Is the Neutron Bomb Ready?

Out of the ominous debate over nuclear testing, an ominous phrase, "the neutron bomb," echoed across the U.S. last week. It resounded through Congress, leaked into the press, was broadcast on TV and radio. Connecticut's Democratic Senator Thomas J. Dodd, the N-bomb's most enthusiastic proponent, told the Senate: "We are in mortal peril. More than a year has passed since I first spoke on the folly of the test-ban moratorium. I mentioned the neutron bomb would operate as a kind of death ray. It would do next to no physical damage and result in no contamination, but it would immediately destroy all life in the target area. Today I doubt there is a single nuclear physicist of repute who would challenge the neutron bomb from the standpoint of feasibility. It can be built, but nothing can be done to build it until we are free to resume nuclear testing." Dodd hinted that the Russians may soon get the neutron bomb. "At that point," he warned, "we might find ourselves confronted with the terrible choice between surrender and all-out thermonuclear war."

Though there are powerful arguments for the resumption of nuclear testing, scientists and high Government officials who are in the nuclear know do not list the neutron bomb among them. It is a fascinating and frightful possibility, but it is not sufficiently advanced to require explosive testing. That stage of development waits in the scientific future.

General Destruction. The still-theoretical neutron bomb will use a "pure-fusion" reaction, a third generation in nuclear explosions. In old-fashioned fission (Abomb) explosions, nuclei of uranium or plutonium split roughly in half, and the big, heavy fragments are shoved apart by powerful electrical forces. Almost at once they collide with other nuclei, with other materials in the bomb and with the surrounding air. The collisions slow the nuclei down and turn their original energy into heat. The result is a high-temperature fireball that sears its surroundings with heat radiation and expands so violently that it generates a destructive shock wave.

In fission-fusion (H-bomb) explosions, a large part of the released energy appears in the form of high-speed neutrons. Since the neutrons are small and have no electric charge to make atoms repel them, they can penetrate a great deal of matter. So they escape from the fireball and travel a mile or more through the air. They are deadly killers, but existing H-bombs, which are bulky and require fission detonators, generate so much heat and blast that the neutrons they manufacture are lost in the general destruction.

High Temperature. If a small, pure-fusion bomb could be built to work with out a fission detonator, theorists believe that it would send its neutrons farther than the destructive reach of its heat or blast. Starting with 14 MEV (million electron volts) of energy, the neutrons would traverse about a half-mile of air and still have enough punch to kill humans protected by several feet of earth or concrete. There would be blast and heat too, but if the N-bomb was just the right size and was exploded at just the right height above the ground, it would kill by neutrons without setting fires or blowing buildings apart. The effective radius of action would be small--1,000 yds. or so--because neutrons are rapidly absorbed by the surrounding air.

Can such pure-fusion (neutron) bombs be built? As Senator Dodd remarked, scientists will not say that the job is impossible (TIME, Feb. 10). But nearly all agree that it is extremely difficult. Since N-bombs cannot have fission detonators and still act like N-bombs, some other detonator must be found that can raise the temperature of the fusion ingredients to some 1,000,000DEG C. so that they can start to react. So far, no chemical explosive or other nonfission detonator has remotely approached this temperature. Until something comes near this goal, there is little point in demanding explosive N-bomb tests. The best N-bomb that could be built today would no more explode than if it were made of putty.

Devastating Effect. A few proponents of the N-bomb have hinted that the Atomic Energy Commission's scientists, under the direction of Chairman Glenn Seaborg, are not making enough effort to develop it--because they think it cannot or should not be done. Responsible officials in many branches of the Government are quick to respond with categorical denials. Admiral John T. Hayward, head of Navy research and development, says that the AEC's labs are doing all they can, and doing it well. Senators on the Joint Committee on Atomic Energy agree. All authorities insist that while other novel nuclear weapons may be ripe for testing, the fabled N-bomb is not. Some think it will not be ready for nearly five years.

Whenever it is ready, the N-bomb will be a deadly weapon. It would have no ordinary fallout, but its neutrons themselves would make many things radioactive, and the intensity of this effect would depend on the local character of the soil and buildings. Attacking troops might have to wait hours or days before moving in to the enemy's undamaged fortifications.

Though classic battlefields may be few in an all-out war of the future, the N-bomb may prove to have other valuable military uses. Carried aloft by anti-missile missiles, it could do its job without spraying the ground below with radioactive fallout. But perhaps the most devastating effect of the N-bomb would be to make nuclear explosives available to all nations. Plutonium and uranium 235 for fission bombs are expensive and scarce, but fusion ingredients (lithium, deuterium, etc.) are comparatively cheap and plentiful. If they are the only major ingredients needed, the manufacture of N-bombs and big H-bombs to be triggered by them will be an easy matter, once the secret of their construction becomes common knowledge.

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