Plutonium Can Be Put Safely to Sleep

Safeguarding the nuclear genie is proving both more difficult and more contentious than anyone dreamed when the Cold War ended. For example, the Department of Energy has 50 tons of surplus plutonium, the raw stuff that makes nuclear weapons possible, to get rid of. It is a problem for which there is no ideal answer, merely a spectrum of choices, each of which has advantages and liabilities, and each of which will require acceptance of risks today to eliminate the greater risk of seeing the material diverted to make nuclear weapons tomorrow.

Secretary of Energy Hazel O’Leary has selected two methods to dispose of the plutonium left over from the nuclear weapons program: burn it in reactors and put the spent fuel in a waste repository, or “immobilize” it by vitrification--sealing it in glass--for storage underground.

These are the recommendations of a panel convened by the National Academy of Sciences. The science is on O’Leary’s side. Since nuclear power is out of favor and the American public is averse to taking risks, any method of disposal would be controversial no matter what its merits. O’Leary’s choices have been severely criticized, first for legitimizing the use of plutonium as a fuel for generating electricity, and second for failing to get the Russians to dispose of their own surplus nuclear material in parallel with American efforts.

The 50 tons of Cold War-surplus plutonium in the U.S. could make about 10,000 atomic bombs, so disposal plans must be evaluated on the degree of assurance they offer that the material will be difficult to retrieve and to convert into nuclear weapons. The Department of Energy’s choices do that. But whatever disposal method is used, the final plutonium “product” must be at least as radioactive and treacherous to handle as ordinary spent nuclear fuel, a standard also met by O’Leary’s preferred programs.

The volume of plutonium to be eliminated is not large; the element is so dense that 50 tons occupy less space than a cord of firewood. Straightforward vitrification involves simply mixing plutonium or plutonium oxide with glass to make “logs” about 2 feet long and weighing about 2 tons. These logs would be difficult to move, and the chemistry of extracting the fissile material from the glass is not well understood. The down side: They would be relatively safe to handle because they would not be very radioactive. For this reason, the National Academy of Sciences insisted that vitrification also involve blending unburned plutonium with high-level radioactive wastes from existing spent reactor fuel; neutron-absorbing elements could also be mixed with the glass in order to make extracting weapons-quality plutonium even more difficult.

Conversion of the plutonium to fuel--O’Leary’s alternative solution--is also feasible, although its very mention has drawn fire. For almost two decades, the United States has opposed the use of any plutonium in civilian power reactors because of the risk that legitimizing plutonium and increasing the traffic in the material could lead to the further spread of nuclear weapons. The possible reversal in U.S. policy is strongly opposed by several arms control and environmental advocacy groups, but it is actually a very attractive solution that could reduce the amount of separated plutonium in the world.

During the next decade, electric power utilities in Japan and Europe plan to use as fuel 100 tons of plutonium produced in their reactors. If the United States provided substitute plutonium under tight safeguards, it could reduce those nations’ investment in plutonium refining plants. It would also clean out the American plutonium larder in about 10 years instead of the 20 to 30 now contemplated. Disposal of the spent reactor fuel would be the responsibility of those nations, with the radioactive waste stored under international safeguards in their repositories, not returned to this country.

Alternatively, the United States could invest in a plant to make its own mixed oxide fuel, a mixture of uranium and plutonium oxides, and supply the material to American reactors as cheap fuel. To suppose that this fuel would be more of a proliferation risk than Japanese or French plutonium is to believe that our standards for safety and safeguards are lower than those abroad.

The new American program for eliminating plutonium is deficient on one point: We should have persuaded the Russian Ministry of Atomic Energy to cease its production of plutonium for military purposes and to dispose of its excess stocks as a way to build mutual trust.

All solutions to the plutonium problem require enormous expense and some calculated risk; all of the other plans that were considered by DOE are inferior to the ones selected. The risks and costs that Americans are asked to accept in order to eliminate plutonium are far less than the ones the nation incurred building the nuclear stockpile and guarding it against cataclysm. Today’s list of options is far more appealing than yesterday’s.