Interaction of Fast Neutrons with Lithium and Uranium

Abstract

This work is concerned with the investigation of neutron shielding materials that are of possible use in future fusion reactors. Measurements and calculations have been carried out for shield of LiF, u238 , a mixture of LiF and U238 and a two region of LiF and U238 The neutron source was a monoenergetic points source of energy 14.1 MeV produced by D(T,n)4He reaction at the centre of a cylindrical shield. The measurements were made with a liquid organic scintillator (NE-213), and the gamma-ray background was rejected by pulse shape discrimination using the zero crossing technique. Calcuations have been carried out in spherical geometry with a multigroup diffusion model where the uncollided flux was calculated by the removal model. The cross-section data used came from the UKNDL-file, and the YOM-20 cross-section set. Measured and calculated spectra show reasonable agreement, and do not indicate any discrepancies in the cross-section data used. Removal cross-sections at 14.1 MeV have been experimentally determined for the four shield assemblies and show a good agreement with those used in the calculations which were based on the transport cross-sections.