Integrity Assessment of Dual-Purpose Metal CASK after Long Term Interim Storage – Seal Performance under Transport Conditions

Spent fuels generated in nuclear power plants (NPPs) shall be stored until reprocessing as recyclable energy resources in Japan. The quantity of spent fuels stored at each NPP site is increasing, and early realization of the interim storage is expected. Dual-purpose metal cask will be used there and will not be reopened until it is delivered to a reprocessing plant in order to for example minimize personal exposure of radiation. Japan Nuclear Energy Safety Organization (JNES) was established on October in 2003 with the mission to ensure the public safety from the potential hazard of nuclear energy. Study of “Metal Cask Storage Technology Verification” was originally initiated in 1999 at Nuclear Power Engineering Corporation with Japanese government funds, and transferred to JNES and conducted up to the end of FY2003. In the study, many tests were conducted to investigate material property change for main components relating to safety of cask due to degradation during interim storage, furthermore, to verify containment safety during the subsequent transport because there was a possibility of providing the cask with degraded metal gasket for the transport after interim storage and the such cask should be considered fragileness of lid containment system, especially for transport that cask would be provided external force. This paper presents the results and consideration on seal performance during the subsequent transport.