Development and application of a prompt gamma activation analysis system in the measurement of neutron capture cross-sections of geologic materials

Abstract

A prompt gamma activation analysis system was developed using available equipment at the Texas A&M Nuclear Science Center. This system was used to obtain prompt gamma spectra from geologic materials. A series of exposures of the geologic materials and elemental standards was performed in the neutron beam emitted from Beam Port #1 at the NSC. All exposures were performed at the same reactor position and power level, but the length of the exposures was varied. The system was able to detect the presence of several elements in an interference free condition and also to identify selected elements in the geologic materials. Quantitative measures of these elements in the unknown materials were estimated from the response of the system to known quantities. For those elements for which no standard sample was exposed, a rough calculational estimate was made based on prompt gamma yield values per unit neutron exposure obtained from previous experimenters. Large diameter samples of geologic material were placed in the neutron beam and neutron transmission and scattering measurements made. The results of these transmission experiments and the elemental compositions determined by the prompt gamma system were combined to produce a value for the gross absorption cross section of the material. The values obtained for some samples were compared to values previously obtained by another method.