The chemistry of underground storage tanks containing high-level waste (HLW) at the Hanford Site in Washington State is an area of continued research interest. Thermodynamic models have predicted the formation of analcime and clinoptilolite in Hanford Tank, rather than cancrinite; however, these predictions were based on carbonate-cancrinite. We report the first observation of a nitrate-cancrinite [possibly Na8K(AlSiO4)6(NO3)2•nH2O] in fully radioactive Hanford Tank waste evaporated to 6M, 8M, and 10M NaOH concentrations. The nitrate-cancrinite phase formed spherical aggregates (4 ?m in diameter) that consisted of platy hexagonal crystals (~0.2 ?m thick). 137Cs was concentrated in these silicate structures. These phase possessed identical morphology as nitrate-cancrinite precipitated in Hanford Tank non-radioactive simulant tests supporting the contention that it is possible to develop non-radioactive artificial sludges. This investigation points to the continued importance of understanding the solubility of NO3-cancrinite and related phases.
Revised: March 14, 2005 |
Published: August 15, 2004
Citation
Buck E.C., and B.K. McNamara. 2004.Precipitation of Nitrate-Cancrinite in Hanford Tank Sludge.Environmental Science & Technology 38, no. 16:4432-4438. PNWD-SA-6242.