Testing of the system code designed for simulation of hypothetical beyond design-basis accident on fast breeder reactor

The purpose of the present study was to develop integrated system of codes (ISC) for performing continuous self-consistent calculation of the whole life cycle of fission products (FP) in the nuclear power plant with nuclear reactor unit (RU) equipped with fast reactor (BN) starting from accumulation of FPs in the reactor core to their exit in the environment and migration outside the NPP site territory. SOKRAT-BN integrated code was used in the calculations in combination with KUPOL-BN and NOSTRADAMUS codes. Practical importance of the study is attributed to the development of the ISC for substantiation of BN RU safety. Simulation of hypothetical beyond design-basis accident at the NPP equipped with BN RU accompanied with escape of radioactive isotopes in the reactor premises was performed as the test task. Results of solution of the test problem confirm practical applicability of the developed ISC. Development of the methodology for simulation of migration and precipitation of radioactive impurities in the sodium coolant represents scientific novelty. Software module TRANS-FR designed for simulation of transport of radioactive fission products (RFP) and radioactive corrosion products (RCP) in the primary cooling circuit and in the gas system of the RU was developed and integrated in the SOKRAT-BN ISC taking into account the main physical processes taking place during transport and accumulation of RFP and RCP. Software interface modules for data exchange between the SOKRAT-BN, KUPOL-BN and NOSTRADAMUS codes were developed and tested.