Calculation of the Thermal Neutron Flux Perturbation Factor for Foil Detectors in Various Media Using the Code Perturb.D

Abstract

The code PERTURB.D computes the thermal neutron flux perturbation factor, K, due to circular foils located in an isotropic neutron field. The calculation is based on the expression K = G.E.F, where G denotes the neutron self- -shielding in the foil, E the edge correction factor and F the flux depression in the diffusing medium surrounding the foil. The code has been tested through an extensive comparison of calculated K-values with published experimental results (87 values! for several Kinds of detector of various radii and thicknesses, and in different media. It was found that, for 66% C85%D of the sample cases, our calculated K- -values agree to better than 1% C2%) with the experimental ones. As an application of the code PERTURB.D, tables of K- -values for different materials, including Nn, Co, In and Au, for diameters in the range 0.5 to 2 cm, and various pra£ tical thicknesses, both in water and graphite, are calculated and presented*.

Abridged version. FUll paper (3) — presenting the following further results: (i) tables of K-values for Sc, Cu and Dy; (ii) tables of G and G.E values for all the materials studied; and (iii) table of K-values for thermal neutron foil detectors from one of the current manufacturers, in water, paraffin, graphite and heavy water — available from the authors.