Plutonium Disposition by “Downblending and Disposal”

By Adam Hoffman

Plutonium_ring 211x201The subject of plutonium disposition has a long history that dates back to the end of the Cold War, combining complex technical, policy, and diplomatic issues. A discussion of this history is timely because the Department of Energy recently released a report1 evaluating technological alternatives to the current approach of disposing of plutonium using mixed oxide (MOX) fuel. One option—referred to as “downblending and disposal”—was assessed favorably in terms of cost, timeliness, and technical risk, but it introduces new technical and political challenges. This blog post provides a brief summary of the storied history of plutonium disposition.

In the wake of the Cold War, the United States and Russia were left with stockpiles of excess weapons-grade uranium and plutonium. In order to fulfill treaty commitments while supporting the global nuclear nonproliferation regime, the U.S. and Russia signed the Plutonium Management and Disposition Agreement2 (PMDA) in 2000. In this agreement, both parties committed to dispose of at least 34 metric tons of excess weapons-grade plutonium, primarily as MOX fuel for light water nuclear reactors. In 2010 this agreement was amended to permit Russia to consume plutonium in fast reactors with limitations on the production of additional weapons-grade plutonium.

The MOX approach was selected based on several evaluations of plutonium disposition options, including a 1994 report by the National Academy of Sciences (NAS) titled “Management and Disposition of Excess Weapons Plutonium.” This report advocated a “spent fuel standard” whereby the plutonium would be converted “to a form from which the plutonium would be as difficult to recover for weapons use as the larger and growing quantity of plutonium in commercial spent fuel.” The report recommended two options that fulfilled this objective: the consumption of plutonium in MOX fuel and the immobilization of plutonium with high-level radioactive waste (HLW). Although the report did not explicitly consider “downblending and disposal,” it recommended against vitrification without HLW, noting that “[f]or states such as Russia or the United States, a chemical barrier alone would be insignificant.”

To convert the weapons-grade plutonium to MOX fuel, the U.S. would build a MOX Fuel Fabrication Facility (MFFF) at the DOE’s Savannah River Site. In 2002, the DOE estimated that the MFFF would cost about $1 billion, but by 2007 the cost had escalated to $4.8 billion. In 2013 the construction cost further increased to $7.8 billion, and as of 2014 the total life-cycle costs of the MOX program are estimated to be about $30 billion. In light of the current budget environment, this cost escalation prompted the DOE to evaluate alternatives for plutonium disposition.

In April 2014, the DOE released a report comparing five options for plutonium disposition including the current MOX program. Of those options, “downblending and disposal” was assessed most favorably in terms of technical risk and expense, with a life-cycle cost estimate of only $9 billion. In this option, plutonium oxide would be mixed with inhibitor materials and disposed at a geologic repository. The Waste Isolation Pilot Plant (WIPP)—a repository for defense-related transuranic waste near Carlsbad, New Mexico—served as the reference case. WIPP received its first shipment of nuclear waste in 1999, and it has already disposed of several tons of plutonium from the Rocky Flats Plant. While the waste form for this option may not meet the “spent fuel standard” endorsed by the NAS report because it lacks a radiation barrier, this could potentially be offset by achieving a geologic barrier much sooner than would be possible for spent MOX fuel or vitrified HLW.

However, the downblending option faces several significant challenges. First, it would require a supplemental agreement with Russia pursuant to Article III of the PMDA. In the past, Russia has been reluctant to accept disposition options that do not degrade the isotopic distribution of the plutonium from weapons-grade to reactor-grade, including vitrification with HLW. In addition to not altering the isotopic distribution, downblending also lacks a radiation barrier. Thus downblending would represent a significant deviation from the existing bilateral agreement, complicating negotiations with Moscow.

In addition, there are technical and policy challenges associated with using WIPP as the geologic repository. First, WIPP does not have sufficient remaining statutory capacity to accept the 34 metric tons of plutonium associated with the PMDA. As a result, using WIPP for disposition could require the amendment of existing legislation or enactment of new legislation. Further complicating this option, there was an accidental release of radioactive material from WIPP in February. This event is under investigation, and it is possible that WIPP may not reopen for years. While an alternate repository can be used in place of WIPP, the licensing process adds significant uncertainty and could substantially erode the estimated cost savings for this option.

Downblending and disposal of excess plutonium is under consideration given the motivation to demonstrate progress in meeting nonproliferation objectives, delays in the U.S. MOX program, and the current federal fiscal environment. To foster a discussion of this topic, the American Association for the Advancement of Science will host a breakfast panel event on the morning of Wednesday, June 4, in Washington, DC on “downblending and disposal” as an option for weapons-grade plutonium disposition under the PMDA (link to RSVP). In light of the benefits and challenges associated with the downblending and disposition option, we expect a lively and informative discussion and invite American Nuclear Society members to attend. In addition, ANS will host a conference on plutonium science September 7–12, 2014, in Las Vegas, NV.


1Report of the Plutonium Disposition Working Group: Analysis of Surplus Weapon-Grade Plutonium Disposition Options,” Department of Energy, April 2014.

2Formally titled the Agreement between the Government of the United States of America and the Government of the Russian Federation Concerning the Management and Disposition of Plutonium Designated as No Longer Required for Defense Purposes and Related Cooperation


adam hoffman 100x137Dr. Adam Hoffman is an intern with the Center for Science, Technology, and Security Policy at the American Association for the Advancement of Science, where he is supporting various Center initiatives and programs. In September of 2013, Adam completed a Ph.D. in Nuclear Engineering and Radiological Sciences at the University of Michigan.  After completing the internship, Adam will begin the National Nuclear Security Administration Graduate Program at the U.S. Department of Energy, working in nuclear nonproliferation.

6 Responses to Plutonium Disposition by “Downblending and Disposal”

  1. Odd that the reactor disposition options for plutonium don’t include any income from electricity generated.

    GE’s offer to build a pair of PRISM reactors for the UK without up-front capital would imply that the technical risk is not as high as portrayed in the report.

  2. Wow, you’ve managed to follow, lock step, all the talking points of the lobbyists for MOX.

    There’s nothing in the non-MOX paths that can’t be solved, some of them fairly easily. There are also many hidden costs in just getting MOX ready for feed that are still buried under the current fallen leaves/bayonetted managers.

    BTW, come back after you’ve actually WORKED on any of these alternatives and have a visceral familiarity with them. MOX is and has been a boondoggle for those of us familiar with the project, and who have washed the mud off our fenders from the actual construction site. A site which, BTW, is within 5 iron distance of at least 5 other hundred-million dollar nuclear boondoggles dedicated to gummint waste.

    Also, anyone else see the implicit hypocrisy in the bad-mouthing of WIPP and the resident outrage at closing Yucca Mountain?

  3. In support of the MOX option, it must be remembered that the Belgonucleaire Dessel (Belgium) MOX plant produced some 660 t of MOX, “absorbing” thus about 40 t of plutonium. The process developed for this plant was transfered to MELOX and served as a basis for the MFFF. Dessel plant was closed after manufaturing MOX for more than 20 years without any notable incident/accident. Closure was unavoidable due to the strongly reduced MOX fuel market …

  4. I can’t understand why the UK hasn’t taken up the PRISM IFR offer. Does anyone have any idea?

  5. Mark Self

    As a former Pantex Plant employee and resident of the Texas Panhandle I would like the DOE to get off their butts and get this plutonium from the 12,000 -20,000 + weapons that have been retired out of zone 4 at Pantex.
    This is a problem that deserves attention now before there is a huge, non-recoverable accident or the excess becomes a target for terrorism. A dispersal could mean hundreds of thousands of square miles of contaminated land. With prevailing winds out of the South, West or Southwest at 30 + mph the contamination plume could extend to Kansas City and beyond. It’s time something is done but politics will most likely prevail until there is a history making damaging incident with major loss of life and property.

  6. I find it remarkable that a substance that was created with so much expense and energy, and which embodies so much potential energy, should just be thrown away. Considering Pu’s potential value–it could be consumed in future molten salt reactors or used as startup fuel in fast reactors–can’t we just store it somewhere until Gen IV reactors are available? If we must throw it away, WIPP is the obvious solution, assuming the legal and political issues can be overcome.

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