Design validation and BN-800 power unit construction status

In 2006, the Government of the Russian Federation has approved the Federal target program 'Development of nuclear power generation complex in Russia up to 2015'. Along with accelerated construction of large VVER-1000 power units, the program envisages the development of nuclear power innovative technologies. They include the activities in fast neutron reactors, which are involved in the perspective to change nuclear power over to closed fuel cycle, which provides the most efficient use of uranium resources and solution of highly actual political and ecological issues of SNF and RW handling. The central stage of the innovation component of target program deals with construction of fast sodium reactor BN-800 that shall take the important stage in development of fast breeder reactor technology and in generation of closed fuel cycle of nuclear power industry. BN-800 design has been developed on the basis of BN-600 reactor, which operates successfully at Beloyarsk NPP starting from 1980. During this period, the reactor plant shows high and stable indices of reliability, safety and efficiency. Average annual plant capacity factor of power unit from the moment of reaching of design rate (from 1982) is 75.7%. In addition, unscheduled loss of plant capacity factor value due to process equipment failures is small (∼ 2%). The final technical decisions on BN-800 were made in 1990th after Chernobyl NPP accident and following strengthening of requirements for nuclear-power safety. For qualitative safety enhancement, BN-800 design implements some predominantly passive systems (additional emergency protection rods hydraulically suspended in sodium coolant, emergency cooling air HX, tray for confining of core melt under hypothetic accident). During design upgrading, the improvements aimed at enhancement of technical-economic indices were also introduced. The main fact that allows sufficient decrease (by 34%) of RP specific metal consumption is BN-800 power increase by ∼45% at RP vessel overall dimensions close to BN-600. In addition, technical-economic indices are improved due to implementation of one turbo generator instead of three ones as in BN-600 and due to some other new design decisions. BN-800 RP and power unit design as a whole is based on large scope R and D work, experimental check results and BN-600 operation experience. The nowadays R and D work is aimed at the development of missing documentation and special-purpose RP equipment among other things: - development and mastering of MCP speed regulation system; - development and mastering of SG automatic protection system; - development of process fluid parameter measuring equipment; - testing of sodium valves; - development of system of ultrasonic observation in sodium; - development of core design for the initial reactor loading; - validation of power unit service life up to 45 years. Large amount of R and D work is related to the core. BN-800 is directed to mixed uranium-plutonium fuel while BN-600 that was developed to master nuclear reactor technology, uses enriched uranium dioxide. As for BN-800, mixed uranium-plutonium fuel will be fabricated on the basis of both depot stocks of power-producing plutonium and weapon-grade plutonium that will be utilized as excessive for defence. Development of BN-800 spent mixed uranium-plutonium fuel reprocessing production will realize industrial demonstration of closed fuel cycle using fast reactors. As for the first period of fast reactor operation, MOX fuel is acceptable considering its commercial production; however, in future it will be necessary to change over to more dense fuel that provides increased breeding. For BN-800, the nitride-fuel core option has been developed that ensures breeding ratio close to 1 directly in the core. From a perspective of technical-economic indices improvement, the important issue is fuel burnup increase that is connected with improvement of radiation resistance of fuel cladding materials. As for the first period of reactor operation, fuel claddings of austenitic steel ChS-68 c.d. (06Cr16Ni15Mo2Mn2TiVB) mastered in BN-600 with maximum possible burnup of 10% h.a. (damage dose is ∼90 dpa) will be used. Further, it is planned to use improved austenitic steel EK-164 c.d. with maximum possible burnup increase up to 13% h.a., and then, ferrite-martensitic steel will be used. ferrite-martensitic steel EP-450 will be used for FA wrapper from the very beginning, same as in BN-600 reactor. To validate new steel applications for fuel element claddings, corresponding experimental studies are performed in BN-600 reactor. Preparation for construction of the 4th power unit started at Beloyarsk NPP site in 1984; however, new NPP construction was frozen after Chernobyl accident. Now, three concrete-mixing plants and nine fixed tower cranes operate at 150ac site, 'Demag' crane with the lifting capacity of 600t has been assembled to install reactor vessel and heavy equipment tied together. More than 2000 people participate in construction and assembling operations; it is planned to increase personnel quantity. In 2008, a separate building for reactor assembling has been put into operation where reactor vessel components are preliminary assembled. It enables reactor installation acceleration and at the same time, ensures the required quality of assembling and assembly-welding work. BN-800 RP equipment is entirely fabricated at the Russian enterprises. Fifteen large plants are involved as a whole. OKBM bears general responsibility on RP equipment set delivery. This company is RP designer. The effective part of this equipment will be fabricated in OKBM. To reduce the period of power unit construction, the schedule for equipment fabrication and supply is combined with the schedules of building construction and large equipment installation. It is planned complete power unit construction in 2012