Neutron activation analysis without multielement standards

A. Ahmad, P. W. Gray, T. D. MacMahon, M. Macwani
1982 Journal of Radioanalytical Chemistry  
The problems associated with multi-standard techniques in Neutron Activation Analysis are all very familiar. Preparation of standards is a source of errors and is time consuming. A new technique in Instrumental Neutron Activation Analysis has been developed which eliminates the need to prepare standards. Its application requires the knowledge of flux parameters in the reactor irradiation facility, nuclear data of reactions of interest and absolute photopeak efficiency of the counting system.
more » ... techniques used to obtain accurate values of the compound nuclear constants k^ are discussed. Particular attention is paid to the method of analysis of data used to obtain the best estimates of measured values and to the neutron flux characterisation both of which are crucial to the technique. Whereas previous authors have determined these constants from foils, it was thought worthwhile to demonstrate that they can be determined from the activation of a multi-element material of known composition. When a complex sample is irradiated in the reactor spectrum, interfering reactions come into play and neutron flux perturbations cannot be neglected. The preparation of the multi-element material was by pooling together Johnson Matthey ultra-pure solutions, k^ values for twentyfive gamma-ray lines have been determined which were then used for the analysis of NBS reference materials, coal samples from Zambia and rainwater samples collected at Silwood Park. Appropriate corrections for random pulse losses and dead time of the ADC, the possible shift of the efficiency curve when a bulk sample is analysed and absorption losses due to sample holders have been applied.
doi:10.1007/bf02516794 fatcat:4fw24a4urbf3lesch2y3ut53by