Precision high-speed neutron activation analysis via very short-lived activities

An automated, highly reproducible fast-transfer system (0.36+-0.001 s) has been developed, an oscillator/multichannel scaling system has been developed to follow rapidly changing spectrometer dead-times, the mathematics has been developed, and the data processing steps have been computerized. Three induced activities have been studied in some detail: sup(207m)Pb(0.80 s), sup(38 m)Cl(0.70 s), and 20F(11.03 s). Both steady-state and high-intensity pulsed reactor irradiations, with and without a Cd liner, have been used. The dead-time correction method has been carefully checked, and the overall method has been tested by the analysis of two NBS Standard Reference Materials: orchard leavas (for Cl and Pb) and bovine liver (for Cl). The advantages of employing short-lived radionuclides for INAA include: a very short sample analysis time (typically a few minutes per sample or less); the reduction of matrix interferences by using short irradiation and counting times; and reasonable sensitivities, due to the ability to tolerate high and rapidly changing counting rates. (T.G.)