title: Development of synthetic environmental radioactivity reference materials.
abstract: 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 SiO(2) 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 Bqg(-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 (60)Co, (133)Ba, (134)Cs, (137)Cs, (152)Eu, (154)Eu and (241)Am and indicative values were obtained for (55)Fe and (90)Sr.
authors.affiliation: National Physical Laboratory (NPL), Hampton Road, Teddington TW11 0LW, United Kingdom. arvic.harms@npl.co.uk
authors.forename: Arvic
authors.initials: A
authors.lastname: Harms
authors.forename: Chris
authors.initials: C
authors.lastname: Gilligan
mesh_terms: D006207:Half-Life; D038622:Internationality; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000592:standards*; D011868:Radioisotopes / Q000032:analysis / Q000737:chemistry* / Q000592:standards*; D011874:Radiometry / Q000592:standards*; D012015:Reference Standards; D012016:Reference Values
chemical_list: D011868:Radioisotopes