How to Watch Red A-Bombs

Physicists were gravely amused when ex-President Truman observed a few months ago that he was not convinced that the Russians had ever exploded any atomic bombs. The Atomic Energy Commission did not tell in detail how it keeps track of Russian progress, but Dr. James R. Arnold explained one method in the latest Bulletin of the Atomic Scientists.* Any amateur with about $1,000 for apparatus can "watch" Russian atomic explosions from his own backyard.

Independent physicists Norman J. Holter and W. R. Glasscock of Helena, Mont., reported Arnold, collected snow or rainwater and filtered it through cotton. The idea was to locate large deposits of uranium ore by means of the radioactive gases that they give off. Some of the gases turn into solid, radioactive elements, which are carried down by rain.

When cotton, contaminated with natural radioactivity, is tested over a series of days, its activity diminishes according to a definite rule that depends on the "decay rate" of the elements involved. The curve of decay, plotted on a chart, normally consists of portions of two straight lines. On nine occasions in 1951 and early 1952, Holter & Glasscock collected samples that gave far from normal curves. Study showed that they were the decay curves of very complex mixtures of radioactive substances. The fission products remaining after an atomic explosion fit this description exactly.

Most of the "unnatural" samples came after U.S. atomic tests in Nevada, but some of them were collected in Montana when no U.S. fission products could have been in the air. The radioactive material presumably came from the Russian explosion announced by President Truman on October 3, 1951. Another sample may have come from a second Russian test a few weeks later.

*Further details are in Nucleonics, August 1952.

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