National Physical Laboratory

Nuclear Industry Proficiency Test Exercise 2016.

Dean, J C J
NPL Report IR 39, February 2017
NPL Doc. Ref:
PDB: 8289 | DDB: 8188
Document Type:
NPL Report

Note: An asterisk after an author's name indicates a non-NPL author.


A sixth Nuclear Industry Proficiency Test Exercise has been run by NPL. One sample was prepared, consisting of a nominal 200 L drum loaded with plastic bottles (500 ml each), some containing ion exchange resin and some vermiculite. The `resin bottles' were spiked with known weights of a standard solution of 241Am, 60Co and 137Cs. The activity concentrations (averaged across the drum¿s contents) were approximately 8.3 Bq g-1, 0.83 Bq g-1 and 1.0 Bq g-1 respectively. No activity was added to the `vermiculite bottles'.The participants were required to report the activity concentrations of the individual radionuclides. Information disclosed to the participants initially included the radionuclides present, activity concentration ranges, details of the empty drum (e.g. its mass and dimensions) and the percentage of each material type present. The drum was measured by 9 UK and 7 overseas laboratories. Approximately 37 % of the initial results were statistically `in agreement' with the NPL value. The participants were then given the location of the activity within the drum and a subset of the participants submitted additional results, 65 % of which agreed with the NPL value. Results from the second round of reporting were mostly higher than those reported initially. This PTE points to possible issues with the assay of 241Am and the use of Segmented Gamma Scanners for drummed waste.

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