Word: fissionable
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Dates: during 1950-1959
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...this flow of information is based the official AEC position, recently expressed by Scientist-Commissioner Willard F. Libby. In general. Chemist Libby's view is calm. As a scientist, he knows that fission products from megaton* explosions rise into the stratosphere and circulate round the earth for years. Most threatening of them is strontium 90, whose long half-life (28 years) keeps it potent during its stratospheric circling, and whose habit of lodging for keeps in human bone makes it a probable cause of leukemia and bone cancer...
Better Chemists. Weiss and Shipman dried the clam flesh, reduced it to ash and dissolved the ash in dilute acid. The solution showed characteristic gamma rays that could come only from cobalt 60. This was odd, they thought; cobalt 60 is not a fission product, and it had not been found in other radioactive material, even in samples from much closer to Ground Zero. To make doubly sure. Weiss and Shipman ran a careful analysis. One clam proved to contain one-tenth of a microcurie of cobalt 60; the other had one-third of a microcurie...
Since the dangerously radioactive cobalt 60 is not a product of fission, it must have come from some other element, perhaps nonradioactive cobalt 59, exposed to free neutrons given off by the thermonuclear explosion. It could never have been more than a trace in the sea water, or the careful tests made in the Marshalls just after the explosion would have detected it. But clams are apparently better chemists than men are; they went after the cobalt 60 for reasons of their own and collected an astonishing amount of the radioacitve isotope...
Strontium 90 is probably the most-feared fission product. Chemically similar to calcium, it is absorbed along with calcium by the human system and deposited in the bones, where its persistent radioactivity (half-life 28 years) may cause cancer. Collecting 500 samples of fresh human bone from widely separated parts of the world, the Columbia men analyzed them delicately and concluded that "at the present time, strontium 90 can be found in all human beings, regardless of age or geographic location s . ." The amount is not large. Averaging all the results together, they reckoned that the human race...
...Columbia men do not consider their work complete. It measured only one of the many fission products. It had nothing to do with the genetic perils of radioactivity. It paid no attention to areas (such as the U.S. Southwest) where "local" fallout has been heavy. It used a very small sample: 500 cases out of 2.5 billion humans...