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 MAINTENANCE DEVELOPMENT FOR MOLTEN-SALT BREEDER REACTORS

 
  

ffiofiert'--':Blumberg_ L

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The malntenance system of 'bhe pr0posed molten-salt breeder

reactors ‘Wlll be based upon the technology in.use and experience- galned

from the Molten-Salt Reactor Experiment.. The unit replacement scheme,
. long-handled tools, moveble maintenance shields,.and the meens for

hendling contam:ma.ted equipment will.be .similar.for many operations.

. The techniques must be. mproved and extended and new techniques must
e ;,_:,fhe develcoped for maintaining some of the larger more radioactive
=" “components :of the breeder reactors.  Remote welding is needed for
- major component replacement.: Methods must be:.available for replacing
. ..the core and for the repair: of heat exchangers. _ Fmally, a genereal
""development and- design surveillance program-will be: req_ulred These |

 

 

 

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~ This document con%nins mformation of a prellminary nature und ‘was preparedr S

~ primarily for internal use at the Ock Ridge National Loboratory.” it is subject N

" to revision or correction and therefore does not represent o final report. The ' .
information .is not to be abstracted, reprinted or otherwise given public dis- s
semination without the npproval of the ORNL potent brqnch Leqal cmd Infor-f
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~LEGAL NOTICE

 

 

This report was prepared as an nccuunt of Govarnment sponsored work. Neither the Unlfcd States,

nor the Commission, nor any person 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 centained in this repert, or that the use of

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B. Assumes ony liabilities with nspect to fhe use of, or for domages 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 smployee or

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or his employment with such contractor.

 

 

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TABLE OF CONTENTS

Page
INTRODUCTION ' | 1
PHILOSOPHY OF MAINTENANCE 1
DESCRIPTION OF PRESENT TECHNOLOGY 2
MSRE MAINTENANCE EXPERIENCE AS RELATED TO MOLTEN-SALT BREEDER k4
REACTORS

DISCUSSION OF ANTICIPAEED PROBLEMS ' ' 5
| Piping Cofinections and Vessel Closures >
Replacement and Repair of Components T
Large Component Replacement 8

Core Replacement 8

Heat Exchanger Replacement 9

Repair of Components ' 9
Radioactive Component Examinetion 10

Improved Performence . | 10
INCREASED RADIATION LEVEL 11
GENERAL: MAINTENANCE DEVELOPMENT AND DESIGN SURVEILLANCE 11
PROGRAM COSTS AND SCHEDULE | 13

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INTRODUCTION

One of the basic differences between & molten-salt reactor or any
circulating-fuel reactor and the more widely utilized, solid or stationary
fuel reactor, is in how each contains fission products. One of the
important ramifications of this difference is in the area of maintenance.
The circulating fuel deposits some fission products in the reactor system,
drain tanks, offgas system, and the fuel processing system. Questions
neturally arise. Is it feasible to maintain such radioactive systems?
From our .experience with Homogeneous Reactor Experiment-2 (HRE-2 or HRT)
and .the Molten-Salt Reactor Experiment (MSRE), .the answer is an unquali-
fied yes.  Another question is, "Are such systems much more expensive to
maintain than solid fuel systems?" This question cannot be adequately
assessed becsuse of the complexity of the economies, but when one accounts
for the costs involved with repla01ng spent fuel elements, the answer is
no longer clearly in favor of the solid fuel system. It may well be
cheaper to maintain a circulating fuel reactor. '

A reference conceptual design for a 1000-Mw(e) molten-salt thermal
breeder reactor (MSBR) is described in ORNL-3996.l1 ‘The progrem for
developing the breeder through & molten-selt breeder experiment (MSBE) is
summerized in ORNL-TM- 1851.2 The following report describes & program
of development of methods and equipment for maintaining the radioactive
equipment of the MSBE. A major criterion for the program is that only
scaleup of the equipment should be necessary to satisfactorily maintain
the larger MSER.

PHILOSOPHY OF MAINTENANCE

The prime philosophy of maintenance of failed radioactive components
in molten~salt breeder reactors is simply stated as remove, replace and
repair or discard. We do not plan to repair those components in place.
They will be removed and replaced by & new or repsired unit and then will

. be repaired in specially equipped facilities or discarded depending on

the size and cost of the unit,  the difficulty of making the repair, and
the value: of the repaired unit. . This philosophy was adopted because it
appears to be the best way of maklng repairs quickly to get the plant
back into operation.

One of the mgst 1mportant factors which affects this mesintenance
phllosophy is the effort to make ‘the components réliable so repairs
are infrequent and discard not prohlbltively expensive. The program for
engineering development will place emphasis on establishing & predictable
and practlcal life for the components permitting us to establish a .
philosophy which includes discard .of the failed component if it is too
radiocactive for direct or semi-direct masintenance. ZEmphasis also will be
placed on repid replacement to reduce the down time for the system.

~The reactor vessel, the heat exchangers for the fuel and blanket
systems, the drain tanks, and the pump rotary elements will become so
radioactive that they will normally be discarded. It may be necessary
 

 

to disessemble and examine & failed component to determine the exact

cause of failure but this would not require that the component be re-
assembled. Possibly the failed component will be stored in the same

cell with the reactor to await some decay before examination.

The offges System and the chemical pfocess plant will contain manyl
of the fission products and will be very radiocactive. Where practical,
components of these systems will be deconteminated and repesired with a -

minimum of shielding, otherwise they will be discarded and a new component

will be installed.

The coolant system ordinarily should not be very radiocactive. There
is some activation of the sodium but with the system drained the residual
activity should be low enough to permit direct maintenance. The pres-
sures in this system are maintained above the opposing pressures across the
tube walls in the fuel and blanket heat exchangers so that any leakage
‘would be out of the coolant system. This arrangement should prevent con-
"tamination of the coolant salt with fission products. If perchance
fission products should get into the coolent system, then some decontamine-
tion would be necessary before maintenance would be possible.

The steam and turbine generator system should never become radioactive
since it is separated from the prime sources of activity by the coolant
system and from direct neutron ectivation by the shielding of the cell
walls. Conventional methods of direct meintenance will be used here.

In this program we shall concentrate on developing the techniques
for maintaining the highly radicactive components such as the core, pump,
drein tenks, and heat exchengers.

DESCRIPTION OF PRESENT TECHNOLOGY

The present status of the technology of maintenance of molten-salt
reactors is largely embodied in the maintenance scheme for the MSRE.
Methods and equipment in use at the MSRE are based on extensive experience
gained on the asqueous Homogeneous Reactor Experiment No. 2. Experience
with remote maintenance of the radiochemical plants at Hanford and
Savannah River, repair of the Sodium Reactor Experiment, and remote dis-
mantling of various reactor assemblies contributes in a general, and
often important wey, to the development.

To achieve a practical level of maintainability, uniform methods are
- provided for gaining access to, removing, and replacing ell of the equip-
ment in the radiocactive areas of the reactor. At the MSRE, this includes
the reactor cell, the drain tank cell, the offgas system and.the chemical
process system. The general philosophy is to remove & failed component
and replace it with an interchangeable spare. A considerable emphasis

was placed in design and construction phases on meking components reliable
so that the need for replacement is infrequent and discarding failed com-
ponents is not prohibitively expensive. However, facilities have been
provided for some some decontamination and répair of equipment.

 

 

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Reduced to fundamentals, the MSRE is & collection of component parts
which are capasble of being disconnected and reconnected remotely. Access
to these units is provided through removeble shielding sections that make
up the roofs of the vaerious cells. A portable maintenance shield is in-
stalled over the component, the roof section is removed, and long-handled
tools -are used to do the manipulations that are required. This portable

shield provides 12 in. of steel for shielding (attenuation factor 10 -10°),

tool access holes, lighting, and maneuverability. The long-handled. tools
are, for the-most part,.simple, strong, and single purpose. Periscopes
and lead glass windows in the shield provide viewing in the work arees.

A1l preparetions for removel are done'completely with the portable shield.
After large components are prepared for removal with the same technique,
they are removed from the installed position by means of .a crane operated
by personnel inside & shielded.control room with closed-circuit television
and liquid-filled windows for viewing. Small components are removed by

“use of suitable transport shields. A hot-equipment storage cell and a

decontamination cell can be reached by the crane so that contaminated - -
equipment can be disposed.ofvconveniently.

The ability to completely disconnect a particular component is basic
to this system. The disconnects must be remotely operable by the long-
hendled tools. They must be reliable both for the service conditions end
for the high redistion and in some cases must satisfy nuclear safety
considerstions of containment lesk tightness and leak detectability. A.
number of different disconnects are used at the MSRE for the various
epplications:. Almost all the piping in such auxiliary systems as the
offgas, lubricating oil, air, and cooling water systems have standard
ring joint flanges, with minor modifications. Special designs were used
for lesk detector tubing, thermocouple, electrical and instrument leads.

The disconnects for the 5-in. sched-40 piping are called freeze
flanges. They are large diameter, unheated and uninsulated flanges. The
clamping device, a U-shaped spring clamp, and the ring gasket seal are
near the perimeter and operate st a much lower temperature than the
bore of the pipe. The oversize flanges take up much space, have large
temperature gredients, and require large clamping forces. Much develop-

- ment was required to obtain the desired serviceability and malntalnablllty,

but five pairs of. flanges are now in service at the MSRE and they work
well. While they have never been broken and remade remotely in a radia-
tion field, the long-handled tools.which were developed for this purpose
were used for the assembly of. the reactor and their operabllity was -

'established to that extent. .

© The draln and storage system of the reactor is connected with 1-1/2—1n.

”sched—ho piping. It is planned t0 maintain this system by remotely cutting
 and brazing these lines.. The ‘equipment to accomplish this is on hand

and has been . exten51vely tested in mockups, but not yet in & radioactive
situation. : : : : ,
 

The maintenance philosophy' in use for most parts of the MSRE is to

- replace a failed, conteminated unit with a spare component. Spares are
built in jigs to essure interchengeebility. Pieces that are smell and:
not too radicactive are partly decontaminated and repaired by direct
contact with the help of local shielding to reduce the radiation level.
‘To satisfy the requirements of the MSRE, a constant:review was made
of the component and instellation design to insure that it wes meintein-
eble and, where necessary, mockups were constructed to assist in guiding
the des1gners. ,

)

MSRE MAINTENANCE EXPERIENCE AS RELATED TO MOLTEN-SALT BREEDER REACTORS

The MSRE has been successfully operated end maintained during the

. past year and a half. Severasl different items of equipment have been
repleced or repaired and several difficult operations were completed which .
were unanticipated in our planning for maintenance. To evaluate our ex-
perience in the light of the needs of the breeder, one may divide &ll of
the equipment of the MSRE into two classes. The first class includes

all the large salt-containing vessel and piping complexes. These are the
three major components in the reactor cell, the drain tanks and. the
interconnecting piping. While these complexes have the most difficult
maintenance jobs, they are also low frequency jobs. We have not yet.
meintained these large components. The second class includes all of the
rest of the removable equipment; items such as control rods, heaters,
valves, auxiliary lines, offgas component, etc. This is where most of the
maintenance work will be done because of the higher failure rate. The
maintenance capability has been clearly demonstrated for the second class
of equipment. Based upon many hours of actual work experience, & detailéd
knowledge of the magnitude of the radiation and contamination levels, and

a8 first hand knowledge of the ability of the system to handle unanticipated
problems, we meke the following statements regarding MSRE maintenance.

1. We believe that the demonstration :of maintenance of the major fuel
components (i.e., that which we have not yet done) is merely e matter of
doing it when the occasion arises. It presumsbly will be more difficult
and will require more time but nevertheless is well within our capsbility.

4

2. The MSRE maintenance system possesses several'attractive;qualities;
including reliability, simplicity, ruggedness and flexibility.

3. There are two wesknesses of the system which have been recognized.
These are the levels of radiation. around tool penetrations end the method
of disposing of contaminated equipment. These are wesknesses that can
be improved quite readily through design and procedural changes.

k. The MSRE can continue to supply informetion of value to the MSBR
program. It is planned to conduct experiments, perform maintenance tasks
-and gather data, during the remainder of the operating life of the MSRE.
Projects of this nature include demonstrating the replacement of & major
-component , mapping the gamme radistion levels in & portion of the reactor
cell and the offgas system, and continuing the plotting and analysis of
in-cell radiation levels. The possibilities of decontaminating components
of the fuel and. offgas systems to & level which would permit direct main-
tenance will be investigated.

Q.
 

-}

5. We believe that the requirements of the MSBR can best be ful-
filled with a system baséd generally on the one in use &t the MSRE.
The equipment must be modified, of course, to meet increased require-
ments in performance and in size, weight and radiation capabilities.
Finally, it must be modifled to reflect the specific de51gn problems

'of the breeder.

DISCUSSION OF ANTICIPATED PROBLEMS

We propose- -that the system for maintaining the radioactive components
of the MSBR be based on the technology and experience of the MSRE. The
overhead access, movable maintenance shield, separable components and long
handled tools to accomplish in.cell manipulations will be retained. We
know that some new technigues must be developed and existing techniques
must be improved. However, the details of the maintenance system must be
based upon a more detailed design of the reactor than now exists. The
MSBR will be larger. The pumps, heat exchangers, and reactor vessel will
be larger and heavier, so the maintenance equipment must have increased
capabilities. For example, the reactor vessel for a 250 Mw(e) MSBR module
weighs - 71 tons compared to @ tons for the MSRE. Radiation levels will be
higher, so the shielding must be increased. The power level in an MSBR -
module is higher by a factor of about 80 and the residual activity after
the fuel salt is drained would be correspondingly higher. While this
would require some additional thickness in the portable maintenance shield,
the importent effect will be the attention which must be given to the cracks
around the tools at penetrations. Economic factors and some nuclear
requirements dictate & compact design for the fuel, blanket, and some
auxiliery equipment and systems. This tends to make maintenance more dif-
ficult. Finelly, economic considerations and program objectives place
more emphasis on efficient maintenance. The following is a discussion
of the places where problems are anticipated, proposed solutions to the
problems, and the development required. This discussion is concerned pri-
marily with the large breeder reactors. The MSBE will have the same
problems but on a smaller scale and the research and development will
in most 1nstances be done on MBBE scale. S .

Piping Connectzons and Vessel Closures -
- The unit replacement séheme‘requireS'piping connections and vessel -

closures that are highly relisble in service and are capable of being
maintained remotely. In the MSBR these .connections will be needed in the

- main fuel and blanket recirculation systems, the drain and storasge systems,
~the offgas. system, the fuel and-blanket processing systems, end in the

parts of the coolant and other suxiliary systems that must be located in
radicactive arees. Vessel closures will be needed on the reactor and on
the fuel and the blanket heat exch&ngers. For lines no larger than those
in the MSRE and. instelled in areas where the ambient temperature is below
about - h00°F, use can be. made of equipment and techniques that will have .

been proven at the MSRE. However, the design of the MSBR imposes three

new difficulties: (1) The 2h~in.-diam piping is considerably lerger than
has been used with remotely disconnectable joints. (2) The 1150°F ambient
 

 

 

6

temperature proposed for the reactor cell is con51derably higher than has
been used in the past. (3) No vessel closures approaching the size
needed for the MSBR have been developed for remote operetion and elevated
temperatures. _

In the reference design of the MSBR, six connections are required in
the reactor cell in the lerge lines that join the reactor vessel to the
heat exchangers and the heat exchangers to the coolant system. Remote
welding, we believe, is the best way to make satisfactory joints in those
lines. Welding also appears to be the best way of making reliable
- vessel closures and it is possible thet the design of & vessel closure seal
can be made fundamentally the same as the piping connection. While con-
siderable development will be required, the program seems to be straight-
forward and the goal reasonably attainable. Development of satisfactory
flanges for those lines would also be difficult and probably would require
considerably more long-term testing. Once developed for the larger
closures, remote welding can be used on the smaller lines in all the
redioasctive systems. The development will be of considersble value to the
entire nuclear 1ndustry. : -

Some development has already been done on remote weldlng. Atomics
International Division of North American Aviation, Inc., has equipment
for remote welding of small tubing for repairing heat exchangers. They \
are deeply involved in esutomatic welding development including the join-
ing of 4O-ft-long pieces of k-in.-diam pipe for deep-well casings by
welding from the inside.* The PAR Project advanced the technology to the
point of completing many seal welds and test welds on large and small
pipes with remotely operated equipment.s The pipeline industry has
automatic equipment that will meke high quality welds on 30-in.-diam pipe. .
North American Avietion, Inc., has used the "skate welding" method for '
fabricating missiles where the welding is controlled from & remote
location.®

The welding development will be & Joint effort of the Materials
Development Program and the Maintenance Development Program. It will
consist primarily of:

1. designing and qualifying the weld joints,

2. supporting the improvement or modification of existing
automatic welding apparatus,

3. adding the jigs and fixtures required to align and hold
‘the pipe or vessel and the masnipulative devices to :
operate the torch, and '

L. meking test welds to improve the technlques until good
~ welds can be made con31stently. |

The maintenance development will also 1nc1ude the devices for cutting

the seals and machining the ends to the specified configuration. A joint
design using a sesl weld with & mechanical clemping device to provide

the strength is a possible alternative to the multi-pass welding of thick
wall members.
 

 

 

 

F'C ’
i

Development of techniques for inspecting and repairing welds in radio-
active areas must accompany the effort on remote welding. Visual inspection
via closed circuit television and dye penetrant and ultrasonic testing
techniques appear to be applicable, whereas radiography does not appear

_ feasible. An intensive study of the joint configuration may reveal a

design that will allow complete confidence in the joint without the
detailed evidence of a totally inspected weld A leak detectable buffered

"301nt is one example of such a de31gn

One arrangement for maklng welded connectlons would involve installing
at each joint a built-in track or .guide, upon which a wheeled or geared
carriage containing weldlng, cutting, and inspection heads would ride.

The track would provide accurate positioning in the radial and circum-
ferential directions. Long-handled tools would lower and install the
various heads upon the built-in tracks and would provide means for routing
purge, power, coolant, and instrument léads. Remote television or optlcal

'eqnlpment could be used to monltor the automatlc control of the process.

The development effort Wlll con51st of at least three stages of
testing: (1) bench tests of automatic welding equipment to establish the
basic parameters of control of the welding process such as voltage,
current, purge and coolant. rates; (2) tests of welding, cutting, inspection,
and repair on full-size plpes and vessels using the preinstalled guides
and remote controls; (3) fully remote shakedown of reactor grade equipment
and procedures. The magnitude of the supporting design effort would depend
upon the success of the tests in the two early .stages. The development
work will be done on Jjoints of the sizes required for the MSBE,making certain
that the results can be applied to the large joints of an MSBR. Service
tests must be made on all joints in the various systems. Equivalent life
cycles of these joints will be run to establish compatlblllty of the Joint,
its method of operatlon and its service requlrements

While the remote weldlng is the flrst—llne approach, some study will
be made of two additional approaches. The feasibility of remotely dis-~
connectable mechenical joints for the intended service will be investi-
gated. Also'a braze seal with mechanical support will be considered for
use in the auxiliary systems in the reactor (both salt and non-salt

 carrying) and as a backup to remote welding. - It is well to note that

remote welding and remote braZing‘ere techniques rather than deslgns_forf
specific applications. As such, they have a wide variety of. potential

. uses in radiosctive environments for incorporation in the orlglnal designs
~and for modifying or repalrlng exlstlng equlpment.

_Replacement'and.Repglr of Components - -

In keeping with the 1¢fig4range'goals eflthe program, we must develop

 the ability to maintain the reactor quickly to avoid down time penalties
‘and efficiently to lower the overall maintenance costs. The present

plan of maintenance of radioactive systems cells. for replacement of a
failed component with another like unit end then either repairing or dis-
carding the failed component. The following is a discussion of the prob-
lems of this plan.
 

 

Lerge Component Replacement -

To replace eny lerge unit we do the following basic operations.
Separate the unit from its connecting lines by remote cutting. Using
long-hendled tools, detach all minor connections and prepere for lifting.
Remove the unit to & previously prepared area in the cell or take it out
of the cell to some other storage area. The latter choice involves the
transport of a very large, very radioactive component, shielding of
meintenence and non-maintenance personnel, and control of contamination
in ereas which are used daily. A new unit must then be installed end
reconnected to the piping by remote welding. _

Development of the means for this capabllity will begin es a deslgn
study. The sizes, weights, and expected radietion levels of the components
will be studied along with the various handling methods thet are available.
At the MSRE, measurements will be made of the effectiveness of flush salt
operstions, radiation levels will be measured and experience will be gained
in handling radicactive components. From this experience, tool designs,
shielding requirements, procedures, and requirements for equipment such
es cranes, supports, in-cell jacks, and slignment devices will be speci-

fied. Questionable areas will be mocked up and tested. For instence,
it is expected that tests must be run on equipment to align large vessels
and equipment to effect the necessary displacements. Tools and techniques
must ultimately be tried and demonstrated in MSBE size equipment and
finally on the components of the Engineering Test Unit.

Core Replacement

In the MSBR of reference design the core is an assembly of graphite
fuel tubes or cells that are joined to Hastelloy-N plenums. First, each
graphite tube is Joined by e threaded and brazed joint to a Hastelloy-N
tube. The resulting elements are assembled into & reactor core by
screwing, welding or brazing the Hastelloy N tubes to the plenum heeder.
The core assembly is then installed in the reactor vessel and connected
to the fuel entrence plenum by a gasketed or seal welded joint. Finally,,
the top head is installed to close the reactor vessel. . o

Means must be provided for replacing the core if one or more of the
grephite elements breasks or develops large lesks. Problems of contain-
ment, shielding, removal of fission product decay heat, etc. influence
the choice of a method for safely remOV1ng, transportlng and dlsposlng
of the core. :

One method calls for replaclng the entire core and reactor vessel
assembly and for storing the used unit in & morgue within the resactor
‘building. This scheme would use the vessel for containment of the
fission products and would ease some of the problems of removing decey
heat, transporting and storing the core. With this concept the reactor
vessel could be of all welded construction, thereby eliminating the need
for large, remotely assembled vessel and plenum closures.

5
 

 

 

Geveloped.

 

: - A second proposal calls for remov1ng the core assembly from the
reactor vessel, installing a new one and discarding the old. This method.

- requires the large closures and may also make solution of the other

problems more difficult. An early study will be made of the problems

‘and the economics of the two methods, & choice will be made for use in

the reactor design, and equlpment will be developed for accomplishing -
the maintenance.

 

aHeat‘Exchanger Replacement

To repair a leek in one tube_of'a heat exchanger,one must do the
following: ,

1. open the vessel to gain access to the tube sheets,
2. find the tube which is leaking,

3. ' seal the ends of the tube,

4. Teseal the'vessel.;

The reference design heat exchenger is not well suited to repair because
of very poor accessibility to the tube ends. Many compromises would have
to be made in the design of the heat exchanger to meke it more easily
repairable.

The first choice for a maintenance method for the radiocactive
heat exchanger is the replacement of the entire heat exchanger bundle.
This requires the removal of the pump rotary element from the pump bowl,
opening the Joint in the piping to the core, opening the vessel closure
in the excheanger shell and disconnecting severel small service lines.
Then the heat exchanger would be removed to an examination facility
or to a storage area. The capability of replacing the entire heat ex-
changer must be available and the. necessary steps to do so. will be

S

.Repalr of Components

Components that can be. ea51ly decontamlnated w111 be repalred and

"reused as spere parts. Components that can be repaired by use of simple

tools behind a small emount of shielding or are small enough to be handled

~in & small hot - cell mey also be repalred for reuse.

RPN

Whether to repair or discard the radloactlve components from & large

.:1breeder plant has not been firmly esteblished but discard is the first
 choice at this:time. Studies are required of the facilities for meking
~repairs and of the costs in arriving at s firm decision. Measurements.

will be made of the effectiveness of flush salt operatlons and decontamina-
tion procedures in reducing the. act1v1ty of contamineted parts from the
MSEE. The levels of neutron-lnduced radloact1v1ty will be calculated.
Meking use of these data, some designs will be made of hot cells and the

‘equipment for making the repairs. This involves the application of hot
 

 

10.

cell techniques to tasks that are ordinarily done in a heavy equipment
shop. Total costs of meking the repeirs will be estimated and compared
with the wvalue of .equipment that would be salvaged. Results of these
studies will be used in specifying end developing equipment end facilities
for the MSBE. .Experience with that reactor w111 strongly influence what
is done for large breeder reactors. '

Although our meintenence proposals are. based on.removel and replace-
ment of major equipment in the plant, some attention will be given to
- in-place repair. Studies will be made of core designs and heat exchanger
designs to better determine whether in-place .repair.of the graphite fuel
cells and the heat exchanger tubes can be made practiceble.

Radioactive Component Examination'

The experimental nature of the MSBE requires that careful examination
be made of any failed component to determine the cause of failure so the
cause can be corrected in future components. An examinstion cell will be
required at the reactor site and it must at least be equipped to dis-
mentle equipment so that parts can be sent to other hot cell facilities
for detailed examination. Depending on the types of failures, repair of
-some radiocactive components could also be demonstrated in this cell.

Specifications will be prepared for the facility and the equipment
required. Some development of very speciel equipment is anticipated end
procedures will be prepared for operating the equipment.

Improved Performance

In e power reactor the importance of meking repairs quickly must be
taken into account. In this respect the record of the radioactive ’
maintenance of the MSRE has been encoursging in spite of severel negative
elements. Because it was an experimental reactor, there was little effort
to provide anything above the minimum level of maintainebility. The
tight time schedule and low budget did not ellow much testing and
practice at the reactor, and the very crowded condition in the resctor
cell is not conducive to efficient maintenance. The handling of components
where meintenance wes anticipated such a&s control rods, space coolers,
valves, heaters, and piping spool pieces has all gone smoothly. The ability
to utilize existing craft forces W1th modest training was encouraging. :

The e is no doubt, however; tham;the'performance can be improved.
Among the items that will be studied sre the increased use of shielding
to cut down radietion levels, better mobility of the roof shield and
the maintenance shield, and,perhaps more than one maintensnce shield. Of
course, in the design of all the tools, components and equipment, the speed
of the completion of the operstion will be considered.

et e - - e

Q.

59

O,

 
 

3 C '

11

INCREASED RADIATION LEVEL

 

A general area for study arises from the increase in the radiation
level which is expected in the MSBR. The geometry for shielding mainten-
ance personnel is shown in Figure 1. The radietion level where personnel
will operete the long-handled tools arises from sources.in the reactor
cell end varies inversely with the distance and.the attenuation factor
of the shielding. Gamma levels at the MSRE as measured by in-cell ion
chambers ,indicate -thet the shleldlng provided there is adequate. When
the reactor is operating at T Mw, the level 'is 60,000 r/hr. This drops

to 4000 r/hr immedistely after draining the fuel. During a recent
shutdowvn the radiestion level in the cell was 2000 r/hr seven days after
shutdown while maintenance operations were in progress and the work.
was asccomplished without undue exposure of personnel.

For the MSBR, the raedistion levels will be considerably higher.
This will require additionel 'shielding. A study will be made:to evaluate
the source strength during shutdown and methods for reducing the radia--
tion levels, such as using e flushing materiel, decontamination systems,
end fluid shielding (perhaps a molten selt with a low melting point).
Also involved with en increase in rediation ere details of the design
of the long-handled tools and the penetrations through the meintenance
shield. Internel voids in the tools end cracks in the penetration
represent radiatlon 1eakage paths, and effort must be taken to avoid
then. : ,

_ Development. of better protectlon of the maintenance crew will begin
with an analysis of'date concerning the rediation levels at the MSRE
and the experience with maintenance there.. This information will then
be applied to analysis of. the radiation levels in the MSBR and the MSBE.
Then the designs of speciel shieldlng and tools will be studied and’
1mproved to provide the necessary shielding. Some new devices or new
approaches ‘to special shielding problems cen be expected to evolve, and
mockups will be built to test them.

GENERAL MATNTENANCE mmfopm AND DESTGN SURVETLLANCE

A very 1mportant part of the maintenance development progrem involves

~;following the design of the reactor to meke certain that the maintenance
_“frequlrements gre satlsfled.end then designing and testing the special
- tools‘to do & wide ‘variety of: maintenence operations. . This activity is
- entirely concerned with the breeder experiment; however, the experience

geined end the ‘general technzques developed are expected to. be useful for
the full-scele’ reactors.\»m ST ,
 

12

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Shielding Configuration for Maintenance Operations.

 

 

 

 

 

: -Aa ' 4&

S ey

 

 

Figo 1-
 

 

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13

This activity will be carried out in about the following sequence.

1. Review preliminary flowsheets and equipment and plant designs
to mgke certain that the meintenance requirements are integrated into
the design of the plant. Items of special importance include the
shielding arrangement with emphasis on special shielding for maintenance,

' the shielding penetrations, the component support structures, the cranes

end other equipment for handling radioactive components, and the view-
ing devices. ,

2. Prepare proposals for all maintenance operations.  Compile lists
of problems, tools, and sPecial‘diSCOnnects.

3. Review final designs as they are being made. Revise maintenance
requirements as necessary. ,

4, Build required speciel tools, Jjigs and-fixtures. Test them in
full-scale mockups and on the Engineering Test Unit. o

5. Follow the'construction of the MSBE and the installation of
the equipment to be certain that malntenance is properly considered
if changes are made. L

6. Prepare.proceduresrfor'maintaining:the equipment in the MSBE.

PROGRAM COSTS AND SCHEDULE

A preliminary estimate of the cost of the maintenance development
program for the MSBE is shown in Teble 1. The activities are fitted into
the schedule proposed in ORNL-TM-1851 (Ref 2) for designing and building
the plant. Although the meintenance considerations influence the design,

there is only one crucial development. The feasibility of remotely
- welding the joints in the main fuel, blanket, and coolant lines and ves-

sels or some suitable alternative must be established before the design
can be completed. The program is designed to demonstrate a satisfactory
Joint by the end of FY 1970, although congiderable testing and improve- .
ment of equipment and techniques are expected'to follow the demonstration.

In the other areas we expect to establish maintenance requirements
end provide convincing evidence of the practicality of the maintensance
schemes by the end of FY 1970. However, the development of meny of the

B tools and procedures will be accomplished whlle the plant is being built.
Table 1. Estimate of Costs for Maintenance Development Program

($ Thousands) 

 

 

 

FY 1968 FY 1969 FY 1970 FY 1971 FY 1972 FY 1973 FY 1974 FY 1975
Remote Welding 120 230 © 250 180 150 100 70 10
Core Replacement and Repair 60 160 160 100 1100 - 50 30. 30
Maintenance of the Heat 60 100 100 60 60 60 30 30
Exchangers and Other o -
Components ‘ _
General Maintenance Develop- 60 120 120 60 60 60 60 30
ment and Design Surveillance - ‘ | | -

300 610 630 400 370 270 190 160 -

| ( )q o C) f-*

T

 
 

 

 

 

£

-k

s
44 REFERENCES
1p, R. Kasten, E. S. Bettis and R. C. Robertson, Design Studies of

1000-Mw(e) Molten-Salt Breeder Reactors, ORNL-3996 (August 1966).

2R. B. Briggs, Summary of-Objectives and a Prdgram of Development of
Molten-Salt Breeder Reactors, ORNL-TM-1851 (June 1967). |

3g. C. Hise, F. W. Cooke and R. G. Donnelly, "Remote Fabrication of
Brazed Structural Joints in Radioactive Piping," ASME 63-WA-53
(September 1964).

“E. H. Seidler, "Welding," Advanced Fabrication Technology, Atomics
International (Brochure).

5E. H. Seidler, Layout and Maintenance, WCAP-1104, Vol. IV, Part 1
(March 1959).

®R. R. Irving, "Welding Reacts to New Demands," Iron Age 191(1k),
pp. 83-90 (April L, 1963).
 

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17

.Internal Distribution

' MSRP Director's Office

K. Adams

M. Ademson.
G. Affel

G. Alexander
F. Apple

F. Baes

M. Baker

J. Ball ~
P. Barthold
F. Baumen
E. Beall

‘Bender

S. Bettis

F. Blankenship

E. Blanco.
0. Blomeke
Blumberg
G. Bohlmenn

J. Borkowski -

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Braunstein".'-:

A. Bredig

B. Briggs

R. Bronstein -
D. Brunton

A. Canonico
Cantor

L. Carter - =

‘I. Cathers

M. Chandler
L. Compere
H. Cook
T. Corbin

L. Crowley - .. .. -
M. Dale
G. Davis

J. Ditto
S. Dworkin

‘R. Engel

P. Epler
E. Ferguson
M. Ferris

P. Fraas - - .

99.
100.
101.
102.
103.
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106.

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108.
109.

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18

145. C. J. McHargue -~ 171. 0. L. Smith

146. L. E. McNeese 172. P. G. Smith
147. A. S. Meyer o 173. W. F. Spencer
148. R. L. Moore o 17T4. I. Spiewak
149. J. P. Nichols - . 175. R. C. Steffy
150. E. L. Nicholson o | 176. H. H. Stone
151. L. C. Osakes : 17T. J. R. Tallackson
152. P. Patriarca | 178. E. H. Taylor
- 153. A. M. Perry 179. R. E. Thoma
15k, H. B. Piper = 180. J. S. Watson -
155, B. E. Prince 181. C. F. Weaver
156. J. L. Redford. | 182. B. H. Webster
157. M. Richardson o 183. A. M. Weinberg
158. R. C. Robertson 184. J. R. Weir
159. H. C. Roller - - 185. W. J. Werner
160. H. C. Savage - 186. K. W. West
161. C. E. Schilling S 187. M. E. Whatley
162. Dunlep Scott o 188. J. C. White
163. H. E. Seegren | 189. L. V. Wilson
164. W. F. Schaffer. - 190. G. Young
165. J. H. Shaffer 191. H. C. Young |
166. M. J. Skinner 192.-193. Central Research Library
167. G. M. Slaughter 194.-195. Document Reference Section
168. A. N. Smith 196.-205. Laboratory Records (LRD)

169. F. J. Smith 206. Laborsatory Records (LRD-RC)
170. G. P. Smith , o

External Distribution

- 207.-208. D. F. Cope, Atomic Energy Commission, RDT Site Office
209. A. Giambusso, Atomic Energy Commission, Weshington
210. W. J. Larkin, Atomic Energy Commission, ORO _

211.-225. T. W. McIntosh, Atomic Energy Commission, Washington
226. H. M. Roth, Atomic Energy Commission, ORO |

227.-228. M. Shaw, Atomic Energy Commission, Washington
229. W. L. Smalley, Atomic Energy Commission, ORO. = .
230. R. F. Sweek, Atomic Energy Commission, Washington

231.-245. Division of Technical Informastion Extension (DTIE)

- 2h6. Research and Development Division, ORO -
24T.-248. Reactor Division, ORO

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