Experimental determination of the epithermal flux shape-parameter factor, alpha, for the University of Arizona TRIGA Mark I reactor

Abstract

Assuming an epithermal neutron flux distribution function of the form Φ'epi(E) α 1/E¹⁺ᵅ, the epithermal flux-shape parameter, alpha, and the integrated subcadmium to epicadmium flux ratio, f, were experimentally determined for two irradiation facilities in the University of Arizona TRIGA Mark I reactor. Two equivalent approaches: the Multimonitor method and the Non-linear least-squares method, based on integral (reaction rate) techniques applied to thin foils of gold, zirconium, vanadium, dysprosium, copper, manganese and molybdenum, were used. The Non-linear least-squares approach was found superior to the Multimonitor method on the basis of smaller resulting uncertainties. The resulting parameters are: α = -.0396±.0104 and f = 16.89 ± 1.08 for the Rabbit and α = -.0296 ±.0089 and f = 19.57 ± 1.26 for the Susan, where the reported uncertainties represent one sigma values.