Closure arrangement for spent nuclear fuel shipping containers

This patent describes a closure system for closing and sealing a cask member having an open end. The closure system comprising a stepped bore in the open end of the cask member. The bore having a first diameter forming a first shoulder within the open end of the cask, and a second larger diameter forming a second shoulder in the bore. The wall of the bore formed by the first diameter having a continuous annular groove therein, and the wall of the bore formed by the second diameter having one or more radially extending slots formed therein, a first closure member adapted to rest upon the first shoulder, a second closure member adapted to rest upon the second shoulder. The second closure member having a continuous peripheral groove, first locking means; second locking means; means for forcing the second locking means into engagement with the second closure member, and sealing members mounted in the first and second closure members