Deterministic and Monte-Carlo interpretations of the MASURCA BALZAC-SI internal storage SFR experiment and quantification of uncertainties to nuclear data

Abstract Internal storage is used in fast reactors as it allows burnt fissile assemblies to cool down before being removed from the reactor. These assemblies are usually stored in the neutron shielding zone far from the core to avoid additional induced fissions. The BALZAC-SI experiment performed in the MASURCA Reactor was dedicated to study internal storage characteristics of a SFR-type MOX core. Fission rate distributions throughout the geometry are calculated with both the TRIPOLI-4® Monte-Carlo and the new APOLLO3® deterministic code. Results show that discrepancies up to 20% are obtained on fission rates with the TRIPOLI-4® code, the APOLLO3® code giving similar results to TRIPOLI-4®. Sensitivity and uncertainty calculations of the different responses to nuclear data are performed in order to explain these biases. We show that uncertainties due to nuclear data may explain a large part of the obtained biases, but further investigations are required to explain remaining discrepancies.