EnergyVol. 23, No. 7/8, pp. 619–627, 1998 1998 Elsevier Science Ltd. All rights reservedPergamon PII: S0360-5442(97)00101-1 Printed in Great Britain

0360-5442/98 $19.00+ 0.00

HISTORY AND PERSPECTIVE OF FAST BREEDER REACTORDEVELOPMENT IN JAPAN

SHUNSUKE KONDO†

Department of Quantum Engineering and Systems Science, School of Engineering, The University ofTokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan

(Received 1 May 1997)

Abstract—Research and development on fast breeder reactors (FBRs) started in Japan in the mid-1960s, leading to the experimental FBR JOYO which went critical in 1977. It was followed bythe prototype FBR MONJU which started operating in 1994. A 600 MWe loop-type demonstrationliquid-metal-cooled FBR (LMFBR) is now under study, especially emphasizing its safety andeconomy. A demonstration plant could be in operation several years after 2010. Japan expects asignificant fraction of world nuclear energy mix to be provided by FBRs by the end of the 21stcentury. This paper has detailed descriptions of the activities of the various Japanese organizationsinvolved in FBR development, as well as program funding and policy considerations. 1998Elsevier Science Ltd. All rights reserved

1. THE JAPANESE FBR DEVELOPMENT PROGRAM

The Japan Atomic Energy Commission (JAEC) has been promoting research and development (R&D)on fast breeder reactors (FBRs) since the mid-1960s and designated this R&D program as one of themost important national projects for nuclear energy development. The Power Reactor and Nuclear FuelDevelopment Corporation (PNC), which was established in 1967 by the government based on therecommendation of JAEC, started construction of the experimental FBR JOYO (100 MWt) in 1970,which went critical in April 1977. Currently, PNC continues to work on the prototype FBR MONJUwhich started operating in 1994.

JAEC issued its ‘Long-Term Plan for the Development and Utilization of Nuclear Energy’ in June1987 [1]. In this long-term plan, JAEC reiterated its long-range view that the FBR will be an essentialelement in future world nuclear energy supply systems, and that major energy consuming countriessuch as Japan should contribute to the development of innovative energy supply technologies such asthe FBR, which have great potential for expanding the non-fossil energy supply in the world. JAECconsiders that realization of a nuclear energy supply system based on the FBR is important for thepurpose of coping over the long term with increasing world energy demands, especially in thedeveloping countries, limiting the indefinite expansion of fossil-fuel consumption and thus the emissionof greenhouse-effect gases including carbon dioxide into the atmosphere.

JAEC recommended a plan for FBR development following MONJU in this long-term plan. Keyelements of the plan are as follows: (i) Successive construction of multiple demonstration FBRs(DFBRs) which will follow MONJU will be planned, aiming at the commercialization of FBRs duringthe period 2020–2030. The R&D for FBRs will be promoted comprehensively based on a long-termperspective for the FBR commercialization process and making the best use of the experiences gainedfrom design, construction and operation of each preceding reactor. (ii) Development of the DFBRs willbe promoted with the cooperation of governmental organizations and private sectors (electric utilitiesand manufacturers). Electric utilities will play a leading role in the design, construction and operation.The basic specifications for the first DFBR will be determined in the 1990s to allow the start of construc-tion in the late 1990s. Priority will be given to mixed oxide (MOX) fuel, taking into account theaccumulation of considerable experience with this type of fuel. (iii) Commercial FBRs will be equival-ent to or superior to light water reactors (LWRs) in terms of safety, reliability, operability and main-

†Fax: + 81 3 3812 1498; e-mail: kondo@sk.t.u-tokyo.ac.jp

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tainability and they will be economically competitive with LWRs. From this viewpoint, emphasis willbe placed on the R&D that may contribute to the realization of compact and high-performance plants.The first DFBR should be regarded as the first step in a multi-step process for attaining the character-istics required for commercial FBRs. It should therefore provide a good perspective of the additionaldevelopment required for commercialization. (iv) R&D on FBR fuel-cycle technology should be pur-sued in parallel with the development of reactor technology.

In 1992, JAEC started work on the revision of its long-term plan. This work was completed in 1995.The revised plan includes consideration of significant changes in the allowable conditions leading tothe development and utilization of nuclear energy in the world. Among other factors, these includedramatic changes in the political and economic system of Russia and other Eastern countries, and thestrong global commitment to the reduction of the carbon dioxide emissions. However, the plan con-cluded that the changing global situation does not significantly alter the need for the FBR based onlong-term perspectives for sustainable development of the world. The present paper summarizes theactivities of the various Japanese organizations involved in FBR development, as well as technicaldirections, program funding and policy considerations within this policy framework.

2. ORGANIZATIONS FOR FBR DEVELOPMENT

2.1. Historical overview

The Japan Atomic Energy Research Institute (JAERI) pioneered basic research for the FBR in 1956.However, JAEC issued in 1966 the ‘Basic Policy for the Development of Power Reactors’, in whichthe Commission maintained that the development of the FBR should be pursued as a national programwith the cooperation of concerned organizations in view of the importance of the development of thenuclear power reactor and its fuel cycle for solving Japanese energy problems. Along with this policy,the PNC was established in 1967 as a leading R&D organization for this program and the results ofFBR R&D activities accumulated by JAERI to 1967 were transferred to this organization. This transferincluded the conceptual design of an experimental liquid-metal-cooled FBR (LMFBR). The PNC hassystematically promoted R&D of FBR technology since 1967, setting the design and construction ofthe experimental FBR JOYO and the prototype FBR MONJU as milestones. PNC has also the responsi-bility of executing R&D on FBR fuel-cycle technology. It started operation of a prototype reprocessingplant for spent LWR fuel in 1977. Using plutonium from this plant, it has steadily built up the MOX-fuel fabrication capability for both the advanced thermal reactor (ATR) and the FBR. The presentproduction level is 5 tons (heavy metal) of fuel for MONJU per year. The development of reprocessingtechnology for spent FBR fuel was also started at the laboratory-scale test facility Process EngineeringTest Facility (PETF).

Utilities and manufacturers have accumulated know-how and experience related to FBR technologyby participating in this program, sending personnel and contributing to the manufacture of equipments.Their participation in the US Fermi LMFBR program from 1966 to 1972 also contributed to thisaccumulation. As a pioneer company for nuclear power generation in the electric utility group, theJapan Atomic Power Company (JAPC) has assumed responsibility for technical support and supervisionof the construction of the balance-of-plant part of MONJU. Based on the JAEC’s recommendationincluded in its long-term plan issued in 1987 that utilities should play a leading role in the design,construction, and operation of DFBRs, the Federation of Electric Power Companies (FEPC) has givenJAPC the task to design, construct, and operate the first DFBR. JAPC started the study of basic specifi-cations for the DFBR and of the definition of optimal concepts for commercial FBR plants. Based onthe results of JAPC’s work, the Federation decided in June 1990 to pursue the preliminary conceptualdesign study for the first DFBR [2]. The immediate goal of the study was to examine the technicalfeasibility of a top-entry loop-type reactor. It is expected that the basic design of the DFBR, whichwill serve as the basis for licensing applications to be conducted after evaluation of both the results ofthis conceptual design study and the initial operating experiences of MONJU.

JAEC also recommended in the 1987 plan that PNC should cooperate with utilities and industriesin promoting the commercialization of FBRs. In accordance with this recommendation, PNC has startedR&D for establishment of the technology base for economically competitive plants, in parallel withthose necessary for the completion of MONJU and for the assurance of fuel-cycle service for MONJU.The Ministry of International Trade and Industry, which has jurisdictional power to promote industrial

621History and perspective of fast breeder reactor development in Japan

activities in the nuclear energy field, has supported industry’s FBR R&D activity by subsidizing boththe feasibility studies and the demonstration test of innovative technologies and concepts for commercialFBRs. JAPC, PNC, JAERI, and the Central Research Institute for Electric Industries (CRIEPI) jointlyestablished the Steering Committee for FBR Research and Development in order to coordinate theseR&D activities for DFBRs among various organizations. JAEC set up the Advisory Committee on FBRR&D for the coordination and monitoring of the progress of FBR R&D carried out by these organiza-tions.

2.2. Current activities of each organization

2.2.1. PNC. Since its establishment in October 1967, PNC has developed JOYO and MONJU inaccordance with the basic policy of the government to develop indigenous FBR technology. Facilitiesfor extensive R&D activities, including those for the development and demonstration of large-scalesodium equipment and components, have been constructed at the Oarai Engineering Center. In the firstphase, the PNC’s effort was devoted to R&D activities for JOYO, for which criticality was first achievedin April 1977. In October of the same year, PNC started operation of JOYO at the rated power of50 MWt. In March 1983, the core was modified into a configuration more appropriate for irradiationtesting and with a thermal power output of 100 MW. Since then, JOYO has been extensively used forthe irradiation of fuels and structural materials. The test materials are evaluated in the post-irradiationexamination (PIE) facility annexed to JOYO. The capability of this facility has been significantlyupgraded for this work. The construction permit for MONJU was issued in May 1983. PNC started itsconstruction in 1985 and construction was completed in 1992. PNC has been performing extensivecommissioning tests, including core physics tests, starting from its first criticality. The tests have beensuspended since 1995 due to a sodium fire event caused by sodium leakage through a thermocouplesheath put into the secondary sodium pipe [3]. It will take a few years to modify the plant and restartthe operation.

PNC is now engaged in R&D for the improvement of design technologies for the reactor core, fuel,components and structure. This work includes extending the applicability of structural design codes tohigher temperature regions. Methods for safety analysis are also undergoing further refinement. PNCalso devotes considerable effort to the R&D of innovative technology such as artificial intelligence(AI), robotics, and advanced materials aiming at their utilization in future FBRs and fuel-cycle systems.Another important role of PNC is development of FBR fuel-cycle technologies, including fabricationand reprocessing of fuels for JOYO and MONJU [4]. PNC started operation of the FBR line in thePlutonium Fuel Production Facility (PFPF) in 1988 for the fabrication of fuel for MONJU. As forreprocessing, based on experience with the laboratory-scale test facility PETF, the design of the RecycleEquipment Test Facility (RETF) was finalized. This facility is to be used for engineering tests for FBRfuel reprocessing. The plan for construction of the pilot reprocessing plant will be developed based ontests at RETF, with anticipated operation after the year 2000. PNC has also been a key organizationfor the promotion of international cooperation in the field of FBR R&D, and has concluded variousbilateral and multilateral agreements for cooperation with foreign organizations. Most of the cooperativeactivities have been in the form of information exchange. Nonetheless, they have been quite useful forpromotion of the JOYO and MONJU projects. There have also been a number of cases involvingparticipation in joint research projects with other countries for the efficient utilization of research facili-ties and resources at home and abroad.

2.2.2. Utilities. It has been recognized from the beginning of FBR development in Japan that util-ities should lead the commercialization after establishment of the prototype FBR MONJU. In recognitionof this role of the utilities, FEPC carried out a preliminary design study of a large-scale FBR duringthe latter half of the 1970s. Following this study, FEPC conducted from 1981 to 1983 a conceptualdesign study of a DFBR plant. This work included both the design of the entire plant system of theloop-type FBR (based on MONJU design experience) and the design of major parts of a pool-typeFBR plant. The study concluded that neither of the design concepts was likely to be cost-competitivewith LWRs as their construction costs were estimated to be three to four times higher than those ofcurrent LWRs. Based on this finding, a cost-reduction design study was conducted in 1984. Furtherinnovative design features and technologies were sought to make the DFBR acceptable as a rationalstep for the successful commercialization of FBRs. In 1986, JAPC, which was assigned by FEPC tobe the responsible organization for the design, construction, and operation of the DFBR, started the

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following R&D as part of the succeeding DFBR design study by the utilities group: (i) search fortechnological innovations which may be effective for improvement of the economy of FBRs; (ii) R&D on technologies which are crucial for the selection of basic specifications of DFBRs and are necessaryfor the design, construction, operation, and maintenance of DFBRs; (iii) R&D for the improvement ofsafety, reliability, and economy of the plant required for commercialization. In June 1990, JAPC startedpreliminary conceptual design studies of the DFBR for a top-entry, loop-type reactor according to thedecision of the FEPC, taking the result of previous R&D into consideration.

2.2.3. JAERI. JAERI has mainly performed basic research for FBRs by utilizing their wide rangeof capabilities in nuclear energy research developed over a period of more than 25 years. The initialcontributions were mainly the advancement of neutronics, including the development of physics andshielding calculation methods. This work involved the evaluation of nuclear data using the fast criticalassembly (FCA) and the compilation of the Japanese Evaluated Nuclear Data Library, JENDL. JAERIis now expanding contributions to the area of FBR safety by utilizing the capability of testing fuel tofailure conditions in the Nuclear Safety Research Reactor (NSRR). It has also conducted basic studieson high performance FBRs and on actinide-burner concepts.

2.2.4. CRIEPI. CRIEPI has been accumulating technologies useful for nuclear reactor developmentin various fields, functioning as a central research laboratory for utilities. Researchers at CRIEPI havebeen performing R&D for the FBR since 1984 on improvements of aseismic design methods basedon seismic isolation systems, elevated-temperature structural design methods, and multi-dimensionalthermohydraulic analysis methods. Also studied were innovative LMFBR concepts and technologieswhich may contribute to the early commercialization of FBRs. It is in this context that CRIEPI con-cluded in 1990 a cooperative agreement with the US Argonne National laboratory on research for thepyroprocessing of FBR spent fuel.

2.3. Funding

The funds for FBR R&D are supplied by the government and industry. Table 1 shows a summaryof the FBR R&D budget in 1988–1990. It should be noted that in addition to the figure in this table,substantial funds have been expended annually by manufacturing companies. The total of their contri-bution is not available but is estimated to equal an appreciable fraction of the funds spent by the utilities.The government budget consists of general and special accounts as is indicated in Table 1. The budgetof a special account for nuclear energy R&D comes from a levy on electric power consumption.

Table 1. Research and development budgets for the FBRs in billion yen.

Organization Items 1988 1989 1990

PNC JOYO operation (1) 4.8 4.4 3.9MONJU construction 65.4 70.0 52.9

(2)R&D of base 15.8 12.2 11.1

technology (1)Subtotal (PNC) 86.0 86.6 67.9JAERI R&D of base 0.37 0.36 0.28

technology (1)JAPC R&D for DFBR (3) 6.0 4.9 5.4CRIEPI R&D for base 1.1 1.0 1.3

technology (3)Technology 1.4 1.8 1.9

demonstration (2)Subtotal (CRIEPI) 2.5 2.8 3.2Total by source(1) General accounting 21.0 17.0 15.3(2) Special accounting 66.8 71.8 54.8(3) Private 7.1 5.9 6.7Grand total 94.9 94.7 76.8

623History and perspective of fast breeder reactor development in Japan

3. TECHNICAL DIRECTION OF FBR DEVELOPMENT

3.1. Concept selection and goals of FBR development

JAEC selected the liquid-metal-cooled FBR (LMFBR) with MOX fuel as a candidate concept forthe FBR development program in the late 1960s. The objective of this program is to construct andoperate a safe, reliable and economically competitive plant in the early part of the 21st century, in thesame manner as several other advanced countries. As for the arrangement of the cooling circuit, theloop-type design concept was chosen by PNC for both JOYO and MONJU.

The FEPC decided [2] in June 1990 that JAPC should pursue the preliminary conceptual designstudy for the first DFBR with the aim of examining the technical feasibility of a top-entry loop-typereactor, setting the unit size at 600 MWe. This decision was made after comparing the concepts of top-entry type and tank-type reactors for approximately 3 years, with emphasis on structural integrity,earthquake-proof characteristics, maintainability, reparability, safety, and economy. The key concernfor the use of the loop type for DFBR was the difficulty of finding an economically competitive plantdesign based on this concept. It is believed that the top-entry type loop-plant concept has potential forimprovements in this respect. For the pool- or tank-type design, the main concern has been difficultyin finding a design approach that meets the structural integrity criteria arising from the design basisfor earthquake-proof reactors. It is believed that this concern may be eased if the use of seismic isolationsystems becomes feasible.

The FEPC also decided to continue studies on the exploitation of more innovative concepts andtechnologies and develop a scenario of utilizing these for the advancement of FBR commercialization.This decision is based on the recognition that: (i) it is desirable to commercialize FBRs and to replaceLWRs as soon as possible to ensure that they can utilize nuclear energy without being limited by theavailability of uranium resources for the protection of the global environment; (ii) safety requirementswill become more severe in the next century; and (iii) cost reductions of LWRs will continue, basedon design simplifications and rationalization in system integration. Specific goals for development estab-lished in these studies are the following: (i) Enhanced safety core concepts and highly reliable reactorshutdown devices must be developed. (ii) Passive decay-heat removal systems with natural circulationmust be developed and incorporated with a normal active cooling system. (iii) The upper core structureand fuel-handling system must be simplified and the rotating plug should be eliminated. (iv) Largeelectromagnetic pumps must be developed for use in the primary cooling circuit in combination withan intermediate heat exchanger and/or a steam generator. (v) Seismic isolation systems must bedeveloped to open the way for plant standardization independent of site conditions while helping toachieve simplifications and material volume reductions in the system. (vi) Highly reliable steam gener-ators, such as double-wall-tube steam generators, must be developed to eliminate the intermediate heat-transport circuit.

The PNC is also performing a series of preliminary design studies of commercial-scale, loop-typeplants to find innovative technology elements and concepts which should be developed for the advance-ment of the LMFBR commercialization process [5]. An interim list of such elements and conceptsproposed in these studies is as follows: (a) build large unit sizes in the range of 1500 MWe; (b) achievehigh burnup (200 GWD/T) and high linear heat rating (480 W/cm) fuel; (c) achieve higher than 40%plant thermal efficiency with an outlet coolant temperature of about 550°C using high-temperaturestructural materials such as SUS316LCN; (d) construct smaller-size reactor vessels by employing threeseparate upper core structures, inverse-nozzle-type fuel assemblies and eliminating the core barrel; (e)realize a direct steam generator made of double-wall heat-transfer tube; (f) fabricate the ‘nozzleless’reactor vessel and cell-liner made of fine ceramics with the latter serving as a guard vessel; (g) realizeself-actuating secondary shutdown systems; (h) pursue decay-heat removal by the direct reactor auxili-ary cooling system with forced and/or natural circulation; (i) construct a concrete containment combinedwith the reactor building; (j) realize a seismic-resistant design based on the use of a seismic isolationsystem; (k) utilize dry processes for cleaning and storage of spent fuel assemblies; (l) apply AI androbotics technology to plant operation and maintenance as widely as possible.

Although a large-scale LMFBR plant is the primary objective for FBR commercialization, smallerunit sizes are also considered by JAERI, CRIEPI, PNC and other research organizations. They arguethat small and medium-scale FBRs may become competitive to LWRs earlier than a large unit through

624 S. Kondo

mass production, as they pose fewer constraints on siting conditions and a group of the smaller-scaledesigns may have potential for uses as a power source in remote areas [6].

3.2. Safety design strategy

The safety design approach for DFBRs is based on a defense-in-depth philosophy, as exemplifiedby the design of the prototype reactor MONJU. This approach is, in essence, to satisfy several designobjectives in parallel: (i) to attain highly reliable operation with special emphasis on maintainabilityand reparability; (ii) to prevent damage to the fuel and plant systems in anticipated and unlikely events;(iii) to prevent the occurrence of a core disruptive accident (CDA) even in the case of extremelyunlikely events; (iv) to build-in design features for increasing safety margins accommodating the conse-quences of CDA in the reactor vessel and mitigating the impact of possible out-of-reactor-vessel conse-quences of CDA. A two-tier approach has emerged as the strategy to satisfy these objectives, basedon the lessons learned from incidents and accidents that occurred in the past and various PRA/PSAstudies [7]. This approach requires the design of safety functions based on conservative deterministicdesign criteria of which an implicit goal is to ensure that the frequency of CDA due to any event familyis less than once in 10 million reactor years or 10−7 per reactor year. It also requires the designer toexploit and/or enhance the functions of passive safety features so as to improve assurance that theprobability of CDA due to any event family is less than 10−7 per year, and to mitigate the consequencesof CDA to ‘as low as reasonably achievable’ levels so that there is no significant ‘cliff edge’ in therisk profile of the plant.

Examples of the results obtained by applying this two-tier approach to the reactivity shutdown func-tion for DFBRs are as follows. The basic configuration of the system planned is to have two independentreactor-shutdown systems, each of which is made up of a trip system and an associated absorber rodgroup. Diverse, independent trip systems and rod and driving mechanism systems are planned. Allow-ance of a margin for a stuck rod is provided for each absorber rod group. A preliminary reliabilityanalysis has indicated that the frequency of unprotected events which may cause CDA is less than 10−7

per reactor year with these configurations. However, two passive features are under development asbackup or for the further reduction of possible contributions of common mode failures to the loss-of-reactivity shutdown-function event. One of these is the articulated absorber rod for ensuring rod insertioneven in the case of excessive deformations of aligning guide tubes which might result from an earth-quake of intensity beyond the design basis earthquake. The other feature is the use of a Curie-pointunlatching mechanism which triggers reactivity shutdown by sensing temperature anomalies caused bypower-to-cooling mismatch events in the core.

For the decay-heat removal function, both maintenance of the coolant level in the reactor vessel andassurance of coolant circulation for heat transport from the core to the heat sink are essential. Thereactor and guard vessels are considered to be two strong passive lines of defense for the preventionof excessive loss of coolant. The heat-transport capability is to be maintained by the redundant activedirect reactor auxiliary cooling system (DRACS) and the primary reactor auxiliary cooling system(PRACS), in addition to the main heat-transport path through the steam generators, to cope with poten-tial failures in the latter system. A preliminary evaluation has indicated that the frequency of the loss-of-decay–heat removal function is less than 10−7 per reactor year with this configuration. Nonetheless,it is planned to provide the capability to remove the decay heat by natural circulation with thisPRACS/DRACS as the second tier. The introduction of this capability of natural convection-decay–heat removal makes it easy to cope with the combination of an S2 (the ultimate design basis) earthquakeand station blackout event. This arrangement increases the grace period during which the plant operatorshould find ways to manage such extremely unlikely events. Key issues remaining concern the meansto demonstrate the availability of this capability under extremely unlikely conditions. Extensive R&Dactivities are being focused on this topic.

As for the third safety function, that is, the containment of radioactive material, most LMFBRs haveseveral intrinsic and engineered containment systems. The determinant for the configuration of engine-ered containment systems is the fraction of radioactive iodine released in the cover-gas region of thereactor vessel in the CDA. If a large fraction of radioactive iodine is released into the cover-gas region,both leak-tight containment and confinement are necessary as in the case of LWRs to satisfy the licens-ing requirement as 10%/day is a reasonable assumption for the leak rate of the roof slab. If the fractionis below 10−4 owing to the chemical affinities of sodium and iodine, however, a confinement with a

625History and perspective of fast breeder reactor development in Japan

leak rate of about 100%/day can be acceptable. At present, this fraction is under intensive investigationand therefore no decision has yet been made on the design basis event for the containment system.The approach being taken for satisfying the second-tier requirement is to study the consequences ofCDA and exploit and/or enhance relevant passive safety features which rely on structures of or compo-nents in the reactor vessel. Some of the features under consideration are as follows: (i) Capability ofin-vessel structure to absorb the kinetic energy of sodium released by severe core damage, and thusprevent the degradation of primary system boundary. (ii) Effects of core support structure on the forma-tion of stable bedding of fuel debris in the reactor vessel to eliminate the possibility of recriticality.(iii) Geometry of core support structure to ensure effective natural convection for debris bed cooling.(iv) Capability of sodium to retain the fission products. (v) Leak tightness of the cover-gas boundaryenhanced by the effective use of an incident seal structure for the roof slab.

Needless to say, to make a plant adequately safe requires a continuous quest for excellence as theINSAG committee of IAEA put in their report [8]. We have learned through hard experiences in thepast that vigilance concerning all details of design and the assurance of excellent plant managementare essential for this achievement. It should therefore be noted that what has been outlined here is onlya part of the activities applied for the safe design and operation of DFBRs.

4. POLICY CONSIDERATIONS

4.1. FBR deployment policy

The start of FBR deployment by electric utilities will depend on many factors, including the rate ofelectricity demand growth, the cost of electricity generation with FBRs, the trend of uranium pricesduring the life of the plant under consideration for construction, the availability of plutonium and theFBR fuel-cycle services, the performance of LWRs available, etc. Although the current goal of theJAEC’s FBR R&D program is to establish the capability for commercializing the FBRs in the 2020sto 2030s, it has become obvious that due to the current downward-revised rate of the increase of nuclearenergy and the expanded uranium resource base, the time-frame for the establishment of the capabilitycan be shifted more than 10 years into the future. Furthermore, the major part of the world nuclearenergy growth for times beyond 2050, which will cause the need for FBRs, will obviously occur incurrently developing nations (particularly in Asia). What should the government and industry do then?One may say that it is not cost-effective now to continue a large-scale investment in FBR R&D, asthe availability of FBR technology demonstrated by various foreign plants and MONJU, which willrestart operation after remedy in a few years, will be sufficient as a prerequisite for restart of thecommercialization process when the need for the FBRs is foreseen within a time period necessary forthe construction and operation of near-commercial plants. Or one may suggest a more cautious approachof keeping the investment in FBR development at the minimum level necessary for maintaining suchcapability of restart when needed, considering it as an insurance premium against unexpected changesin the energy scene of the future [9].

Key characteristics of the nuclear energy business, however, are long lead-times of about 20 yearsnecessary for the development and deployment of new-type plants and long life-times of about 50 yearsfor nuclear power plants once they are constructed. From the global perspective, it is therefore desirableto pursue establishment of the capability for the transition from LWRs to FBRs by the mid-21st century.The other important point to keep in mind is that the market for new electricity generating technologyis decided by electric utilities as they are the only customer for the technology. Taking into considerationthese characteristics and the fact that Japan is not endowed with any natural energy resources, it isprudent and ethical for JAEC to continue to encourage the utilities to pursue the construction andoperation of DFBRs which can be excellent precursors for the commercial FBRs deployed in Asia fortimes beyond 2050, maintaining necessary expertise through investment into the development of innov-ative FBR technologies.

It is true that utilities are becoming rather cautious to commit to the construction of DFBRs, first,because they are not sure at present that the second DFBR which will succeed the first DFBR willbecome sufficiently competitive to LWRs as a near-commercial FBR, and second, because their primaryconcern at present is how to obtain new sites for LWRs as suggested in the recent report of MITI’sEnergy Committee on the revised energy demand and supply outlook [10], according to which nuclearpower plants are expected to be constructed and put in service in Japan at a rate of 2 GWe per year

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to the year 2010, reflecting both the recent surge of energy demand and concerns for global warming.It should also be mentioned that suspension of the operation of MONJU due to the sodium leakageevent in 1995 will cause a delay in the development of the high burnup fuel necessary for DFBRs.The most probable course in sight is therefore to start the basic design of the first DFBR sometimeafter the restart of MONJU, aiming at the start of its construction around 2010 under the condition thatthe design will give sufficient assurance that the construction and operation of the plant will be apositive benchmark for establishing the capability to produce a commercially competitive LMFBR.

4.2. Non-proliferation

Reprocessing of LWR spent fuel and the use of recovered plutonium are vital elements of the nuclearenergy program based on the FBRs which succeed the LWR program. Recognizing this, the constructionof necessary facilities is moving ahead in Japan in accordance with bilateral nuclear cooperation agree-ments concluded between the governments of Japan and foreign countries, following the conclusion ofthe International Nuclear Fuel Cycle Evaluation (INFCE) study. As it is a firm belief of JAEC thatbefore any country can enjoy the benefits of this technology, it is vitally important to establish effectivesafeguards and physical protection systems in all the fields of reprocessing, fabrication, irradiation andtransportation of plutonium fuel, the PNC and other organizations involved have been promoting thedevelopment of such systems in cooperation with IAEA for the various elements of a nuclear fuel cyclesystem involving the use of plutonium. It is clear that the same system can be applied to commercialFBRs and their fuel-cycle system in order to provide adequate protection against the diversion of wea-pons-grade nuclear material by malevolent parties. In Japan, some of these safeguard technologies havealready been utilized for MONJU. It can be argued that additional rules to regulate the locations andprocessing method for sensitive fuel-cycle activities should be established as the condition for allowingthe large-scale deployment of breeders. It seems too early to judge whether the restriction on geographi-cal locations of the FBR fuel cycle facility vis-a`-vis power plants will be a meaningful addition fromthe viewpoint of safeguardability and physical protection. Furthermore, as the dominant issue of thesafeguard system for FBR systems is assurance for the secure management of plutonium, the develop-ment of international institutional means for ensuring the proper storage and utilization of plutoniummay provide the most cost-effective route to adequate safeguards.

4.3. International cooperation

The goal of JAEC’s FBR R&D program is to create an indigenous technology adequate to attainand sustain commercial applications of the breeder. To have such a goal should not be automaticallyinterpreted as reluctance for technical cooperation with other leading countries in FBR technology.Needless to say, through various kinds of technical exchange programs with these countries, Japan hasreceived considerable help for rapid progress on the R&D program and has also contributed, to someextent, to progress in FBR technology for the world. Considering this fact and the limited current statusof the world FBR R&D program, Japan and Japanese utilities in particular should approve making theirR&D and DFBR construction programs open to foreign partners, even if this were to imply a possiblesacrifice for part of its own program schedule in order to lead the world’s FBR technologies towards pro-gress.

Japanese utilities have in the past declined several times to participate in joint investment on thedesign and/or construction of a FBR demonstration plant. The principal reasons for rejections are theexistence of too large a difference in the seismic design conditions for Japan and other countries andthe difficulty of recovery of the investment due to the absence of a suitable electricity transmissionline. These are not insurmountable problems. Considering the progress made worldwide and in Japanon the internationalization of major businesses, Japanese utilities should find arrangements for pursuingpossible joint developments of FBRs to be an acceptable option.

4.4. Diverse uses of FBRs

Considering the role of the FBR as one of the major alternatives for nuclear energy supply techno-logies for the foreseeable future, a variety of applications for FBRs should be developed in additionto large-scale electricity generation. Compared with the LWR, the LMFBR systems have the followinguseful characteristics: (a) availability of intense fluxes of fast neutrons; (b) potential for long core life;(c) suitability for small plants; (d) potential for high coolant temperatures. There have been several

627History and perspective of fast breeder reactor development in Japan

preliminary studies on the application of the FBR for actinide burning and hydrogen production. Smallunits are possible for remote isolated sites, perhaps ultimately including lunar bases. Of these, thepossibilities for actinide-burning FBRs and hydrogen production have considerable strategic importancefor the long-term goal of the FBR R&D program. Studies are under way on the nuclear performanceof LMFBR cores as actinide burners [11]. The idea is to dispose of transuranic (TRU) elements suchas neptunium and americium, whose half-lives are from 400 to 2 million years, in the fast-neutronspectrum core. One possible way is to add TRU elements as minor ingredients of the fuel withoutmaking significant changes in the reactor and fuel-cycle system design and operation. The potentialmerit of the idea is to provide an intrinsic proliferation resistance to the fuel cycle and reduce theradioactivity of the high-level radioactive wastes from the cycle.

Hydrogen production by nuclear energy is expected to widen the niche for nuclear energy appli-cations. Electrolytic and thermochemical processes are known for hydrogen production. The formeruses electricity from FBR power plants. The latter uses heat from the FBR if the coolant temperatureis high enough. PNC has made a preliminary study of the use of 700°C sodium from the FBR forhydrogen production based on the UT-3 process, which is known to be one of the most promising low-temperature thermochemical water-splitting methods [5].

5. CONCLUSION

Japanese FBR R&D activities are reaching a turning point with completion of the construction ofMONJU. Utilities are expected to take major responsibility in pursuing the further advancement towardscommercialization. It is clear that if the people on earth want to continue to enjoy adequate suppliesof energy with rationally limited environmental impacts, they must continue to explore the capabilityto expand the use of nuclear energy significantly including FBRs. It is also clear that the FBR shouldprovide a significant fraction of the nuclear energy supply mix by the end of the 21st century if nuclearenergy is used as a major alternative for fossil fuels. Forward-looking investment for FBR R&D byadvanced industrialized countries will ensure the future world society availability of an important optionfor energy supplies from FBRs when these are needed. The issue before Japan is how to continue interimdevelopment and deployment of the FBR. Stepwise demonstration of the technology by constructingintermediate plants and developing the required technical products are essential. Sound coordination ofresearch and construction is needed among the world’s FBR developers since the needed resources aresignificant. Japan should continue to take the responsibility of leading the development work as appro-priate for its needs as one of the major energy consumers in the world with essentially no endowmentof natural energy resources.

REFERENCES

1. Japan Atomic Energy Commission’s Long-Term Plan for the Development and Utilization of Nuclear Energy,Japan Atomic Energy Commission, June, 1987.

2. Hori, M. and Takeda, A., inProceedings of the International Conference on Fast Reactors and Related FuelCycles, October 1991, Kyoto, Japan, pp. 1–5.

3. Usami,S. and Iwata, K., inProceedings of the 10th Pacific Basin Nuclear Conference, 20–25 October 1966,Kobe, Japan, p. 843.

4. Kurihara, H. and Kashihara, H., inProceedings of the International Conference on Fast Reactors and RelatedFuel Cycles, October 1991, Kyoto, Japan, pp. 1–10.

5. Hori, M., Fukuda, T. and Takahashi, T., inProceedings of the International Fast Reactor Safety Meeting, 12–16 August 1990, Snowbird, Utah, pp. 477.

6. Kawakami H., Nishiguchii, Y. and Sakano, K., inProceedings of the International Conference on Fast Reac-tors and Related Fuel Cycles, October 1991, Kyoto, Japan, pp. 14–4.

7. Kondo, S., inProceedings of International Fast Reactor Safety Meeting, 12–16 August 1990, Snowbird, Utah,p. 115.

8. Basic Safety Principles for Nuclear Power Plants, IAEA Safety Series No.75-INSAG-3, 1988.9. Suzuki, T. and Suzuki, A.,Science and Public Policy, 13-1, February 1986.

10. Long-Term Energy Demand and Supply Outlook, Ministry of International Trade and Industry, October, 1990.11. Mukaiyama, T., Yoshida, H. and Gunji, Y., inProceedings of the International Conference on Fast Reactors

and Related Fuel Cycles, October 1991, Kyoto, Japan, pp. 19–6.