Validation of a subgroup method for pressurized water reactor fuel assembly models

Abstract : We are investigating the accuracy of a self-shielding model based on a subgroup method for pressurized water reactor (PWR) fuel assembly models. Until now, APOLLO2 lattice code was using the Sanchez-Coste method based on an $equivalence\ in\ dilution$ with a 281-group Santamarina-Hfaiedh energy mesh (SHEM). Here, we validate a subgroup approach with an improved 361-energy group SHEMat burnup 0 and with isotopic depletion. The aim is to show this new self-shielding technique is more precise than the current one and leads to simpler production computational schemes by avoiding complicated correction algorithms for the mutual resonant self-shielding effects. Compared to a Monte Carlo reference case, the new approach leads to encouraging results in almost every cases. This subgroup technique is proposed as a short-term replacement for the Sanchez-Coste method used in production computational schemes dedicated to the production of multi-parameter cross-section reactor databases.