A re-examination of coincidence and gamma-peak doublet handling in Kayzero-based NAA

In order to further strengthen at DSM Research the key analytical technique "neutron activation analysis" based on the KAYZERO/SOLCOI(C) software package, a project was recently started aiming at, among others, improvements in the correction for true-coincidence and in the automatic handling of peak multiplets. Problems could be identified in the calculation of true- coincidence correction factors for a number of analytically important cascade gamma lines of about 20 radionuclides including those formed from the elements Fe, As, Zr, Mo, Ag, Sb, some rare earth elements, Ta, W and U. As an example, in the present paper an outline is given of sources of error - caused by computer programming, decay scheme analysis or selection of relevant decay data - that are related to the measurement of As-76, Sb-124, Nd-149, Ta-182 and W-187. For some radionuclides, k(0)-factors of analytically relevant gamma lines present in multiplets (in most cases doublets) were formerly not available. Hence, problems existed with the automatic computer-assisted conversion of input peak areas to output analytical results. Therefore, remeasurement of the individual k(0)-factors was carried out by using a high-performance Ge-detector and a gamma-spectrum analysis program with proven accuracy. This study involved a number of gamma lines of radionuclides for the determination of some 10 elements among which Mo, Pd, Ag, Eu and U were included. This now leads to the elimination of important data processing errors.