Weaponry, Nuclear

Weaponry, Nuclear

THE EFFECTS OF A NUCLEAR EXPLOSION

DELIVERY METHODS

BIBLIOGRAPHY

The advent of the nuclear weapons age began on July 16, 1945, when the United States tested its first nuclear device in New Mexico at the Alamogordo Bombing Range, now known as the White Sands Missile Range. The successful nuclear explosion, named Trinity, was the end result of the Manhattan Project, a three-year, $1.9 billion ($26.9 billion in 2005 dollars) effort that brought hundreds of the world’s top scientists together to develop a weapon to be used in the United States’ war efforts against Japan and Germany. Nuclear weapons have been used in warfare on two occasions: on Hiroshima, Japan, on August 6, 1945, and on Nagasaki, Japan, on August 9, 1945. Both bombs were dropped by the United States. As of 2006, eight nations were known to possess nuclear weapons: the United States, Russia, the United Kingdom, France, China, Israel, India, and Pakistan. It is possible that North Korea also possesses a nuclear weapon. In 2003 North Korea claimed to have had successfully developed nuclear weapons. While North Korea has not tested a device, most intelligence estimates believe it is likely that it has nuclear capabilities. South Africa once possessed nuclear weapons but dismantled them in 1993 (see Cirincione, Wolfsthal, and Rajkumar 2005).

Nuclear weapons require fissionable materials. When a fissionable atom absorbs a neutron, it will split and release additional neutrons. In a nuclear chain reaction, those neutrons are absorbed into other fissionable atoms that subsequently split and release additional neutrons into other atoms. Nuclear explosions are the result of the rapid release of energy that comes from an uncontrolled nuclear chain reaction.

The two fissionable elements used in nuclear weapons are uranium and plutonium. Uranium is found in nature, but the specific fissionable isotope, uranium235, constitutes only 0.7 percent of all natural uranium. A nuclear weapon, however, requires uranium-235 to make up over 90 percent of the sample. In order to achieve such a high concentration, the uranium must go through an enrichment process that separates uranium-235 from the more common uranium-238 isotope. This has most commonly been achieved with centrifuges, but other methods, such as gaseous diffusion and electromagnetic isotope separation, have also been successful. Plutonium is not found in nature but is a product of the highly radioactive waste from a controlled chain reaction of uranium, usually performed in a nuclear reactor. To extract plutonium from this waste, a sophisticated chemical process is used. For a country seeking to establish a nuclear weapons program, these large-scale industrial and technical processes can be prohibitive.

Critical mass is the smallest amount of fissionable material that is needed to maintain a nuclear chain reaction. How much uranium or plutonium is needed to reach critical mass depends on various elements of weapon design, such as the shape of the fissile core (gun-type or sphere) or the effective use of reflectors to capture errant neutrons. Most estimates are that between 12 to 60 kilograms of weapons-grade uranium and 4 to 10 kilograms of plutonium are needed. In addition, the efficiency and yield of a weapon can be increased by adding a fusion fuel “booster,” such as lithium-6, as found in thermonuclear weapons.

THE EFFECTS OF A NUCLEAR EXPLOSION

The effects of a nuclear explosion are devastating. The majority of damage is caused by three main elements: blast effects, thermal heat, and ionizing radiation. For example, the bomb that was dropped on Hiroshima, a uranium-type device known as Little Boy, had a yield of 12.5 kilotons of TNT. Of the 76,000 buildings in Hiroshima, 48,000 were completely destroyed and another 22,000 were damaged. According to one study of the Hiroshima bombing, the temperature at the site of the explosion reached 5,400 degrees Fahrenheit and “primary atomic bomb thermal injury was found in those exposed within [2 miles] of the hypocenter” (quoted in Rhodes 1986, p. 714). The heat was so intense that people within a half mile of the fireball were reduced to bundles of smoking char. The number of deaths in Hiroshima due to the bomb is estimated to be 140,000, with an additional 60,000 dying from radiation effects over the next five years.

Since these early devices, the yield of nuclear weapons has grown considerably. Although never deployed, on October 30, 1961, the largest nuclear bomb ever tested was the Soviet Union’s “Tsar Bomba,” which had a maximum yield of 100 megatons. More commonly, modern nuclear weapons have yields ranging between one and 5.5 megatons.

For a one-megaton device, the damage would be even more widespread than at Hiroshima and Nagasaki. According to Ansley J. Coale (1985), the shockwaves from a one-megaton blast would destroy modern multistory buildings within 2.9 miles and unreinforced brick and wood buildings within 4.2 miles of impact. Damage to brick and wood buildings would be substantial up to 8.5 miles from the blast. Heat would cause third-degree burns to exposed skin and set fire to clothing within 4.2 miles. The gamma rays produced from such a blast would be almost immediately lethal to any exposed person within 2.5 miles. People exposed at a slightly greater distance (2.7 miles) would have about a 50 percent mortality rate within a month of the explosion. Finally, a nuclear explosion that makes contact with the ground (as opposed to an airblast) would create tremendous amounts of radioactive fallout that could spread over an area as far as 1,000 square miles downwind from the explosion. Estimates of what percentage would be killed in a one-megaton blast on an urban population vary from 11 percent to 25 percent of the total population, with an additional 16 to 25 percent injured. Of course, in a nuclear exchange between advanced nuclear weapons states, multiple bombs would likely be assigned to single targets, resulting in even higher levels of devastation.

DELIVERY METHODS

The three main methods of delivery involve ballistic missiles, aircraft, and submarines. Delivery methods are tied to larger strategic and tactical issues related to nuclear deterrence. Nuclear states, such as the United States and the Soviet Union during the cold war, are concerned that a first-strike nuclear attack from another country could be so damaging that it would successfully eliminate any possibility for retaliation. As a result, states design their nuclear forces in such a way that a sufficient number of weapons would remain to respond with a devastating second strike. Many argue that the sole purpose of any nuclear weapon is to deter other states from ever using one. Some also fear that a terrorist organization could gain possession of a nuclear weapon and smuggle it into a major urban center.

Intercontinental ballistic missiles (ICBMs) are launched from reinforced below-ground silos and have ranges of more than 8,000 miles. Often, ICBMs are equipped with multiple warheads—multiple, independently targeted reentry vehicles (MIRV)—capable of hitting multiple targets. Shorter-range ballistic missiles, which could more easily be used in tactical or battlefield scenarios, have largely been eliminated from the arsenals of major nuclear states.

The appeal of aircraft and submarines is their mobility, as well as an enemy’s consequent difficulty in targeting them. Heavy-duty bombers, primarily equipped with up to twenty short-range attack missiles capable of hitting multiple targets, have the ability to penetrate enemy territory and withstand a great deal of abuse. Submarines carrying strategic nuclear missiles can remain below the surface for long periods and can launch missiles capable of hitting specific targets over distances of hundreds of miles. The possession of a nuclear-equipped submarine fleet gives a country a very credible second-strike deterrent.

Since the end of the cold war, both the United States and the former Soviet Union have worked to decrease their nuclear arsenals. However, many fear that tensions between other nuclear states, such as India and Pakistan, and the ongoing threat of further proliferation could result in the future use of nuclear weapons.

SEE ALSO Defense; Defense, National; Deterrence, Mutual; Disarmament; Proliferation, Nuclear; World War II

BIBLIOGRAPHY

Barnaby, Frank. 2003. How to Build a Nuclear Bomb and Other Weapons of Mass Destruction. London: Granta.

Campbell, Christopher. 1984. Nuclear Weapons Fact Book. Novato, CA: Presidio Press.

Cirincione, Joseph, with Jon B. Wolfsthal and Miriam Rajkumar. 2005. Deadly Arsenals: Tracking Weapons of Mass Destruction. Washington, DC: Carnegie Endowment for International Peace.

Coale, Ansley J. 1985. Nuclear War and Demographers’ Projections. Population and Development Review 11 (3): 483–493.

Nuclear Weapons Data. Bulletin of the Atomic Scientists. http://www.thebulletin.org/nuclear_weapons_data.

Rhodes, Richard. 1986. The Making of the Atomic Bomb. New York: Simon and Schuster.

Schwartz, Stephen I., ed. 1998. Atomic Audit: The Costs and Consequences of U.S. Nuclear Weapons Since 1940. Washington, DC: Brookings Institution Press.

David R. Andersen