Bias and Range of Applicability Determinations for Commercial Nuclear Fuels

The purpose of this calculation is to apply the process described in the Preclosure Criticality Analysis Process Report (Ref. 2.2.12) to establish the bias for keff calculations performed for commercial nuclear fuels using the MCNP code system. This bias will be used in criticality safety analyses as part of the basis for establishing the upper subcritical limit (USL). This calculation also defines the range of applicability (ROA) for which the bias may be used directly without need to consider additional penalties on the USL. In addition, the range of parameters (ROP) is determined for those MCNP models of commercial nuclear fuels that are expected to be relied upon to form the criticality safety basis for the geologic repository operations area (GROA). The comparison of the ROP of the MCNP models of commercial nuclear fuels and the ROA of the modeled critical benchmarks is used as the basis for determining the need for any additional penalties on the USL.
MCNP is used throughout this document to refer specifically to version 4B2 as described in Section 4.2.1.