HIGH-LEVEL WASTE MANAGEMENT AT THE DEPARTMENT OF ENERGY SAVANNAH RIVER SITE

摘要

The Savannah River Site (SRS) is a Department of Energy (DOE) site located on 300-square miles in South Carolina. Since it became operational in 1951, the site has produced nuclear material for national defense, research, medical, and space programs. The separation of fissionable nuclear material from irradiated targets and fuels resulted in the generation of over 150 million gallons of radioactive waste. Originally, 51 tanks were constructed and utilized to support the mission. Six tanks have been operationally closed and taken out of service and two are currently undergoing the closure process. Most of the tank waste is a complex mixture of chemical and radioactive waste generated during the separation of special nuclear materials and enriched uranium from irradiated targets and spent fuel using the Plutonium Uranium Reduction Extraction (PUREX) process in the F-Canyon separation facility and the modified PUREX process in the H-Canyon separation facility (HM process). Waste generated from the recovery of Pu-238 in H-Canyon for the production of heat sources for space missions is also included. The waste was converted to an alkaline solution; metal oxides settled as sludge (iron, aluminum, uranium, manganese, nickel, and mercury), and supernate evaporated to form saltcake. The Liquid Waste System is a highly integrated operation involving safely storing liquid waste in underground storage tanks; removing, treating, and dispositioning the low-level waste fraction in concrete; vitrifying the higher activity waste at the Defense Waste Processing Facility (DWPF); and storing the vitrified waste in stainless steel canisters until permanent disposition. Continued long-term storage of these radioactive wastes poses a potential environmental risk. Therefore, since 1996, DOE and its contractors have been removing waste from tanks, pre-treating it, vitrifying it, and pouring the vitrified waste into canisters for long-term disposal in a permanent repository. As of December 31, 2014, DWPF had produced 3,917 vitrified waste canisters.