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The certification of the activity concentration of the radionuclides 137Cs, 90Sr and 40K in wild berries: IRMM-426

Abstract: 
This report describes the production of CRM IRMM-426, a dried bilberry material certified for the radionuclide activity concentrations of 137Cs, 90Sr and 40K. The material was produced following ISO Guide 34:2009. Bilberry samples were collected in a woodland region of so-called “strontium hot spots” close to the Chernobyl reactor site. The samples were air-dried at the sampling site before transport to IRMM, where the raw material was oven-dried, cryo-milled, sieved, homogenised and bottled. The bottled material was sterilised by gamma-irradiation. Between-unit homogeneity was quantified and stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006. The material was characterised by an intercomparison among laboratories of demonstrated competence and adhering to ISO/IEC 17025. Technically invalid results were removed but no outlier was eliminated on statistical grounds only. Uncertainties of the certified values were calculated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainties related to possible inhomogeneity and instability and to characterisation. The material is intended for the assessment of method performance and quality control. As any reference material, it can also be used for control charts or validation studies. The CRM is available in amber glass jars containing about 100 g of dried bilberry powder. The minimum amount of sample to be used for analysis is 50 g for 90Sr and 18 g for 137Cs and 40K.