Gas pressure measuring device in fuel rod

The present invention provides a device for measuring a gas pressure in a fuel rod of BWR by measuring the pressure of a helium gas in the fuel rod when the gas is diffused. Namely, a fuel rod is secured in a vacuum vessel, a small hole is perforated to the fuel rod and the pressure of the helium gas sealed in the fuel rod is measured when the gas is diffused. As a result, the pressure of the gas in the fuel rod can be measured. In this case, on the inner circumferential surface of a fuel rod end plug-receiving portion of the vacuum vessel, a tapered portion having a diameter gradually increased toward the central portion of the vacuum vessel is formed. Since the outer circumferential edge of the top end of the fuel rod is abutted entirely against the tapered portion, the position is secured reliably. As a result, the fuel rod is supported at two points of a sealing device and the of tapered portion in the vacuum vessel. Since the top of a drill blade is in contact with the fuel rod at a position between both of the supporting points, the fuel rod does not bend upon processing. Then, sealing property is not deteriorated upon perforation. (I.S.)