Nuclear Criticality Calculations for Canister-Based Facilities - Commercial SNF

The results of the MCNP criticality safety calculations described in this document are presented in Section 7.1. Based on the results presented attributes of the TAD canister-based systems that are important to ensuring their subcriticality are established. These attributes can be categorized according to the criticality control parameter that is impacted. Based on the categorization presented it is seen that moderation control is the underlying criticality control parameter for TAD canister-based systems containing CSNF with a maximum initial enrichment of 5 wt.% 235U/U. However, geometry and neutron absorber control are also important because the design of the canister basket, including the associated neutron absorber panels, directly influence the maximum moderator volume that can be safely tolerated inside the TAD canister cavity in the event of a canister breach. on this basis, it is convenient to define the moderation limits for PWR and BWR TAD canisters according to the geometry and neutron absorber condition prevalent.