Waste from Hanford underground storage tank 241-AN-107 is a candidate low-activity waste (LAW) for Envelope C. Envelope C wastes require pretreatment to remove radioactive Sr and TRU (along with cesium and technetium) before immobilization. The baseline pretreatment process planned for Sr/TRU removal was precipitation with added strontium and iron. However, studies have shown that the Sr/Fe precipitates were very difficult to filter. An alternative treatment being evaluated uses permanganate instead of iron. Permanganate treatment has been shown to be effective for decontaminating waste from Hanford Tank SY-101.Battelle conducted small-scale experiments with archived AN-107 waste over a period of about three months to determine the effectiveness of the permanganate treatment process. These tests showed that permanganate treatment alone would provide adequate TRU removal, however, permanganate alone would not provide adequate Sr removal. The preferred Sr/TRU removal process involved addition of strontium and permanganate. Test conditions that provided adequate Sr/TRU decontamination were identified. These test conditions were fimther evaluated with a 1-L batch of archived AN-107, which provided a large enough volume of waste to conduct crossflow filtration studies. These tests showed that Sr/TRU removal could be accomplished by addition of a strontium solution followed by permanganate solution. The resulting precipitate could be removed effectively by crossflow filtration.The original target sodium concentration for AN-107 diluted feed was 7.7M. The waste was fi,u-ther diluted and additional caustic added before Sr/TRU precipitation. The target concentrations for the treated waste were 6.OM sodium, 1.OMfree hydroxide, 0.075M strontium, and 0.05M permanganate. Approximately 1.4-L of AN-107 diluted feed were treated. Decontamination of strontium-90 and TRU (Am-241) in the supematant was greater than needed to meet the immobilized low-activity waste (ILAW) requirements (less than 100 nCi/g TRU and less than 20 Ci/m3 Sr-90 in the final ILAW). The stronium-90 decontamination factor (DF) was consistently greater than 50 and the Am-241 DF greater than 25. The target DFs were 10 for Sr-90 and 5 for Am-241. These DFs include the contribution from the removal of the entrained solids although this was relatively small. The removal of the entrained solids accounted for about 8V0of the DF for Sr-90 and about 17°/0of the DF for the alpha emitters.Crossflow filtration tests with archived AN-107 showed that the entrained solids could not be readily removed from AN-107 waste prior to Sr/TRU treatment, However, the filterability, as determined by filter flux rate, increased by an order of magnitude after the treatment process. For AN-107 diluted feed, crossflow filtration tests were conducted in the Cell Unit Filter (CUF) system with the Sr/TRU precipitated waste only. Results showed that the treated waste could be effectively filtered by crossflow filtration. A parametric study was conducted with relatively low, 1.9 wt'?/0, initia...

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Waste from Hanford underground storageTank 241-AN-107 is a candidatelow-activity waste (LAW) for Envelope C. Envelope C wastesrequirepretreatmentto remove entrainedsolids, radioactivestrontium, transuranics, radioactivecesium,andtechnetiumbefore immobilization. The initial baseline pretreatment pr~cess includes plans for entrained solids removal by crossflow filtration, Sr/TRU precipitation with added strontium and iron, and Sr/TRU precipitateremoval by crossflow filtration. However, studieshaveshown thatentrainedsolids and the Sr/Fe precipitateswere very difficult to filter from candidate Envelope C waste. An alternativepretreatment process being developed uses permanganateinstead of iron. Permanganatetreatment has been shown to be effective for decontaminating waste from Hanford Tank SY-101. Small-scaleexperiments with archivedAN-lo7 wastewere conducted by Battelleto determine the effectivenessof the permanganatetreatmentprocess. These testswere conducted in three rounds of experiments. The early tests showed that permanganatetreatment alone would provide adequate TRU removal, however, it would not provide adequate Sr removal. The second set of experiments showed the preferredSr/T&U removal process involved addition of strontium and permanganate. Becausethe composition of the archivedwastehad been altered by past pretreatment tests (diluted and removal of cesium and settled solids), the final set of experiments included testswith actualAN-107 diluted feed. These testsidentified conditions that should provide"adequateSr/TRU decontamination.. .. 111 Am-241) in the supernatantwas greaterthanneededto meetthe immobilized low-activitywaste (ILAW) requirements (lessthan 100 nCi/g TRU and less than 20 Ci/m' Sr-90 in the final ILAW). The targetDFs were 10for Sr-90and 5 for Am-241. The stronium-90decontamination q factors (DFs) obtained were consistently greaterthan 20 and the Am-241 DF was 10 and greater. Removal of Eu isotopes 154 and 155 was slightly less than the Am DFs. These DFs include the contribution from the removal of the entrainedsolids althoughthis was relatively small. The removal of the entrainedsolids accounted for very little Sr-90removal and about 10°/0of the DF for Am-241 becausethe archived waste sampleshad most of the solids already removed.

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