Was Dry cask storage technologically inaccessible 80 years ago?

A single dry cask can be breached, and the contents spilled, causing local contamination and killing the people who breached it. What I'm thinking here is that the fact that breaching a single cask kills the breachers it's impossible to cause massive contamination by accident. You have to know what you're doing, warning signs or no warning signs, if you are able to break in to a geological vault, extract numerous casks and breach a large number of them simultaneously. It requires dogged stupidity in charge of industrial-scale technological abilities. Oh, wait...

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