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Solid state NMR of 133Cs incorporated into and adsorbed on colloids formed in soils reacted with Hanford Tank Waste Solutions


EMSL Project ID
2588

Abstract

High-level radioactive waste solutions stored in the underground tanks at Hanford sites have leaked into the vadose zone. The waste tank supernatants are known to consist of solutions with high pH (9-14), high ionic strength (sodium nitrate, sodium nitrite and other electrolytes), and high aluminate concentration. The leaked solutions can dissolve some minerals such as quartz, feldspar, kaolinite, and smectite of the sediments underlying the tanks. New minerals precipitate when the leaked solutions contact the sediments. The new colloids may facilitate the transport of radioactive nuclides in the vadose zone. Cancrinite, sodalite, chabazite, and Linde Type A zeolite have been found or suspected in simulation experiments. These zeolite-like materials have high negative charge sites in their structures and therefore they are capable of incorporating and adsorbing cationic radionuclides such as Cs+ in their framework and external surfaces. Cesium-137 has been reported as one of the major radioactive elements in the Hanford tank waste supernatants. In addition to the high charge properties, the zeolite-like minerals have unique cages and channels within their structures (Figure 1), the radionuclides might be trapped in the cages or channels. The radionuclides can be released to the environment when the pH of the surrounding media becomes lower and the zeolite materials start to dissolve and transform to other crystalline or amorphous phases. It is critical to know the quantity of the radionuclides that can be incorporated and adsorbed in the newly formed colloids and their stability in the minerals. It is also important to understand the chemical environment of the sorbed and incorporated cesium, because it determines how cesium is associated with the minerals and it controls the kinetics of the sorption/desorpiton of cesium from colloids. In this proposed experiment, we will use magic angle spin nuclear resonance spectroscopy (MAS NMR) to study the chemical environment of the incorporated and adsorbed cesium in the newly formed minerals. The chemical environment of sorbed cesium on the natural colloids in the Hanford sediments also will be investigated with MAS NMR.

Project Details

Project type
Capability Research
Start Date
2002-12-01
End Date
2002-12-18
Status
Closed

Team

Principal Investigator

Youjun Deng
Institution
Washington State University

Team Members

Markus Flury
Institution
Washington State University

James Harsh
Institution
Washington State University

Related Publications

Mon J, Y Deng, M Flury, and JB Harsh. 2005. "Cesium Incorporation and Diffusion in Cancrinite, Soalite, Zeolite, and Allophane." Microporous and Mesoporous Materials 86(1-3):277-286.