Treatment and Conditioning of Wastes from US Nuclear Fuels Reprocessing Plants

摘要

The US has operated nuclear fuels reprocessing plants at Hanford, Idaho Falls, and Savannah River in its defense programs and at West Valley in its commercial program. Other commercial plants have been proposed and some constructed but not operated. The liquid high-level wastes at Hanford and Savannah River have, for nearly 40 years, been conditioned for storage by adding NaOH, a process which precipitates most of the radionuclides except Cs in an insoluble sludge. Mechanical separation of this sludge coupled with decontamination of the supernate by ion exchange and/or precipitation gives a waste concentrate for immobilization. The Defense Waste Processing Facility at Savannah River is under construction to immobilize this concentrate in borosilicate glass. Idaho is just placing a new calciner in operation to treat their acid wastes directly. Techniques have also been developed to remove Cs, Sr, and noble metals from the liquid wastes for defense purposes and commercial uses. Except at West Valley, the US technique to date has been to dissolve the fuel clad rather than shear-leach it. However, because shear-leach is the expected future process, the US has also developed techniques both for immobilizing leached clad in concrete and for decontaminating it by melting. As regard to gaseous waste, the current US reprocessing plants treat their off-gas mainly to remove iodine and particulates. Idaho also has a small facility for recovery of exp 85 Kr for beneficial use. By US Environmental Protection Agency rules on the nuclear fuel cycle, it may be necessary to remove T, exp 14 C, and Kr if a large commercial reprocessing industry matures. Oak Ridge has developed a voloxidation process as a first step in such removal. Finally, the US has the decontamination, assay, sorting, incineration and burial technologies and facilities for treating the low-level liquid and solid wastes from reprocessing. (ERA citation 08:050758)