CALCULATION ESTIMATION OF THE REQUIRED HEAT GENERATION IN TESTING FUEL ELEMENTS TO ACHIEVE SUPERCRITICAL PARAMETERS OF THE COOLANT UNDER IRRADIATION IN THE RESEARCH NUCLEAR REACTOR

The paper considers the possibility of achieving the required neutron-physical parameters during irradiation of experimental fuel elements circumfluent with a SCW parameters coolant in the RR IR-8 in order to study the behavior of fuel element cladding under the influence of reactor radiation and coolant with SCW parameters under conditions closest to real operation in nuclear power plant. The possibility of carrying out such experiments in the RR IR-8 will make it possible to contribute to the development of new generation IV nuclear power plants, one of the areas of which is a reactor with super-critical parameters coolant. This direction is promising, as the use of the SCW coolant technology will increase the efficiency of the reactors by 10-12 %. Irradiation experiments in RR IR-8 are carried out using experimental ampoule rigs. During developing the design of an ampoule rig with experimental fuel elements, it is required to provide the necessary heat transfer from the fuel element to the water of the reactor pool, and to maintain the pressure of the SCW coolant by the structure of the ampoule rig vessel. The calculations of heat release in the experimental fuel elements and the accumulation of fluence in the cladding were carried out using the MCU-PTR code with the MDBPT-50 database, which implements the Monte Carlo method. The assessment of heat release in fuel elements during irradiation of an ampoule rig in the cells of the IR-8 core and reflector was carried out. The calculation results of heat release in experimental fuel elements and fast neutron fluxes in the cladding during irradiation in the central channels of fuel assemblies and special blocks made of aluminum, stainless steel, as well as water are presented. An assessment of the contribution of heat release from gamma heating of the ampoule rig structure elements was carried out, which showed that the amount of heat release can be comparable with the energy release due to the fuel fission reaction in an experimental fuel element, which must be taken into account when calculating the temperature irradiation regimes of experimental fuel elements. Obtained results showed the principle possibility of achievement the parameters of the SCW coolant in the ampoule rig on the outer surface of the experimental fuel elements cladding in the RR IR 8.