Modeling Representative Gen-IV Molten Fuel Reactivity Effects in the ZEPHYR ZPR. Part II LFR Analysis

International audienceStudies related to severe core accidents are a key factor in Gen-IV safety. A novel experimentalprogram, related to severe core accidents studies, is proposed for the future Zero-powerExperimental PHYsics Reactor (ZEPHYR), to be built in Cadarache in the next decade. Theinnovative program aims at studying reactivity effects at high temperature during degradation ofGen-IV cores by using critical facilities and surrogate models. The current study introduces theEuropean Lead-cooled System (ELSY) as an additional Gen-IV system into the representativityarsenal of the ZEPHYR, in addition to the sodium-cooled fast reactors. Furthermore, this studyconstitutes yet another step towards the ultimate goal of studying severe core accidents on a fullcore scale. The representation of the various systems is enabled by optimizing the plutoniumcontent in the ZEPHYR MOX fuel. The study focuses on the representativity of reactivity variation from 900DC at nominal state to 3000DC at a degraded state in both ELSY and Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID) cores. The study utilizesthe previously developed optimization sequence, which is based on the coupling of stochasticoptimization process and Serpent 2 code for sensitivity analysis. Two covariance data are used, the ENDF 175-groups for ELSY and the COvariance MAtrix Cadarache (COMAC) 33-groupsfor ASTRID. The effect of the energy groups structure of the covariance data on therepresentativity process is found to be significant. The results for single degraded ELSY fuel assembly demonstrate high representativity factor (>0.95) for both the multiplication factor and the reactivity variation. It is also shown that finer energy group structure of the covariance data leads to dramatic improvement in the representativity factor of the reactivity variation