Russian Federation (RF) and United States (US) collaborations from July 1998 through July 2001 conducted investigations of the Pu-bearing sludges in storage at the Mining Chemical Combine (MCC) K-26 site in order to dispose of weapons-grade plutonium and decommission the radiochemical plant. This RF work resulted in the recovery of approximately 20 kg of weapons-grade plutonium (and (approx)19 MT of uranium) from the sludges which was stored as oxide. Another method investigated and partially developed as joint collaborative efforts during this time period was direct immobilization of plutonium with no recovery of plutonium. This method melts the untreated recovered sludges by microwave ultrahigh frequency (UHF) heating with glass formers. After cooling, melter-crucibles of vitrified sludge are stored on site in underground cavities for eventual disposal in a geologic repository. Cost and technical feasibility studies of the two methods show that direct immobilization (i.e., vitrification) of the plutonium-containing sludge is the preferred alternative. It is also preferred from the ecological point of view. However, RF funding alone is insufficient to continue this work, and US funding has been suspended. It appears unlikely that development of full scale vitrification technologies for the plutonium-bearing sludges can be undertaken without continuing support from the US or from others. Thus, the only demonstrated technology for the MCC for removing weapons-grade plutonium in sludges will remain recovery and extraction of plutonium for storage and reuse for the indefinite future. It is estimated the about 1200 to 1800 kg of weapons plutonium are in the sludges that must be removed an d treated as part of the MCC facility decommissioning. This specific plutonium is not covered under any current monitoring or treaty agreement between the RF and the US.
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