(697f) Hanford West Area Tank Treatment Solids Assessment

Approximately 55 million gallons of radioactive and hazardous waste are stored in underground storage tanks at the U.S. Department of Energy’s (DOE’s) Hanford Site in southeastern Washington State. The Hanford Waste Treatment and Immobilization Plant (WTP) is being constructed to immobilize the waste in glass waste forms. In an effort to expedite and remediate waste beyond the use of the WTP, the Hanford tank waste treatment mission will include a realistic and achievable course for 200 West Area for grouting the low-activity portion of the waste for offsite disposal. The approach is the West Area Tank Treatment (WATT) mission. The WATT mission is currently preparing the 200 West Area to support tank waste retrieval, pretreatment, and subsequent offsite shipment of liquid or solid treated waste for out-of-state disposal as a cementitious solidified/immobilized waste form. However, in the process or retrieving waste, solids will accumulate in WATT receiver tanks (which also receive the liquids that are the feed for pretreatment). The gradual accumulation of these solids has the potential to limit throughput of liquids for pretreatment and presents feed management challenges. Very little relevant data exists for the physical property behaviors of the insoluble 200 West Area sludge that will be retrieved. The ability to settle these solids to create clarified liquids is an important part of the pretreatment process. To address these data gaps, solids dissolution, settling tests, viscosity and shear strength measurements were determined on two West Area tank waste sludge samples from single-shell tanks (SSTs) 241-S-106 and 241-SX-102. Sludge solids and resulting wash water concentrations were characterized to determine settling rates, settled density, solids composition, and dissolution characteristics. This presentation details the results of these actual waste tests to determine the behavior of sludge in the 200 West Area of the Hanford site. Data and results from this work will be used to help support the development of waste management strategies for retrieval of waste from 200 West Area SSTs as well as provide technical guidance and potential remedies for addressing problematic behavior during flowsheet planning.