The path for innovative severe accident neutronics studies in ZPRs - Part I.1 - Analysis of SNEAK-12A experiments for core disruption in LMFBRs

International audienceThe present work details a new benchmark to be produced to the International Community, for dealing with neutronics code validation in the frame of SFRs (Sodium Fast Reactors) severe accidents sequences leading to core degradation and material relocation. The benchmark is based on a complete re-analysis of the SNEAK-12A experimental program, using TRIPOLI-4, MCNP and Serpent-2 Monte Carlo codes as reference tools, and the ERANOS system of codes for deterministic calculations, all based on JEFF-3.1.1 nuclear data libraries. The complete material balance is resumed, and the main degradation sequences are detailed. Preliminary results on available experimental results (k eff) are given, and additional local quantities are calculated, such as axial flux distributions, as well as detector responses in function of the distance to the degraded part. The benchmark offers an excellent opportunity to validate calculation schemes for strongly heterogeneous interfaces, in particular the preparation of homogenized and condensed cross sections for deterministic core calculations, as well as leakage treatment in locally very heterogeneous media. This work is made within the frame of new core design capacities and new ways of conducting experiment in Zero Power Reactors, such as the ZEPHYR project led independently by CEA. The present analysis will be completed by a full nuclear data sensitivity and uncertainty analysis of the reactivity coefficients in a companion paper