Characterization of radioactive wastes at nuclear weapons sites can reduce fissile material uncertainties necessary for deep nuclear arms reductions while serving to protect the human environment. In this regard, a preliminary estimate based on waste characterization data indicates that from 1944 to 2009 about 12.7 metric tons of plutonium was discarded at U.S. nuclear weapon production facilities. This is more than three times than the U.S. Department of Energy’s (DOE) last official estimate of waste losses (3.4 tons) made in 1996. Of the 12.7 tons, about:
- 2.7 tons in high-level radioactive wastes are stored as liquids in tanks and as granulated material in bins on the sites of former U.S. military reprocessing plants;
- 7.9 tons are in solid waste, which DOE plans to dispose at the Waste Isolation Pilot Project (WIPP) a geological repository in New Mexico for transuranic wastes. About half is already emplaced; and
- 2.1 tons are in solid and liquid wastes buried in soil prior to 1970 or held up in facilities at several DOE sites. The DOE considers most of this plutonium to be permanently disposed.
The dramatic increase from the DOE’s 1996 waste estimate appears to be due to: reclassification as waste of process residues originally set aside for plutonium recovery for weapons; underestimates of production losses; and improvements in waste characterization data.
The amounted of discarded plutonium also increases the estimate of the total amount of plutonium produced by the U.S. Government from about 0.4 to 3 tons. It’s possible that inventory at other sites may have also been reclassified as waste at other sites, which may also explain the increase. If so this would be more compatible with the plutonium production equation used by DOE. There remain uncertainties over how much plutonium was produced and disposed because of gaps in record keeping during the first 25 years of weapons production.
DOE should update its Nuclear Materials Management and Safeguards System to take into account recent radioactive waste characterization data. The Hanford site in Washington State is responsible for nearly a third of DOE’s plutonium wastes (4 tons) — more than any site in the U.S. nuclear weapons complex. Despite evidence of significant deep subsurface migration, DOE currently plans to leave about 0.7 MT of plutonium disposed before 1970 behind in the ground at the conclusion of its environmental cleanup at Hanford. DOE should, however, remove as much buried plutonium as possible at Hanford for geologic disposal, as it is doing at the Idaho National Laboratory.
Finally, WIPP is the world’s first operating deep geological disposal site for waste that includes significant quantities of weapon-usable material. DOE requires the plutonium-239 content of each waste container to be measured. WIPP therefore could be brought under IAEA monitoring prior to its closure, currently planned for 2030. This would be seen internationally as an indication of strengthened U.S. commitment to nuclear disarmament and the Nuclear Non-Proliferation Treaty.