This was the heaviest door in the world: A shield to protect us from what was inside

The 1950s. Nuclear energy. One door to protect everyone. A door built so heavy that it was resistant to neutron radiation, yet a single person could move it. It was part of the Rotating Target Neutron Source II, known as RTNS II, at the ultra-secret Lawrence Livermore National Laboratory, founded in 1952 in Los Alamos, United States.

Livermore operated under extremely strict security measures, and the legendary door was not designed to keep people out, but to keep neutron radiation in. It functioned as a radiological shield, ensuring that work could be carried out safely outside the facility without health risks. The structure was made of steel and filled with concrete.

The 44-Ton door that was a shield

The door weighed over 97,000 pounds (44,000 kg) and was 8 feet (2.5 m) thick. Its hinges were equipped with bearings that distributed the weight evenly and minimized friction. Because of this design, a single person could open and close it, although very slowly. The door was completed in 1972 and held the title of the heaviest door in the world for more than twenty years.

According to the Guinness Book of World Records, it lost that title in 1994. The new record holder was installed at Japan’s National Institute for Fusion Science. It weighed 720 tons and measured nearly 38.5 feet (11.73 m) high, 37.4 feet (11.4 m) wide, and over 6.5 feet (2 m) thick.

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