Integral reaction rates and neutron energy spectra in a well moderated reactor.

Abstract

Cadmium ratio measurements in the internal reflector of MOATA haev been made with gold, indium, tungsten, manganese, molybdenum, and copper detectors. These measurements have been analysed on the assumption that the neutron spectrum consists of a Maxwellian distribution to which is smoothly joined a 1/E slowing down spectrum, cross sections being averaged according to the methods of Westcott. A search through recent literature suggests that the s factors for gold and indium listed by Westcott are in error. If this is accepted then it appears that the measured epithermal spectrum is closely 1/E in form for neutron energies between one and six hundred eV. The corrections to be applied when foils of finite thickness are used in cadmium ratio measurements are discussed, and the spectrum derived from these measurements has been used to calculate reaction ratios of cooper: indium and copper: gold alloy foils. These ratios have been compared with measured values. Values of the effective resonance integral of Pt198 wire detectors have been measured, and from these values an estimate has been made of the infinitely dilute resonance integral of this isotope.