Plutonium Disposal Difficulties

Back in the 1990s, when the United States and Russia were both drawing down their numbers of nuclear weapons, Presidents Bill Clinton and Boris Yeltsin agreed, in a burst of mutual good will, to make 34 tons each of plutonium from those weapons unusable for that purpose. I was among those working hard on how to do that: the ARIES Project at Los Alamos was designing a plant for plutonium weapons pits in, canned plutonium out, with facilities for IAEA inspections.

Making the agreement work has proved difficult and is currently the subject of accusations from Russia’s President Vladimir Putin that the United States is not living up to its obligations. The good will has turned sour.

The Plutonium Management and Disposal Agreement (PMDA), signed by Clinton and Putin in 2000, is the legal basis for both operations and recriminations. Russia has changed its mind twice, once having to do with liability as nuclear safeguards collaboration was affected by shifts within the Russian government, and the other being a move from light-water MOX fuel to fuel for experimental fast reactors. The agreement was modified in 2010 to accommodate those changes. The United States is now in the process of changing its preferred option from MOX fuel to, um, something else, not quite defined.

The program in the United States has been a poster case for narrow interests competing with each other with little consideration of the larger picture. For nonproliferation interests and better relations with Russia, the best course of action would have been a direct route to plutonium disposal by the Spent Fuel Standard, which means that the plutonium would be as unusable as if it were contained in highly radioactive spent nuclear reactor fuel. To reach that standard, the plutonium might be fabricated into reactor fuel and used to produce power, with the spent fuel stored at the end of that process; or mixing the plutonium with fission products from a reactor and glassifying the mixture, to be disposed of in deep boreholes.

Russia has long wanted to use its plutonium for electrical power production, so their choice was easy. However, along the way, their plan switched from light-water reactors to fast reactors, which can be used as breeders, which can produce a lot more plutonium. That was the subject of the 2010 modification to the agreement.

 

Problems in the US Program

In the United States, the glassification and deep burial option was dropped in favor of producing MOX fuel. A plant was built in South Carolina to fabricate that fuel. That plant is now behind schedule and over budget. About $4.5 billion has been spent on it; completion may require $10 billion or more, and it is not clear that a market exists for MOX fuel.

The reasons for the cost and schedule overruns are not clear. My suspicion is that they derive from low-balling initial contract bids and mismanagement by the Department of Energy, along with uncertainties introduced by stop-and-go funding by Congress.

In terms of the agreement with Russia, the stop and go and change undermine trust. That is Putin’s gripe. He may or may not be sincere, but he has a point. The senators from South Carolina, where the plant is being built, have referred to his remarks as part of their argument for continuing to fund the plant. A large part of senatorial interest is maintaining jobs in their state.

Organizations opposing nuclear energy have been seeking to stop the MOX plant, and they use the budget overruns to argue against it. However, some of those organizations also promote nonproliferation goals. Glassification has been going badly at the Hanford Site, so a new alternative must be found.

 

The Red Team Report

A Red Team was convened to consider the options and found the preferred option to be conversion of pits to oxide, after which

The plutonium oxide would be diluted with an adulterant mixture that serves to reduce the attractiveness level of the plutonium oxide by yielding a mixture that: 1) has a reduced plutonium concentration; and 2) requires extensive processing to achieve a purified material.

It is not clear what the adulterants would be. The report mentions “inert material,” presumably inert with respect to fission. A chemically inert material could easily be separated from the plutonium.

The Red Team further recommends that the diluted material be disposed of in WIPP. WIPP has been closed since a radiological accident in February 2014. It is expected to open later this year. WIPP was never intended for storage of this type of material, and its permits would have to be revised. Questions of capacity and requirements for criticality control have been raised. Taking this option will result in more delay. It is one thing to work out this solution conceptually, as the Red Team report does, and another to work up the procedures and the safety calculations required to do the work and justify the permit changes.

Edwin Lyman and Frank von Hippel propose diluting the pit plutonium with reactor-grade plutonium from Britain or Japan. It is not clear whether this is intended to be the Red Team’s inert material or an alternative proposal.

The Spent Fuel Standard for making the plutonium unusable has been greatly modified, as described in the Red Team Report, which regards disposal in WIPP as an equivalent. Changing the isotopic composition of plutonium from nearly pure plutonium-239 to a composition including several of the other plutonium isotopes makes it less favorable for use in a bomb, but that use remains possible, with larger masses of plutonium and skillful design. Both Russia and the United States are capable of designing such weapons, but they also have sufficient stocks of weapons-grade plutonium that altering the isotopic composition takes the plutonium out of probable use in nuclear weapons. The altered plutonium will merely be undesirable. Locking it away in WIPP, the Red Team argues, is the equivalent of locking it up in highly radioactive glass.

The Red Team report contains conclusions with little information on how they were reached. It is difficult to compare the MOX option, components of which are being implemented, with the preferred dilution and disposal option more hypothetical. Indeed, the report identifies areas where facilities will likely have to be upgraded for that option. There are many steps where problems could occur. Reading between the lines of the report, a large part of the MOX plant’s problem has been inadequate funding by Congress. As long as Congress cannot pass a budget, a situation likely to persist, any option will have cost and schedule problems.

 

For the United States to change from MOX to another option will require renegotiating the PMDA with Russia; renegotiation is probably necessary because deadlines will not be met. With tensions high between the two countries, this is not a good time for renegotiation.

Having been energized and hopeful as a part of eliminating these 68 tons of plutonium from weapons use back in the 1990s, I can only feel disappointed at today’s predicament. Much effort and not nearly enough thought by all the parties involved has taken us to this point. The agreement now may be doing more harm in creating friction between the United States and Russia than good in removing the plutonium from potential use. Good job, all.

 

Photo: Technicians inspect a MOX fuel element.

2 comments

  1. Edwin Lyman · April 23

    Dear Cheryl,

    This is Ed Lyman here. Just to clarify, Frank von Hippel and I are certainly not suggesting that plutonium isotopic dilution be used as a substitute for the baseline “dilute and dispose” method. Our suggestion is that it be used as a supplemental measure should the Russians continue to complain about the fact that “dilute and dispose” does not move the isotopics of the plutonium away from weapons-grade.

    Dilution and disposal entails blending plutonium oxide with a diluent and packing small quantities (300 g Pu) into disposal drums for emplacement in WIPP (or a second repository with similar characteristics). The purpose of the diluent, the composition of which is classified, is to increase the difficulty of chemical purification of the plutonium. The combination of small quantities of plutonium per item, relatively low plutonium concentration in the mixture, deep geologic disposal, and international monitoring provides a level of confidence that the material is inaccessible, and acquisition of a sufficient quantity for a weapon would be complex and detectable.

    Changing the isotopics, as I hope the post that Frank and I wrote makes clear, does not add any significant benefit from a technical perspective. Simply changing the isotopics does not affect the weapon-usability of the plutonium by either the U.S. or Russia. The sole purpose of doing so would be to remove one objection that the Russians have raised to the U.S. proposal to change its plutonium disposition method to direct disposal instead of irradiation as MOX fuel.

    I hope this is helpful.

    Best regards,

    Ed Lyman
    Union of Concerned Scientists
    Washington, DC

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  2. Cheryl Rofer · April 24

    Thanks for the clarification, Ed.

    It’s not surprising that the composition of the chemical diluent is classified, but a person with some knowledge of plutonium chemistry can probably make a reasonable guess.

    Packing in 300-g-Pu quantities will make it more difficult, but that will also take up quite a bit of space in WIPP, which is somewhat limited. There will need to be something like 112,000 containers. If they are the size of the 3013 cans that my team developed, ten might fit in a 55-gallon-drum-sized overpack, which means 11,200 of those. The number and configuration would depend on criticality considerations.

    Developing an additional repository would take at least as much time as completing the MOX plant.

    I agree that something on that order would be more or less equivalent to the spent fuel standard in difficulty of recovery.

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