In a tunnel 40 feet beneath the surface of the Greenland ice sheet, a Geiger counter screamed. It was 1964, the height of the Cold War. U.S. soldiers in the tunnel, 800 miles from the North Pole, were dismantling the Army’s first portable nuclear reactor.

Commanding Officer Joseph Franklin grabbed the radiation detector, ordered his men out and did a quick survey before retreating from the reactor.

He had spent about two minutes exposed to a radiation field he estimated at 2,000 rads per hour, enough to make a person ill. When he came home from Greenland, the Army sent Franklin to the Bethesda Naval Hospital. There, he set off a whole body radiation counter designed to assess victims of nuclear accidents. Franklin was radioactive.

The Army called the reactor portable, even at 330 tons, because it was built from pieces that each fit in a C-130 cargo plane. It was powering Camp Century, one of the military’s most unusual bases