Tank Waste Treatment Science Task quarterly report for January--March 1995

Abstract

SummaryThis report describes the work performed by the Pacific Northwest Laboratory during the second quarter of FY 1995 (January -March 1995) under the Tank Waste Treatment Science Task of the Tank Waste Remediation System Pretreatment Technology Development Project. Work was performed in the following areas: 1) analytical methods development, 2) sludge dissolution modeling, 3) sludge characterization studies, 4) sludge component speciation, 5) pretreatment chemistry evaluation, and 6) colloidal studies for solid-liquid separations. Significant accomplishments during the second quarter FY 1995 are highlighted below:The particle size analysis system for measuring of particulates in solution is ready for general research use, with user-verified operating procedures.Computer code modifications were completed, which allow the computation of parameters for the ESP model using our extensive thermodynamic properties database.A model for plutonium solubility in mixed NaOH/NaNO,/NaNO, systems was developed that provides predictions in good agreement with the experimental data.Transmission electron microscopy studies of Tank T-1 1 1 samples indicates that sludge washing removes the soluble phosphate salts [e.g., NqH(PO,),]; does not affect the other major components of iron, bismuth, manganese, and silicon, which appear to exist as amorphous FGBi(SiO,),OH; and causes the larger agglomerates to disperse into fine aggregates with a primary aggregate size of -50 nm, making solid-liquid separations difficult.X-ray diffraction analysis of Tank S-104 sludge indicates that the majority crystalline phase is boehmite. The colloidal properties of boehmite have been extensively studied in this task, and boehmite has been observed to form a variety of stable colloidal dispersions.Strontium incorporation into calcium minerals in several tank sludges was confirmed by x-ray absorption spectroscopy.Studies were initiated that were designed to develop sludge wash factors for single-shell tank wastes via analysis of experimental and historical tank inventory data.A preliminary statistical analysis using the SORWT model to evaluate tank waste physical properties indicated that centrifuged solids density is the only physical property with significant differences between SOWRT groups.Studies of Fe(OH), and Tank C-103 sludge simulant suspensions indicate that their colloidal properties are qualitatively the same as those of beohmite and gibbsite, and that baseline assumptions concerning solid-liquid separations may be inadequate.iii Results suggest the sensitivity of sedimentation rate to container geometry is due to an "instability" regime in the formation of floc networks, which must be accounted for in the design and interpretation of sedimentation experiments.Studies of Tank C-103 simulant suggest that apatite is capable of scavenging fine particles from basic supernatant liquids via a heterocoagulation process. iv

Status Report on Phase Identification in Hanford Tank Sludges

“…In this report, we summarize the results obtained through FY 1999. Aspects of this summary already have been reported (Lafemina 1995;Lumetta et al 1998;Rapko et al 1996).…”

Retrieval process development and enhancements waste simulant compositions and defensibility

“…Thus, most of the siniulants used for retrieval system testing &e., those included in this report) are physical rather than chemical simulants. Others have developed chemical waste simulants (Elmore et al 1992;LaFemina 1995).…”

Use of Sol−Gel Systems for Solid/Liquid Separation

“…The high concentration of salts in HLW also presents difficulties in controlling the rheological properties of the waste suspensions. Previous studies have shown that in dispersed HLW systems with low particulate concentrations, the suspensions behaved like Newtonian fluids, but relatively minor increases in solids concen-trations (e.g., to 8 vol % solids) led to gel formation (Rector and Bunker, 1995;LaFemina et al, 1995). Under certain conditions of pH, salt concentration, and storage time, gels were formed at even lower solids concentrations (e.g., 3 vol %).…”