Taming the Atom

The atomic dragon's trainers are learning how to gentle him. They have a long way to go. The dragon is still too fractious to harness; his fiery breath is still deadly. But last week the trainers announced important progress; atomic energy may yet do more good than harm. Some day the dragon may be yoked to a plowshare.

At Los Alamos, N.Mex., the atomic Forbidden City, the physicists described a gentle atom bomb. It contains enough "fissionable material" to vaporize its surroundings. But instead of exploding, it smolders as quietly as a furnace banked for the night.

Hazardous Past. The tight-lipped Atomic Energy Commission did not tell all it knows about the new "reactor." The active substance is plutonium, which wrecked Nagasaki. This time it is under exact control. In operation since last November, the tame bomb can be throttled down until "the heat produced in the core of the reactor is no greater than that given off by a kitchen oven."

Essentially, the tame bomb is a "pile" like the original uranium pile at the University of Chicago. But uranium needs slow-moving neutrons to make its atoms split. Thus, a uranium pile is made up of small rods of uranium embedded in a large mass of graphite. Plutonium is different: its atoms can be split by fast neutrons. So a pile made of plutonium needs no graphite or other "moderator." The "Nagasaki model" atom bomb is a plutonium pile that reacts so quickly that it blows itself (and the neighborhood) to bits in millionths of a second.

The bomb-tamers of Los Alamos had a ticklish assignment: to make their bomb explode, but gently, in slow motion. How they solved the problem has not been fully explained. Uranium piles are kept from reacting too fast by inserting cadmium rods into the graphite. The rods absorb neutrons and check the action. The more cadmium, the slower the pile percolates. Some similar method may be controlling the tame plutonium.

The A.E.C.'s report contains a grisly hint about the early stages of bomb taming: "Original design, testing and construction were undertaken by a group working with the late Dr. Louis Slotin, victim of a radiation accident at the Los Alamos Laboratory in May, 1946. . . ."

Hopeful Future. "The heart of the fast reactor," the report explains, "is a small vessel"; but apparently the vessel must be surrounded by a good deal of auxiliary apparatus. "Since the heat is generated in a relatively small region, special cooling provisions are required to prevent overheating of the center of the reactor."

So far, the plutonium pile has been used only for research, where it has been extremely useful: "The fast reactor gives a more intense source of fast neutrons than physicists heretofore have been able to obtain, except during the brief time of the test of the first atomic bomb in the New Mexico desert."

Keeping its secrets close to its chest, the A.E.G. hardly mentioned the practical possibilities. The fast reactor must be surrounded, like its predecessors, by a thick shield to protect the neighborhood from destructive radiation. This limits its use. But the comparatively small size is an obvious advantage. The new pile, further developed and allowed to run faster and hotter, may be the furnace of tomorrow's atomic power plant.

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