Demonstration of Entrained Solids and Sr/TRU Removal Processes with Archived AN-107 Waste

Abstract

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.

Status Assessment of Readiness to Deploy Permanganate Treatment for Removal of Strontium and Actinides from Savannah River Site High Level Waste

“…Numerous studies continue to complete development of this process technology for the Hanford program. 4,5,6 The process requirements for treatment of the Savannah River Site waste differ from those at Hanford, most notably with the lower allowed concentrations for soluble strontium and alpha emitting radionuclides in the treated waste at Savannah River Site. 7 Further, current plans include treatment of most of the stored liquid and saltcake waste at Savannah River Site to remove actinides and strontium.…”

Ion Exchange Studies for Removal of Sulfate from Hanford Tank Waste Envelope C (241-AN-107) Using SuperLig 655 Resin

“…Following Cs removal, the free hydroxide measured 0.126 M. The cesium-decontaminated samples were transfemed to the Radiochemical Processing Laboratory (RPL) and were archived in the Shielded Analytical Laborato~(SAL). A 1-L aliquot of this archived material was processed for Sr/TRU removal using 1 M Sr(NOJz and 1 M NaMnOq solutions (Hallen et al, 2000). After decontamination, the archive AN-107 could be contact-handled in a tie hood.…”