CHARACTERIZATION OF PLUTONIUM CONTAMINATED SOILS FROM THE NEVADA TEST SITE IN SUPPORT OF EVALUATION OF REMEDIATION TECHNOLOGIES

ABSTRACT The removal of plutonium from Nevada Test Site (NTS) area soils has previously been attempted using various combinations of attrition scrubbing, size classification, gravitybased separation, flotation, air flotation, segmented gate, bioremediation, magnetic separation and vitrification. Results were less than encouraging, but the processes were not fully optimized. To support additional vendor treatability studies soil from the Clean Slate II site (located on the Tonopah Test Range, north of the NTS) were characterized and tested. These particular soils from the NTS are contaminated primarily with plutonium-239/240 and Am-241. Soils were characterized for Pu-239/240, Am-241 and gross alpha. In addition, wet sieving and the subsequent characterization were performed on soils before and after attrition scrubbing to determine the particle size distribution and the distribution of Pu-239/240 and gross alpha as a function of particle size. Sequential extraction was performed on untreated soil to provide information about how tightly bound the plutonium was to the soil. Magnetic separation was performed to determine if this could be useful as part of a treatment approach. The results indicate that about a 40% volume reduction of contaminated soil should be achievable by removing the >300 um size fraction of the soil. Attrition scrubbing does not effect particle size distribution, but does result in a slight shift of plutonium distribution to the fines. As such, attrition scrubbing may be able to slightly increase the ability to separate plutonium-contaminated particles from clean soil. This could add another 5-10% to the mass of the clean soil, bringing the total clean soil to 45-50%. Additional testing would be needed to determine the value of using attrition scrubbing as well as screening the soil through a sieve size slightly smaller than 300 um. Since only attrition scrubbing and wet sieving would be needed to attain this, it would be good to conduct this investigation. Magnetic separation did not work well. The sequential extraction studies indicated that a significant amount of plutonium was soluble in the "organic" and "resistant" extracts. As such chemical extraction based on these or similar extractants should also be considered as a possible treatment approach. WM '03 Conference, February 23-27, 2003 , Tucson, AZ 2 INTRODUCTION The removal of plutonium from Nevada Test Site (NTS) area soils has previously been attempted using various combinations of attrition, scrubbing, size classification, gravitybased separation, flotation, air flotation, segmented gate, bioremediation, magnetic separation, and vitrification (1). Results were less than encouraging, but the processes were not fully optimized. There is an opportunity for significant improvement through the utilization of more in depth studies

Magnetic Adsorption Method for the Treatment of Metal Contaminated Aqueous Waste

There have been many recent developments in separation methods used for treating radioactive and non-radioactive metal bearing liquid wastes. These methods have included adsorption, ion exchange, solvent extraction and other chemical and physical techniques. To date very few, if any, of these processes can provide a low cost and environmentally benign solution. Recent research into the use of magnetite for wastewater treatment indicates the potential for magnetite both cost and environment drivers. A brief review of recent work in using magnetite as a sorbent is presented as well as recent work performed in our laboratory using supported magnetite in the presence of an external magnetic field. The application to groundwater and other aqueous waste streams is discussed. Recent research has focused on supporting magnetite in an economical (as compared to the magnetic polymine-epichlorohydrine resin) and inert (non-reactive, chemically or otherwise) environment that promotes both adsorption and satisfactory flow characteristics

Americium recovery and purification at Rocky Flats

Americium processing at Rocky Flats Plant is described. The americium is recovered from plutonium metal by a pyrochemical process; the resulting molten salt extraction residues must be processed to recover americium. At present the process uses cation exchange with Dowex 50W-X8 resin, This work shows that a macroporous resin, BioRad AG MP-50, has 30 to 50% more capacity and better elution kinetics than Dowex 50W-X8. Two extraction methods, solvent extraction and extraction chromatography with an organophoshorus bidentate, are also described. Americium is effectively decontaminated from magnesium and aluminum, and recovered by these methods