Science: Water Boiler

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If anyone wants to build a low-power nuclear reactor, the Atomic Energy Commission will tell him how. Last week the AEC, jointly with Britain and Canada, announced a new "Declassification Guide," which permits the release of such information. Still restricted, of course, is information about large-scale reactors (which make plutonium) and about atomic weapons themselves.

"The three governments," said the AEC, "have determined that the release of information . . . will speed the training of nuclear reactor engineers and technicians and will hasten atomic energy development in these countries, particularly for peacetime applications. It was determined that this information would not aid rival nations in the development of military applications of atomic energy. Low-power research reactors cannot be used for producing atomic weapons or power."

The data released will not be up to date. The newest reactor to be described in detail is HYPO (for High Power), the Los Alamos "Water Boiler" which went into operation in December 1944. A lot of uranium has fissioned since then. In the guarded centers of the AEC's "technical areas" are more advanced reactors. But HYPO is effective enough, comparatively cheap and simple.

Its essential part is a spherical stainless steel tank one foot in diameter. Inside is a water solution of uranyl nitrate which contains 1.9 lb. of fissionable U-235. Water running through a coiled tube keeps the reactor cool, and another tube piercing the sphere gives access to its interior. One big advantage of HYPO is that it is self-regulating. If the chain reaction gets going too fast, the solution heats up and expands, reducing its density and therefore its reactivity. So the reaction slows down automatically until the solution has cooled off. This built-in stability makes HYPO a safe and easy basic trainer for future atomic engineers.