One continuing nightmare of the atomic age is the possibility that somewhere, some time, a nuclear reactor may go out of control and blow itself to bits like an overheated steam-age boiler with its safety valve tied down. Builders and promoters of reactors insist that this is highly improbable, but the Atomic Energy Commission wants more facts just in case. So last week it loosed the controls of a reactor and let her blow.
The reactor was a Kiwi, an obsolete experimental nuclear rocket engine built at Los Alamos Scientific Laboratory and used only for brief tests. It was set on an expendable railroad car on Nevada's desolate Jackass Flats and surrounded with a motley array of test objectsnuclear fuels, explosives, radiation detectors, air samplers. A stout steel net was hung to catch any flying debris, and the scientists retired to the control building two miles from the condemned power plant to wait for a northeast wind that would carry any radioactive fallout away from Nevada's inhabited areas.
Fireball & Sparklers. Kiwi was always excessively touchy. In a cylindrical core not much bigger than a garbage can, it could generate 1,000,000 kw. of heat, as much as a large coal-burning power plant. When in normal operation, it was kept in uneasy check by elaborate control systems and cooled by liquid hydrogen with a temperature close to absolute zero. Last week it was given no cooling at all, and the controls that kept its reaction in check were arranged so they could be removed in a fraction of a second. Test Director Keith Boyer hoped that Kiwi would get hot enough to vaporize itself entirely.
When a northeast wind finally blew down the gulch, Boyer pressed the button. A cloud of grey smoke rose up with a ball of fire at its heart; out of it spouted flashes of light like giant Fourth of July sparklers. Observers heard a loud bang and felt a modest shock wave. As the cloud began to dissipate, three Air Force bombers swooped into it, collecting air samples. Then men wearing respirators and full safety suits stepped cautiously within 200 yds. of ground zero. Kiwi had disappeared. Nothing was left on the seared site but the railroad car with its back broken, and a few shreds of burning electric cable.
Poison for Toads. The reactor itself was completely gone, its graphite moderator and several hundred pounds of uranium fuel turned to vapor by temperatures above 8,000°F., roughly the same as the surface of the sun. For a fraction of a second before it evaporated, the reactor had generated millions of times as much energy as Hoover Dam.
The test, Dr. Boyer explained, matched almost exactly the theoretical calculations done at Los Alamos. What Kiwi's flaming death proved was that if nuclear rockets are ever used in space, they will not need explosive charges to break them up after they are spent. They can be turned into small and relatively harmless particles by a signal commanding them to commit suicide.