The Making of the Atomic Bomb: 25th Anniversary Edition

by Richard Rhodes

Suddenly Fermi raised his hand. “The pile has gone critical,” he announced. No one present had any doubt about it.1699 Fermi allowed himself a grin. He would tell the technical council the next day that the pile achieved a k of 1.0006.1700 Its neutron intensity was then doubling every two minutes. Left uncontrolled for an hour and a half, that rate of increase would have carried it to a million kilowatts. Long before so extreme a runaway it would have killed anyone left in the room and melted down. “Then everyone began to wonder why he didn’t shut the pile off,” Anderson continues.1701 “But Fermi was completely calm. He waited another minute, then another, and then when it seemed that the anxiety was too much to bear, he ordered ‘ZIP in!’ ” It was 3:53 P.M. Fermi had run the pile for 4.5 minutes at one-half watt and brought to fruition all the years of discovery and experiment. Men had controlled the release of energy from the atomic nucleus. The chain reaction was moonshine no more.