ANALYTICAL BASIS FOR NEUTRON-ACTIVATION ANALYSIS MEASURING NUCLIDES WITH A HALF-LIFE OF 2ND-ORDER

An analytical basis for a neutron-activation analysis (NAA) for measur ing nuclides of second-order half-life produced by the (n, gamma) reac tion has been studied using a neutron-activation analysis facility (PN -3) of JRR-3M. The NAA facility, comprising a fast pneumatic irradiati on system and a high count-rate gamma-ray spectrometer, is able to aut omatically conduct NAA with short-lived nuclides. Basic experimental c onditions, such as a high count-rate gamma-ray measurement, the effect s of irradiation-capsule material and the stability of the neutron flu x, were examined. The analytical sensitivities and detection limits fo r 20 elements of which activated radionuclide having half-lifes from 0 .7 to 100 s were obtained. Scandium, In, Dy and Hf were elements havin g the highest analytical sensitivity, with detection limits down to 4. 2 to 14 ng. Fluorine, which is difficult to determine by other methods , can be detected at above 530 ng. Analytical applications of NAA with short-lived nuclides have been carried out for F, Se, Sc, Hf In and D y in various materials, including reference materials. The accuracy, p recision and detection limits of NAA with short-lived nuclides have be en evaluated.