a sealing cover for shipping containers for hazardous materials , such as nuclear fuels , which cover has a twist locking member which may be operated when the cover is under sufficient external force to provide an adequate seal . the cover includes resilient members which , once the cover is locked in place , continue to exert the necessary force on the seals to keep the container tightly sealed . the cover has a safety feature of being tightly locked so that the cover cannot be easily or accidently removed .