JP5352375B2 - Reactor power controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain a water level of a reactor from reaching a high water warning level even though manipulation is performed to insert control rods at the same time during a low-output operation such as a start-up range. <P>SOLUTION: A control unit has a control rod manipulation limiter which stops a control rod drive device from manipulating control rods when the water level of the reactor becomes a limitation level set between a target water level and a high water warning level and a setter which sets set points of the high water level warning level and/or that of the limitation level at different ones according to reactor power levels. Even though manipulation is performed to insert a plurality of control rods at the same time during a low-output operation such as a start-up operation, the water level of the reactor can be restrained from reaching the high water warning level. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a reactor power control apparatus and a reactor power control method.

  The nuclear power plant has various control modes. Each control mode is controlled by setting a control target. When the boiling water reactor (BWR) is started up, the control mode is a critical control mode for bringing the reactor from a shutdown state to a critical state, and the reactor pressure is reached to reach the target value according to the target value of the reactor water temperature change rate. There are a temperature / boost control mode and a reactor power control mode for controlling the reactor power in a relatively low power state before the generator is added. On the other hand, in the control mode in which the reactor power is reduced from the operating state, a control rod is inserted into the reactor, and the subcritical control mode in which the reactor power is lowered below the critical level, and the control rod is inserted to the full insertion position. In addition, there is a full control rod insertion mode that shuts down the reactor. In recent years, a plurality of control rods are operated simultaneously in an improved boiling water reactor (ABWR) for the purpose of labor saving and shortening of start / stop time. Further, a reactor power control device that automates these controls has been developed (for example, Patent Documents 1-3).

  The reactor water level during reactor start-up / stop and operation is controlled by a water supply control system. Generally, when the output of the nuclear reactor is 20% to less than 30%, the water supply control system controls the water level to be constant by single element control based only on the reactor water level. When the reactor power is 30% or more, the water level is controlled to be constant by three-element control using the reactor water level, feed water flow rate, and main steam flow rate. Therefore, when the reactor is started / stopped and the reactor is at low power, the reactor water level is normally controlled at a constant level by single element control of the feed water control system.

  By the way, even at the time of low reactor power, steam components are generated mainly in the reactor primary cooling water (inside the reactor) by heat generated from the reactor. The void ratio refers to the vapor volume ratio in the total volume of water and steam. When the void ratio in the core changes, the reactor water level changes depending on the change in the volume of the steam. For example, when the reactor power increases and the void ratio of the core increases, the amount of cooling water pushed out from the core through the gas-liquid separator (separator) outlet to the downcomer region outside the core shroud increases. Therefore, the reactor water level measured by the downcomer rises. On the contrary, in the subcritical control mode in which the reactor is shut down and the control rod full insertion control mode, when the control rod is inserted, neutrons are absorbed by the control rod and the core power is reduced. Therefore, the steam generated in the core is reduced. As a result, the amount of cooling water flowing from the core to the downcomer region is reduced, and the reactor water level is lowered.

  When the power of the reactor is low, the reactor water level is controlled by the single element control function of the feed water control system. The reactor water level is controlled after increasing or decreasing from the target water level. However, even if the control system opens and closes the feed water pump regulating valve, it has a response time until the reactor water level actually increases or decreases. Therefore, a deviation occurs with respect to the target water level. When the reactor water level increases or decreases by about 10 cm from the normal water level, an alarm water level is reached and an alarm is generated. When an alarm occurs, it is necessary to temporarily stop the operation and investigate the cause, which is undesirable in terms of operation management.

  When a plurality of control rods are operated at the same time, the change in output becomes larger than when the control rods are operated one by one, so that the change in water level tends to be larger. Therefore, the technique of Patent Document 4 sets a control upper limit (W1) and a control lower limit (W4) between the high water level alarm level (WU) and the low water level alarm level (WL). And the technique of patent document 4 prevents the control rod operation when the reactor water level reaches one of the two restriction levels when operating the control rod, and suppresses the change in the reactor power, Suppress changes in reactor water level. This technology has been adopted in actual plants, and it has been confirmed that it has the effect of suppressing fluctuations in water level through start / stop operation tests and computer simulations.

Japanese Patent No. 3172653 Japanese Patent No. 3275163 Japanese Patent No. 3372767 Japanese Patent Laid-Open No. 11-153893

  Even if the technology of Patent Documents 1-4 is adopted, during the operation of reducing the reactor power in the startup region where the reactor power is approximately 10% or less of the rated power, compared to the case of higher output than the startup region, Reactor water level fluctuation increases. In some cases, it was found that the reactor water level reached the high water level warning level (WU). Even if the water level high warning level is reached, the reactor power at that time is low. Further, the high water level alarm level has a sufficient margin with respect to the scram water level provided approximately 50 cm above the normal water level in order to protect the turbine. Therefore, there is no safety problem. However, there is a burden such as delaying the operation time due to the temporary interruption of the operation and giving a stress to the operator due to the alarm of the high water level.

  FIG. 2 is a diagram showing the relationship between the reactor water level and control rod operation by the reactor power control device. In FIG. 2, WU is a “water level high” alarm level, and WL is a “water level low” alarm level. W0 is the normal water level of the reactor. W1 is a first limit water level set between the normal water level W0 and the high water level warning level WU. Then, when the reactor water level becomes equal to or higher than the limit water level W1, the control rod operation is blocked. The water level W2 is a first operation permission level set between the water levels W0 and W1. Then, the control rod operation is resumed when the reactor water level returns to the water level W2. W4 is a second limit water level set between the normal water level W0 and the low water level warning level WL. When the reactor water level falls below the limit water level W4, control rod operation is blocked. The water level W3 is a second operation permission level set between the water level W0 and W4. When the reactor water level returns to a water level of W3 or higher, the control rod operation is resumed.

  FIG. 2 shows changes in the reactor water level W in the subcritical control mode for reducing the reactor power and the control rod full insertion mode. According to the above prior art, the control rod driving device inserts the control rod from the time t0 to the time t1, and interrupts the control rod insertion from the time t1 to the time t2. Then, the control rod is inserted again from time t2 to time t5, the insertion is interrupted from time t5 to time t6, and inserted again after time t6.

  FIG. 3 is a simulation result of the control rod insertion amount, the reactor output, the feed water flow rate, and the reactor water level when the control rod insertion operation is performed. This simulation result shows a case where the reactor power is reduced from about 8% of the initial power by the control rod full insertion mode of the reactor power control device based on the above-described conventional technology.

The control rod is inserted in accordance with a predetermined procedure, and always stops at a predetermined position regardless of the reactor water level. As control rods are inserted, reactor power decreases. On the other hand, when the reactor water level falls, the feed water control system increases the feed water flow rate. Conversely, when the reactor water level rises, the feed water control system decreases the feed water flow rate. The water supply control system controls the reactor water level so that it is close to the normal water level. However, after time t _A , the water supply control system decreased the feed water flow rate in response to the reactor water level rise, but the water level rise did not stop. Therefore, the reactor water level at time t _B reaches the first limit water level W1, insertion operation of the control rod is interrupted. Even after that, the water supply flow rate decreased and eventually the reactor water level reached the high water level warning level WU, although it became zero.

  An object of the present invention is to prevent the reactor water level from reaching the high water level warning level even when a plurality of control rods are inserted at the same time at a low output such as the startup region.

  The present invention provides a control rod operation limiter that prevents control rod operation by the control rod driving device when the reactor water level reaches a restriction level set between a target water level and a water level high alarm level, and the water level high alarm level. It has a setting device which makes a setting value or a limit level setting value or both different setting values according to a reactor power level.

  According to the present invention, even if a plurality of control rods are inserted at the same time when the output is low, such as in the startup region, the reactor water level can be prevented from reaching the water level high alarm level.

1 is a configuration diagram of a reactor power control apparatus in Embodiment 1. FIG. It is the schematic diagram which showed the relationship between the reactor water level by conventional technology, and control rod operation. It is the figure which showed the relationship between the control rod insertion operation by a prior art, and the reactor power at that time, feed water flow volume, and a reactor water level in a low output state. It is the figure which showed the relationship between a core enthalpy and a core void ratio. FIG. 3 is a configuration diagram illustrating an example of a setting device 18. FIG. 2 is a configuration diagram illustrating an embodiment of an alarm generation device 40. It is the schematic diagram which showed the relationship between the reactor water level in Example 1, and control rod operation. It is the figure which showed the relationship between the control rod insertion operation by Example 1, and the reactor output at that time, a feed water flow volume, and a reactor water level in a low output state. It is the figure which compared the time change of the core void ratio by Example 1 and a prior art. It is a block diagram of the reactor power control apparatus in Example 2. It is the schematic diagram which showed the relationship between the reactor water level by Example 2, and control rod operation. 1 is an example of a boiling water reactor system.

  The inventors have found that the reason why it is difficult to suppress the rise in the reactor water level when the reactor power is low is due to the following mechanism. When the reactor water level rises, the feed water control system decreases the feed water flow rate. When the water level reaches the first limit water level W1, the control rod insertion operation is stopped. The coolant and feed water coming out of the steam separator are mixed by a downcomer and flow into the reactor core. The feed water temperature is lower than the temperature of the coolant coming out of the steam separator. Therefore, when the feed water flow rate decreases, the temperature of the coolant flowing into the core increases. When the temperature of the coolant flowing into the reactor core increases, steam is likely to be generated, so that the void ratio of the reactor core increases and the coolant flow rate from the steam separator to the downcomer also increases. As a result, the reactor water level rises and the feed water control system further reduces the feed water flow rate. The reactor water level rises due to a positive feedback effect.

  The reason why the positive feedback action does not occur when the reactor power is high will be described with reference to FIG. FIG. 4 is a diagram showing the relationship between the core enthalpy and the core void ratio. The core enthalpy on the horizontal axis represents the energy of the coolant (a combination of steam and water). When the reactor heat output is the same, the higher the coolant temperature at the core inlet, the greater the core enthalpy. The vertical axis represents the core void ratio. As the core enthalpy increases, the core void ratio increases.

When the reactor power is high, the core enthalpy and core void ratio are high. Even if the core enthalpy changes by Δh, the change amount Δα ₂ of the void ratio is very small. On the other hand, when the reactor power is low, the core enthalpy and core void ratio are low. When the core enthalpy changes by the same Δh, the void ratio change Δα ₁ becomes larger than Δα ₂ . For this reason, in the case of a low output, when the coolant temperature at the core inlet rises as the feed water flow rate decreases, the amount of increase in the core void ratio increases. Therefore, a positive feedback phenomenon has occurred.

  Next, in the operation mode of the boiling water reactor (BWR), there are an operation region in which the core performance calculation apparatus monitors the core state, and a start-up region in which the reactor power is low and the monitoring of the core state is not required. The boundary between the start-up region and the operation region differs depending on the plant, but the reactor power is generally set between 5% and 10%. A positive feedback phenomenon occurs in the output region corresponding to the activation region. Therefore, the reactor power control device may change the control rod insertion operation logic in the startup region and the operation region.

  Specifically, when the operation mode is the start-up region and the control mode is the subcritical control mode or the control rod full insertion mode (that is, the control mode in which the control rod is inserted into the core and the reactor power is reduced). The reactor power control device may continue to insert control rods without stopping the control rod insertion operation when the reactor water level rises. When controlled in this way, the reactor power control device inserts the control rod, thereby reducing the reactor power and suppressing the generation of steam. On the other hand, since the temperature of the coolant flowing into the core becomes high, steam is generated. Therefore, the reactor power control apparatus can suppress the generation amount of steam as a whole, suppress the increase in the core void ratio, and as a result, suppress the increase in the reactor water level. A specific example is shown in Example 1.

  FIG. 12 shows the configuration of a boiling water reactor system. The core 60 in the reactor pressure vessel 3 is composed of a plurality of fuel assemblies (not shown). The amount of steam generated in the core 60 is adjusted by the heat output of the core 60. The thermal output of the core 60 can be controlled by changing the flow rate of the coolant flowing through the core, or by adjusting the amount of the control rod 61 containing the neutron absorbing material inserted into the core. As for the core flow rate, the recirculation flow rate control device 63 sends a signal to the built-in recirculation pump 64 installed in the reactor pressure vessel 3 to change the rotational speed of the pump rotor blades. The output controller 1 transmits a command signal for the insertion amount of the control rod 61 into the core to the control rod driving device 2. The control rod drive device 2 inserts or pulls out the control rod 61 from the core 60 by an electric motor or water pressure.

  The reactor pressure vessel 3 is provided with a pressure detector 6, a plurality of neutron detectors 5 installed in the reactor core 60, and a reactor water level meter 4 for measuring the water level of the downcomer portion in the reactor pressure vessel. The main steam pipe 70 is connected to the upper part of the reactor pressure vessel 3 and is connected to the high-pressure turbine 73 and the low-pressure turbine 74. The steam generated in the core 60 in the reactor pressure vessel 3 flows into the main steam pipe 70 and rotates the rotor blades of the high pressure turbine 73 and the low pressure turbine 74. The generator 75 is connected to the low pressure turbine 74, and generates electric power by the shaft rotational force of the high pressure turbine 73 and the low pressure turbine 74. The condenser 76 is connected to the downstream side of the low-pressure turbine 74, and condenses the steam discharged from the low-pressure turbine 74 into water with seawater or the like to reduce the pressure. The water condensed by the condenser 76 is heated by a feed water heater (not shown), pressurized by a feed water pump 77, passes through a feed water flow rate adjustment valve 78, and enters the reactor pressure vessel 3 from a feed water pipe 80. Return to.

  The main steam pipe 70 is provided with a turbine steam flow rate adjusting valve 72 and a bypass pipe for directing steam to the condenser 76. The turbine bypass valve 81 is provided in this bypass pipe. By adjusting the opening degree of the turbine steam flow rate adjusting valve 72 and the turbine bypass valve 81, the turbine steam flow rate can be controlled and the amount of power generation can be controlled. A main steam flow rate detector 71 is installed in the main steam line 70, and a feed water flow rate detector 79 is installed in the water supply line 80. The feed water control device 68 is based on the main steam flow signal 151 output from the main steam flow detector 71, the feed water flow signal 152 output from the feed water flow detector 79, and the reactor water level signal 153 output from the reactor water level meter 4. Then, the control signal 102 of the feed water flow rate adjustment valve 78 is output to control the feed water flow rate so that the reactor water level becomes constant.

  Based on the reactor pressure signal 154 and the generator output signal 155, the pressure control device 21 outputs a control signal 101 for the turbine steam flow rate adjustment valve 72 and a control signal 106 for the turbine bypass valve 81. Further, a signal 103 corresponding to the reactor output as a control target is output to the output controller 1.

  The water level alarm generation device 40 transmits an alarm signal to the output control device 1 based on the reactor water level signal 153.

  The output controller 1 is a main device of the reactor power control apparatus, and is connected to a central control panel 66 that serves as an interface with an operator. The central control panel 66 inputs the operation control mode, the target reactor power change rate, the reached target value, and the like to the output controller 1. The output controller 1 transmits a control signal 104 to the recirculation flow rate control device 63 based on a signal from the central control panel 66, a signal 103 from the pressure control device 21, and the like, and a control signal 105 to the control rod drive device 2. Is output. In addition, the control rod drive device 2 transmits control rod position information 156 and the like to the output control device 1. The central control panel 66 can display control rod position information 156. Then, when the information that the reactor power is excessive is received from the core performance calculation device 65, the power control device 1 temporarily stops the power control or decreases the reactor power.

  FIG. 1 shows an embodiment of a reactor power control apparatus. The output controller 1 receives the control mode signal 51, the target value 52, the target change rate 53, the output signal from the neutron detector 5, and the output signal of the pressure controller 21 </ b> A constituting the pressure control device 21. Here, the control mode signal 51 is a signal representing the type of control mode such as a critical control mode or a subcritical control mode input by the operator. The target value 52 indicates the target pressure in the temperature raising and boosting control mode, and the target reactor output in the reactor power control mode. The target change rate 53 indicates a target temperature change rate in the temperature rising pressure increase control mode and a target output change rate in the reactor output pressure control mode. Then, the output control device 1 outputs a control rod operation signal necessary for controlling the output of the nuclear reactor 3 to the control rod drive device 2. This control rod operation signal changes based on the target change rate 53.

  The output controller 1 transmits a control rod operation signal to the control rod drive device 2 via the operation determination device 9. The pressure detector 6 inputs the main steam pressure of the nuclear reactor 3 to the pressure control device 21. The output signal of the pressure controller 21A corresponds to the total steam flow rate, and can be converted from the total steam flow rate into the heat output.

  The switch 8 outputs a control rod operation signal from the output controller 1 to the control rod operation determiner 9. The control rod operation determination unit 9 outputs a control rod insertion command or a control rod extraction command indicated by the illustrated characteristics to the control rod driving device 2. The control rod driving device 2 inserts or pulls out the control rod in the nuclear reactor 3 in accordance with an input command. The reactor water level meter 4 detects the downcomer water level of the reactor 3 and outputs it to the control rod operation limiter 22 and the water level alarm generator 40.

  The control rod operation limiter 22 transmits an open / close signal to the switch 8 to restrict the operation of the control rod so that the reactor water level does not reach the warning water level. The comparators 13, 14, 15, and 16 receive the reactor water level signal from the reactor water level meter 4 and compare the reactor water level set in the setting devices 17, 18, 19, and 20 with the reactor water level. To do.

  W1 of the setting device 18 is a first limit water level set between the normal water level W0 and the high water level warning level WU. When the water level reaches the limit water level W1 or higher, the control rod operation limiter 22 prevents the control rod operation. The water level W2 of the setting device 20 is a first operation permission level set between the water level W0 and W1. When the water level returns to W2 or lower, the control rod operation limiter 22 resumes the control rod operation. W4 of the setting device 17 is a second limit water level set between the normal water level W0 and the low water level warning level WL. When the water level becomes lower than the limit water level W4, the control rod operation limiter 22 prevents the control rod operation. The water level W3 of the setting device 19 is a second operation permission level set between the water level W0 and W4. When the water level returns to W3 or higher, the control rod operation limiter 22 restarts the control rod operation.

  If the reactor water level is W, the comparator 13 outputs a logic “1” when W <W4, and the comparator 14 outputs a logic “1” when W> W1. The comparator 15 outputs a logic “1” when W> W3, and the comparator 16 outputs a logic “1” when W <W2. Comparators 13 and 14 output an output signal to the OR gate 11, and comparators 15 and 16 output an output signal to the AND gate 12. The output signal of the OR gate 11 becomes a set signal of the flip-flop (F / F) circuit 10, and the output signal of the AND gate 12 becomes a reset signal of the F / F circuit 10. The F / F circuit 10 opens the switch 8 when a set signal is input (when the logic is “1”), and switches when the reset signal is input (when the logic is “0”). 8 is closed. When the reset signal is input, the F / F circuit 10 holds the output signal until the set signal is input. Conversely, when the set signal is input, the F / F circuit 10 holds the output signal until the reset signal is input. . That is, when the reactor water level W becomes W1 or higher, or when W becomes W4 or lower, a set signal is input to the F / F circuit 10, and the F / F circuit 10 opens the switch 8. When the reactor water level W is W3 or higher and W2 or lower, a reset signal is input to the F / F circuit 10, and the F / F circuit 10 closes the switch 8.

  When the switch 8 is in the closed state, the control rod driving device 2 operates the control rod according to the control rod operation signal output from the output controller 1. When the reactor water level changes and approaches the warning water level and reaches the limit level, the OR gate 11 outputs a set signal to the F / F circuit 10 and the F / F circuit 10 opens the switch 8. As a result, the control rod driving device 2 stops the control rod operation without transmitting a control rod operation signal from the output controller 1. Thereafter, the water supply control system restores the reactor water level to the normal water level, and the AND gate 12 outputs a reset signal to the F / F circuit 10. The F / F circuit 10 closes the switch 8 and restarts the control rod operation.

  In the present embodiment, the setting device 20 that sets the operation permission level W2, the setting device 19 that sets the operation permission level W3, and the setting device 17 that sets the limit water level W4 always output one set value. The setter 18 that sets the limit water level W1 has a function of changing the set value of the limit water level depending on the control mode and the operation mode.

  FIG. 5 is a configuration diagram showing an embodiment of the setting device 18. The setter 18 receives a control mode and an operation mode. The setter 18 outputs a logic “1” when the control mode is a mode for reducing the reactor power and the operation mode is the startup region. For example, when the control modes for reducing the reactor power are only the subcritical control mode and the control rod full insertion mode, the OR gate 35 determines the control mode for reducing the reactor power. The AND gate 36 receives the operation mode signal and the signal output from the OR gate 35.

  When the output signal from the AND gate 36 is true (logic “1”), the setter 18 outputs a preset setting value W1-B. In addition, when the output signal from the AND gate 36 is false (logic “0”), the setter 18 transmits an output signal with the logic “1” from the knot gate 37, and the set value W 1 -A previously given. Is output. The set value W1-B is larger than the set value W1-A, and a set value is set so as not to prevent the control rod insertion operation in the activation area.

  In this embodiment, an operation mode signal such as a start area or an operation area is input. However, instead of the operation mode signal, the pressure controller 21A calculates the reactor output from the total steam flow rate and outputs it to the AND gate 36. When the reactor output is in the range corresponding to the startup region, the AND gate 36 It can also be configured to output a logic “1” signal. Further, the output level for switching the set value W1 can be set to an output level different from the output level for distinguishing the startup region and the operation region.

  The water level alarm generating device 40 outputs an alarm signal when the downcomer water level of the reactor 3 detected by the reactor water level gauge 4 falls below the water level low warning level WL or above the water level high warning level WU. Output to 1. When the alarm signal is logic “1”, the output controller 1 sets the output signal to zero and stops the automatic control rod operation by the output control device.

  FIG. 6 is a configuration diagram showing an embodiment of the water level alarm generator 40. The reactor water level signal of the reactor water level meter 4 is input to the comparators 43 and 44. The comparators 43 and 44 compare the reactor water level with the reactor water level set by the setting devices 41 and 42. The water level alarm generating device 40 generates a water level high alarm signal when the water level W is higher than the water level high alarm set value WU, and outputs the water level low alarm signal when the water level W is lower than the water level low alarm set value WL. Send to. The setter 42 always outputs one value. On the other hand, the setting device 41 outputs two types of set values according to the operation mode and the control mode. That is, the setter 41 outputs a preset set value WU-B when the control mode is a mode for reducing the reactor power and the operation mode is the start-up region, and is set in advance otherwise. The given set value WU-A is output. The set value WU-B is larger than the set value WU-A.

  In the present embodiment, only the setting device 41 is configured to change the output of the set value according to the operation mode and the control mode. However, the setting device 42 can also have the same configuration as the setting device 41. Also, the water level high alarm set value WU can be switched according to the output level using a signal corresponding to the reactor power level instead of switching according to the operation mode (startup region and operation region).

  Next, the relationship between the reactor water level and the control rod operation according to this embodiment will be described with reference to FIG. The left diagram of FIG. 7 shows the control rod operation characteristics when the control rod insertion operation is performed according to this embodiment in an operation region where the reactor power is relatively large. WU-A is a high water level warning level for the operation region, WL is a low water level warning level, and W0 is a normal water level of the reactor. W1-A is a first limit water level set between the normal water level W0 and the high water level warning level WU-A. When the limit water level W1 or higher is reached, the control rod operation limiter 22 prevents control rod operation. The water level W2 is a first operation permission level set between the water level W0 and W1-A. When the water level returns to W2 or lower, the control rod operation limiter 22 resumes the control rod operation. W4 is a second limit water level set between the normal water level W0 and the low water level warning level WL. When the water level becomes lower than the limit water level W4, the control rod operation limiter 22 prevents the control rod operation. The water level W3 is a second operation permission level set between the water level W0 and W4. When the water level returns to W3 or higher, the control rod operation limiter 22 resumes the control rod operation. When the reactor water level W in the operation region changes as shown in FIG. 7 in the subcritical control mode or the control rod full insertion mode in which the reactor power is reduced, the control rod operation limiter 22 controls between time t8 and time t9. A rod is inserted, and the control rod insertion operation is interrupted between time t9 and time t10. Then, the control rod operation limiter 22 inserts the control rod again between time t10 and time t11.

  The right diagram of FIG. 7 shows the control rod operation characteristics when the control rod insertion operation is performed as in the present embodiment in a startup region where the reactor power is relatively small. The setting device 41 sets the water level high alarm level WU-B in the start-up area, which is higher than the water level high alarm level WU-A in the operation area. Moreover, the setting device 18 sets the 1st limit water level W1-B in a starting area | region whose level is higher than the 1st limit water level W1-A in an operation area | region. In the subcritical control mode in which the reactor power is reduced or the control rod full insertion mode, when the change in the reactor water level W in the startup region is as shown in the right diagram of FIG. 7, the control rod driving device 2 starts from time t12. The control rod is always inserted during time t14. At this time, at time t13, the reactor water level W reaches the water level W1-A at which the control rod insertion operation is interrupted in the operation region. However, in the activation region, the setting device 18 sets the water level at which the control rod insertion operation is interrupted to W1-B. Therefore, the control rod drive device 2 continues to execute the control rod insertion operation.

  Even in the start-up region, the critical control mode for increasing the reactor power by pulling out the control rod, the temperature rise / boost control mode, and the reactor power control mode are not shown in the right diagram of FIG. Output control is performed using the limit value.

  FIG. 8 shows the simulation results of the control rod insertion amount, the reactor output, the feed water flow rate, and the reactor water level when the control rod insertion operation is performed. This simulation result shows a case where the reactor power is reduced from about 8% of the initial power by the control rod full insertion mode of the reactor power control apparatus based on the present embodiment. The control rod is inserted in accordance with a predetermined procedure, and always stops at a predetermined position regardless of the reactor water level. As control rods are inserted, reactor power decreases. On the other hand, when the reactor water level decreases, the feed water control system increases the feed water flow rate. Conversely, when the reactor water level rises, the feed water control system decreases the feed water flow rate. Therefore, the water supply control system controls the reactor water level so that it is close to the normal water level. According to this embodiment, the control rod insertion is continued even when the water level becomes high. In that case, the rise in the water level of the nuclear reactor is suppressed. Since the water level high alarm level WU-B is larger than WU-A, it is above the graph and is not shown. According to the calculation result, there was an effect that the reactor water level does not reach the water level high warning level WU-A in the operation region.

  The water level alarm generating device 40 in the present embodiment uses different set values depending on the operation mode and the control mode. However, from the result of FIG. 8, it is possible to use one set value regardless of the operation mode or the control mode.

FIG. 9 is a simulation calculation result showing how the core average void ratio changes with time when the prior art shown in FIG. 3 and the present embodiment shown in FIG. 8 are used. In the prior art, since the control rod insertion operation is stopped at time t _B , a decrease in the reactor power is suppressed, and the core void ratio increases. As a result, the reactor water level rose. On the other hand, in this embodiment, since the control rod insertion operation is continued after time t _B , the reactor power decreases and the core void ratio continues to decrease. As a result, the rise of the reactor water level is suppressed.

  A control rod operation limiter that prevents control rod operation by the control rod drive when the reactor water level reaches the limit level set between the target water level and the water level high alarm level, and the water level high alarm level set value or limit level set value Alternatively, by having a setter that sets both of them to different set values depending on the reactor power level, even if a plurality of control rods are inserted at the same time when the reactor power is about 10% or less of the rated power, It is possible to prevent the reactor water level from reaching the water level high warning level, thereby shortening the plant shutdown time and reducing the burden on the operator when the water level high warning occurs. Furthermore, in this embodiment, it is possible to change the low water level alarm level or the second limit water level.

  In this embodiment, the control rod operation limiter 22 is configured independently of the output controller 1. However, the control rod operation limiter 22 can be incorporated into the output controller 1.

  FIG. 10 shows an embodiment of the reactor power control apparatus. The difference between FIG. 10 and FIG. 1 is a control rod operation limiter 26. The control rod operation limiter 26 includes a setter 28 for setting the limit water level W1. And this setting device 28 always outputs one value like the other setting devices 17, 19, and 20. The comparator 14 compares the reactor water level W1 set in the setting device 28 with the reactor water level signal W of the reactor water level meter 4, and outputs a logic “1” signal when W> W1.

  The comparator 13 and the comparator 14 are connected to the OR gate 11 as in the embodiment of FIG. Unlike the embodiment of FIG. 1, a switch 30 is installed between the comparator 14 and the OR gate 11. The switch 30 is turned off when the control mode is the subcritical control mode or the control rod full insertion mode and the operation mode is in the startup region, and is turned on in other conditions. When the switch 8 is on, the comparator 14 outputs a logic signal “1” or “0” to the OR gate 11. When the switch 8 is off, the comparator 14 outputs a logic signal “0” to the OR gate 11. That is, the control rod operation limiter 26 corresponds to not setting the effective first limit water level W1 when the control mode is the subcritical control mode or the control rod full insertion mode and the operation mode is the startup region. However, even if the reactor water level increases, the logic does not stop the control rod operation.

  The left figure of FIG. 11 shows the control rod operation characteristics when the control rod insertion operation is performed according to this embodiment in an operation region where the reactor power is relatively large. WU is the high water level warning level, WL is the low water level warning level, and W0 is the normal water level of the reactor. W1 is a first limit water level set between the normal water level W0 and the high water level warning level WU. The control rod operation limiter 26 prevents the control rod operation when the water level reaches the limit water level W1 or higher. The water level W2 is a first operation permission level set between the water levels W0 and W1. When the water level returns to W2 or lower, the control rod operation limiter 26 resumes control rod operation. W4 is a second limit water level set between the normal water level W0 and the low water level warning level WL. The control rod operation limiter 26 prevents the control rod operation when the water level becomes lower than the limit water level W4. The water level W3 is a second operation permission level set between the water level W0 and W4. When the water level returns to W3 or higher, the control rod operation limiter 26 resumes control rod operation. In the subcritical control mode or the control rod full insertion mode, in the operation region, the control rod driving device 2 inserts the control rod from the time t15 to the time t16, and the control rod insertion operation from the time t16 to the time t17. Interrupt. The control rod is inserted again from time t17 to time t18.

  The right figure of FIG. 11 shows the control rod operation characteristics when the control rod insertion operation is performed according to the present embodiment in a relatively small start-up region of the reactor power. In the subcritical control mode and the control rod full insertion mode, the control rod drive device 2 always inserts the control rod between time t19 and time t21. During this time, the reactor water level W reaches the water level W1 at time t20. However, the control rod operation limiter 26 is logic that does not interrupt the control rod insertion operation in the activation area. Therefore, the control rod driving device 2 continues to execute the control rod insertion operation.

  In this embodiment, it is only necessary to install the switch 30 in the control rod operation limiter 26 and add an algorithm for operating the switch 30. Therefore, there exists an advantage which can be changed easily from the prior art of patent document 4. FIG.

  1 and FIG. 10, the control mode signals such as the subcritical control mode and the control rod full insertion mode are inputted to the control rod operation limiters 22 and 26. However, when a plurality of control rod operation limiters corresponding to each control mode are prepared, it is not necessary to input the control mode. In that case, an operation mode signal indicating the start-up region or the operation region, or a reactor output signal capable of determining the operation mode may be input to the control rod operation limiter. Therefore, the OR gates 32 and 35 in FIG. 5 and FIG. The gates 31 and 36 are unnecessary.

  In any of the embodiments, when the operation of raising the reactor power is performed or when the reactor water level fluctuates greatly when the reactor power level is relatively high, the control rod drive limiter temporarily stops the control rod operation and Promote the stabilization of On the other hand, in the operation of shutting down the reactor in the low power state, the control rod drive limiter does not restrict the control rod insertion operation, thereby mitigating the rise in water level caused by the decrease in the feed water flow rate. Therefore, the control rod driving device can be operated so that the reactor water level does not reach the water level high alarm point.

DESCRIPTION OF SYMBOLS 1 Output controller 2 Control rod drive device 4 Reactor water level meter 5 Neutron detector 6 Pressure detector 8, 30 Switch 13, 14, 15, 16 Comparator 17, 18, 19, 20, 28 Setter 21 Pressure control device 22, 26 Control rod operation limiter 40 Water level alarm generating device 60 Core 63 Recirculation flow rate control device 65 Performance calculation device 66 Central control panel 71 Main steam flow rate detectors 73, 74 Turbine 75 Generator 79 Feed water flow rate detector WU Water level high Alarm level W1 First limit water level W2 First operation permission water level W0 Normal water level W3 Second limit water level W4 Second operation permission water level WL Water level low alarm level WU-A Operation level water level high alarm Level WU-B Water level high alarm level W1-A in the operation region First limit water level level in the operation region W1-B First limit water level in the operation region

Claims (2)

The reactor water supply is controlled such that the reactor water level becomes the target water level, the reactor whose output is controlled by the operation of the control rod, the output controller that outputs the control rod operation signal for controlling the output of the reactor, and In a reactor power control device comprising a control rod drive device that receives a control rod operation signal and operates one or more control rods simultaneously,
A control rod operation limiter that prevents control rod operation by the control rod driving device when the reactor water level reaches a restriction level set between a target water level level and a water level high alarm level; limit level setting value or both thereof have a setting device for a different set value according to the reactor power level,
When the setting device is an operation operation for reducing the reactor power and the operation mode is a start-up region where the reactor power is low, the water level high alarm level set value and / or the limit level set value are both in the operation region. Reactor power control device characterized in that the water level set value is higher than the water level set value 2. The reactor power control apparatus according to claim 1, wherein the setter has the water level high alarm level setting value and / or the limit level setting value set between 5% and 10% of the reactor power. A reactor power control apparatus characterized in that a set value of the start-up region is set higher than a set value of the operation region in a start-up region lower than the boundary and an operation region where the reactor power is larger than that .

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