Plutonium Disposition by Downblending and Disposal

On June 4, AAAS hosted a breakfast panel event on “downblending and disposal” as an option for weapons-grade plutonium disposition under the Plutonium Management and Disposition Agreement (PMDA[1]). This subject has a long history that dates back to the end of the Cold War, combining complex technical, policy, and diplomatic issues. This discussion is timely because the Department of Energy (DOE) recently released a report[2] evaluating technological alternatives to the current approach of disposing of the 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 Unites States and Russia had excess weapons-grade uranium and plutonium. In order to fulfill treaty commitments while supporting the nuclear nonproliferation regime, the U.S. and Russia signed the PMDA in 2000. In this agreement, both states committed to dispose of at least 34 metric tons of excess weapons grade plutonium, primarily as MOX fuel for light water reactors (LWR). In 2010 the agreement was amended to permit Russia to consume the 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 for a “spent fuel standard” whereby the plutonium should 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.”

In order 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 with the Waste Isolation Pilot Plant (WIPP) as the reference case. WIPP is a repository for defense-related transuranic waste near Carlsbad, New Mexico. 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, this option could require 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 still under investigation, but WIPP may not reopen for years. While an alternate repository could be used in place of WIPP, the licensing process adds significant uncertainty, and it could substantially erode the cost savings for this option.

Downblending and disposition of excess plutonium is under consideration given the motivation to demonstrate progress in meeting nonproliferation objectives, delay in the U.S. MOX program, and the current fiscal environment. In light of the benefits and challenges associated with the downblending and disposition option.

The event hosted by CSTSP on June 4 brought together Dr. Edwin Lyman, Union of Concerned Scientists, and Miles Pomper, James Martin Center for Nonproliferation Studies in a session moderated by Dr. Pierce Corden, a visting scholar at CSTSP. 

The presentations from the event are available below:

Dr. Edwin Lyman, Union of Concerned Scientists 

Dr. Edwin Lyman is a Senior Scientist in the Global Security Program at the Union of Concern Scientists (UCS). His work focuses on nuclear proliferation, nuclear terrorism, nuclear safety, and nuclear security. He is a member of the Institute of Nuclear Materials Management and a co-author of the book “Fukushima: The Story of a Nuclear Disaster,” which was published in February by the New Press. He holds a doctorate degree in physics from Cornell University.

PResentation 

Miles Pomper, James Martin Center for Nonproliferation Studies 

Miles Pomper is a Senior Research Associate in the Washington DC office of the James Martin Center for Nonproliferation Studies (CNS). His work focuses on nuclear energy, nuclear nonproliferation, nuclear security, and nuclear arms control. He is also a co-chair of the Fissile Materials Working Group. He holds a master's degree in international affairs from Columbia University and a master's degree in journalism from Northwestern University.

PRESENTATION