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Russian plutonium policy
ELSEVIER
Nuclear Engineering and Design 173 (1997) 293-299
Nuclear Engineering and Design
Russian plutonium policy N. Ponomarev-Stepnoi
*, D . T s o u r i k o v
Russian Research Center 'Kurchatov Institute', 123182 Moscow, Russia
Abstract
This paper is intended to provide more detail on the main features of Russian strategy of utilization of both the civilian and weapons-grade plutonium. At present, the Russian Federation has a large stock of plutonium and at the same time some scientific, technological and industrial experience in the utilization of plutonium, in particular in fast reactors. The key elements of Russian plutonium policy are the interim secure storage and plutonium disposition in nuclear reactors. The disposition options being discussed are the following: BN-type reactors, VVERs, and HTGR. It is shown that the utilization of weapons-grade plutonium, for a number of reasons, should begin using the reactors currently in operation. The importance of broad international cooperation for a safe and effective management of weapons plutonium designated as no longer required for defense purposes has been stressed. © 1997 Elsevier Science S.A.
1. Introduction
In Russia nuclear power develops on the basis of the existing nuclear industrial complex. This complex was created to provide the country with nuclear weapons. The complex integrates the whole chain of technologically related enterprises, including mining and processing o f uranium ores, enrichment facilities, plants for manufacturing of fuel elements, commercial nuclear reactors, radiochemical plants for reprocessing of spent fuel, plutonium handling installations and other components of the nuclear fuel cycle. At present Russia has nine operating NPPs totaling 21 242 M W (el) with 13 V V E R units, 11 R B M K units and one BN unit. * Corresponding author. Tel.: + 32 2 2993184; fax: + 32 2 2950146.
F o r the present-day scale of nuclear power there is no problem in its fuel supply. Russian nuclear power with its open or semi-closed fuel cycle will be sufficiently provided with fuel from the available reserves of raw materials within the next few decades. An inevitable absolute growth o f the nuclear capacities and an increase o f their contribution to the total fuel balance as well as the extension of regions and the increasing number o f countries using nuclear energy are expected in the future. Then, although it is hard to predict exactly when there comes that time, nuclear power will encounter the problem of nuclear resources, unless it is on the point of recycling nuclear fuel. In Russia the nuclear fuel cycle strategy was established at the stages of formation and intense development of the domestic nuclear power. The two-components nuclear power based on thermal reactors and breeders reactors was proposed. This
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structure assumes a closed fuel cycle: chemical reprocessing of spent fuel with the reuse of both recovered uranium and recovered plutonium. Following this concept, Russia has gained some experience in reprocessing of spent fuel with the recovery of plutonium and its recycling in reactors. The greatest efforts were made on the utilization of plutonium in fast breeders reactors. Works on the use of MOX fuel in VVERs were also conducted. But it should be stressed that the slowdown in the rates of nuclear power development and a surplus of uranium fuel lessened the efforts on development of mixed fuel for VVERs.
2. Russian experience in plutonium utilization As marked above the efforts connected with the use of plutonium in nuclear power have been quite extensive in Russia from the very beginning. Investigation on the use of plutonium as a fuel commenced at the V N I I N M in the 1950s with the development of fuel elements for various fast reactor tests. These early investigations led to the construction in the mid-1960s of a pilot line at 'Mayak'. This pilot line was used to produce cores for the reactors BR-5, IBR-2 and to produce experimental fuel assemblies for the reactor BOR60. The initial investigations of MOX-pelleted fuels were based on mechanical mixing of the individual dioxides of uranium and plutonium. In 1980, a ' P A K E T ' facility was developed at 'Mayak' with the sections for both pelletizing and fabricating fuel elements. The capacity of the facility is 350 kg/year total of uranium and plutonium oxides. In 1980-1981, the first 10 full-length fuel assemblies were manufactured and used to test in BN-350 reactor. At the beginning of 1987 a pilot-industrial facility 'Granat' was designed and constructed at 'Mayak'. MOX fuel production began in April 1988. The facility produced one test subassembly for the BN-350 and has established the baseline for tests in BN-600. Currently five technical processes have been developed for producing mixed oxide pelleted fuels:
• • • • •
mechanical mixing of oxides; sol-gel process ('Zhemchyg'); ammoniac granulation ('Granat'); carbonate co-precipitation; and plasma-chemical conversion. The in-reactor testing of fuel assemblies containing fuel elements with MOX-pelleted fuels commenced at the beginning of the 1970s, first in the BOR-60 reactor, and then in BN-350 and BN-600. Up to now 37 subassemblies with MOX pelleted fuel have been fabricated and irradiated at the BOR-60, BN-350, and BN-600 reactors. A pilot facility for producing MOX fuel elements by vibropacking technology is in operation at the State Scientific Center 'Research Institute of Atomic Reactors' (Dimitrovgrad, RIAR). The production equipment for fabrication of MOX vibropacked fuel from civil and weapons-grade plutonium has proved to be highly reliable and has a capacity of making about 50-60 subassemblies per year for fast reactors. Besides there are two technological lines situated in the glove-boxes for BOR-60 subassemblies production at the RIAR. The vibropacked MOX fuel (354 subassemblies) was tested in BOR-60, BN-350, BN600. Since 1981 the BOR-60 reactor has been operated with MOX fuel made by the vibropacking process. The first experience in the weapons-grade plutonium irradiation was gained in Russia in the experimental reactor BR-10 at the State Scientific Center 'Institute of Physics and Power Engineering' (Obninsk, IPPE), where two cores with the PuO2 fuel were tested. The first core with PuO2 was in operation from January 1959 to November 1964; the second core, from 1971 to 1979. At the industrial pilot-plant BN-350, MOX-fuel assemblies (350 kg of weapons-grade plutonium) were tested, reprocessed and examined. The positive experience gained with the fabrication, operation and post-irradiation examination of MOX pelleted fuel formed the basis for the construction of the first production line of Complex-300 at 'Mayak'. The Complex-300 was design to produce subassemblies for BN-type reactors. The construction was started in 1983. However, the economic situation halted all construction, research and design development work
N. Ponomarev-Stepnoi, D. Tsourikov/ Nuclear Engineering and Design 173 (1997) 293-299
for Complex-300 in 1989. At present, about 50% of the construction has been completed. In Russia the fuel cycle is oriented to the chemical reprocessing of spent nuclear fuel. The RT-1 plant built in 1977 at 'Mayak' can reprocess the spent fuel of VVER-440, BN-350, BN600, research and naval reactors. Its capacity is sufficient to serve the domestic and foreign NPPs with VVER-440 type reactors. The end products of reprocessing are: • uranium containing 2 to 2.4% of U-235 which is re-enriched with highly-enriched uranium obtained in reprocessing spent fuel from naval reactors and used as RBMK fuel; • plutonium (plutonium dioxide) which is enclosed in special packages and transported to a storage facility. At present, the RT-1 plant works at the partial capacity producing 0.6 tons of plutonium per year. At a full capacity, the RT-1 plant can produce 2.5 tons of reactor-grade plutonium per year. The RT-2 plant for reprocessing of spent VVER-1000 fuel was planned and is partially constructed. According to the project the plant must produce uranium dioxide pellets for WE R- 1 0 0 0 fuel elements and plutonium oxide powder for mixed uranium-plutonium fuel for the VVER-1000 reactors. The RT-2 plant construction started in 1977. Since 1991, construction has been suspended due to the lack of financing of the Russian Nuclear Energy Program. Approximately 10% of the planned capital cost had been expended at that time. Closing the VVER-440 and VVER-1000 fuel cycles requires to complete the construction of the RT-2 plant and a complex for production of mixed uranium-plutonium fuel. At present, Russia has accumulated approximately 30 tons of reactor grade plutonium produced from spent uranium-based fuel of VVER-440, BN-600 and BN-350 at the RT-1 plant, this quantity will achieve 47 tons by the year 2005. As a result of strategic and tactical nuclear weapons reduction, significant amounts of weapons grade plutonium, that could be identified as no longer required for military pur-
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poses, will also accumulate. This amount for Russia is about 50 tons. As discussed above, the Russian Federation has a large stock of plutonium and at the same time some scientific, technological and industrial experience in the utilization of plutonium.
3. Plutonium utilization in nuclear reactors 3.1. Reactor options
At the Moscow Nuclear Safety and Security Summit in April 1996, the G7 countries and Russia expressed their determination to ensure that 'fissile material designated as no longer required for defense purposes will never again be used for nuclear-explosive purposes', and 'that effective management of this material will aim to reduce stocks of separated plutonium and highly-enriched uranium...as soon as practicable'. A considerable analysis has been performed by international experts to identify the available technical options that will provide 'an optimal answer to this problem, both in terms of nonproliferation and of the environment, and also from an economic and technical viewpoint'. A wide range of various alternatives was identified for consideration: • nuclear reactors, • storage, • geological formations, • accelerators, • immobilization, and • stabilization of solutions and other forms. The experts at the Paris meeting on safe and effective management of weapons fissile materials designated as no longer required for defense purposes in October 1996 concluded that there are two options which offer prospects of early progress towards the non-proliferation and other objectives set by the Moscow summit: • utilization of weapons-grade plutonium as MOX fuel in reactors, and • plutonium immobilization. Both these options may be suitable for some countries in their national programs on plutonium disposition.
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In Russia plutonium is viewed as an extremely valuable national resource and a potential source of energy for the future. Thus, Russia favors the burning of plutonium in nuclear reactors. Plutonium immobilization is being considered for disposition of plutonium which is unsuitable for use in MOX fuel. The traditional Russian plutonium policy based on the following points: • safe and reliable storage of plutonium until it may be used in reactors; • utilization of plutonium in reactors; • future orientation on nuclear power centers to find the reliable solution of the non-proliferation problems. This is explained by the desire to use the high energy value of plutonium, the capabilities of the existing nuclear industrial complex, the adopted national concept for long-term nuclear energy development, and the scientific and technological background. The utilization of the weapons-grade plutonium is being considered as a part of its national plutonium strategy. In Russia various variants of burning plutonium in power reactors are been considered: BNs, VVERs, and H T G R . Moreover, Russian experts in collaboration with A E C L (Canada) experts are examining the possibility of plutonium burning in C A N D U reactors. These approaches correspond formally to the term 'spent fuel standard' accepted in the USA. However, in some cases the Russian option of plutonium burning in nuclear reactors involves the possibility of spent fuel reprocessing and recycling of nuclear fuel, including plutonium. First of all, this is true for the BNtype reactors, but the possibility for recycling of spent VVER fuel is not ruled out. At present, for a number of reasons, including approved political decisions on converting the plutonium into spent fuel or other forms equally unusable for nuclear weapons as soon as practicable, current economic situation in Russia, and existing world experience in MOX fuel utilization, the weapons-grade disposition policy has been change. The utilization of MOX fuel should begin using the reactors currently in operation, that is to say BN-600 and VVER-1000s.
3.2. Fast reactors
Russia has large scale experience in developing fast reactor technology. The extensive valuable experience has been gained in mixed oxide fuel fabrication and irradiation tests, development, construction, and operation of fast reactors. The most significant success achieved in the field of Russian fast reactor technology is the construction and operation of the BN-600. The BN-600 reactor was put in operation in 1980 as the third power unit at Beloyarskaya NPP. The successful operating experience of BN-600 is attributed to the appropriate design and technical solutions, high quality in the manufacturing of components, and proper management of reactor operation. This positive experience has allowed Russian organizations to start development of the BN-800 reactor design. The BN-800 reactor has been designed for electricity production and plutonium utilization and meets regulatory safety requirements now in effect in Russian Federation. The core design has been developed for using civil plutonium, but calculations studies performed shown that there are no serious problems to use in BN-800 weapons-grade plutonium. According to the national fast reactor program it was planned to construct three or four MOXfueled BN-800 as well as complete the Complex300. Construction of the BN-800 reactor was started simultaneously at the South Urals and Beloyarskaya NPPs at the end of the 1980s, but both were halted in the early 1990s due to the changing of the economic situation in Russia. The vision of Russia was to utilize one BN-800 located at Mayak place for disposition of weapons-grade plutonium. This design is to use 2.3 tons of weapons-grade plutonium for the initial loading and 1.6 tons for annual feed. Necessary supporting facilities would also be built at Mayak. These facilities include: • a metal-to-oxide conversion facility, • a mixed uranium-plutonium oxide (MOX) fuel fabrication facility, and • an intermediate spent fuel storage facility. These facilities would have a capacity of 3.3 metric tons per year. Given adequate financial
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support the new BN-800 reactor at Mayak would be ready for start-up around the year 2005. Contingent upon adequate financial support, the metal-to-oxide conversion plant and the MOX fuel fabrication plant were both scheduled to start up by the year 2002. At present, Russia considers that an early start on the disposition of excess weapons plutonium in fast reactors can be met by using a hybrid core as a demonstration in the existing BN-600 reactor. The use of MOX fuel in the BN-600 reactor gives rise to the main two problems: • The first problem is the need to improve the fresh fuel handling systems. Such a system can be manufactured and installed during 1997 1998. • The second problems relates to Russian regulatory requirements which say that sodium void reactivity effect (SVRE) must be nonpositive or at least negligibly small. For the existing uranium fuel core in BN-600, the SVRE is negative of about - 0 . 5 % A k / k . The simplest way to introduce plutonium into BN-600 core is to create so called hybrid core with simultaneous using enriched uranium and MOX fuel in the same core. Design aspects of the BN-600 hybrid core for plutonium consumption have been developed. The core design could be completed this or next year. This project could be started by the year 2001 with the completion of a pilot plant for MOX fuel fabrication including metal plutonium to oxide conversion. Different conceptual designs for pilot plant are currently under consideration with European partners. This plant would be able to feed up BN-600 and four VVER- 1000. The scheduled end-of-life of the BN-600 reactor is the year 2010. Thus BN-600 using hybrid core would be able to effect disposition of 5 metric tons of weapons-grade plutonium. 3.3. V V E R type reactors
The utilization of plutonium in VVER-1000 reactors is one of the most realistic options, because reactors of this type are in operation in
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Russia and abroad. There is long standing experience in MOX fuel fabrication and MOX utilization for LWR type reactors in Western Europe. Proven MOX fuel fabrication technology for LWR type reactors, as well as commissioning and operating know-how, and equipment could be available at present time in the framework of international cooperation. The MOX fuel utilization in LWR type reactors does not only meet the spent fuel standard but also degrades the isotopic composition of plutonium to a non-weapons grade level. Seven existing plus three partially complete VVER-1000 and a new generation of VVER type reactors with improved safety are being considered now in Russia for weapons-grade plutonium utilization. The simplest way of involving plutonium in the VVER-1000 fuel cycle being considered now by Russian experts is the direct replacement of a part of uranium fuel by MOX fuel without essential changes in the core design and the unit operating conditions. The physical features of the core with uranium-plutonium fuel pose restrictions on the number of MOX fuel assemblies in the VVER1000 of existing design. Their fraction is about one-third of the core. The extensive program of work on utilization of weapons plutonium in VVERs to substantiate the decision about the loading of one-third of the VVER-1000 core by plutonium fuel assemblies is underway now. This program includes a complex of calculation studies and experiments, in particular: • conducting of the critical experiments with uranium-plutonium fuel; • upgrading and verification of the codes for the calculation of the neutron-physical characteristics of the VVER-1000 cores with plutonium fuel (comparison with the results of the precision calculations made by Russian and foreign codes, analysis of the results of the Russian and foreign critical experiments with plutonium fuel); • complex calculations for the substantiation of the safety with particular emphasis on reactivity accidents; • trial operation of plutonium fuel assemblies in operating VVER-1000s;
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• review of the Western experience in the use of MOX fuel in PWRs. To obtain the experimental data for the verification of the codes the critical experiments with MOX fuel should be conducted. This study is underway now at the IPPE and at the Russian Research Center 'Kurchatov Institute' (Moscow, RRC KI). Alongside with the substantiation of the neutron parameters of cores with uranium-plutonium fuel for licensing purposes it is necessary to substantiate the serviceability of MOX fuel elements. The loop tests of plutonium fuel elements for VVER-1000 are in progress now at the RIAR. A program for development and trial operation of three pilot fuel elements containing weapons plutonium in the VVER-1000 reactor at Balakovskaya NPP has been drawn up. The possibility of the trial operation of these fuel elements is being justified by the neutron-physical calculations being performed at the RRC KI. The program to be carried for the three MOX assemblies includes: • In 1997-1998, manufacturing of three experimental MOX fuel assemblies for irradiation in a VVER-1000 reactor; • Mid-1998, loading of the first W-Pu MOX assembly in the core of a VVER-1000 reactor at Balakovskaya NPP; • In 1999, loading of the two remaining W-Pu MOX fuel assemblies in the core of the same VVER-1000 reactor. It should be mentioned that for the VVER options, MOX fuel fabrication capabilities will be needed as uranium-plutonium fuel for VVER reactors has not produced in Russia. Research and development, design efforts and development of the technology for MOX fuel production are in progress with the collaboration of Western partners. There are grounds to believe that the trial operation of three MOX fuel assemblies in a VVER-1000 reactor might be started in the year 2000 and that the pilot loading of a third of the core in an operating VVER-1000 reactor by MOX fuel assemblies might be made in the year 2004.
3.4. Gas-cooled high-temperature reactors
In November 1993 the M I N A T O M R F addressed to the US Government a proposal on the joint US-Russian Program on development of a G T - M H R reactor plant which could be efficiently used for burning weapons-grade plutonium. The first G T - M H R reactors were suggested to be constructed in Seversk. At present, joint US-Russian development of the Conceptual G T - M H R Project is under way with the financial backing given by the General Atomic (the USA) and M I N A T O M RF. Recently, Framatome (France) has joined the Program. The Conceptual Project is planned to be completed in October 1997. The G T - M H R concept is based on the use of the core with the graphite moderator and helium coolant as well as of the fuel in the form of microspheres with multilayer pyrocarbon and silicon carbide coatings. The G T - M H R consists of a reactor enclosed into a steel high pressure vessel incorporated with the power conversion system using gas turbine cycle. The core consists of hexagonal graphite prism fuel elements based on coated particles. The G T - M H R is characterized by enhanced safety and high efficiency (up to 50%), which make it more economically advantageous comparing with other reactor types. In the reactors of this type weapons-grade plutonium is used in the form of undiluted plutonium dioxide. The employment of microspheres with multilayer coatings of pyrocarbon and silicon carbide allows a high burnup of plutonium: up to 90% of the initial Pu-239 charge, to be reached in a once-through reactor cycle. Plutonium contained in the spent fuel is of no interest for weapons production. The ceramic structure of the spent fuel and the multilayer coating properties make possible its long-term disposal in geological formations without reprocessing. The leaching tests have demonstrated a higher ability of coated fuels to retain wastes as compared with the method using borosilicate glass. It should be stressed also that the use of multilayer coatings would increase the resistance of
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starting plutonium to proliferation and diversions. In the GT-MHR the quantity of useful power generated per a gram of burnt plutonium for once-through fuel irradiation is larger than in any other reactor system. Thus, the concept of weapons-grade plutonium disposition using the GT-MHR includes the following stages: • transforming weapons-grade plutonium into another form, namely, coated particles, which practically rules out the possibility of its use for military purposes; • burning weapons-grade plutonium in the GTMHR reactors with efficient generation of useful power; • long-term disposal of the spent fuel in geological formations. The foundation of the GT-MHR Project is both the solutions proven in the development and operation of foreign high temperature reactors as well as longer than the 30-year Russian experience in designing the HTGR reactors. Russia has evaluated alternative variants for reprocessing 50 tons of plutonium using the GTMHR. One of these variants suggests the construction of three plants, each containing four reactor modules: in Seversk, Krasnoyarsk, and at the 'Mayak' Combine. The first reactor module may be put into operation in 8.5 years after the decision is made, the last one in 6 years after this date. These plants would reprocessed 50 tons of plutonium during 25-30 years after the decision is made. The location of a fuel production facility and a GT-MHR plants in Seversk as well as in Krasnoyarsk and at 'Mayak' having a well organized infrastructure for weapons-grade plutonium handling and security reduces the proliferation risk. As discussed above, the GT-MHR could be efficiently used simultaneously for the production power and for surplus weapons-grade plutonium disposition.
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4. Conclusions
The Russian strategy of utilization of plutonium, being considered as valuable national resource and a potential source of energy, is the inalienable part of long-term National nuclear energy program. The key elements of this strategy are the following: • interim secure storage, and • disposition of plutonium in nuclear reactors. Follow the approved political decisions on safe and effective management of weapons fissile materials designated as no longer required for defense purposes and taking into account the urgency of the problem of reducing the security risks posed by excess weapons plutonium, Russia will begin using existing nuclear reactors for disposition of weapons-grade plutonium, in particular BN-600 and VVERs- 1000. All the same, long-term used of fast breeder reactors as well as high-temperature gas-cooled reactors will continue to be studied by Russia. Russian experience in the utilization of plutonium is limited by fast reactors and there is no industrial production of MOX fuel that would meet current requirements for safety and output capacity. At present, research, development, and design are under way with the collaboration of Western partners. It should be stressed, that MOX fuel manufacturing and operation will be provided by security and accounting measures meeting stringent international standards and ensuring effective non-proliferation control and transparency. The importance of broad international cooperation for safe and effective management of weapons fissile materials designated as no longer required for defense purposes has been recognized by all states having experience in using plutonium. It is necessary now to focus joint efforts on reaching practical and operational results and on creating mechanisms for international cooperation in the financing and management of corresponding projects.
Nuclear Engineering and Design 173 (1997) 293-299
Nuclear Engineering and Design
Russian plutonium policy N. Ponomarev-Stepnoi
*, D . T s o u r i k o v
Russian Research Center 'Kurchatov Institute', 123182 Moscow, Russia
Abstract
This paper is intended to provide more detail on the main features of Russian strategy of utilization of both the civilian and weapons-grade plutonium. At present, the Russian Federation has a large stock of plutonium and at the same time some scientific, technological and industrial experience in the utilization of plutonium, in particular in fast reactors. The key elements of Russian plutonium policy are the interim secure storage and plutonium disposition in nuclear reactors. The disposition options being discussed are the following: BN-type reactors, VVERs, and HTGR. It is shown that the utilization of weapons-grade plutonium, for a number of reasons, should begin using the reactors currently in operation. The importance of broad international cooperation for a safe and effective management of weapons plutonium designated as no longer required for defense purposes has been stressed. © 1997 Elsevier Science S.A.
1. Introduction
In Russia nuclear power develops on the basis of the existing nuclear industrial complex. This complex was created to provide the country with nuclear weapons. The complex integrates the whole chain of technologically related enterprises, including mining and processing o f uranium ores, enrichment facilities, plants for manufacturing of fuel elements, commercial nuclear reactors, radiochemical plants for reprocessing of spent fuel, plutonium handling installations and other components of the nuclear fuel cycle. At present Russia has nine operating NPPs totaling 21 242 M W (el) with 13 V V E R units, 11 R B M K units and one BN unit. * Corresponding author. Tel.: + 32 2 2993184; fax: + 32 2 2950146.
F o r the present-day scale of nuclear power there is no problem in its fuel supply. Russian nuclear power with its open or semi-closed fuel cycle will be sufficiently provided with fuel from the available reserves of raw materials within the next few decades. An inevitable absolute growth o f the nuclear capacities and an increase o f their contribution to the total fuel balance as well as the extension of regions and the increasing number o f countries using nuclear energy are expected in the future. Then, although it is hard to predict exactly when there comes that time, nuclear power will encounter the problem of nuclear resources, unless it is on the point of recycling nuclear fuel. In Russia the nuclear fuel cycle strategy was established at the stages of formation and intense development of the domestic nuclear power. The two-components nuclear power based on thermal reactors and breeders reactors was proposed. This
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structure assumes a closed fuel cycle: chemical reprocessing of spent fuel with the reuse of both recovered uranium and recovered plutonium. Following this concept, Russia has gained some experience in reprocessing of spent fuel with the recovery of plutonium and its recycling in reactors. The greatest efforts were made on the utilization of plutonium in fast breeders reactors. Works on the use of MOX fuel in VVERs were also conducted. But it should be stressed that the slowdown in the rates of nuclear power development and a surplus of uranium fuel lessened the efforts on development of mixed fuel for VVERs.
2. Russian experience in plutonium utilization As marked above the efforts connected with the use of plutonium in nuclear power have been quite extensive in Russia from the very beginning. Investigation on the use of plutonium as a fuel commenced at the V N I I N M in the 1950s with the development of fuel elements for various fast reactor tests. These early investigations led to the construction in the mid-1960s of a pilot line at 'Mayak'. This pilot line was used to produce cores for the reactors BR-5, IBR-2 and to produce experimental fuel assemblies for the reactor BOR60. The initial investigations of MOX-pelleted fuels were based on mechanical mixing of the individual dioxides of uranium and plutonium. In 1980, a ' P A K E T ' facility was developed at 'Mayak' with the sections for both pelletizing and fabricating fuel elements. The capacity of the facility is 350 kg/year total of uranium and plutonium oxides. In 1980-1981, the first 10 full-length fuel assemblies were manufactured and used to test in BN-350 reactor. At the beginning of 1987 a pilot-industrial facility 'Granat' was designed and constructed at 'Mayak'. MOX fuel production began in April 1988. The facility produced one test subassembly for the BN-350 and has established the baseline for tests in BN-600. Currently five technical processes have been developed for producing mixed oxide pelleted fuels:
• • • • •
mechanical mixing of oxides; sol-gel process ('Zhemchyg'); ammoniac granulation ('Granat'); carbonate co-precipitation; and plasma-chemical conversion. The in-reactor testing of fuel assemblies containing fuel elements with MOX-pelleted fuels commenced at the beginning of the 1970s, first in the BOR-60 reactor, and then in BN-350 and BN-600. Up to now 37 subassemblies with MOX pelleted fuel have been fabricated and irradiated at the BOR-60, BN-350, and BN-600 reactors. A pilot facility for producing MOX fuel elements by vibropacking technology is in operation at the State Scientific Center 'Research Institute of Atomic Reactors' (Dimitrovgrad, RIAR). The production equipment for fabrication of MOX vibropacked fuel from civil and weapons-grade plutonium has proved to be highly reliable and has a capacity of making about 50-60 subassemblies per year for fast reactors. Besides there are two technological lines situated in the glove-boxes for BOR-60 subassemblies production at the RIAR. The vibropacked MOX fuel (354 subassemblies) was tested in BOR-60, BN-350, BN600. Since 1981 the BOR-60 reactor has been operated with MOX fuel made by the vibropacking process. The first experience in the weapons-grade plutonium irradiation was gained in Russia in the experimental reactor BR-10 at the State Scientific Center 'Institute of Physics and Power Engineering' (Obninsk, IPPE), where two cores with the PuO2 fuel were tested. The first core with PuO2 was in operation from January 1959 to November 1964; the second core, from 1971 to 1979. At the industrial pilot-plant BN-350, MOX-fuel assemblies (350 kg of weapons-grade plutonium) were tested, reprocessed and examined. The positive experience gained with the fabrication, operation and post-irradiation examination of MOX pelleted fuel formed the basis for the construction of the first production line of Complex-300 at 'Mayak'. The Complex-300 was design to produce subassemblies for BN-type reactors. The construction was started in 1983. However, the economic situation halted all construction, research and design development work
N. Ponomarev-Stepnoi, D. Tsourikov/ Nuclear Engineering and Design 173 (1997) 293-299
for Complex-300 in 1989. At present, about 50% of the construction has been completed. In Russia the fuel cycle is oriented to the chemical reprocessing of spent nuclear fuel. The RT-1 plant built in 1977 at 'Mayak' can reprocess the spent fuel of VVER-440, BN-350, BN600, research and naval reactors. Its capacity is sufficient to serve the domestic and foreign NPPs with VVER-440 type reactors. The end products of reprocessing are: • uranium containing 2 to 2.4% of U-235 which is re-enriched with highly-enriched uranium obtained in reprocessing spent fuel from naval reactors and used as RBMK fuel; • plutonium (plutonium dioxide) which is enclosed in special packages and transported to a storage facility. At present, the RT-1 plant works at the partial capacity producing 0.6 tons of plutonium per year. At a full capacity, the RT-1 plant can produce 2.5 tons of reactor-grade plutonium per year. The RT-2 plant for reprocessing of spent VVER-1000 fuel was planned and is partially constructed. According to the project the plant must produce uranium dioxide pellets for WE R- 1 0 0 0 fuel elements and plutonium oxide powder for mixed uranium-plutonium fuel for the VVER-1000 reactors. The RT-2 plant construction started in 1977. Since 1991, construction has been suspended due to the lack of financing of the Russian Nuclear Energy Program. Approximately 10% of the planned capital cost had been expended at that time. Closing the VVER-440 and VVER-1000 fuel cycles requires to complete the construction of the RT-2 plant and a complex for production of mixed uranium-plutonium fuel. At present, Russia has accumulated approximately 30 tons of reactor grade plutonium produced from spent uranium-based fuel of VVER-440, BN-600 and BN-350 at the RT-1 plant, this quantity will achieve 47 tons by the year 2005. As a result of strategic and tactical nuclear weapons reduction, significant amounts of weapons grade plutonium, that could be identified as no longer required for military pur-
295
poses, will also accumulate. This amount for Russia is about 50 tons. As discussed above, the Russian Federation has a large stock of plutonium and at the same time some scientific, technological and industrial experience in the utilization of plutonium.
3. Plutonium utilization in nuclear reactors 3.1. Reactor options
At the Moscow Nuclear Safety and Security Summit in April 1996, the G7 countries and Russia expressed their determination to ensure that 'fissile material designated as no longer required for defense purposes will never again be used for nuclear-explosive purposes', and 'that effective management of this material will aim to reduce stocks of separated plutonium and highly-enriched uranium...as soon as practicable'. A considerable analysis has been performed by international experts to identify the available technical options that will provide 'an optimal answer to this problem, both in terms of nonproliferation and of the environment, and also from an economic and technical viewpoint'. A wide range of various alternatives was identified for consideration: • nuclear reactors, • storage, • geological formations, • accelerators, • immobilization, and • stabilization of solutions and other forms. The experts at the Paris meeting on safe and effective management of weapons fissile materials designated as no longer required for defense purposes in October 1996 concluded that there are two options which offer prospects of early progress towards the non-proliferation and other objectives set by the Moscow summit: • utilization of weapons-grade plutonium as MOX fuel in reactors, and • plutonium immobilization. Both these options may be suitable for some countries in their national programs on plutonium disposition.
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In Russia plutonium is viewed as an extremely valuable national resource and a potential source of energy for the future. Thus, Russia favors the burning of plutonium in nuclear reactors. Plutonium immobilization is being considered for disposition of plutonium which is unsuitable for use in MOX fuel. The traditional Russian plutonium policy based on the following points: • safe and reliable storage of plutonium until it may be used in reactors; • utilization of plutonium in reactors; • future orientation on nuclear power centers to find the reliable solution of the non-proliferation problems. This is explained by the desire to use the high energy value of plutonium, the capabilities of the existing nuclear industrial complex, the adopted national concept for long-term nuclear energy development, and the scientific and technological background. The utilization of the weapons-grade plutonium is being considered as a part of its national plutonium strategy. In Russia various variants of burning plutonium in power reactors are been considered: BNs, VVERs, and H T G R . Moreover, Russian experts in collaboration with A E C L (Canada) experts are examining the possibility of plutonium burning in C A N D U reactors. These approaches correspond formally to the term 'spent fuel standard' accepted in the USA. However, in some cases the Russian option of plutonium burning in nuclear reactors involves the possibility of spent fuel reprocessing and recycling of nuclear fuel, including plutonium. First of all, this is true for the BNtype reactors, but the possibility for recycling of spent VVER fuel is not ruled out. At present, for a number of reasons, including approved political decisions on converting the plutonium into spent fuel or other forms equally unusable for nuclear weapons as soon as practicable, current economic situation in Russia, and existing world experience in MOX fuel utilization, the weapons-grade disposition policy has been change. The utilization of MOX fuel should begin using the reactors currently in operation, that is to say BN-600 and VVER-1000s.
3.2. Fast reactors
Russia has large scale experience in developing fast reactor technology. The extensive valuable experience has been gained in mixed oxide fuel fabrication and irradiation tests, development, construction, and operation of fast reactors. The most significant success achieved in the field of Russian fast reactor technology is the construction and operation of the BN-600. The BN-600 reactor was put in operation in 1980 as the third power unit at Beloyarskaya NPP. The successful operating experience of BN-600 is attributed to the appropriate design and technical solutions, high quality in the manufacturing of components, and proper management of reactor operation. This positive experience has allowed Russian organizations to start development of the BN-800 reactor design. The BN-800 reactor has been designed for electricity production and plutonium utilization and meets regulatory safety requirements now in effect in Russian Federation. The core design has been developed for using civil plutonium, but calculations studies performed shown that there are no serious problems to use in BN-800 weapons-grade plutonium. According to the national fast reactor program it was planned to construct three or four MOXfueled BN-800 as well as complete the Complex300. Construction of the BN-800 reactor was started simultaneously at the South Urals and Beloyarskaya NPPs at the end of the 1980s, but both were halted in the early 1990s due to the changing of the economic situation in Russia. The vision of Russia was to utilize one BN-800 located at Mayak place for disposition of weapons-grade plutonium. This design is to use 2.3 tons of weapons-grade plutonium for the initial loading and 1.6 tons for annual feed. Necessary supporting facilities would also be built at Mayak. These facilities include: • a metal-to-oxide conversion facility, • a mixed uranium-plutonium oxide (MOX) fuel fabrication facility, and • an intermediate spent fuel storage facility. These facilities would have a capacity of 3.3 metric tons per year. Given adequate financial
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support the new BN-800 reactor at Mayak would be ready for start-up around the year 2005. Contingent upon adequate financial support, the metal-to-oxide conversion plant and the MOX fuel fabrication plant were both scheduled to start up by the year 2002. At present, Russia considers that an early start on the disposition of excess weapons plutonium in fast reactors can be met by using a hybrid core as a demonstration in the existing BN-600 reactor. The use of MOX fuel in the BN-600 reactor gives rise to the main two problems: • The first problem is the need to improve the fresh fuel handling systems. Such a system can be manufactured and installed during 1997 1998. • The second problems relates to Russian regulatory requirements which say that sodium void reactivity effect (SVRE) must be nonpositive or at least negligibly small. For the existing uranium fuel core in BN-600, the SVRE is negative of about - 0 . 5 % A k / k . The simplest way to introduce plutonium into BN-600 core is to create so called hybrid core with simultaneous using enriched uranium and MOX fuel in the same core. Design aspects of the BN-600 hybrid core for plutonium consumption have been developed. The core design could be completed this or next year. This project could be started by the year 2001 with the completion of a pilot plant for MOX fuel fabrication including metal plutonium to oxide conversion. Different conceptual designs for pilot plant are currently under consideration with European partners. This plant would be able to feed up BN-600 and four VVER- 1000. The scheduled end-of-life of the BN-600 reactor is the year 2010. Thus BN-600 using hybrid core would be able to effect disposition of 5 metric tons of weapons-grade plutonium. 3.3. V V E R type reactors
The utilization of plutonium in VVER-1000 reactors is one of the most realistic options, because reactors of this type are in operation in
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Russia and abroad. There is long standing experience in MOX fuel fabrication and MOX utilization for LWR type reactors in Western Europe. Proven MOX fuel fabrication technology for LWR type reactors, as well as commissioning and operating know-how, and equipment could be available at present time in the framework of international cooperation. The MOX fuel utilization in LWR type reactors does not only meet the spent fuel standard but also degrades the isotopic composition of plutonium to a non-weapons grade level. Seven existing plus three partially complete VVER-1000 and a new generation of VVER type reactors with improved safety are being considered now in Russia for weapons-grade plutonium utilization. The simplest way of involving plutonium in the VVER-1000 fuel cycle being considered now by Russian experts is the direct replacement of a part of uranium fuel by MOX fuel without essential changes in the core design and the unit operating conditions. The physical features of the core with uranium-plutonium fuel pose restrictions on the number of MOX fuel assemblies in the VVER1000 of existing design. Their fraction is about one-third of the core. The extensive program of work on utilization of weapons plutonium in VVERs to substantiate the decision about the loading of one-third of the VVER-1000 core by plutonium fuel assemblies is underway now. This program includes a complex of calculation studies and experiments, in particular: • conducting of the critical experiments with uranium-plutonium fuel; • upgrading and verification of the codes for the calculation of the neutron-physical characteristics of the VVER-1000 cores with plutonium fuel (comparison with the results of the precision calculations made by Russian and foreign codes, analysis of the results of the Russian and foreign critical experiments with plutonium fuel); • complex calculations for the substantiation of the safety with particular emphasis on reactivity accidents; • trial operation of plutonium fuel assemblies in operating VVER-1000s;
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• review of the Western experience in the use of MOX fuel in PWRs. To obtain the experimental data for the verification of the codes the critical experiments with MOX fuel should be conducted. This study is underway now at the IPPE and at the Russian Research Center 'Kurchatov Institute' (Moscow, RRC KI). Alongside with the substantiation of the neutron parameters of cores with uranium-plutonium fuel for licensing purposes it is necessary to substantiate the serviceability of MOX fuel elements. The loop tests of plutonium fuel elements for VVER-1000 are in progress now at the RIAR. A program for development and trial operation of three pilot fuel elements containing weapons plutonium in the VVER-1000 reactor at Balakovskaya NPP has been drawn up. The possibility of the trial operation of these fuel elements is being justified by the neutron-physical calculations being performed at the RRC KI. The program to be carried for the three MOX assemblies includes: • In 1997-1998, manufacturing of three experimental MOX fuel assemblies for irradiation in a VVER-1000 reactor; • Mid-1998, loading of the first W-Pu MOX assembly in the core of a VVER-1000 reactor at Balakovskaya NPP; • In 1999, loading of the two remaining W-Pu MOX fuel assemblies in the core of the same VVER-1000 reactor. It should be mentioned that for the VVER options, MOX fuel fabrication capabilities will be needed as uranium-plutonium fuel for VVER reactors has not produced in Russia. Research and development, design efforts and development of the technology for MOX fuel production are in progress with the collaboration of Western partners. There are grounds to believe that the trial operation of three MOX fuel assemblies in a VVER-1000 reactor might be started in the year 2000 and that the pilot loading of a third of the core in an operating VVER-1000 reactor by MOX fuel assemblies might be made in the year 2004.
3.4. Gas-cooled high-temperature reactors
In November 1993 the M I N A T O M R F addressed to the US Government a proposal on the joint US-Russian Program on development of a G T - M H R reactor plant which could be efficiently used for burning weapons-grade plutonium. The first G T - M H R reactors were suggested to be constructed in Seversk. At present, joint US-Russian development of the Conceptual G T - M H R Project is under way with the financial backing given by the General Atomic (the USA) and M I N A T O M RF. Recently, Framatome (France) has joined the Program. The Conceptual Project is planned to be completed in October 1997. The G T - M H R concept is based on the use of the core with the graphite moderator and helium coolant as well as of the fuel in the form of microspheres with multilayer pyrocarbon and silicon carbide coatings. The G T - M H R consists of a reactor enclosed into a steel high pressure vessel incorporated with the power conversion system using gas turbine cycle. The core consists of hexagonal graphite prism fuel elements based on coated particles. The G T - M H R is characterized by enhanced safety and high efficiency (up to 50%), which make it more economically advantageous comparing with other reactor types. In the reactors of this type weapons-grade plutonium is used in the form of undiluted plutonium dioxide. The employment of microspheres with multilayer coatings of pyrocarbon and silicon carbide allows a high burnup of plutonium: up to 90% of the initial Pu-239 charge, to be reached in a once-through reactor cycle. Plutonium contained in the spent fuel is of no interest for weapons production. The ceramic structure of the spent fuel and the multilayer coating properties make possible its long-term disposal in geological formations without reprocessing. The leaching tests have demonstrated a higher ability of coated fuels to retain wastes as compared with the method using borosilicate glass. It should be stressed also that the use of multilayer coatings would increase the resistance of
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starting plutonium to proliferation and diversions. In the GT-MHR the quantity of useful power generated per a gram of burnt plutonium for once-through fuel irradiation is larger than in any other reactor system. Thus, the concept of weapons-grade plutonium disposition using the GT-MHR includes the following stages: • transforming weapons-grade plutonium into another form, namely, coated particles, which practically rules out the possibility of its use for military purposes; • burning weapons-grade plutonium in the GTMHR reactors with efficient generation of useful power; • long-term disposal of the spent fuel in geological formations. The foundation of the GT-MHR Project is both the solutions proven in the development and operation of foreign high temperature reactors as well as longer than the 30-year Russian experience in designing the HTGR reactors. Russia has evaluated alternative variants for reprocessing 50 tons of plutonium using the GTMHR. One of these variants suggests the construction of three plants, each containing four reactor modules: in Seversk, Krasnoyarsk, and at the 'Mayak' Combine. The first reactor module may be put into operation in 8.5 years after the decision is made, the last one in 6 years after this date. These plants would reprocessed 50 tons of plutonium during 25-30 years after the decision is made. The location of a fuel production facility and a GT-MHR plants in Seversk as well as in Krasnoyarsk and at 'Mayak' having a well organized infrastructure for weapons-grade plutonium handling and security reduces the proliferation risk. As discussed above, the GT-MHR could be efficiently used simultaneously for the production power and for surplus weapons-grade plutonium disposition.
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4. Conclusions
The Russian strategy of utilization of plutonium, being considered as valuable national resource and a potential source of energy, is the inalienable part of long-term National nuclear energy program. The key elements of this strategy are the following: • interim secure storage, and • disposition of plutonium in nuclear reactors. Follow the approved political decisions on safe and effective management of weapons fissile materials designated as no longer required for defense purposes and taking into account the urgency of the problem of reducing the security risks posed by excess weapons plutonium, Russia will begin using existing nuclear reactors for disposition of weapons-grade plutonium, in particular BN-600 and VVERs- 1000. All the same, long-term used of fast breeder reactors as well as high-temperature gas-cooled reactors will continue to be studied by Russia. Russian experience in the utilization of plutonium is limited by fast reactors and there is no industrial production of MOX fuel that would meet current requirements for safety and output capacity. At present, research, development, and design are under way with the collaboration of Western partners. It should be stressed, that MOX fuel manufacturing and operation will be provided by security and accounting measures meeting stringent international standards and ensuring effective non-proliferation control and transparency. The importance of broad international cooperation for safe and effective management of weapons fissile materials designated as no longer required for defense purposes has been recognized by all states having experience in using plutonium. It is necessary now to focus joint efforts on reaching practical and operational results and on creating mechanisms for international cooperation in the financing and management of corresponding projects.