Time dependent 237Np, 235U and 239Pu fission rates in a thorium assembly during the interval 0 to 200 ns using a pulsed 9Be(d,n) source—I. Experiment

Abstract

This paper describes a series of integral pulsed neutron experiments performed in a 0·4 × 0·4 × 0·4 m³ metallic thorium assembly in such a way as to allow direct comparison of space independent reaction rates with calculated reaction rates derived from a code which uses the asymptotic reactor theory approximation to describe leakage. The technique relies on the Fourier decomposition of measured space-time dependent reaction rates and the extraction from these of the reaction rate corresponding to the fundamental three-dimensional Fourier spatial mode. The reaction rates measured were the fission rates of ³³⁵U, ²³⁹Pu and ²³⁷Np following a short ∼ 10 ns) burst of neutrons with a mean energy of ∼ 2·7 MeV.