(1980) In order to safely operate nuclear reactors, there must be periodic inspections (in-service inspections). Two kinds of robots to inspect the peripheral parts of the steam drums within the nuclear reactor shown in Fig. 1 were developed for this purpose.

Photo.1 is the GRIPEDE, which inspects the construction safety of the welded parts of the riser pipes, and the steam drum using an UT (ultra sonic wave defectoscope). In the past there has been inspection equipment, which automatically inspected one pipe part, but when inspecting the neighboring pipe, it was necessary for the operator to come in and switch the equipment. In this regard, the 28 rising pipes of the nuclear reactor "Fugen" are arranged with extremely high precision at intervals of 450 mm in four arrays. For this reason, the approach of using the pipes as a ladder, as shown in Fig. 2, was introduced into the GRIPEDE, and by this free movement between the pipes was acquired. The mobile body has four degrees of freedom as indicated in Fig. 2. The weight is 12 kg. The time for one cycle is 50 sec. A second practical model was also prototyped.

Photo.2 is the MAGPEDE, which moves while using permanent magnets to adhere to the outer walls of the steam drum. The principle of motion is one in which up/down motion is caused by a fully reduced actuator that puts out a powerful thrust to one of the permanent magnets A, B as shown in Fig. 3, and simultaneously with this up/down motion, a sliding motion parallel to the wall is repeated. Fig. 4 shows the structure. The weight is 18 kg; it can produce an adhesive force of 3400 N with one of the permanent magnets; and as shown in Photo. 2, it can run even with a person suspended from it. By doing this, the ISI robot system, which circulates and inspects the steam drums can be configured as in Fig. 5.