Automatic motion inhibit system for a nuclear power generating system

#Reference to the following co-pending application, Ser. No. 380,772 filed July 19, 1973, the benefit of the filing date of which is hereby claimed.

#The present invention relates to a control system for a nuclear power generating system and more particularly to a control system for preventing unnecessary reactor power reductions.

#The principles for the generation of power by a nuclear reactor have been well established and are well understood. Briefly, the reactor contains uranium or plutonium fuel elements in a core arrangement. Through the mechanism of neutron absorption and nuclear fission of the uranium or plutonium, large amounts of energy are released. This released energy manifests itself in the form of heat which is utilized to generate electricity. In the pressurized water reactor context, the heat is transferred to a primary coolant which continuously circulates through the core and carries the generated heat to a heat exchange boundary where a secondary coolant or working fluid is heated. Ordinarily the secondary coolant is water and is vaporized at the heat exchange boundary to produce steam. The steam is then circulated in a secondary system to a turbine for its ultimate use. The turbine is caused to turn at a predetermined rate and is connected to a generator for the ultimate transformation of the thermal energy to electrical energy.

#FIG. 1 is a schematic diagram of a nuclear power generating system which incorporates the automatic motion inhibit system of the present invention.

#FIG. 2 is a schematic circuit diagram of the automatic motion inhibit control system of FIG. 1.

#FIG. 3 is a schematic circuit diagram of a modified arrangement which utilizes a predetermined power demand setpoint and an inhibit locking system.

#Referring now to the drawings, FIG. 1 shows a pressurized water reactor power generating system 10 in which the present invention is incorporated. However, this should not be taken as inferring a limitation on use of the present invention as the invention is equally applicable to other nuclear power generating systems. The nuclear power generating system 10 includes a nuclear reactor vessel 12 having a core 14 which is controlled by control elements 16 which penetrate the shell of the reactor vessel 12. The control elements 16 are actuated to be driven into and out of the core 14 by driving means 18. The drive means 18 can be controlled manually from the manual control panel 43 or automatically by the automatic motion control means 42 as hereinafter described. The reactor 12 and core 14 are cooled by a primary coolant system (generally indicated by 20) which provides a continuous flow of primary coolant to and from the reactor vessel 12. The coolant exits the reactor 12 at exit nozzle 22 and is circulated to a heat exchanger 24 where the coolant gives up its heat to a secondary coolant system (generally indicated by 26). After passing through the heat exchanger 24, the primary coolant is returned to the reactor 12 through pump 28 and inlet nozzle 30. The heated secondary coolant, which is usually water, is caused to pass in its vapor form through pipe 32 of the secondary control system 26 to the turbine 34. After passing through the turbine 34 the vapor or steam is quenched in condenser 36 and eventually returned through pipe 38 by a feed water pump 40 to the heat exchanger 24.

#Normally the power level of the reactor 12 and the load on the turbine 31 are maintained to be in agreement. That is, the turbine 34 is caused to accept steam at a rate which is commensurate with the reactor power level so that the energy transferred from the primary coolant system 20 to the secondary coolant system 26 is completely utilized by the turbine 34. To maintain this agreement between reactor power level and turbine load an automatic motion control means 42 is provided which controls the average reactor coolant temperature (T.sub.AVG) to a desired value determined according to the turbine load. The automatic motion control means 42 controls the driving means 18 in response to input signals 44, 45 and 46 to lower and raise the power level. The input signals 44, 45 and 46 are indicative of the primary inlet coolant temperature (T.sub.C), the primary exit coolant temperature (T.sub.H) and the turbine load respectively. Of course, when T.sub.AVG is held steady, a balance exists between the reactor power and the turbine load.

#The turbine load signal 46 is obtained by monitoring the turbine's first stage pressure detector means 45. Such detector means 45 and the techniques for deriving turbine load from turbine first stage pressure are well known in the art of reactor turbine control.