Measurement techniques used in the development of environmental radioactivity standards at the National Physical Laboratory

NPL´s Division of Radiation Science and Acoustics (DRSA) provides standards and calibration services in the fields of ionizing radiation and radioactivity, acoustics, and ultrasonics. Radioactivity standards are provided by the Radioactivity Group, which has the following functions: (1) to develop and maintain the UK primary standards for radionuclide metrology; (2) to disseminate the standards through calibration and measurement services, secondary standards and reference data; (3) to promulgate good measurement practices and provide information, advice and training courses on measurement techniques; (4) to collaborate with European and international organisations to further the development and adoption of new measurement techniques and harmonised measurement protocols. In recent years, environmental radioactivity monitoring laboratories have come under increasing pressure to demonstrate that their measurements are traceable to national standards; this has led to a demand for standards and calibration services at the environmental level. The required standards can be categorised as follows: (1) single and mixed nuclide solutions; (2) spiked reference materials (SRMs); (3) gas standards. NPL has responded to these requirements by expanding its metrological capacity in the radioactivity field to accommodate low-level measurements