Abstract: The cover for exhaust and drain hole on the inner cover of the spent fuel transport container is part of the container’s containment boundary, which uses a double O-type metal seal. After the container is loaded with spent fuel assembly, the cover for exhaust and drain hole should be tested by helium leakage test. During the commissioning of the ENUN 24P spent fuel transport container, the leak test tool provided by the manufacturer was found to be difficult to centering the hole cover and sealing surface, complicate to operate, easy to damage the sealing surface, increased exposure risk of the operator, and the detection method did not consider the natural background value. In view of the above issues, background measurement and an improved detection tool was developed and validated through testing and verification, which can effectively speed up the leakage detection and simplify the operation. The operating personal dose was also reduced. The improved detection tool can be applied to the leakage detection of the cover for exhaust and drain hole of NAC-STC spent fuel transport container which is used domestically.

Key words: spent fuel, transport container, hole cover, helium leak test, improvement