LOW PRESSURE LOSS FUEL ASSEMBLY FOR PRESSURE TUBE HEAVY WATER REACTOR

摘要

PURPOSE:To lower the pressure loss of a fuel assembly to accomplish high burnup by attaching an axial center support tube alone to an upper tie plate to make the upper end of a fuel rod free so as to increase the coolant flow passage cross section of the upper tie plate. CONSTITUTION:A coolant allowed to flow from a lower tie plate 4 passes through a flow opening having a large cross section surrounded by the circumferential ring part 1a, an axial center attached part 1b and a connection part 1c of an upper tie plate 1. And, since the coolant is allowed to flow out from a passage hole of an upper end plug 2c, the flow resistance of the coolant reduces sharply. Further, a lower end plug 2b is fixed on the lower tie plate 4 and the stable support of a parallel state can be secured to obtain the strength of the whole by providing spacers to increase their number. In addition, because the fuel rods are free for the upper tie plate 1, there is no fear of receiving an excessive force.