Treatability study for the stabilization of chromium contaminated waste
A process has been developed which immobilizes chromium in calcined uranyl nitrate mixed waste, resulting in a waste form disposable as radioactive, non hazardous waste. A prime contractor at the Idaho National Engineering Laboratory generates a radioactive waste contaminated with chromium. During handling, the waste becomes contaminated at a concentration sufficiently high to cause the waste to exceed the EPA`s Toxicity Characteristic Leaching Procedure (TCLP) leachable limit for chromium. A treatability test program was instigated to define the optimum conditions for the chemical reduction pretreatment step necessary for the stabilization of the contaminated waste. Sodium dithionite was determined to be the reducing agent of choice. A dithionite demand experiment was run to determine optimum dithionite dose. This dose, plus 67 percent excess, was added to each sample. Four different stabilization systems, at three different dosage levels, were investigated. The best performing reagent system was chosen for scale-up and more stringent performance testing. In one of the tested reagent systems, Portland cement sodium silicate and dithionite, all of the samples exhibited TCLP extract concentrations for chromium well below the regulatory limit. Portland cement/blast furnace slag blend had one passing sample, and for cement/fly ash and cement alone none of the samples had passing values for leachable chromium. The samples scaled-up passed the performance criteria and the process which is currently undergoing implementation at INEL has successfully converted mixed waste into radioactive waste for disposal.
- Research Organization:
- Arizona Univ., Tucson, AZ (United States). Coll. of Engineering and Mines; New Mexico State Univ., University Park, NM (United States); Waste-Management Education and Research Consortium (WERC), Las Cruces, NM (United States); USDOE, Washington, DC (United States)
- OSTI ID:
- 121114
- Report Number(s):
- CONF-940225--Vol.2
- Country of Publication:
- United States
- Language:
- English
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