Review of neutron activation analysis in the standardization and study of reference materials, including its application to radionuclide reference materials

Abstract

Neutron activation analysis (NAA) plays a very important role in the certification of reference materials (RMs) and their characterization, including homogeneity testing. The features of the method are briefly reviewed, particularly aspects relating to its completely independent nuclear basis, its virtual freedom from blank problems, and its capacity for self-verification. This last aspect, arising from the essentially isotopic character of NAA, can be exploited by using different nuclear reactions and induced nuclides, and the possibility of employing two modes, one instrumental (nondestructive), the other radiochemical (destructive). This enables the derivation of essentially independent analytical information and the unique capacity of NAA for self-validation. The application of NAA to quantify natural or man-made radionuclides such as uranium, thorium, 237Np, 129I and 230Th is discussed, including its advantages over conventional radiometric methods, and its usefulness in providing independent data for nuclides where other confirmatory analyses are impossible, or are only recently becoming available through newer “atom counting” techniques. Certain additional, prospective uses of NAA in the study of RMs and potential RMs are mentioned, including transmutation reactions, creation of endogenously radiolabelled matrices for production and study of RMs (such as dissolution and leaching tests, use as incorporated radiotracers for chemical recovery correction), and the possibility of molecular activation analysis for speciation.