| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic sealing method of a fuel assembly upper nozzle as a guaranteeing measure against fuel of a highly reliable fuel assembly. SOLUTION: A fuel rod 15 opposed to a ligament 19 of an upper nozzle 11 is selected by at least one, the selected fuel rod 15 is sealed by a long size upper end part plug 1 in close vicinity to the opposed ligament 19, bolt holes 3, 2 adapted to a bolt 5 with an ultrasonic sealing function are respectively board in the ligament 19 and the opposed long size upper end part plug 1, the bolt 5 with an ultrasonic sealing function is screwed in the bolt hole 2 arranged in the long size upper end part plug 1 of the fuel rod 15 through the bolt hole 3 arranged in the ligament 19, and a stage is provided to detect/ confirm a sealing state by recording ultrasonic data when fastening the bolt 5 with an ultrasonic sealing function in this bolt hole 3.
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