Patent GB-1173730-A (GB)
Title: Control System for a Nuclear Reactor Plant
IPC: G21D3/10
Filed: 1968-11-18
Abstract: 1,173,730. Controlling reactors. SULZER BROS. Ltd. 18 Nov., 1968 [14 Dec., 1967], No. 54632/68. Heading G6C. A control system for a nuclear reactor in which control rods are arranged in zones includes means for measuring the outputs of the individual zones, means for measuring the total output of the reactor, and control means which produces an identical and simultaneous adjustment of the control rods in all the zones in response to a deviation in the total output of the reactor and which produces an identical and simultaneous adjustment of the control rods in one zone in response to a deviation in the output of that zone. Fig. 1 shows a top plan of a reactor sub-divided into four zones I, II, III, IV with one set of control rods associated with each of these zones (only one control rod of each set being shown). The set of control rods for zone I represented by the control rod 35 is mounted on a rack 36 which meshes with a pinion 37 of a positioning motor 38. The other sets of control rods are similarly mounted. The motor 38 is controlled by a controller 40 via an amplifier 39. The input values of the controller 40 are the outlet temperature # 1  of the coolant gas of zone I, the mean value ## of the four outlet temperatures # 1 , # 2 , # 3 , # 4 , and a signal originating from a pressure controller 50. As a feed-back value for the amplifier 39, a signal corresponding to the neutron flux density in zone I, as measured by means of a neutron monitor 41, is used. The signal is superimposed on the amplifier 39 so that with increasing neutron flux, the control rods of zone I are lowered. The outlet temperature # 1  is measured in the outlet connecting branch 6 of zone I by means of a thermometer 42 and is fed to the controller 40 via a signal line 43. The values of the outlet temperatures # 1 , # 2 , # 3 , # 4  of the four zones are supplied through signal lines 44, 45, 46, 47 to an adding device 48, which forms therefrom the mean outlet temperature T. This is fed to the controller 40 of zone I via a signal line 49. A signal corresponding to the deviation of the line steam pressure p in the steam line 23 of the generating plant 15 is formed in the controller 50, this being supplied with the line steam pressure p through a pressure transducer 52 and a set value of the line steam pressure through a signal line 53. The generating plant 15 includes a heat exchanger 14 supplied with water by a feed pump 20, the water being heated in a steam generator 21, vaporized and subsequently superheated in a superheater 22. The mean temperature T formed in the adding device 48 is also supplied through a signal line 60 to a temperature controller 61 which controls the drive motor 62 of the coolant circulating pump 16. As a feed-back value, the controller 61 is supplied with a signal from a flow-meter 63 which measures the rate of flow m of coolant gas delivered by the pump 16, and is also supplied through a signal line 64 with the set temperature value for the mean temperature of the coolant gas at the outlet connecting branches of the zones I, II, III, IV. The drive motor 62 of the pump 16 is controlled such that the mean temperature # remains constant. In the embodiment described, it is not the total output as such that constitutes the controlled condition but rather the pressure p of the working medium of the power plant. This pressure is a parameter which represents an integrated balance between the desired output value (the quantity of steam required by the turbine) and the actual value of the quantity of steam supplied. Therefore the deviation of the pressure from the set value is a value which is approximately proportional to the time integral of the deviation of the output from the set value.