WASHINGTON — HOW'S this for a trash removal problem: The United States government is right now puzzling over disposal plans for tons of dangerous plutonium and highly enriched uranium culled from dismantled nuclear warheads.
This fissile material, created at great cost over decades by the US nuclear-weapons infrastructure, has been rendered surplus by big cuts in superpower arsenals. Plans call for it to be converted from bomb-ready components into some form that can be protected from terrorists and kept from polluting the environment.
In recent months much attention has focused on the dangers of Russia's excess fissile material stocks. Fewer headlines have mentioned that the US itself now faces a mammoth atomic-bomb cleanup.
``We are very much into the process of trying to solve some of the leftover problems of the cold war,'' sighed a senior Energy Department official at a recent meeting with reporters. ``The fact is we have no clear path.''
At issue is so-called weapons-grade material, plutonium and uranium refined to produce the greatest possible explosive yield. In the days of mutual extended deterrence, this fissile stuff was part of a closed cycle. When old warheads were retired, their plutonium and highly enriched uranium (HEU) was typically reformed and recycled into the hearts of new weapons.
But both the US and Russia are now dismantling between 1,000 and 2,000 warheads a year to meet new arms-treaty limits. All told, current estimates are that the US will end up with 50 metric tons of excess plutonium, which is typically used for the spherical core ``pit'' of a thermonuclear weapon, and perhaps 400 metric tons of extra HEU, used among other things to boost bomb explosions.
Surplus warheads from the former Soviet Union could produce an estimated 100 tons of plutonium and 500 tons of HEU.
Currently, excess plutonium pits are being stored at the Department of Energy's Pantex bomb-assembly site in Texas. HEU goes to DoE's Y-12 plant in Oak Ridge, Tenn., for what is supposed to be interim storage.
Last January, the Energy Department launched a study project to decide where and in what form to keep fissile material for final storage. One decision officials may well make is to embrace a so-called ``spent fuel'' standard for plutonium urged by a National Academy of Sciences report.
That means DoE plans to convert plutonium into some form that makes it as inaccessible for use in a warhead as the plutonium contained in spent nuclear fuel produced by commercial power reactors. ``We're not trying to do away with any of this forever. We're trying to keep it from being used in weapons,'' said the DoE official.
Options for the disposal of the highly enriched uranium stocks are relatively straightforward. It can be easily blended with low-enriched or natural uranium into a product that is both difficult to make into weapons and useful as fuel for nuclear power reactors.
Deciding on disposal of plutonium - the highly toxic material at the heart of ``loose nuke'' nightmares - is more problematic. Options DoE is considering include figuring out how to burn up part of the material in nuclear reactors; immobilization of plutonium by vitrifying it with radioactive waste into glass or ceramic logs; or perhaps putting it directly in canisters and burying it in deep holes in the earth. Location of any final waste disposal sight must be decided upon.
A number of environmentalists are urging that the US pick the glass log option. They claim that immobilizing plutonium with nuclear waste into what in essence would be a large radioactive Lincoln Log would involve much less handling and transport than other options, and thus less chance for accident or theft. Terrorists would be highly unlikely to have access to the complex technology needed to extract plutonium from this type of storage.
This approach would also send the message that plutonium is not an energy resource to be hoarded. Russia, Japan, and a number of other nations consider plutonium a potential energy asset that should not be thrown away lightly.
Using plutonium in reactor fuel ``would undermine our nonproliferation goals by legitimizing plutonium as a nuclear fuel in other countries,'' says Dr. Arjun Makhijani, president of the Institute for Energy and Environmental Research.
But so far Energy Department attempts to convert nuclear waste into glass logs have been dogged by technical problems and expense. Some in the US nuclear industry are lobbying that plutonium instead be disposed of by partially burning it up in reactor fuel.
One firm, Combustion Engineering, has proposed building two big new reactors at a government site in South Carolina to burn plutonium-laced, mixed-oxide fuel.
The Energy Department plans a decision on which method to use by the spring of 1996.