Fuel assembly assay by neutron interrogation in a lead slowing-down-time spectrometer

This paper reports that interrogation neutrons from 3 eV to 3 keV are used to determine the relative sensitivity of a spent light water reactor fuel assembly assay system. The fuel assay system used for this measurement consist of three threshold fission chambers installed in the Rensselaer intense neutron spectrometer, a 75-t lead slowing-down-time spectrometer at the Gaerttner Linac Laboratory. The fission chambers detect fission neutrons from a simulated fuel assembly, and aluminum enclosure filled with depleted uranium oxide (0.2% 235U), and a 235U (93%) metal foil sample placed at various locations throughout the assembly. The measurement with the assembly are compared with a Monte Carlo analysis of an homogenized pressurized water reactor fuel assembly. This is concluded to be a practical method for the assay of spent fuel