Elements of validation of microscopic depletion for the future EDF calculation scheme based on APOLLO2 and COCAGNE codes

Within the framework of the project N3Cv2 (New Core Calculation Chain), EDF/R and D is developing a new calculation scheme based on the transport-Simplified Pn (SPn) approach. The lattice code used is the CEA deterministic code APOLLO2, while the core code COCAGNE is currently under development at EDF R and D. In order to validate the microscopic depletion scheme, direct comparisons with APOLLO2 results were made on COCAGNE depletion calculations of fuel assemblies. These infinite boundary condition calculations involved depleting the fuel from 0 GWd/t to 60 GWd/t while keeping fixed thermal-hydraulic conditions and boron concentration, so as to be consistent with the depletion process of APOLLO2. It is shown that isotopic concentrations and the multiplication factor (keff) obtained by COCAGNE microscopic depletion solver are consistent with APOLLO2 results. Discrepancies observed are less than 70 pcm for the keff and less than 3% for the isotopic concentrations of relevant heavy nuclides. (authors)