Rabbit Reactor

Atomic energy has passed a new and important milestone. Last week Atomic Energy Commission Chairman Gordon Dean told an Atlantic City meeting that the AEC's "breeder reactor" at arco. Idaho has been pronounced successful: The development multiplies by more than the energy-producing potential of the world's uranium. An analogy spelled out by Dean explained what atomic breeding is.

Dean asked his audience to imagine that the world has only 100 gallons of gasoline, but that when the gasoline is burned in the presence of water, it turns some of the water into new gasoline. If the amount produced is less than the original stock, the world would soon run out of gasoline. But if the amount is greater the gasoline stock could grow bigger and bigger until all the world's water had been turned into fuel.

'Done with Neutrons. Breeding atomic fuel, said Dean, works in somewhat the same way. Natural uranium contains only .7% of fissionable U-235. Nearly all the rest ot it is nonfissionable U-238. But when U-235 fissions (splits in two) and produces heat, it also yields free neutrons. Some of these are needed to keep the reaction going; they make other U-235 atoms split. Some neutrons escape or are absorbed by structural materials in the reactor. The rest of the neutrons enter the nuclei of U-238 atoms and make them turn into plutonium, which is just as fissionable as U-235 and can be used as atomic fuel.

If the reaction produces less plutonium than there was U-235 to start with, the reaction will soon stop, leaving most of U-238 unaffected. But if the amount of plutonium produced is greater, the reaction will continue until all the U-238 has been turned into plutonium. The way to accomplish this scientific miracle (a fuel that breeds like rabbits) is to make a reactor that is extremely economical in neutrons. If more than one neutron from fissioning U-235 is available for turning U-238 into plutonium, the amount of fuel in the charge, instead of being consumed like coal, will grow continually.

This is what has been done at Arco under the direction of Dr. Walter Zinn of the Argonne National Laboratory. The AEC has given few details, but the reactor certainly used new structural materials (such as zirconium) which absorb very few neutrons, leaving enough to breed an excess of plutonium. It must have been running long enough to prove that it actually "breeds."

Energy Unlimited. Chairman Dean points out emphatically that the success of the breeder reactor is not the dawn of a new atomic millennium. Fuel supply is only one of the obstacles that stand in the way of atomic power at competitive prices. But the breeder eliminates any possibility that the world's supply of fissionable material will run out in the practical future. Under the system of burning only the U-235, each pound of natural uranium, containing .007 Ibs. of fissionable materials, was equivalent in energy to about 18,200 Ibs. of coal. The breeding system makes one pound of uranium equivalent to 2,600,000 Ibs. of coal.

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