Thermal study of several spent fuel cask distributions in a repository using CFD codes

Abstract

Peak Cladding Temperature (PCT) becomes the reference parameter when assessing the safety during the spent fuel drystorage phase and is dependent on the overall thermal performance. Many variables have been studied in the literature, including the wind speed, air humidity, or heat load. Nevertheless, very limited attention has been given to the impact that cask distribution in an external, or interim, storage facility might have on overall thermal performance. Although this might seem trivial for top-welded canisters with a concrete over pack (i.e. HI STORM-100) due to the lower surface temperatures of the concrete (around 300 K), it should not be applied to bolted-cask with no over pack (i.e. TN-24P with 350 K , or TN-32 with 410 K). Therefore, the need to develop new capabilities arises in ENUSA Industrias Avanzadas S.A., S.M.E in order to obtain more realistic results of spent fuel temperature distribution during transport and storage. As a result, a long-term collaboration project between ENUSA Industrias Avanzadas S.A., S.M.E and Universidad Politécnica de Madrid (UPM) has been launched. In this paper, the thermal performance is compared between a single cask simulation (TN-24P) and multiple cask distributions, using a CFD code. The results show the noticeable impact of the cask distribution on the thermal characterization even for a low powered cask, such as the TN-24P (20 kW). It is expected that the impact on higher powered cask (up to 35 kW) will be greater and therefore it could be worth studying it in future works.