Fast breeder reactors make the most efficient use of natural uranium. Plutonium recycling with fast breeder reactors increases the efficiency of uranium use by a factor of 60 to 70.
If we try to supply the expected share of nuclear energy to satisfy worldwide energy requirement, a shortage of uranium would be experienced around the middle of the next century. Commercial operation of fast breeder reactors by the middle of next century will become indispensable; so smooth transition of fissile materials from uranium 235 to plutonium can be achieved. If this plutonium recycling takes place, about one million tons of depleted uranium (mostly uranium 238) that the world now possesses could supply about one thousand years of nuclear power at the present world nuclear power generation level.
At the initial stage of fast breeder reactor introduction, light-water reactors and fast breeder reactors will coexist, complementing each other. Plutonium produced by light-water reactors will be used for the initial inventories of fast breeder reactors. Then, fast breeder reactors will start to breed plutonium, increasing the supply capability of nuclear energy by increasing the amount of fissile materials, i.e., the sum of uranium 235 and plutonium. As available fissile materials changes from uranium 235 to plutonium, a smooth transition from light-water reactors to fast breeder reactors could be achieved. The fast breeder reactor system is based on the premise of a full and complete nuclear fuel cycle.
Fast breeder reactors could also respond to the needs of various types of fuel cycles. As adaptable, multipurpose reactors, they can breed plutonium or burn it along with other trans-uranic elements which are nothing more than waste as far as light-water reactors are concerned.
STATUS AND PROSPECT
Fast Breeder Reactors
The importance of recycling plutonium has been recognized since the beginning of nuclear power development. Development of the FBR and the associated fuel cycle began in the United States in the 1940s, in the United Kingdom and Soviet Union in the 1950s, and in France and Japan in the 1960s. Now, India has an operating prototype reactor and China and South Korea are beginning FBR development. Metallic, nitride, and carbide fuels of mixed plutonium and uranium are being developed for FBRs as well as the more familiar mixed-oxide. A total of 21 fast reactors have been constructed so far; 9 of them are working at present.
All of the fast reactors that have operated for a number of years proved to be safe, reliable, and easy to operate. The safety and reliability have been explored in the prototype reactor stage. The economics will be determined in the demonstration reactor stage, which has been currently being evaluated in the design studies of the European Fast Reactor (EFR) conducted jointly by France, the United Kingdom, and Germany, and of the Demonstration Fast Reactor (DFR) by Japan.
The EFR study projects that the construction cost of series-introduced plants will be 10 to 40% more than that of an LWR, depending on the country in which it is sited. The electricity generation cost (including fuel cycle cost) of the EFR is about 10% higher than that of an LWR in France. Construction cost estimates from the Japanese DFR study are 40% higher than that of the LWR for a first plant, falling to 10% higher for series-introduced plants of 1300 MWe.
If the results of research and development now under way in Europe and Japan, and previously in the United States, are applied to the FBR plant design, the construction cost might be cut to close to or less than that for LWRs. The operating cost (including fuel cycle cost) for FBRs is generally lower than that of LWRs when reliability is acceptable, based on European experience. Thus, the total generation cost of FBRs may become more favorable than that for LWRs, even if uranium prices do not increase.
If construction of the next FBR demonstration plants, being designed in Europe and Japan, could start in the 2000s; the commercialization of FBRs by series construction could be demonstrated in the 2010s. Therefore, the global introduction of the FBR and its fuel cycle around 2030 would be technically feasible.
The removal of long-lived radioactive elements from wastes could reduce the environmental burden on repositories. Methods of destroying the long-lived elements in high-level radioactive waste by transmuting them in FBRs are being studied. Although the actual implementation of transmutation disposal methods may well be an extremely long term objective, the demonstration of its potential would reduce concerns about the long life span of some radioactive waste.
The fuel for the current fast reactors is mixed plutonium and uranium oxide (MOX). Mixed nitride and metallic fuels are being developed. The development of MOX fuel is further advanced than that of other fuel types and cycles, and the performance of oxide fuel has already been demonstrated.
A nitride fuel core gives better neutron economy than an oxide fuel core because the neutron energy spectrum is harder. Therefore, a nitride fuel FBR can respond more flexibly to requirements such as conversion/breeding ratio, actinide burning, long core life, or a compact core. Furthermore, the Purex reprocessing process used for oxide fuel can be applied to nitride fuel. However, it may be necessary to use enriched nitrogen-15 in the nitride fuel in order to avoid, for environmental reasons, the formation of carbon-14 from nitrogen-14 during irradiation. In the future, if technologies such as granulated fuel, vibration packing, and sodium-bonded fuel pins and the dry reprocessing process can be applied commercially to nitride fuel, then the nitride fuel systems are likely to become superior in cost-competitiveness to oxide fuel systems. Nitride fuel systems are currently being investigated in France and Japan.
A metallic fuel core has neutronic characteristics similar to a nitride core. Its total fuel cycle has a number of advantages. In the United States, a pyroprocessing technique has been developed whereby spent metallic fuel is reprocessed at the reactor site. The plutonium is not separated from the higher, radioactive actinides; they are recycled together in the reactor and never leave the reactor site. The long-lived radioactive minor actinide elements that otherwise would be disposed of as waste are irradiated in the fast breeder core and transmuted into elements with shorter half-lives, thereby lightening the burden of radioactive waste disposal.
The dry reprocessing methods such as the pyroprocessing technique demonstrated experimentally in the United States, if commercialized, may offer an alternative to aqueous Purex reprocessing. The dry reprocessing methods can be applied not only to the FBR fuelsómetallic, nitride, and oxideóbut also to the oxide fuels of LWRs. Thus, dry reprocessing may bring new options to the overall fuel cycle.
The oxide fuel FBR and fuel cycle systems are in the prototype-to-demonstration stage of development. On the other hand, both metallic and nitride fuel FBRs and their fuel cycle systems are in the development-to-testing stage. Therefore, the commercial feasibility of these systems can only be evaluated after substantial progress has been made.
STRATEGIES AND RECOMMENDED ACTIONS
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