Currently, the United States has more than 60 metric tons (MT) of weapons-grade surplus plutonium. Rather than use the surplus for weapons, the United States is developing long-term plans for its safe and secure disposition.
For the past two decades, the Department of Energy’s National Nuclear Security Administration (DOE-NNSA) has moved forward with a plan to use the surplus plutonium to make MOX (mixed oxide) fuel, which would be used to generate electricity by nuclear power plants. Once used to generate electricity, the MOX fuel becomes highly radioactive and the plutonium can no longer be easily recovered and reused to make nuclear weapons. In a historic move toward nuclear non-proliferation, Russia and the United States signed an agreement to use at least 34 MT of their respective declared surplus plutonium inventories to make MOX fuel for use in power reactors. But after the U.S. program to develop MOX fuel ran far over-budget and over-schedule, the DOE-NNSA decided to explore an alternative “dilute and dispose” plan.
The DOE-NNSA plans to dilute more than half of the U.S. surplus plutonium and place it in an underground nuclear waste repository in New Mexico called the Waste Isolation Pilot Plant (WIPP). Construction of the WIPP began more than three decades ago to serve as a place for disposing of contaminated clothing and equipment from the nuclear weapons making process and early exploration of nuclear energy – known as defense transuranic waste. Putting this much concentrated plutonium waste in the WIPP is not what the citizens of New Mexico or their governor agreed to when the facility was built. Also, diluted surplus plutonium emplaced underground can be recovered and used to make nuclear weapons. While less expensive than operating the MOX Plant, the dilute and dispose plan will take 30 years and cost at least $18 billion.
Surplus plutonium is stored in multiple U.S. locations. The majority is in the Pantex Facility near Amarillo, Texas.
The plutonium is transported to Los Alamos National Laboratory in New Mexico where it is oxidized.
The oxidized plutonium is transported to the Savannah River Site in South Carolina where it is diluted to meet WIPP’s acceptance criteria.
The diluted plutonium oxide is transported in specialized packages via trucks to the WIPP near Carlsbad, New Mexico. View Image. It is then unloaded and emplaced underground.
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The amount of waste that can be emplaced in WIPP is limited both by the physical space currently available in the facility and by the Land Withdrawal Act, which caps the total amount of waste that can be in the WIPP at 175,564 cubic meters.
The addition of the diluted surplus plutonium in question would require building additional underground storage wings. A recent decision to change how waste volume is measured may help DOE to stay within the limits of the Land Withdrawal Act.
Before this change, the DOE measured the outer volume of all waste containers. After a permit modification was approved by New Mexico officials, the DOE now reports volume by inner containers – in instances where one is present. For instance, rather than counting the volume of the 55-gallon drum waste container (0.21 cubic meters), the DOE now reports only the volume of the pipe within the drum that contains the diluted plutonium (0.013 cubic meters) – a reduction of a factor of ~15. This is why there is a large size reduction in the red striped boxes in the figure. Our experts recommend that DOE reserve space in WIPP for the diluted surplus plutonium waste, since these graphs show that WIPP is likely to reach its maximum capacity even with the recalculation of volumes.
The WIPP became operations in 1999 and was originally planned to close in 2034. The final shipment for the new dilute and dispose plan is scheduled for 2049; but according to an independent evaluation from the Army Corps of Engineers, the end date is more likely to be 2056 at the earliest.
In total, the diluted surplus plutonium will take up approximately 160,660 waste containers (55 gallon drums) – more than has been emplaced in WIPP since 1999. Each shipment to WIPP carries up to 42 of these containers. For this new plan to work, 3,825 shipments from SRS – about four per week – would need to be made to the WIPP, more than double the current shipment rate.
The extended timeframe also affects the South Carolina facility in which the dilution and packaging takes place. The facility is currently 65 years old and in “poor condition,” according to the DOE. Assuming an on-time completion in 2049, the facility will be close to a century old.
By virtually any measure, the dilute and dispose plan substantially changes the physical, radiological, and chemical composition of emplaced wastes at the WIPP as well as the “social contract” for WIPP and the State of New Mexico. No previous waste stream headed to the WIPP has affected the facility’s technical measures at this high of a level. While the initial analyses indicate that the WIPP repository will maintain regulatory compliance with the increased amount of plutonium in its inventory, such a substantive change raises technical, social, and political questions that, if unaddressed, could translate to system vulnerabilities.
DOE-NNSA’s early-stage dilute and dispose plans are technically viable and cheaper than the mixed oxide (MOX) fuel plan, provided that current implementation challenges and system vulnerabilities are resolved. Our committee made several recommendations that can be implemented by the DOE and policymakers and demanded by citizens from their government.
*Security details are still under development and not available for review.