Interim Solidification of Srp Waste with Silica, Bentonite,or Phosphoric Acid.

摘要

One option for interim waste management at the Savannah River Plant is in-tank solidification of the liquid waste solutions. This would reduce the mobility of these highly radioactive solutions until techniques for their long-term immobilization and storage are developed and implemented. Interim treatments must permit eventual retrieval of waste and subsequent incorporation into a high-integrity form. This study demonstrated the solidification of simulated alkaline waste solutions by reaction with silica,bentonite,and phosphoric acid. Alkaline waste can be solidified by reaction with silica gel,silica flour,or sodium silicate solution. Solidified products containing waste salt can be retrieved by slurrying with water. Alkaline supernate (solution in equilibrium with alkaline sludge in SRP waste tanks) can be solidified by reaction with bentonite to form cancrinite powder. The solidified waste can be retrieved by slurrying with water. Alkaline supernate can be solidified by partial evaporation and reaction with phosphoric acid. Water is incorporated into hydrated complexes of trisodium phosphate. The product is soluble,but actual plant waste would not solidify completely because of decay heat. Reaction of simulated alkaline waste solutions with silica gel,silica flour,or bentonite increases the volume by a factor of approximately 6over that of evaporated waste;reaction with phosphoric acid results in a volume 1.5times that of evaporated waste. At present,the best method for in-tank solidification is by evaporation, a method that contributes no additional solids to the waste and does not compromise any waste management options. (ERA citation 01:018741)