| 摘要 |
948,890. Reactor control rods. GENERAL DYNAMICS CORPORATION. July 19, 1962 [Aug. 2, 1961], No. 27906/62. Heading G6C. A nuclear reactor control rod comprises a support rod to which are fixed spacers at intervals therealong, cylindrical neutron absorber elements axially mounted on the support rod between adjacent spacers, and flexible metal discs between each spacer face and the adjacent absorber element end face. The absorber elements 42 and the metal discs 46 are a clearance fit in the control rod guide tube 20, the control rod being axially guided by ceramic rings on each spacer which slide on the guide tube inner surface. Movement of the control rod is effected by a circulating ball nut 64 acting on a leadscrew 62 connected through two releasable couplings 60, 38, to the support rod 22. The leadscrew 62 is rotated by a hydraulic motor 24 having associated therewith an overrun brake 68. The control valves for the hydraulic motor are housed in a portion 70 and include a valve which, in event of an emergency, connects the hydraulic motor direct to a pressurised reservoir above a gas urged piston 84. To remove the functional part of the control rod, the leadscrew casing is removed and a tool inserted to release the upper coupling 38, after which the control rod can be withdrawn upwardly by a fuel handling machine grappling a lifting head 32. The construction described is such as to allow normal working of the control rod in a distorted guide tube, and due to the cushioned axial freedom allowed each portion of the neutron absorber independently of the remainder, control rod damage due to abnormal thermal or mechanical loading is likely to be confined to a limited portion of the overall effective length of the control rod. Inadvertent dropping of the control rod due to any failure in the drive system is obviated by a solenoid operated catch 66. |
