Evaluation of Phase- and Element Distribution After Non-Traditional In Situ Vitrification (NTISV) at Los Alamos National
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TRADITIONAL /N-SITU VITRIFICATION (NTISV) AT LOS ALAMOS NATIONAL LABORATORY ON A SIMULATED ADSORPTION BED
Thomas HARTMANN Environmental Science and Waste Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA, [email protected] ABSTRACT A cold test demonstration of the Geosafe® Non-Traditional In-Situ Vitrification technology (NTISV) was performed at a simulated adsorption bed by using commercial-scale equipment. A successful demonstration of NTISV at Los Alamos National Laboratory (LANL) is expected to provide a useful technology for remediation needs of EM-40 in the U.S. Department of Energy (DOT) complex on legacy buried waste containing organics and radionuclides in geological environments. Therefore, a simulated test bed including surrogates was prepared to evaluate the impact this technology has on immobilizing radionuclides. The total volume of the cold demonstration vitrification was 3.1 m x 4.6 m x 4.9 m resulting in 176,667 kg of glass or glassy constituents. A drill core sample was removed from the glass monolith and divided into 13 samples to gain spatial (vertical) information about (a) vitrification progress, (b) phase distribution, and (c) element distribution. Based upon optical microscopy, least square and Rietveld refinement of the X-ray diffraction data, the phase constitution was determined and a temperature profile estimated. The glass compositions as well as the concentrations of surrogates and trace metals were analyzed by using X-ray Fluorescence Analysis, Electron-beam Microprobe Analysis, and Scanning Electron Microscopy. In the main melting zone, in the depth range 3.7 m to 6.3 m, NTISV successfully vitrified the geological formation (Bandelier Tuffl Unit 2/3 of Tshirege) and convert it mainly into 98-99 wt.-% silicate-based glass and 1-2 wt.-% iron-based metal inclusions. Within this zone the glass compositions have been found to be nearly constant and the surrogate elements (cerium and cesium) are distributed homogeneously. INTRODUCTION A cold test demonstration of the Geosafe Non-Traditional in-situ Vitrification technology (NTISV) was performed at a simulated adsorption bed by using Geosafe's commercial-scale equipment. Between 1945 and 1961, three former adsorption beds received effluent from a nuclear laundry and are now contaminated with a number of radionuclides. A successful demonstration of NTISV at LANL is expected to provide a useful technology for remediation needs on legacy buried waste containing organics and radionuclides in geological environments. Therefore, a simulated adsorption bed including surrogates was prepared to evaluate the impact of this technology on immobilizing radionuclides. The surrogates (6.5-kg Cs 2CO 3 and 30-kg CeO2) were placed on the floor of the adsorption bed. The total volume of the vitrified tuff after cold demonstration was estimated to be 3.1 m x 4.6 m x 4.9 m (10 ft x 15 ft x 16 fi) resulting in 3 67.95 mr or 176,667 kg of glass or glassy constituents. If NTISV is capable of providing perfect homogeneous element distr
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