GB822415A - Improvements in or relating to nuclear reactors - Google Patents

Abstract

822,415. Controlling nuclear reactors. GENERAL ELECTRIC CO. Ltd. Sept. 26, 1957 [Oct. 1, 1956], No. 29924/56. Class 39(4). [Also in Group XXXV] Control means for a nuclear reactor power plant maintain a predetermined relationship between neutron flux within the reactor core and the flow of cooling medium through ducts in the core, thereby reducing thermal shock to which the reactor is subjected. The plant is set to operate on a particular loading by moving a key 8 to energize one of two contactors 10, 12 causing forward or reverse drive of a motor 7, which has a maximum speed corresponding to a change of 5% full load per minute. This motor 7 drives a shaft 3, to vary potentiometers 1 and 2 and 55 to 58, Fig. 1c. Flux control.-The setting of potentiometer 1 is compared in an automatic flux regulator 13 with the neutron flux as measured with an ion chamber 15. An error signal obtained from this regulator causes a motor 18 to drive a low frequency generator 21 through a clutch 22. This generator controls a winch to adjust the extent of insertion of control rods 34 in the reactor core as described in Specifications 822,413 and 822,414 [Group XXXV]. By changing over switches 33 the generator 21 can be manually controlled at 27. Controlling flow of cooling medium.-The shaft 3 also sets a potentiometer 2 according to the required load. This setting is compared in a polarized relay 36 by current in coil 35 with the total flow of cooling medium as measured at 39 and producing current in an opposing coil 41. When the balance of relay 36 is disturbed, a relay 45 or 46 is operated to drive ganged phase shifters 47 controlling circulators 49 of the cooling medium. Manual control at 75 is effected by changing over a switch 74. The flux /flow relationship is recorded at 50, an excessive ratio operating alarm circuits 53 and subsequently tripping the reactor. Safety and recording gear.-The setting of the potentiometer 55 is compared with the neutron flux as measured at 60 and the result is recorded at 59, an alarm circuit 62 being energized if the drift exceeds Π2%. The remaining three potentiometers, 56, 57 and 58 similarly provide comparison with the neutron flux as measured at 66, 67 and 68 to actuate relays and shut down the reactor in the event of any two ratios being excessive. Automatic control of the load setting.-The motor 7 may be operated automatically either as a result of variation in the pressure of steam generated by the cooling medium or by the output of a turbo alternator driven by this steam, A frequency sensitive network 85, Fig. 3, is supplied at 84 from the alternator output and an error signal from this network actuates either of polarized relays 96, 97 to energize the motor 7 and re-set the shaft 3. Preferably this network has an inherent delay, and an alternative form including an eddycurrent disc relay is described with reference to Fig. 4 (not shown).