Reactor detection device of a nuclear reactor

The present invention provides an incore detection device to be used in a reactor pressure vessel and suitable to detection, for example, of weld lines relevant to a shroud of incore structural member from the outer side. Namely, a detection means supported by a support means is inserted into the pressure vessel. The detection means is urged to an object to be detected by an urging means. The support means comprises a holding frame having a flexible structure bendable over the entire length and a detection means disposed to the structure. The urging means is supported by the support means, and comprises a jetting means having a fluid jetting reaction as an urging force for the detection means. The support means is suspended in the pressure vessel, the detection means is suspended and supported by the supporting means, and the supporting frame is made closer to the object to be detected together with the detection means and urged against the object by the jetting reaction of the jetting means. The device of the present invention can insert the detection means even to extremely restricted positions and can detect them. (I.S.)