ТЕПЛОФИЗИЧЕСКОЕ ОБОСНОВАНИЕ ПРОВЕДЕНИЯ РЕСУРСНЫХ ИСПЫТАНИЙ ЭКСПЕРИМЕНТАЛЬНЫХ ТВС ВВР-КН В РЕАКТОРЕ ВВР-К

The paper deals with the results of computational and experimental research to justify the safety of life tests of the lead test assemblies with low-enriched fuel. As a result of calculation studies conducted in the Institute of Nuclear Physics of the Republic of Kazakhstan, the eight-tube and five-tube fuel assemblies with thin-walled fuel elements (thickness 1.6 mm), later named FA VVRKN, have been chosen for conversion of the WWR-K research reactor to LEU fuel (19.7% for uranium-235). The new fuel assembly has a developed surface of heat removal which makes it possible to create on its basis a compact core without increasing in flow rate of coolant and to improve the experimental reactor capabilities. The paper presents the results of in-pile LTA test (three experimental LTA VVR-KN were manufactured at the Novosibirsk Chemical Concentrates Plant, Russia) to confirm the design characteristics and to verify the performance of new design of the fuel assemblies with low enriched uranium fuel. We have proven using calculations that the design characteristics of fuel assemblies can achieve in the core of the WWR -K reactor. The paper notes that the main difficulty of this research is the creation of the necessary test modes in the core of the WWR-K reactor because the power of the LTA is over two times higher than that of the regular fuel assembly of a reactor with highly enriched uranium fuel. We have determined that the life test of three LTA in the WWR-K reactor core requires a change in the configuration and composition of the core, and, consequently, the analysis of the test safety. The calculation results have shown that the thermo-technical safety of the WWR-K reactor core is provided during the performance of the three LTA life test.