Word: pilings
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Dates: during 1940-1949
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Fishing Probabilities. Swaggering little Enrico Fermi, who put the match to history's first atomic chain reaction, led off with a circumstantial account of how a chain-reacting pile works...
...typical pile is a 20-foot block of graphite (pure carbon) interlarded with lumps of fissionable uranium. The chain begins with the capture of a neutron by a uranium atom. When the atom "fishes" (splits by fission), neutrons released by the reaction fly off at more than 6,000 miles a second. To give the neutrons a maximum chance of being captured by other uranium atoms, they are slowed to "thermal" speed-roughly 3 m.p.s. Normally a neutron slows down to that speed after about 110 collisions with carbon atoms...
...controlling fission, the nuclear physicists' big problem was to calculate the probability that a given atom would capture a neutron traveling at a given speed. They found that in a certain type of pile the critical size at which a lump of enriched uranium begins to cook in a nonexplosive chain reaction is 1.5 kilograms (about 3⅓ Ibs.). Theoretically, a pile might heat up to the temperature of the sun (over 6,000°), but no known container can withstand more than 1,500°. The physicists discovered that the simplest way to throttle down a pile...
...sandlotters who might do almost as well as Pittsburgh's seventh-place regulars. The visiting Giants warmed up on the field, while 36 unionized Pirates locked themselves in the dressing room for two hours to argue and take a vote. Outside, newspapermen stood on ladders and a pile of trunks peering in through a high window; Organizer Murphy, also excluded, paced nervously up & down...
Before the uranium pile was developed for atom bombs, artificial isotopes were made by cyclotrons, and were enormously expensive. The pile produces them much more cheaply, for any substance exposed to the hurricane of neutrons which rages inside the pile quickly becomes radioactive. They are still expensive by ordinary standards, but their cost should fall rapidly. Production at Oak Ridge will be supervised by practical Monsanto Chemical...