‘*‘5"% : | 'l_*o AK mDGE NATIONAL LABORA‘I’ORY "';__;:‘_‘ operated bY TN UNION CARBIDE CORPORATION Lt . - for the - -:r' o U S ATOMIC ENERGY COMMISSION '__' <~ ORNI. TM"' 1859 ', CO{?Y;NO_.} 231 MAINTENANCE DEVELOPMENT FOR MOLTEN-SALT BREEDER REACTORS ffiofiert'--':Blumberg_ L w 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 | THIS DOCUMENT A N\J IN!"EI T Ib SF P - i A Frr TE) THr. A E C A{; ' AT IE - _rf-programs are’ described a.nd the:n: cost is est:.ma.ted. T ~ 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 mation ConfroI Depcrtment SRR - . o 3 B’-’EN REVIEWED, PISTRIDTION OF THIS DOCUMENT (S UNLIMITER ol P ~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 any information, apparatus, mcthod, or pfoéys# disclosed in this ropon may not infringo' privately owned rights; or 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 _contractor of the Commission, or employee ‘of such contractor, to the extent that such -mployce " or controctor of the Commission, or omployeo of such contractor prepares, disseminates, or provides access to, any information pursuant to his employment or contract with the Commission, or his employment with such contractor. i)l' ) (@ N Ay L A iii 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 [ od or 1 o tion, eXpr 1 o, - ppars gl e ed inmthia report may not mfnnge R mpl 88, OF uelulne::e&m s acinae e - pr - . : s res - s ron . r for damage i any Infor®8 s ot o he weo o, @ e o ' - Eprivately ¢ riflmmbmueu with respect o e o mm" < - < “3 > e i et o comm‘t::cwr to extent {hat . On, u . o . o ‘pemmi"on noyee of such ¢ T s BT < - ot o “ci::l;x:;s:ran. or amploye: : h'i:c:mploymanto b .mmmn provi rc:f!:b;‘ any jnformation np;r::; . ! e e th such €0 . . o fiese W",:s:glm or his employment Wi wuch o8 | it the Commissiots . iSTRIBUTION OF THis DOCUNERT 5 OUNOIMITED - - L e ol - v, it et et e repen e et = o \(V he e (fi’l\y ‘}; - " f » 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. ;- ’ e w3 ol e e e - Y, - -n'E»~ 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- “(N ’ ‘rk 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). e bt e i e e -w(m 3 O 1.-50. 51. 52. 53. sk, - 55. - 56. 5T. 58. 59. €0. 61. 62. 63. 6k, 65. 66. 67.-T1. T2. T3. L. T5. 76. TT. T8. 80. 81. 82. 83. 8L. 85o 86. 88, - 90. 91. 92. . 7;93., -9k, 96. 9T. 98. R. G. R. L. R. - C. J. S. W. H. S. M. E.. F. R. J. R. ,E. C. G. J. M. R. H. G. D. S. Ww. G. J. E. w. L. dJde. F. J. D. .s. A. J. E. D. L. -A. 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 - E.'dedl 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. 10k. 105. 106. - 107. 108. 109. 110. 111. 112. 113. 11k, 115. 116. 117. 118. 119. 120. 121. 122. 123. 124, 125. 126. 127. 128, 129. 130. - 131. 132, 13k, 135, 'T‘ f:l36. 137. . 138. 139. 1ko. 141, - 1bke, - 1h3, 1Lk, -133. H. J. c. R. H. W. A. R. _B. P. D. C. P. F. P. J. H. R.. T. H. - W. P. R. ‘M. M. C. T. H. S.. ‘A. J. c. i R. ‘A. M. “Re H' R. . C. C. C. R. H... H. C. . L. R. J. T. J. R. W. T. S. I. W. E. A. B. fP; I. N. G. E. D. E. L. W. CO F. K. mfitflbtfl??lfihfltflh’lb _‘ Friedmean Frye, Jr. “Gabbard . Gallasher. Goeller Grimes Grindell Guymon ‘Hannaford Harley . Harman Harrill Haubenreich Heddleson Herndon - Hightower Hoffman. Horton ‘Hudson - Inouye ' ‘He Jordan Kasten Kedl Kelley Kelly Kennedy Kerlin Kerr Kirslis Krakoviak Krewson Lamb Lane Lindauerrw' .Litman Lundin . Lyon . MacPherson MacPherson Martin Mathews Matthews McClung McCoy McDuffie McGlothlan 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 O, cr W At 8 . et 1. % s s i 1 6 e e w L e e e e