3rd WP Probabilistic Criticality Analysis: Methodology for Basket Degradation with Application to Commercial SNF

This analysis is prepared by the Mined Geologic Disposal System (MGDS) Waste Package Development (WPD) department to describe the latest version of the probabilistic criticality analysis methodology and its application to the entire commercial waste stream of commercial pressurized water reactor (PWR) spent nuclear fuel (SNF) expected to be emplaced in the repository. The purpose of this particular application is to evaluate the 21 assembly PWR absorber plate waste package (WP) with respect to degradedmode criticality performance. The degradation of principal concern is the borated stainless steel absorber plates which are part of the waste package basket and which constitute a major part of the waste package criticality control. The degradation (corrosion, dissolution) of this material will result in the release of most of the boron from the waste package and increase the possibility of criticality. The results of this evaluation will be expressed in terms of the fraction of the PWR SNF which can exceed a given k-eff as a function of time and the peak value of that fraction over a time period up to several hundred thousand years.