Surplus Plutonium Disposition: NNSA's Long-Term Plutonium Oxide Production Plans Are Uncertain, Report to the Committee on Armed Services, U.S. Senate [open pdf - 2MB]
From the Highlights: "The United States has 57.2 MT [metric tons] of weapons-usable plutonium that it has declared surplus and that still requires disposition. This plutonium exists in various metal and non-metal forms, including pits--the central core of a nuclear weapon. To prevent insidious use of this plutonium, DOE [Department of Energy] plans to disassemble pits into metal; convert the plutonium metal to plutonium oxide, a powder-like substance; dilute it with inert material; and dispose of it at WIPP [Waste Isolation Pilot Plant]. [...] GAO [Government Accountability Office] was asked to review DOE's plans for plutonium oxide production to dispose of surplus plutonium. This report (1) examines the amount of surplus plutonium in DOE's inventory that could be converted to plutonium oxide for dilution and disposal and (2) examines DOE's capacity to produce plutonium oxide."
Government Accountability Office: https://www.gao.gov/