Dose Evaluation for an Independent Spent-Fuel Storage Installation Using MAVRIC

This study reevaluates the dose rates at the site boundary of an independent spent-fuel storage installation (ISFSI) using the MAVRIC computational sequence in the SCALE6 code package. Based on advanced variance-reduction techniques and powerful geometry modeling capabilities, MAVRIC can tackle this large ISFSI shielding problem by directly simulating the radiation transport in a full-scale model. This study started with a benchmark calculation of a single storage cask and then investigated the impact of a fully loaded ISFSI on the dose rates at the site boundary. Because of the short distance to the nearest site boundary, additional shielding to the cask itself or the site is necessary to meet the stringent design dose limit. Compared to the two-step cask-by-cask approach adopted in the original safety analysis report, this method of analyzing the site boundary doses is straightforward and efficient enough to allow us to evaluate the effect of the cask design modification and to test various options for further improvement.