Characterization of Compaction and Dryout Properties of KE Basin Sludge During Long-Term Storage

Delegard, Calvin H. ; Poloski, Adam P. ; Schmidt, Andrew J. ; Chenault, Jeffrey W.

Pacific Northwest National Laboratory (U.S.)

关键词: Cs-137;    Eu-154;    Plutonium Isotopes;    Ke Basin;    Fissile Materials;   

DOI  :  10.2172/15011820
RP-ID  :  PNNL-15092
RP-ID  :  AC05-76RL01830
RP-ID  :  15011820

美国|英语

来源: UNT Digital Library

【 摘 要 】

The long-term behavior of Hanford Site K Basin sludge with respect to loss of supernatant water and solids compaction is important in designing sludge storage and handling systems. This report describes the results of laboratory tests performed to understand and predict K Basin sludge drying and compaction rates under extended (28-month) {approx}34 C hot cell storage. Tests were conducted with six K Basin sludge materials, a control sample of simulated K Basin sludge, and a control sample containing only K Basin supernatant liquid. All samples were held in graduated cylinders fitted with threaded plastic caps. Quantitative data were gathered on how the mass and volume of K Basin sludge, and its associated supernatant liquid, changed with respect to storage time. The tests showed that the K Basin sludge samples lost water unpredictably, depending on cap seal tightness, with projected dryout times for a 1-cm cover water depth ranging from 5 to 216 months. Though the ambient radiation field ({approx}5 Rad/hour) likely contributed to cap seal degradation, water evaporation rates were found to be independent of the contained material (water vs. sludge; radioactive vs. non-radioactive sludge). Although water was lost at variable rates from sludge samples during storage in the hot cell (and, presumably, in long-term containerized storage), the sludge itself had no intrinsic propensity to enhance or diminish the rate of water evaporation compared with that exhibited by water stored in the same environment. Most of the compaction of the six KE Basin sludges and the simulated sludge occurred in the first week. Subsequent compaction to 28-months time provided little additional increase in settled sludge density. Agitating the settled sludge likewise had little to no effect on the density. However, one tested sludge contained unreacted uranium metal that began to generate corrosion product hydrogen gas after 78 days of settling and strongly altered the apparent sludge density. T he lengthy induction time shows again that uranium metal-bearing sludge may lie quiescent for long periods, even at comparatively warm temperatures, before initiating gas generation. When the testing was completed, the sludge samples were removed from the graduated cylinders. Most sludge re-suspended readily but a canister sludge sample that had previously been allowed to dry out during storage self-cemented into a hard-cake monolith and could not be re-suspended. Settled sludge density and the concentrations of 154Eu, 241Am, and the plutonium isotopes were found to follow the dry basis uranium concentration in the sludge solids. These findings amplify observations made in prior characterization studies that showed that sludge density and radiolytic, fissile material, and TRU (primarily 241Am and 238,239,240Pu) concentrations are proportional to uranium concentration. The sludge pH, found to decrease from {approx}8 to {approx}5 with a dry basis uranium concentration increase from {approx}2.5 to 82 wt% , provides data useful in designing sludge storage and process equipment.