Verification and validation of radiation source term capabilities in STREAM

Abstract

This paper presents the verification and validation of the radiation source term calculation capability implemented in the reactor analysis code STREAM for pressurized water reactor (PWR) spent nuclear fuel (SNF) analysis. Activity, decay heat, neutron and gamma source spectra of irradiated PWR fuel assemblies are calculated with STREAM and ORIGEN and the results obtained are compared. The verification is performed with Westinghouse 15 × 15, 17 × 17 and Combustion Engineering 16 × 16 designs with enrichment of 3–5 wt.% 235U, burnup of 30–60 GWd/t and cooling times of 0.3–1000 years. The radiation source term comparison between STREAM and ORIGEN indicates that the implementation of the source term equations is correct. The validation is done by comparing STREAM calculation results against 91 decay heat calorimetric measurements for 52 PWR fuel assemblies performed at the Swedish central storage facility for spent nuclear fuel, CLAB, and United States Hanford Engineering Development Laboratory (HEDL) and General Electric Morris Operations. The measured fuel assemblies have enrichment of 2–4 wt.% 235U, burnup of 28–51 GWd/t and cooling times of 2–27 years. The comparison between calculated and measured decay heat shows good agreement. For most of the measurements analyzed, the calculated decay heat is within the range of the measurement uncertainty. The average, overall C/E over 71 CLAB decay heat measurements is 1.000 ± 0.017, and 0.997 ± 0.013 for 20 US measurements. Overall, this work demonstrates that STREAM can be reliably used to predict PWR SNF radiation source terms.