New Atomic Battery

Atomic batteries powered by radioisotopes were one of the first dreams of the Atomic Age, but the dream has taken a long time to turn into reality. Most atomic batteries have produced too little elec tricity, or have stopped working after too short a time. This week the Walter Kidde Nuclear Laboratories, Inc. of Garden City, N.Y. told about a new and apparently practical kind of atomic battery developed for Elgin National Watch Co.

The battery's power comes from promethium 147 (one of the more plentiful byproducts of nuclear fission), which emits low-energy beta particles (electrons). Other atomic batteries have attempted to turn beta particles directly into electric current, but they have often run into trouble because the particles damage the current-yielding parts of the battery. The Kidde-Elgin battery sidesteps this difficulty by mixing the promethium 147 with a phosphor (light-giving substance) and enclosing the mixture in transparent plastic. Electrons from the Pm-147 make the phosphor glow, and its light is turned into electricity by a photoelectric surface of silicon on each side of the plastic wafer. No electrons escape from the plastic, and so the silicon is not damaged.

A battery of this sort, no bigger than the head of a thumbtack, produces 20 microwatts of electricity, which is more than enough to run an electronic watch that Elgin is working on. It will also operate small transistor radios, and Elgin researchers believe that it will eventually be used in hearing aids. When worn in close contact with the human body, the battery must be enclosed in a metal shield that makes it as big as a cough drop (0.2 in. thick, 0.6 in. in diameter). For use in military guided missiles, the atomic battery has the important advantage of not being affected much by temperature changes. At --200DEG F., it yields more current than at room temperature, and it loses only a little power at the temperature of boiling water.

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