Homogenised group constants generation using Monte Carlo codes for diffusion calculation of pebble bed reactor

Abstract

This study is focused on the development of homogenization technique for the ASTRA pebble bed critical facility. The methods of generating homogenized few-group cross sections using continuous energy Monte Carlo codes MCU-PTR and Serpent 2.1.29 for full core diffusion calculation of pebble bed reactor were studied. 13-group cross sections were used in the SHIPR diffusion code to calculate the simplified cores of the ASTRA critical facility with HTGR-type fuel and a graphite reflector. Cross-verification of Serpent and MCU-PTR applied to HTGR system was carried out. Different homogenization schemes were tested for the SHIPR model and compared against Monte Carlo solutions. Diffusion coefficients for the fuel calculated using out-scatter approximation and cumulative migration method (CMM) were compared. It was shown that diffusion coefficients for fuel of pebble bed reactor calculated by CMM may reduce the difference between the diffusion and Monte Carlo simulation. The abilities of Serpent and MCU-PTR for modelling pebble bed reactors were compared.