BR2 fuel element hydraulic analyses for reactor conversion

Argonne actively supports SCK CEN in the conversion of the BR2 reactor from highly enriched uranium (HEU) to low-enriched uranium (LEU) fuel. In addition to the use of U3Si2-Al fuel, the transition to LEU fuel also required minor modifications to the fuel element geometry. As a result, the hydraulic models used in the safety analysis software, including PLTEMP/ANL, RELAP5-3D, and PARET/ANL, required updates. Hydraulic analyses of the BR2 fuel element were conducted and compared with historically measured data for flow distribution and recent measurements of flow versus pressure drop. Independent subchannel models for the three codes were created to demonstrate consistency with experimental data. The comparisons demonstrate accuracy of the coolant flow distribution, which provides confidence in the models utilized for further safety analyses of reactor conversion.