k(0)-NAA, a valuable tool for reference-material producers

The main concern of producers of certified reference materials (CRM) is the preparation of high-quality products with demonstrated homogeneity and sta bility, combined with a well established set of certified characteristics. CRM producers must, furthermore, comply with other constraints imposed by t he ISO Guide 34: production processes, production control, and certification analyses should be performed by expert laboratories, using validated protocols documented in their respective quality assurance manuals; laboratory mean values and the corresponding "expanded" uncertainties, must be used for the determination of the certified values, as recommended by t he ISO Guide to the Expression of Uncertainties in Measurements (GUM); and when possible, traceability of the certified value to the SI units, using a ppropriately validated and/or primary methods, must be ensured. k(0)-NAA, i.e. neutron activation analysis with k(0) standardization, is on e of the analytical techniques implemented at the Reference Material Unit o f IRMM; it meets the first two requirements.