Improved Analytical Characterization of Solid Waste-Forms by Fundamental Development of Laser Ablation Technology
Laser ablation (LA) with inductively coupled plasma mass spectrometry (ICP-MS) has been demonstrated as a viable technology for sample characterization within the EM complex. Laser ablation systems have been set up at the Hanford Site, Savannah River Plant, the Pu immobilization program (MD), Los Alamos, and at numerous other DOE facilities. Characterization of elemental and isotopic chemical constituents is an important function in support of tank-waste operation and remediation functions. Proper waste characterization enables safe operation of the tank farms, resolution of tank safety questions, and development of processes and equipment for retrieval, pretreatment, and immobilization of tank waste. All of these operations are dependent on the chemical analysis of tank waste (1). A specified need by the Tanks Focus Area (TFA) is to validate the laser ablation mass spectrometer (LA/MS) technology through round robin testing of standard materials and through fundamental studies of the laser ablation process (2). Advancement of the laser ablation technology is warranted to guarantee accuracy of analysis for the diversity of complex EM samples. This EMSP research endeavored to understand fundamental laser-ablation and ICP-MS detection characteristics, to ensure accurate and sensitive analytical characterization for EM wastesite samples. The difficulty in characterization of EM waste samples is that matrix-matched standards are not available. ICP-MS instrumental calibration must be performed with a series of standards. The sample-matrix will influence the ablation process, such as an amount of ablated mass, elemental fractionation, particle size distribution and particle transport characteristics, and ICP-MS response. If matrix-matched standards existed, the quantity of mass, degree of fractionation, and particle transport would be the same for standards and samples; hence, accuracy of analysis would be guaranteed. In contrast, for most EM samples in which standards are not available, accuracy can only be accomplished through knowledge of the laser ablation processes. Laser ablation offers direct characterization of any solid waste form in a timely manner and at a reduced cost compared to conventional analytical technologies (3-5). Numerous advantages exist for direct solid waste-form characterization. Little or no sample preparation will be required. Laser ablation will eliminate the dissolution requirement, and eliminate the generation of solvent waste. Personnel exposure to hazardous materials will be minimized. Chemical characterization 6 using laser ablation requires a smaller amount of sample (<micrograms) than that required for conventional solution nebulization (milligrams). Depending on the analytical detection system, picogram to nanogram quantities may be sufficient for analysis. The smaller sample requirement will also minimize contamination of equipment. Finally, because photons are used for sampling, any sample can be laser ablated. The sample can be homogeneous, heterogeneous, radioactive, stable, inorganic, organic, biological, sludge, saltcakes, soils, anything. The focused laser beam permits spatial characterization of heterogeneities in solid samples. Because of these capabilities, laser ablation has received a great deal of attention; numerous analytical studies are described and reviewed in the literature (5-18).
- Research Organization:
- Lawrence Berkeley National Lab., Berkeley, CA (US)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM) (US)
- OSTI ID:
- 828184
- Report Number(s):
- EMSP-55318-2000; R&D Project: EMSP 55318; TRN: US0404489
- Resource Relation:
- Other Information: PBD: 31 Dec 2000
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
54 ENVIRONMENTAL SCIENCES
ABLATION
CHEMICAL ANALYSIS
HAZARDOUS MATERIALS
LASERS
LOS ALAMOS
MASS SPECTROMETERS
MASS SPECTROSCOPY
PARTICLE SIZE
SAMPLE PREPARATION
SAVANNAH RIVER PLANT
SOLID WASTES
STORAGE FACILITIES
WASTE FORMS
WASTES