Energy Officials Eye New Options for Disposing of Weapons-Grade Plutonium

Fourteen years after Russia and the United States agreed to each get rid of 34 metric tons of surplus weapons plutonium, the projected cost of building and operating a plant in South Carolina to turn the surplus U.S. plutonium into reactor fuel has increased to at least $31 billion, according to a recent U.S. Department of Energy report.

A cheaper alternative, the report says, is a method called downblending and disposal, which was the subject of a 4 June panel discussion organized by the AAAS Center for Science, Technology and Security Policy (CSTSP).

In downblending, the plutonium would be mixed with a chemically inert material, called an inhibitor, and buried in deep salt caverns in New Mexico at the federal government's Waste Isolation Pilot Plant (WIPP). The Energy Department report estimated that the downblending approach would cost $8.78 billion in new spending.

But the method faces substantial regulatory and political hurdles, according to Miles Pomper, a senior research associate at the Monterey Institute of International Studies. The United States would need Russian approval for any changes in their agreement, signed in 2000, on disposal of surplus weapons plutonium.

Moreover, the plant in South Carolina is more than half complete and both the Senate and House authorization bills for the Energy Department budget include funding for continued construction. South Carolina has filed a lawsuit seeking to force the federal government to complete the plant, which was put on "cold standby" when the costs escalated and the Energy Department decided to consider other options.

"This is a pretty live political issue right now," Pomper said.

There also are questions about the availability of WIPP, which opened in 1999 as a deep geologic repository for radioactive wastes generated during the research and manufacture of nuclear weapons. The facility was shut down in February after a release of radioactivity was vented into the atmosphere. A drum of nuclear waste heated up and leaked, possibly because some chemically incompatible materials in the drum (including an absorbent similar to kitty litter) interacted to cause combustion within the drum.

Assuming the WIPP eventually reopens, the 29 April Energy Department study on plutonium disposal options noted that a federal statute will have to be amended to accommodate the additional volume of waste represented by the 34 metric tons of surplus weapons plutonium at the site.

Edwin S. Lyman, senior scientist at the nonprofit Union of Concerned Scientists, questioned that conclusion. He told the AAAS gathering that a new disposal package has been designed that could nearly double the amount of plutonium to be packed into each waste drum. The criticality control overpack, as it is called, would allow disposal of up to 44 metric tons of plutonium at WIPP, Lyman said.

Under the agreement with Russia in 2000, the United States initially undertook a two-track approach to dispose of it surplus weapons plutonium. The bulk of it was to be converted to a nuclear fuel called MOX — a mixture of oxides of plutonium and uranium — that could be burned in civilian power reactors. The rest, about 25% of the total, was considered too impure for use in MOX and, instead, was to be immobilized in glass and buried in cannisters along with highly radioactive waste (to discourage any efforts in the future to recover it).

In 2002, the Bush administration cancelled the immobilization option and decided to pursue only the MOX option at the Energy Department's Savannah River site in South Carolina. But processing the impure plutonium for MOX use added to the cost of the fuel fabrication facility under construction. At the same time, the Energy Department has been unable to find any electric utilities willing to purchase MOX fuel for use in existing or planned commercial power reactors.

Lyman, who has long opposed the construction of a large-scale plutonium processing facility because of safety and security concerns, said the escalating costs of the South Carolina plant were predictable. "Watching this unfold like a slow-motion train wreck has been a very disappointing experience for me," he said.

The Energy Department, faced with rising costs and a tough budget environment, commissioned the April study to assess the cost of finishing and operating the uncompleted MOX plant as well as the cost of other plutonium disposal options. The total cost of the MOX plant was estimated at more than $31 billion when "sunk" costs such as those related to the WIPP facility are included, with a start date of plutonium disposition in 2028. The study also looked at:

• Building specially purposed "fast" reactors for burning the MOX fuel, at an estimated total cost of at least $58 billion, with disposition to begin in 2033.
• Immobilizing all the plutonium and burying it with high-level nuclear waste, at a cost of more than $36 billion, with disposition to begin in 2039.
• Placing cannisters of plutonium in three-mile deep boreholes, with disposition to begin in 2048 (and not enough data available to allow a long-term costs estimate).
• Downblending and disposing of the plutonium, with disposition to begin in 2019 at an estimated $8.78 billion in new costs and a total of more than $16 billion if "sunk" costs are included.

The report concluded that downblending was the cheapest of the options studied and the easiest to accomplish with existing technology in a timely fashion.

Both Lyman and Pierce Corden, visiting scholar at CSTSP, noted that "downblending" is a bit of a misnomer when applied to plutonium rather than highly enriched uranium (HEU), another fissile material used in nuclear warheads. HEU typically contains at least 85% of the fissile uranium-235 isotope. To be rendered unusable in warheads, highly enriched material can be downblended with other isotopes of uranium, such as U-238, to bring its percentage of U-235 to less than 5%.

Lyman said that all isotopes of plutonium (with the exception of nearly pure Pu-238) have the potential for use in warheads, however. A plutonium warhead cannot be truly downblended. But it can be mixed with a special chemical inhibitor. The Energy Department has developed a classified substance called "stardust" that is described in one unclassified document as "a mixture of cementing, gelling, thickening and foaming agents" that make it "more difficult and complex to recover, concentrate and purify the plutonium."

Pomper and Corden said the debate over how best to dispose of surplus weapons plutonium should be set in a broader context, given that large amounts of plutonium are produced in the civilian sector (in nuclear power reactors) as well as in the defense sector.  More than 500 metric tons of the material has been reprocessed globally from spent fuel of power reactors and is kept in a separated form.

"Bear in mind that every time you turn on a reactor, you create plutonium," Corden said. An additional 70 tons of plutonium is created globally each year in the civilian sector, he said.  In the wrong hands, only about 18 pounds of the stuff could be used to make a nuclear weapon. 

Proper handling and disposition of plutonium is a challenge for many nations, not just Russia and the United States. Corden noted the parties to the Nuclear Security Summit 2014, attended by more than 50 world leaders in March at The Hague in the Netherlands, recognized that all nuclear materials must be covered by effective nuclear security systems. The communique from the summit said "that highly enriched uranium (HEU) and separated plutonium require special precautions and that it is of great importance that they are appropriately secured, consolidated and accounted for." It added, "We encourage States to minimize their stocks of HEU and to keep their stockpile of separated plutonium to the minimum level, both as consistent with national requirements."

National interests continue to complicate the worldwide handling and disposition of plutonium, however. Pomper noted long-standing differences between Russia and the United States on the uses of plutonium. The Russians see separated plutonium as a resource to be used both as a fuel in conventional reactors and as a fuel for fast reactors that can create more plutonium than they consume. They consider efforts to immobilize, dilute, and bury plutonium as akin to "flushing gold down the toilet," Pomper said. 

In 2010, the Obama administration agreed that the Russians should be allowed to burn their surplus weapons plutonium in two demonstration fast reactors, the BN-600 reactor which has been in operation since 1980 and the nearly completed BN-800. The agreement also committed the United States to turning its surplus weapons plutonium into MOX fuel rather than disposing of it through burial or other means. The agreement with the Russians would have to be modified if the United States were to undertake a downblending and disposal option.

Pomper said there is some optimism that such an accommodation could be reached. Even with the current Ukraine crisis, he said, Russia has agreed to talk about possible changes to the U.S. disposition plan. He noted that a "Megatons to Megawatts" agreement between Russia and the United States was completed in the early 1990s during the Yugoslavia crisis. Under that agreement, Russia agreed to supply the United States with low-enriched uranium (LEU), obtained from downblending of high-enriched uranium left over from the former Soviet Union's defense program. The United States agreed to purchase the low-enriched uranium fuel for use in civilian power reactors, and the last shipment of the material occurred late last year.