Photoneutron Target Design for Fast Neutron Spectrum Measurements

摘要

The potential application of thorium in nuclear fuel cycles has led to a need for improved thorium data for reactor calculations. The measurement of neutron spectra emanating from homogeneous assemblies containing thorium can provide integral data of benchmark quality against which the adequacy of differential nuclear data can be tested. At RPI the thorium integral experiments currently underway utilize a 0.6-m-dia. spherical assembly of thoria which was designed, constructed and originally used in conjunction with the spectrum measurements program of the Research Reactor Institute of Kyoto Univ. (KUR) in Japan. The assembly has been made available on loan to RPI, to extend the measurements to higher energies and to greater resolution with the well-established time-of-flight facilities at the RPI Gaerttner LINAC Laboratory. Previous measurements at KUR on this assembly employed a 5-cm-dia. cylindrical lead target located inside the assembly through a 5-cm-dia. reentrant hole. This target was limited to a maximum of approx. 120 watts of electron beam power and it was not specifically designed to yield an isotropic distribution of emergent neutrons. This paper describes the design and testing of a higher powered target which produces a more isotropic distribution of emergent neutrons. (ERA citation 04:039444)