| Autor: |
Thornthwaite, Alex, Clarke, Nicholas, Sharpe, Jonathan, Rackham, Jamie, Wilson, Mark |
| Předmět: |
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| Zdroj: |
Journal of the Institute of Nuclear Materials Management; 2022, Vol. 50 Issue 1, p67-82, 16p |
| Abstrakt: |
Plutonium containing fluorine compounds significantly increases the neutron flux due to the nuclear reactions between alpha particles (α) emitted from the radioactive decay of Pu and the 19F nuclei. As a result, this introduces significant measurement challenges in passive thermal-neutron coincidence counting. To address this, an innovative non-destructive assay technique was developed by Cavendish Nuclear, in collaboration with Sellafield Ltd., using high-resolution gamma-ray spectrometry (HRGS) to account for the presence of fluorine so that a more accurate estimate of the plutonium mass can be calculated. The fluoride correction technique measures the fraction of the Pu that exists in fluoride form using several key gamma rays: the 583 keV, 891 keV, 1236 keV, and 1275 keV emissions. In addition, a Pu and 241Am isotopic abundance calculation algorithm is performed using the same gamma-ray spectrum, as part of the fluoride correction technique. From this information, a more accurate estimate of the Pu-specific neutron emission rate can be calculated, which when combined with the passive thermal-neutron totals count rate, which has a much smaller statistical uncertainty and less influence from self-multiplication compared to the passive thermal-neutron "reals" coincidence count rate, yields more accurate Pu mass estimates. This work has been applied "offline" to high α-radioactive transuranic (TRU) waste drums, residue containers and packages generated from the nuclear decommissioning and clean-up of legacy nuclear facilities on the Sellafield site. The technique was also used on HRGS in-situ surveys performed in Pu oxide finishing lines; unexpected evidence of significant fluorine contamination in the held-up Pu in oxide plant equipment was discovered for the first time at Sellafield. The results and benefits from applying this technique are summarized and discussed. A new independent complimentary method of fluoride quantification in the Pu using passive fast-neutron spectroscopy methods is currently under development and is showcased here. [ABSTRACT FROM AUTHOR] |
| Databáze: |
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