Methodology improvement: separation and measurement of uranium, thorium, americium, plutonium and strontium in large mass environmental samples
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Date
2012-10-16
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Publisher
Australian Nuclear Science and Technology Organisation
Abstract
This paper outlines recent method modifications implemented for the radiochemical analysis of large volume groundwater, soil and ashed tree samples. The issues addressed include the formation of silica gel, interference of polonium-210 (210Po) with the uranium-232 (232U) tracer peak in U spectra, and broadening of alpha peaks in thorium (Th) and americium (Am) spectra due to chemicals derived from separation resins. A silica gel forms in evaporated groundwater samples that increases co-precipitate volumes and sample load solution volumes. If not effectively removed, this silica gel will clog the separation resin cartridges. The addition of polyethylene glycol (PEG) followed by high speed centrifugation and filtering after co-precipitation enables the removal of this silica gel. 210Po, present in some ashed vegetation samples with activities up to 500 Bq/kg,
was sometimes found in the U fraction. The 210Po alpha emission peak overlaps the 232U tracer peak, preventing accurate chemical yield determination. An additional wash step between Am and U elution was implemented to remove 210Po from the U fraction. Organic compounds from the TEVA TM and TRU TM separation resins are leached into the Th and Am fractions respectively, resulting in broad alpha peaks. Evaporation and dilution of the fractions prior to alpha source preparation or the use of an Eichrom Pre-filter cartridge during elution is required.
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Keywords
Uranium, Thorium, Americium, Plutonium, Strontium, Environment, Sampling, Separation processes, Radiochemical analysis, Ground water
Citation
Harrison, J. J., Thiruvoth, S., & Wilsher, K. L. (2012). Methodology improvement: separation and measurement of uranium, thorium, americium, plutonium and strontium in large mass environmental samples. Paper presented to the 12th South Pacific Environmental Radioactivity Association Conference (SPERA 2012), Sydney, Australia, Tuesday 16 October – Friday 19 October 2012. Lucas Heights, NSW: Australian Nuclear Science and Technology Organisation. (pp. 54).