Tank waste treatment R and D activities at Oak Ridge National Laboratory

Oak Ridge National Laboratory (ORNL) served as the pilot plant for the Hanford production facility during the 1940s. As a result, the waste contained in the ORNL storage tanks has similarities to waste found at other sites, but is typically 10 to 100 times less radioactive. It is estimated that nearly 4.9 million liters of legacy of waste is stored on the site of ORNL. Of this volume about one-fifth is transuranic sludges. The remainder of the waste volume is classified as low-level waste. The waste contains approximately 130,000 Ci, composed primarily of {sup 137}Cs, {sup 90}Sr, and small amounts of other fission products. The wastes were originally acidic in nature but were neutralized using Na{sub 2}CO{sub 3}, NaOH, or CaO to allow their storage in tanks constructed of carbon steel or concrete (Gunite). In addition to the legacy waste, about 57,000 L of concentrated waste is generated annually, which contains about 13,000 Ci, consisting primarily of {sup 137}Cs, {sup 90}Sr, and small amounts of other fission products. As part of the US department of Energy`s (DOE`s) Environmental Management Tanks Focus Area and Efficient Separations and Processing programs, a number of tasks are under way at ORNL to address the wastes currently stored in tanks across the DOE complex. This paper summarizes the efforts in three of these tasks: (1) the treatment of the tank supernatant to remove Cs, Tc, and Sr; (2) the leaching or washing of the sludges to reduce the volume of waste to be vitrified; and (3) the immobilization of the sludges