Metrological references for nuclear measurements provided by LNE-LNHB to users through a strict traceability chain

The task of National Metrology Laboratories is to develop national standards and to ensure their transfer to users according to traceability requirements. In the field of radionuclide metrology, radioactive standard are characterized in terms of activity, emission flux or emission fluence rate. In France, the national metrology laboratory for ionizing radiation is LNE-LNHB. This paper describes the main measurement methods used at LNE-LNHB to establish the primary standards of activity which can then be disseminated to users, either through accredited laboratories or directly, when no commercial offer is available. Each of those measurement methods is briefly described with its associated uncertainty budget and typical measurement examples are given for radionuclides of interest in the field of fundamental physics, nuclear energy and nuclear medicine. The paper also describes how, through international measurement comparisons with other national laboratories, the quality of those national standards can be assured and checked by the users, and how this international traceability is expressed in terms of degree of equivalence between laboratories.