Advanced resonance self-shielding method for gray resonance treatment in lattice physics code GALAXY

Abstract

A new resonance self-shielding method based on the equivalence theory is developed for general application to the lattice physics calculations. The present scope includes commercial light water reactor (LWR) design applications which require both calculation accuracy and calculation speed. In order to develop the new method, all the calculation processes from cross-section library preparation to effective cross-section generation are reviewed and reframed by adopting the current enhanced methodologies for lattice calculations. The new method is composed of the following four key methods: (1) cross-section library generation method with a polynomial hyperbolic tangent formulation, (2) resonance selfshielding method based on the multi-term rational approximation for general lattice geometry and gray resonance absorbers, (3) spatially dependent gray resonance self-shielding method for generation of intra-pellet power profile and (4) integrated reaction rate preservation method between the multi-group and the ultra-fine-group calculations. From the various verifications and validations, applicability of the present resonance treatment is totally confirmed. As a result, the new resonance self-shielding method is established, not only by extension of a past concentrated effort in the reactor physics research field, but also by unification of newly developed unique and challenging techniques for practical application to the lattice physics calculations.

Resonance self-shielding methodology of new neutron transport code STREAM

“…Equations (10) and (11) are applicable to an infinite array of fuel pin or isolated fuel pin problems. Therefore, for practical fuel assembly problems with various types of fuel pins, the following procedures were developed:…”

“…The gray resonance treatment method [10] also requires the assembly-wise fixed source calculations for each energy group and level of total XS. On the contrary, the optimum rational approximation in this paper computes the individual Dancoff factor by assemblywise fixed source calculation for each energy group only, and smaller size pin-wise fixed source calculations are performed for each energy group, level of optical length and pin type.…”

“…Since the new method does not depend on analytic expression, general geometries can be supported. There are several differences in computing coefficients of rational approximation between the new method in this paper and the gray resonance treatment method [10]. The optimum rational approximation computes the fuel escape probability directly by counting the actual number of neutrons.…”

Refinements of the Pin-Based Pointwise Energy Slowing-Down Method for Resonance Self-Shielding Calculation—I: Theory

“…Owing to this advantage, many lattice physics codes adopt the equivalence theory to generate effective multigroup XSs (Powney and Hutton, 2002;Rhodes et al, 2006). There has been much research into the equivalence theory to improve the accuracy of effective multigroup XSs and the applicability to general geometry (Koike et al, 2012;Godfrey, 2014;Choi et al, 2015a). However, there are still many points missing from the resonance calculation.…”

Recent activities in the field of reactor physics

“…For example, new resonance self- * Corresponding author. Email: mtatsumi@neltd.co.jp shielding methods based on the equivalence theory or the subgroup model have been proposed to improve the accuracy of the transport calculations [6,7]. The generalized equivalence theory and the superhomogeneisation (SPH) method, which have been widely used in current core calculations with the advanced nodal method to mitigate cell/assembly homogenization errors, have been applied to the integro-differential transport equation to further improve the accuracy of whole-core calculations [8,9].…”