ABSTRACT
Neutron activation analysis (NAA) and prompt gamma neutron activation analysis (PGNAA) are proven methods of elemental analyses traditionally performed at nuclear research reactors. With NAA, samples are irradiated with highly thermalized neutrons inside the reactor and then taken to a low background counting area where the induced radioactive decay products are analyzed. e intensities of the obtained specic gamma rays provide information about the number of atoms in the sample. Hence, the information on its chemical composition can be extracted from the measured gamma ray spectrum. NAA can be used to measure the concentrations of many elements, often with very high (<ng/g) sensitivity, but it is not sensitive for about one third of the elements where no radioactive product can be produced. PGNAA utilizes a neutron beam, external to the reactor, to irradiate a sample, which then emits prompt γ-rays with energies and cross sections characteristic of all elements. With PGNAA, sensitivities up to <0.1 mg of any element, except helium, can be achieved; see some of the numerous textbooks on the subject (Koch 1960; Bowen and Gibbons 1963; Taylor 1964; Lernihan and omson 1965; Kruger 1971; De Soete et al. 1972; Nargolwalla and Przybylowicz 1973). Both NAA and PGNAA oer the distinct advantage that many elements in a small sample can be simultaneously and accurately analyzed. Traditionally, NAA and PGNAA have been limited to research reactor laboratories that are not always conveniently accessible to scientists around the world, although, there are currently about 380 research reactors worldwide.
