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

Abstract

The Horizon 2020 ESFR-SMART project investigates the behaviour of the commercial-size European Sodium-cooled Fast Reactor (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 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 sensitivity and uncertainty analysis are detailed in Margulis et al. [1]; and the decay heat mapping calculations are reported in Jimenez-Carrascosa et al. [2]. The work was performed across four institutions using both continuous-energy Monte Carlo 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 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 behaviour of the reactor.

Impact of Thermal-Hydraulic Feedback and Differential Thermal Expansion on European Sodium-Cooled Fast Reactor Core Power Distribution

“…Coefficients are generally predicted to within ±50%, although an exception is that TRACE and WIMS predict a substantially different magnitude for 𝑔 (with DYN3D in between them). Static reactivity coefficients for neutronics only are in generally good agreement [19], [39], although the magnitude of the perturbations here is appreciably lower, perhaps making the magnitude more challenging to predict precisely due to numerical discretization and convergence effects.…”

Analysis of sodium boiling initiated by unprotected loss of flow in European sodium fast reactor core with different subassembly designs

“…The reactivity and power evolution during transient are calculated using the built-in point kinetics model of TRACE. The employed reactivity feedback coefficients were calculated using the Serpent Monte Carlo code on the End of Equilibrium Cycle (EOEC) core state (Baker et al, 2022). The reactivity feedback effects considered in the modeling are the Doppler, axial fuel expansion, control rod driveline (CRDL) expansion, sodium density, and void effect, presented in Table 4.…”