Thinking outside the MOX: A closer look at disposal alternatives

A Carlsbad, N.M., plant where employees suffered radiation exposure made headlines again last week as a possible landing spot for down-blended plutonium from the Savannah River Site – one of several alternatives to the current MOX program.

But the plant, the Waste Isolation Pilot Plant, or WIPP, is still shut down from the February 2014 incident, leaving some officials questioning its viability in serving as a disposal site.

Last week, the public finally received Part 1 of a highly anticipated study comparing two methods of ridding the nation of 34 metric tons of weapons-grade plutonium – a task that is part of an international agreement with Russia.

It compared MOX, a program that includes the Mixed Oxide Fuel Fabrication Facility under construction at SRS, and another method known as down-blending.

Conducted by Aerospace Corp. – a California nonprofit corporation that operates a federally funded research and development center – the study prices the MOX lifecycle cost at $51 billion and the down-blending method at $17 billion.

The MOX project currently is about 65 percent complete and includes the construction of multiple facilities at SRS and other DOE facilities that would convert the plutonium into commercial nuclear fuel.

Aerospace concluded that the $51 billion MOX price tag is based on whether it was to be funded at $500 million per year, closer to the level the Department of Energy has said it would take to make significant progress. If MOX was funded at $375 million per year – $30 million less than its current funding – Aerospace reported it would cost about $110 billion to complete.

Congressional supporters of MOX, including CB&I Project Services group – one of the companies building the MOX facility – have spoken out against the study, stating that the figure is inaccurate.

Specifically, federal legislators Sens. Tim Scott and Lindsey Graham and Rep. Joe Wilson – all Republicans – addressed the study in a combined statement last month.

“Having already spent $4.4 billion on the project to achieve roughly 65 percent completion, we find it difficult to understand how completing and operating the project will cost another $47.5 billion,” they wrote.

A closer look at down-blending

The down-blending method, which would also take place at SRS, would be executed using inhibitor materials, or materials that slow down the chemical process.

The solution would then be packaged into approved canisters and shipped to a repository for permanent disposal.

According to the study and other DOE-funded studies, to down-blend the plutonium, material would be added to plutonium oxide to prevent the plutonium from combining again into its original pure form. The process would reduce the plutonium content to less than 10 percent by weight, the study concludes.

The containers of down-blended plutonium would be characterized to ensure that they meet waste acceptance criteria before shipment to WIPP.

Once shipped, the containers holding the down-blended plutonium would be placed in a salt bed at WIPP. Over time, high pressure on the salt formation would cause the salt to creep, filling in the voids in the disposal rooms, and entombing the packages permanently.

According to an April 2014 DOE report, the same report that priced the MOX program at $30 billion, down-blending already has been used several times in the U.S. to dispose of about 5 metric tons of weapons-grade plutonium.

The sites which those down-blending processes occurred include the Savannah River Site, Rocky Flats in Colorado, the Hanford Site in Washington, the Idaho National Lab, Lawrence Livermore National Lab in California and the Los Alamos National Lab in New Mexico.

“This disposal method has been proven and continues to be used to dispose of surplus plutonium from various DOE sites,” officials wrote in the report.

Disposal at WIPP

According to the Aerospace study, the most likely disposal site would be the Waste Isolation Pilot Plant, which is closed due to the radiation exposure incident.

Two isolated events took place at the plant, according to DOE. On Feb. 5, 2014 a salt haul truck caught fire. Workers were evacuated, and the underground portion of WIPP was shut down. Six workers were treated for smoke inhalation.

Nine days later, late in the evening of Feb. 14, 2014, a second, unrelated event occurred when a continuous air monitor alarmed during the night shift. Only 11 employees were at the WIPP site on the surface, and no employees were underground.

Two other WIPP employees reported to the site a couple of hours later. The air monitor measured airborne radioactivity close to the operating location where waste was being stored, and ventilation air was pulled from the underground repository by huge fans on the surface. This exhaust consisted of unfiltered air, and ultimately caused the exposure incident.

Since then, the plant has been shut down until further notice and as of last month, officials said it is still too early to say when the plant will reopen.

The looming uncertainty is worrisome to MOX supporters and opposers, including SRS Watch – an independent group that monitors activities at SRS.

SRS Watch Director Tom Clements said WIPP’s initial purpose of storing transuranic waste, solid waste consisting of clothing, tools, rags, residues, debris and other items contaminated with plutonium, may cause space issues.

“I’m afraid there may not be capacity at WIPP (to house the waste),” Clements said. “But I can be supportive of the down-blending option as long as it meets the proper regulations and laws.”

Ed Lyman, a senior scientist with the Union of Concerned Scientists, also expressed concern with the down-blending approach, stating there is still more analysis to do to evaluate the security and safety of the method.

“The safety of the material used to down-blend, which has a classified composition, needs to be demonstrated to the satisfaction of the state of New Mexico,” Lyman said. “But these issues are minor in comparison to the safety and security problems of the MOX approach.”

Looking ahead

Part 2 of the MOX alternative study is scheduled for a September release. The study will review three other plutonium disposition options.

One option, the use of fast reactors, is currently being used by Russia in to hold up its end of the nonproliferation agreement.

In that process, plutonium-based nuclear weapons would be broken down into plutonium metal and used to charge a casting furnace. The plutonium would then be blended with uranium and zirconium in the fast reactor, creating a metal fuel out of the weapons-grade material. The method last year was projected to have a $50 billion lifecycle cost.

Another option is immobilization, and would include the construction of a “can-in canister” facility. Plutonium would be immobilized into either a ceramic or glass form, placed in a can and surrounded with high-level waste glass, or HLW glass, in a glass waste canister, which is why it is phrased, “can-in canister.”

Officials highlighted uncertainties with the method, but priced it last year at about $29 billion.

The final method is the use of a deep borehole and would consist of drilling boreholes into crystalline basement rock. Holes would run to 5,000 meters deep. Canisters would be placed into the lower 2,000 meters of the borehole, and the upper borehole would be sealed with compacted clay or cement.

Cost projections for the borehole method were not included in the study.