Neutron activation analysis (NAA) is a nuclear technique in which a sample is bombarded with neutrons to produce radioactive isotopes with distinct decay patterns. It is useful for performing bulk qualitative and quantitative multi-element analysis of major, minor, and trace elements in samples. For many elements and applications, NAA offers sensitivities that are superior to those attainable by other methods, on the order of parts per billion or better. In addition, because of its accuracy and reliability, NAA is generally recognized as the "referee method" of choice when new procedures are being developed or when other methods yield results that do not agree.