The Manhattan Project: Making the Atomic Bomb

Pile Operation

Excitement mounted at Hanford as the date for pile start-up approached. Fermi placed the first slug in pile 100-B on September 13, 1944. Final checks on the pile had been uneventful. The scientists could only hope they were accurate, since once the pile was operational the intense radioactivity would make maintenance of many components impossible. Loading slugs and taking measurements took two weeks. From just after midnight until approximately 3:00 a.m. on September 27, the pile ran without incident at a power level higher than any previous chain reaction (though only at a fraction of design capacity). The operators were elated, but their excitement turned to astonishment when the power level began falling after three hours. It fell continuously until the pile ceased operating entirely on the evening of the 28th. By the next morning the reaction began again, reached the previous day's level, then dropped.

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