YIELDS AND ENERGIES OF DELAYED NEUTRONS FROM FAST FISSION IN URANIUM AND PLUTONIUM
Department of Physics Radiation Centre
University of Birmingham
Birmingham B15 2TT, UK.
Present addresses: * Tajoura Nuclear Research Centre, Libya
** Logica Ltd., London
*** Computer Centre, University of Birmingham
The properties of delayed neutrons from the aggregate of fragments produced by fission in uranium or plutonium are of interest not only in reactor physics but also for comparison with the summed properties of individual precursors. We report measurements on delayed neutrons from neutron-induced fast fission in natural uranium, where the interest was in absolute and fractional yields, and in 239Pu, where the interest was in energies. The primary neutrons were from an accelerator target containing tritium or beryllium bombarded by modulated beams of protons or deuterons of various energies; delayed neutrons were measured when the accelerator beam was off. For yield measurements, the fission rate in the sample was deduced from that in a 238U fission chamber mounted close to it, and the delayed neutrons were counted in a calibrated precision long counter; the sample was shuttled automatically between its irradiation and counting positions. In separate measurements, a 3He spectrometer provided the energies of delayed-neutrons from 239Pu.
KEYWORDS: Fission, uranium, plutonium, delayed neutrons, yields, energies