The concept of long-term underground storage for radioactive waste has been explored since the 1950s.

These are the most prominent and common form of underground storage.

So the Russians turned to underground storage at three widely dispersed sites.

Ukraine has accumulated "a record volume of gas" in its underground storage.

Iran has moved almost all its enriched uranium out of underground storage and into plain view.

Much of the hillside is built up on tunnels and underground storage.

Also on the property are two outbuildings that once provided access to underground storage.

The underground storage and lava tubes were an obvious target.

You have also talked about the final solution for underground storage being reversible.

I do have one concern, however, and that is underground storage.