Year
1976
Abstract
This paper describes the National Nuclear Corporation (NNC) multichannel fuel rod scanner system (see Figure 1). This is a production line tool, designed for continuous duty in assaying commercial nuclear fuel rods. The system uses the NNC coincidence fuel assay method.1 The system uses a Cf252 source to irradiate a segment of the fuel rod as it is transported through a detector assembly located in an irradiator. The detector assembly consists of four individual plastic scintillators. As the source neutrons irradiate the fuel rods, they cause the fissile materials in the rod to fission, which results in the coincident emission of neutrons and gammas. The coincidence electronics discriminate against non-coincidence events such as the source background. The signal from the coincidence detectors is directly proportional to the rate of nuclear fission or the amount of fission material in a short segment of the nuclear fuel rod which is passing through the detector. Thus for a given flux of source neutrons, the system provides a direct indication of fissile content.