National Physical Laboratory

Primary and secondary standards

Coincidence counter used for radionuclide standardisationA typical coincidence counter used for
radionuclide standardisation 

This service covers the provision of both primary and secondary standards of a range of alpha-, beta- and/or gamma-emitting radionuclides. Also provided under this service are standardised low-level radionuclide mixtures which are used for the annual environmental proficiency test exercises.

Gamma-ray emitting radionuclides

These are determined directly by primary counting methods or by means of the NPL ionisation chamber or other secondary standard instruments, previously calibrated using primary standards. Many nuclides are available and further details can be provided on request.

Pure beta-particle emitting radionuclides

The following are examples of radionuclides that can be standardised: 3H, 14C, 32P, 35S, 89Sr, 90Sr + 90Y, 99Tc, 147Pm and 204Tl. A standard of organically bound tritium is also available on request.

Alpha-particle emitting radionuclides

Examples are 208Po, 209Po, 229Th, 232U, 237Np, 238U, 239Pu, 241Am, 242Pu, 243Am, 244Cm, of which some are standardised by primary counting techniques.

Environmental radioactivity proficiency test exercises

NPL runs an annual environmental radioactivity proficiency test exercise of standardised environmental-level radionuclide mixtures in support of user measurements and Quality Assurance. Each exercise includes a follow-up workshop at NPL, the cost of which is included in the participation fee. Further details are available here.


Customer Service tel: +44 20 8943 8695

Last Updated: 3 Mar 2014
Created: 28 May 2009


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