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The U.S. Department of Energy has decided that most of the plutonium from dismantled nuclear weapons will be made into an experimental fuel (called MOX) for use in commercial atomic reactors. Southeastern utilities are lining up to get involved in this dangerous, large-scale plutonium business (although other utilities also may join the program). Use of reactors does not get rid of the plutonium and further complicates existing nuclear safety and radioactive waste problems.


The MOX project will include numerous shipments of plutonium by truck and/or rail. Transportation of plutonium, even when guarded, opens possibilities for the theft or diversion of plutonium. Plutonium fuel will be stored at the reactor sites before it is loaded for use into the reactor. This puts plutonium safeguarding responsibilities into the hands of commercial utilities, which sometimes have had inadequate security records. Only 13 pounds of plutonium were used to destroy Nagasaki.


Plutonium from nuclear weapons has never been used in fuel for nuclear reactors on more than a research scale. Using weapons-grade plutonium at nuclear reactors would be an experiment that could have devastating results.

In the U.S., most commercial light water reactors are not designed to use plutonium-based fuel. Differences in the characteristics of plutonium fission as compared to the normally-used uranium are likely to create problems. The neutrons from plutonium fission have a higher average energy than neutrons from uranium fission. This will increase the rate of radiation damage to key reactor parts, which could affect reactor control and maintenance. In addition, the rate of fission of weapons-grade plutonium tends to increase with temperature. When fuel temperature increases, so does the rate of fission, which further increases the temperature, and so on. This property of plutonium makes the reaction harder to control.

MOX plutonium fuel also produces more heat and radioactivity than uranium fuel. Uranium fuel that has been used in a reactor core for three years is about a million times more radioactive than unirradiated uranium fuel. This is from the atoms called "fission products" that are actually fragments of the uranium-235 atoms that have been split in the reactor core. These include hundreds of radionuclides like cesium, strontium, iodine, xenon and a host of others. The plutonium atom is even bigger and heavier: when it splits there is a higher yield of these highly radioactive elements. There is also more energy released in the form of heat.


An early 1999 study by the respected Nuclear Control Institute revealed that a severe accident at a civilian reactor powered with plutonium (or MOX) fuel could cause twice as many fatal cancers as an identical accident at a reactor that uses uranium fuel.

Similarly, according to an International MOX Assessment report, the consequences to human health and the environment would increase in case of a severe accident at a nuclear power plant that uses plutonium fuel, because more plutonium and other dangerous radioactive materials would be released into the environment if containment is lost at a reactor. Studies indicate that the doses from a major reactor accident such as Chernobyl could be as much as 2 1/2 times higher to those in the reactor community than would be expected from a uranium core accident.


Using plutonium in a nuclear reactor will not get rid of the plutonium. From 40 –70% of the plutonium from the MOX fuel remains in the waste. Meanwhile, the reactor also produces new plutonium from the uranium oxide in the fuel. The Westinghouse Corporation estimates that putting plutonium in a reactor as MOX fuel may only reduce the amount of plutonium by as little as one percent, compared to the initial content. At best, less than a third of the plutonium inventory is "used up," the rest remains in the radioactive waste.

Indeed, the real point of the MOX program is not to get rid of plutonium—an impossible goal—it is to mix the plutonium with high-level nuclear waste. The idea is that terrorists and rogue nations will be unlikely to approach this lethal waste to attempt to steal the plutonium. On the other hand, no nation yet has a workable, scientifically-defensible solution for its radioactive waste problem. Use of MOX will exacerbate this problem..

All reactor waste contains some plutonium. Thus, plutonium levels in "low-level" waste also could be expected to increase by use of MOX-powered reactors.

The radioactive waste produced by the plutonium fuel program would further aggravate existing radioactive waste problems. Current forms of irradiated fuel storage, in liquid pools or in dry containers, are vulnerable to heat load and possible criticality. MOX fuel, which is thermally hotter and is likely to have a higher concentration of plutonium that could still fission, may challenge these storage options. Thermal load and criticality are also key issues for any geologic repository concept. There is currently no way to safely store this kind of waste for the length of time that it will remain a threat. Plutonium-239 remains hazardous for 240,000 years.


Although MOX fuel has been used occasionally in Europe, it is not made with such a high percentage of plutonium-239 as is contemplated for the United States. This form of plutonium is the material of choice for nuclear weapons precisely because it is easiest to explode. Obviously, this is not the goal in reactor operation. Compounding the concern about the use of a weapons material is the disclosure that the plutonium is not pure. In order to make the nuclear weapons, other ingredients were added to the plutonium. One of these is Gallium, which has not been put in a reactor core before, and which interacts with zirconium, one of the metals composing the fuel rod’s "cladding."

Compromise of fuel cladding can cause a host of problems including greatly increased releases of radioactivity to air and water. People living near the Pilgrim nuclear power reactor in Massachusetts had a 400% greater chance of suffering leukemia than those who lived upwind during the years when that reactor was using fuel with faulty cladding. The stakes of current reactor operation are very high without compounding them with MOX fuel use.

Prepared by Carrie Benzschawel, Nuclear Energy Information Service, Evanston, IL

For more information, contact: Nuclear Information and Resource Service,
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