Criticality calculations of spent fuel in deep geological repository

Criticality calculations have been performed for a typical spent fuel disposal canister model filled with PWR fuel elements. Geometric and material properties of the disposal canister and disposal holes were modeled based on the Swedish preliminary disposal concept. Direct disposal of 5% enriched 16 × 16 PWR fuel was considered. We performed the calculations of the neutron multiplication factor using various disposal configurations, depending on the initial enrichment, fuel burnup, canister geometry and disposal holes configuration. The results showed that under normal conditions, when the canister is filled with fresh spent nuclear fuel, the system is deeply sub-critical. If it is assumed that the canister is faulty, leaking and filled with ground water, the system may become critical in the case of fresh fuel.