Criticality Evaluation of Degraded Internal Configurations for the PWR AUCF WP Designs

The purpose of this analysis is to provide input on the criticality potential of various degraded configurations to an analysis on the probability of a criticality event in a Pressurized Water Reactor (PWR) Advanced Uncanistered Fuel (AUCF) Waste Package (WP). The objective of this evaluation is to develop multivariate regressions which represent keff for the various degraded configurations as a function of fuel assembly parameters (i.e., burnup, enrichment, age), and configuration parameters (i.e., amount and distribution of remaining basket corrosion products, amount of borated stainless steel plate remaining). Potential design options for reducing the keff of the degraded configurations are also discussed. For guidance in determining the range of parameters which can occur, this analysis begins with a refinement of the WP degradation scenarios developed in previous degraded mode criticality evaluations (Refs. 5.16 and 5.37), as applied to the current reference WP designs (Ref. 5.5).