History: A door filled with concrete used as a shield against the world's most powerful continuous fusion neutron source, 1979. A special bearing in the hinge allowed one person to open or close the door. [1080x1080]

https://i.redd.it/px302m6llal71.jpg via /r/HistoryPorn https://www.reddit.com/r/HistoryPorn/comments/ph5iyd/a_door_filled_with_concrete_used_as_a_shield/?utm_source=ifttt