ORNL-TM-2974.txt

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OAK RIDGE NATIONAL LABORATORY
operated by

UNION CARBIDE CORPORATION
NUCLEAR DIVISION

for the
U.S. ATOMIC ENERGY COMMISSION

ORNL- TM- 297h4

 

COPY NO. -

DATE - April 7, 1970

PLANS FOR POST-OFERATION EXAMINATION OF

THE MOLTEN-SALT REACTOR EXPERIMENT

P. N. Haubenreich and M. Richardson

ABSTRACT

In December 1969, after more than 4 succe .ful years, the nuclear
operation of the MSRE was concluded and the plant was placed in standby.
Work planned for early in FY-1971 includes removal of some core graphite;
viewing inside the reactor vessel and inside the fuel-pump bowl; inspection
of portions of the salt piping, the offgas charcoal bed, the coolant salt
pump, and the control rods; and testing the coolant salt flowmeter, FEach
study is justified by its benefit to the Molten-Salt Reactor Program.
Procedures and tools are available for some jobs; for others, they are

currently being developed. .

Keywords: reactors, fused salts, MSRE, operation, inspection,
maintenance, remote handling, leaks,

NOTICE This document contains information of a preliminary nature
and was prepared primarily for internal use at the Oak Ridge National
Laboratory. It is subject to revision or correction and therefore does

not represent o final report.

3 TED
I—~--———-—--———---i——-_—w-fi—#-«—— LEGAL MOTICE ———rrmm o oo rmoem oo
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; This report was prepared as an account of Government sponsored work. Neither the United States,

nor the Commissien, ner any perscn acting on behalf of the Commission:

A. Makes any warranty or representation, expressed or implied, with respect to the accuracy,
completeness, or usefulness of the information contsined in this report, or that the use of
any informatien, apporatus, method, or process disclosed in this report may not infringe
privately owned rights; or

B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of
any information, apparatus, method, or process disclosed in this report.

As used in the above, '‘person acting on behalf of the Commission’” includes any employee or

contractor of the Commission, or employee of such contractor, to the extent that such employee

or contractor of the Commission, or employee of such contractor prepares, disseminates, or
provides access to, any information pursuent to his employment or contract with the Commission,

or his employment with such contractor.

 

 

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CONTENTS

ABSTRACT . . . . &

e : : e e e e e e e e e e e e e e e e e e e

GOA L L T T |

CRIiszz %O?T OPERATION EXAMINATIONS . . . . . : : : L

STEPS IN DEFINING THE CAMPAiG& : L

STUDIES AND TASKS TO BE UNDERTAKE& L
Investigation of Leak Near Freeze éaiv; %V:léS. L

Examination
of Surfaces Insi
gide the Fuel-Pu
-Pump Bowl .

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Examination of Fuel Piping

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Inspection of Fuel Drain Line

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xamination of Charcoal Bed Inlet

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Examination of Radiator Tubing

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Test of
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Inspection of Control Rods

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Verifi .
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Decontamination

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Securing the Plant.

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Disposal. . . . .
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LEGAL NOTICE

sponsored work, Nefther the United

This report Was prepar
States, noT the Commission, nor any perso
y warranty of 'repreneutat\on,
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atugd, method, oF praces?

uee of, or for damages resgulting from e
report.
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{ the information contal
t may not 1nfringe

A. Makes an
disclosed tn thif repor

racy, completen2ss, ©
of any information, appar
privately awned rightg; oF

B, Aspumes Y witk respect to the

 
 

   
   

ployee or contrac
such employee ar
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with the Commissgion, T

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1
INTRODUCTION

The primary purpose of the Molten-Salt Reactor Experiment was to
demonstrate the practicality of the molten-salt reactor concept. To this
end its design! incorporated essentially the same materials and many of
the design features of proposed molten-salt power reactors. Its primary
purpose was accomplished as it was operated for more than 4 years at Qak
Ridge National Laboratory, Experience® with the MSRE was quite encouraging
and a great deal of new information (particularly with regard to fission
product behavior) was obtained, In December 1969, the reactor was shut
down because its original goals had been met and continued operation,
although offering additional information, could not be Jjustified in the
very stringent budget situation. Except for removal of an experimental
array from the core, all post-operation examination was deferred until
the next fiscal year, In the interim the reactor was placed in a standby

condition,”
GOAIS OF POST-CPERATION EXAMINATIONS

The broad goal of the post-operation examinations is to complete the
gathering of information from the MSRE by in-place inspection, removal of
specimens and some pieces of equipment, and detailed examination of these
in hot cells, Specific objectives include determination of the condition
of materials with the greatest exposure to the reactor environment, the
condition of key equipment (pumps, heaters, insulation), the location and

nature of deposits in selected parts of the fuel salt and offgas systems,

 

R. C. Robertson, MSRE Design and Operations Report, Part I —
Description of Reactor Design, ORNL-TM-728 (January 1965).

P, N, Haubenreich and J. R. Engel, "Experience with the MSRE,"
Nucl. Appl, Tech. 8, 118 (1970).

3p. N. Haubenreich and R. H. Guymeon, Plans for the MSRE Between End
of Nuclear QOperation and Beginning of Post-Operation Examinations,
internal memorandum MSR-69-121 (December 1969).
and the exact location and nature of a leak in a salt freeze valve. This
information will influence materials development and the design of equip-

ment and systems for future molten-salt reactors,

CRITERTA

The scope of the post-operation studies will be limited to those
whose costs are Justified by the benefits to the Molten-Salt Reactor Program.
Tentative plans call for holding the radicactive fuel salt (about
360,000 curies of fission products as of July 1970) frozen in the MSRE
tanks until such time as salt mine disposal is feasible. The post-operation
examinations shall not prevent the ultimate removal of the salt nor leave
the system in an unsafe condition in the interim. 1In addition, to pre-
serve the option of fluorinating the salt for uranium recovery, the opera-
bility of the processing facility shall be preserved.

Exposure of personnel to radiation during the post-operation exami-
nation shall not exceed normal occupational limits prescribed by ORNL

and the USAEC.

STEPS IN DEFINING THE CAMPAIGN

Planning for the post-operation examination, to some extent, began
with the design of the reactor, when provisions were made for removing the
5 central bars of core graphite. Final selection of post-operation studies,
of course, had to awalt operating experience and evaluation to point out
areas of most interest and other program developments (such as the budget)
to determine what could be justified.

In February 1969, the head of the MSRE Operations Department sent a
request for suggestions for final operations and shutdown of the MSRE to
group leaders in the MSRP. Responses were consolidated to eliminate dupli-
cations and in October 1969, a tentative list of post-operation tasks was
distributed with a request for comments. This list was discussed with ORNL
and AEC-ORO reactor safety review committees and with AEC-DRDT representa-

tives, After discussion and review of the tentative list with MSRP staff
members in which benefits were weighed against costs, the program described

in the next section was arrived at in March 1970.

STUDIES AND TASKS TO BE UNDERTAKEN

The studies that we propose to make are listed in Table 1. Under
each study are listed the separate jobs, some to be done on-site, some in
X-10 hot cells, involved in that study. DNot shown in the table are the
tagks of rewoving some items for use in development facilities, decontami-
nating areas outside the containment cells, securing the plant, and dis-
posing of the fuel salt. The Justification for and objectives of each
study (in the order listed in Table 1) and each task are discussed in the
text of this section., Job descriptions, including purposes and general

procedures, are presented in the next section.

Table 1

Iist of Studies to be Made and the Jobs that will be Involved

 

Investigation of leak near freeze valve FV-105

View vicinity of FV-105
Excise FV-105
Inspect FV-105

Examination of fuel-pump bowl internals

Excise sampler cage and baffle
View inside of pump bowl
Inspect sampler cage and baffle

Examination of reactor vessel internals

Prepare for core work

Remove access plug and rod thimbles

Remove some core graphite

View core and inside of reactor vessel heads
Close reactor access

Cut off piece of rod thimble

Inspect core graphite bar

Inspect rod thimble piece
Table 1 (continued)

Examination of fuel piping

Fxcise sections of piping at heat exchanger inlet and outlet
Inspect sections of piping

Inspection of fuel drain line

Remove heater H-103
View drain line inside reactor furnace

Examination of charcoal bed inlet

Excise inlet section of a main charcoal bed
Inspect inlet section

Examination of radiator tubing

Excise tubing near inlet and near outlet
Inspect for deposits and corrosion

Examination of thermocouple wells in coolant salt piping

Fixcise wells at radiator inlet and outlet
Inspect for deposits and integrity

Test of differential pressure system on coolant salt flowmeter

Cut coolant piping
Test pressure measuring system

Inspection of coolant pump rotary element

Remove rotary element
Inspect

Inspection of control rods

Examine
Remove elements
Inspect elements

Verification of remote maintainability

Remove and inspect heater units
Remove fuel pump motor
Disconnect fuel sampler line
Investigation of Ieak Near Freeze Valve FV-105

A leak appeared in the primary system on December 12, 1969 shortly
after the scheduled end of nuclear operation., Correlation of changes in
cell air activities with certain operations Indicated that a small leak
had developed in or near freeze valve FV-105 (leading to fuel drain tank
FD-2) about two hours after the fuel was drained for the last time,

Amounts of xenon and iodine indicated that a few ft° of gas and perhaps some
salt (1 cc or less) escaped into the cell before the leak was effectively
stopped by freezing salt in the line,

This is the only leak that ever occurred in the primary system and
the explanation is not known. Examination of radiographs and other con-
struction records showed nothing suspicious. We believe corrosion could
not have been a significant factor in the origin of the leak, and radiation
damage at this location should be virtually nil. The most likely hypothesis
is that thermal stresses in the valve caused a crack to originate at the
welded Juncture of the cooling-air shroud and the pipe and to propagate
through the pipe wall.

We should determine the exact location and description of the lesk

and, if' possible, derive an explanation,
Examination of Surfaces Inside the Fuel-Pump Bowl

During operation of the MSRE, effects related to the salt-gas inter-
face in the fuel-pump bowl were of considerable Importance. Bubbler level
elements indicated that considerable amounts of gas were carried under the
salt surface by the xenon stripper jets. The density profile above the
bubblers could not be measured, but the fluid surface was certainly higher
because of the gas. There is reason to think that the surface was not
quite uniform (being lower inside the sampler baffle, for example), Certain
fission products tended to concentrate at salt surfaces, with perhaps some
going into the gas space as a "smoke." 01l leaked into the pump bowl from
the shaft bearing region at a few cc per day, ©Some oil decomposition pro-
ducts probably deposited on the pump bowl surfaces and some on the salt
where they may have influenced fission product separation and bubble be-

havior. Thermocouple readings indicated that fission product heating of
10

the pump bowl above the salt level was moderate but changed from time to
time for unknown reasons.

A sample capsule was dropped into the pump bowl in August 1967 and
another in March 1968. The steel cap of the first capsule was retrieved
in May 1968, There was some evidence that the second capsule was Jjammed
between the cage and baffle during recovery attempts.

We should observe surfaces inside the pump bowl for evidence of depo-
sition and the patterns displayed. It appears now that it will probably
be practical to cut out a section of the pump bowl top with the sample
cage and baffle attached. This would make 1t possible to determine much
more about the deposits and also to inspect for evidence of corrosion,
(Conditions in the vicinity of the dissimilar metal junctions in the sample
capsule are particularly interesting.) The information will aid in under-
standing the MSRE behavior and will be useful in evaluating design of off-

gas systems for future molten-salt reactors,
Examination of Reactor Vessel Internals

The effect of reactor operation on core materials was monitored by ex-
posure at the center of the core of experimental arrays containing speci-
mens of graphite and Hastelloy-N like those used in the construction of
the MSRE. Arrays were removed after 1087, 4510, 9005, 11,555, and 13,172
equivalent full-power hours., Usually the replacement array included some
subassemblies with previous exposure, so very long total exposures were
accumulated on some specimens before detalled examination and testing.

The conditions of the specimens, which were assumed to be typical of the
core, never gave any cause for concern over the condition of the core,
Although this surveillance program was presumably quite adequate, its
vallidity can be supported by examination of portions of the core graphite
and Hastelloy-N exposed from start to end of the MSRE operation,

The condition of Hastelloy-N can be determined by inspection of the
removable core access assembly, which Includes the control rod thimbles
and a plug exposed to the fuel stream in the core exit, After the assembly
has been visually inspected in the reactor cell, a portion of a rod thimble

can be cut off and examined closely in a hot cell, Metallographic
11

examination of interior surfaces will reveal any effect of the exposure

to the cell atmosphere used for cooling. The exterior surface will show
effects of very long exposure to the fuel salt. (It will not be practical
to shape specimens for physical property testing from the thimbles, but
this is unnecessary since irradiation effects were well described by the
specimens from the experimental arrays.)

Removal of one of the five central stringers will make available
graphite exposed to fuel flowing through channels with a cross section
typical of the bulk of the core. Surface appearance and penetration of
salt constituents and fission products in regions free of flaws should be
compared with results from the experimental arrays.

There was no detectable evidence of any physical damage to the core
during operation, nor did thermocouple readings on the lower head and near
the core support flange indicate any substantial accumulation of sediment,
Nevertheless, a look will be worthwhile, An optical device and light can
be used to view and photograph the top of the core and the upper head of
the reactor vessel, the lower grid structure, the bottom head, and the
drain line inlet., If loose fragments, broken graphite, sediment or other

deposits are discovered, they should be examined as closely as 1s practical.
Examination of Fuel Piping

The MSRE operated for 13,172 eguivalent full-power hours with a
temperature difference of LO°F between the fuel entering and leaving the
heat exchanger. Close examination and comparison of Hastelloy-N surfaces
exposed to fuel at the extremes of the temperature range will provide in-
formation on corrosion and mass transport under the reactor conditions.
Short sections of the 5-inch pipe near the heat exchanger inlet and be-
tween the heat exchanger and the reactor vessel should be cut out and

examined metallographically for this purpose,
Inspection of Fuel Drain Line

The Jjuncture of the fuel drain line with the reactor vessel was sub-
jected to a combination of stress and irradiation about as severe as any
in the reactor. Removal of this section is not practical, but it can be

viewed from a distance by removal of heater H-103 and insertion of viewing
12

devices in its place inside the reactor furnace., The juncture, the drain
line, and the exterior of the insulation box around the drain valve should

be scrutinized for any evidence of incipient trouble,
Examination of Charcoal Bed Inlet

During the initial escalation of the MSRE power in 1966, plugging
occurred at several points in the fuel offgas system, including the inlets
of the charcoal beds. Even after the installation of an efficient filter
(the "particle trap"), plugging recurred at the charcoal bed inlets, This
was believed to be due to polymerization of oil vapors downstream of the
filter and accumulation of the polymers on the steel wool in the entrances
of the beds. This could not be verified directly, but the restrictions
could be cleared temporarily by lowering the cooling water level around
the beds and applying heat to the inlet section. There was concern over
possible reduction of the adsorptive capacity of the charcoal by the oil
residues but no change was detectable from the few thermocouples spaced at
80-ft intervals in the bed. A short section of the inlet to one section
of the beds should be cut out and the explanation for the recurrent plugging
verified, A sample of charcoal from the inlet should be tested and if its
adsorptive capacity is seriously reduced, samples should be obtained from

further along the bed to determine the extent of the effect.
Examination of Radiator Tubing

The chromium concentration of the coolant salt remained very low
through the entire operation, indicating that corrosion was extremely low
or that corrosion-product chromium was being deposited. There were no
corrosion surveillance specimens in the coolant system, Sections of the
3/k-inch tubing should be cut from the radiator near the inlet and outlet

ends and examined for information on corrosion in the coolant systen,
Examination of Thermocouple Wells in Coolant Piping

Because of the desire to eliminate, insofar as possible, conceivable
sources of trouble, the MSRE design included only 2 thermocouple wells in
salt piping: one each at the inlet and outlet of the radiator, The pipe

with these wells should be cut out and sectioned and a careful inspection
13

made to see if the wells suffered any unusual corrosion. The pessibility
of deposition on what were to some extent "cold fingers" should also be

investigated,
Test of d/p System on Coolant Salt Flowmeter

There is a significant discrepancy between the reactor power that was
indicated by the system heat balance and the power indicated by observed
changes in isotopic ratiocs of uranium and plutonium in the fuel., The
latter indicated up to 10 percent lower power than the heat balance. The
possible reasons for the discrepancy have been checked one by one until
now only the coolant salt flow rate has not been verified as thoroughly as
possible, This must be done. The ultimate test will consist of cutting
the salt lines near the venturi flowmeter and applying signals to test the

entire transmitting and modifying systen,
Inspection of Coolant-Pump Rotary Element

The salt pumps are key components in a molten-salt reactor. Except
for the small amount of oil leakage (about 2 - 5 cc/day) into the pump
bowls, there was no problem with either the coolant-salt or fuel-salt
pump in the MSRE, The problems due to oil leakage were not serious enough
to warrant replacing the original units with seal-welded replacement rotary
elements that would have had no oil leakage into the bowl. As a result,
the original units served for the entire duration of the operation. An
inspection should be made to determine the condition of the pumps and to
permit some judgement as to remaining service life., The fuel and coolant
rotary elements are essentially the same, but the coolant pump operated
considerably longer, pumping salt for 26,076 hr compared to 21,788 hr for
the fuel pump. Since the coolant pump rotary element is also nonradio-

active and more accessible, it should be removed and thoroughly inspected,
Inspection of Control Rods

The control rods in the MSRE, of a unique, flexible design, on the
whole performed well, There were gradual changes in drop times, however,
that were attributed in part to changes in the flexibility of the rods

with long exposure and use. On occasion, rods were pulled out of the
1k

thimbles and viewed from a distance in the reactor cell for evidence of
unusual scratches or dragging. (None was found.) It was not possible to
inspect the internals of the rod or to ascribe a reason for changes in
flexibility.

The rods must be pulled to gain access to the core and at that time
the active section of one should be removed for examination in a hot cell,
The Inconel-canned Al-0=-Gd0s ceramic poison elements should be checked
for dimensional changes and the flexible metal hose and rod should be

closely inspected,
Verification of Remote Maintainability

An important goal of the MSRE was to demonstrate that maintenance of
the molten-salt reactor, with its highly radioactive fuel circulation sys-
tem, was in fact practical, To this end, the radiocactive portions, in-
cluding virtually everything in the reactor cell, were designed to be
replaceable., Replacement of core specimens, work on the offgas system,
replacement of alr-line disconnects, and repair of the fuel sampler-
enricher and in-cell heater units demonstrated the feasibility of the
general approach, Some features were not tested, however, because most
of the equipment required no maintenance, It would be worthwhile to try
certain of these features., The difficulty of replacing the fuel-pump
motor should be determined by removing the old motor or at least loosening
several of the flange bolts. The flanged section of the sampler tube,
which was designed to be swung out of the way for pump bowl replacement
should be removed as intended., (This needs to be done in preparation for

cutting into the pump bowl.)
Removal of Coolant Salt Pump Bowl and Piping

It has been proposed that a fluoroborate technology test loop be con-
structed, using the MSRE coolant pump and other portions of the coolant
salt system, ©Since portions ouwtside the reactor cell are not radioactive,
removal would be a straightforward task that can be done when needed. The
only consideration is that lines leading into the reactor cell be sealed,

since they are penetrations of the containment envelope.
15

Recovery of MSRE Coolant Salt

 

Salt for a proposed loop to test gas injection and stripping tech-
nology can be prepared most economically by adding ThF, and LiF to the
MSRE coolant szlt, The coolant salt, 2610 kg of LiF-BeF- (66 - 34 mole
percent), should be melted and removed when required for this purpose.
This operation will also test some aspects of techniques that may be used

eventually in disposal of the fuel salt,

Decontamination

 

The spread of radicactivity during the work described above will be
controlled by proper ventilation, temporary containment enclosures, the
establishment of contamination zones, and other techniques that have been
proved in use at the MSRE and elsewhere in CORNL. When necessary during
the campaign and at its conclusion, some of the contaminated tools and
material will be disposed of and the rest will be decontaminated., Before
the task is finished, everything outside the containment will be decon-

taminated to safe levels,

Securing the Plant

 

There is currently no demand for the fissile material in the MSERE
fuel salt (37 kg U, 84% EB%J). Because of the extremely high =33 content
(220 ppm) and consequent radiation problems, it is doubtful that the
uranium will ever be worth the cost of recovery from the salt., We propose
to keep the fuel salt frozen in the MSRE drain tanks, safely contained
until developments make it possible to decide on the optimum method of
disposal, Meanwhile the option of stripping the uranium by the fluoride
volatility process will be retained by preserving the M3RE processing
plant.

The MSRE reactor cell and drain tank cell will be resealed after the
examination work is completed, Service lines into the cells which were
left connected to the ancillary systems during the interim period will be
capped to minimize chances of accidental openings. The reactor equipment
that is heavily contaminated with fission products will be retained within

the cells and the offgas containment system. (As of July 1970, the total
16

fission product activity in the salt and elsewhere in the reactor will
amount to about 360,000 curies.) Some radioactive items with little or
no transferable activity may be placed in other shielded cells in the re-
actor building. Radiation zones will be defined, marked and secured as
required by ORNL procedures., The conditions in the reactor, cells, and
building will continue to be monitored remotely by the Central Waste Moni-
toring Group at ORNL. Access to the reactor building and grounds will be
strictly controlled by the existing system of fences, gates, and guard

service.

Disposal

Items that are not required for the containment of the radioactivity
nor for the possible future operation of the processing facility will be
identified and advertised. Those items whose removal can be Jjustified by
Program needs will be removed. ©Such removal will be planned and super-
vised to guard against inadvertent compromise of the continuing needs of
the MSRE,

The safety of the plant will be reviewed periodically by appropriate
groups 1in ORNL,

We expect that eventually it may become desirable to transfer the
fuel salt, containing the fissile material and the bulk of the fission
products, to a more permanent waste storage situation. The best way to
get the salt out would now appear to be to cut the line from the salt
fluorination tank to the experimental salt still and transfer batches of
molten salt into transport containers connected at that point. It would
also be feasible to pull salt into containers through a dip tube installed
through the drain tank access port. After the bulk of the activity is re-
moved this way, 1if there 1s no foreseeable need for eguipment in the re-
actor and drain cells, the cells can be filled in and closed to provide

permanent containment for the remaining activity.
17

JOB DESCRIPTIONS

This section gives some additional detail on the jobs that will be
involved in the studies described in the previous section., The letters
in each job identification refer to the principal location of the work
(RC = reactor cell; DC = drain cell; CC = coolant cell; HC = hot cell =t
X-10; O = at reactor site outside of cells; L = laboratory). The numbers
in the job identification refer to the sequence in which the work will
probably be done (see Table 2), The order in which the jobs are discussed,
however, is that in which they are listed in Table 1. The "purpose" is
the specific contribution toward the broader objective of the study of
which the job is part, A preliminary description of the procedure is
given to indicate the scope of the job and the present plan of attack.

The detailed procedures have yvet to be developed and proved in most cases.,

 

 

View Vicinity of Freeze Valve FV-105 (Job DC-1)

Purpose — To look for evidence of the leak and its cause, If any
is found, to decide more precisely the probable location of the leak, If
any salt is observed, to determine the amount and its condition. To ob-
tain measurements and photographs to be used in detailed plans for excision
of section with the leak,

General Procedure — Remove drain cell top blocks, cut membrane, set
up maintenance shield, remove lower blocks, insert lights and viewing
devices, take photographs, remove heater units in viecinity of FV-105, view

and photograph, remove tools, reinstall blocks, remove maintenance shield,

 

 

Excise FV-105 (Job DC-2)
Purpose — To remove the section of drain line where the leak has
been found (or is believed to be) so that detailed inspection can be made.

General Procedure — Set up maintenance shield, remove lower block,

 

install lights and viewing devices, Clear away interfering wiring,
18

insulation and supports., Use pipe cutter to sever lines, Lift sections
to be inspected into shielded carrier and transport to hot cell, Thread
ends of line in cell, close with pipe caps, test. Remove tools, etec.,
replace block, remove maintenance shield, seal membrane, install top

blocks,

 

 

Inspect FV-105 (Job HC-6)

Purpose — To ascertain the location, nature and probable cause of
the leak,
General Procedure — (In hot cell) — If leak is in FV-105, remove

 

cooling-air shroud. Inspect exterior visually and by dye-penetrant tech-

nique. ©Section and examine metallographically.

 

 

Excise Fuel Pump Sampler Cage and Baffle (Job RC-13)

Purpose — To remove this assembly to a hot cell for detailed exami-
nation. To provide an opening through which the interior of the fuel-
pump bowl can be viewed.

General Procedure — Set up maintenance shield, install lights and

 

viewing device, Remove FP heaters and leads. Use plasma torch to cut
away interfering portion of support plate and ring. Remove flanged sec-
tion of sampler tube, then cut tube Jjust above bowl cooling shroud, Cut
out ring of shroud around tube, Use plasma torch to cut through upper
head of FP bowl in cirecle close around sampler baffle, Lift short sec-
tion of sample line with attached latch stop, capsule cage and baffle

into shielded carrier and deliver to hot cell,

 

 

Inspect Sampler Cage and Baffle (Job HC-h)

Purpose — To determine the nature of any deposits on the metal sur-
faces inside and outside of the baffle and how the deposition varied at

and above the salt-gas interface. To see if the 10-g capsule that was
19

dropped in March 1968 is still wedged outside the cage as it seemed to
be. To examine specimens from selected spots for evidence of corrosion.
General Procedure — (In hot cell) — Remove assembly from carrier,
view and photograph. Section vertically and horizontally. Remove de-
posits from some sections mechanically, from others chemically, Prepare

specimens for metallographic examination,

 

 

View Inside Pump Bowl (Job RC-1k)

Purpose — To make observations and photographs that can be used
with the results of Job HC-4 to describe the deposition of salt mist,
0il residues (and perhaps fission products) on the various surfaces ex-
posed to salt and gas in the pump bowl,

General Procedure — After removal of the sampler cage and barffle

 

(Job RC-13) look down at bottom head below hole and photograph it. In-
sert viewing device with light through the hole (about 3-in. diameter).
Look at and photograph top head, top and bottom of "shed rocof," overflow
line, volute support cylinder, and volute. ILook for remains of capsules

and latch key in bottom head. Remove viewing equipment.

 

 

Close Fuel Pump Bowl (Job RC-15)

Purpose — To prevent free communication between the inside of the
fuel system and the cell atmosphere under credible future conditions,
(There would seem to be no way for the pressure differential to exceed
5 psi or the %temperature to exceed 200°F.,)

General Procedure — Prepare a patch to fit over the hole and seal

 

against the pump tank, Apply the patch, remove tools.

 

 

Prepare for Core Work (Job RC-2)

Purpose — To clear the way for opening the core access flange, To

make the control rods available for inspection.
20

General Procedure — Set up maintenance shield. (The upper blocks

 

and part of the reactor cell membrane will have been removed in Job RC-1.)
Disconnect control rod drives and move to spare cell. Remove control rods
and hang in reactor cell. Remove the graphite sampling standpipe. Clear
away control rod drive shielding, bracing and any other obstruction from

the reactor access flange area,

 

 

Remove Core Access Plug and Rod Thimbles (Job RC-T)

Purpose — To give access to the interior of the reactor vessel. To
permit inspection of Hastelloy-N that has received long exposure in the
core. To permit examination of plug surfaces for evidence of unusual de-
position around the salt-gas interface.

General Procedure — Unbolt, 1ift out, and hang in the reactor cell.

 

 

Remove Some Core Graphite (Job RC-8)

Purpose — To provide a bar of graphite from the core for examination
in a hot cell,

General Procedure — Lift one of corner bars into a carrier and de-

 

liver to hot cell, (A second bar, perhaps the center, may also be re-

moved., )

 

 

View Core and Inside of Reactor Vessel Heads (Job RC-9)

Purpose — To look for evidence of unusual deposits in low-velocity
regions, any fragments of graphite or other loose objects, and any broken
graphite stringers.

General Procedure — ILower viewing device and light into upper head.
View and photograph inside of core access nozzle and fuel outlet on the
way down, View and photograph in upper head with particular attention to
top of graphite and retaining wires, Lower device through core, scanning
for anything unusual. View and photograph horizontal graphite, support

grid, flow directors and surface of lower head, Remove viewing devices,
21

Close Reactor Access (Job RC-10)

 

Purpose — To prevent free communication between the inside of the
fuel system and the cell atmosphere under credible future conditions,

General Procedure — Install a blank flange on core access nozzle,

 

 

Cut Off Piece of Rod Thimble (Job RC-11)

 

Purpose — To obtain a piece of thimble for close examination in
hot cell.
General Procedure — With access norzle and attached rod thimbles in

 

the reactor cell, sever No., 3 thimble just below the pipe-to-tube tran-
sition., Deliver the lower end of thimble, including the guide assembly

and threat, to hot cell.

 

 

Inspect Core Graphite Bar (Job HC-2)

Purpose — To see 1f there 1s any perceptible difference between con-
dition of this graphite and that of the graphite in the specimen arrays,
To look for evidence of unusual flow situations.

General Procedure — (In hot cell) — Examine surfaces, observe pat-

 

Terns related to flow in channels, look for any evidence of salt intrusion
between bars. Section bar and determine distribution of salt constituents

and fission products in graphite,

 

 

Inspect Control Rod Thimble (Job HC-3)

Purpose — To attempt to determine why a rod hung on withdrawal and
the replacement rod (with beveled shoulders on the end fitting) did not.
To see if moisture or foreign matter (such as fragments of blower drive
belts) in the cooling air had significant deleterious effects. To de-
termine if surfaces exposed to salt were corroded or otherwise affected.

General Procedure — (In hot cell) — Cut open to reveal lower ends
of guide bars. See if bars are loose or warped. Examine surfaces for

evidence of corrosion.,
22

Excise Sections of Fuel Piping (Job RC-1T)

Purpose — To remove surfaces from hot and cold sides of fuel circu-
lation loop for close examination, closing up the openings after the
removal,

General Procedure — Set up maintenance shield, Use an 18-in,-dia
cutting wheel on a mast-mounted tool to cut out 12-in, sections of 5-in,
Plpe. One section will be from Line 10l between the pump discharge and
freeze flange 101l; the other from the horizontal run of line 102 between
the heat exchanger exit and freeze flange 102. Transfer sections in
shielded carriers to hot cells. Close severed ends of pipe in cell with

caps suitable for anticipated conditions.

 

 

Inspect Sections of Fuel Piping (Job HC-5)

Purpose — To determine effects of corrosion and fission product de-
position for comparisons between "hot'" and "cold" sections and with other
indications (core specimens, rod thimbles, remote gamma-ray spectrometry).

General Procedure — (In hot cell) — Examine surfaces metallog-

 

raphically and for elemental composition of deposits.

 

 

Remove Heater H-103 from Fuel Drain Line (Job RC-3)

Purpose — To provide an opening through which equipment can be in-
serted to view beneath reactor vessel, To test maintalnability.
General Procedure — Set up maintenance shield. Pull H-103 and store

in reactor cell,

 

 

View Drain Line Inside Reactor Furnace {(Job RC-L4)

Purpose = To look for effects of operation and evidence of in-
cipient trouble,

General Procedure — Insert viewing device with light through H-103

 

port and guide sleeve in thermal shield. View and photograph outside of
23

FV-103 enclosure, with attention to condition of sheet metal, insulation
and thermocouples. Scrutinize and photograph drain line and visible
portion of reactor vessel, with emphasis on drain line near vessel

Juncture. Remove viewing device,

 

 

Excise Inlet Section of Main Charcoal Bed (Job 0-5)

Purpose — To get short section at inlet of one main charcoal bed to
hot cell for examination,

General Procedure — Setl up work shield, Lower water in charcoal

 

bed pit. Sever 1/2-inch inlet line near 1-1/2-inch cap at bed entrance,

Cut bed about 6 inches below cap, taking care not to spill charcoal, Re-
move in shielded carrier to hot cell. Cap 1/2-inch line and bed (1—1/2-

inch pipe).

 

 

Inspect Inlet Section of Main Charcoal Bed (Job HC-T)

Purpose — To determine reason for recurrent plugging. To determine
if adsorptive capacity of charcoal is significantly reduced, If so, to
determine the reason.

General Procedure — Cut open, look at, and photograph steel-wool-

 

packed inlet section. Remove charcoal, Test adsorptive capacity for
xenon or krypton. Compare with result of same test on unused charcoal

of same type.

 

 

Excise Sections of Radiator Tubing (Job 0-2)

Purpose — To provide specimens from "hot' and "cold" ends of tube
bundle.

General Procedure — Cut out a 6-inch section of 3/L-inch tube near

 

inlet end of tube bundle and one near outlet end. Deliver to Metals and
Ceramics Division laboratory. (These specimens will not be radioactive,
but precautions with regard to beryllium must be observed.) Close cut

ends of tubes in radiator.
e

Inspect Sections of Radiator Tubing (Job L-1)

Purpose — To look for effects of corrosion and mass transport,
Genergl Procedure — Examine metallographically., Determine compo-

 

sition of any deposits.

 

 

Excise TC Wells at Radiator (Job 0-3)

Purpose — To remove these wells for inspection,

General Procedure — Observing beryllium precautions, cut out a 6-in,

 

section of 5-inch coolant piping containing radiator inlet thermocouple
well, Cut out a similar section with the outlet well. Deliver to M & C

laboratory. Cap severed endsg of pipe in coolant system.

 

 

Inspect Coolant TC Wells (Job L-2)

Purpose — To look for evidence of any unusual corrosion or incipient
trouble, (Pipe surfaces can also be compared with surfaces in radiator
tubes.)

General Procedure — Examine metallographically. Determine compo-

 

sition of any deposits,

 

 

Test d/p System on Coolant Salt Flowmeter (Job 0-1)

Purpose — To determine the output from flow transmitters FI-2014A
and FT-201B as a function of the differential pressure applied to the
cells. The calibration is to be done in place to avoid any movement of
the salt-NaK diaphragm seals or the NaK-filled lines leading to the d/p
cells which conceivably could cause a shift in the readings.

General Procedure — Cut out a section of line-201 just ahead of up-
stream d/p connections, Install plug in venturi between the upstream and
throat d/p connections, Cap the line and apply argon pressure to section
with upstream d/p connections. Record output for both flow transmitters

as a function of applied d/p over full range of transmitters,
25

Remove Coolant Pump Rotary Element (Job O-k)

Purpose — To permit detailed inspection of the rotary element and
interior of the pump.

General Procedure — Disconnect, remove and deliver to Reactor Di-
vision pump facility in Y-12, After inspection of interior of pump, in-

stall cover plate to close the opening.

 

 

Inspect Coolant Pump Rotary Element (Job L-3)

Purpose — To determine effects of operation., To obtain information
on which to base judgement of serviceability and remaining life,

General Procedure — Observe evidence of oil leakage and decomposition.

 

Look for unusual rubbing., Check key dimensions against originals,

 

 

Examine Control Rods (Job RC-5)

Purpose — To see if there is any evidence of unusual rubbing or
damage on the outside of the rod.
General Procedure — With the rod hanging in the reactor cell, ex-

amine carefully through periscope.

 

 

Remove Section of Control Rod (Job RC-6)

Purpose — To get active section of control rod to hot cell for
inspection,
General Procedure —— Cut Control Rod No. 3 just above poison elements,

Deliver lower end of rod, with elements, to hot cell.

 

 

Inspect Control Rod and Flements (Job HC-1)

Purpose — To lock for possible explanation of changes in stiffness

of rod. To inspect elements for effects of exposure.
26

General Procedure — Remove poison elements, Examine hose for degree

 

of oxidation and roughening of surfaces that slide when hose is flexed.
Measure canned elements. If any can is swelled, cut open and determine

condition of ceramic.

 

 

Remove and Inspect Heater Units (Job RC-16)

Purpose ~— To determine condition of units. To judge difficulty of
repair and replacement, To make way for excision of sections of fuel pipe,

General Procedure — Set up maintenance shield, Disconnect heater

 

H-101-1, Lift and set back in place, noting difficulties. Remove to
equipment storage cell, View, Repeat for heater H-102-3.

 

 

Test Fuel Pump Motor Removal (Job RC-1)

Purpose — To determine if unbolting system is still operable after
over L years' exposure.

General Procedure — Unbolt and remove all top blocks., Cut and re-

 

move sections of membrane as required for this and later jobs,., Set up
maintenance shield. Disconnect power and instrument leads to pump motor.
Unbolt oil and water lines, Loosen several extension bolts on motor
flange. If motor must be off for Job RC-13, proceed to remove motor to

equipment storage cell.

 

 

Disconnect Fuel Sampler Line (Job RC-12)

Purpose — To determine if disconnect system is still operable after
long exposure to cell environment, To prepare for excision of sampler
cage and baffle.

General Procedure = Set up maintenance shield. Remove clamps from

 

flanges on spoolpiece. Use installed jack to compress bellows and clear
flanges., Swing aside. Note any difficulties, Judge practicality of pro-

visions for remote removal of pump bowl,
27

SCHEDULE

Some of the non-radioactive work, such as that on the coolant system,
may begin before July 1, 1970 if funds are available, Before the work in
the reactor cell and drain tank cell can commence, tools must be procured
and tested, detailed procedures must be developed, and the plans must be
reviewed and approved by program and safety groups. A target date of
July 6 has been set for the beginning of the in-cell work.

Table 2 shows the sequence of in-cell work that now appears most
logical, progressing generally from jobs involving less chance of contami-
nation to those likely to involve the most contamination of the cell,
tools, and shielding, The estimated dates tend to be optimistic since
they include no allowance for "unusual' delays. Although critical-path
scheduling was used in planning maintenance and modification work through-
out the operation of the MSRE, this type of diagram is not shown here be-
cause the in-cell work requiring the portable maintenance shield falls on
a single path and most of the other work can be done as "fill-in" jobs
whenever it is most convenient,

A goal will be to have virtually all the work of securing the plant
finished by October 2, 1970. Hot-cell work and analyses should be com-
pleted by December h, 1970. These dates may be extended if, for example,

it is more economical to do so than to work overtime.

STATUS

As of April 10, the general strategy has been decided for each job
and plans have been sketched in enough detail to establish confidence in
the feasibility (by one means or another) of all the important jobs. A
shear and plasma torch have been selected for procurement, other tools and
the maintenance shield are being readied, and the prototype fuel pump is
on hand to be set up in the maintenance practice cell as a mock-up for

developing the procedure for cutting into the pump bowl.
 

a
Sequence

28

Table 2

and Estimated Datesb

of Work

In MSRE Reactor and Drain Tank Cells and X-10 Hot Cells

 

July 6
10

15

28

21

Sep. L
18

Reactor and Drain Tank Cells

DC-1
RC-1
RC-2
RC-3
RC-4
RC-5
RC-6
RC-T
RC-8
RC-9
RC-10
RC-11
RC-12
RC-13
RC-14
RC-15
RC-16
RC-17
DC-2

View FV-105 vicinity
Test FP motor removal
Prepare for core work
Remove heater H-103
View beneath reactor
Examine control rods
Remove section or rod
Remove core access plug
Remove some graphite
View core

Close core access

Cut rod thimble

Open sampler tube
Excise cage and baffle
View in FP bowl

Close P bowl

Remove and check heaters
Cut 5-in. fuel pipe
Excise FV-105

Seal cells

Decontaminate

Available to Hot Cells

Control rod and elements

Core graphite

Rod thimble

Cage and baffle

5~inch pipe
FV-105

 

The Jobs listed for the MSRE cells cannot be done in parallel be-
cause all require the portable maintenance shield. The sequence was de-

termined mainly by contamination considerations,

for hot-cell work in the sequence listed.

Ttems will be available

10These dates are based on preliminary procedures and make no
allowance for unusual delays.
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29

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aE:L:UE%:E.'SPL'EIW:I>
 

30

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