Towards a methodology for large-sample prompt-gamma neutron-activation analysis

Large-sample prompt-gamma neutron-activation analysis, or shortly LS PGNAA, is a method by which mass fractions of elements can be determined in large samples with a mass over 1 kg. In this method the large sample is irradiated with neutrons. Directly (prompt) after absorption of the neutrons photons are emitted. The presence of elements can be derived from the energy of the photons. In small samples the mass fractions of elements can be calculated directly from the measured intensities of the photons. However, when large samples are analysed there has to be corrected for three effects. These are (i) the absorption of neutrons, (ii) the scattering of neutrons and (iii) the absorption of photons. For each position in the sample the specified effects are studied separately with Monte Carlo simulations. Finally the correction methods are combined in a method for LS PGNAA. This method was tested by the determination of the mass fraction of silicon in four different samples. The mass fractions could be determined within 10 % error of the real value.Interfaculty Reactor Institut