National metrology institutes (NMI) keep the national primary standards for all SI units and for some derived quantities required for the measurement of ionising radiation. In case of neutron measurements, the basic quantities are the total emission rate of sources and the (spectral) fluence rate. Only a few NMI’s or their associated laboratories are world-wide engaged in neutron measurements and regularly compare their primary standards in key comparisons organised by CCRI(III), the section III of the consultative committee for ionising radiation CCRI of CIPM (international committee for weights and measures). However, calibration measurements are accepted in some countries only if the measurement is traceable to their national primary standard even if the underlying procedure is supported by international comparisons. In order to overcome these restrictions, the leading NMI’s recently signed a Mutual Recognition Arrangement (MRA) which states that the calibrations of those laboratories for which the applied calibration measurement capability has been internationally approved will be accepted world-wide. Regional metrology organisations (RMO), in co-operation with the international bureau for weights and measures (BIPM), jointly organise the approval of submitted CMC’s to confirm compliance with the agreed service categories and rules for specifying the CMC’s. Provided these specifications are supported by successful participation in comparison exercises, the CMC’s and the associated degree of equivalence are published in the key comparison data base (KCDB, parts B and C) on the BIPM webpage. Calibrations performed according to approved CMC’s are then accepted world-wide.
Klein, H. (2006). International control of neutron calibration measurements. International Workshop on Fast Neutron Detectors and Applications, FNDA 2006, Kapstadt, 03-06, April, 2006, South Africa.
