Evaluation of the ESFR End of Equilibrium Cycle State: Spatial Distributions of Reactivity Coefficients

The Horizon 2020 European Sodium-cooled Fast Reactor Safety Measures Assessment and Research Tools (ESFR-SMART) project investigates the behavior of the commercial-size ESFR throughout its lifetime. This paper reports work focused on the end of equilibrium cycle (EOEC) loading of the ESFR, including neutronic analysis, core- and zone-wise reactivity coefficients, and more detailed local mapping of important safety-relevant parameters. Sensitivity and uncertainty analysis on these parameters have also been performed, and a detailed investigation into decay heat mapping was carried out. Due to the scope of this work, the results have been split into three papers. The nominal operating conditions and both zone-wise and local mapping of reactivity coefficients are considered in this paper. The work was performed across four institutions using both continuous-energy Monte Carlo (MC) and deterministic reactor physics codes. A good agreement is observed between the methods, verifying the suitability of these codes for simulation of large, complicated reactor configurations and giving confidence in the results for the most limiting ESFR EOEC core state for safety analysis. The results from this work will serve as the basis for the transient calculations planned for the next stage of work on the ESFR, allowing for more in-depth studies to be performed on the multiphysics behavior of the reactor.