使用済燃料キャスクの貯蔵用金属製緩衝体の開発

抄録

Metal shock absorbers of nuclear spent fuel casks for storage have been developed. The shock absorbers are equipped at both ends of the cylindrical cask to reduce the impact force and maintain the safety functions of the cask in the event of an unexpected drop accident. As a countermeasure to meet long-term storage requirement (against material degradation), the shock absorber was designed with metal instead of usual wood and its energy absorption performance against 2.5 m height drop (maximum hypothetical handling height in nuclear power plants during storage) was evaluated. With the aim of reducing compression stiffness the metal shock absorber was designed from a perforated aluminum block. Two tests were done for static compression characteristics using cubic specimens and energy absorption capacity against 2.5 m drop using 1/4 scale mockup of metal shock absorber. In addition, a drop test using 1/10 scale mockup cask with metal shock absorbers confirmed that it could deform as assumed and reduce the applied acceleration on the cask to a safety level at crash. As a result of the finite element analysis of the cask with designed shock absorbers dropped from a height of 2.5 m that was verified by the drop test, the fitting portion between body and primary lid in the cask remained within elastic deformation thus confirming the design’s validity.