Modeling and analysis of core-debris recriticality during hypothetical severe accidents in the advanced neutron source reactor

This article discusses salient aspects of severe-accident-related recriticality modeling and analysis in the Advanced Neutron Source (ANS) reactor. The development of an analytical capability that uses the KENO5A- SCALE system is described, including evaluation of suitable nuclear cross- section sets to account for the effects of system geometry, mixture temperature, material dispersion, and other thermal-hydraulic conditions. Benchmarking and validation efforts conducted with KENO5-SCALE and other neutronic codes and compared with critical experiment data are described. Potential deviations and biases resulting from the use of the 16-group Hansen-Roach library are shown. A comprehensive test matrix of calculations to determine the reactivity of various hypothetical configurations that might arise, along with the effects of various parameters on that reactivity, is described. Strong dependencies on geometry, material constituents, and thermal-hydraulic conditions are also discussed as well as the introduction of designed mitigative features.