Interpretation of PERLE Experiment for the Validation of Iron Nuclear Data Using Monte Carlo Calculations

The Programme d'Etude du Réflecteur Lourd dans Eole (PERLE) critical experiment was recently performed in the EOLE zero-power reactor to provide representative experimental data for heavy stainless steel (SS) reflector physics. It is a UO2 regular 27 × 27 square core surrounded by a 22-cm-thick SS block. The neutron source presents the same spectrum as Gen-III pressurized water reactors (PWRs).

The analysis of measurements with the TRIPOLI4 reference Monte Carlo calculations notably aims at validating ⁵⁶Fe nuclear data in the JEFF3.1.1 library. Large uncertainties are still associated with ⁵⁶Fe nuclear data, in particular for the inelastic cross section ([approximate]10% at 1) since considerable discrepancies have been observed between various international evaluations of the inelastic level.

This paper is dedicated to the analysis of the PERLE experiment. The reactivity worth of the PERLE heavy reflector was measured and compared with the efficiency of both the water reflector and the standard PWR reflector (2-cm-SS baffle). The radial power distribution at the core/reflector interface was measured by direct gamma spectrometry on fuel pins. The TRIPOLI4 analysis gives satisfactory results. The flux attenuation with SS penetration was measured by miniature fission chambers and metallic activation foils, using the fast, intermediate, and thermal response function. Interpretation of flux attenuation measurements shows calculation/experiment discrepancies within the experimental uncertainty. These results highlight that the ⁵⁶Fe cross sections in the JEFF3.1.1 library have been evaluated accurately.