Thermal Conductivity and Shear Strength of K Basin Sludge

Abstract

To provide input for the design and modeling of sludge storage systems, Pacific Northwest National Laboratory, under contract to the Fluor Hanford Spent Nuclear Fuel (SNF) Project, performed thermal conductivity and shear strength measurements on representative sludge samples from the Hanford K East (KE) Basin: floor sludge, canister sludge, and a composite of floor and canister sludge plus spent fuel fragments. This work was performed in the High Level Radiochemistry Facility (hot cells) located in the Radiochemical Processing Laboratory in the Hanford 300 Area. K Basin sludge contains metallic uranium and uranium oxides that will corrode, hydrate, and, consequently, generate heat and hydrogen gas during storage. Heat is generated within the sludge by radiolytic decay and the reaction of uranium metal with water. For maintaining thermal stability, the sludge must be retrieved, staged, transported, and stored in systems designed to provide a rate of heat removal that prevents the temperature from increasing beyond acceptable limits. To support dispositioning the sludge to T Plant, modeling and experimental testing and analyses are being performed to predict the behavior of the material when placed into the storage containers. Two physical properties of the sludge that are critical to the modeling and testing/analyses efforts are thermal conductivity and sludge shear strength (yield stress).The thermal conductivity for a material is defined as the ratio of steady-state heat flow by conduction across a surface (heat transfer per unit area per unit time) to the temperature gradient at the surface. The thermal conductivity of the K Basin sludge must be known in order to accurately predict the rate of heat removal and the temperature of the sludge within a storage container. KC-2/3 M250 Canister sludge (minus 250-µm fraction) 0.81 (±0.06) 2.15 0.88 96-13 Canister sludge collected in 1996 -Reconstituted (a) 0.68 (±0.04) 2.67 0.64 KE Basin Floor + Canister Sludge + Fuel Fragments SNF + Sludge Composite By volume, ~64% floor sludge, ~26% canister sludge, ~7% fuel corrosion product (e.g., U 4 O 9 ), and ~3% uranium fuel fragments 0.70 (±0.03) 2.32 0.72 (a) Reconstituted -sludge sample dried out and was reconstituted to a settled sludge state through the addition of K Basin water and aggressive mixing.

An Approach to Understanding Cohesive Slurry Settling, Mobilization, and Hydrogen Gas Retention in Pulsed Jet Mixed Vessels

“…The original T-204 core sample without any dilution was 31.5 wt% total solids and had a shear strength of 1520 Pa . Poloski et al (2003) reported the second measurement on a pretreated AZ-101 waste sample. The initial sample had 10.3 wt% UDS, and the settled layer had 22 wt% UDS.…”

Development of K-Basin High-Strength Homogeneous Sludge Simulants and Correlations Between Unconfined Compressive Strength and Shear Strength

“…Most measurements given in Poloski et al (2002) were obtained from sludge samples that been settled/gelled for several days to several weeks. For some K-Basin sludge samples that had settled/gelled for 20 to 30 days, the shear strength ranges from 1 to 8200 Pa (Poloski et al 2002, Plys and Schmidt 2009, Schmidt 2010. The shear strength of the 96-13 sample of K East Basin sludge was estimated to be 15 to 65 kPa after 28 months stored under hot cell storage conditions.…”

“…The shear strength of the sludge is one of the key sludge properties to determine whether water jets would mobilize the stored sludge in the STSCs (Onishi et al 2010). The shear strength is affected by sample history among other factors, and most of the measurements given in Poloski et al (2002) were obtained from sludge samples that had been settled/gelled for several days to several weeks. These include the shear strength range of 1 to 8200 Pa reported for K-Basin sludge samples (predominantly collected from the KE floor, KE pits, and KE canisters) from 1995-2002(Poloski et al 2002, Plys and Schmidt 2009, Schmidt 2010.…”

Strength Measurements of Archive K Basin Sludge Using a Soil Penetrometer

“…Most prior sludge strength measurements were obtained for sludge that had been quiescent for several days to several weeks (Poloski et al 2002). Shear strengths ranging from 1 to 8200 Pascals (Pa) have been reported for K Basin sludge samples predominantly collected from the KE floor, KE pits, and KE canisters from 1995 to 2002 (Poloski et al 2002;Schmidt and Sexton 2009;Schmidt 2010). These measurements were mostly conducted for samples that had settled for up to 20 to 30 days.…”