Reactor output control device and reactor output control method

Abstract

To provide a reactor output control device that can accurately control output from a reactor.SOLUTION: A reactor output control device comprises: a reactivity calculation unit that calculates reactivity from a neutron flux; and a first operation unit that calculates a temperature reactivity coefficient and delay time of temperature measurement from the reactivity and reactor water temperature. The reactor output control device further comprises a second operation device that calculates a temperature change rate from a change of the reactor water temperature, and calculates and outputs a target neutron flux corresponding to a target temperature change rate on the basis of a neutron flux going back to the past by the delay time. The reactor output control device further comprises a control rod control operation unit that sets the output target neutron flux.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reactor power control device and a method for controlling the power of a nuclear reactor. [Background technology]

[0002] When starting up a nuclear reactor, many control rods inserted in the reactor are withdrawn to increase the amount of neutrons generated by nuclear fission. At this time, the operation of withdrawing the control rods is a heavy burden. For this reason, recent boiling water reactors automate the operation of the control rods from start-up to reaching the rated power output. In addition, in the heating and pressurizing process at the start-up of a boiling water reactor, the temperature of the reactor water is changed by controlling the operation of the control rods. In this method, the value of the neutron flux is changed by operating the control rods to control the temperature change rate of the reactor water to a target value. However, due to various factors, a delay occurs between the operation of the control rods and the measurement of the change in the temperature change rate. For this reason, it is difficult to maintain the reactor water temperature change rate at the target value even if the control rods are simply operated based on the measured value of the reactor water temperature change rate. In view of this, focusing on the relationship between neutron flux and the rate of change of reactor water temperature, a reactor power control method has been proposed in which the operation of the control rods is controlled (see, for example, Patent Documents 1, 2 and 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-145895 [Patent Document 2] JP 2005-207944 A [Patent Document 3] JP 2005-241384 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the response time delay between the neutron flux and the rate of change of temperature is affected by, for example, the time required for heat transfer from the fuel rods to the coolant in the core, the time required for flow from the core to the temperature measurement point, and the delay time due to measuring instruments such as the heat capacity of the thermocouple that measures the reactor water temperature. Thus, the response time delay between the neutron flux and the rate of change of temperature varies depending on the design of the fuel and the configuration of the measuring system. For this reason, it is difficult to accurately control the power output of the reactor by simply controlling the operation of the control rods while paying attention to the above-mentioned relationship between the neutron flux and the rate of change of the reactor water temperature.

[0005] In order to solve the above problems, the present invention provides a reactor power control device and a reactor power control method capable of controlling the power of a reactor with high accuracy.

[0006] The above and other objects of the present invention and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0007] The reactor power control device of the present invention includes a reactivity calculation unit that calculates reactivity from neutron flux, and a first calculation unit that calculates a temperature reactivity coefficient and a temperature measurement delay time from reactivity and reactor water temperature. The reactor power control device also includes a second calculation unit that calculates a temperature change rate from changes in reactor water temperature, and calculates and outputs a target neutron flux corresponding to the target temperature change rate based on the temperature change rate, the temperature measurement delay time, and the neutron flux going back in time by the delay time. The reactor power control device also includes a control rod control calculation unit that sets the output target neutron flux.

[0008] The reactor power control method of the present invention calculates reactivity from neutron flux, calculates a temperature reactivity coefficient from reactivity and reactor water temperature and a delay time of temperature measurement, and calculates a temperature change rate from a change in reactor water temperature. The reactor power control method also calculates a ratio A of the neutron flux and the temperature change rate based on the neutron flux, the temperature change rate, and the delay time, and calculates a target neutron flux corresponding to the target temperature change rate. Furthermore, the reactor power control method controls the withdrawal and insertion of control rods so that the neutron flux coincides with the target neutron flux. Effect of the Invention

[0009] According to the present invention, it is possible to provide a reactor power control device and a reactor power control method capable of controlling the power of a reactor with high accuracy.

[0010] Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram showing a schematic configuration of a reactor power control device according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing a configuration of a first calculation unit of the reactor power control device. [Diagram 3] 1 is a graph showing a calculation of a delay time between reactivity and reactor water temperature. [Figure 4] FIG. 2 is a diagram showing a configuration of a second calculation unit of the reactor power control device. [Diagram 5] FIG. 1 is a conceptual diagram showing a method for calculating the ratio of neutron flux to temperature change rate. [Figure 6] FIG. 13 is a diagram showing an example of a target neutron flux and past, present, and future predicted neutron flux values ​​displayed on a display device. [Figure 7] FIG. 1 is a diagram showing a schematic configuration of a reactor power control device according to a second embodiment. [Figure 8] FIG. 2 is a diagram showing a configuration of a third calculation unit of the reactor power control device. [Figure 9] 2 is a flowchart of a reactor power control method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An example of a reactor power control device and a reactor power control method according to an embodiment of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following example. In each of the drawings described below, the same reference numerals are used for common members. In addition, in the drawings used in this specification, the same reference numerals are used for the same or corresponding components, and repeated description of these components may be omitted.

[0013] 1. Overview of the Invention Before describing the embodiments of the present invention, an overview of the present invention will be described. As described in the Background Art section, the control rod operation is automated from the start-up of the reactor until the rated power is reached. This allows the reactor operator to monitor the power control of the reactor at a higher level.

[0014] After a nuclear reactor goes critical, the period until it reaches the rated pressure is called the heating and pressurization process. During this process, the control rods inserted into the core are successively withdrawn without steam flowing out of the reactor, to control the neutron flux to an appropriate level. Then, the heat generated by nuclear fission in the fuel is used to raise the temperature and pressure of the cooling water in the reactor.

[0015] During the heating and pressurization process, it is desirable to avoid thermal shock to the components that make up the reactor. For this reason, the temperature change rate of the reactor water must be kept below a limit value (usually 55°C / h) during the heating and pressurization process. Therefore, when controlling the operation of the control rods during the heating and pressurization process, a target value that keeps the temperature change rate below the limit value is set as the target temperature change rate. The control rods are then controlled based on the deviation between the reactor water temperature change rate and the target temperature change rate.

[0016] In control based on the deviation between the reactor water temperature change rate and the target temperature change rate, the neutron flux value changes immediately in response to the operation of the control rod. However, from the change in neutron flux caused by the operation of the control rod to the measurement of the change in the temperature change rate, there are delay times, such as the heat transfer time from the fuel rod to the coolant in the core and the flow time from the core to the temperature measurement point. In addition, there are delay times due to measuring instruments such as the heat capacity of the thermocouple that measures the reactor water temperature, and delay times due to the time averaging operation for calculating the temperature change rate from the measured temperature. These delay times are on the order of several minutes. Therefore, even if the control rod is operated simply based on the deviation between the reactor water temperature change rate and the target temperature change rate, the operation of the control rod is delayed due to the above delay times, making it difficult to maintain the reactor water temperature change rate at the target value.

[0017] Therefore, the method described in the above-mentioned Patent Document 1 calculates the ratio α of the neutron flux and the temperature change rate using the detected values ​​of the neutron flux and the temperature change rate. Specifically, during the transition from the critical process to the heating and pressure increase process, the maximum value of the neutron flux in the reactor and the maximum value of the reactor water temperature change rate are detected. Then, the detected maximum value of the neutron flux in the reactor (φ max ) and the maximum value of the reactor water temperature change rate (T max ) is used to calculate the ratio α using equation (1) (Q l o ss (is approximated to zero). The neutron flux target value for bringing the rate of change of the reactor water temperature closer to the target value is then calculated from the calculated α, and the control rod operation is controlled according to this neutron flux target value.

[0018]

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[0019] φ max : The first neutron flux maximum occurring in the early post-critical stage dT max / dt: First maximum value of reactor water temperature change rate M: Effective mass of cooling water C v : Specific heat of the coolant Q loss: Heat loss to outside the reactor (approximately zero) α: Conversion factor from neutron flux to heat generation

[0020] The method using the above formula (1) assumes that the temperature reactivity coefficient of the reactor water is negative. When the temperature reactivity coefficient is negative, a negative reactivity is applied to the reactor core when the reactor water temperature rises. Then, the increase in neutron flux slows down, and eventually the neutron flux starts to decrease. This results in the formation of a maximum value of the neutron flux and a maximum value of the rate of change of the reactor water temperature.

[0021] However, recent boiling water reactor fuel has been designed to have a higher fuel enrichment and burn up, improving fuel economy. In high burn up fuel, the volume of the water region relative to the fuel volume is increased in order to burn the fuel efficiently. When such fuel is used, the temperature reactivity coefficient of the reactor water may become positive if the reactor water temperature is low. When the temperature reactivity coefficient of the reactor water becomes positive, a positive reactivity is applied when the neutron flux increases and the reactor water temperature rises. Therefore, an increase in the reactor water temperature increases the rate of rise of neutrons, and also increases the rate of change of the reactor water temperature. In this way, when the temperature reactivity coefficient of the reactor water is positive, the maximum value of the neutron flux and the maximum value of the reactor water temperature change rate are not formed, so that the control rod operation using the above equation (1) cannot be controlled.

[0022] Finally, even with high burnup fuel, the temperature reactivity coefficient becomes negative as the temperature approaches normal operating temperature. Furthermore, gas bubbles are generated in the reactor water, imposing negative void reactivity. Therefore, the increase in neutron flux stops automatically even if the operator does not insert the control rods. However, the reactor water temperature increases during the period until the operation stops. Therefore, unless the control rods are inserted, the rate of change of the reactor water temperature may exceed the temperature change rate limit value.

[0023] In contrast, the method described in the above-mentioned Patent Document 2 inserts control rods on the condition that the reactor water temperature change rate is equal to or greater than a set value and the detected neutron flux is on an increasing trend. This control inserts control rods when the reactor water temperature change rate and neutron flux increase, even if the temperature reactivity coefficient of the reactor water becomes positive.

[0024] Moreover, the technique described in the above-mentioned Patent Document 3 calculates a neutron flux limit value from the reactor water temperature change rate, the reactor water temperature change rate limit value, and the detected neutron flux at a certain time, and operates the control rods. This technique calculates the reactor water temperature change rate at a certain time. Then, the neutron flux limit value is calculated based on the calculated reactor water temperature change rate, the reactor water temperature change rate limit value that is preset as an upper limit value for the reactor water temperature change rate, and the neutron flux detected at a certain time before the certain time. Then, the detected neutron flux is compared with the calculated neutron flux limit value to control the operation of the control rods.

[0025] However, as mentioned above, the response time delay between the neutron flux and the rate of temperature change may change due to changes in the fuel design or the measurement system. For example, if the delay time used to calculate the ratio between temperature change and neutron flux is off by 1 minute from the original value, and the period of neutron flux increase after criticality (the time it takes for the neutron flux to increase to 2.71 times) is assumed to be 150 seconds. In this case, the neutron flux will be about 1.5 times (or about 1 / 1.5) of the original value. That is, in the method described in Patent Document 3, the evaluation of the delay time used to calculate the ratio between the temperature change and the neutron flux (a certain time ago) may not be appropriate. If the evaluation of this delay time is inappropriate, the neutron flux cannot be controlled with high precision. For this reason, the method described in Patent Document 3 is effective when used with a sufficient margin as a safety function. However, the method described in Patent Document 3 is not suitable for high-precision control.

[0026] Therefore, for highly accurate control, it is necessary to properly evaluate the delay time when calculating the ratio between the temperature change and the neutron flux (a certain time before). For this purpose, it is necessary to evaluate the delay time based on the value measured in the actual device.

[0027] In order to evaluate the delay time, the method described in the above-mentioned Patent Document 1 uses the characteristics of the time series data of the maximum value of the neutron flux and the maximum value of the temperature change rate to find the corresponding delay time. However, when the temperature reactivity coefficient is positive, such a maximum value may not be obtained. Therefore, even when the temperature reactivity coefficient is positive, it is necessary to have characteristics of the time series data that can find the delay time by associating the neutron flux with the temperature change rate, or the neutron flux with the temperature itself.

[0028] One way to obtain such features on time series data is to use the reactivity calculated from the neutron flux. The reactivity is obtained by solving an inverse time equation using the measured neutron flux as input. This reactivity has a small lag with respect to the neutron flux. In addition, the reactivity is expected to be proportional to the reactor water temperature during the heating and pressurization process when no voids are generated in the moderator. In other words, by comparing the proportional reactivity and reactor water temperature, the delay time of the temperature change rate can be evaluated from the neutron flux.

[0029] Therefore, the reactor power control device and the reactor power control method of the present invention evaluate the response delay time between neutron flux and temperature based on values ​​measured in an actual plant. Then, the ratio between neutron flux and temperature change rate is calculated taking the delay time into consideration. This makes it possible to accurately determine a target neutron flux corresponding to a target temperature change rate. As a result, by controlling the operation of the control rods according to this neutron flux target value, the reactor power can be accurately controlled.

[0030] 2. First embodiment of reactor power control device A first embodiment of the reactor power control device will be described. Fig. 1 shows a schematic configuration of the reactor power control device. Fig. 1 also shows a reactor power control device 50 and the configuration of a main part of a boiling water reactor controlled by the reactor power control device 50.

[0031] The pressure vessel 1 of a boiling water reactor holds a reactor core 2 therein. A plurality of control rods 3 (only one is shown in FIG. 1 ) are attached to the reactor core 2 in a structure that allows them to be inserted and removed. The control rods 3 are connected to a control rod drive mechanism 4. The control rod drive mechanism 4 operates the control rods 3 to withdraw the control rods 3 from the reactor core 2 and insert them into the reactor core 2. The operation of the control rod 3 by the control rod drive device 4 is controlled by a control rod drive control unit 5. The control rod drive control unit 5 is connected to a control rod control calculation unit 6 of a reactor power control device 50. The control rod drive control unit 5 receives operation instructions for withdrawing the control rod 3 and inserting the control rod 3 from the control rod control calculation unit 6. Then, the control rod drive control unit 5 outputs operation instructions for the control rod 3 to the control rod drive device 4.

[0032] Furthermore, the core 2 is equipped therein with a plurality of neutron detectors 7 (only one is shown in FIG. 1). The neutron detector 7 is connected to a power monitoring device 8. The neutron detector 7 measures the neutron flux per unit time and outputs the result to the power monitoring device 8. The power monitoring device 8 is connected to the control rod control calculation unit 6 and the reactivity calculation unit 9 of the reactor power control device 50. The power monitoring device 8 receives a signal from the neutron detector 7 and calculates neutron flux data. Then, the power monitoring device 8 outputs the calculated neutron flux data to the control rod control calculation unit 6 and the reactivity calculation unit 9. Moreover, the power monitoring device 8 is connected to a memory 10 of the reactor power control device 50. The power monitoring device 8 stores in the memory 10 neutron flux data for a predetermined period of time.

[0033] The reactor pressure vessel 1 is equipped with a temperature detector 11 at the bottom (near the inlet of the reactor water purification system piping). The temperature detector 11 is connected to a temperature monitoring device 12. The temperature monitoring device 12 measures the reactor water temperature using the temperature detector 11. The temperature monitoring device 12 is connected to a memory 10 of the reactor power control device 50. The temperature monitoring device 12 stores temperature data for a predetermined length of time in the memory 10.

[0034] [Reactor power control device] Next, there will be described the configuration of the reactor power control device 50. The reactor power control device 50 includes a memory 10, a reactivity calculation unit 9, a first calculation unit 13, a second calculation unit 14, a control rod control calculation unit 6, and a display device 15.

[0035] The reactor power control device 50 is configured by a known arithmetic device. For example, the reactor power control device 50 is configured by a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a storage unit, and the like. The CPU reads out program codes of software related to various processes of reactor power control stored in a ROM (an example of a recording medium) and expands them in the RAM. Then, the CPU performs reactor power control according to the expanded program. Note that the reactor power control device 50 may include another arithmetic device, such as an MPU (Micro Processing Unit), as the arithmetic unit, instead of the CPU. The storage unit is an example of a recording medium made of a non-volatile storage, etc. The storage unit stores various processing programs executed by the CPU, programs such as the OS, information on the functions of the reactor power control device 50 required to execute the programs, various data tables used by each calculation unit for calculation, etc. The storage unit is, for example, a hard disk drive (HDD), a solid state drive (SSD), a magnetic tape, etc.

[0036] The memory 10 is configured, for example, by the storage unit and RAM. The memory 10 stores neutron flux data calculated by the power monitoring device 8. The memory 10 also stores temperature data measured by the temperature monitoring device 12. The memory 10 also stores reactivity data calculated by the reactivity calculation unit 9. The memory 10 stores a target temperature change rate (dT / dt) to be controlled together with various data to be stored. T and the target temperature change rate (dT / dt) for control switching judgment, which will be described later. T Temperature change rate dT / dt(t n ) ratio B and coefficient D are stored. Target temperature change rate (dT / dt) T The operator stores the ratio B, the coefficient D, etc. in the memory 10 from an external input device or the like.

[0037] The reactivity calculation unit 9 is connected to the power monitoring device 8 and the memory 10. The reactivity calculation unit 9 calculates reactivity data based on the neutron flux data calculated by the power monitoring device 8. The reactivity calculation unit 9 calculates the reactivity data, for example, every time a predetermined time has elapsed. Then, the reactivity calculation unit 9 stores the reactivity data calculated for each elapsed time in the memory 10 together with the elapsed time.

[0038] The first calculation unit 13 is connected to the memory 10 and the second calculation unit 14. The first calculation unit 13 acquires reactivity data and temperature data from the memory 10. The first calculation unit 13 calculates a delay time and a temperature reactivity coefficient based on the reactivity data and the temperature data. Then, the first calculation unit 13 outputs the calculated delay time and temperature reactivity coefficient to the second calculation unit 14.

[0039] The second calculation unit 14 is connected to the memory 10, the first calculation unit 13, and the control rod control calculation unit 6. The second calculation unit 14 acquires neutron flux data and temperature data from the memory 10. Then, the second calculation unit 14 calculates the temperature change rate from the change in reactor water temperature. The second calculation unit 14 also acquires the delay time and the temperature reactivity coefficient from the first calculation unit 13. Then, the second calculation unit 14 calculates a target neutron flux corresponding to a target temperature change rate, based on the calculated temperature change rate and neutron flux data going back by the delay time. Furthermore, the second calculation unit 14 outputs the calculated target neutron flux and the temperature reactivity coefficient used in calculating the target neutron flux to the control rod control calculation unit 6.

[0040] The control rod control calculation unit 6 is connected to the second calculation unit 14, the display device 15, the power monitoring device 8, and the control rod drive control unit 5. The control rod control calculation unit 6 sets a target neutron flux obtained from the second calculation unit 14. Then, the control rod control calculation unit 6 compares the current neutron flux obtained from the power monitoring device 8 with the set target neutron flux to determine the operation of withdrawal and insertion of the control rod 3. Then, based on the determined operation of the control rod 3, the control rod control calculation unit 6 outputs an operation instruction for withdrawal and insertion of the control rod 3 to the control rod drive control unit 5. The control rod control calculation unit 6 repeats the operation instruction for withdrawal and insertion of the control rod 3 until the target temperature is reached.

[0041] The control rod control calculation unit 6 also calculates a predicted value of the future neutron flux from the current reactivity, temperature reactivity coefficient, and current neutron flux, and outputs the calculated future predicted value of the neutron flux, the target neutron flux, and the past and current neutron fluxes to the display device 15.

[0042] The display device 15 includes a display unit such as an LCD (Liquid Crystal Display), and displays various screens on the display unit according to instructions of a display signal input from the control rod control calculation unit 6 . The display device 15 is connected to the control rod control calculation unit 6. In accordance with the instruction of a display signal input from the control rod control calculation unit 6, the display device 15 displays on the display unit the future predicted value of the neutron flux, the target neutron flux, and the past and present neutron fluxes.

[0043] [Output control processing] Next, the details of the processing contents of the reactivity calculation unit 9, the first calculation unit 13, the second calculation unit 14, and the control rod control calculation unit 6, which are the calculation units of the reactor power control device 50, will be described. First, in a boiling water reactor, after reaching criticality, the period is adjusted to be between about 100 and 200 seconds to increase the neutron flux. In this state of the reactor, the control rod control calculation unit 6 starts controlling the operation of the control rods 3. First, the power monitoring device 8 takes in the neutron flux measured by the neutron detector 7 at a fixed period (e.g., 100 ms). Then, the power monitoring device 8 calculates neutron flux data based on the neutron flux measured by the neutron detector 7. Furthermore, the power monitoring device 8 outputs the calculated neutron flux data and the time to the reactivity calculation unit 9. The power monitoring device 8 also stores the calculated neutron flux data and the time in the memory 10.

[0044] [Reactivity calculation section] The reactivity calculation unit 9 acquires time series data that corresponds the neutron flux data calculated by the power monitoring device 8 to the time when the neutron flux data was measured. After acquiring the time series data of the neutron flux, the reactivity calculation unit 9 calculates the reactivity ρ from the neutron flux n according to the inverse time equations of Equations (2) and (3).

[0045]

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[0046]

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[0047] ρ(t): Reactivity at time t (-) β: Delayed neutron fraction (-) l: Prompt neutron lifetime (s) n(t): Neutron flux at time t (particles / s / cm 2 ) C i (t): Delayed neutron precursor density of group i at time t (particles / cm 3 ) λ i: Decay constant of delayed precursor of group i (1 / s) S: External neutron source strength (pieces / s) β i : Proportion of delayed neutrons in group i (-) i: Group of delayed neutrons (group of delayed neutrons with similar decay constants)

[0048] The reactivity calculation unit 9 stores the reactivity data [ρ(t)] calculated using equations (2) and (3) in the memory 10 together with the measurement time of the neutron flux. The reactivity calculation unit 9 acquires the neutron flux data calculated by the power monitoring device 8 at each predetermined elapsed time, and calculates the reactivity data [ρ(t)]. Therefore, the reactivity calculation unit 9 calculates the reactivity data [ρ(t)] for each elapsed time, and stores it in the memory 10. As a result, the memory 10 holds the corresponding reactivity data [ρ(t)] for each predetermined elapsed time.

[0049] [First calculation unit] 2 shows the configuration of the first calculation unit 13. The first calculation unit 13 has an arithmetic controller 21, an input device 22, a time lag shift calculator 23, a reactivity coefficient calculator 24, and an output device 25.

[0050] The first calculation unit 13 reads M pieces of time series data ρ(t) from the memory 10, starting from the current time of the reactivity data ρ(t m The first calculation unit 13 also acquires N pieces of time series data T(t) from the memory 10, starting from the current time of the temperature T(t) n The first calculation unit 13 obtains the time series data ρ(t m ) and time series data T(t n ) is acquired each time the reactivity calculation unit 9 calculates the reactivity data ρ(t).

[0051] For example, the first calculation unit 13 outputs a command from the calculation controller 21 to the input device 22 to input the reactivity data ρ(t) from the memory 10 to the time lag shift calculator 23. The time lag shift calculator 23 calculates, as the reactivity data ρ(t), M pieces of time-series reactivity data ρ(t) going back a predetermined time (e.g., 600 seconds) from the current time. m) (1≦m≦M) is obtained from memory 10. At the same time, the calculation controller 21 outputs a time delay setting value τ to the time delay shift calculator 23. The time delay setting value τ is sequentially changed and output according to an initial value (e.g., 0 seconds) and an interval (e.g., 5 seconds) for searching for an optimal time delay built into the calculation controller 21.

[0052] Next, the time lag shift calculator 23 calculates the reactivity data ρ(t m +τ). The time delay shift calculator 23 creates the reactivity data ρ(t m +τ) is calculated by dividing the time delay setting value τ input from the calculation controller 21 and the reactivity data ρ(t m At this time, the period from the current time to the time delay setting value τ is excluded. The time delay shift calculator 23 calculates the reactivity data ρ(t m +τ) is output to the reactivity coefficient calculator 24.

[0053] Next, the arithmetic controller 21 inputs the temperature data T(t n ) from the memory 10 to the reactivity coefficient calculator 24. The reactivity coefficient calculator 24 uses N pieces of temperature data T(t n ) (1≦n≦N, N≦M) is obtained from memory 10. Then, the reactivity coefficient calculator 24 calculates N pieces of reactivity data ρ(t m + τ) and a × T(tn), obtained by multiplying the temperature data by the temperature reactivity coefficient a, is calculated using equation (4). In addition, the temperature reactivity coefficient a that minimizes equation (4) is calculated using equation (5).

[0054] In the upper graph of Figure 3, the horizontal axis is time and the vertical axis is reactivity, and the reactivity data ρ(t m ) is shown by a solid line. m) shifted by the time delay setting value τ from the reactivity data ρ(t m +τ) is shown by a dashed line. In the lower graph of FIG. 3, the horizontal axis is time and the vertical axis is reactor water temperature, and the temperature data T(t n ) is shown by a solid line. In addition, in Fig. 3, N reactivity data ρ(t m ), and N pieces of temperature data T(t n ) are indicated by dashed lines and arrows.

[0055]

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[0056]

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[0057] In the calculation using equations (4) and (5), first, N reactivity data ρ(t m +τ) and N temperature data T(t n ) and calculate the temperature reactivity coefficient a. Then, the calculated temperature reactivity coefficient a and N reactivity data ρ(t m +τ) and N temperature data T(t n ) into equation (4) to calculate the square difference SE.

[0058] The reactivity coefficient calculator 24 performs the calculations using equations (4) and (5) every time the calculation controller 21 sequentially changes and outputs the time delay setting value τ. Therefore, the reactivity coefficient calculator 24 holds the square difference SE calculated using equation (4) and the value of a calculated using equation (5) for each changed time delay setting value τ.

[0059] In equation (4), the squared difference SE is the reactivity data ρ(t m ) and the reactivity data ρ(t m +τ) is evaluated. The squared difference SE is the smallest when the reactivity data ρ(t m) and the reactivity data ρ(t m The deviation from the temperature data T(t +τ) shown in FIG. 3 is smallest at the time delay setting value τ when the squared difference SE is smallest. n ) and the reactivity data ρ(t m + τ) is the graph that most closely resembles the graph shown in Fig. 1. Therefore, the time delay setting value τ at which the squared difference SE is smallest is the appropriate value for the response time delay between the actual neutron flux and the temperature change rate. Therefore, by comparing the squared difference SE for each time lag setting value τ using equations (4) and (5), the time lag setting value τ can be appropriately evaluated.

[0060] The reactivity coefficient calculator 24 compares the square difference SE between different time delay set values ​​τ and sets the temperature reactivity coefficient a at which the square difference SE is smallest as the final temperature reactivity coefficient a. The reactivity coefficient calculator 24 sets the time delay set value τ at this time as the final temperature measurement delay time τ. The reactivity coefficient calculator 24 outputs the set final temperature reactivity coefficient a and delay time τ to the output device 25.

[0061] The output device 25 acquires the temperature reactivity coefficient a and the delay time τ. The output device 25 outputs the temperature reactivity coefficient a and the delay time τ to the second calculation unit 14 based on a command from the calculation controller 21. The temperature reactivity coefficient a and the delay time τ do not necessarily have to be determined by the least squares method shown in equations (4) and (5). For example, the temperature reactivity coefficient a and the delay time τ may be determined by other methods, such as by using a correlation coefficient.

[0062] [Second calculation section] 4 shows the configuration of the second calculation unit 14. The second calculation unit 14 shown in FIG.

[0063] The second calculation unit 14 starts operation on the condition that the temperature reactivity coefficient a and the time lag τ are input from the first calculation unit 13 to the calculation controller 31 . When the temperature reactivity coefficient a and the time delay τ are input from the first calculation unit 13, the calculation controller 31 calculates the time series data n(t k ) from the memory 10 to the shift calculator 33. The shift calculator 33 then outputs a command to the input device 32 to input K pieces of neutron flux time series data n(t k ) (1≦k≦K) is obtained from memory 10.

[0064] Next, the shift calculator 33 calculates the time series data n(t k ) and the time series data n(t k The shift calculator 33 creates the shifted neutron flux time series data n(t k +τ) with the input time delay τ and the acquired neutron flux data n(t k At this time, data for the period equivalent to the time delay setting is excluded from the current data. The shift calculator 33 calculates the time series data n(t k +τ) is output to the target neutron flux calculator 34.

[0065] Next, the arithmetic controller 31 inputs the temperature data T(t n ) from the memory 10 to the target neutron flux calculator 34. The target neutron flux calculator 34 inputs J pieces of temperature data T(t n ) (1≦n≦J, J≦K) is obtained from memory 10. Then, the target neutron flux calculator 34 calculates J pieces of temperature data T(t n ) is used to find the temperature change rate dT / dt(t n ) is calculated.

[0066] In Fig. 5, in the upper graph, the horizontal axis represents time and the vertical axis represents the neutron flux. The time-series data n(t k ) of the neutron flux is shown by a solid line. Also, the time-series data n(t k ) of the neutron flux shifted by the time delay setting value τ from the time-series data n(t k ) of the neutron flux is shown by a dashed line. In Fig. 5, in the lower graph, the horizontal axis represents time and the vertical axis represents temperature. The temperature data T(t n ) is shown by a dotted line. In Fig. 5, the ranges of the time-series data n(t k ) of J neutron fluxes and the temperature data T(t n ) of J are shown by dashed lines and arrows.

[0067] Next, the target neutron flux calculator 34 determines whether the ratio of the calculated temperature change rate dT / dt(t T ) to the preset target temperature change rate (dT / dt) n is equal to or greater than B times (0 < B ≤ 1.0). When the ratio is equal to or greater than B times, the target neutron flux calculator 34 obtains, from the time-series data n(tk + τ) of the neutron flux shifted by the delay time τ, the J neutron fluxes n(t n ) where t k = t k ) + τ from the memory 10. Then, the target neutron flux calculator 34 calculates the average value ave_n(t k ) of the J obtained neutron fluxes n(t k ) + τ. Further, the target neutron flux calculator 34 calculates the ratio A of the calculated average value ave_n(t k ) + τ of the neutron flux to the temperature change rate dT / dt(t n ) as shown in Equation (6).

[0068]

Equation

[0069] After calculating the ratio A, the arithmetic controller 31 outputs the target temperature change rate (dT / dt) TThe target neutron flux calculator 34 outputs a command to input the target temperature change rate (dT / dt) from the memory 10. T Based on the ratio A calculated by the above formula (6), the target neutron flux n T Calculate.

[0070]

number

[0071] The target neutron flux calculator 34 calculates the target neutron flux n T is output to the output device 35 together with the temperature reactivity coefficient a and the ratio A of the neutron flux to the temperature change rate. The calculation controller 31 outputs a target neutron flux n T , temperature reactivity coefficient a, and ratio A of neutron flux to temperature change rate to the control rod control calculation unit 6. The calculation of the temperature change rate by the least squares method and the calculation of the average neutron flux by simple averaging used here are for the same period t n =t k As long as J pieces of data that satisfy the condition τ+τ are used, another method may be used.

[0072] The second calculation unit 14 uses the delay time τ appropriately evaluated by the first calculation unit 13 to obtain a ratio A between the temperature change rate and the average value of the neutron flux shifted to a time advanced by the delay time τ. This makes it possible to appropriately calculate the ratio A between the neutron flux and the temperature change rate whose response is delayed relative to the neutron flux. Then, using the calculated ratio A between the temperature change rate and the neutron flux, a target temperature change rate (dT / dt) T The target neutron flux n T By using an appropriate delay time τ, the temperature change rate whose response time is delayed with respect to the neutron flux can be corrected, and the measurement time difference between the neutron flux and the temperature change rate can be appropriately corrected. Therefore, in a configuration in which the response of the temperature change rate is delayed with respect to the neutron flux, the ratio A of the temperature change rate and the neutron flux that corresponds appropriately and the appropriate target neutron flux n T can be calculated.

[0073] [Control rod control calculation section] The control rod control calculation unit 6 determines the target neutron flux n T The control rod control calculation unit 6 starts its operation on the condition that the current neutron flux n(t k ) and the target neutron flux n calculated by the second calculation unit 14 T The control rod control calculation unit 6 determines the operation of the control rod 3 based on the deviation from this. The control rod control calculation unit 6 determines the operation of the control rod 3 using, for example, the deviation Δn calculated by equation (8). If the deviation Δn is equal to or greater than a predetermined value δ1, the control rod control calculation unit 6 determines to insert the control rod 3. On the other hand, if the deviation Δn is equal to or less than a predetermined value δ2 and the period is equal to or greater than a certain value, the control rod control calculation unit 6 determines to withdraw the control rod 3. Then, the control rod control calculation unit 6 outputs a signal to insert or withdraw the control rod 3 to the control rod drive control unit 5. Through the above process, the reactor power control device 50 calculates the neutron flux n(t k ) to the target neutron flux n T can be approached.

[0074]

number

[0075] The control rod control calculation unit 6 repeats the above-mentioned withdrawal / insertion of the control rod 3 until the target temperature is reached. In addition, the control rod control calculation unit 6 determines n(t) and C in the dynamic characteristic equations shown in Equation (9) and Equation (10). i By gradually evolving (t) in small time increments, we can calculate the predicted future neutron flux. Equations (9) and (10) use the current reactivity ρ(t), temperature reactivity coefficient a, and the current neutron flux n(t) described above.

[0076]

number

[0077]

number

[0078] Here, the meaning of each symbol is the same as that described in formula (2) and formula (3). Equation (9) requires a predicted value for reactivity ρ(t). The predicted value for reactivity ρ(t) can be calculated in the following way. First, the temperature change rate dT / dt(t) is calculated from the neutron flux n(t) using the ratio A. Then, the temperature T(t) is calculated from the temperature change rate dT / dt(t). Then, the predicted value for reactivity ρ(t) can be sequentially calculated from the temperature T(t) using the temperature reactivity coefficient a.

[0079] The control rod control calculation unit 6 determines the target neutron flux n T The display unit 15 outputs the calculated predicted value of the neutron flux n(t) together with the current and past neutron fluxes n(t) to the display unit 15. The display unit 15 displays the target neutron flux n T , current and past neutron flux n(t). The display device 15 displays the target neutron flux n T is displayed simultaneously in combination with at least one of the past neutron flux n(t), the current neutron flux n(t), and the predicted future neutron flux value n(t).

[0080] FIG. 6 shows an example of the target neutron flux and past, present and future predicted neutron flux values ​​displayed on display device 15. In this example display screen, the dashed line numbered 1 is the target neutron flux. The set value is displayed as a number at the top of the screen. The past neutron flux is shown as a solid line. The current value is plotted with a white circle and assigned the number 2. The current neutron flux number (present value) is also displayed at the top of the screen. The future predicted neutron flux is shown as a dashed line and assigned the number 3. By constantly displaying the above screen on the display device 15, the operator can easily confirm whether or not it is necessary to perform the withdrawal / insertion operation of the control rods 3 to control the neutron flux to the target value.

[0081] As described above, the reactor power control device 50 described in this embodiment evaluates the response delay time between neutron flux and temperature based on values ​​measured in an actual plant, and calculates the ratio between neutron flux and temperature change rate taking the delay time into consideration. Then, the reactor power control device 50 can accurately obtain a target neutron flux corresponding to a target temperature change rate. Furthermore, the reactor power control device 50 can control the reactor power according to the target neutron flux. In addition, the reactor power control device 50 displays the target neutron flux, past and present values ​​of the neutron flux, and future predicted values ​​on a display device, so that an operator can easily confirm that the control of the power control device is appropriate.

[0082] 3. Second embodiment of reactor power control device Next, a second embodiment of the reactor power control device will be described. FIG. 7 shows a schematic configuration of the reactor power control device of the second embodiment. FIG. 7 also shows a reactor power control device 51 and a main part of a boiling water reactor controlled by the reactor power control device 51. The reactor power control device 51 of the second embodiment differs from the reactor power control device 50 of the first embodiment described above only in that it includes a third calculation unit. Therefore, in the following description, only the configuration related to the third calculation unit will be described, and detailed description of the same configuration as the first embodiment will be omitted.

[0083] The reactor power control device 51 shown in FIG. 7 includes a memory 10, a reactivity calculation unit 9, a first calculation unit 13, a second calculation unit 14, a third calculation unit 16, a control rod control calculation unit 6, and a display device 15.

[0084] The third calculation unit 16 is connected to the memory 10 , the second calculation unit 14 , and the control rod control calculation unit 6 . In the reactor power control device 51, the second calculation unit 14 calculates the target neutron flux n T , the temperature reactivity coefficient a, and the ratio A between the neutron flux and the temperature change rate are output to the third calculation unit 16.

[0085] The configuration of the third calculation unit 16 is shown in Fig. 8. The third calculation unit 16 includes a proportional, integral and differential calculator 41 and a switch 42. The third calculation unit 16 calculates the target neutron flux n T is input to a proportional / integral / differential calculator 41 and a switch 42. The third calculation unit 16 also inputs the target temperature change rate (dT / dt) from the memory 10 to the proportional integral and differential calculation unit 41. T and the temperature change rate dT / dt(t n ) is entered.

[0086] The switch 42 is connected to the switch 42 at a temperature change rate dT / dt(t n ) and the target temperature change rate (dT / dt) T The switch 42 then compares the target temperature change rate (dT / dt) T Temperature change rate dT / dt(t n The ratio of the target temperature change rate (dT / dt) is compared with a preset coefficient D for determining whether to switch control. The coefficient D is stored in the memory 10. The switch 42 is T Temperature change rate dT / dt(t n ) is less than or equal to the coefficient D, S B Therefore, the target neutron flux n input from the second calculation unit 14 to the switch 42 is switched to the T is output as is to the control rod control calculation unit 6.

[0087] On the other hand, the neutron flux increases and the temperature change rate dT / dt(t n ) increases, and the target temperature change rate (dT / dt) T Temperature change rate dT / dt(t n When the ratio of S A Switch to the side. The proportional integral differential calculator 41 receives a target temperature change rate (dT / dt) T and temperature change rate dT / dt(t n ) is input. Therefore, the target temperature change rate (dT / dt) T and temperature change rate dT / dt(t n) are the same value, the same value is always input to the proportional / integral / differential calculator 41.

[0088] The output of the proportional integral differential calculator 41 is the target neutron flux n T Therefore, the temperature change rate dT / dt(t n ) is the target temperature change rate (dT / dt) T When the neutron flux reaches the target value n T is corrected. Then, the corrected target neutron flux n T is output to the control rod control calculation unit 6. The target neutron flux n T The fine adjustment of temperature change rate dT / dt(t n ) deviation.

[0089] Specifically, the proportional integral differential calculator 41 calculates a target temperature change rate (dT / dt) T and temperature change rate dT / dt(t n ) and the target neutron flux n T This corrects the target temperature change rate (dT / dt), for example. T For the temperature change rate dT / dt(t n ) is large, the target neutron flux n T is corrected in the negative direction. As a result, the deviation Δn calculated by equation (8) is increased. Also, for example, the target temperature change rate (dT / dt) T For the temperature change rate dT / dt(t n ) is small, the target neutron flux n T is corrected in the positive direction. As a result, the deviation Δn calculated by equation (8) is reduced.

[0090] 4. Nuclear Reactor Power Control Method Next, an embodiment of a reactor power control method will be described. A flowchart of a reactor power control method is shown in Fig. 9. The flowchart shown in Fig. 9 is a method of controlling the reactor power using the reactor power control device 50 of the first embodiment shown in Fig. 1 described above.

[0091] First, in the reactor control method, the operator adjusts the reactor period after criticality by operating the control rod 3 between 100 seconds and 200 seconds at the start of control to increase neutrons (step S1). Thereafter, data of the neutron flux n(t) is acquired by the output monitoring device 8 and data of the temperature T(t) is acquired by the temperature monitoring device 12 at a constant period (for example, 1 s) (step S2). Next, based on the acquired neutron flux n(t), the reactivity calculation unit 9 calculates the reactivity ρ(t) according to the inverse time equations of equations (2) and (3) (step S3).

[0092] Next, the first calculation unit 13 calculates the time delay τ and the temperature reactivity coefficient a using the reactivity ρ(t) calculated by the reactivity calculation unit 9 and the temperature T(t) (step S4). The first calculation unit 13 calculates the temperature reactivity coefficient a and the squared difference SE using equations (4) and (5) assuming the time delay τ of temperature measurement. Then, the first calculation unit 13 calculates the delay time τ at which the squared difference SE is minimized and the temperature reactivity coefficient a at that time as the final values.

[0093] Next, the second calculation unit 14 determines whether the reactor water temperature has reached the target temperature (step S5). If not (NO in step S5), the second calculation unit 14 calculates the temperature change rate dT / dt(t) using the temperature data T(t n ) over a predetermined time (for example, 120 seconds) by the least squares method or the like (step S6).

[0094] Next, the second calculation unit 14 determines whether the target neutron flux n T is set (step S7). If not (NO in step S7), the second calculation unit 14 determines whether the temperature change rate dT / dt(t) is equal to or greater than B times (0 < B ≤ 1.0) of the target temperature change rate (dT / dt) T (step S8). If the temperature change rate dT / dt(t) is less than B times (NO in step S8), the second calculation unit 14 returns to the determination of whether the target temperature has been reached in step S5, and determines whether the temperature change rate dT / dt(t) is equal to or greater than the target temperature change rate (dT / dt). T The process is repeated until the number of bits is equal to or greater than B.

[0095] If the neutron flux average value ave_n(t k +τ), the neutron flux and the rate of temperature change dT / dt(t n The second calculation unit 14 calculates the ratio A of the average neutron flux ave_n(t k +τ) is the time series data of neutron flux at a time shifted by a time delay τ from the specified time used in the calculation of the temperature change rate dT / dt. k +τ) is used as the basis.

[0096] Next, the second calculation unit 14 calculates the ratio A of the calculated neutron flux to the temperature change rate as a target temperature change rate (dT / dt) T Multiplying by the target neutron flux n T is calculated (step S10). Target neutron flux n T If set (YES in step S7), or if the target neutron flux n T After calculating the current neutron flux n(t k ) and the target neutron flux n T The control rod control calculation unit 6 calculates the deviation Δn from the set value δ1 and determines whether to insert or withdraw the control rod 3 (step S11). Specifically, if the calculated deviation Δn is greater than a set value δ1, the control rod control calculation unit 6 determines to insert the control rod 3. Also, if the calculated deviation Δn is less than a set value δ2 and the period is equal to or greater than a certain value, the control rod control calculation unit 6 determines to withdraw the control rod 3.

[0097] If the reactor water temperature has reached the target temperature (YES in step S5), the process according to this flowchart ends. After the control rod operation determination and operation are performed, the process may return to the determination of whether the target temperature has been reached (step S5), and control may be repeated until the target temperature is reached. By controlling the reactor output according to this flowchart, the same effects as those of the first embodiment, which is based on automatic control, can be obtained even in the case of manual control.

[0098] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to an embodiment having all of the configurations described. It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to delete a part of the configuration of each embodiment, or to add or replace another configuration. [Explanation of symbols]

[0099] 1 Pressure vessel, 2 Reactor core, 3 Control rod, 4 Control rod drive device, 5 Control rod drive control section, 6 Control rod control calculation section, 7 Neutron detector, 8 Power monitoring device, 9 Reactivity calculation section, 10 Memory, 11 Temperature detector, 12 Temperature monitoring device, 13 First calculation section, 14 Second calculation section, 15 Display device, 16 Third calculation section, 21, 31 Calculation controller, 22, 32 Input device, 23, 33 Shift calculation device, 24 Reactivity coefficient calculation device, 25, 35 Output device, 34 Target neutron flux calculation device, 41 Proportional integral differential calculation device, 42 Switch, 50, 51 Reactor power control device

Claims

1. A reactivity calculation unit that calculates reactivity from neutron flux; a first calculation unit that calculates a temperature reactivity coefficient and a delay time of temperature measurement from the reactivity and the reactor water temperature; a second calculation unit that calculates a temperature change rate from a change in the reactor water temperature, and calculates and outputs a target neutron flux corresponding to a target temperature change rate based on the temperature change rate, a delay time of the temperature measurement, and a neutron flux shifted in time by the delay time; and a control rod control calculation unit that sets the output target neutron flux. A nuclear reactor power control device comprising:

2. The first calculation unit includes: N pieces of time series data T(t ｎ ) (1≦n≦N), and M pieces of time series data ρ(t ｍ ) (1≦m≦M, N≦M) is acquired, and the time series data ρ(t ｍ + τ), The time series data T(t ｎ ) by the temperature reactivity coefficient a, ｎ = t ｍ +τ for a given set of N (N≦M) ｍ + τ) and a × T(t ｎ ) and the difference {ρ(t ｍ + τ) - a × T (t ｎ )} and calculate the delay time τ and the temperature reactivity coefficient a by the least squares method. The reactor power control device according to claim 1 .

3. The second calculation unit includes: J pieces of time series data T(t ｎ ) (1≦n≦J) and K pieces of neutron flux time series data n(t ｋ ) (1≦k≦K, J≦K), The time series data T(t ｎ ) is obtained by approximating the temperature change rate dT / dt(t ｎ ) (1≦n≦J), The target temperature change rate (dT / dt) Ｔ The temperature change rate dT / dt (t ｎ When the ratio of the neutron flux to the time series data n(t ｋ + τ) of t ｎ = t ｋ + τ, and calculate the ratio A of the average value of the J pieces of data The target temperature change rate (dT / dt) Ｔ The target neutron flux n corresponding to Ｔ Calculate The reactor power control device according to claim 1 .

4. a display device that displays the target neutron flux calculated by the second calculation unit; The reactor power control device according to claim 1 .

5. The display device simultaneously displays the target neutron flux calculated by the second calculation unit in combination with at least one selected from a past neutron flux, a current neutron flux, and a future neutron flux prediction value. The reactor power control device according to claim 4.

6. a third calculation unit that calculates a deviation from the target temperature change rate by using at least one selected from proportional, integral, and differential, and corrects the target neutron flux calculated by the second calculation unit by using the calculated deviation. The reactor power control device according to claim 1 .

7. The correction of the target neutron flux by the third calculation unit is started when the ratio of the temperature change rate to the target temperature change rate becomes D times (0<D≦1.0). The reactor power control device according to claim 6.

8. Calculate reactivity from neutron flux, Calculating a temperature reactivity coefficient and a temperature measurement delay time from the reactivity and the reactor water temperature; Calculating a temperature change rate from the change in the reactor water temperature; Calculating a ratio of the neutron flux to the temperature change rate based on the neutron flux, the temperature change rate, and the delay time; Calculating a target neutron flux corresponding to the target temperature change rate; Controlling the withdrawal and insertion of control rods so that the neutron flux matches the target neutron flux. A method for controlling nuclear reactor power.

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