Berkelium is one of the most dangerous and radioactive elements. Oak Ridge was the only place in the world where berkelium could be made for the experiment (test). After the berkelium was made, it had to be purified (cleaned) to make it ready for the experiment. Berkelium has a half-life of only 310 days. This means that after 310 days, half of the berkelium will disappear because of radioactive decay. Oak Ridge could only make a small amount of berkelium (less than 30 milligrams). They had to work fast to purify it before it was lost because of radioactive decay.