Secretary of Defense Caspar Weinberger announced that the assembly of neutron tactical weapons had begun and that, when ready, they could be deployed overseas within hours. The neutron bomb was considered by some to be a credible deterrent to potential aggression from Warsaw Pact countries.
The neutron bomb was the result of an attempt to construct a nuclear weapon that was “kind” to the environment. “Neutron bomb” is the popular name for a device that its designers prefer to call enhanced radiation weapon (ERW). It was designed to reduce destructive effects of blast and heat while devoting more of its energy to radiation than does a conventional nuclear weapon.
The majority of neutron bombs produced by the United States had yields equal to one kiloton of high explosives. These bombs were intended to be used in place of ten-kiloton conventional nuclear devices. A ten-kiloton conventional nuclear weapon might deliver its energy as 5 percent prompt radiation (chiefly neutrons and gamma rays), 10 percent radioactive fission products (fallout), 35 percent thermal radiation (heat), and 50 percent blast (air shock). In contrast, the neutron bomb puts nearly 30 percent of its energy into prompt radiation, 40 percent into blast, and 5 percent into fallout. Since most of its prompt radiation consists of high-energy neutrons, the weapon was called the neutron bomb.
The intended use of the neutron bomb was to halt an invasion of Europe by the Warsaw Pact countries, although driving invaders out of Middle Eastern oil fields was suggested. An invading army theoretically needs a two-to-one advantage over a defending army in order to ensure a successful invasion. The Warsaw Pact countries had at least that advantage over the North Atlantic Treaty Organization
One defense plan was to use conventional tactical nuclear weapons to blunt the attack, but the Germans pointed out that this might cause more devastation to their country than the attacking troops did. Supporters of the neutron bomb suggested that if the bomb’s radiation were used to incapacitate tank crews, it would be effective over the same area as a conventional ten-kiloton bomb. Use of the neutron bomb would result in about 80 percent less destruction of civilians and their homes, chiefly because it was only a one-kiloton bomb and secondarily because there was a smaller percentage of energy expended on the blast.
The effect of radiation on an individual depends on the amount of radiation absorbed by the body. The absorbed dose is measured in grays (Gy). (The unit formerly used was the rad; one hundred rad equals one gray.) An acute dose, or a dose received over a short time period, of six grays is generally fatal, although death may occur up to two months later. A supralethal dose of eighty grays produces almost immediate incapacitation; coma and death follow within a few hours to one day. The radiation from the neutron bomb is intended to deliver supralethal doses to enemy troops within about one kilometer from ground zero.
The first atomic bombs were fission weapons using a neutron-induced chain reaction to fission, or split uranium or plutonium nuclei into lighter nuclei such as barium and cesium. This reaction also releases floods of neutrons, gamma rays, and X rays. On detonation, so much energy is released within the small volume of space occupied by the bomb that pressures approach one billion atmospheres and temperatures near 100 million Kelvins. Searing heat in the form of infrared rays flows outward from the fireball at the speed of light, while the rapid expansion of the fireball gases produces the blast shock wave.
Tritium is a heavy isotope of hydrogen. It is radioactive with a half-life of 12.3 years. When heated to millions of Kelvins, tritium nuclei undergo fusion to produce helium, high-energy neutrons, and vast amounts of energy. A neutron bomb may be constructed by adding tritium to a small plutonium fission bomb so that one-half or more of the bomb’s energy comes from tritium fusion, and by avoiding the use of materials in the bomb which absorb neutrons. Such a neutron bomb is a fission-fusion weapon. Pure-fusion neutron bombs have been proposed that would produce even less blast damage and less fallout than ordinary neutron bombs.
If a neutron bomb were detonated 150 meters above the ground, prompt neutrons would produce the supralethal dose of eighty grays 690 meters from ground zero. A person in the open at this distance would probably be killed by blast effects. Although some neutrons would change nitrogen in the air into carbon 14, the resultant carbon 14 radioactivity would be inconsequential. Neutrons would also cause elements in the ground, such as sodium and magnesium, to become radioactive. A rough rule is that the induced radioactivity would be at least a factor of one thousand times less than the neutron radiation that caused it, so that, with the possible exception of the area near ground zero, the induced radioactivity would not be expected to pose a substantial risk for people moving through the area several minutes after a bomb explosion. Moreover, the induced radioactivity would be expected to decay, so that the radioactivity would be ten times less potent after one hour and fifty times less potent after one day.
During World War II, Germany provided bomb shelters covered with about 1.6 meters of concrete for a large percentage of its urban population. This type of protection would adequately shield civilians, since it would reduce neutron dosages by 100,000. Unshielded individuals who were closer than about 1.6 kilometers from ground zero would receive a lethal dose from the prompt neutrons, while those at a distance of about 1.6 to 2.1 kilometers would receive a large but nonlethal dose. In subsequent years, they would suffer an increased fatality rate attributable to cancer and leukemia. The normal death rate from leukemia in the United States is about 7 per 100,000 people. This could rise to as high as 210 per 100,000 people exposed to large but nonlethal doses of radiation, with a similar increase in cancer. Studies of atomic bomb victims in Japan showed that, in pregnant women exposed to prompt radiation, there was about 50 percent combined fetal and infant mortality. About 10 percent of pregnancies resulted in mentally retarded children, while 40 percent resulted in normal children. After the bomb, children conceived by bomb victims were normal. As yet, there have been no genetic effects discovered in the children of atomic bomb victims.
Neutron bombs do destroy buildings. Blast effects would destroy normal civilian structures to about 760 meters out from ground zero, which is only about 25 percent of the area of damage of a ten-kiloton conventional nuclear warhead. A higher detonation altitude would reduce the damage further.
The United States constructed two versions of the neutron bomb, but neither was designed to be dropped from an airplane. One version, designated W79, was a projectile for an eight-inch howitzer (artillery gun) which has a range of about 17 kilometers. Forty of these projectiles were built and placed in the nuclear stockpile, while 380 of the second version, designated W70-3, were constructed. This second version was a warhead for the Lance missile, with a range of about 130 kilometers. These weapons were kept ready for use for about ten years, after which they were included in the nearly seven thousand nuclear warheads and bombs that President George H. W. Bush
Samuel T. Cohen is regarded as the father of the neutron bomb. He got the idea during the mid-1950’s and spent much of the rest of his life attempting to convince various politicians, weapons developers, and military leaders of the advantages he saw in the neutron bomb. A prototype neutron bomb was tested in early 1962, but neutron bomb development was stalled until 1975, when Secretary of Defense James Schlesinger gave its development priority. Schlesinger believed that the neutron bomb would be a more credible deterrent and therefore would make aggression by the Warsaw Pact less likely. The production of the neutron bomb was proposed as part of modernizing the tactical nuclear weapons in Europe by making them smaller, safer to handle, and less productive of fallout. The trigger for the subsequent production of neutron bomb components under President Jimmy Carter, and their assembly under President Ronald Reagan, was an effort to get the Soviet Union to negotiate a pullback of its SS-20 missiles, which NATO regarded as particularly dangerous.
Other countries have neutron bombs: Russian scientists say they tested one as early as 1968; the French tested their version during June, 1980; and the Chinese successfully tested theirs on September 29, 1988. Nevertheless, neutron bombs remain controversial. Since they might be used in situations in which other, more destructive, nuclear weapons would be considered too dangerous, it is argued that they lower the threshold for the use of nuclear weapons. Once any nuclear weapons are used, it is further argued, the likelihood of escalation to total nuclear war is increased. Total nuclear war would be a worldwide environmental disaster greater than any other human-made or natural disaster in recorded history.
Many European critics feared that the neutron bomb might limit a nuclear war to Europe. They preferred the deterrence of the threat or even the risk of nuclear war between the Soviet Union and the United States. Other critics noted that tank killing could be done with even less collateral damage by the use of nonnuclear precision-guided munitions; however, the NATO allies have not been willing to spend enough money to halt massive aggression with conventional forces. In fact, tactical nuclear weapons were introduced as a money-saving alternative to providing and equipping the larger number of soldiers that would realistically be required. Cohen, the neutron bomb’s chief supporter, opposed the U.S. use of the neutron bomb in Europe. He pointed out that the United States has always paid more than its share of NATO’s expenses, and he argued that Europe should shoulder the burden of its own defense.
Since neutron bombs have never been used, their actual environmental effects are limited to those caused by their production, testing, and disposal. Beginning with the Manhattan Project, by 1989 the United States had spent about $250 billion to produce sixty thousand nuclear warheads of all types. It is estimated that it will cost at least another $150 billion to clean up seventeen badly contaminated weapons production sites. This averages out to a total of $6.7 million per warhead. A reasonable estimate for the entire neutron bomb project, including cleanup, totals $2 to $3 billion.
The tritium for neutron bombs was produced at the Savannah River facility in South Carolina. Targets enriched in lithium 6 are irradiated in a nuclear reactor where neutrons react with the lithium to form helium and tritium. These targets are then transferred to a furnace and melted in a vacuum, where the gases driven off are collected and purified. The plutonium for the fission trigger is produced by irradiating uranium with neutrons in a nuclear reactor.
The production of both tritium and plutonium results in the creation of radioactive wastes which are placed in temporary storage. Eventually they must be placed in permanent storage, a procedure that presents some minor technological problems along with major political ones. The magnitude of this permanent storage task can be seen from the fact that, as of 1985, the radioactivity of wastes produced by the nuclear weapons program was equivalent to that of 700 tons of radium. Although they were never used, the manufacture of neutron bombs produced some of this waste, a problematic legacy for the future.
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Cohen, Sam T. “Enhanced Radiation Warheads: Setting the Record Straight.” Strategic Review, Winter, 1978, 9-17. Covers the basics of the neutron bomb and dispels common myths about it. Discusses tactics of its use. -
_______. Shame: Confessions of the Father of the Neutron Bomb. New York: Philadelphia: Xlibris, 2000. Autobiography by the prolific and controversial weapons scientist. -
_______. The Truth About the Neutron Bomb. New York: William Morrow, 1983. Chapters on the bomb briefing and morality should be consulted by any serious student of the subject. Nontechnical and easy to read. An eye-opening account of the real politics that drive weapons programs. -
Kaplan, Fred M. “Enhanced-Radiation Weapons.” Scientific American, May, 1978, 44-51. Describes the neutron bomb and compares it with conventional nuclear weapons. Gives reasons for not using it, with emphasis on the risk of escalation to total nuclear war. Suggests some alternatives. -
Kistiakowsky, George. “The Folly of the Neutron Bomb.” The Bulletin of the Atomic Scientists, September, 1978, 25-29. Gives some of the political history of the neutron bomb and several reasons it should not be used. Recommends an increase in NATO forces and the use of precision-guided munitions. -
Zimmerman, Peter D. “The Physics and Employment of Neutron Weapons.” In Physics, Technology, and the Nuclear Arms Race, edited by D. W. Hafemeister and D. Schroeer. New York: American Institute of Physics, 1983. Describes the neutron bomb and its effects in some detail. Admits that it would force an attacker to disperse his tanks, but suggests that the tanks would benefit from an internal borated plastic neutron absorbing shield. Urges the use of precision-guided munitions in the place of neutron bombs. Somewhat technical.
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