Preservation of kinetics parameters generated by Monte Carlo calculations in two-step deterministic calculations
North Carolina State University, 3140 Burlington Engineering Labs, 2500 Stinson Drive, Raleigh, NC, 27696-7909, USA
2 Idaho National Laboratory, 2525 Fremont Ave., Idaho Falls, ID, 83415, USA
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Received in final form: 19 July 2022
Accepted: 20 December 2022
Published online: 27 February 2023
The generation of accurate kinetic parameters such as mean generation time Λ and effective delayed neutron fraction βeff via Monte Carlo codes is established. Employing these in downstream deterministic codes warrants another step to ensure no additional error is introduced by the low-order transport operator when computing forward and adjoint fluxes for bilinear weighting of these parameters. Another complexity stems from applying superhomogenization (SPH) equivalence in non-fundamental mode approximations, where reference and low-order calculations rely on a 3D full core model. In these cases, SPH factors can optionally be computed for only part of the geometry while preserving reaction rates and K-effective, but the impact of such approximations on kinetics parameters has not been thoroughly studied. This paper aims at studying the preservation of bilinearly-weighted quantities in the Serpent–Griffin calculation procedure. Diffusion and transport evaluations of IPEN/MB-01, Godiva, and Flattop were carried out with the Griffin reactor physics code, testing available modeling options using Serpent-generated multigroup cross sections and equivalence data. Verifying Griffin against Serpent indicates sensitivities to multigroup energy grid selection and regional application of SPH equivalence, introducing significant errors; these were demonstrated to be reduced through the use of a transport method together with a finer energy grid.
© C. Takasugi et al., Published by EDP Sciences, 2023
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