Dangerous Waste Characteristics of Waste from Hanford Tank 241-S-109

Abstract

Existing analytical data on samples taken from Hanford Tank 241-S-109 (S-109), along with process knowledge of the wastes transferred to this tank, were reviewed to determine whether the dangerous waste characteristics currently assigned to all wastes in Hanford underground storage tanks are applicable to S-109 waste. Supplemental technologies are being examined to accelerate the Hanford tank waste cleanup mission and to accomplish waste treatment in a safer and more efficient way. The Bulk Vitrification System (BVS) is one treatment technology being considered to assist in immobilizing the low-activity tank waste. The goals of the supplemental technologies are to reduce costs, conserve double-shell tank space, and meet the scheduled tank waste processing completion date of 2028. The effectiveness of the bulk vitrification process will be demonstrated at a research and development facility known as the Demonstration Bulk Vitrification System (DBVS). The DBVS will test technologies using dissolved saltcake waste from Tank S-109. The dangerous waste characteristics being considered (and the dangerous waste codes) include ignitability (D001), corrosivity (D002), and reactivity (D003). The analytical data reviewed with respect to waste code D001 include differential scanning calorimetry (DSC) results and the percent of the lower flammability limit (LFL) calculated from the composition of the headspace. Concentrations of sulfur, sulfate, and cyanide, the composition of headspace (vapor space), and DSC results were reviewed for waste code D003; and pH was reviewed for D002. Data on mercury concentrations were also included. DSC results were used to determine the energetics of the tank wastes as a function of temperature. Exothermic transitions were observed in a limited number of samples from Tank S-109. Exothermic transitions were broad peaks with small amplitudes at temperatures exceeding 200ºC, indicating that explosive reactions or ignition hazards at standard temperatures and pressures are unlikely (waste codes D001 and D003). Sulfur and sulfate analyses indicated that the majority of the sulfur in the waste is present as sulfate. Based on the pH of the tank wastes, the sulfate is stable and will not react to form sulfide. Thus, this waste should not be considered sulfide-bearing (waste code D003). Cyanide analyses were not available, but process history indicates that no cyanide-containing process or waste streams were transferred to this tank. Thus, this waste should not be considered cyanide-bearing (waste code D003). The pH of the waste in Tank S-109 is 13, which exceeds the 12.5 limit considered characteristic of corrosive wastes; therefore, this waste must be considered corrosive (waste code D002). Gas analysis of the headspace vapors in this tank indicates that all of the toxic vapors except ammonia are well below the threshold limit value-time weighted average (TLV-TWA) (waste code D003). The dilution required (a factor of 1.9) is less than that currently planned for retrieval of this waste (3.37 to 1 wate...

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