A comparative numerical investigation of the thermal-fluid phenomena between helium and nitrogen cooled pebble bed reactors

Abstract

The study assesses the thermal-hydraulic performance of a pebble bed type nuclear reactor using nitrogen and helium as coolants. The analysis is done in two separate parts using CFD. First, a segment of the pebbles is modeled and later the whole reactor core. The study assesses the core performance under normal and after reactor shutdown conditions using these two different coolants. The assessment concludes that nitrogen as a coolant candidate for PBR behaves in an acceptable manner in both conditions at a cost of increased pumping power consumption. It is found that under steady state conditions, the heat stored in the pebbles (both for the segment and the whole core) is more in the case of the nitrogen cooled bed compared to the helium cooled bed.