Interaction between closely-spaced indium foils in light water

Abstract

Interactions between closely-spaced indium disc foils of 1 cm dia. and 0.0127 cm thick exposed to an isotropic thermal flux in light water, were experimemtally studied with a view to establish the closest distance between them at which no significant perturbation was experienced. This investigation, therefore, was undertaken to determine the flux perturbation factors (defined as the ration of thermal neutron flux present in the foil to the unperturbed thermal neutron flux) for various interfoil distances. It was observed that these factors changed from a value of 0.833 ± 0.019 (large perturbation) for 1.5 cm interfoil distance (centre to centre) to 0.986 ± 0.015 (small perturbation) for 1.8 cm interfoil distance, where the unperturbed flux was taken as the measurement with indium foils being 6 cm apart. It was, therefore, concluded that interaction between neighbouring foils of 1 cm dia. and 0.0127 cm thick became small for interfoil separations greater than 1.8 cm.