Method of detecting failed fuel in a reactor

Object: To insert a water-taking tube with a through-hole into a water rod to detect with high accuracy a failure of a fuel assembly in its suitable axial direction. Structure: A method of detecting a failure of fuel assembly for a light-water nuclear reactor having a water rod, which is hollow and formed in its outer peripheral wall with a plurality of through holes separated in lengthwise direction, incorporated in the center thereof, wherein a water conduit is inserted into the water rod to a suitable position lengthwise, and a first through hole in the water rod is placed in registration with a second through hole in the water conduit to jet fluids from the conduit to the fuel assembly through the second through hole and the first through hole, after which cooling water within the fuel assembly is taken from the conduit through the first and second through holes to use as specimen for detection. (Kamimura, M.)