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Nuclear Power Deployment Operation and Sustainability Part 11

Tham khảo tài liệu 'nuclear power deployment operation and sustainability part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 340 Nuclear Power - Deployment Operation and Sustainability So it can be concluded that non-traditional chain 231Pa 232U 233U . appears to be more attractive from the standpoint of neutron-multiplying properties as a consequence from the standpoint of extended fuel life-time or achievability of ultra-high fuel burn-up in comparison with traditional chain 232Th 233U 234U . due to the following reasons 1. Combination of two consecutive well-fissionable isotopes 232U and 233U . 2. High rate of their generation from the starting isotope 231Pa whose neutron capture cross-section is larger substantially than that for the starting nuclide 232Th in traditional chain of isotopic transformations. It is noteworthy that 231Pa may be regarded to a certain extent as a burnable neutron poison for fuel life-time 231Pa is burnt up to 80 and converted into well-fissionable isotopes neutron capture cross-section of 231Pa is substantially larger than that of fertile isotope 232Th. As is known the existing LWRs are characterized by thermal neutron spectrum. In advanced LWR designs for example in LWR with supercritical coolant parameters SCLWR different regions of the reactor core are characterized by different neutron spectra depending on coolant density. Thermal spectrum prevails within the core region containing dense coolant y 0.72 g cm3 while resonance neutron spectrum dominates within the core region containing coolant of the lower density y 0.1 g cm3 Kulikov 2007 . Reasonability of 231Pa introduction into fuel composition for the cases of thermal and resonance neutron spectra is analyzed in the next section. 5.2 Reasonability of 231Pa involvement in the case of thermal neutron spectrum Numerical analyses of fuel depletion process were carried out with application of the computer code SCALE-4.3 Oak Ridge National Laboratory 1995 and evaluated nuclear data file ENDF B-V for elementary cells of VVER-1000. The only exception consisted in the use of martensite steel MA956 elemental .