Development of synthetic environmental radioactivity reference materials

In this paper, a novel way of developing synthetic environmental radioactivity reference materials via the sol–gel process is described. Two solid reference materials (both having a SiO2 matrix) were synthesised by hydrolysing a liquid mixture of tetraethyl orthosilicate (TEOS), ethanol and standardised mixed radionuclide solutions. The certified values, which were in the Bq g−1 range, for the radionuclides in the material were determined by NPL and compared with results from measurements made by 36 organisations from 17 countries using a ‘consensus’ approach. The measurements were made within two wider test exercises (the NPL Environmental Radioactivity Proficiency Test Exercises 2009 and 2010). Certified activity concentration values were obtained for 60Co, 133Ba, 134Cs, 137Cs, 152Eu, 154Eu and 241Am and indicative values were obtained for 55Fe and 90Sr.

► Synthetic radioactivity reference materials were developed via the sol–gel process.
► Certified values for radionuclides were determined and compared with PTE results.
► Results were obtained for Co-60, Ba-133, Cs-134, Cs-137, Eu-152, Eu-154 and Am-241.