Validation of the thermal calculation method and the applicability of confinement monitoring with a full-scale mock-up test of a concrete cask

Abstract

The Mitsui Engineering & Shipbuilding Co. Ltd (MES) has designed and fabricated a full-scale mock-up system that can be used to store spent nuclear fuel (SNF). The system is made up of two parts; a concrete shield that is vented and an inner steel canister that provides containment of the SNF. A benchmark analysis of this storage system was carried out using a combined thermal calculation method. Initially airflows and temperatures outside the canister were calculated using a three-dimensional thermal flow analysis method. The results from this analysis were used as the boundary conditions to calculate the maximum temperatures inside the canister using a two-dimensional heat transfer method. The calculated results agreed well with the measurements and the validity of the combined method of analysis was confirmed. Since all measured temperatures were within their acceptable limits, it was also confirmed that the concrete cask storage system has sufficient heat removal capability. MES has also proposed a new canister confinement monitoring system. It is based on the relationship between the inner pressure of the canister and the temperature of the canister lid and the pedestal. The validity and applicability of the system are confirmed by the full-scale mock-up experiment results. The conceptual design of the monitoring system is considered, and the system can realised at low cost, with high reliability and easy maintenance.