Monte Carlo calculation of epithermal neutron resonance self-shielding factors in wires of different materials

Abstract

Epithermal neutron resonance self-shielding factors in wires of materials used as activation detectors or as targets for radionuclide production have been calculated using the MCNP code. The energy dependent self-shielding factor depends on the ratio scattering/capture cross sections. The self-shielding factors for cobalt and gold have been compared with available values. The self-shielding factor depends on various physical and nuclear parameters. However, an adimensional variable can be adopted that describes the self-shielding factors of different materials by a quasi "universal curve".

Mathematical formulae for neutron self-shielding properties of media in an isotropic neutron field

“…3. Experimental results from literature of Gonalves et al [17], Lopes [62,63], McGarry [64], Brose [65], Yamamoto et al [66], Jefferies et al [67], Eastwood & Werner [60], and Kumpf [68] were used for comparison. Elements were Au, Co, Mn and Na in a form of wire, foils or infinite slabs.…”

“…3 using the interaction probability of Eq. 33, with experimental values taken from Gonalves et al [17], Lopes [62,63], McGarry [64], Brose [65], Yamamoto et al [66], Jefferies et al [67], Eastwood & Werner [60], and Kumpf [68]. (F:Foil, W:Wire, S: Infinite Slab, and G: General Convex body, our approach).…”

“…There is an interplay between neutron absorption in the sample and the overall neutron flux [14]. Predominantly, the correlation between neutrons self-shield factors and the set of parameters involved in the calculation of its value had been studied by several scientists [15][16][17][18][19][20][21][22][23][24][25], who gave dimensionless variables to identify and encompass the physical and geometric varieties of the samples geometries in order to attain a universal formula for self-shielding. The Montè-Carlo approach effectively calculates self-shielding, but it takes time and an experienced user to achieve acceptable accuracy and efficiency [26], see Appendix E. Empirical expressions such as those given by researchers in Refs.…”

“…The Montè-Carlo approach effectively calculates self-shielding, but it takes time and an experienced user to achieve acceptable accuracy and efficiency [26], see Appendix E. Empirical expressions such as those given by researchers in Refs. [17][18][19][20][21] based on Ref. [15], had became routine in calculating self-shielding, these empirical expressions have been derived for a few specific geometries and limited number of elements.…”

Monte Carlo Simulation of Correction Factors for Neutron Activation Foils

“…The program can be used for calculations with multi-element samples and applicable only for reactor isotropic neutron field. Gongalves et al [8,9] performed resonance neutron self-shielding factors for foils and wires of different materials by using the MCNP code and proposed universal curves for a number of neutron source geometries, and applicable only for single element samples.…”