Tritium measurement proficiency testing
NPL provides a performance test for dosimetry services who measure tritium-in-urine as part of their internal dose assessment procedures.
The Health and Safety Executive's HSE Statement on the Approval of Dosimetry Services states that all UK dosimetry services seeking approval are now required to undertake a relevant performance test if there is one available. For tritium-in-urine measurements, the relevant test requires the dosimetry service to measure a set of 'blind' samples of tritium-in-water provided by an independent testing laboratory. Once approved, the dosimetry service must take part in a repeat test once every 18 months. NPL provides such a test, and does so in accordance with the relevant HSE protocol.
To minimise costs to the individual dosimetry services, a large batch of samples is prepared by NPL once every 18 months and the test is offered to all participants simultaneously. One-off tests can be provided outside the normal schedule, although at a higher cost.
The next round of tests is scheduled for December 2013.
Details of performance test
NPL provides each participating dosimetry service with a set of 15 tritium-in-water samples with activity concentrations within the range 40 to 850 Bq g-1. Of the 15 samples, five contain added tartrazine (at a concentration of 13 mg L-1) and 5 contain tartrazine at 26 mg L-1. The dosimetry service must measure the tritium activity concentration in each sample and reports their results to NPL who will then prepare a Performance Test Report for sending directly to the dosimetry service. This report states the reported and true activity concentrations and assigns the dosimetry service to the relevant HSE Performance Band based on the results of the test.
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