Coupled Thermal-Hydraulic and Neutron-Physical Calculation of IR-8 Reactor’s Fuel Assembly Using MCU-PTR/ATHLET Codes

The paper analyzes the results of modeling one of the types of fuel assemblies used in the IR-8 research reactor. The article is a continuation of the work in which the analysis of hydraulic tests of the eight- and six-tube fuel assemblies IRT-3M was carried out and the nature of the change in the velocity field of the coolant in the cross-section of a standard six-tube fuel assembly, without taking into account the energy release in the fuel elements, was revealed. The calculation was carried out using the program for thermohydraulic calculation ATHLET. This paper presents the results of a connected thermohydraulic and neutron-physical calculation of IRT-3M fuel assemblies. For neutron-physical calculations, the MCU-PTR program was used. The multiphysics approach makes it possible to take into account the effect on the calculation results of changes in the physical properties of the core materials. The paper presents the results of mathematical modeling of stationary operation of a standard IRT-3M fuel assembly with power rate of 600 kW. The coupled work of the neutron-physical and thermal-hydraulic calculation codes has been debugged. The main thermophysical parameters of fuel assemblies are obtained: temperatures of the coolant, cladding, and fuel, and the margin to surface boiling are determined. Using a multiphysics approach, these thermohydraulic parameters were refined. The data obtained can be useful for further calculations of such fuel assemblies using the central channel of the fuel assembly for installing experimental irradiation devices. In addition, the indicated temperature distributions can serve as boundary conditions for design models of irradiation devices used in 3-D CFD codes. The results of this work can be used to determine the permissible power of research reactors of the IRT type: IR-8 at NRC KI (Moscow), IRT-MEPhI at NRNU MEPhI (Moscow), IRT-T at TPU (Tomsk) and WWRSM at INP (Tashkent).

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