ORNL-CF-71-7-8.txt

L~

 

 

DATE:

SUBJECT:

TO:

FROM:

OAK RIDGE NATIONAL LABORATORY FTOR INTERNAI USE ONLY

OPERATED BY

 

UNION CARBIDE CORPORATION

NUCLEAR DIVISION 0 R N L
Lol

UNI
CARBIDE

| CENTRAL FILES NUMBER

OAK RIDGE, TENNESSEE 37830

7L - 7 - 38

 

 

 

July 7, 1971 COPY NO.

Additional Calculations of the Distribution of Tritium
in the MSRE

Distribution

R. B. Briggs

ABSTRACT

Some of the calculations reported in CF 70-T7-13
were repeated, taking into account recent information
on the solubility of hydrogen in molten salts and the
sorption of tritium by graphite. Reasonable agreement
was obtained between the measured and calculated distri-
butions of tritium in the MSRE. Additional experimental
data are needed to reduce the uncertainties in the
calculations.

Key Words: tritium, MSRE, fused salts, reactors,
operation.

NOTICE This document contains information of a preliminary nature
and was ogepared primarily for internal use at the Oak Ridge
Nationa? +-8bratory. It is subject to revision or correction and
therefore does not represent a final report. The information is
only for official use and no release to the public shall be made
without the approval of the Legal and Information Control Depart-
ment of Union Carbide Corporation, Nuclear Division.
ADDITIONAL CALCULATIONS OF THE DISTRIBUTION OF TRITIUM
IN THE MSRE

 

Results of calculations of the tritium distribution in the MSRE and
discussion of the methods used in the calculations were reported in CF
70-7-13, "Calculation of the Tritium Distribution in the MSRE." Since
the time of publication of those results, several changes have occurred:

1. Measurements by Malinauskas and Savolainen have indicated that the
solubility of hydrogen in molten salt is about 1/3 the values used
previously.

2. Only a small amount of lithium was found by chemical analyses of
samples of insulation from the MSRE reactor furnace, so we conclude
that the tritium in the reactor cell was produced in the fuel salt
and diffused through the metal walls of the reactor system into
the cell. |

3. The rate of production of tritium in the fuel salt during the time
that the tritium distribution was being measured is now estimated
to be 54 curies per day.

L, Tritium was found in graphite removed from the reactor core in a
quantity equivalent to a deposition rate of about 8 curies per day.

Ttems 2-4 are discussed by P. N. Haubenreich in a memorandum now in prepa-
ration.

The effect on the distribution of tritium of hydrogen solubility and
of sorption of tritium by graphite were considered in the previous memo-
randum. The calculation of the solubility effect was, however, not entirely
correct (reducing the solubility causes more tritium to enter the off-gas
than was reported), and sorption by graphite was considered in only two
cases. Because of these differences, it seemed desirable to make some
additional calculations. They were made and the results are summarized
in Table 1. |

Values of the reference parameters in the equations that describe
the tritium distribution were listed in Appendix A of CF T70-7-13. The
same values were used in these calculations except that k,, the solu-
bility coefficient for T, in fuel salt, was reduced from 0.06 to 0.02,
and kn, the solubility coefficient for T, in coolant salt, was reduced
from 0.04 to 0.02. The complete set of calculations involves cases for
the following conditions.

I. With UF,/UF; = 1000

A. Reference condition without graphite, with graphite, and
with graphite and hydrogen.
Table 1. Summary of Results of Calculations of Tritium Distribution in MSRE

 

 

 

 

 

Condition Tritium Distribution - Percent of Production Concentrations, molecules/cmaxIO"l
Mass Transfer Metal Coolant Fuel Pump Off-Ges Graphite
Case Coefficient Permeability Cooling Coolant Pump Reactor T; in T, in TF in
No. UF,/UF, (x Ref.) (x Ref.) Hydrogen Air Cell Off-Gas Cell T, TF Total T, TF Total Fuel Salt Coolant Salt Fuel Salt
1 1000 1 1 8 2 0.1 17 b1 31 72 0O O 0 6 0.9 130
2 2 0.k 0 3 8 1k 22 3 70 73 1 0.2 57
3 8 2 0.1 15 37 L Iy 13 20 33 310 50 9Lo
5 0.01 T 2 0.2 11 41 L b5 14 21 35 340 83 990
7 001 2 0.7 0.8 3 8 14 22 3 70 173 420 320 1100
8 0.5 1 5 1 0.2 10 b9 34 83 0O O 0 7 1 140
9 2 0.4 0.1 L 18 20 38 3 53 56 3 0.4 85
10 6 1 0.2 11 55 5 60 10 12 22 k70 T4 1100
12 0.01 5 1 0.2 10 5T 5 62 10 12 22 480 91 1200
14 - 0.001 2 0.7 0.8 3 65 5 70 12 13 25 550 350 1200
15 100 1 1 12 3 0.2 2l 5T L 61 O O 0 8 1 15
16 8 2 0.1 17 ko 3 43 14 16 30 6 0.9 13
17 10 2 0.2 20 L8 O.4 48 17 2 19 400 65 110
19 0.01 9 3 0.3 14 53 0.5 sk 19 2 21 450 120 110
20 0.001 7 2 0.3 11 Ly 3 L8 16 17 32 6 2 13
21 * 3 0.8 1 3 66 0.5 66 23 3 26 560 Lho 130
22 0.5 7 2 0.2 15 T2 L 76 0O O 0 10 2 17
23 6 1 0.2 12 58 4 61 10 10 20 8 1 15
24 7 2 0.2 13 65 0.5 65 11 1 13 550 86 120
26 0.01 6 2 0.3 11 67 0.5 68 12 1 13 570 110 130
27 0.001 6 2 0.3 9 60 L 64 11 10 20 9 2 16
28 * 2 0.7 1 3 T 0.6 T 1k 1 15 650 420 140
Measured distribution 59 -

1 5=9 46~56 15

 

*Indicates hydrogen added to salt at rate of 60 times the production of
tritium. Addition rate is approximately that which would be produced by com-
plete decomposition of 0.5 g/day of oil in pump bowl.
B. Permeability of metal reduced by factor of 100 with graphite
and with graphite and hydrogen.

C. Permeability of metal reduced by factor of 1000 with graph-
ite and with graphite and hydrogen.

IT. Repeat I with all mass transfer coefficients reduced by factor of 2.

IIT. Repeat I and II with UF,/UF; = 100.

Not all the results are reported in Table 1. The salt is the major
barrier to the transport of tritium and reducing the permeability of the
metal by a factor as large as 1000 had no significant effect in some
cases, so the results are not included in the table. For cases with
hydrogen, the hydrogen was added to the fuel salt at a rate of 3 x 1017
molecules/sec. This is 60 times the rate of tritium production and
results in a concentration of hydrogen in the salt that is about what
should be obtained from complete decomposition of 0.5 g per day of oil
in the pump bowl.

The measured distribution is also given in Table 1 and does not
account for 10-28% of the production of tritium. Some of this tritium
was dissolved in the metal, some of 1t was held in deposits in the reactor
system, but I believe that most of it must have left the fuel pump bowl
in the off-gas. The percentages assigned to the cooling air, to the
reactor cell, and to sorption by the graphite could not be too low by
such a large amount. In my consideration of the data I assign 66 to Th%
of the tritium to the fuel pump off-gas.

Examination of the data in Table 1 leads me to conclude that case
27 is in best agreement with the measured distribution. In this case,
UFs/UF, = 100, the mass transfer coefficients were reduced by a factor
of 2, and the permeagbility of the metal was reduced by a factor of 1000
from the reference values. The uncertainty in the mass transfer coeffi-
cients is at least a factor of 2. Oxide on the metal surfaces or a
change from Q proportional to p%/a to Q proportional to p at very low
pressure might produce such a reduction in the effective permeability
of the metal. In case 27 the amount of tritium sorbed by the graphite
is too high, but T; or TF might not be sorbed as efficiently as was
assumed in the calculations. The distributions in other cases, such as
10, 12, 16, in which the hydrogen has an effect, agree about as well
with the measurements except that the flow rate to the reactor cell is
too high, and that measurement seems to me to be our most reliable one.

Two factors deserve additional attention:

1. The distribution is sensitive to the values assigned to the mass
transfer coefficients. In all calculations to date, we have changed
all mass transfer coefficients simultaneously and by the same multi-
plier, on the basis that an uncertainty in one parameter in the cal-
culation would apply to all the mass transfer coefficients. It

 
appears that the distribution could be shifted considerably by
adjusting individual mass transfer coefficients. A more careful
analysis of the mass transfer coefficients in each of the regions
might justify changing only some of the coefficilents.

2. The assumption that graphite retains both tritium and tritium fluo-
ride might not be correct and could markedly affect the amount held
by the graphite. Experimental data are needed to confirm this
assumption or to provide the basis for a better one.

The conclusions and recommendations of CF 70-7-13 are not changed
much by the more recent data and the calculations reported here. The
graphite did indeed prove to be a reservoir of tritium and to have a
greater capacity than had been anticipated. Preliminary measurements
of the solubility of hydrogen in salt and analyses of the lithium in
the insulation in the reactor furnace have reduced some of the uncer-
tainties in the calculations and in the measured distribution. In cal-
culations that give the best agreement with the measured distribution,
the permeability of the metal still seems to be much lower than one
might expect, although the same effect might be obtained by adjusting
the mass transfer coefficients. More of the experimental data outlined
in CF T70-7-13 are needed to provide an adequate understanding of the
behavior of tritium in molten-salt reactors.
\O 003 Oyt W O H

N RN USSR YN PN NP NI NG NI NI ENP Q0N IO NERQQHE D

*

P EEEE QD EE NN TR E PSRN O

TnEcEHE

CEENeENOpEEEC Y

a

n

Affel
Apple

. Anderson

Baes
Bamberger
Beall

nder

Bettis
Billington
Blankenship
Bohlmann
Borkowski
Boyd

Briggs

ntor

Carter
Chapman
Clark
Compere
Cook
Cope, RDT-SSR
Crowley
Culler
Dale
Ditto
kBatherly
Engel
Ferguson
Ferris
Fraas
Franzreb
Frye
Furlong
Gabbard
Gibbons
Grimes
Grindell
Guymon
Harley
Haubenreich
Helms
Huntley

ouye

Jordan
Kaplan
Kasten
Kedl
Kelley
Kirslis
Koger

DISTRIBUTION

57 .
58.
59.
60.
61.

109.
110-112.
113.

PoENrEDIEEED PR RS R

R. B. Korsmeyer
A. I. Krakoviak
T. S. Kress
Kermit Laughon, RDT-OSR
Lundin
Malinauskas
MacPherson
MacPherson
McCoy
McIntosh, AEC, Wash.
McLain
McNeese
McWherter
Meyer
Moore

Nicholson
Perry
Piper
Prince
Richardson
1chardson
Robertson
Rosenthal
Roth, AEC-ORO
Savage
. Savolainen
nlap Scott

H. Shaffer

Shaw, RDT, Wash.
Silverman

Skinner

Smalley, AEC-ORO
Smith

Strehlow
Struxness
Tallackson
Taylor
Thoma
Trauger
Watson, AEC, Wash.
Weinberg
Weir
Whatley
. White .
. Wichner

L. V. Wilson
Gale Young

Central Research Library
Document Reference Section
Laboratory Records
Laboratory Records - RC

HEREECRAIEP S HEQ T

GUEE DR EE P EE S E EwE
HOEE

2

TOHEEREEOEQ RN SO