Independent Report Confirms that Downblending and Geologic Disposal is Best Option for Plutonium

December 7, 2015 | 9:37 pm
Ed Lyman
Director, Nuclear Power Safety

Today, UCS is releasing the Phase 2 report of the “Plutonium Disposition Options Independent Assessment” carried out by the Aerospace Corporation. This report, dated August 20, 2015, but only now becoming public, is the second part of a congressionally mandated independent review of the Plutonium Working Group (PWG) report that was released by the Department of Energy in 2014. The PWG was charged with reviewing the options for disposing of tens of tons of plutonium left over from the U.S. nuclear weapons program.

The Phase 1 Aerospace report, which was delivered to Congress in April of this year, analyzed two of the plutonium disposition options that had been studied by the PWG: the MOX fuel option, which is the current baseline, and the “downblend and disposal” option.

The MOX fuel option involves using the plutonium as fuel for commercial nuclear reactors. DOE is currently constructing a plant at the Savannah River Site in South Carolina that would fabricate mixed-oxide (MOX) fuel from the ex-weapons plutonium, but the estimated cost of completing the plant has skyrocketed. Moreover, this option would make the plutonium more accessible to terrorists. The downblend and disposal option entails blending down the plutonium with an inert material and disposing of the mixture in a geologic repository such as the Waste Isolation Pilot Plant (WIPP) in New Mexico. (WIPP is currently not accepting waste following an accident involving a waste drum in February 2014, but is projected to resume operation within the next several years.)

The Phase 1 report confirmed the PWG’s findings that the MOX option would be far more expensive than the downblending option and has a far higher level of programmatic risk. The Phase 1 report provided strong support for DOE’s aspiration to suspend the MOX program and pursue a cheaper and less risky alternative like downblending. However, Congress continues to fund construction of the MOX plant to the tune of roughly $350 million per year for reasons of the pork-barrel variety.

The Phase 2 report supports “downblend and disposal”

The Phase 2 report addresses the remaining options discussed in the PWG report but not included in Phase 1: irradiation of plutonium in advanced fast neutron reactors (as opposed to the MOX option, which would use current generation light-water reactors); immobilization of plutonium with high-level radioactive waste and disposal in a geologic repository (other than WIPP, which cannot accept this kind of waste); and direct disposal in deep boreholes.

The Phase 2 report takes a generally unfavorable view of these three options in comparison to downblending, citing their technical challenges. It concludes that “downblend is the least complex [alternative] in design and operations and has the lowest cost-risk.”

The report is particularly negative about the prospects of the advanced disposition fast reactor, which it considers even more technically challenging and higher in cost-risk than the current MOX program. Even though there is little prospect that DOE would seriously consider fast reactors for plutonium disposition, other countries, such as the United Kingdom, continue to study the option. Policymakers in those countries would be well advised to pay attention to the Aerospace report’s assessment.

While UCS generally agrees with the Phase 2 report, we think that it is too pessimistic about the prospects for plutonium immobilization, and that further study of potential immobilization alternatives as backup options to downblending is warranted.

The Phase 2 report provides additional insight into the reasons the MOX project has proven so difficult and gone so far off track. The report points out that the unique plant design requires equipment to be fabricated and installed within tight tolerances, necessitating highly skilled trade workers, but the contractor has had difficulty locating suppliers and subcontractors able to do the exacting work to high quality standards. This could partly explain why, as DOE testified to Congress earlier this year, the project has a “rework rate” of 25%, meaning 25% of the construction and installation work has to be torn out and redone.

The MOX project contractor, CB&I Areva, hired a firm called High Bridge to do its own critique of the downblending and disposal option. In a recent report, High Bridge asserted that disposing of the entire inventory of excess plutonium in WIPP would cause serious safety problems. However, these concerns are overblown and should be put into context. The safety, security and environmental risks of the MOX program, which would involve far more processing of plutonium in above-ground facilities, including irradiation of MOX fuel in reactors, would be far greater than any incremental risk resulting from an increase in the quantity of plutonium to be disposed of in WIPP.

Congress should stop wasting taxpayer money on the MOX boondoggle and allow DOE to pursue a course that will be less expensive and will have a far higher chance of success.

For more information about this issue, see the January 2015 UCS report:  “Excess Plutonium Disposition The Failure of MOX and the Promise of Its Alternatives