Low Activity Waste Feed Solids Characterization and Filterability Tests

Technical Report · Sat Mar 01 04:00:00 EST 2014

DOI:https://doi.org/10.2172/1129159· OSTI ID:1129159

Crawford, Charles L. ^[1]; Duignan, Mark R. ^[1]; Williams, Michael R. ^[1]; Burket, Paul R. ^[1]; McCabe, Daniel J. ^[1]

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1. Savannah River National Laboratory (SRNL), Aiken, SC (United States)

The primary treatment of the tank waste at the DOE Hanford site will be done in the Waste Treatment and Immobilization Plant (WTP) that is currently under construction. The baseline plan for the WTP Pretreatment facility is to treat the waste, splitting it into High Level Waste (HLW) feed and Low Activity Waste (LAW) feed. Both waste streams are then separately vitrified as glass and sealed in canisters. The LAW glass will be disposed onsite in the Integrated Disposal Facility (IDF). There are currently no plans to treat the waste to remove technetium in the WTP Pretreatment facility, so its disposition path is the LAW glass. Options are being explored to immobilize the LAW portion of the tank waste, i.e., the LAW feed from the WTP Pretreatment facility. Removal of ⁹⁹Tc from the LAW Feed, followed by off-site disposal of the ⁹⁹Tc, would eliminate a key risk contributor for the IDF Performance Assessment (PA) for supplemental waste forms, and has potential to reduce treatment and disposal costs. Washington River Protection Solutions (WRPS) is developing some conceptual flow sheets for LAW treatment and disposal that could benefit from technetium removal. One of these flow-sheets will specifically examine removing ⁹⁹Tc from the LAW feed stream to supplemental immobilization. The conceptual flow sheet of the ⁹⁹Tc removal process includes a filter to remove insoluble solids prior to processing the stream in an ion exchange column, but the characteristics and behavior of the liquid and solid phases has not previously been investigated. This report contains results of testing of a simulant that represents the projected composition of the feed to the Supplemental LAW process. This feed composition is not identical to the aqueous tank waste fed to the Waste Treatment Plant because it has been processed through WTP Pretreatment facility and therefore contains internal changes and recycle streams that will be generated within the WTP process. Although a Supplemental LAW feed simulant has previously been prepared, this feed composition differs from that simulant because those tests examined only the fully soluble aqueous solution at room temperature, not the composition formed after evaporation, including the insoluble solids that precipitate after it cools. The conceptual flow sheet for Supplemental LAW immobilization has an option for removal of ⁹⁹Tc from the feed stream, if needed. Elutable ion exchange has been selected for that process. If implemented, the stream would need filtration to remove the insoluble solids prior to processing in an ion exchange column. The characteristics, chemical speciation, physical properties, and filterability of the solids are important to judge the feasibility of the concept, and to estimate the size and cost of a facility.

• Research Organization: Savannah River National Laboratory (SRNL), Aiken, SC (United States); Savannah River Site (SRS), Aiken, SC (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC09-08SR22470
• OSTI ID: 1129159
• Report Number(s): SRNL--STI-2014-00126
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
ION EXCHANGE
Ion Exchange
Low Activity Waste
PRECIPITATION
Precipitation
TECHNETIUM
Technetium