Gadolinium-neutron-activation determination with a Pu-Be source

A nondestructive neutron activation method for determining gadolinium content for reactor construction materials was developed. The method uses a Pu-Be neutron source capable of giving 108 neutrons per second and the neutron reaction with a 160Gd target. To determine the flux attenuation, induced-activity distributions were measured along the radius with artificial compacts of Al2O3 + Gd2O3 specimens with varying gadolinium contents. The specimens were irradiated in unscreened and screened containers. The ratios of the unfiltered and filtered activities were not more than 1.06 +/- 0.04. The dependence of the gamma-ray absorption coefficient on gadolinium content and the effect of gadolinium content on the count rate due to 161Gd were determined. The nondestructive neutron-activation determination of gadolinium was possible for gadolinium concentrations where the radial induced-activity distribution was constant. The method for calculating the gamma-ray absorption coefficient was simple and reliable for measurement geometry close to 4pi. Neutron activation results agreed with chemical measurement within the error limits