Activation analysis capability of the STRAUM and BESNA coupled system for pressurized water reactors

Abstract

Activation analysis is critical for nuclear reactor operation, maintenance, and decommissioning. This study couples the unstructured discrete ordinates transport code STRAUM with the point-depletion code BESNA to perform activation analysis for a typical pressurized water reactor. A problem-dependent 47-group neutron cross section library was generated using the open-source Monte Carlo code OpenMC for transport calculations in STRAUM, while three problem-independent multi-group neutron activation libraries were generated using NJOY based on the JEFF-3.1/A library for activation calculations in BESNA. These neutron spectra obtained from STRAUM show good agreement with the continuous-energy calculation results from MCNP and OpenMC. The relative errors of energy-integrated fluxes in the baffle, barrel and reactor pressure vessel are within 4%. The 47-group neutron spectra were further expanded into 200-group ones, using spectrum conversion ratios obtain from one-dimensional spectral calculations, to enable BESNA simulations with its 200-group activation library. Comparative analyses with MCNP and ORIGEN using a 252-group activation library verify activation capability of the STRAUM and ORIGEN coupled system, where radioactivity differences of most activated nuclides remain within 5%. In particular, BESNA activation calculations using the expanded 200-group fluxes achieve better agreement with reference results than the original 47-group fluxes.