| 摘要 |
PURPOSE:To prevent the action of rapid accelerating force at the time of start-up by loosely inserting a guide pipe of a small piston provided in an accumulator into the bottom part of the accumulator which faces a high pressure gas inlet port and boring a plurality of through holes in the sidewall of the guide pipe. CONSTITUTION:On the primary side a small piston 22 is integratedly formed through a rod 26 and a guide pipe 23 which vertically and movably receives the small piston 22 is axially and loosely inserted by facing a high pressure gas inlet port 25 of the bottom part in an accumulator 8. An appointed number of through holes 27 in which high pressure gas flows are bored in the sidewall of the guide pipe 23. Since in the above arrangement the piston 22 is positioned on the bottom part of the guide pipe 23 just after scram action start and there are few through holes 27, high pressure drive water 28 is slightly supplied in a control rod drive mechanism 2 and a control rod 4 is started at low speed. Thereafter the inserting sped of the control rod 4 is gradually increased as the piston 22 is elevated. Therefore excessive stress applied on the control rod 4 by rapidly accelerating force at the time of start can be prevented.
|
