In March the Japan Atomic Energy Agency (JAEA, formerly JNC (Japan Nuclear Cycle Development Institute)) released the final report of its "Feasibility Study on Commercialized Fast Breeder Reactor Cycle System", Phase II (hereafter referred to as Feasibility Study). We have not previously reported on the Feasibility Study in NIT, so this article gives some background.
In 1997 a committee was established within the Atomic Energy Commission (AEC) to consider how the fast breeder reactor (FBR) should be developed. This committee was established in response to the December 1995 accident at the Monju prototype FBR, which involved a sodium leak and fire. In December 1997 AEC released its decision regarding the future of the fast breeder reactor, determining that it would proceed with development. This decision established FBR's status as "a strong energy option for the future". It proposed that the understanding of the local region should be obtained and that research and development should proceed in a flexible fashion. It also added the following considerations: "internal and external circumstances such as the need to assure a long-term energy source, the importance of safety assurance and of local understanding, tight financial conditions, and placing importance on striving for economic viability". Future nuclear research and development was said to be "important from the point of view of natural resources and the environment". Following AEC's decision, JNC obtained approval from the responsible government departments to carry out jointly with the power companies a feasibility study leading up to the commercialization of FBR. It signed a cooperative agreement with Japan Atomic Power Company and Central Research Institute of Electric Power Industry, established an organization to advance research and the Feasibility Study commenced in July 1999. The objective was "to present in around 2015 an appropriate picture of commercialization of the FBR cycle and the research and development program leading up to the commercialization."
A total of 5 billion yen was poured into Phase I and a report was released in March 2001. The title of the report translates roughly as "Promising Candidate Concepts for Commercialization". Forty concepts were selected for consideration. Candidate coolants were sodium, carbon dioxide, helium, metal (lead-bismuth), water, and molten salts. Candidate fuels were oxides, nitrates, metals, and molten chloride salts. Of these, the following combinations were selected as concepts for consideration in Phase II: sodium coolant with oxide or metallic fuel, gas coolant with oxide or nitrate fuel, lead-bismuth coolant with nitrate or metallic fuel, and water coolant with oxide fuel. Before proceeding to Phase II, the Phase I report was evaluated by a committee established within JNC. JNC selected the members of the committee, but the people selected were from outside JNC.
Sodium cooled reactor selected
Phase II proposed development objectives under 5 headings: safety, economic viability, reduction of environmental burden, effective use of resources, and resistance to proliferation. It considered the above concepts in order to identify a main concept, which would be the major focus of development, and a supplementary concept, which would be developed in order to give flexibility. An interim report was released in August 2004 and the Phase II final report was released this March.
Phase II, which cost 17.2 billion yen, selected the combination of sodium coolant + advanced aqueous reprocessing + oxide fuel produced by a simplified pellet method. Reasons given for choosing this as the main concept included the following: the breeding rate is comparatively high (1.10 assumed), it is the concept for which there is most technical experience, and costs can be reduced by operating large scale plants. The nuclear reactor system would be a "twin plant" with 2 x 1,500 MW reactors. An interim heat exchanger with pump is being considered for the primary system. The advanced aqueous reprocessing method is based on the existing PUREX method, which uses nitric acid, but would eliminate the refining process for the uranium product and the plutonium product. Also, after the spent fuel is dissolved in nitric acid, around 70% of the uranium would be crystallized out. As a result the quantity to be processed later would be reduced. Minor actinides (MA) would be collected and mixed with MOX. Using this method, the quantity of fission products (in the form of MA and other impurities) in the MOX fuel would increase, but in an environment of fast neutrons this would not have much impact. In the simplified pellet method, instead of mixing uranium oxide powder and plutonium oxide powder, uranyl nitrate and plutonium nitrate would be mixed in the desired ratios and then turned into powder form. The fuel fabrication facility would be located alongside the reprocessing plant.
Two patterns were proposed for the supplementary concept. The first pattern uses sodium coolant + pyroprocessing. It uses metal fuel produced by ejection molding. Pyroprocessing is a form of dry reprocessing. The spent fuel is dissolved in a molten salt. First uranium, then plutonium and other elements are removed by electrolysis. Alternatively, the uranium and plutonium can be removed together. In the ejection molding method, pressure difference is used to make molten MOX + MA flow into a cast, which is kept at reduced pressure. This method is said to be suited to high volume production of fuel.
The second pattern uses helium coolant + advanced aqueous reprocessing. Coated particles of nitrate fuel would be used. By making uranium and plutonium into a nitrate compound the fuel's melting point can be raised. The idea is that the helium coolant would be used at over 850oC. Nitrate fuel of diameter 1mm or less would be coated with multiple layers to form fuel particles. Titanium nitrate is one of the materials being considered as a coating material. The high temperature test reactor (HTTR), which commenced operations in March 2000, uses helium gas coolant and coated particle fuel.
It all sounds wonderful, but many technical questions, related to both the main and the supplementary concepts, are left for future technical development. For example, operating large scale plants, uranium crystallization and MA recovery during reprocessing, etc., etc. The schedule from now is in around 2015 to decide on an innovative technology and to present a picture of the commercialization of the FBR cycle and of the research and development program leading up to commercialization.
The Framework for Nuclear Energy Policy (approved by AEC in October 2005) says, "The Government will promptly evaluate the results of Phase II in view of starting on an appropriate picture of commercialization of FBR cycle" from around 2015. There is no allowance for citizens' involvement in the evaluation process. Only technologists and nuclear energy experts will be involved in considering future directions.
Ten years after the Monju accident, the result of the Feasibility Study is that once again the sodium cooled reactor has been chosen as the preferred candidate. One gets the impression that the FBR program has returned to where it started. One also suspects that from the beginning the people involved in the Feasibility Study had a fair idea of what the conclusion would be. In the end, the Feasibility Study was none other than a Feasibility Study for the institutional preservation of the FBR division of JNC (now JAEA).
Finally, it is worth noting that the Feasibility Study proposes equipment included in the major modifications planned for the Monju prototype FBR: for example, the interim heat exchanger with pump and the advanced steam generator (2 x 330 MWt). Perhaps this is because there is no indication of what organization will take the lead in the construction of a demonstration reactor. In the absence of any clear plan for a demonstration reactor, the Feasibility Study perpetuates the fixation with Monju, even though there are no prospects of commercializing this design.