GB1090632A - Nuclear reactor control mechanism - Google Patents

Abstract

1,090,632. Reactor control rods. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. July 30, 1964 [Aug. 16, 1963 (2)], Nos. 32591/63 and 32592/63. Heading G6C. In a nuclear reactor control mechanism having a neutron absorbing body movable relative to the core by means of a flexible tie between it and the winch, the control rod is spring biased towards its active position, and withdrawn from this position, against the spring, by the winch and tie. The control unit is an integral structure housed in a casing 115 (Fig. 1), and retained in a standpipe 113 by balls 117. The unit contains a shield plug 120 penetrated by leads 119 for an electric motor 121, which drives a winch 122 to raise the safety rod 124 through chain or cable 127, against pressure from the spring 125. After initial insertion of the unit in the standpipe, the motor is energized to withdraw the safety rod 124 to its normal position within the casing 115. In an emergency, a clutch 123, between the winch and motor, is released, allowing the spring to force the safety rod into the core 111. Alternative drives.-In a first modification, the clutch and motor are replaced by two hydraulically actuated pawls which engage a ratchet wheel on the cable drum. One of the pawls allows winding-in rotation and prevents unwind of the drum. The other pawl is reciprocated, to wind the drum. For emergency shutdown, the first pawl is hydraulically withdrawn from the ratchet wheel, thus allowing the spring 125 to forcibly insert the safety rod. The second modification allows the associated rod to be used for normal reactivity control and for emergency shutdown. Wind-in is achieved as previously described, but a further hydraulic piston and cylinder unit actuates two pawls, each engaging a separate ratchet wheel, so as to allow tooth-by-tooth re-insertion of the control rod. A third hydraulic unit withdraws the pawls to enable the spring to rapidly insert the control rod.