Control rod holding mechanism in reactor

The present invention concerns a control rod holding mechanism in an FBR type reactor. The control rod holding mechanism comprises in combination an electromagnet having a bisected structure of an iron core and a coil at the lower end of a driving shaft, and a control rod is held under suspension or detached by means of the electromagnet. The feature of the present invention is that the adsorption surface of the both cores of the electromagnet has a spherical structure. Since the control rod is positioned in the reactor core coolants, it undergoes a lateral force due to fluid vibrations. Since the control rod is long, a great bending moment is applied. However, since the adsorption surface in both cores of the electromagnets has the spherical structure in the present invention, even if the bending moment is applied, the bending stress is absorbed by the slip of the adsorption surface. Further, since the gap of the adsorption surface is not changed in this case, the magnetic attraction force is not reduced. Accordingly, the control rod is hardly detached by the horizontal bending stress. In view of the above, there is no worry that the electromagnet is detached during ordinary operation. (I.S.)