| 摘要 |
PURPOSE:To prevent neutron absorbers from being broken to pieces and being released to the outside and to maintain a neutron absorbing function over a long period of time by providing thread parts or fitting parts in the lower part of an outer cladding pipe and inner cladding pipe. CONSTITUTION:The thread parts 29, 30 which are screwed to each other are provided in the lower parts of the outer cladding pipe 17 and the inner cladding pipe 18 and the deviation in the vertical direction of the outer cladding pipe 17 and the inner cladding pipe 18 is restrained by the thread parts 29, 30. The upper part of the outer cladding pipe 17 and the inner cladding pipe 18 is covered by an upper cap 26 provided with a stopper 31. The upper cap 26 is pinned 27 to the inner cladding pipe 18. The outer cladding pipe 17 and inner cladding pipe 18 of the control rod constituted in such a manner do not deviated in the vertical direction and, therefore, the formation of a spacing is obviated, even if the control rod elements 14 move upward and downward while rubbing the inside surface of a control rod guide pipe and a control rod insertion hole. The release of the neutron absorbers 19 broken to pieces to the outside is, therefore, obviated and the neutron absorbing function is maintained over a long period of time. |
