NAS-NS-3004.txt

National

 

Academy
of
Sciences

National Research Council

NUCLEAR SCIENCE SERIES

The Radiochemistry
of Thorium

b,
NN

AT
7 Energy =
et LR

 
. COMMITTEE ON CHEMICAL SCIENCES

James. L. Kinsey, Cochairman, Massachusetts Institute of Technology

Alan Schriesheim, Cochairman, Exxon Research and Engineering Company

Andreas Acrivos, Stanford University

AIIen\J_. Bard. University of Texas, Austin

Fred Basolo, Northwesfern University

Steven J. Benkovic, Pennsylvania State Universitf
Bruce J. Berne, Columbia University

R. Stephen Berry, University of Chicago

Alfred E. Brown, Celanese Corporation

Ernest L. Eliel, University of North Carolina

Roald Hoffmann, Cornetl University

Rudolph Pariser, E. . Du Pont de Nemours & Co., Inc.
Norman Sutin, Brookhaven National Laboratory
Barry M. Trost, University of Wisconsin

Edel Wasserman, E. |. du Pont de Nemours & Co., inc.

SUBCOMMITTEE ON NUCLEAR AND RADIOCHEMISTRY

Gregory R. Chaoppin, Chairman, Florida State University

Eugene T. Chulick, Babcock & Wilcox Co.

Christopher Gatrousis, Lawrence Livermore National Laboratory
Peter E. Haustein, Brookhaven National Laboratory

Darleane C. Hoffman, Los Alamos National Laboratory

Paul J. Karol, Carnegie-Mellon University

Michael J. Welch, Washington University School of Medicine
Raymond G. Wymer, Oak Ridge National Laboratory

William H. Zoller, University of Maryland

LIAISON MEMBERS

Fred Basolo, Northwestern University
Theodore L. Cairns, Greenville, Delaware

Gerhart Friedlander, Brookhaven National Laboratory

{(Membership as of January 1982}
The Radiochemistry of Thorium

By E. K. HYDE
Lawrence Radiation Laboraiory
Universily of California

Berkeley, California

January 1960

Reprinted by the Technical Information Center
U. S. Department of Energy

Subcommittee on Radiochemistry
National Academy of Sciences —National Research Council

 
Price $9.75. Available from:

National Technical Information Service
U. S. Department of Commerce
Springfield, Virginia 22161

Printaed in the United Gtates of America

 

USDOE Technical informaton Center, Oak Ridge. Tennessse
1960; latest printing June 1982
FOREWORD

The Subcommlttee on Rediochemistry 1s one of a number of
subcommittees working under the Committee on Nuclear Sclence
within the National Academy of Sciences - National Research
Counclil. Its members represent govermment, Industrial, and
university laboratorles 1n the areass of nuclear chemlstry and
analytical chemistry.

The Subcommlttee has concerned 1tself with those areas of
nuclear scilence which involve the chemlst, such as the collec-
tilon and distribution of radliochemical procedures, the estab-
lismment of specifications for radiochemically pure reagents,
the problems of stockpiling unconteminated materials, the
avaellability of cyclotron time for service irradlations, the
place of radiochemistry in the undergraduate college program,
etec.

This series of momograephse has grown out of the need for
up-to-date compllations of radiochemicel Information and pro-
cedures. The Subcommlttee has endeavored to present a series
which will be of maximm use to the working sclentist and
which contains the lateat available Information. Each mono-
graph collects in one volume the pertinent information required
for rediochemical work with an Indlvidual element or & group of
¢closely related elements.

An expert in the radiochemistry of the particular element
has written the monograph, following a standard format developed
by the Subcommittee. The Atomic Energy Commlssion has sponsored
the printing of the serles.

The Subcommittee 1s confident these publications will be
useful not only to the radiochemist but also to the research
worker 1n other fields such as physics, blochemistry or medlcine
who wishes to use radiochemical techniquee to solve a specific
problem.

W. Wayne Meinke, Chslrman
Subcommittee on Radiochemistry

ill
CONTENTS

I. General Reviews of the Inorganic and Analytical Chemistry of
Thorium '

II. General Reviews of the Radiochemistry of' Thorium
ITI.Table of Isotopes of Thorium
IV. Review of those Features of Thorium. Chemis'try of Chief Interest

to
1.

Radiochemlests
Metalllic thorium
Boluble salts of thorium

Insoluble salts of thorlum and coprecipltation characteristics
of thorium

Complex ions of thorium

Chelate complexes of thorium

Extraction of the TTA-complex of thorium fnto organic solvents
Extraction of thorium into organic solvents

Ion Exchange behavior of thorium

V. Collection of Detalled Radiochemical Procedures for Thorium.

w W

BREE o -
INTRODUCTION

This volume which deals with the radiochemistry of thorium
is one of a series of monographs on radiochemistry of the elements.
There is included a review of the nuclear and chemical features
of particular interest to the radiochemist, a discussion of prob-
lemg of dissolution of a sample and counting techniques, and
finally, a collection of radiochemical procedures for the element
as found in the literature.

The series of monographs will cover all elements for which
radiochemical procedures are pertinent. Plans include revision
of the monograph periodically as new techniques and procedures
warrant. The reader is therefore encouraged to call to the
attention of the author any published or unpublished material
on the radiochemistry of thorium which might be included in a
revised version of the monograph.

vi
The Radiochemistry of Thorium

E. K, HYDE
Lawrence Radlation Laboratory
University of Californie, Berkeley, California
January 1960

Table of Isotopes

I. GENERAL REVIEWS OF THE INORGANIC AND ANALYTICAL CEEMISTRY OF THORTUM

Chapter 3, pp 16-66 in "The Chemistry of the Actinide Elements",
J. J. Katz and G. T. Seaborg, John Wiley and Sons, Inc., New
York, 1957.

Chapter 4, pp 66-102, "The Chemistry of Thorium" by L. I. Katzin
in the "The Attinide Elements", National Nuclear Energy Series,
Division IV, Plutonium Project Record Volume 14A, edited by G. T.
Seaborg and J. J. Ketz, McGrew-Hill Book Co., New York, 195&4.

Gmelin's Handbuch der Anorganischen Chemie, System Nr. 44, 8th
Edition (Verlag Chemie, GmbH. Weinheim-Bergstrasse, 1955).

C. J. Rodden &nd J. C. Warf, pp 160-207 in "Analytical Chemlstry
of the Manhattan Project", McGraw HEill Book Co., New York, 1950.

"Thorium, pp 946-954, Vol. 1 of "Scott's Standard Methods of
Chemical Analysis", K. H. Furman, editor, D. Van Noetrand Co.,
Inc., New York, 1939.

"The Analytical Aspects of Thorium Chemistry", T. Mueller, G.K.
Schweltzer and D. D. Starr, Chem. Rev. 42, Feb. 1948.

Collected Papers on Methods of Analysis for Uranium and Thorlum
compiled by F. 8. CGrimaldl, I. May, M. H. Fletcher and J.
Titcomb. Geological Survey Bulletin 1006, 1954, for sale by
Superintendent of Documents U. 8. Govermment Printing Office
Washington 25, D. C. Price ¢ 1. -

II. GENERAL REVIEWSOF THE RADIOCHEMISTRY OF THORIUM
Chapter 15, "Radiochemical Separations of the Actinide Elements",

by E. K. Hyde in "The Actinide Elements", edited by G. T. Seaborg
end J. J. Katz, McGraw Hill Book Co., New York, 195L.
Paper P/728, "Radliochemical Separations Methods for the Actinide
Elements" by E. K. Hyde, pp. 281-303, Vol 7, Proceedings of the
International Conference in Geneve, August 1955 on the Peaceful Uses
of Atamic Energy, United Nations, New York, 1956. Single copies of
this paper may be available for 25 cents from United Natlons Book-
stare, New York City.

IIT. TAHLE OF ISOTOPES OF THORIUM

 

 

 

Isotope Half 1life Type of Method of Preparation
Decay
rn2e3 ~0.1 sec o Demghter 1.3 min UPZ!
Thzah ~1l Bec a Daughter 9.3 min 0228 '
The22 8 mn a ~90% Daughter 58 min y229
EC ~10%
Tn?26 30.9 min a Daughter 20.8 day UZ0°
ThE2l 18.17 dsy a Netural redicactivity; dsughter AcZZ!
(RdAc) -
T'J:L228 1.91 year a Netural radiocactivity; dsughter MZZB
(RATh) (MsTh,, )
229 7340 year o Daughter U233
Th23° 80,000 year a Natural radicactivity; daughter Uz3h
(Ionium)
%’hZ?l 25.64 hour B Natural radiosctivity; dsughter U237
UY
™?32 1,39 x 10¥%ear < Natural thorium 1s 100% Th232
233 22.1 min B- ThZ32 4+ neutrons
:(uh23;' 24.1 day B- Natural radlosctivity; dmughter U230
Uxy

 

For more complete information on the radiations of the thorium isotopes
and for references to original literature, see "Table of Isotopes”, D. Strom-
inger, J. M. Hollander and G. T. Besborg, Reviews of Modern Physics, 30,
No.2, Part II, April 1958. |
IV. REVIEW OF THOSE FEATURES OF THORTUM CHEMISTRY OF CHIEF
IRTEREST TO RADIOCHEMIOSTS

1l. Metgllic Thorium

Thorium metal is highly electropositive and its preparation is a matter
of no mean difficulty. Methods which are used for this purpose include re-
ductlon of thorlum oxide with calclum, reduction of thorium tetrachloride or
tetrafluoride or tetrachloride by calcium, megnesium or sodium or electrolysis
of fused salts. Thorium metal has a high melting point (1750° C) and is
highly reactive in the molten state. The potential of the thorium-thorium (IV)
couple has been egtimated as + 1.90 volts.l A fresh surface of thorium tar-
nishes rapidly in alr and the finely divided metal 18 pyrophoric. The pres-
ence of oxygen and poselbly of nitrogen and other light element impurities
on the surface of thorium can be a matter of some importance in some experi-
ments in nuclear chemlstry or physics where thin foils of thorium are employed
a8 targets.

The reaction of thorlum metal with agueous mineral acids has some featbures
of grea-t Interest to radiochemists. Dilute.hydrofluoric aclid, nitric mecid,
sulfuric acid end concentrated phosphoric acld or perchloric ecld attack mas-
slve thorium metal slowly. Concentrated nitric acid rendere thorium passive
but the additlon of fluoride ion ceuses the dissolutlon to contimue. In the
dissolution of small thorium targets, 1t is found that concentrated HRO3 con-
talning 0.0l molar (N]Ih)z SiF, (or HF) mekes a good solvent mixture. The sol-
vent should be mdded in batches with heatlng and stirring in between rather
than all at once. Hydrochloric acld attacks thorium vigorously but a mysteri-
ous black or blue-black residue remains on completion of the reaction. As
mick as 25 percent of the original metal may be comverted to the black solid
by either dilute or concentrated hydrochloric acid. Most or all of this resl-
due can be dlesclved by adding fluoride lon 1n small concentration to the

hydrochloric acid. The blaeck réesidue may be ThO or it may be a hydride Thgz
For a further discussion of this material see Katzin , James and Stresumanis-,
and Katz and Bea:borgh. | |

Thorium oxide targets csn also be dissolved by a mixture of hydrochloric
acid plus (Nflh)z BiF¢ or of mitric acid plus (Hflh)zflfli‘G. A good discussion of
the fluoride ion catalyzed dissolution of thorium metal or thorium dioxlde is

given by Schuler, Steahly and Stoughton.'®

2. 8oluble Salts of Thorium
Since thorium exists in solution as a comparatively small highly charged
cation, it undergoes extensive interaction with water and with many anions.
There 1s one great simplification in the agueous chemlstry of thorium in that it
hes only one oxidatlon state and hence oxidaetion-reduction reactions do not
need to be considered.

The water soluble salts of thorium include the nitrate, the sulphate, the
chloride and the perchlorate.

3. Ingoluble Balts of ThoriuméPrécipitation and Coprecipitation Character-
isties of thorium

The common Iinsoluble compounds of thorium are listed in Table 1. An
inspection of the table suggests a number of precipitates which may e sultable
for the removal of tracer amounts of thorium from solutlon. Good descriptlons
of the insoluble compounds of thorium and their use in analysis are glven in the
general references listed 1n Part I.

Thorium hydroxide is a highly insoluble compound forming s gelatinous pre-
cipitate when alkal! or ammonium hydroxide 1s added to an aguéous solutlon of
Th*h. It 15 not amphoteric. Thorlum hydroxide dissolves In aquecus solutlions
contalning ions such as clitrate, carbonate, or sulfosallcylic acid which
complex thorium lon. Tracer amounts of thorium will coprecipitate quantitetive-
ly with a wide variety of lnsoluble hydroxides; lanthammm, ferric snd zircon-

TABLE 1 IRSOLUBLE COMPOUNDS OF THORIUM

 

 

Reagent Precipitate Solubllity in Solubility in
Water other Reagente
OH ‘Th(OH), very insolgBle soluble in acids,
S.P. = 10~ ammonium oxalate,

alkall carbonates,
sodium cltrate, etc.

F ThF), - hnéo very insoluble soluble 1in acld
aluminum nitrate
solution

Kr + HF KzThFG very lnscluble

Io3' Th(103)4 very insoluble

(even in strong EN03) soluble with reagents
whlch destroy 103
C,0,= Th(Czoh)EGHEO ingoluble in water soluble in excess
or 1ln dilute acid ammonium or potasslium
oxalate

PO, = Th3(P04)h very insoluble diesalves with

difflculty in
Th(HPOh)zHéo concentrated acid
(PO, ) 5, PO; 22,0
BP0~ ThP_0, - 2H_0 extremely insoluble
276 :
276 Hz 1.65x10=*% moles per
liter 4.ON HC1

H;0, + Th(00)230£3320 very insoluble soluble in strong

0.1X stoh mineral ecild

 
TARIE 1 (Cont'd.)

 

 

Reagent Precipitate Solubility in Solubility in
. Water . other Reagents
503= Th(SO3)2H20 partially dissolved in
excesa sulphite
Cr207= Th(Cro,, ), * 38,0 insoluble 1n'320 . soluble in conc,acid

Th(0H) ,Cr0, *E,0

MoQ, = Th(moh)zlmzo ' insoluble soluble in dilute
mineral acids

Fe(CH) gh ThFe(CN) 6-hELzO very insoluble

 

ium hydroxide bhave been used. Since hydroxide carrier precipitates are notori-
ously non-specific, they should be counted on only to remove thorium from e
simple mixture of contaminants or as a group separation to be followed by more
specific chemlcal purificatlon steps. In some of the classical studies of the
uranium series’ le(Th23h') wag separated from uranium by precipitating ferric
hydroxide and ammonium uranate together and leaching the uranium from the pre-
cipitate with ammonium carbonate.

Thorium peroxide forms when hydrogen peroxide is added to a dilute miner-
al acid containing thorium. It is highly insocluble. The formula ip often
glven &s Th,on but recent investigations suggest that anions are incorporated
into the solld as integral components. The preclse formula of the precipitate
varies with the condltions of precipitation. The physical form 1s aleo greatly
different depending on the acidifiysa: when preclpitated from a neutral solu-
tlon it 1s gelatinous and contains many copreclipltated anions; when preclipi‘ba'bed
from a slightly baslc solution, it i1s not so gelatlnous and has & lower perox-
ide content; when formed in an acid solution, 1t is opaque and readily filtered.
Insoluble peroxide compounds are rare in the Periodic Syst. 8o that preclplta-
tion of thorium peroxlde can provide clean separatlion of thorlum from most other
elements. Plutonium (IV) forme & peroxide similar to tbat of thorium (IV). Other
(IV) state elements such es cerium (IV) and zirconium (IV) aleo form such in-
soluble peroxides. Urenium (IV) and neptunium (IV) also form insoluble precipi-
tates upon the addition of peroxide, but these seem to be of a somewhat differ-
ent type than those formed by thorium and plutonium. These peroxide precipl-
tates are reedily dissolved by the addition of reagents such as Sn(II), I,

MRop or Ce(IV) which can destroy peroxide. For a more complete discussion of
the peroxide and for references to the original literature, see Katz and Sea-
borgs.

Lanthamm Fluoride as Carrier for Thorium. Thorium will coprecipitate
quantitatively with lanthamm precipitated as the fluoride from strongly acidiec
solutions. This is e very useful method for the aeparation of small smounts of

p
thorium from uranium sclutions. The fluoride may be converted to the hydroxide
by direct metathesie with mlkall hydroxdde pellete or strong alkall solutions,
or it may be dissolved in an alumimum nitrate-nitric acid solution (which
thoroughly complexes the fluoride ion) and then be precipitated as the hydroxide,
The coprecipltation of rare esrth impurities 1is, of course, complete. Zircon-
l1um and barium in trace concentrations are carried but, i1f milligrem quantities
of these elements are added as "hold-back carriers”, no coprecipitation is ob-
served. Hence coprecipitation with lanthamum fluoride serves as an excellent
method of freeing thorium from the zirconlum carrier used lIn a previous step.

An slternate method would be the removal of zirconlum on an anlon exchange
regin from an 8-10 molar solution of hydrochloric acid.

Other lnsoluble fluorlides may serve as carriers for trace amounts of thor-
ium.

Zirconium Todate as Qarrier. Zirconium in a cohcentration of 0.1 to 1.0
'mg/ml may be precipitated as the iodete from a strongly acidic solution to
carry thorium nearly quantitatively. The iodate concentration is not critical.
Elements which form insoluble lodates are also coprecipitated, but many, such
as uranium, are separated. The rare earths and actinium are decontamlnated if
the preclpitation i1s from a strongly scidic solution and the preclpitate is
washed with an lodate contalning selution. Under conditions of low acldity
and low total ionic strength, the carrylng of these elements may be gulte high,
as shown for actinium by McLane and PetérsonT. If cerium is present 1t 1s
necessary to reduce Ce(IV) to Ce(III) with eome sulteble reducing egent such as
hydrogen peroxide, before precipitation.

The zirconium lodate may be dissolved in nitrilc acid containing sulfur
dioxide or some other reducing agent, and the zirconium may be repreclpitated
as the hydroxide after the solution 1s boliled to remove ilodine.

Hegemann and his co-m:rkerea8 applied this method to thelr study of the
isotope T]:x229 in the 4n + 1 series. Their procedure is reproduced in Proced-
ure 16 of Section V below. Ba.lloru9 used 1t as a means of substituting zircon-
lum carrler for rare lea.rth carrier after an 1nitial leanthanum fluoride precipl-
tation. See Procedure 13 in Section V below.

Phoephate Precipitates. Thorium precipitates in a varlety of ill-definped
forms in the présence of phosphorous-containing enions. These compounds are
extremely insoluble in.water and in acid solutlion. The hypophosphate is parti-
cularly insoluble. Even in @i Hecl the solubility is only 2.1 x lf)ll' moles per
liter. Other insoluble phosphates such as zirconium phoephate serve as good

 

carriers for the removal of trace amounts of thorium from-agueous esolution.
Thorium Oxalate. A widely used method of quantitatlive analysis of thorium
is the precipitation of thorium oxalate followed by ignition to thorium dioxide

and weighing of the dioxlde..°
Some camplexing agents lnterfere with the precipitetion of thorium oxalate
by the formation of soluble thorium complexes. Gordon and Shaver report a& meth-
od for the separation of rare earth ions from thorium by precipitation of- phos-
phate-free rare earth oxalates l1n the presence of the strong chela.ting a.gent,
ethylenediaminetetraacetic acid (EDTA). _

"Organic Aacids which form water-insoluble compounds with thorium vhich are
of possible analytical or radiochemical importance Include sebacic, a.nthranitic,
phenylarsonic, galllic, tennlc, quinaldic and aspartic acids.

4. Complex Tons of Thorium -

The highly-charged pceitive lon, Th+‘h, has & strong tendency to form com=-
plex ions with enions which may be present in solution. Some familiarity with
the more common of these complex ions is required for a proper u.nderstanding of
tbe behavior of thorium lm ion exchange sepa.ra.tions, in the extraction of thori-
um into organic solvents and so on., Quantitatlive measurements which have been
made on the equilibrium constants for complex ion formations are summarized in

Table 2.

TABLE 2 COMPLEX IORS OF THORIUM
(Reprinted from Katz and Sesborg p.57, reference 5)

 

 

Complexing Reaction - Ionic K I Ref'-
Agent 8trength _ erences

c1L” 01" = e *3 ' 0.5 2.2h a

0.7 1.78 a

1.0 1.53 a

2.0 1.21 e

4.0 1.70 a

6.0 2.1 a

mn*te2cT = Thcféz 2.0 0.1 a

Yo - 0.1k a

6.0 0.55 a

301" = Tao1tt 2.0 0.2 . a -

4.0 0.10 a

6.0 0.35 a

e = ThCL,, : k.0  0.018 a

N05 Th*"‘mo; = Th(NO3)+3 0.5 L.73 b

: ' 2.97 2.83
Th+h+2£0§ = Th(NO3);2 5.97 1.4 c
c10; '1'h+4+01o; - 'I‘h(ClO3)+3 ~ 0.5 1.84 b
TABLE 2 (Cont'd.)

 

 

Complexing Reaction Tonic K Ref
Agent ' Strength erences
Bro; Th+h+Br05 = Th(Br03)+3 0.5 6.4 b
‘I‘h+h'+2:Br05 - Th(BrOB)'éz 0.5 8.2 b
C1CE,COOH Th+h+ClCHZCOOH = Th(C1CH,C00 R 0.5 1.33 b
C1,CHCOCH Th+h+CIZCBJOOH = Th(Clzcacoo)+3+H+ 0.5 5.7h b
Th“‘+2012011c003 = Th(Clchcoo);2+zn* 0.5 12.7 b
C1.,CCO0H Th+h+013CC00H = Th(0130000)+3+]1+ 0.5 8.23 b
Th*l-tec13ccoon = Tl:\(c13ccoo)'2’2+13H+ 0.5  26.7 b
1'0_;’ Th*l‘qo; = Th( 103)+3 0.5 "{.6x_'|.0i b
Th+l++2105 = Th(IO3)£2 0.5 6.2x10
Th+h'+310; = Th( :ro3)3JL 0.5 1.4x107
- +i - ++ -+
EOM_ Th +E0h‘ = ThSOh +H 2.0 159 .C
Th*'!f-zmo; = Th(80,, ) +2E" 2.0 2850 c
'1'?:1*"‘“+215|.°..o,:L = Th(rsohsoh)‘” +E" 2.0 800 c
HaPoh_ Th#'t+H3PO,+ = Th(H3POL)+J+ 2.0 T8 ¢
Th+h+H3P01|_ = -1'1:1(15[2?01‘)"34[+ 2.0 150 c
Th+4+ZH3POh_ = Th(HzP°hH£°1+)+3+H+ 2.0 1400 c
Th*‘l‘+zna1=oh = Th(H,P0, )5 +2H" 2.0 8000 c
EF Tt EF = ThETO4E 0.5 sx10° o
T4 2HF - ThF§2+ZH+ 0.5 2.9,‘10; e
e 3EF = ThF3+3H+ 0.5 9.4x10 d
CH,COCH, COCH, Tht*+EAcAc = Th(ache)t+E" 0.0l 3. 7107 e
Tt +2BAcAc = Th(AcAc)*Zr2E" 0.0L  7.3kx10%?
T, 3pAcAe = Th(AcAc) +3H" 0.0L  5.93x10%°
Th“AEAcAc = -Th(AcAc)ll_+1+3+ 0.01 5.3Tx1025

 

a. W.C. Waggener and R.W. Stoughton, J. Phys. Chem

. 56, 1-5 (1952).
b. R.A. Dey Jr. and R.W. Stoughton, J. Am. Chem. Soc. T2, 5662-66 (1950).

c. E.L. Zebroskl, H.W. Alter, and F.K. Heumann, J. Amer. Chem. Soc. T3,
5646-50(1951) -

d. H.W. Dodgen and G.K. Rollefson, J. Am. Chem. Soc. 71, 2600-7 (1949).

e. J. Rydberg, Acta Chem. Scand. 4, 1503-22 (1950); Arkiv for Keml 5,
413-23 (1953). -
A large number of other complex ions are known although not much quantita-
tive information 1s avallable on the strength of the complexes. Ions derived
from meny organic acids such es cltrate, phthalate, maleate, succinate, malo-
nete lon and ethylenediaminetetrascetic (called EDTA or versene) form a series
of complex compounds or lons with thorium, The soluble EDTA-Complex of thorium .
forms the basis of an excellent tdtrimetric determination of small amounts of
thoriumll’lz. It 18 of great significance to radlochemistry that thorium forms
a negatively-charged nitrate complex in nitriec acid solutions greater than 3
molar in concentration. This is discussed further in connection with anion
exchange methods.

In connectlon with complex ion formation we may mention briefly the hydroly-
sis of thorium ion. In acidlic solution throughout the entire range below pH3
hydrolysis of Th+1|. is negligible. At higher pH values there is extensive hydroly-
8le. There is a consldersble disagreement in the published literature on the |
products of hydrolysis end a number of mononucdlear and polynuclear complexes
have been postulated. For interesting experimental studies and theoretical in-
terpretation of the hydrolysls of 'I'h+h see Krans and Holmbergl3 and Ei]_'l.énlh’ 15.

5. Chelste Compounds of Thorium

A few 1,3 diketones form chelate complexes of thorium which are readily ex-
tractable from agqueous solution into organic solvente. This fact forms the ba-
gls of a wildely used method for the radiochemical purification of tracer thor-
ium, namely the extraction into benzene of the thenoyltrifluorcacetore acid com-
plex of thorium which 1s discussed in section 6. Before discussing this speci-
fic eystem, it will be worthwhile to review briefly the other known complexes
of this type which thorlium forms.

The very strong and rather volatile complex of thorium.with ecetylacetone
has been knwon for many yea.rs.ls In a 1,3 diketone complex of this type, four
molecules of the organic compound react with the Th'm ion to form a neutral
complex. Thorium acetylacetonate, like the other metal acetylacetonates,
poeges a cyclie structure with the metal incorporated as part of a six-membered
ring. Rydberng has made a particuarly careful study on the complex formatlon
between thorium end acetylacetone and of the extraction of the complex 1lnto
organic solvents. Other 1,3 diketones which form similar complex compounds mich
more stable toward acidlc solutions are trifluoroacetylacetone, thenoyltrifluoro-

-2
acetylacetone, benzoylacetone and dibenzoyl 11149.'t.]:ua.1:LelB 0._ A comprehensive 1n-

2
vestigation of thorium chelate complexes was carrled out by Dyrssen 1. Some of

his remults are quoted i1n Teble 3 where the complexing constants of the proton
and thorium complexes of several chelating agente are given.
Thorium forms complex compounds with salicylic acid, methoxybenzolic acid

and cinnamie acidzz. The thorium-salicylate complex extracted lnto methyl
isobutyl ketone has salicyclic aclid assoclated with 1t and mmy have the formila
Th(HA)h-HzA. Cowan®2® developed a procedure for thorium analysis based on the
extraction of the thorium salicylate complex into a mixed solvent of chloroform
" and ethyl acetate. ‘ |
Cupferron (nitrosophenylhydroxylamine) forms & complex which can be ex-
tracted into cholorform. Thorium forms a complex with quinolinol which is sol-
uble in orgaenic solvents.23 The thorlum complex wilth the reagent, thorin, 1s

widely used in a colorimetric analytical method.23a’23b

TABLE 3 THORIUM COMPLEXES OF SOME CHELATING AGENTS. (Dr:rflsenZJ)

 

 

Chelating Agent: DKa 1/4 log X
(note 1)
Acetyl acetone 8.82 -2.85
Thenoyltrifluoroacetone 6.23 . +0.0k4
1-nitroso-2-naphthol T.63 -0.41
2-nitroso-l-naphthol 7.24 +0.05
Tropolone 6.71 +0.52
Cupferron 4.16 +1.11
N-phenylbenzohydroxamic acild 8.15 -0.17
8 Hydroxy quinoline (oxine) 9.66 -1.78
5 Methyl oxine 9.93 -2.5
5 Acetyl oxine T-75 -1.0
5,7 Dichloro oxine T4 =0.22
Cinpamic acld 4,27

 

notel K= [MAnJ orgfif]n [M]n[HA]grg , where MAn = uncharged complex;
[BA]= ec1d form 6f the chelating agent.

6. Extraction of the TTA-Complex of Thorium into Organic Solvents

Many of the chelate complexes mentioned in the last section of this report
are soluble in organic solvents. By sultable adjustment of reagent concentre~
tions and acldity, thorium cen be cleanly separated from conteminating ione by
such an extraction procedure, We single out for special attention the complex
formed with a-thenoyltrifluoroacetone, (called for convenience, TTA), which
has been more widely used in rediochemlistry then any of the others. Some of the
reasons for this are the gtabllity of the reagent toward acidic solution, the
favorable Keto-enol equilibrium in the remgent, the strength of the thorlum com-
plex in slightly acldic solutions and the moderate solubllity of the complex in
such solvents as benzene, chloroform and ketones.

Hagemannah studied the zcld dependence of the extraction of trace quantities
of thorium, ectinium and other elememts into an 0.2M solution of TTA in benzeme.
A typlcal curve 1s shown in figure 1. The extraction of thorium is essentially
quantitative ebove pHland drops rapldly in solutions of higher acidity. The
acld dependence is fourth power so that rather sensitive control of the extrac-
tiofi can be made by control of the acldity. This control 1s highly useful since
thorium mey easily be separasted from elements of lower lonic charge such es the
alkall elements, the alkgline earths and even the rare earth elements by extrac-
tion of thorium 1n the pH range of 1 to 2. Elements which extract more readlly
than thorium are left in the benzene phase when the thorium is later removed by
contact with an agueous solution. of sl ightly lower pH. The chief lomns which are
extracted more strongly than thorium Iin solutions of acidity greaster than pHL
are zirconium (IV), hafnium (IV), plutonium (IV), neptunium(IV), iron III, and
protactinium (V). These ions show high partition coefficients into the organic
phese for solutions as strongly acidic as 1 molar or greater.

Further control of thorium extvrectlon can be achieved by chenging the con-
centration of TTA or by using another solvent In place of benzene. The presence
of ions which form strong complexes with thorium (see Table 2) interferes with
the extraction of thorium; therefore, it is best to perform the extraction from

 

 

 

S
— 100F
2 i Th(lV) Ac (I11)
o 80
|—
xX 60 '
w MU-9899
- 40+
w 20F
(&
ES I i 1 ! i 1
a i 2 3 4 5 6 7 8
pH
Figure 1 Extraction of trace amounts of actinium end thorium

from a dilute nitric acid solution by an equal volume of an 0.25 M
gdolution of TTA in benzene as a function of pH.

a8 dilute nitric acld, perchloric acid or hydrochloric acid solution. Most of
the complex ion formation constants listed in Table 2 were measured by noting
the changes in the extractability of the thorium-TTA complex into benzeme when
various anions were added. to the agquecus phase. Hence the references quoted in
Teble 2 can be consulted for very specific information on the extraction of thori-
um in the presence of complexing anions.

TTA extraction of thorlum is an important step in several of the procedures
written down in SBection V below.
Thorium may be separsted from uranium when both are present in small con-
centrations 1if the solution co.nfa.ins no great quantity of neutral salts, but
the acldity mist be edjusted carefully, There are better methods for meking
this particular separation. The extraction of tracer thorium from concentrated
golutions of uranium is not satisfactory beceause of the formation of insoluble
uranium complex compounds at the interfece and it is necessary to remove the
bulk of the urmalum by some prelimlinary step.

In the isolation of small emountes of thorium from a complx initial mixture
of elements TTA extraction provides an excellent final step. Carrier precipitates
such as lanthanum fluoride and zirconium lodate may be used to remove the bulk
of the impurities and the finel purificaetion as well as the elimlnation of the
carrier material, may be effected by a final TTA-extraction cycle.

The solubility of the thorium-TTA complex In benzene 18 rather small so
that large volumes of solutlon are required to handle bulk amounts (gram amounts)
of thorium. Some .wor]a:ersz5 report good results with the reagent, 1-(3,4 dichloro-
phenyl) - &,k4,5,5,6,6,6 heptafluoro-1,3 hexanldione which forme a thorium complex
with a coneldersbly higher solubility in benzene. Unfortunately, this reagent
is not avallsble commercially. With this ‘reagent 20 grems of thorium can be dis-
solved 1n 100 millileters of Cfllh_ compared to 0.3 grems of thorium as the TTA-
complex.

T. Extraction of Thorium Into Organic Solvents o

The extrzctability of thorium from esgqueous solutlions irto organic solventa
has been studled for dozens of representative solvents of all types. Most aof
these studies have been concerned with hydrochloric acid systems, nitric acid
syetems or mixed nitric acid - neutral nitrate salt systems. A great deal of
the information on the extraction of thorium, urenium and plutonium was origj.-
nally published in dlessified repfirts of the Manhattan Project or of the Atcmic
Bnergy Commission or of the governmental lsboratories of Canada and Great Britain
and France. This information is now declassifled, but there has never been a
complete systematic covermge of the basic chemistry in bocks &nd Journals readi-
ly avallable in any sclentific laboratory. Solvent extractlon processes have
been developed for the recovery of thorium from monazite sands, for the separa-
tlon of U°33 from neutron irradiated thorfum, for the recovery of the irraiisted
thorium for reuse, and for othefi:- .purpoaes. In this brief review, we conflne
our rema.rks to the chief solvents and the pflnc:l.pa.l effects of experimental
conditions of the laboratory scale treatment of small or tracer quaht:l.ties of
thorium,

Ethyl ether ig often used to purify uranium. If the agueous phase ia
slightly acidic with nitric acld (perhaps .0l to .05 Molar) and highly selted
with a neutral nitrate such as amnnium, cdlclum or megnesium fiitrate, then

12
uranium ieg reedlly extracted into ethyl ether leaving nearly all lmpurities in-
cluding thorium in the aquecus phase. Thorium will not extract into ethyl ether
unless the concentration of acid ard neutral salts in the aqueous phase is so
high that numerous other Impurites would also extract.

Methyl iscbutyl ketone wlll extract thorium with a distribution coeffi-
clent ae high as 9 (organic/aq_ueoua) provided the nitric acld concentration
of the agueous phase 1s malntgined at 1M to 3M and if, in addition, a high
concentration of such strong salting egents as calelum, magnesium or aluminum
nitrate 1s maintelned. At the Towa State College in Ames Iowa, large quantities
of thorium were purified from monazlte sands by a process which included a sol-
vent extraction separation of thorium fram rare eexrth impurities 26. The so0l-
vent was hexone and the aquecus phase feed solution was 3 Molar in calcilum ni-
trate and 3 Molgr in nitric acid, _

Rydberg and Bernstrim’| have studied the distribution of Th(IV), U(VI),
Pu(IV), PU(VI), Zr(IV), Ca(II}, La(III) and mwo3 between methyl isobutyl ketone
and agueocus solutions of nltric acid and calcium nitrate of varying composition.
Figure 2 teken from thelr work shows the maln feamtures of the extractlon of
theee 1lons. A 1955 Geneva Conference peper of BrucezTa discusees the extractlion
of flssion products into hexone.

Pentaether (dlbutoxytetraethylene glycol) will extract thorium from
equeous nitrate soclutions under moderate salting conditionasz. For example,

3 and 1M or greater in calclum
nltrate are removed to the extent of 90 percent or more from the agqueous phase
by an equal volume of this solvent. Fifty percent is removed from s IM B.ND3
solution and 80 percent from an BM BNJ3 solution by an equal volume of solvent.
If the agueous phese ig 1M in H'.NO3 arzag saturated with emmonium nitrate, the
extraction 1s quantitative. Pappard ~ hes reported the use of pentaether 1n
the purification of lbnium (Th230) from pltchblende resldues. He states that

90 percent of the thorium is extracted from a solution &M in “Eum3 and 0.3 M
in HFO_ into an equal volume of solvent consisting of a mixture of pentaether

(2 volumes) and diethylether (1 volume). Under these conditipne less than 1
percent of yttrium snd the rare earths are extracted.See alpo analytical method
of nefigseffgfi oxtde [ (CB,), C = CH-CO-CH3] has been reported to be & useful sol-
vent for thorlum. Levine and Grima.ldizg have used 1t in an analytical procedure

tracer amounts of thorium in a solutlon Zy_ in HRNO

for the determination of thorium in thorium ores. The ore sample is decomposed
by fusion wilth a mixture of NaF 'KZSZO'T' Thorium is precipltated as the oxalate.
The oxalate preclpitate 1s dissolved 1n nitric eclid end the solution 1s pre-
pared for solvent extrection by edjusting the ZE[BOB concentration to 1.2 Molar
and edding eluminum nitrate to 2.5 Molar, The solution is contacted with an
equal volume of mesityl oxlde which extracts the thorium quantitatively and

separates it from nearly all impurities including rare earths. Traces of

13
 

 

-
=
L
o
L
Lo MU - 16989

LJ
o
o
<
o
=
=
<
o

K o= 000"

1 1 ] |

4 5 6

| M HNO,
Figure 2 Solvent extrection data for methyl isobutyl ketone.

The distribution ratios of U, Pu, Th, Zr, La and Ca as functions

of the equllibrium concentration of HN03 in the mqueous phase,

Concentration of Ca(NO is 3.5 to 4.0 Molar. Data by -Ry'd'berg
w27

and Bernatrom.

3)2

rare earths are removed from the solvent by three separate washes with e wash
solution containing HNO &nd Al(ND ) . The thorium is stripped from the washed
- solvent with weter. Thorium is precipita'ted as the oxalate and ignited to
Tth, in which form 1t 1s weighed,

Hiller and Mertin3® have used mesityl oxlde to extract thorium eway from
rare earth fission products in a thorium target solution. The thorium metal
was dissolved in HC1 with a small amount of fluosilicate lon present to clear
up the solution. The solution was seturated with A1(®O )3 and the thorium was
extra.cted. by contecting the solution with mesityl o:d.d.e.

Marechal-Cornil and Picciotto3 used mesityl oxide for the quantitative
.ex't.ra.ction of thorium, bismth and polonium from a mixture of natural radlo-
elements present in concentrations 10_9 grams per c¢.c, The solution was sat-
urated with Al(N03)3. Redium and lead did not extract.

Tributyl Phosphate (THP) 1e a wldely used solvent in the industrial scale
recovery of uranium and thorium from ores, or the purification of urenium, thor-
ium or plutonium from reactor fuel elements. Some idea of the scope of 1ts use

4
32-34

can be obteined by consulting some general references on process chemistry.

The mdjustment of egqueous phase composition for the optimum radiochemlcal
purification of thorium depends greatly on the nature of the impurities present.
The principal heavy elements or fission products which show high extractability
into TBP are the following:

thorium (IV) < £¢ptunium (I¥) < plutonium (IV)
plutonium (VI) < neptunium (VI) < uranium {VI)
protactinium (V)

cerium (IV) hafnium (IV) zirconium {IV)

rare earths (ITI) (considersbly less extracteble than
above under most cond:l.'l:.ions).

RuNo (III)

TABLE 4 BASIC REPERXNCES ON THE EXTRAOTIOF OF THORIUM, OTHER HEAVY ELEMENTS
AND THE RARE BARTHS INTO TBP

 

Tri-n-butyl Phosphate as an Extracting Bolvent for Inorganic Nitrates,

I. Zirconium nitrate
35. K. Alcock, F. C. Bedford, W. H. Hardwlick and H.A.C. McKay,
J. Inorganic and Nuclear Chem. L4, 100, 1957.

II. Yttrium and the lower lanthanide nitrates
36. D. Bcargill, K. Alcock, J. M. Fletcher, E. Hesford, and H.A.C.
McKey. J. Inorg. Fucl. Chem. L4, 304, 1957

ITT. The plutonium nitrates _
37. G. F. Best, H.A.C. McKay and P.R. Woodgate, J. Inorg., Rucl.
Chem., k%, 315, 1957

IV. Thorium nitrate
38. E. Hesford, H.A.C. McKay and D. Scargill, J. Inorg. and Fucl.
Chem. 4, 321, 1957

 

An excellent overall view of the extraction of these elements from hydro-
chloric or nitric acid systems of varylng composition into an undiluted or
diluted THP solvent phase is presented in the articles listed in Table L.

The high extractabillty of thorium into undiluted TBP from hydrochloric
acid and nitric acld systems are given in figures 3 and 4. Thorium nitrate 1s
mich more extractable when most of the nitrie acid in the esgueous phase 18 re-
placed by some nitrate salt such as sodium nitrate, caleium nitrate or alumlmum
nitraete. Thls 1s drematically shown 1n Taeble 5 where some date taken from a
publicetion of H.A.C. MKay are presented. The maln reason for the difference
1s that the neutral nitrate salts are not soluble in TBP whereas BNQ3 forma a
seoluble complex with TBP.
Bernstrom and Rydberghl have studied the effect of the replacement of HN03
with calcium nitrate on the extraction of thorium by undiluted tributyl phosphute.
An approximate summary of thelr results 1s glven in Table 6. Some of the impor-

 

0.}

0.01

 

0.001

 

 

1 1 1 1
20 4.0 6.0 8.0 10.0 120
M OF HCI

 

1
0.0001
o

. Figure 3 Variation of distribution ratios (TBP/agueous) of
gcandium, thorium and zirconlum with aqueous HC1l concentratlon

for extraction into pure, undiluted TBP. Peppard, Mason and Maierhz.

tant separations which can be made with such a mixture of "salting agents" in the
- aguecus phase are apparefit from an ipspection of figure 5.

The viscosity and denslty of undiluted TBP mekes 1t somewhat troublesome to
use, Hence 1t 1s frequefitly diluted to a 10 to 40 volume percent solution in
some inert diluent solvent such as n-butyl ether, ether, benzene, carbon tetra-
chloride, kercsene or some industrial mixture of hydrocerbons., The diluted THP
extracts thorium with & reduced extraction coefficlent but, as a cqmpensatory
change, the ektractability of a number of other ions 1s reduced below the point
where they will extract to an apprecisble extent,

Thorium may be recovered from a TBP phase into an aguecus phese by back-
washing the TBP with dlstlilled water or with very dilute acid.

16
 

100

 

 

 

 

K 10
1.0
0.1
Q 2 4 6 8 i0 12 14 16
M OF HNQ3
Figure L Variation of distribution ratice (TBP/aqueous) of

scandium, thorium and zirconium with aqueous HNOa concentration

for extraction into pure undiluted TBP. Peppard, Mason and Maierhz.

17
 

 

 

—
<
wJ
o
L
L
Ll
o
&
=2 10
o
=
T L HNOs
<t
a La (1)
107
Cu(ll)
r(l1)
I 0 1 L |
| 2 3 4q 5 6
M HNO,
MU - 16988
Figure 5 The partition coefficlents (org/eq) of Th(IV) and

of several representative contaminating lons lnto undiluted TEP

es a function of END3 in the agueous phese. The agqueous phase
concentration of Ca(R03)2 ls fixed et 3 Mclar. The curves for
Pu(VI) and Pu(IV) have been extrapolated assumlng Pu(VI) parallels
U(VI) end Pu(IV) perallels Th(IV). From Bernstrbm and Rydberg r.
TABLE 5 EFFECT OF NEUTRAL SODIUM NITRATE ON THE
EXTRACTION OF THORIUM FRQM HNO; SOLUTION WITH 19% THP

 

 

Aqueous Composition '_ K (org/aq.)
ENO3 Na.N03

2.0 0 0.8k

0.01 1.99 k.o

6.0 0 3.2

1.0 5.0 33

0.1 5.9 200

 

Abstracted from data of H. A. C. McKay presented 1n
Process Chemistry, Progress in Nuclear Energr, Pergamon
Prese Ltd. London 1956.

Thorium concentration about 1 gram per liter.

TABLE 6 EFFECT OF CONCENTRATION COF Ca(RO,)
AQUEOUS PHASE ON THE EXTRACTION OF Sxro
UNDILUTED TBP. (Bernstrim and Rydberghl)

 

 

Ca(No,), HNO, K, (TBP/Aq)
Conc Conc

0 1-k M 4-20

1M 1-% M 60-200

2 M 1-4 M 310-550
3M 1-4 M 1400

 

19
Important Note: All of the data quoted here for extractlon of thorium by
tributyll phosphate are for e pure solvent pretreated to remove monobutylphos-
phate and dibutyl phosphate. Most THP "as received" is contaminated with these
hydrolysie products. Since these compounds have a much stronger sbility to com-
plex thorium and contaminating impurities, quite different extraction and purifi-
cation behavior is obtalned when they are presnt. Hence 1t is good practice to
pretreat TBP by washing it thoroughly with aqueous sodium carbonate and pure
water. |

Monoalkyl and Dialkyl Phosphates mixed with inert carrier solvents show
phenomenally high extraction coefficients for thorium even from aquecus solution
in which the concentration of acid and neutral salts is quite low. The general
equations for such solvents are

(GO)PO(OH)Z

and (G0),PO(0H)
Some specific solvents are those 1n which G 1s butyl or 2-ethyl hexyl or octyl
phenyl tmore specifically pare (1,1,3, 3-tetra;nethylbuty1) phenyf_\. Dilute solu-
tlons of these acldic esters of orthophoephoric acid in toluene are able to
pull th(IV), the rare earth ioms, Zr(IV), Np(IV), Pu(IV), Bk(IV) and many other
ibns into the organic phase with partition coefficients ranging up to several
thousand. The partition coefficlents are strong functions of the concentra-
tion of the extracting agent and of the acid so there 1s considerasble opportuni-
ty to manipulate experimental conditions to favor the preferential extraction
of certain iomns, particularly such highly extractable ions as th(IV). No de-
tailed date on the extraction of thorium has been published and there are no
detalled descriptions In the literature on the use of solvents of this type for
the rediochemical separation of thorium., It seems clear, however, that the
extraordinarily high partition coefficients for thorium 1n the presence of these
ecidic esters of orthophosphate will find many applications 1n radlochemistry.
' Some idea of the necessary pretreatment of the solvent and of the solvent power
of these solvent systems can be obteined in publiéetions by Peppard and his co-
45-I7 A pape:rhT on the extraction of Bk(IV) from rare earths and other -
impurities indicates the type of separation of tetrepositive and tripositive ions
which cen be achieved. Peppard, Moline and Mason'' T put Cm(III) end Bk(IV) into
an aqueous solution 10M in Em3 and O.1M in KZBrO3 (to maintain the Bk in an
oxldized state) and contacted the aguecus phmse with an 0.15 M solution of
di-ethyl hexyl phosphate in n-heptane. The curium remained in the agqueous
phase (K, = 1.k x 1073) while the berkelium was quantitatively extracted
(x,, = 1900). -

In addition to tributyl phosphate and the mono and dlalkyl esters of
Phosphoric acld, there are several other classes of phosphorous containing
compounds which have received considersble study &s poesible extracting solvents

workers,

20
for urenium, thorium and other elements. B8everal of these campounds have ex-
tracting power much greater than that of +tributyl phosphate. Some of the

most promleing solvents are of the followlng types, where the letter R represents
an alkyl group.

RO o
\Pz dialkyl phosphi xid
sphine oxides
7 N\
R R
R 0
N_A
P trialkyl phosphine oxides
R’/ N R

Esters of pyrophosphoric acid

Other clasaee of solvents which are very promlising for many applications in
the extractive metallurgy of the heavy elements are the mono - di - trli - and
quaternary alkyl ammines. A number of reports have been written on these phos-
phorous and ammine solvents and most of them can be located with the aid of
Nuclear Sclence Abstracts. It 1s premature to discuss these solvents in any
detall here because very little has been published concerning their use in the
radiochemical separation of thorium. There is no questlon, however, that radio-
chemists will find geveral of these new solvents highly useful to them.

As a8 single example, the solvent trli-n-octylphosphline oxide is reviewed
briefly in Taebles 7 and 8 . This data 1s teken from an Osk Ridge Report by
Ross and Whiteha. It cen be seen that thorium is very highly extracted into
en O.I'E solution of tri-n-octylphosphine oxide in cyclohexsne from dilute HCI,
HCth and particularly, dilute HNO3. It is particularly well extracted when

the aquecus phase is 1M in HNO3 and 1M in sodium nitrate.

8. Ion Exchange Behavior of Thorium
Cation Exchange

The tetrapositive thorium ion is adsorbed on cetlon exchange resins more
strongly than most other ions. This fact makes 1t possible to adsorb thorium
tracer from a large volume of solution onto a small amount of resin. It mskes
it feasible to separate thorlum from most other lons by washing the resin on
which the thorium is adsorbed quite thoroughly with a mineral acid solutlon or
some other suliteble leaching agent to remove the less-strongly-bound ions.
When both the thorium and the unwanted contaminaente are present in small con-
centrations the method 1e particularly applicable,

Diamond, Street and Seaborghg studied the adsorption of tracer ilons on the
resin Dowex 50 (a cop&lymer of styrene and divinyl benzene wlth nucleonic sul-
fonic acld groups as exchange sites) and the elution of the ions with hydrochlor-

21
ic acid of varying coficent:‘ra.tion. At all concentrations of HC1,thorium (IV)
wes very strongly held by the resin end such ions es 8r(II), La{III),CE(ILI)
and Ac{IIT) were much more rapidly eluted. Thorium (IV) on the resin is reedily
washed free of heavy element tetrapositive ions such as Kp(IV) or Pu(IV) with
HCl1 6 molar or greater in concentration beceuse the higher elements in the tetra-
poaitive state form strong complexes with hydrochloric acid. This is true also
of uranyl lon. .

Thorium ie removed from a cation exchange reesin by passing a complexing
agent through the column of resin to reduce the effective concentration of free

TABLE 7 EXTRACTICN OF THORIUM FROM ACID SOLUTICON
INTO TRI-N-OCTYLPEOSPEINE OXIDE (‘TOPO)
Thorium present _JJ..3 mg ThCl, , Th(ClOll_)h_
| | 11.5 ng Th(R0,),
TOPQ, 0.1 M In cyclohexane, 9 ml

Equilibration time - 10 minutes
Data from Ross and White, ORNL 2627

 

Acid Molarity E::'lg

HC1 1M Q.26 H,S0, 1M 0.3
3M 11 2 M 0.3
oM 145 34 0.
TM™ 208
8 M 64
9 M 28
10 M 32
HC10, O.5 M 82
1.0 M 26
2.0 M 9.9
L.OM 8.3
5.0 M 16
6.0 M 56
HNO, 1M 2100
2M 420
h M 78
6 M 27
10 M 10

 
TABLE 8 EXTRACTION OF THORIUM FROM ACID SOLUTION
INTO TRI-N-OCTYLPHOSPEINE OXIDE (TCPO) IN THE
PRESENCE OF NITRATE AND CHLORIDE SALTS

TOPO, 0.1 M in cyclohexene, 5 ml
10 minute equilibration i
Data from Ross and White ORRL-2627

 

 

 

Aqueous Composition ' Ez;g
1 M HNO + 1 M NaNoO, - 3800
1 ¥ HNO + 2 M NaNO, 1900
1 M HNO, + € M NaNO, 1200
1 MECL + 1 M NeCl 1.5
1 M HCL + 2 M NeCl 6.1
1 MHCL + 4 M NeCl 107
1MECL + 1/3 M Alcl, 0.4
1 M EC1 + 1 M AlCl, ' 11
1 M HC1 + 2 M AlC1 1100

3

 

thorium ions and thus reverse the adsorption procesa. Sultable complexing agents
are buffered citric acid, buffered lactic aecid, fluor._’né.e ion, carbonate iom,
sulfate lon, oxalate ion, etc.

:Ba.ne5 0 separsted emall emounts of thorium from 0.15 M urenyl nitrate solu-
tion contalning 0.1 M Bm3 by paseing the .solution through a bed of Amberlite
JR-1 resin. The colurn was thoroughly washed with 0.25 M EE&J‘_ to remove all
the urenivm. The thorium wes then eluted with 1.25 M Naflmh-

Dryasensl separated UI_L('I'h23h) from uranium by adsorbing the UX, on Wolfat-
it XS from a 24 HC1 solution of uranium. The pure UX, is then eluted with 0.5 M
oxalic acid. The solution is evaporated to dryness and the oxalic acld is
aublimed off leaving a carrier-free thorium sample.

Asaro, Stephens and Perl_mansz prepared radiochemically pure samples of
| 'I'h228 for @ and y spectrum studies by adsorbing an Impure mixture of 'I’]:l228 and
1ts deughter producte on a short Dowex-50 resin column (3mm dismeter x 3 cm

height) from a dilute nitric acid solution. The columm was jacketed to allow

| operation at 8'70 € (the temperabure of the vapors of bolling triethylene glycol).
The redium, lesd and bismth fractions were eluted with 4M nitric acid, after
which the thorium wes stripped with & 50-volime-percent solution of lactic acid
at pH3. One ml of lactic acid sufficed to remove the ThZ2C from the colvmn.

The lactic acld could be removed by sublimation. The high temperature opera-

23
tion was eseentlal for the rapid removal of the thorium in a small volume of
eluting solution.

Procedure 9 1n Section V of thie report contains additional comment on the
adsorption and desorption behavior of thorium on cation exchange resins.

Anion BExchange - Hydrochloric Acid Systems

The remarks on the use of aenion exchange resins in the rediochemical purl-
fication of thorium will be divided into two parts. The first part will discuss
hyd.rdchloric acid 'syfit in. uhic".h thordum forms no negative complexes and
hence is not a.dsor'bed. 'by' a.nion excha.nge resins. Several 6the1; heé:v'yl elements
end several fission product elenents do form negative 1ons ig concentra.ted h.y--
drochloric acid and can be readily removed from a thorium solution by ad.sorp-
tion on & small amount of ion exchange resin. - A number of possible separations
are rea.diiy a.;;pa.rent from a consideration of the following data on adsorption
behavior 1n the case of the resin Dowex-1 (a. coplymer of styrene and divinyl
benzene with quaternary ammonium functional groups.)

Uranium(VI), neptunium (VI) end plutonium (VI) readily adsorbed
from hydrochloric acld solutioms & M or greater in concentration. Readily
desorbed with 0 to 3 M HCl.

Neptunium (V) readily adsorbed above 4 M HCl. Protactinium (V)
readily adsorbed above 8 M HCl.

Thorium (IV) not adsorbed at any HC1 concentration. Neptunium(IV)
adsorbed above 4 M HCl. Plutonium (IV) adsorbed strongly sbove 2.5 M HC1 .

Plutonium (ITI) not adsorbed at any HCl concentration, Lanthanide
rare earths not edsorbed at any HC1l concentration. Americium and higher
actinide elements in the tripositive oxlidation state very slightly adsorbed
in highly concentrated HCl.

Kraus, Moore and Nelson5 3 investlgated the anlon exchange behavior of thor-
lum, protectinium and uranium 1n hydrochloric acld solutions and suggested sev-
eral alternate procedures for the clean separation of theae three elements from
each other. For example, a mlxture of the three lons in 8 M HC1l may be passed
through a Dowex-1 colurm to adsorb uranium and protactinium et the top of the
column. Thorium passes through the column quantitatively. The protactinium is
rapldly eluted with 3.8 M HCl. The uranium elutes somewhat later. Alternatively
the protectinium may be eluted with a nd.x-t.ure of T M EC1 plus 0.11 M HF leaving
fhe uranium firmly bound to the resln. The presence of fluoride ilon causes a
dramatic decrease in the distribution coefficient for protactinium without affect-
ing that for uranium., After the protactinium is off the column the uranium 1is
rapldly desorbed with 0.5 M HCL.

Many of the fisslon product elemente form adsorbeble negatively-charged
chloride complexes in hydrochloric acid. Those which do can be removed from a
solution of thorium by contact of the solution with a sample of resirn. An

24
excellent overall review of all elements in the perlodic system and a good

bibliography is to be found in the 1955 Geneva Conference paper of Kraus and
54

Nelson” .

Dowex-1 resin are zirconium(IV), hefnium{IV), iron(IIT), zine{II), cobalt{II),

gallium(III), molybdenum(VI)}, cadmium({II), tin(IV), tin(II), antimony(III),

antimony(V), mercury(IT}, bismth{IIT), and polonium{IV). It is noteworthy

that thorium appears to be the only metallic element of the fourth group of

Some importent ions which may be removed from a thorium solution by

the Pericdic Syfitem.which canncot be adsorbed by a strong base anion-exchange
resin from concentrated hydrochloric acid soclution. The.differing behafiior okif
thorium(IV) and ziiconium(rv) is particularly notéwortny in this comnection be-
cause 1n some raediochemical procedures zirconium lodate or scme other zirconium
" compound is used“as a carrier precipitate for thorium. The carrier ion can be
removed easily by placing the thorlum tracer and zlrconium carrier in 9-12 M
HC1l and remo?ing the zirconium with anion exchange resin.

Polrier and Bearse5ha of the Battelle Memorial Institute wrote a report
on the separation of uranium end thorium with particular reference to the pro-
2essing of monazlte sands. The s eparatiorn of uranium from thorium in carbonate,
HC1 and stoh solutions by anlon exchange resins was studied in scme detall
including the effects of extraneocus lons, types of resin, etec.

Anion Exchange Nitric Acid Systems
In the second maln part of the discussion of the anion exchange behavior

of thorium, fie tufn to a consideration of nltric ecld systems. A few years ago
the surprising discovery was made55 that thoriufi forms adsorbeble nitrate com-
plexes in nitric acid solution over a wide range of nitric acid concentfation
with maximim absorption occurring near TM EN03. This fact can be made the basis
of a number of lmportant radlochemical separatione such as the separation of
thorium from rare earths, from zirconium, from uranium, from actinium and a
number of other elements. |

Danon55 reports that the ebsorption of thorium on Dowex-1l, 8% divinyl-ben-
zene 50-100 mesh, expressed as a distribution coefficient D (amount of thorium
per gram of dry resin divided by the amount of thorium per ml of solutiom),
increases from D = 300 and decreases slowly to D = 210 at 10 E'HNO3. The
thorium is immediately desorbed from & Dowex-1l column with dilute HCl.

"Carswe1;56 investigated the adsorption of ThoSC and UZSS tracer by De-

Acidite EF (nitrafe form) from HNO3 solutions. Some of his values are given
in Teble 9. Using these resulis Carswell separated a mixture of thorium and
uranium by adsorbing both on the top of & 2 mm diemeter by 8 em long column of
De-Acidité FF from & small volume of 6 E.HN03 and then eluting the uranium elowly
wilth y M nitric acid. The separation was not good at room temperature but was
satiéfactory at TTOC. The thorium was eluted from the column wilth pure water.
The number of elements which form negatlve complexes with nitrate ion 1s
smell and a large number of ions such as the alkalis, the alkaline earths, the
rare earths, etc. can be separated rapldly and cleanly from thorilum by adsorb-

ing the thorium on Dowex-l, Dowex-2 or De-Acidite FF resin fram 6-10 M ENO3

Even zirconium cen be separated as it 1s only weé.k_'Ly adsorbted. Same combina-
tione of impurities might best be removed by a two step anipn excha.née treat-
ment based on the differing bebavior of thorium and its contaminante in chloride
syetems and secondly in nitrate systems.

The U.S. Naval Radiological Defense Iaboratory has published a serles of
report557’58 on the anlon excha.nge_ behavior of a number of heavy element and
fission product ions from HC1, m3, E,80, snd E.PQ, solutions. Figures 6 and 7

TABLE 9 VOLUME DISTRIBUTION COEFFICTENTS FOR ADSORPTION OF Th23° AND y233
TRACER ON DE-ACIDITE FF (settling rate 3-1.4 cmjnin) Data from Carswell’®

 

Molarity Distribution Ccefficlent
'EHO3 : ~ Thorium Uranium

2 2.1 0.7

4 20 2.6

6 140 5.5

8 200 5.5

 

 
  
 

 

 

 

 

 

 

 

 

< 1op

e £ Figure 6  Equilibrium

. f edsorption of thorium and
0 ‘ . |} ‘BeV_era.l other elements b;y.

~ f-fi{ Dowex-z; 8 percent DVB, -

- ; / ) ~ 200-400 mesh from mitric

B E.-I . ! ' a.cid Data from Blmney,. |
al—1 11 T : i UJJ_H-'\- L1 11t B_a.]J.ou__, '.Psins_cua.l a.nd Fotj_.b-?.' :

al 1.0 10 © . 100
 

10,0004

ot

1000

 

e

 

 

Kg
o

 

101

 

10

 

T TTTIT
/
ol

I
ol
-.T

 

 

 

 

 

o
0.1 I EEI \"-L_LL-H’Ui\ |ttt
o1 10 10 100
N H,50,
Figure 7 Equllibrium adsorption of thorium and several other

elements by Dowex-2 from sulfuric acid solution. Data from Bunney,

Ballou, Pascual and Fot157.
summarizlng results for HNO3 and Ezmh systems make 1t poseible to devise g
number of separations. Note the peculiar shape of the adsorption curve for
thorium in HBSO“'

Da.non5 describes the separation of tracer amounts and milldgram amounts

of thorium (IV) from tripositive rare earth ions using Dowex-l and nitric ecid
systems.
V. COLLECTION OF DETATLED RADIOCHEMICAL
PROCEDURES FCR THORTUM

PROCEDURE 1
SBource - W. W, Meinke, report ABCD-2738, pp. 262. Aug. 1949

Target material: Tracer Pa separated . Tme for geparation: Beveral hours
fram 60 in. bombardment of lonium,

Type of bombardment: (Milking experiment)
Yield: As high as 50 percent possible Equipment requlred: Stirrers and TTA
Degree of purificetion: Decontaminate fram 107 c/m Pa, 106 c/m U, and 10° c/m Ac,

Advantages: Gilves carriler-free Th, e thin plate for pulse analysls, and good
purification aelthough not speed.

Procedure:

1. Nitric acild used throughout. Meke semple 6K acid and TTA extract (with
O.4M TTA in benzene) five times with double volume of TTA, stirring 5 min
for each extraction. (Removes Pe into TTA ~70 percent or more per pass).

2. Evaporate to dryness (wash twlce wlth water and take these weshings also to
dryness) and teke up in acid pH 1.0, TTA extract with equal volume (0.25M
TTA in benzene) stirring 15 min. (Th into TTA but not U or Ac.)

3. Repeat TTA extraction of ptep 2 with fresh TTA and combine the extractions,

4. Wash TTA with equal volume of pH 1.0 solutlon for 15 min., (U contemination
into acid,)

5. Wash TTA with 6N scid (equal volume) and stir 15 min. (Th into acid.)

6. Repeat steps 2, 3, and 4, (Repeat wash as in step 4 1f necessary for
further U purification.)

7. Plate out the 0,25M TTA on Pt plates end flame,

Remarks:

Bee curves of Hegemann (JACB T2, 768 (1950) ) for percentage of extraction
into TTA ve. pH for Th and Ac, At pH of 1, Th should go into the TTA
almost campletely, but U should only go in less than 10 percent, perhaps
as llttle as 2 percent. Ac will not go into TTA until ebout pH 3 or so,
and of couree Pa goes in up to about 6K or BN acid,

PH conditions for separating Th from U by TTA extractions are quite

eritical!

Equivalent and molecular welght of TTA is 222 g.

28
PROCEDURE 2
Source - D.B. Stewart in report AECD-2738, edited by W.W. Méinke. Aug. 1949
Target material: UO_(NO_) 6H 0 in which Time for separation: 24 hr
le has come to eauil%bglum

Equipment required: L4O-ml
centrifuge come

Yield: 50,000 to 10,000 c/m from 20 g UNH
Degree of purification: Factor of ~10" from U

Advantages: Good yield with small amount of inert carrier. (Very voluminous
insoluble precipitate. Uranium does not precipitate at all.)

Procedure:
1. Dissolve 20 g of UO (mo3)2 +6H,0 in 20 to 30 ml of 0.01 ¥ ENO, in 40-m1
centrifuge cone and warm solution to about 80 C in a hot water bath, Add
0.5 to 1 mg of Zr carrier as nitrate.
2. Add 5 ml of a saturated solution of m-nitrobenzoic acid in water and con-
tinue warming for about 1 hr. Let stsnd overnight. '
3. Centrifuge, decant supernatant, and wash Zr (csnhnozcoo)h twice with
0.01N HNO3 + m-nitrobenzolc acid.
Remarks:
Seturated solution of m-nitrobenzoic acid made up by dissolving 400 mg of
the material in 100 ml of H,0. Heat to 80°C. Allow to stand sveral hours and

f1lter to remove excess and lmpurities,

PROCEDURE 3

Source - W.W. Meinke in report ABCD-2T738. Aug. 1949.

Parent materiel: Tracer Pa and daughters Time for separation: ~3/4 hr
(both & and K)
Milking experiment Equipment required: Standard

Yield: Only ~40 to 50 percent Th per cycle

Degree of purification: 2 to 3 percent Accarried per cycle, other elements
decontaminated by factor of at least 100.

Advantages: Good procedure 1f Th iz present in mpproximately the game amount
ag other mctivitles.

Procedure: Pa daughters in 6N HC1l after milking from Pa in TTA (procedure
91-1 in AECD-2738).

1. To ~10-cc deughter sclutiom, add 1/2 to 1 mg df Zr'l']‘L carrler and enough
H3P0 to make ~4M in POh Centrifuge precipitate (carries Th*h).

2. Add to the precipitate 3 mg of La +3 carrier and dilute with 1N HCl. Add
HF, digest, and centrifuge.

3. Metathesize the fluoride precipitate to hydroxide by adding canc. KUH.
Centrifuge. Wash once with alkaline water.
PROCEDURE 3 (Cont'd.)

4, Dissolve in HCl end repeat steps 1 to 3, reducing amount of La carrier.

5. Plate as the LaCl3 solution, flame, and count.

Remarks:
ZT3(P°u)h

in the heavy region. Yield lost in the LaF3-La(0H)3 precipitation.

Do not use this procedure if more purification is needed than 1s glven by

precipitate quite specific for carrying Th+h from cther elements

two cycles, since the Th yleld will be very low.
LaCl3 solution when eveporated sticks to Pt plates much better than the
precipitate encountered in thls procedure. ’

PROCEDURE L

Solution of Thorium Metsl and Thorium Dioxide
Source Newton, Hyde, end Meinke in report AECD-2738.

Thortum metal can be dissolved rapidly in conc. HCl, but a considerable
amount of black insoluble residue is formed in the process. If a few drops
of (Rfih)ZSiF6 solution (enough to make ~0D.1 M) are added to the HC1l before
solution 1s started, the black residue ia dissolved, leaving only a small
residue of thorium oxide (< 1 percent) in the clear solution.

Thorium metal can be dissolved in conc. HN03 with the addition of (Kflh)z
BiF, (or HF) to 0.01M. The metal becomes passive to solution from time to
time, requiring further additions of acid and SiF6 .

If the excess H!O3 1s evaporated off, care should be taken not to allow
the solution to go completely to dryness, or difficulty soluble ThO2 willl be
formed. _

If 1t is desired to dissolve ThO,, the HROB_(NHH)ZSiFG solution should be
used, and the mixture should be heated with stirring for several hours. ThO

when first formed, is much more soluble than after prolonged heating.

2)

PROCEDURE 5
Source - R.N. Osborme in report UCRL-L377, edited by M. Lindner. Aug. 195L.

Purification:

Thorium isolated from uranium targets showed no evidence of forelgn alpha
particle groups upon pulee analysis. The complex beta decay and growth was
always reproducible and could be accounted for on the basis of the isotopes
known to be present. Thds reproduclbility suggests a high degree of beta
purity.

Yleld: At least 50 percent.

30
PROCEDURE 5 (Cont'd.)

Separation time: About four hours.

1.

To about 20 ml of the active soluticn in 8N HNO3’ add an appropriste
thorium tracer and about 5 mg lanthanum carrier. Add 20 drops 27N HF.
Centrifuge precipltate and wash once with dilute HNOa-HF. Discard super-
natant and wash.

To the precipitate add 3 ml water, 1 ml 5% 33303 and.five:drops cone,
HN03, in that order,

To the resultant soclution add 5 ml 3N RaeOH, Centrifuge and wash
precipitate twice with 3N NaOH. Discard supernatants.

Add 10 m1 1.5M HN03 to the precipitate.

.Equilibrate the solution, by vigorous stirring, with 5-ml portions of

thenoyltrifluoracetone (TTA) in benzene*, ellowing ten minutes for each
equilibration. Discard benzene phases. '

AdJust agueous layer to pH 1.5 (buffering not necessary) with NaOH, snd
equilibrate with 20 ml TTA solution in benzene for 15 minutes. Separate
layers and discard aqueous phase. Wash benzene layer with two 10-mi
portions of HNO3 at pHE 1.5.

Equilibrate benzene solution with 5 ml 3N HN03 for 15 minutes. Separate
layers and discard benzerne phase. The 3N HNO_ solutlion will contaln

3
carrier-free thorium, unless Th232 was present in the original solution.

 

*
Note: If large amcunis of Th

232 should be present in the origlnel soluticn,

the above procedure might become avkward because of large precipitates
and the difficulty in extrecting large mscro amounts of thorium into
TTA. In this case, the use of an assoclated chelating compound,
"Dagmar,” (1-(3,L4-dichlorophenyl)-4,%,5,5,6,6,6, heptafluoro-1,3
hexanedione) in place of TTA is preferable because of the much
greater solubllity of this thorium chelate in benzene.

31
PROCEDURE 6

Source - unpublished procedure obtained from G.M. Iddings.

Note - This procedure was developed to rerover gram amounts of ionium which
had been irradiated in a reactor to produce Pa23l end u2iz,

Dissolve pile irradimted Al slug containing 1 gm m™23° in 6§ NaoH.
Centrifuge out the ThOz.
Dissolve the ThO2 in concentrated HNO
Precipitate Th(OH)h with NaOH,

(Pa23l and U232 carry down with the Th230.)

Wash the fluoride from the hydroxide precipitate.

Dissolve the Th(OE)h with conc. HC1.

Put solution through Dowex-2 enion column.

(U232, Paz3l, and Zro’ stick; 230 dces not stick.)

Wash column with 10 KN HCl.

Save conc., HCl solution and wesh containing Th23o and fisslon products for
further purification.

Elute PazBl from anion columm with 9 N HC1 end 0.1 N HfF.

(U232 and Zr95 stick to anion resin.)

Elute Uz32 (together with ngs) from colum with 0.5 N HCl.

Th230 purification:

Add conc. HN03 to the Th solution and boll to destroy the HCI.
Evaporate Just to dryness and redissolve in distilled water.
AdJust the acidity of the solutlion to pH 1 with nitric acid.
AdJust the vol. so that solution is ~0.1 M Th230 (In this case 4% ml for the

gn of Thzao.)
Extract the Th with 80 ml of 0.60 M.Dagmar* in Penzene 15-20 minutes.
Add enough naCH to the aqueous phase to bring the acidity to pH 1.
(2.9 ml of 6 K NaOH for 1 gm Th).

Continue the Dagmar* extraction for 15-20 minutes more.
Separate phases and wash organic phase with 0.1 § HNO
Drain off the aquecus wash.
Back extract the gm of Th23o

Repeat back extraction. (Degmar extraction separates Th from all fission
230

Wash precipitate.

3 eand 0.05 M HF with boiling.

230

3"

Prom organic phase with 8 N HEO3 ~10 m.

products except Zr. Zr was previously separated from Th on the anion
resin column. )

Precipitate Th(OH)h with NE,OH.

Wash precipitate.

—
Dagmar refers to the p-dlketome reagent.[1r(3,h-dichlorophenyl)-h,h,5,5,6,6,6
heptafluoro-1,3 hexanedione] .
PROCEDURE 6 {Cont'd.)

Ignitg precipitate to ThO_, in Pt crucible with water ccoled inductiom ecoil in
glove box.

Load new Al slug with t]:eThOz-- ready for pile irradiation.

2

PROCEIURE 7
Source - J.W. Barnes and H.A., Potratz in "Collected Radiochemical Procedures” ’
Los Alamos report LA-1T72l. Jan. 1958.

230

A, Determination of Ionium{Th“’") in Coral Samples

l. Introduction

The determination of ionium (Th230) in coral samples involves cerrier free
separation of the total thorium content by use of TTA[k,k4,4,trifluoro - 1 -
(2-thienyl) ~ 1,3 - butanedione]. Thorium is finally adsorbed on a cation
exchange column and eluted with oxmlic acid. It 1s then @-counted and pulse
enalyzed, with T}:L228 being employéd to determine chemical yleld. - The chemical

yield is 50-70%. Duplicate samples may be run in about 6 hours.
2. Procedure

Step 1. Transfer about 2 g. of coral, weighed to the nearest 0.1 g., to
a 600-mL beaker. Add ThZ2C tracer in known amount (5-100 ¢/m) end wash down
the sides of the beaker with H,O. |

Step 2. With a speedyvap wvatch glass in place on top of the beaker,
gradually add 75 ml. of cone. B:NO3 , dropwise at first to prevent excessive
foaming. FPlace the covered beaker on & hot plate and mllow the solutlon to
boll until the begetable fibers present i1n most samples have disintegrated and
brown fumes are no longer evolved. Cool to room temperature and cautlously
add TO% HC10,, . (During this and subsequent steps which involve fuming with
HEth_, the operator should wear a face shield and rubber gloves.) Evaporate
to dense white fumes and continue heating for at least an additional 5 minutes.
Copl to room tempéra‘ture and dilute to about 200 ml. with H_O.

2
Step 3. Add conc. IIEhOH until the solution is Just acid, and then adjust
the pH to 2.0-2.5 with the use of 3M REhCH and 3IM B!Cloh.
Step k. To a special separatory funnel add the solution

from Step 3 and 150 ml. of O.5M TTA in benzene. 8tir for at least 1.5 hours
with e vortex stirrer driven at high speed by means of an air motor. Permit
the layers to separate, draw off the aqueous layer, and discard. (Note 1).

Step 5. Wash the benzene layer, containing the thorium complexed with TTA,
for about 30 seconds by stirring with 100 ml. of nzo. Discard the washings.
Wash again with 50 ml. of Hzo and discard the washings.

33
. PROCEDUEE 7 (Cont'd.)

Btep 6. Extract the thorium from the benzene by stirring for 3 minutes
with 100 ml. of 3M HCI. |

Step 7. Transfer t.he'aqueous phase t0 a baker and evaporate with an air
Jet on a steam bath until the volume has been reduced to 20-30 ml. Transfer
the solution to a 40-ml. centrifuge tube and contlnue evaporation to a volume
of 1-2 ml. '

Step 8. Add 1 ml. of conc. IHIWO3 end boil over a flame until brown fumes
are no longer evolved. Cool to room temperature, then add 0.3-0.% ml. of TOP

l':II:lO‘h, ann_i boll to the eppearance of_white fumes. .Cool to room tempera-
ture and dilute to about 3.5 ml. with HZO.

Step 9. Transfer the solution to the top of a Dowex 50 - x 4 cation
exchange column (Note 2) and rinse the centrifuge tube with 0.5 ml. of water,
adding the rinsings to the column. (If air bubbles are present in the calumn,
they should be removed by stirring with Pt wire.) Force the solution through
the colum under 2 pounds of air pressure, and then wash the column with 3=l
ml. of 3M HCl under the same pressure. Discard the first effluent end the wash.

Step 10. Pour 2 ml. of 0.5M H,C,0) onto the columm and allow the solution

to run through under atmospheric pressure. Collect the drops from the column
on 1" square (13 mil) Pt plates, which are placed just far enough below the
column so that drops separate'from the tip before hitting the plate. ' Nine
drops of effluent are collected on each of four plates. Dry the plates under
a heat lamp; then flame in an open flame.

Step 11. a-count the indlvidual plates and then pulse analyze those
plates which carry the activity (Note 3).

Hotes

l. The chemical yleld may be increased slightly by taking the aquecus
layer through an additionasl extraction. This was done with some of the semples.

2. The tubes which are used to support the resin columns were constructed
by blowing out the end of a 15 ml. centrifuge tube and sealing on & length of
'3-4 mm, 1.d. tubing. | |

Dowex 50-xh resin was water-graded and the fractlon which settled at the
rate of 2-5 cm./min. was selected for use. This was washed several times with

conc, HCl and then with IZO.
To support the resin column, a layer of HCl-washed send abcut 5 mm. thick

is pleced in the tlp of the column tube. A elurry of graded, HCl-washed resin
is then added by means of a' syringe pipet, tfie resin slurry belng introduced
into the tube near the bottom so me to eliminate air bubbles. The emount of
slurry added should be sufficilent to produce a column 7-9 cm. in length after

3
PROCEDUEE 7 (Cont'd.)

settling. Bettling of the resin may be hastened by application of up to 10
pounds ailr pressure tq the top of the column. To permit pressure control, the
connection from the air line to the top of the column is made through a
reducing valve. Slurry liquid ie allowed to flow through
the column until the 1iquid level® reaches the top of the resin; the stopper is
then removed from the top of the column tube. Ailr must not be permitted to
enter the resin colum. If air does 'ber., the resin is reslurried to
remove air bubbles. The cation column prepared as described above 1s washed .
with 2=3 ml. of IM HCth and is then ready for use.

3. Pulse analyses were made with 100 channel analyzer operated at a

window setting which placed the ']II:l228 peak in the 83-87 channel region.

PROCEDURE 8
Source - J.W. Barnes and H.A. Potratz in "Collected Radiochemical Procedures”
Los Alamos report LA-1721. Jan. 1958.
Determination of Jonium in 0ld Fission Product Material.

1. Introduction

The method described for the determination of ionium (Th23°) in coral
samples (Procedure 7) is not satisfactory for fission p:roduct solutions inas-
much as the plutonium présent in the latter comes through the separation
procedure and seriocusly intereferes in pulse analyses. To overcome this
difficulty, plutonium is removed on an anion exchange columm from concentrated
Eydrmhloric acid medium immediately befofe thorium is absorbed on the cation

column.

2. Procedure

Step 1. To an liquot of the sample in a 150-ml. beasker add T]:Lz28 tracer

in xnown amount (5-100 c/m) and then boil to white fumes. Dilute to 40 ml.
with H,0.

Step 2. Repeat Steps 3-7 of Procedure T except cut down amounts of all
reagents by a factor of five.

Btep 3. Add 0.3-0.k ml. of 70% HC10, end boil to the appearance of white
fumes. Cool to room temperature and dilute to about 4 ml. with Solution A.
(Solution A comsists of conc. Hnba mixed with conc. HCL in the ratlo of 0.1
ml. ENO, to 15 ml. of HCL.)

Step 4. Transfer the solution to the top of a 5 em x 2 mm. Dowex Alx2
anion exclmnge column (Note 1) and rinse the centrifuge tube with about 0.5
ml. of Salution A, adding the rinzings to the column. (Observe the usual pre-

35
FROCEDURE 8 (Cont'd.)

cautions to avoid introducticn of air bubbles.) Force the solutlon through
the_colmni under 1-2 pounds of air pressure and collect the effluent in a
40-ml. test tube. Rinse the column with 3 ml. of Solution A under the same
pressure and collect the effluent in the. same teat tube. Pu 1s retained on
the column and thorium comes through in the effluent.

Step 5. The effluent is evaporated with an air Jjet to about 1 ml. on &
steam bath. '

Step 6. Add 1 ml. of comc, nma and boil over a flame until brown fumes
are no longer evolved. Cool to room temperature and add 1 ml. of 70% of HC10, .
Boil until white fumes appear, then cool to room temperature, and dilute with
HZO to about 3.5 ml. '

Step 7. Repeat steps 9, 10, and 11 of Procedure 7.

Rotes

1. The anion exchange column is prepared in essentially the seme manner
as the cation column (See Note 2, Procedure 7). The resin used is'a 0.5-2
cm]m:l.n. fraction of Dowex Al-x2. The resin is prepared for use by washing
with Solution A.

PROCEDURE 9

Source - J.W. Barnes in "Collected Radiochemical Procedures”,
Los Alamos report LA-1721. Jan. 1958.

Tracer Methode for Analyeis of Thorium Isotopes

l. Intreduction

The principal pm‘ii'iéation step in tracer work with thorium isotopes
depends on the fact that the relatively small, highly charged thorium lon 1is
more tightly bound to a cation exchenge resin such as Dowex 50-Xk than the ions
of most other elements. Thorium 1s adsorbed on the resin bed and washed with
dilute hydrochloric acid solutions to remove most Impurities; then it 1s
eluted fram the column in a very narrow band with oxalic acid. Since thorium
oxalate is insoluble, macro quantities cannot be-eluted from the colum in
this way. The Dowex 50-X4 resin with 4% divinyl benzene in the original poly-
styrene bead 1s more satisfactory for this separation than any of the other
cross-linkages. Dowex 50-X2 does not adsord tharium strongly emough under the
experimental conditlions to be describeds the higher cross-linkages in Dowex
- 50-X8 or -X12 do not allow impurities to be removed at a reascmable rate, and
also cause so much ta':L‘L:Lng in the elution that the thorium is not concentrated

36
PROCEDURE 9 (Cont'd.)

in the small volume desired. In tracer work with thorium, it is well to awoid
solutions containing nitrate, fll.ibride, sulfate, or phoaphate, since these cawme
considerable losseg in either anion exchange or cation exchange column steps.
In the analysis for any thorium lsotope in a soluticm containing organic
matter such as incompletely. decomposed filter paper, it 1s deemed necessary
as a first step, after the addition of a sultable tracer, to boll to demse
fumes with perchloric acid. Even though thorium has only the one stable valence
state 1n solutlon, there is very strong evidence for lack of exchange between
added tracer and the radioisotope already in the solution when a hydroxide pre-
cipitation is performed without the fuming ahead of it. Whether thles apparent
lack of complete exchange results from complexing of thorium by organic mole-
cules that survived the initiml solution of the sample in nitric and perchloric
aclds, or from the existemce of thorium in the sclution as some polymeric lom,

is probably difficult to determine. Routine fuming of this type of semple has
markedly improved the precision of the analysis. If the analysis 1s performed

on solutlons contalining macro amounts of calcium, two precipitations of thorium
on some carrier hydroxide such as iron or a rare earth will result in a much
cleaner plate. Since most of the analyses were done on solutions containing a
very large excess of fission products, (Bection 5A), two Dowex 50-XL columms
were used. '

SBome of the zirconium and probably a few other unknown contaminants are
eliminated by adascrbing them from concentrated hydrochloric acid solution cm a
relatively high cross-linked, atrong-base anion exchange resin such as Dowex
1-X8 or -X10. Two of these columns are used, one after the other, if ome of
the beta-emitting thorium isotopes 1s being separated. If an alpha-emitting
thorium 1s belng purified, one of the anion colums may well be sufficient,
and if the sample contains fission products which are several days old and
excessive amounte of plutonium and neptunium are not present, the two cation
columns provide sufficlient decorntamination. .

Tracer emounts of thorium can be separated from uranium in quantities up
to ebout a gram with cne Dowex 50-Xh column. Amounts of uranium up to about
10 grams csin be adsorbed on & 150- to 200-ml bed of Dowex 1-X8 from concen-
trated hydrochloric acid, leaving thorium inthe effluent. A carrier-free
source of 'J!’n23l was prepared from 2 kg of oralloy by doing several -ether
extractions; then finally a cation colum was.employed to concentrate the:
activity in 1 to 2 drops of oxalic acid (Bectiom 5C).

Section 5B describes the application of the principles of separation
noted abové to the epecific analysis of thorium in coral or limestone saxples,
as develcped by W.M. Backett.
PROCEDURE 9 (Cont'd.)
2. Resins
Anion exchm ge resin AG 1-X8, 100-200 mesh, stored in conc. HCL.
(AG resins are analytical grade Dowex materials supplied by the Bio-Rad
Laboratories, 800 Delaware, Berkeley, California.)
Cation exchange resin AG 50-Xk, -50-100 mesh
Cation exchange resin AG 50-Xi, 100-200 mesh.

Both of the cation resifis are stored 1n 3M HCl. It may not be necessary
to do any further purification on the resins if they are obtained from Bio-Rad
Laboratories. However, it may be well to treat the resins as follows. Place
.a quantity of the resin 1n a large fritted disk funnel of medium or coarse
porosity. (In this Laboratory, we use a 12-cm fritted disk funmel sealed to a
foot-long plece of glasas tubiné so that much larger quantities of resin can be
handled.) The treatments described below are speeded considerably by draining
reagents into a large (2 to 4£) suction flask connected to vacuum to allow more:
complete removal of a reagent before the next ome is added. It -is helpful when
adding a reagent to the mmrtially dried resin to stir it up with a heavy
porcelain spatula, then let it settle and flow by gravity awhile td prolong the
treatment time before suction is applied and the reagent removed, The success-
lve reagents used for treating the resin are: An orgenle solvent, such as
acetone, or alcohol, which removes short-chain organic polymers not firmly
anchored in the resin matrix; water to rinse out the organic sclvent; conc.
HCl, containing about 1 ml of ZM HaBrO3 per 100 ml, to dissolve extraneous
inorganic matter. This 1s removed with water or dilute HCl 1n an amount equal
to 10 to 20 times the volume of resin being purified. The resin can be washed
with 3M EE,_LOE and then wlth water at this polnt, but it probably is not
necegsary. It should now be washed with 5 to 10 times its own volume of
vhatever solution it 1s to be stored in. If there are fine particles that are
undesirable, they can be removed by running distilled water upward through the
fritted disk at such & rate that they will float over the top, leaving ihe
bulk of the resin in the tube.

3. Equipment
Plpets, Normax |
Plpets ,-tranafer
50-ml and 125-ml Erlenmeyer flasks
Centrifuge tubes: 4O-ml short and long taper, and 90-ml
Test tube block
Stirring rods
Syringes, 10 ml
PROCEDUEE 9 (Cont'd.)

Tweezers

Centrifuge

Pt dishes

Heat lamp

Pt platee: 1" or 1-3/4 to 2" in dilameter

Water bath

Fisher burner

‘Manifold with as many outlets as the number of samples to be rumn at one time

Resin colums - 4 per sample: three that are 0.6 c¢m i.4. and 7 cm height,
and one that 1s 0.35 cm 1.d. and 7 cm helght.

The glass container for the column of resin 1s most convenienlly made
by 'sealing'a plece of the proper size of tubing, in thie case either 0.6 cm
i.4. by T cm or 0.35 cm 1.4. by T em, to the bottom of a tapered 15-ml cen-
trfiuge tube. If glase wocl is to be used as a support for the resin, the
- slze of the opening in the tip at the bottom of the colum 1s not very eritieal,
from ebout 0.3 to 2 mm being satisfactory. The hole size for a sand support
ghould not be much larger thsn 0.3 to 0.5 mm, and it is beat to put a layer of
coarse sand in first, and then cover this with a layer of finer material to
guarantee that the column will not be part .of the effluent. The sand should
be boiled and leached with HEl, or better, be made from glass.

The cholce between sand and glass wool ge & column support 1s mostly a
matter of personal preference. A glass wool colum plug 1s made by cutting
off a short piece of fiber, wetting it, rolling . 1into a ball, end pushing
this to the bottom of the column with a rod.

Pressure re tor

The pressure of ailr used in pushing solutions through columms 1s
reguleted by a disphragm reducing valve with a scale reading from zero to
100 1b and the first mark at about 4 to 5 1b.

4. Preparation end Standardization of Tracers and the
Calculations Involved in their Use

In analyses for the beta emitters '.l‘h23l and Thzah, !En230 is the best

tracer gince no daughters grow into it within a time that could affect the
mpalysis. It is desirable to use arcund 10,000 c/m of 230 tracer. It 1s
well to have on hand several standards made with the amount of tracer bheing
used in the analysis; then the chemical yleld is determined by a ratio of
sample-to-standard counted very close together, thus eliminating any small
error due to change in response of the alpha counter.

The beta counting efficiencies for ThZll and Th23"' are determined by

39
PROCEDURE 9 (Cont'd.)

mixing a known amount of '.I!I:z30 tracer with a known quantity of the appropriate
uranium parent, eithef U235 or U238. After a perchloric acid fuming to
guarafitee exchange and eliminate the nitrate that is probably present, the
solution is diluted to 2 to IM in H+ ion concentration and an AG 50-X4 column
Btep performed as in the last step of the fisslon product decontamination
(Step 9), with the one’exceptiom that a drop or two of 0.5M Na.'BrOS is added
to the 1initisl solution and to the wash to Insure that the uranium will be
present as U(VI). TU(VI) behaves the same as Ta(IV) on this column and will
lead to enougu deposit an the plate to cause errors in the glphe counting.
The directions for obtainlng large quantlties of Thz3l or Thzah for use as
tracers are given under- Sectlon 5C.° '

The best tracer to use in analysis for Th231 228

is Th ", as free from

Th229_a3 possible. Since Th230 and Th.z28 are both alpha emitters, the final
plate 1s pulse-analyzed to get the ratio of the two. The alpha energy of
.29 (as compared to that of Th?za) is 50 much closer to that of h23° that
tail correctione are much larger and more subJect to error when Th229 1s
present in the Th?za tracer. This tracer is made by the (d,2n) reaction’on
w232, | i

90'J:h232 (d,an)glPa232 —L>L 5 9211232 %;> 901‘]:1228.

It 1s possible to standardize a solution of Th228 by allowing it to

. decay untll all its daughters are at equilibrium, then alpha counting it
and subtracting the contribution of the rest of the decay chain. It 1s,
however quicker and more reliable to mix accurately-measured quantities
of Th22é and a known Th230 solution, fume with Hflloh, and then separate

' from daughter activities with an AG 50-XL column ag in Step 9 of the regular
fission product purification. The resultant plate 1s pulse-analyzed to get
the ratio of Th228 to Th23° which, when multiplied by the alpha count of
Thzao, gives the correct alpha count rate for Th22 . If this tracer is to be
used for an apprecimble length of time, a decay correction for its 1.9 year
half-1ife will have to be made. There is another correction to be made in
pulse analyses involving 228, me energy from 4,66 of the alphas of the
RaZ2% gaughter of ThZZ8 coincides with the amlpha pesk of Tho20. The time of
last separation of the daughter is noted. This 18 the time when the last HC1l
wash comes off the last AG 5o-xh column. '

This parent-daughter relationship falls imto the clessification of tran-
8lent equlilibrium, where the equation of radicactive decay is simplified to
‘the Pollowing: . .
_l—::lI ME
h-
L0

Né(t) = (e
"PROCEDURE 9 (Cont'd.)

224 8

vhere the subscript 2 refers to Ra and 1 refers to Thzz . N; is constant
for the times involved, so it is convenient to make up a plot of sznf against
time using the above equation. The elapsed time from the end of the BEC1l wmsh
on the last cation exchange column to the midpoint of the pulse analysis 1s
noted on the curve, the fraction Hz/N; read from the gmph, multiplied by
0.046, and subtracted from the counts under the'Th228 peak.

To get the countlng rate of Th230 in a sample with 'I'h2 ‘tracer,.the
ratio of the Th23°/'.1:h228 peaks is multiplied by the alpha counting rate of

Th228 as obtalned above.

28

S5A. Procedure for Thorium Isctopes in a Solution of Fission Products

Step 1. Pipet the tracer into an Erlenmeyer flask of the proper size;
use a 50-ml flask when the volume of sample plus tracer is less than 10 to 15
ml; a 125-Erlenmeyer for 12 to 50 ml. Plipet the sample into the flask, using
a clean plpet for each sample o that the sclutlon will not become contemineted
wvith the tracer. Add a few drops of .Fe carrler (carrier sclution 10 mg iron
per ml) and sbout 1 ml of conc. HC10). Evaporate to demse vhite fumes and con-
tinue heating for at least 2 minutes after their first appearance. This
evaporation 18 most rapidly done over & Fisher burner, but if there is no
hurry it may be done using an air Jet and either a hot plate or an oll bath.
Cool and add 10 to 15 ml of HZO and transfer to a short-taper LO-ml centrifuge
tube. There may be a fine-gralned residue of 8102 in the Erlenmeyer, but
thorium loss at this point is not very great.

Step 2. Add an excess of conc. NELOH, mix well, centrifuge, and discard
the supernate.

Step 3. Dissolve the precipitate from Step 2 in 1 ml of 3M HC1 and dilute
with Hzo to half the volume of the tube. Add conc. NHhOH to precipitate the

hydroxide, centrifuge, and discerd the supernate.

Step L. Dissolve the precipitate from Step 3 in about 5 ml of 3M HCl.
If there is a very heavy precipitate of FE(OE)3, it may be necessary to add
more 3M HCl to obtain complete solution. Again ignore a small residue of SiOz.

Prepare a column 0.6 cm in diameter and eabout 7 cm in height filled with
AG 50-X4, 50-100 mesh resin. Pour the HC1l solution onto the top of the resin
and allow to run through by gravity. Wesh the column with 10 ml of 3M HC1l and
discard both the wash and the firset effluent. Put a 50-ml Erlenmeyer contain-
ing 1 ml each of conec. HCth and HN03 under the column and add 3.5 ml of O.5M
15[20201\L to the top and gllow this to pass through by gravity.

Step 5. Evaporate the solution from Step 4 to dense white fumes and con-
tinue heating for about a minute. |

La
PROCEDURE 9 (Cont'd.)

Step 6. Transfer the solution to a 40-ml long-taper centrifuge tube and
rinse the contents of the flask into it with 2 ml of comc. HCl. Add 2 to 3
drops of 0.5M NaBr03 and saturate wlth HC1l gas whlle the tube i1s surrounded
by water at room tempersture. Prepare a wash solution by adding a few drops
of NaBr03 to conc. HC1l and saturate it at the same time.

Step 7. Prepare two colummns for each sample. The diameter of each column
is 0.6 cm and each 1s filled to a height of ebout 7 cm '-r.Lth AG 1-X8 or AG 1-X10,
100-200 mesh resin. Add the Bolutio:; from Step 6 to the top of one of the
columns and collect the effluent 1n a dry centrifuge tube. Rinse the origipal
tube and columm with about 1.0 to 1.5 ml of the wash solution prepared in Step
6. Combine this wash with the effluent end pass through the second column.
Rinse thie in the same manner as the firat and collect the combined effluents
in a 50-ml Erlenmeyer. It may be desirable to use very light air pressure to
push the solution through these two columns.

' Step 8. Evaporate the solution from Step 7 to 2 to 3 ml and add 1 ml of
conc, J:INO3 and 0.5 ml of conc. HIJJ.OL, and continue heating until dense white
- fumes mve been evolved for about a minute. Cool and add 2 ml of water.

Step 9. Prepare a column 0.35 cm by sbout 7 cm filled with 100-200 mesh
AG 50-X} resin. Pour the solution from Step 8 on the top of the column and
force it through with light pressure (2 to 3 1b). Wash the columm with 4.5
ml of 6M HC1 and discard this wash and the first effluent, Add 0.3 to 0.k
ml of Q.5M Hzczoh and push down _the column with very slight pressure. Make
sure that the leading edge of the oxalic acid band does not get to the bottom
of the resin and get discarded wlth.the other effluent. Add 0.7 ml of O,.5M
HZCZOlL to the top of the column and collect the sample on a 5-ml Pt plate.

If it is for alpha counting only, use a 1-3/h" to 2" diameter plate. If beta
counting is to be performed also, the sample is collected on a 1" diameter
plate. The sampleée ere dried under heat lamps and are left there untll most
of the Hzczoh is sublimed. Then they are heated to red heat in a flame.

SB. Thorium Procedure for Coral or Limestone Samples

Step 1. Dissolve 100 to 125 g of coral (accurately weighed) in 250 ml of
conc. ]5|1!03 and make up to 500 ml with HZO. This gives a solution contalning
about 0.2 g of coral per ml. '

Step 2. Add a 50 ml allquot of the well-mixed solution to a 90-ml cen-
trifuge tube together with 1 ml of Thzah (see Section 5C) tracer solution end
1 ml of Fe carrier. Stir and heat in hot water bath for an hour; then cool (Fote 1).

Step 3. Add cone. NH)OH slowly with stirring until IE':.E(‘.'J.E)3 precipitates
and then centrifuge for 5 minutes (Note 2).

42
PROCEDURE 9 (Cont'd.)

Step 4. Decant and dissolve the precipitate inm 5 ml of come. HN03,
dilute with H20, and again precipitate Fe(OE)3 with conme. RHhO .

Step 5. Centrifuge, decant, and dissolve the precipitate in 5 1 of
conc. HN03’ and with HZO wash the solution into a Pt dish. Add 10 ml of conc.
H \h and 5 m! of conc. HF.

Step 6. Take to fumes of HDth three times, washing the sides of the dish
with water after esch fuming (Note 3).

Step 7. Dilute the HCth solution to gbout 25 ml with HZO'

Step 8. The first columm (4 x 150 mm with 40-ml reservoir) is filled with
an AG 50-X4, 200-400 mesh resin-water mixture and packed to about 120 mm. Wash
the resin with 3M HCth and add the solution from Step 7. Allow to flow at
atmospheric pressure or adjJust the pressure to give a flow of about one drop
every 30 sec. | .

Step 9. When the solution reaches the resin, add 3M HCL acid in several
l-ml portions, washing down the sides of the columm. Continue until the ferric
chloride color disappears.

Step 10. Elute the Th with 0.5M H,C,0, (2 to 3 m1), catching the effluent
in a centrifuge tube. Add to the HZCZO,l solution 5 ml of comnc. HN03 and 5 ml
of conc. H.ClOl+ and teke to fumes of HCth three times, washing the beaker down
with H O after each fuming (Note 3).

Step 11. Add the solutlon, diluted with EZO to 12 ml, to the second
colum (2 x 150 mm with a 15-ml reservoir) packed to & length of 120 mm with
the seme resin and treated s in SBtep 8. Adjust the flow rate as in Step 8 also.

Step 12. When the solution reaches the level of the resin, wash with
five 1-ml portions of 3M HCl, rinsing the sides of the centrifuge tube with
each portion. : '

Step 13. Elute the Th with 0.5M Hzczoh, collecting the first ten drops
of EZCZOh acid effluent on a Pt plate. (The first few drops which are HCl are
not collected.) Evmporate to dryness under a heat lamp, and flame.

Step 14. Count Th23h to determine the yleld and pulse-snalyze the alpha
radiation (Notes L =snd 5), —

Additional Reagents and EBquipment for this section are:

Dowex 50-X4, 200-400 mesh
Resin columns - 4 x 150 mm with a 40-ml reservolr
2 x 150 mm with 3 15-ml reservoir

Rotes

1. The phosphate, chloride, and other impurities in the coral and the
high acid concentration seem to take the thorium into a completely exchangeeble
form. '

43
PROCEDURE 9 (Cont'd.)

2. Large quantities of phosphate increase [Ca3(POh)2] is precipitated
along with Fe(OE)3 end lead to a decrease in yleld due to the formation of
phosphate complexes of thorium. .

3. The solution 1s fumed three times to be sure no fluoride or oxmlate
18 there to Interfere 1n separation.

4. The isotopic thorium composition 1s calculated from the growth and
decay of alpha activity.

5. The yleld for this procedure variles from 50 to 90%.

5C. Isoclation of Thorium Decay Products from
Large ‘@Quantitles of Uranlum Parent

 

23

and Th23h
decay. For preparation of tracer using either of these thorium lsotopes, the
final step is an AG 50-X4 cation exchange column as in the determination of
comnting efficiency of Tho3* or Th23* under Section 4, except that the Pinal
oxalic acid effluent is fumed nearly to Aryness ?1th 1l ml each of conc. HEO3
and HCth. If an emount of uranium up to ebout a gram 1s sufficient to supply
the amount of tracer needed, the AG 50-Xk column can be used as in Sectiom &,
except that the final oxalic acid effluent is fumed nearly to dryness with 1
ml each of conc. EHO3 and BCth.
1s sufficient to supply the amount of tracer needed, the AG 50-X4 column can
be ueed ae in Section 4. B8ources of Th23l or Th23h can be milked from a 'cow'

of the appropriate uranium isotope asdsorbed on an AG 1-X8 column., The uranium

1s isoleted from a solution of oralloy, approximately 93.5% U235,
is obtained from normal urenium end the Th231 present allowed to

"If an amount of uranium up to about a gram

is dissolved 1n conc. HCl, and some oxlidizing agent such as bromate ion or bro-
mine water or chlorine gas 18 used to oxldize the uranium to U(VI). The
golution is then saturated with HCl gas at room temperature and adsorbed on
an AG 1-X8 column.

For 10 g of uranium a colum aout 25 mm 1n dlameter and holding 150 to
200 ml of resin bed is satisfactory. The resin is pre-washed with conc. HCl
containing about 0.5 ml of 2M laIBrO3 per 100 ml of acid. The uranium solution
is pareed through the column and thén re-cycled two or three times to get more
of i, adsorbed. Then the column is washed with about twice the resin bed
volume of conc. HC1l containing a drop or two of the bromate solution. After
a sultable growth time for the thorium daughter, the colfimn is treated with
conc., HC1 as above. The solution is evaporated to a small volume, fumed with
1l ml each of conec. HR03 and ECth and treated with an AG 50-X4 colum as in
Section 4. A Th23l source reading over 1 roentgen was prepared from 2 kg of

oralloy as follows: the uranium metsl was dissclved in an excess of conc.

4
PROCEDURE 9 (Cont'd.)

HNO3 and this solution was evaporated until the temperature became constant
at about 118°.

This is the boiling point of WO (NO ) - 6H 0. This solution freezes at
about 60 , 80 1t can be cooled to 70 to 800 and the molten hexmhydrate poured
into a 5-liter separatory funnel containing about 3 to L4 liters of diethyl
ether that is being rapidl& stirred with an air-driven stirrer. This must
be done in a good hood with explosion-proof fixtures, or out of doors. As
long es the molten hexahydrate is added in a slow stream to the ether with
good stirring, ‘the operation is perfectly safe and the ether losses are rnot too
large, since the vapor pressure of the ether decreases rapidly as the uranium
is dissolved. It 18 a far-mdre rapld and easler operation to add the molten
hexahydrate than it 1s to c 'ystallize it and &d4d the crystals. The final
golution in ether from the 2 kg of oralloy should have a volume of sbout L
liters. An aqueous layer of about 600 ml is withdrawn. The ether solution is
scrubbed with three 3-ml ‘portions of H_ O to insure complete removel of any
thorium that might be present. Tthl is allowed to grow for 1 to 2 days and
then 1s removed with three 3-ml portions of HEO' This aqueo':: layer is shaken
with two 200-ml portions of ether to remove more of the uranium. The
residual water layer 1s first evaporated on a steam bath to remove ethér, then
fumed with 1 ml each of conc. ENO3 and ECth and the AG 50-X4 column used as in
Section 4 except that the column dimensions are 0.2 cm x 5 cm. The bulk of the
Th231 can be followed down the column with a beta-gamms survey meter and over
80% of it is usually concentrated in 2 to 3 drops. The oxalic acld effluent
is placed in small drops on & 10-ml Pt wire about 1.5 in long and the wire
gradually heated to red heat by applying e current, controlled by a Vériac.

In this way the oxalic acid is completely volatilized, leaving a nearly mass-
free depoeit of Th23l. The ether 'cow' of uraenium can be kept over s eeverail
week period for the preparation of & number cf éanples.

PROCEDURE 10
Source - R.J. Prestwood in "Collecdted Radiochemical Procedures"”
Los Alamos Report LA-172l. Jan. 1958
l. Introduction

In the separation of thorium from large amounts of fission products
(1015 fissions or more), four principal decontamination steps are employed:
(1) Th(IO )h precipitation gives separation from the rare earths.

(2) 'rh(c2 ) precipitation effects separation from zirconium.

45
PROCEDURE 10 (Cont'd.)

(3) Ion exchange from a concentrated (greater than 12M) hydrochlaric acid
solutlon on a Dowex A-1 anlon resin results in the adsorptiom of
zirconium, iron, neptunium, nlutonium (VI), and uranium (VI}, the
thorium passing through the column.

(4) Extraction of thorium from ¢ aluminum nitrate - nitric acid solution
by means of mesityl oxide ((cn'3)2 C =CH. - E - 033) glves excellent

deccontamination from the alkali and alkaline earth metal ions
(including radium), lantfianum, and cerium. This e: ‘raction is
lneffective for the separation ¢~ thorium from zorconium, plutonium
(VI), and uranium (VI), and gives only poor decontamination from
neptunium. |
Thorium is finally precipitated as the oxalate and ignited to the dloxide,
in which form it is mounted and weighed. The yleld is TO to 80%, and quadrup-
licate analyses can be carried out in approximately 8 hours.

2. Reaggnta

Th carrier: 10 mg Th/ml (See preparation and standardization of carrier).
Bi carrier: 10 mg 31/m1 (added as 31(:03) "5H,0 in dilute nno3)

La carrier: 10 mg La/ml (added as La(no3)3-sgzo in néo).

Zr carrier: 10 mg Zr/ml {added as purified.ZrOClz'Bflio in nzo).

HCl: conc.

HIO.: 1M (carefully filtered).

HC,0,: saturated solution (carefully filtered).
EHlI_OH: conc.

HCl: gas.

EBS: gas.

502: gas.

2.4M A1 (H03)3 in 1.2M 13103 (carefully filtered).
IC103: 80ligd.

Methanol: absolute.

Mesltyl oxlide: Eastman White Label.

3. Equipment
3team bath

Fisher burner
PROCEDURE 10 (Cont'd.)

Drying oven
Ignition furnace (900°)
Block for holding centrifuge tubes
Forceps
Mounting pletes
Ground-off Hirsch funnels
Filtef chimneys
Transfer pipets
Manifold for column pressure
60-ml separatory funnels (one per sample)
40-ml conical short taper centrifuge tubes: Pyrex 8320 (four per sample)
LO-ml conical long taper centrifuge tubes: Pyrex 8140 (one per sample)
2", 60° funnels
Stirring rods (5 mm glass rod)
Stirring rods (4 mm glass rod - hooked end)
10-ml hypodermlc syringes
Porcelsin crucibles: Coors 000 (one each per standardization ani sample)
No. 42 Whatman filter circles: 15/16" dlameter
No. 50 Whatman filter circles: 15/16" diameter - weighed
No. LO Whatman filter paper (9 cm)
Fo. 42 Whatman filter paper (9 cm)
Jon exchange column
3" x 5 mm tubing attached to bottom of 15 ml centrifuge tube

4 cm of Dowex A-1 anion resin, 10% cross-link (about 200 mesh).

The resin 1ls suppllied by Bio-Rad Labcratories, 800 Delaware, Berkeley,
California. The resin 1s stored as a slurry in water. To prepare the
ion exchange columm, plug the bottom with glass wool, then add the resin
slurry from a transfer pipet. Allow the resin to settle and withdraw
excess resin and liguii. It i1s important that the resin be added all at
once, and not by several additions of slurry, to avoid "channeling®™ down
the columm,

4. Preparation and Stendardization of €Carrier

If the purity of the thorium 1s known, the metal may be weighed out
directly as a primary standard. It is dlssclved on a steam bath in a small
excess of concentrated HIO3 In a Pt dish, with perlodic additions of small
amounts of O0.1M HF. If thorium nitrate is used as carrier, i1t is 8issolved in

about 0.00LM HNO, and filtered. To & 10.00 ml aliquot (four standaraizations

&7
PROCEDURE 10 (Cont'd.)

are usually carried out) of the carrier, 10 drops of cone. HCL are added and
the solution is boiled over a Fisher bturner, Four ml of staurated Hzczoh are
then added and the solution 1s bolled for 2 min. The thorlum oxalate pre-
cipitate is filtered through No. L2 Whatman filter peaper (9 cm) in a 2", 60°
funnel and washed with sbout 1 percent H2020h solution (the saturated sclution
18 diluted 1 to 10). The precipitate 1s transferred to a tared porcelain
crucible (Coors 000) and is carefully igrnited at 9000 for 1 hour. The carrier
1s weighed as ThOz.

5. Procedure

Btep 1. Into a LO-ml short taper centrifuge tube, pipet 2.0 ml of
standard Th carrler; add the fission product solution and 5 drops of La
carrier. Precipifate Th(OH)h by means of an excess of conc. REhOE, centri-
fuge, and discard the supernate.

Step 2. To the precipitate add 8 ml of conec. HNO3, 15 ml of HEO’ and 7
ml of 1M EIO3' Centrifuge the Th(103)h preclipitate and discard the supernate.
Wash the precipitate with 15 ml of a solution which is LM in HNO_. and 0.25M in
HIO

3
Centrifuge and discard the supernate.

Step 3. To the precipitate add 1 ml of canc. HCl and 5 drops of Zr hold-
back carrier. Heat with stirring over en open flame until the precipitate
dissolves and the solution bolls. Dilute to 5 ml and bubble in SOz &a8 until
the solution becomes essentially colorless. Dilute to 10 ml and boil until the
solution is water white. Add 4 ml of saturated HZCZOL soluticon and continue
bolling for about 1 min. Centrifuge the oxalate precipitate and discard the
supernate.

Step 4. To the precipitete add 1 ml of conc. HIIO3 end about 100 mg of
solid KClOS. Heat cautiously to bolling to destroy oxmlate. Dilute to 15 ml

and precipitate Th(OH)h by means of an excess of conc. NH,OH. Centrifuge and

3

discard the supernate.

Step 5. Add 10 drops of conc. HCl to the precipitate and bubble in HCL
gas through a transfer plpet until the solution 1s saturated. With the aid of
a8 hypodermic syringe and the same pipet, transfer the solution (which hae a
volume of epproximately 1 ml) onto a Dowex A-1 anion reein (10% cross-link)
column (Before uae,'the resin column is treated with a
wash solution made up by adding 1 drop of come. HRO3 (Note 1) to 20 ml of conc
HCl end saturating with HCl gas at room temperature.) By mesns of air
pressure , force the eample solution through the columm in
approx;mately 3 min, but do not ellow the meniscus tc go below the top of the
resin. The effluent 1s collected in a 40-ml short taper centrifuge tube. Add

48
PROCEDURE 10 (Cont'd.)

1l ml of the resin wash solution to the original centrifuge tube and transfer
the washings by means of the same pipet onto the column. The vashings are
forced through the column in the same manner as the semple solutiofi, and are
collected along with the sample solution. This wesh - ¥y be rep- *ed.

Step 6. Dilute the collected samp.. plus washes to ap~—oximately 25 ml
and make the solution basiec with conc. NH&OE. Centrifuge the Th(OE)h precipi-
tate end discard the supermnate.

Step 7. Dissolve the precipitate with 6 drops of M E ‘3. Use 10 ml of
2. M Al(N03)3 - 1.5M HNO3 mixture (hereafter called the extraction mixture) to
transfer the sample solution to a 60-ml separatory funnel. Add 10 ml of
mesityl oxide to the separfitory funnel , shake for 15-20 sec, and discard the
water (lower) layer. Wash the mesityl oxide layer twice with 5-ml portions of
extraction mixture, discarding each washing. Back-extract the thorium with two
5-ml washes of distilled EZO’ collecting both'EZO layers ;n a 40-ml short taper
centrifuge tube. Dilute to 15 ml and add 8 m of conc. HR03 and 7 ml of 1M HIO
(Note 2). Centrifuge the Th(IO3)h precipitete and wash as in Step 2.

Step 8. Repeat Steps 3, 4, 5, and 6.

Step 9. To the Th(OE)h precipitate, add 5 drops if Bl carrier amnd 10
drops of conc, stoh' Dilute to 10 ml and saturate the solution with st.
Filter through a No. kO Whatman filter paper (9 cm) in a 2", 60° funnel,
collecting the filtrate 1n a 40-ml short taper centrifuge tube. Wash the pre-
cipitate with a small emount of water and combine the wash with the filltrate;
discard the precipitate. Make the filtrate basic with conec. NHhOH, centrifuge,
and dlscard the supernate.

Step 10. Repeat Step 7.

Step llf Repeat Step 3, but do not add Zr holdback carrier and do ndt
centrifuge the oxalate precipitate.

Step 12. Filter the hot solutlon containing the oxalate precipitate onto
a 15/16" Ko. 42 Whatman filter circle, using a ground-Hirsch funnel and filter
chimney (see illustration 2). Wash the precipitate with 1% Hzczoh solutlon.
Transfer the filter paper by means of forcepe to a Coors 0O0Q porcelaln crucible
and ignite for 15-20 min at 900°.

Step 13. Tranmsfer the Thoz to a dry Lo-ml long taper centrifuge tube.
(This is readily done by holding the edge of the cruciblée with forceps and
dumping the contents Into the centrifuge tube. TLittle or no 'I'hO2 edheres to
the crucible.) Grind the ThO,, Witk a 5 mm fire polished glass stirring rod;
6dd 1 ml of absolute methanol end continue grinding until the sclld is very
fine. Add an additional 10 ml of methanol and suspend the solid by vigorous
swirling. Transfer onto a tared No. 50 Whatman filter circle (15/16" diameter)

3

k9
PROCEDURE 10 (Cont'd.)

in the regular filter chimney setup. Apply suction until the_fiethanol has
passed through the filter circle. Remove the circle, dry in an oven at 115o
for 10 min, place in the balance case for 20 min, and welgh. Mount the sample
on two-sided Scotch tape which is stuck to an Al plate. Cover the sample with
Nylon £ilm (1.5 mg/cmz).

Notes

l. The purpose of the HN03 1s to maintain an oxidizing medium on the
resin to prevent reduction of Pu(VI). _

2. At this point the solution will be somewhat colored as a result of
oxlidation of dissclved mesityl oxide. This, however, does not affect the
results.

6. P-Counting of Th
Whenever Th B activities such as isctopes 231, 233, and 234 are cbunted
and Th232 is used as carrier, one 1s faced with the problem of the growth of pB
activities from the carrier. Examination of the decay chein of Th232 shows
that the amount of p actlivity depends upon the quantity of Th228 present. In

the chain the longest lived parent of Th228 (half-1ife 1.9 y) is Razze

the

’

half-life of which is 6.7 y. Thus, the amount of Th228 present in 232 depends

upon the time of separation of 35228. The B emltters succeeding Th228 grow in
224

essentially with the half-1ife of Ra which 1s 3.64 4. Therefore, the B
actlvity that one observes from natural Th which has had all of 1ts decay
products chemically removed grows im with a 3.64 d half-life. One mg of
natural Th in equilibrium with its decay producte has 494 disintegretions per
minute ° B activity. Since cne does not usually know the history of the Th
used as carrier, the moest convenient way to correct for these coun.. is the
fo' owing:

Pipet out as much carrier solution as will glve approximateiy the same
welght ae & true semple would when carried through the whole separation
procedure. Perform Steps 9 through 13 of the procedure. Note the time
of the laest mesliyl nxlide "msh of Step 10. After the sample is mounted,
count 1t every few hours over & period of several days. It 1s convenient
to use the time of he last mesityl oxlde wash as t . In thls manner, one
can correct for the growth of betas from the carrier.
The counting of 'I'hz31 is rather 3ifficult because of 1its weak B radiastilons
[0.302 (u4%), 0.216 (11%), 0.09% (L45%)]. This. isotope has nine y-rays ranging
in energy from 0.022 to 0.230 Mev. Since the efficiency of y-counting, even
with 1 in. Nal crystals, 1s quite low, one usumlly counts the betas. This means
that extreme care must be taken to insure uniform thickness of samples. Th233

and Thzah do not present such difficulty. The former has a 1.23 Mev p and decaye

20
PROCEDURE 10 (Cont'd.)

to Pa”J> which has a 0.530 Mev B. The latter, although it has weak radiations,
decays into Pa23h (1.175 m) which has a very strong B.

7. Absclute B-Counting of Some Th Isotopes

The relation between counts and disintegrations for thorium isotopes of
mass numbers 231, 233, and 234 can be cbtained from UE35, Np237, and U238,
235 238

respectively. If a weighed quantity of U or U is taken, Th carrier added,
and a chemical separation of Th made, one can calculate in each case the number
of Th disintegrations present. By counting the sample and correcting for decay
from time of separgtion, one has a direct relationship between counts and dis-
integrations. The self-absorption of the sample can be taken into account by
the use of this technique on several different weights of Th carrier with
identical specific activity. for example, one adds 100 mg of Th carrier to a
weighed amount of either U235 or U238, mixes the solution thoroughly, takes
several aliquots of different sizes, and separates the thorium. In this way, one
can plot a curve of sample weight vs disintegrations.

In the case of Th233 the sltuation is somewhat different. The decay
product of this isctope is P3233} which is also the immediate decay product
of Np237. By separating Pa233 from a known weight of Np237 and counting the
former, one has a direct relationship for PBZSS of counts vs disintegratioms.
For a sample of Th.233 one takes twe known aliquots, differing by a factor of
about 1000 in activity. (The ratio of Pa’33 to Th23S half-lives if 1693.5.)
The wesker aliquot is counted for Th233 immediately upon separation of Pa.
The stronger one is permitted to decay until it is all P3233 and is then
counted. From the previous (Np237) calibration one then can find the disin-
tegrations of Pa233 for this sample. The sample is corrected for decay back to
the time the weaker sample was counted for Th233, thus obtaining the number of

atoms of the latter when the sliquot correction is made.

PROCEDURE 11

Source - G.A. Cowan in "Collected Radiochemical Procedures”
Los Alamos Report LA-1721. Jan. 1958

Preparation of Carrier-Free UXi(Th23h) Tracer

1. Introduction

In the separation of le(Th23”) from uranium, the latter, originally
present in the form of UOZ(NO3)2, is converted to a soluble uranyl carbonate

complex by meaps of ammonium carbonate solution. Then at pH 8.0-8.5 the cup-

51
PROCEDURE 11 (Cont'd.)

ferrate of uxl is made and separated from the uranium by extraction into
chloroform. The UI_L is back-extracted into dilute nitrie acild contalning
bromine which serves to decompose the le cupferrate, thus allowing extractlon
of all the organic material and excess bromine int the chloroform phase,

2. Reagents

z(15103)2: 1 g U ml. (Added as 1_1308 or 1102(1!03)2.6320 in dllute msoa).

BN03: 3IM _

(NEH)ZCOB: saturated aqueous solution

]3:|:'2 wvater: saturated solution : , .
Cupferron: &b agueous solution (freshly prepared and kept in refrigerator)
Chloroform: c.p.

Hydrion paper (short range)

3. Bguipment
250-ml. beakers (2 per sample)
250-ml. separator funnels (3 per sample)
Volumetric flask: appropriate size (1 per sample)
Plpeta: assorted slzes
1" cover glasses
Heat lamp

4., Procedure

Step 1. Pipet 10 ml. of uoa(uo3)2 solution into a 250 ml. besker and
treat with saturated -(mik)aco3 solution end H,0 until the yellow precipitate
vhich first forms dissclves. Sufficient (mh°z°°3 1s added to meke the final
pH of the eolution 8.0-8.5 (Fote 1). '

Step 2. Transfer the solution to a 250-ml. separatory funnel, anl add
1-2 ml. of 6% aquecus cupferron reagent and 10 ml. of chloroform. Shake well .
and transfer the chloroform layer containing the Ull To a clean separatory
funnel. Repeat the chloroform extraction and combine the extracts.

Step 3. Wash the chloroform extracts with 20 ml. of 1120 to which has been
added 1 ml. of cupferron reagent and sufficlent (nx[h)zco3 solution to make the
pH 8.0-8.5. Transfer the chloroform phase to a clean separetory funnel.

Step 4. To the chloroform phase add 10 ml. of 3M B‘.l03 and a few ml. of
saturated B:L-2 water and shake. Discard the chloroform phase and waah the
agueous phage twice with chloroform, discarding the washings. Transfer to a

250-ml. besker and boil for a minute to remove the last traces of chloroform.

52
PROCEDURE 11 (Cont'd.)

Transfer the solution to a volumetric flask of the appropriate size and make
up to volume with HZO°

Step 5. Pipet aliquots of solution to 1" cover glasses and evaporate
t0 dryness under a heat lamp. Count, '

Rotes

1. A pH of 8.0-8.5 appears to be the optimum for the preparation and
gxtraction of the le cupferrate, although a pH in the range 7-8.5 1s suitable.

PROCEDURE 12

Precipitation Procedure for the PTeparatiai of Thorlum Free of its
Disintegration Products. N.E. Ballou et al. Paper 225 in "Radlochemical
Studies; The Fission Products" edited by C.D. Coryell and N. Sugarman,
McGraw-Hill Book Co., Inc. New York, 1951.

"o a solution of approximately LOO g of Th(NDB)h.hHEO one gram each of
barium and lead (as the nitrates) was added and precipitated with an exactly
equivalent quantity of stoh. This operation which removes the radium isctopes
NBThl and ThX and the lead 1sotope ThB, was repeated; after the barium and lead
preclpitates were flltered and discarded, 1 gram of lanthanum (as the nitrate)
was added to the filtrate. About 3 liters of comc. (HHh)zCO solution was asdded;
this precipitated the lanthanum and converted the
thorium intoc a soluble carbonate complex. Lanthanum was precipltated from the

3

solution twice more by adding one gram portions of lanthanum. These precipi-
tates, which remove the actiaum isctope MsTh2 (Hhoseichemistry is gquite similar
to that of lanthanum), were separated from the solution by centrifugation.

The purified thorium was then precipitated as the basic carbonate, ThOCOfi.xHBO,

by the addition of about TOC ml of conmec. EHO3 and was filtered and dried.”

FROCEDURE 13

Zirconium Iodate as a Carrier for the Removal of Tracer Thorium from
Rare Earths. N.E. Ballou. Paper 292 in "Radiochemicsl Btudies; The Fission
Products” edited by C.D. Coryell and K. Sugarmen, McGraw-Eill Book Co., Inc.
Nev Yark, 1951. Procedure originally formulated in 1943.

The starting solution contains a mixture of the flssion producte of
. uranium and severasl millig-ams of rare-earth cerriers including Cerium(IIT).
A mixed rare earth fluoride precipitate 1s formea oy the addition of 4M HF to

53
PROCEDUHE 13 (Cont'd.)

a 24 3103 solution of the activities. Tracer thorium coprecipitates The fluo-
ride precipltate is dissolved in canc. E!D3 saturated 53m . XC10,_ is added
and the solution is heated to oxidize cerium to cerium(IV). Add 20 ml 0.35M
E[Oa to precipitate Ce(IOa)L (vhich coprecipitates thorium). Diesolve the
Ce(IOa)h in comc. no3 plus one drop of 30 percent H,0,. Add 5 miliigrams of
lenthanum carrier and 2 grams of xc103 and reprecipitate Ce(IOa)h_. Dissolve
the precipitate in 5 ml of conc. ma plus 1 drop of 30 percent 5202. Add 5
milligrams of zirconlum carrier and 20 ml of O.35M HIO3 s cool in ice and
centrifuge to remove the precipitate of !'.r(IOa) j+ Thorlum tracer coprecipitates
quantitatively. Cerium (et this point in the III state) 1s decontaminated by
a factor of 200. For additional decontamination the Er(IOa)h can be dissolved
in s mixture of hydrochlorlc acid and sulfur dioxide and the zirconium
reprecipitated with naznroh.

PROCEDURE 1k

Source - L. Winsberg and J. A. Seiler. Paper 309 in "Radiochemical Btudies:
The Fission Products" edited by C.D. Coryell and N. Sugarman, McGraw-Hill Book
Co., Inc. New York, 1959. Original report written in 19L3.

1l. Introductiom

The older procedure for the determination of mhzal‘(‘uxi) activity in
fission meterial depended cn the separation of ThZ3" with the rare-earth
fraction and on a later removal with thorium carrier. The procedure
deac:r_i‘bed here_is much improved and shortened.

Thorium is used as a carrler for its lsctope UX,. Thorium iodate, together
with zirconium activity, precipitates from a come. Ema solution on the addition
of 3103 , but the other fission products, including the trivalent rare earths
(cerium 1s present in the reduced state), remain in solution. Thorium is then
precipitéted as the oxnlate from a solution containing zirconium holdback
carrier. Xrconium remains in salution as the soluble oxnlate complex. The

thorium oxalate is ignited to the oxide, mounted, and counted for UI_L activity.

2. Procedure

Btep 1. To an appropriate amount of uwanyl nitrate in a 50-ml centrifuge
tube, add a known amount of thorium carrier (about 20 mg) and 10 mg each of
cerium(IIT), lenthanum, and yttrium carriers (Note). Add 8 ml of canc. EIJB,
varm on a steam bath, and stir 2u ml of 0.35M HIO3 into the solution. Recard
the time of precipitation. The mixture is cooled in an ice bath with stirring.

>4
PROCEDURE 14 (Cont'd.)

The Th(IO3))_L precipitate (containing UX, and zirconium activity) is
centrifuged and washed twice with 2- to 10-ml portions of a mixture of 4 mi
of conc. HNO3 and 10 ml of 0.35M HIO3.

Step 2. The Th(}:o3)lL precipitate is dissolved in 5 ml of conc. HCL, and
1C mg each of cerium(III), lanthanum, and yttr... carriers and 10 +- 5 ml of
HZO are added. The centrifuge tube is placed * . ice bath, and SO2 is passed
in to reduce the IOg to I  and to maintain the cerium in the Ce(III) state.

The sclution should be clear after treatment with SO2 fo several minutes. The
solution is made alkaline with conec. NHAOH, and an excess is added. The
hydroxides are centrifuged and washed twice with H20 to which a small amount of
NHhOH has been added.

Step 3. The hydroxides are dissolved in 8 ml of conc. HNO_, and an iodate
separation is carried out as described in step 1. The Th(IO )h so cobtained is
dissolved in 5 ml of conc. HCl, the 103 is destroyed with SOZ’ and the thorium
is precipitated as the hydroxide, as described in step 2.

Step Yy, The washed thorium (UXl) hydroxide, which still contains zirconium
activity, is dissolved ir 6N HCl; 10 mg of zirconium carrier is sdded (Note);
and the solution is diluted to 10 ml. Ten milliliters of hot saturated oxalic
acid solution is added to the hot solution with stirring. The Th(czoh)2 pre-
cipitate is centrifuged and washed twice with a 1 percent oxalic acid sclution.
One gram of KClO3
carefully for a few minutes until gas evolution ceases. The solution is
diluted to 10 to 15 ml, and Th(on)J+ is precipitated with conc. NHhQH and washed
twice with H20 to which & small amount of NHhOH has been added. .

Step 5. The hydroxide is dlssolved ir 6N HCl, 10 mg of zirconium carrier
is added, and the solution is diluted tc 10 ml and heated in a steam bath.

and 3 ml of conc. HN03 are added, and the solution is heated

Ten milliliters of hot saturated oxalic acid solution is added to the hot
solution with stirring. The 'l‘h(CZOM)2 precipitate is centrifuged and washed
twice with a 1 percent oxalice acid sclution. The precipitate is then

suspended in 20 ml of H_.O containing 0.5 ml of &N HC1l and a small amount of

2
macerated filter paper. The Th(CZOu)z precipitate is collected on an ashless
filter paper in a small Hirsch funnel. The paper and the precipitate are

transferred to a crucible, the precipitate is ignited to ThO_, and a weighed

2
sample of the oxide is mounted for counting.

Note

The carriers are prepared as slightly acidic solutions of the nitrates.

2>
PROCEDURE 14 (Cont'd.)
'3. Discussion

Thie method was tested by analyzing both unirradiated and neutran-
1rradiated uranyl nitrate for Ufli._ The two analyses gave identical mctivities
and absorption curves; thls indicated that Ull i1s obtained radiochemically
pure by the above procedure. In the analysls of solutioms of high fission activity
it may be necessary to repeat the thorium iodate and thorium oxalate precipitation

gseveral times.

PROCEDURE 15

Determination of Thzah(uml) Activity in the Presence of Uranium and Fission

Products. K.E. Ballou and D.N. Hume. Paper 310 in "Radiochemical Studies: The
Fission Products” edited by C.D. Coryell end N. Sugarman, McGraw-Hill Book Co.,
Inc., Rew York, 1951. It is based on report cn-i312 dated May 15, 1945.

l. Introduction

The precipitation of thorlum with HF and KF (prdbably as KzThF6) removes
Thzah (Uxi) from uranium and the fission products except the rare earths, zirco-
nium, and the alkaline earths. The addition of zirconium holdback carrier
markedly reduces the coprecipitation of zirconium. Large amounts of UO';+ cause
some UOZF2 to come down with the fluoride precipitawv.; this is re. 1y removed
by washing the precipitate with €M HF.

The golution of the thorium precipitate is accompliched by warming with
HNO_ and H,BO,. The precipitation of Th(OH), removes the alkaline-earth con-
tamination. Additional decontaminstion from all the fission products except
zirconium end niobium (columbium) is brought sbout by the precipitation of
.Th(IO3)h from & LM HN03 solution. The precipltation of thorium with oxmlic acid
serves as an additional separation from zirconium and niobium and also converts

the thorium to a welghable form.

2. DProcedure

Step 1. To 5 ml or less of uranium and fission-product ple in e
lusteroid tube, add 1 ml of conc. HROS, 20 mg of standard thorium carriler, and
10 mg of zirconium holdback carrier. Dilute to 20 ml and add 3 ml of conc. HF
end 3 ml of €M KF. Centrifuge, and wash with 5 to 10 ml of &M HF.

Step 2. Dissolve the precipitate with 2 ml of 6 percent H3BD3 and 2 ml of
cone. HRO3 (Fote 1}. Dilute to about 15 ml, add 5 mg of parium holdback carrier,
and precipitate with 3 to 4 ml of conc. NHMQE. Centrifuge, and wash with 20 ml

0.
of H2

56
PROCEDURE 15 (Cont'd.)

Step 3. Add-8 ml of conc. HNO3, 10 drops of 3 peréent HZOB, and 20 ml of
0.35M EIOB-to the precipitate. Cool; and let the Th(Io3)h precipitate . Jnd
for 5 min (Note 2). Centrifuge. and wash the precipitate with 10 ml of &
mixture of 3M HRO_ and 0.03M HIO..

Step 4. Dissolve the Th(103)h precipitate by the addition of 2 ml of conc.
HCl, dilute to about 20 ml, and pass in SOz.until the solutlon becomes color-
lees. Add 5 ml of conc. RE

Step'5. Dissolve the hydroxide precipitate in 8 ml of conc. HN03, and add
5 mg of Ce(III) carrier, 0.5 ml of 3 percent 3202, and 20 ml of 0.35H'H103.
Cool, and let the Th(103)4 precipitate stand for 5 min. Centrifuge, and wash
with 10 ml of 0.035H.HIO3. Add 2 ml of conc. HC1l to the precipitate, dilute to
20 ml, and pass SOZ into the solutlon untll it 1s colcorless. Precipitate
Th(OE)h by the addition of 5 ml of conc. RE,OH, and centrifuge and wash the
precipltate with about 20 ml of EZO'

8tep 6. Dissolve the precipitate in 1 ml of 6N HC1l, add 15 ml of Ezo,
heat the solution to bolling, and add 15 ml of sat. H,C,0,. Coal the Th(czoh)2
precipitate in an ice bath for 10 min, and filter it on a weilghed filter-paper
disk. Wash with alcohol and ether, and use the same technique for drying and
weilghing as in the rare-earth procedures (Note 3). Count without excessive
delay (Note &4).

hOH and centrifuge.

-Rbtes

1. Additianal H3BQ3 and BRO_ may be mnecessary if much lanthanum was
present in the original sample.

2. Hydrogen peroxide reducee cerium to the Ce(III) state, in which it is
not precipitated from strongly ecid solutions by IO.. '

3. The precipitate is welghed as Th(CZOL)z.BHZOn The carrier must be
standardized in the same manner.

k. The thorium precipitate should not be allowed to stand very long

before the activity measurements are made, since the p-actlive disintegration

3

products of thorium contribute an incregsingly larger fractlon of the total
activity with time.

3. Discussion

The procedure has been tested by using carrier-free tracers of cerium,
yttrium, rutheniufi, strontium, zirconium, and tellurium. The final thorium
oxalate precipitate was contamineted to the extent of 0.06 percent of the
grose added tracer activity. '

T
PROCEDURE 16

Isolation of Th229 from a mixture of 0233 and 1its decay products by means
of coprecipitation on Zr(IO3)lL and extraction with TTA. 8or—-= - Hagemsann and
co-worke=-, Phys. Rev. T9, 435 (1950).

One- to two-tenths of a milligram of zirconium nitrate end sufficient
lodic acid solution to give a final iodate cancentration of 0.05M were added
per milliliter of solution of U233 in O0.1N nitric acid. The precipitated
zirconium iodate was washed by centrifugation, dissolved in sulfur dioxide-
water, heated to remove llberated iodine, diluted, and the zirconium
reprecipitated with lodic acid. Four to five of these cycles served to de-
contaminate completely from urerium, radium, and most of the actinium. Bismuth
and lead actlvitles were removed by ome or two lead sulfide by-product
preclpitates. '

In order to prepare samples sufficilently free from carrier for alpha-
particle range_méasuremefits in the pulse anelyzer, and to remove any traces of
actinium activity, the following procedure was used. The thorium isotopes were
co-preclpitated from the final zireonium iodate solutlon with lantlanum fluoride
carrier (0.1-0.2 mg/ml), the fluoride precipitate was metathesized to hydroxide
wlth concentrated potassium hydroxide and the hydroxide dissolved in 0.05M
nitric acid. Separation of the thorium activity from the lanthanum carrier was
accomplished by extraction with a solution of Q.15M thenoyl trifluoracetone
(TTA) in benzene. The change'frdm zirconium to lanthenum carrier was necessary
since the former extracte into TTA solution under the canditions used, whereas
the latter does not. In some cases, TTA extraction of the thorium i1sotopes was
made directly from the uranium solution. The TTA benzene solutlon was in either
case evaporated directly on the counting plate or reextracted with 8N nitric
acld and the latter solutiom evaporated. Ignition of the resulting ple .3 left
an essentially weightless film of the thorium activity.

PROCEDURE 17

Measurement of thorlum isctopes in sea water. Source - F.F. Koczy, E.
Piceciotto, G. Poulaert, and 5. Wilgain, Geochim. et Cosmochim Acta 11, 103-29
(1957); see also Nature 17L, 742 (1953).

Abstract

In order to study the geochemlstry of thorium lsotopes in the hydrosphere,
perticularly in the ocean, a method has been worked out by which Th232, Th23o,
Th228, an 22t can be determined separately. Eight samples of 20 to 40 liters

58
PROCEDURE 17 (Cont'd.)

of sea-water, from 23.0 fi to 34.97 % salinity, were collected in November
1953, in the Skagerak and the Gullmarfjord (Sweden). Thorium was isolated by
the following procedure: Just after collection, the samples were brought to pE
2 and a glven amount of Th23lL ( ) was added as tfacer, Thorium was first
precipltated with Fe(OH)3 as carrier. Further purification was obtailned by ion-
exchange column chrometogrephy followed by solvent extraction; the final
fraction was obtained as the cltric complex, a form suiteble to incorporstion

in the photographic emulsion. The total yield varied from i to 23% according

to the sample, as determined by the P activity of the tracer. The various Th
isotopes were measured through their @ activity, using nuclear photographic epul-
sions, more precisely the double-emulsion teéhnique. RdTh and RdAc both genersate
five-branched stars; more than 90% of these originated from RdTh, as indicated
by the length of the tracks: while Io and Th only yield single tracks of

range 18.8 p and 15 p respectively in the emulsion. Most samples showed a much
1+ :r activity than expected; this did not make it possible to discrimirnate
bétveen Io and Th through the range distribution of their tracks, thus we could
cnly ascertaln upper limits of Io and Th concentrations. '

PROCEDURE 18

Preparation of UX absolute p-counting standards. OSource - T.B. Rovey,
D.W. Engelkemeir, apd P.W. Levy. Paper 9, pp. 114-121 in "Radiochemical
Studies: The Fission Products"” edited by C.D. Coryell and K. Sugarman,
McGraw-Hill Book Co., Inc. 1951; report originally written in 1945,

UX Standard. Pure U308 more than 3 yr old was dissolved in acld to meke
a solution of sufficiently high concentration so that aliquots to glve m
desired activiiy were large enough to permit accurate pipetting. The uranium
concentration chosen was 4 mg/ml. Fifteen milliliters of this solution then
gave an activity of about 9,000 counts per minute (c/m) at the highest
geocmetry factor used. '

The uranium was precipitated from this volume with bese, and the pre-
cipitate was dissolved in 1 ml of acid solution and transferred to a 3-ml
lusteroid test tube. This transfer caused no detectable loss. Lanthanum
carrier (0.25 mg) was added and precipliteted with KF. The precipitate was
centrifuged out and washed twice with water. The supernatants were collected
and tested for UX loss by LaF
1l to 2 percent.

The first LBF3 precipitate was slurried with 10 pl of water, transferred
to a sheet of 0.2-mil aluminum weighing 1.4 mg/cmz, end evaporated to dryness

separation. The activity loss here was fisually

3

29
PROCEDURE 18 (Cont'd.)

vith an infrared lamp. The lusterold tube and the transfer pipet were rinsed
out with several 25-ul water washes, which were added to the rest of the
precipltate and dried. A drop of dilute Zapon lacquer was evaporated on top
of the precipitate. The lusteroid was then ashed, mounted; and counted. OCne
to two percent of the total activity usually remained in this residue.

The source then conslsted of about 0.5 mg of precipitate on an area of
0.4 cm2 mounted on thin aluminum. Thls sheet was attached with Scotch tape
over a l-in. hole in an aluminum éard of conventional size, 2-1/2 by 3-1/h by
1/32 in. Four standards were made this way; the total mctivity of any one
standard corrected for the €wo losses veried from the average by no more than
0.8 percent. '

PROCEDURE 19
Source .- G.R. Choppln and T. Slkkeland

Scheme for the Separatinn of the Elements Francium Through Uranium.

The separation is accomplished by three ion exchange column elutions, the
first two utilizing Dowex-1 gnd the third, Dowex-50.

Reaggnts

1 M FH,EF,, 0.5 M BF, 0.1 M EC1, 9 ¥ HC1, 0.1 M HC1-0.1 M EF, 9 M HC1-1 M FEF,
8 M HNO hnflnoy'analnmo :

3’ 3

Procedure

.l. Prepare the first anlon resin column by paesing the solution of NEfiHFz
through it to convert the resin to the fluoride form. A glass column which has
been coated with paraffin before addition of resin is used. The resin bed in
all three columns 3 mm x 5 cm. This of course is governed by the amount of
material to be sorbed. A flow rate of 1.5 minutes per drop is used.
(a) Load the sample in 1-2 drops of 0.1 M HCI1.
(b) Begln elution with 0.5 M HF. Fr elution occurs immediately
(first column volume).
(c) After 4 or 5 colum volumes, elute with 9 M HCl. Ra, Ac, and Th,
elute in next few column volumes.
(d) The third eluting solution 1s 9 M HCl-1 M HF which elutes Pa
immediately. '

(e) Finally U is removed by elution with O.1 M HC1-0.1 M HF.

60
PROCEDURE 19 (Cont'd.)

2. The second anion resin column is prepared by washing with 8 MZHN03.

(a) The Ra, Ac, Th fraction is loaded and eluted with 8 M HN03 for

several column volumes. Re and Ac elute immediately.
(p) 1 M HN03 is used as eluant to remove Th.
3. The cation resin column is prepared by passage of 4 M'HNOB.
(a) The Ra, Ac fraction is loaded and elution begun with L M Em03.
Ra is eluted.

(b) After elution of Ra, 8 M HNO, 1s used to bring off Ac.

3

Discussion

From the characteristics of the elutlon peeks from the fluoride columms,
it seems more likely that negative flucride complexes are sorbing rather than
that insoluble fluorides are precipltating in the resin. The behavior of Ra is
surprilsing as formation of a negative complex seems rather unlikély and Ban 1s
not particularly insoluble. It has been suggested that Ra may be coprecipitat-

ing with Can which is much more insoluble.

PROCEDURE 20

Radiochemical Determination of ITonium in Uranium Fluorination Ash
Source: F. L. Moore, Anal. Chem. 30, 1020 (1958)

- Introduction

Recent detectioufi‘ of iocnium (tl/z’ 8 x th years, 4.68 Mev alpha emitter)
in process solutions of uranium "ash" from various gaseous diffusion processes
pecessiteted an analytical method for the determination of this radiocactivity.
Many of the process solutlons contain aluminum, lron, stainless steel corrosion
products, fluoride, uranium-234 end -238, neptunium-237, and plutonium-239. The
present method (60) for the radiochemical determinaticn of the thorium
isotope, thorium-234 (le), in the presence of uranium and fission products. is
satisfactory, as the gamma radiocactivity may be counted efficlently in the
presence of the thorium carrier prescribed. However, a earrier-free method was
desired for the determination of ionlum to avoid self-absorptlon losses of the
alpha particles. The method for uml does not provide for the séparation of

neptunium and plutonium. A method for the determination of fonium in coral

61
PROCEDURE 20 (Cont'd.)

limeatone63 appears rather lengthy, because both enion and cation exchange steps
are necessary to eliminate the plutonium interferencea

The radiochemical method descrlbed gives satisfactory results on uranium
ash process solutions. Mbat interferences are eliminated by a combination of
lanthanum hydroxide and fluoriae_precipitations which carry the ionium quantita-
tively. Uranium, neptuniumiand:plntonium are .effectively eliminated by maintain;
ing them in the fluoride;soluble aexivalent oxldation state. The lanthanum
fluoride technique 1is an-adaptation of the famllier method‘aof carrying
plutonium (III IV) in the presence of plutonium (VI) Iron (III) forme e
fluoride soluble complex and is essentially eliminated in this step. A final
ert.raction6l of the ion-ium with C.5 M Z-thenoyltrifluoroacetone-:qvlene eliminates
the lanthanum. oarrier, increasea the selectivity, and provides a polld-free

plate for alpha counting

 

Procedure
Pipet a suitable aliquot of the sample aolution into & 5-ml Pyrex Brand
8060 centrifuge cone. Add 0. l ml of. lanthanum carrier (5 mg. per ml.) and mix
well with 8 platinnm stirrer | Adfl l ml. of 19 M sodlum hydroxide, mix well,
and digeat for 5 minutea_at room temperature. Centrifuge in e clinlicagl
centrifuge for 3'minutea. Remove the.aupernatant aolution with mild suction.
Wash the nrecipitate by stirring with 2 to_3 ml. of 0.05.5 sodium hydroxide.
Centrifuge for 3 minutes, remove the supernatant solution, and repeat the wash
step. |
Dissolve the precipitate 1n several drops of concentrated nitric acid and
"add 8 to 10 drops in excess. Add 0.3 ml. of O.4 M potassium dichromate, mix .
well, and digest for ld minutes In a beaker of water at approximately bolling
temperature.- Add 0.3_ml. of 2T M hydrofluoric acid, mix well, end digest at room
temperature for Sfminuteal' dentrifuge for 3 mlnutes. Add 0.05 ml. of
lanthanum carrier and atir the aupernatant solutlion, being careful not to dis-

turb the precipitate Digeat for 5 minutes at room temperature. Centrifuge
FROCEDURE 20 (Cont'd.)

for 3 minutes and carefully remove the supermatant solution, leaving sbout 1
drop. Wash the precipitaté by stirring with 0.5 ml. of 1 M hydrofluoric hcid-
1 M nitric acid containing 1 drop of 0.4 M potassium dichromate. Centrifuge for
3 minutes, remove the supernatant solution, and wash the precipltate with 0.5
ml. of 1 M hydrofluoric acid-1l M nitric acid.

Dissolve the lanthanum fluoride precipitate by adding 0.5 ml. of 2 M
aluminum nitrate and several drops of 1 M nitric acid. Cerefully transfer the

sclution to a 10-ml. beaker using several distillled water washes. AdJjust the

PH to 1.4 to 1.5 with a pH meter and extract for 10 minutes wilth a ope-half
volume portion of 0.5 M thenoyltrifluoroacetone-xylene. After centrifugation,
evaporate an aliquot of the organic phase on s platinum or stainlesgs steel
disk, fleme to a red heat, cocl to room temperature, and count in a proportional
alpha counter. An alpha energy analyzer is useful for occasionally checking the
disks, when pmall amounts of lonium are determined in the presence of high
levels of other aipha radloactlivities.

If radium, protactinium, americium, or curlum is not present, omit the final
extraction step. Blurry the lanthanum fluoride precipitate with several drops
of 1 M nltric acid and transfer quantitatively to a platlnum or stalnless steel
disk. Rinse the cone with three 3-drop portions of distilled water, transferring
the rinses to the disk. Dry under an 1lnfrared heat lamp, flame to a red heat,
and count the disk In a proporticnal alpha counter. .

The initial hydroxide precipitation nay.be cmitted 1f the sample solution

does not contain aluminum or chromium.

Discussion
The procedure described ylelds 97 3% on process solutions. Most losses
are in the pH adJustment prior to the final extraction. By rinsing the centri-
fuge cone with several distilled water washes before pH ad]Justment and by using
several portions of the organic phase to wash the beaker afterwvards, essentislly

quantitative recovery of ionium can be effected. Quadruplicate analysis of a

63 -
PROCEDURE 20 (Cont'd.)

dilute nitric acid solution conteilning 1.4 x 10°

alpba counts per minute per
milliliter of ionium gave 99.h, 98.0, 98.1, and 99.5% recovery, which is
satisfactory for a carrier-free technique. The radlochemist may desire tc apply
a8 yleld correction fér the ionium recovery, particularly if many chemical
separations are performed. The beta, gamma emitter, thorium-234 (le), is very
fiseful in such cases. |

' The major alpha radioacti#ity present in this particular process was
neptunium-237 along with much smaller amounts of plutonium-239 and uranium-234
and -238. Decontaminatipn from theée alpha emitters wae satisfactory. A
solutlon containing 2 x 105 alpha counts per minute per milliliter of neptunium-

h alpha counts per minute per milliliter of ionium was analyzal

237 and 5.6 x 10
by the prescribed procedure. An alpha energy analysis of the final plate
indicated pure ionium with no neptunium-237 detected. This analysls should be
performed occaslonally, if very low levels of lonium are being determined in the
presence of high concentrations of other aipha emitters.

Although radium, polonium, protactinium, americium, and curium were not
detected in solutions of this particular process, these elements are often present
in uranium wastes. Radium will be eliminated in the hydroxide precipitation and
traces that do carry will be elimipated verj effectively in the final extraction
of ionium.2 Deconéamination of ionlum from polonium was excellent: 0.02, 0.03,
0, 0.03, and 0.02% in five expériments. Solutions containing 7.6 x 10“ alpha
counts per minute per millilliter of polonium-zoa were analyzed using the ionium
procedure.' Analysis of the variofis separated fractions in the procedure
indicated that easentially all of the polonium was in the oxidized supernatant
solutian from the lanthanum fluoride precipitation. Thus, polonium behaves
like uranium, neptunium, and plutonium in the procedure. As quadrivalent
polonium readily carries on lanthanum flucride from nitric acld solutlon, the
polonium may be in the sexivalent fluorlde-soluble state in the presence of
potassium dichromate. Approximately 50% of the protactinium originally present

remained in the supernatant aolfition as a Ffluoride soluble complex upon the pre-

64
PROCEDURE 20 (Cont'd.)

cipitation of lanthanum fluoride. If protactinium-231 1s present, the lonium
should be stripped from the 0.5 M 2-thenoylfrifluoroacetone-xylene By etirring
with an equal volume of 2 M nitric acid for 5 minutes. Iocnium strips quantite-
tively, leaving the protactinium In the organic phese. Typlcd decontemination

. data for protactinium in four experiments (imcluding the final strip with 2 M
nitric acid) gave 0.03, b.ZO, 0.07, and 0.05%. A ZM nitric acid solution con-
taiging 6.5 x lO5 gamma counts per minute per milliliter of protactinium-233 was
analyzed 1n 1l-ml. aliqpota.br the lonlum procedure. The final 2 M nitric acid
gtrip solutlon was counted for protactinium-233 gamma redicactivity using e
scintillation counter having s sodium icdide crystel. Although 1t 1s rarely
necessary, the last traces of protactinium mey be removed by re-extracting the

2 M nitric acld strip solution with an equal volume of 0.5 M z—thenoyltrifluoro;
acetone-xylene for 5 minutes. Americium and curium ere readily eliminated elomg
with the lanthanpum carrier when the lonium 1s extracted with thls reagent.

The method should prove useful in the carrler-free isolation of thorium
isotopes. Although the procedure has been used specifically to determine lonium
in uranium flaorination ash, it should be useful for the determination of
ionium in various waters end rocks. Ionium may be isolated from compiex
mixtures of elemeqts by lanthanum hydroxide and fluoride carrying, followe. by
extraction with 2-thenoyltriflucroacetone-xylene. In analyzing materials con-
taining natural thorium, a final alpha energy anaslyslis should be performed to

differentiate lonlum from other thorium isotopes.

65-66
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69
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commmication.

Printad In the United States of Amarica
USDOE Technlcal Information Center, Ook Ridge, Tannsuss

TO
NUCLEAR SCIENCE SERIES: MONOGRAPHS ON RADIOCHEMISTRY
AND RADIOCHEMICAL TECHNIQUES

Available from the National Technical Information Service,
U. S. Department of Commerce, Springfield, Virginia 22161

ELEMENTS

Aluminum and Gallium, NAS-NS-3032 [1961],
$9.25

Americium and Curium, NAS-NS-3006 [1960],
$9.75 :

Antimony, NAS-NS-3033 [1961], $9.50

Arsenic, NAS-NS-3002 (Rev.) [1965], $9.00

Astatine, NAS-NS-3012 [1960], $8.75

Barium, Calcium, and Strontium, NAS-NS-
3010 [1960]. $11.00

Beryllium, NAS-NS-3013 [1960], $9.50

‘Bismuth, NAS-NS-3061 [1977], $11.75

Cadmium, NAS-NS-3001 [1960], $9.50

Carbon, Nitrogen, and Oxygen, NAS-NS-
3019 [1960), $8.50

Cesium, NAS-NS-3036 [1961], $9.75

Chromium, NAS-NS-3007 {Rev.) [1963], $9.50

Cobalt, NAS-NS-3041 [1961], $10.25

Copper, NAS-NS-3027 [1981], $9.60

Fluorine, Chlorine, Bromine, and ledine,
NAS-NS-3005 [1960], $9.25

Francium, NAS-NS-3003 [1960], $9.00

Germanium, NAS-NS-3043 [1961], $9.25

Gold, NAS-NS-3036 [1961], $9.00

Indium, NAS-NS-3014 [1960], $9.50

lodine, NAS-NS-3062 [1977], $11.00

Iridium, NAS-NS-3045 [1961], $8.75

Iron, NAS-NS-3017 [1960], $11.75

Lead, NAS-NS-3040 [1961], $12.00

Magnesium, NAS-NS-3024 [1961], $8.76

Manganese, NAS-NS-3018 (Rev.) [1971],
$9.75

Mercury, NAS-NS-3026 (Rev.) [1970Q], $13.00

Molybdenum, NAS-NS-3009 [1960], $9.00

Neptunium, NAS-NS-3060 [1974], $13.75

Nickel, NAS-NS-3051 [1961], $11.25

Niobium and Tantalum, NAS-NS-3039 [1961],
$9.50 '

Osmium, NAS-NS-3046 [1961]. $8.50

Palladium, NAS-NS-3052 [1961], $11.00

Phasphorus, NAS-NS-3056 [1962], $9.00

Platinum, NAS-NS-3044 [1961], $8.75

Plutonium, NAS-NS-3058 [1966], $12.75

Polonium, NAS-NS-3037 [1961), $9.76

Potassium, NAS-NS-3048 [1961], $9.26

Protactinium, NAS-NS-3016 [1959], $10.00

Radium, NAS-NS-3057 [1964], $13.26

Rare Eerths—Scandium, Yttrium, and
Actinium, NAS-NS-3020 [1961], $16.00

Rare Gases, NAS-N5-3025 [1960], $9.50

Recent Radiochemical Separation Procedures
for As, At, Be, Mg, Ni, Ru, and Se, NAS-NS-
3059 [1974], $10.25

Rhenium, NAS-NS-3028 [1961], $9.26

Rhodium, NAS-NS-3008 (Rev.) [1965]. $10.00

Aubidium, NAS-NS-3053 [1962], $10.25

Ruthenium, NAS-NS-3029 [1961], $10.00

Selenium, NAS-NS-3030 {Rev.) [1965], $9.50
Silicon, NAS-NS-3049 (Rev.) [1968], $10.00
Silver, NAS-NS-3047 [1961], $9.50

Sodium, NAS-NS-3055 [1962], $9.25

Sulfur, NAS-NS-3054 [1961], $9.50
Technetium, NAS-NS-3021 [1960], $9.50
Tellurium, NAS-NS-3038 [1960], $9.25
Thorium, NAS-NS-3004 [1960], $9.75

. Tin, NAS-NS-3023 [1960], $9.75

Titanium, NAS-NS-3034 (Rev.) [1971]. $10.26

Transcurium Elements, NAS-NS-3031 [1960),
$9.00 .

Tungsten, NAS-NS-3042 [1961], $9.25

Uranium, NAS-NS-3050 [1961], $17.00

Vanadium, NAS-NS-3022 [1960], $10.00

Zinc, NAS-NS-3015 [1980], $9.50

Zirconium and Hafnium, NAS-NS-3011 [1960],
$9.50

TECHNIQUES

Absolute Maasurement of Alpha Emission
and Spontaneous Fission, NAS-NS-3112
[1968], $9.75

Activation Analysis with Charged Particles, '
NAS-NS-3110 [1966], $9.25

Application of Distillation Techniques to
Radiochemical Separations, NAS-NS-3108
[1962],-$8.00

Applications of Computers to Nuclear and
Radiochemistry, NAS-NS-3107 [1962], $16.00

Cation-Exchange Techniques in Radio-
chemistry, NAS-NS-3113 [1971], $13.00

Chemical Yield Determinations in Redio-
chemistry, NAS-NS-3111 [1967], $10.50

Detection and Measurement of Nuclear
Radiation, NAS-NS-3105 [1961], $11.50

Liquid-Liquid Extraction with High-
Molecular-Weight Amines, NAS-NS5-3101
[1960], $10.25

Low-Level Rediochemical Separations,
NAS-NS-3103 [1981], $9.00

Neutron Activation Techniques for the Measlre-
ment of Trace Metals in Environmental
Samples, NAS-NS-3114 [1974], $10.26

Paper Chromatogrephic and Electromigration
Techniques in Radiochemistry, NAS-NS-
3106 [1962], $9.25

Processing of Counting Data, NAS-NS-3108
[1966], $12.25

Rapid Radiochemical Separations, NAS-NS-
3104 [1861], $11.26 :

Seperations by Solvant Extraction with
Tri-n-octylphosphine Oxide, NAS-NS-3102
[1961]}, $9.50 _

Users” Guides for Radioactivity Standards,
NAS-NS-3115 [1974], $10.26

Current as of January 1982