2019, Kulikov, G. G., Shmelev, A. N., Apse, V. A., Kulikov, E. G., Куликов, Геннадий Генрихович, Апсэ, Владимир Александрович, Куликов, Евгений Геннадьевич

© 2019 Obninsk Institute for Nuclear Power Engineering, National Research Nuclear University 'MEPhI'. All rights reserved.The purpose of the study is to justify the possibility of improving the safety of fast reactors by surrounding their cores with reflectors made of material with special neutron#physical properties. Such properties of the 208Pb lead isotope as heavy atomic weight, small absorption cross section, and high inelastic scattering threshold lead to some peculiarities in neutron kinetics of the fast reactor with a 208Pb reflector, which can significantly improve the reactor safety. The reflector will also make it possible to generate additional delayed neutrons, which are characterized by «dead» time. This will increase the resistibility of the fission chain reaction to reactivity jumps and exclude prompt supercriticality. Note that the additional delayed neutrons can be generated by the reactor designers. The relevance of the study is that the generation of additional delayed neutrons in the reflector will make it possible to reduce the consequences of a reactivity accident even if the reactivity introduced exceeds the effective fraction of delayed neutrons. At the same time, the role of the fraction of delayed neutrons as the maximum permissible reactivity for reactor safety is depreciated. The scientific novelty of the study is that the problem of the formation of additional neutrons, which in their properties are close to traditional delayed neutrons, has not been posed so far. The authors propose a new method for improving the safety of fast reactors by replenishing the fraction of delayed neutrons due to the time delay of prompt neutrons during their transfer in the reflector. To implement the considered advantages, the following combination is acceptable: lead enriched by 208Pb is used as a neutron reflector while natural lead or other material (sodium, etc.) is used as a coolant in the reactor core.