A Study on Optimum Design of Active Type Fuel Rod Scanner using Neutron Generator

摘要

The fuel rod scanning system in nuclear fuel fabrication facilities has been used to examine the condition of fuel rods such as the enrichment and deficit of Uranium-235. Delayed gamma rays emitted by induced fission reactions with U-235 can be a measure to quantify the U-235 contents in a fuel rod. To induce the fission reactions in a fuel rod, the neutron source has been employed in a fuel rod scanner (active type rod scanner). In this study, the optimization of the fuel rod scanner using a neutron generator was performed to change the neutron generator from a Cf-252 neutron source because of its short half-life and the periodic replacement cost. The optimum moderation system was studied by analyzing many cases of moderation structures to induce many fission reactions in a fuel rod. The shielding system between neutron source and delayed gamma ray detectors was also determined. In conclusion, the counts of delayed gamma rays in the detectors are 5.90×10~(-4) counts per neutron source. It shows 6.97-times higher efficiency than the conventional one. It is expected that the optimum design proposed in this study may compensate for the loss of neutron intensity occurring by substituting the neutron generator.