Reactor byproducts

 

The neutron flow inside a reactor bombards, and by bombarding changes, the nuclei of many atoms in the reactor. The longer a unit of nuclear fuel remains in a reactor, therefore, the more altered nuclei it contains. Most of the new atoms formed are radioactive nuclides such as cesium-144 or ruthenium-106; a significant number are, if²³⁸U is present, isotopes of plutonium, mostly 239Pu. (Absorption of one neutron by a 238U nucleus turns it into a²³⁹Pu nucleus; absorption of one, two, or three neutrons by a²³⁹Pu nucleus turns it into a²⁴⁰Pu,²⁴¹Pu, or²⁴²Pu nucleus.) Plutonium is found in nature only in trace amounts, but is present in all spent nuclear fuel containing²³⁸U. If it is extracted for use as a reactor fuel or a bomb material, it is considered a useful by-product of the nuclear reactor; otherwise, it is a waste product. In either case, plutonium is highly toxic and radioactive, and remains so for tens of thousands of years unless it is further transmuted by particle bombardment, as in a particle accelerator, reactor, or nuclear explosion. Reactors specially designed to turn otherwise inert²³⁸U into²³⁹Pu by neutron bombardment are termed fast breeder reactors, and can produce more nuclear fuel than they consume; however, all nuclear reactors, whether designed to "breed" or not, produce plutonium.

This fact has a basic military consequence: Every nation that possesses a nuclear power plant produces plutonium, which can be used to build atomic bombs. Plutonium sufficiently pure to be used in a bomb is termed bomb-grade or weapons-grade plutonium, and the process of extracting plutonium from irradiated nuclear fuel is termed reprocessing. (The alloy used in sophisticated nuclear weapons is nearly pure plutonium, but the U.S. Department of Energy has estimated that an unwieldy bomb could be made with material that is only 15 to 25 percent plutonium, with less-unwieldy bombs being possible with more-enriched alloys.) Every nation that possesses a nuclear reactor and reprocessing capability thus possesses most of what it needs to build nuclear weapons. Several nations, including India and Pakistan, have in fact built nuclear weapons using plutonium reprocessed from "peaceful" nuclear-reactor programs. A large (100 MW electric) nuclear power plant produces enough plutonium for several dozen bombs a year.

Besides producing plutonium that can, and sometimes is, extracted to produce nuclear weapons, every nuclear reactor has the feature that if bombed, its radioactive contents could be released into the environment, greatly amplifying the destructive effects of a wartime or terrorist attack. Nuclear reactors thus have a two-edged aspect: as producers, potentially, of weapons for use against an enemy, and as weapons, if attacked, for an enemy.