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Burying Warhead Plutonium as Waste is Safer and Cheaper Than Burning it in Reactors

Steven Dolley
Research Director

March 28, 1997

The Two Lead Contenders: MOX and Immobilization

Plutonium is a man-made element created by the fissioning (rapid, chain-reaction splitting) of uranium atoms in nuclear reactors. Less than 15 pounds of plutonium---about the size of an orange---is enough to make a nuclear bomb powerful enough to destroy a major city. Nagasaki was devastated by the "Fat Man" bomb containing about 13 pounds of plutonium. During the Cold War, the United States produced over 100 metric tons, and the Soviet Union perhaps as much as 150 tons, of plutonium for use in tens of thousands of nuclear weapons.

With the collapse of the Soviet Union, the United States and Russia have agreed to substantial reductions in their nuclear arsenals. As a result, about 50 tons of plutonium in each nation (a total of 100 tons or more) is likely to be declared surplus to defense needs and require disposal. But plutonium lasts hundreds of thousands of years, an eternity in human terms. Something must be done to minimize the chance that this plutonium might someday be turned back into nuclear weapons.

Both nations have studied this problem for several years, assessing dozens of options, ranging from dumping the plutonium in the ocean, to dropping it down mile-deep wells, to shooting it into the sun. The governments and national science academies of the United States and Russia have concluded that the two most realistic options are: (1) combining the plutonium with uranium into mixed-oxide ("MOX") fuel for irradiation in nuclear power reactors, and (2) immobilization of the plutonium in a mixture of glass or ceramic with highly radioactive fission products, which would be sealed in steel canisters for disposal as waste.

How Would MOX and Immobilization Work?

Both approaches require that the metallic plutonium "pits" be removed from nuclear weapons and converted into an oxide power. In the MOX approach, this powder would be transported to a fuel fabrication plant, where it would be mixed with uranium oxide, made into pellets, and placed in long metal tubes to form fuel assemblies. These fuel assemblies would then be transported to nuclear power plants, where they would be loaded into the cores of the reactors for three to four years of irradiation. The highly radioactive fuel elements would then be discharged and placed in the reactor's spent fuel pool to await final disposal in a geologic repository.

In the immobilization approach, plutonium oxide powder would be transported to a vitrification plant, such as the Defense Waste Processing Facility (DWPF) at the Savannah River Site in South Carolina. The DWPF is now being used to immobilize highly radioactive waste generated by the production of weapon plutonium during the Cold War. In the "can-in-a-canister" approach to immobilization---the simplest and least expensive method---warhead plutonium would be mixed with molten glass and poured into stainless steel cans. These cans then would be placed in larger stainless steel canisters, which would be filled with a mixture of molten glass and intensively radioactive waste. The canisters are then allowed to cool and are stored pending final disposal.

Both approaches produce final waste forms that are highly radioactive and would be likely to kill a thief or terrorist that attempted to steal them. Both approaches "imprison" the plutonium in a waste form, making it inaccessible for weapons use unless the plutonium is chemically separated in an expensive, complex facility known as a reprocessing plant. In this way, these approaches meet the "spent fuel standard" recommended by the U.S. National Academy of Sciences: warhead plutonium would be as difficult to access as the much larger amounts of plutonium now contained in highly radioactive spent fuel from civilian nuclear power plants.

Dual-Track: The Wrong Track

In December 1996, then-Energy Secretary Hazel O'Leary announced that the United States would pursue a "dual-track approach" to plutonium disposition. Research and development would move forward on both the MOX and immobilization approaches, and the President would make a decision in 1998 as to whether one approach, or a combination of both, should be employed. Soon after Secretary O'Leary's departure, the acting head of DOE's Office of Fissile Materials Disposition announced that DOE would "implement both tracks, not just study them for two years." Commercial contracts might even be concluded within the next year for the construction of a MOX fuel fabrication plant and the irradiation of MOX fuel by U.S. nuclear electric utilities. A proposal to send U.S. and Russian plutonium fuel to Canada for use in CANDU reactors is also being seriously considered.

The dual-track approach is being sold as a kind of "insurance policy": if one technology has problems, the other can take up the slack. In reality, by overturning a 20-year U.S. non-proliferation policy opposing the use of plutonium fuels, the policy could waste hundreds of millions, or even billions, of dollars, pose grave risks to human health and the environment, and pose a threat to our national security.

Why Immobilize?