Browsing by Author "Amatya Joshi, A"

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    Chemical removal of sulphur from AgCl and AgBr for 36Cl measurements at ANSTO
    (Australian Nuclear Science and Technology Organisation, 2021-11-17) Simon, KJ; Wilcken, KM; Amatya Joshi, A
    Measurements of 36Cl on the 6MV tandem accelerator (SIRIUS) at ANSTO began in 2016, and since then over 1000 groundwater and rock samples have been processed and measured. The challenge with the sample preparation for 36Cl is to keep the 36S rates consistently low to minimise the impact to the 36Cl ion detection. This is generally achieved by precipitating sulphate as BaSO4 before a final precipitation as AgCl. We tested a range of methods for their efficacy, ease of use and consistency in keeping the 36S rates low. For measurement, the AgCl is backed in a bed of AgBr, but the sulphur rate of commercially available AgBr can vary significantly between batches. Preparing AgBr in house can produce very low sulphur rates [1,2]. Alternatively, we have achieved similarly low 36S rates by treating commercially available AgBr in 1M HNO3 for >24 hours.
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    Sample processing improvements for actinide analysis in low level samples
    (Australian Nuclear Science and Technology Organisation, 2021-11-17) Child, DP; Chisari, R; Hotchkis, MAC; Amatya Joshi, A
    A review of the performance statistics of actinides samples measured on the VEGA AMS facility at the Centre for Accelerator Science, ANSTO indicated that inadequate yield was being achieved on a particular subset of samples, namely plutonium isotopic measurements on chemistry blanks, and on low level “clean” low matrix samples (e.g. swipes and filters) when using our routine method [1]. Absolute yields of AMS targets are difficult to ascertain due to the use of isotopic dilution analysis since measurements yield only relative ratios, and variations in ion source output and ionisation efficiency between targets make it hard to compare absolute count rates. The measured count rates of plutonium isotopes in these samples however were routinely <50% of comparable calibration and tuning materials however leading us to conclude that there was a yield issue. Additionally, development was desired on a simplified processing method for multi-actinide extraction and isolation including U, Np, Pu and Am isotopes. An investigation was conducted into the chemical loss of Pu in blanks and low matrix samples during processing as well as to determine the efficacy of a proposed multi-actinide extraction method. This investigation was able to successfully reproduce the systematic loss of Pu during ion exchange extraction chromatography which was correlated to a lack of iron in the sample matrix and its utility as a redox agent for fixing Pu during separation. A revised sample processing method was then developed and tested, confirming an increase in Pu yield >90% for all sample types including blanks and low matrix materials using this revised method. This method employed a streamlined, single pass through utilising paired Eichrom UTEVA/TEVA pre-packed resin cartridges. Additionally >80% yield was achieved on a series of tests samples for U, Np, and Am tracers when employing this revised ion exchange separation method. This revised method will be presented along with data demonstrating the improved performance of this method.