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September 23, 2008

Exclusive: Constructing Nuclear Weapons for Fun and Profit

Tom Ordeman, Jr.

In previous installments, we discussed the basics of nuclear physics, and the basics of a civil nuclear program. Since the 1940s, nuclear weapons have been the proverbial monkey on the back of the world. Their use ended World War II, arguably saving thousands upon thousands of lives by preventing a bloody American invasion of Japan. America was the undisputed king of the nuclear mountain for only a few years before it was joined by the Soviet Union, and subsequently by a handful of additional countries. Nuclear weapons became a central issue of the Cold War; and at the time of this writing, nine states possess nuclear weapons, while numerous others are in various stages of operating or building nuclear reactors for various purposes. So, since nuclear weapons are such an integral part of international relations, diplomacy, and foreign policy, how do they work?

While nuclear weapons are exceptionally difficult to engineer and build, their basic design is actually relatively simple. While a civil nuclear program uses low-enriched Uranium to achieve a slow, steady, controlled nuclear reaction, a nuclear weapon is based upon the need for a rapid reaction. As such, it uses highly enriched Uranium or Plutonium. The highly enriched Uranium is configured in such a way as to keep it from reaching criticality while in storage or transport. There are two basic designs for nuclear weapons.

The first atomic bomb test was conducted in the United States in July of 1945. The device, nicknamed "The Gadget," was an implosion-type plutonium bomb. In order to create a nuclear explosion, two or more fissile objects must be rapidly combined in order to take them to a super-critical state. Implosion-type devices achieve this by surrounding a sphere of fissile material with specially shaped explosives. When these fissile samples are forced together at an exceptionally high speed, their combined density forces a rapid nuclear reaction, and a massive explosion occurs In addition to "The Gadget," the "Fat Man" weapon used on Nagasaki in August of 1945 was an implosion-type plutonium bomb.

The other basic atomic bomb design is known as the gun-type. The "Little Boy" weapon that was used against Hiroshima in the first instance of atomic warfare employed this design. The gun-type operates by placing two sub-critical pieces of fissile material, typically a hollow "bullet" and a "spike," away from each other in a tube/artillery barrel. The two pieces are then forced together through the detonation of conventional explosives at one end, thus creating a supercritical mass that rapidly and violently detonates. This system can only use highly-enriched Uranium, as the physical properties of Plutonium lead to a high likelihood of a low-yield, premature detonation. For various reasons, there are no known gun-type weapons currently in existence, the design having been abandoned in favor of implosion-type weapons.

One of the inherent challenges of creating a high yield bomb is the fact that once rapid fission begins in a warhead, the violent explosion prevents some of the fissile material from reacting before it gets blown apart. One type of fission device uses a small amount of fusion fuel to increase the speed of the nuclear reaction, thus increasing its yield. This is known as a boosted fission weapon. There is also a design, known as the Teller-Ulam design for the physicist and mathematician who designed it, that uses the X-ray radiation from the primary explosion of a fission bomb to spark the detonation of a secondary fusion bomb.

In more than a half century since the first atomic bomb was detonated in New Mexico, major nuclear powers have translated complex theoretical nuclear physics into a highly refined array of nuclear weapons. These range from extremely large, strategic nuclear warheads, to small tactical warheads that can be mated to a cruise missile. In the 1950s and 1960s, nuclear weapons spawned the development of the same rockets that carried men into space. Between the late 1950s and today, they also compelled the development of the Ohio (United States), Typhoon (Soviet Union/Russia), Vanguard (United Kingdom), and Jin (China) ballistic missile submarines. In the air, it was nuclear weapons that spurred the creation of the B-52 Stratofortress, the B-2 Spirit, and the Tupolev Tu-95 "Bear".

So, if the basic concept behind a nuclear weapon is relatively simple, why is it so difficult to build one? There are several reasons. Perhaps the most difficult is the acquisition of fissile material. In order to create fissile material, one must first find a reliable source of Uranium for the purpose of enrichment. Uranium sources are limited, and they tend to be highly regulated and scrutinized by the International Atomic Energy Agency. Even if a country or group could acquire raw Uranium in any substantial quantity, they would then need to go through the lengthy and expensive process of refinement and enrichment. Not only is this process lengthy and expensive, but one must either purchase or construct the necessary centrifuge cascade, which is also complex, difficult, and subject to intense scrutiny - let us not forget Saddam Hussein's purchases of aluminum tubes.

Generating or procuring fissile material in the form of highly-enriched Uranium or Plutonium would only be the first step in creating a nuclear weapon. Assuming that one could procure not only the fissile material, but also the additional components necessary to turn it into a viable warhead, they would subsequently require highly trained scientists and technicians who could not only manipulate the shape of the fissile core, but also design said core to precise geometric specifications. It is due to these complex, expensive requirements and the lengthy, difficult process that rogue countries such as pre-war Iraq, pre-2003 Libya, and Syria have faced difficulty in developing clandestine nuclear weapons programs.

Assuming one were able to get to this stage in the first place, the mere possession of a viable warhead is pointless without a delivery method. This is where things like ballistic missiles, heavy bombers, and ballistic missile submarines come into play. When rogue nations like North Korea and Iran test ballistic missiles, the international community reacts strongly because ballistic missiles have only one purpose: to deliver weapons of mass destruction. However, as states such as North Korea, Pakistan, and Iran have shown, nuclear weapons programs and delivery systems can be developed with the requisite amount of determination.

So, what were the ramifications of nuclear weapons during the Cold War, and what impact do they have on the present and future state of international relations and global security? These issues will be addressed in the final installment.

FamilySecurityMatters.org Contributing Editor Tom Ordeman, Jr. is a technical writer for a major defense contractor in Hampton Roads, Virginia. Feedback: editorialdirector@familysecuritymatters.org

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