The so-called Demon Core was a cursed object, a 6.2 kilogram mass of plutonium intended to be installed in a nuclear weapon. Instead, slapdash experimental techniques saw it feature in several ...

This image from 1945 shows Manhattan Project physicist Harold Agnew smiling and holding the plutonium core of one of the world's most devastating weapons. Weighing 14 pounds and responsible for ...

In 1946, a P-239 plutonium core scheduled for detonation-by-nuclear-bomb was harmlessly melted down and reintegrated into the United States’ nuclear stockpile. That was the end of a 14-pound ...

On this day in 1940, the element plutonium was first isolated by researchers at the University of California, Berkeley. Here’s a quiz on it.