Safety assessment of hybrid heat pipe-integrated spent fuel dry storage cask

Abstract

Various spent fuel dry storage casks have been installed as an interim spent fuel storage with designs in terms of criticality, structural integrity, shielding, passive decay heat removal because on-site spent fuel pools of nuclear power plants have limited storage capacity despite the increase of spent fuel. Although safety of the previously developed dry storage casks have been proven by thermal analyses using experiments and computational fluid dynamics codes, there are issues on structural integrity under long-term storage condition and economics. Therefore, hybrid heat pipe-integrated dry storage cask (UCAN, UNIST canister) was proposed for the reduction of thermal loading and construction cost. In this study, analysis methodology on dry storage cask using thermal-hydraulics system code, MARS, was established with implementation of additional module regarding the hybrid heat pipe for the safety analyses of UCAN under normal storage and accident conditions. The temperature profiles in the cask during normal storage, predicted by the established analysis method, showed reasonable agreement with experimental data of 1/10-scaled test model. Based on the validated MARS analysis method, the safety of full-scale UCAN, that are difficult to realize in the experiment, was analyzed. The calculated temperature variations of UCAN components were lower than those of existing cask design indicating the quantitative enhancement of thermal margin through the installation of the hybrid heat pipe. Consequently, UCAN is expected to be a advanced dry storage cask design in aspect of safety and the proposed analysis method with heat pipe module can reduce the computational resource in terms of thermal analysis of dry storage cask under transient conditions. © 2018 International Heat Transfer Conference. All rights reserved.