ON THE RELIABILITY OF THE ASSESSMENT OF THE THERMAL MODE OF AN UNDERGROUND SPENT NUCLEAR FUEL STORAGE FACILITY BASED ON NUMERICAL MODELING

Abstract

The results of checking the reliability of a previously performed assessment of the thermal mode of an underground facility for long-term storage of spent nuclear fuel in a variant of an integrated reinforced concrete structure on three calculation grids (Coarse, Normal, Fine) are presented. The test was performed on a previously developed three-dimensional computer model in the COMSOL program. The mathematical basis of the model is following: continuity equation, Navier-Stokes equations averaged by Reynolds, standard turbulence model and general heat transfer equation. The consideration of mixed convection conditions was implemented in the "incompressible ideal gas" approximation. It was shown that when using computational grids with high resolution (Normal, Fine), some characteristics may be predicted. They are: temperature increase inside the built-in structure and at the boundary "rock mass - built-in structure" no more than 1°C; a significant change in the structure of the spatial distribution of temperature and an increase in maximum temperatures by about 1°C on the surface of the built-in structure. The duration of calculations in variants with small grids increased approximately 3.4 (Normal) and 7.7 (Fine) times, respectively