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NPL nuclear industry proficiency test exercise 2012.

Dean, J C J (2013) NPL nuclear industry proficiency test exercise 2012. NPL Report. IR 30

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Abstract

A fourth Nuclear Industry Proficiency Test Exercise has been run by NPL. One sample was prepared, consisting of a nominal 200 L drum loaded with steel and Nylon sheets and plastic bottles containing coarse aggregate (with one containing ion exchange resin). The steel sheets and the resin bottle were spiked with known weights of standard solutions of Americium-241, Cobalt-60 and Caesium-137. The activity concentrations (averaged across the drum's contents) were approximately 2.8 Bq/g, 1.0 Bq/g and 1.0 Bq/g respectively. The participants were required to report the activity concentrations of the individual radionuclides. Information disclosed to the participants initially included the radionuclides present, and activity concentration range, details of the empty drum (e.g. its mass and dimensions) and the percentage of each material type present. The drum was measured by 11 UK and 3 overseas laboratories. After the initial results deadline, further details of the distribution of materials and activity within the drum were disclosed, and the participants were invited to submit additional data. It was pointed out that, during the transport process, the bottles in the drum had moved and it was concluded that the 'active bottle' could have been positioned anywhere in the base of the drum when measured by the participants (although probably within 25 cm of the base). Approximately 44% of the 'initial' results were statistically 'in agreement' with the NPL value. This was partly due to the large proportion of questionable and discrepant data submitted for Americium-241. As in earlier exercises, some of the results derived using Segmented Gamma Scanners were either low, questionable or discrepant. Four participants submitted additional results after NPL had disclosed the drum's internal matrix structure; however, the overall proportion of results 'in agreement' with NPL was only 27% (compared with 53% for the same four participants 'pre-disclosure').

Item Type: Report/Guide (NPL Report)
NPL Report No.: IR 30
Subjects: Ionising Radiation
Ionising Radiation > Radioactivity
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/5925

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