JP4590361B2 - Nuclear reactor system - Google Patents

Description

  The present invention relates to, for example, a reactor system and a reactor control method for a natural circulation boiling water reactor in which a coolant is circulated by natural circulation.

  In general, boiling water reactors can be roughly classified into forced circulation type and natural circulation type depending on the circulation method of the coolant (cooling water). A forced circulation boiling water reactor (hereinafter referred to as a forced circulation nuclear reactor) is equipped with a jet pump or an internal pump, and the pump is used to forcibly feed cooling water into the core. It has become.

  On the other hand, a natural circulation boiling water reactor (hereinafter referred to as a natural circulation nuclear reactor) does not have a pump for forcibly circulating cooling water like the above forced circulation nuclear reactor, Cooling water is circulated by the natural circulation force based on the density difference (water head difference) between the cooling water outside the surrounding reactor shroud and the gas-liquid mixed flow in which water and steam inside the reactor shroud are mixed. .

  In this way, in a natural circulation reactor, cooling water is circulated by natural circulation force, so that a cooling water flow rate in the core equivalent to a forced circulation reactor in which cooling water is forcibly circulated by a pump is obtained. This is difficult, and the ascending flow path above the core is lengthened to promote recirculation. As a result, if an attempt is made to maintain a reactor plant start-up time comparable to that of a forced circulation reactor, the coolant flow rate in the core becomes unstable for about 1-2 hours at the time of start-up.

  Specifically, when the boiling water reactor (BWR) is started, first, the core is brought into a critical state by pulling out the control rod inserted in the core, and then the neutron flux is increased to supply the core cooling water. The core is heated to about 280 ° C during rated operation, and the pressure in the furnace is increased to about 7 MPa. In this temperature raising and pressure increasing process, the output is adjusted by operating the control rod so as to raise the reactor water temperature within the limit value of 55 ° C./h.

  In order to complete the temperature raising and pressurizing process in a short time, it is necessary to keep the temperature increase rate constant at a value as close as possible to the limit value. In particular, the main steam isolation valve is closed at the initial stage of the temperature rise and pressure rise process, and the rate of increase of the reactor power and the reactor water temperature is in a proportional relationship, so that the output as high as possible does not exceed the limit value. Maintaining it leads to a reduction in startup time.

Here, an improved boiling water reactor (ABWR) is known in which an output control device has a function of operating a control rod so as to maintain a set temperature increase rate (see, for example, Patent Document 1). ). The same control is also required for natural circulation boiling water reactors (ESBWR), but in low pressure conditions, the flow rate inherent to natural circulation reactors is unstable, so it is necessary to reduce the output to a stable level. Is also known to occur (see, for example, Patent Document 2).
Patent 3357975 JP-A-5-256991

  The reactor power control apparatus described in Patent Document 1 described above is provided with a change rate limiter to limit the rate of increase of the temperature change rate set value in the process of raising and lowering the temperature of the reactor. This is to prevent overshoot of the temperature change rate due to a sudden rise in the set value at the time, and since the temperature change rate is changed over time, the temperature change rate is reduced only when the reactor is in an unstable region Such control is not possible. Therefore, when applied to a natural circulation furnace as it is, in order to avoid instability of the natural circulation furnace at a low pressure, if the output is lowered more than necessary in the temperature raising and boosting process, the startup time is extended. In particular, the unstable region at low pressure transitions to the higher output side as the pressure increases, so if the output and temperature increase rate are set to the lowest pressure, the rate of increase will be higher than necessary when the pressure increases. It will limit. Therefore, if the temperature increase rate setting is manually adjusted according to the pressure, the work burden on the operator increases, and the merit of automating control rod operation is greatly impaired.

  In the natural circulation reactor described in Patent Document 2, the reactor water temperature is raised by nuclear heating from a state where the subcooling degree of the core inlet is very large (about 50 ° C.) to a state where the subcooling degree is close to zero, and then the subcooling is performed. The procedure for boosting the reactor pressure while maintaining the temperature close to zero is shown, but in reality, flow instability occurs in the process of nuclear heating from a state where the subcooling degree is large to a state where the subcooling degree is close to zero. Will occur.

  Furthermore, in the conventional natural circulation reactor, the temperature change rate is set to a constant value, so if it is set to avoid instability at the lowest pressure, the output will be limited more than necessary when the pressure rises. There was an inconvenience.

  The present invention is for solving the above-mentioned problems, and does not increase the work burden on the operator, and enters an unstable region determined by the relationship between temperature and pressure in the reactor at the time of startup. The purpose is to stably control the reactor in a short time so that there is no.

  In order to solve the above problems and achieve the object of the present invention, a reactor system of the present invention forms an ascending channel and a descending channel for a coolant inside a reactor pressure vessel, and cools the rising channel. The present invention is applied to a nuclear reactor system having a natural circulation system in which a coolant is circulated by a density (buoyancy) difference between the material and a coolant in a descending flow path.

  The reactor system of the present invention includes an output control unit that generates a control rod operation signal for extracting and inserting a control rod inside the reactor pressure vessel based on the reactor water temperature change rate, and a natural circulation system. Based on the detected reactor water level signal, it has a feed water control unit that generates a feed water flow rate to the reactor pressure vessel and a waste water flow rate signal from the reactor, and a process calculation unit that supervises the output control unit and the feed water control unit The reactor water temperature change rate setting function for adjusting the set value of the reactor water temperature change rate based on the fluctuation amount of the reactor water level signal is added to the output control unit, the feed water control unit, or the process calculation unit.

As described above, in the reactor system of the present invention, the reactor water temperature change rate setting function monitors the instability due to the fluctuation of the reactor water level, and when the fluctuation becomes large, the set value of the reactor water temperature change rate is set. Decrease. Further, when the fluctuation becomes small, the set value of the reactor water temperature change rate is increased.
Furthermore, when the fluctuation is large, the function to output the control rod drive inhibition signal implements control rod operation inhibition, or the function to output the control rod insertion signal implements selective control rod insertion, thereby stabilizing the flow rate and water level. Can be kept in.

More simply, at least as a function of the reactor pressure and the cooling water temperature at the core inlet, a power or rate of temperature change that does not cause instability of the water level is stored in the start-up controller and a function or reference table is stored in The temperature change rate set value can be adjusted based on the measurement data from the furnace instrumentation system. Note that it is also effective to add control rod drive blocking and selection control rod insertion functions in case the water level instability becomes greater than a certain level.
Thus, for example, the set value of the reactor water temperature change rate is controlled based on the fluctuation amount of the reactor water level so that it is outside the unstable region generated according to the temperature and pressure inside the reactor pressure vessel. Thus, the reactor can be stably controlled in a short time so as not to enter an unstable region determined by the relationship between the temperature and pressure in the reactor at the time of startup.

  Further, the reactor control method of the present invention is a natural control method in which a coolant is circulated by a difference in density (buoyancy) between the coolant in the ascending flow channel and the descending flow channel formed in the reactor pressure vessel. The present invention is applied to a nuclear reactor control method for controlling a nuclear reactor using a circulation system.

  The reactor control method of the present invention includes a step of detecting the amount of fluctuation of the reactor water level based on the reactor water level signal detected from the natural circulation system, and the amount of fluctuation of the reactor water level from a predetermined value. And a step of reducing the set value of the reactor water temperature change rate set for the reactor pressure vessel when the fluctuation amount of the reactor water level is larger than a predetermined value. Increasing the set value of the reactor water temperature change rate set for the reactor pressure vessel when the fluctuation amount of the reactor water level is smaller than a predetermined value, and the reactor pressure vessel at the time of start-up Determining whether or not a set value of the reactor water temperature change rate has been set so as to be out of an unstable region generated according to the pressure inside the reactor and the temperature inside the reactor pressure vessel. .

According to the control method of the present invention, since the set value of the reactor water temperature change rate is controlled based on the amount of fluctuation of the reactor water level, the reactor enters an unstable region determined by the relationship between the temperature and pressure in the reactor at startup. It is possible to control the reactor stably so that nothing happens.
Furthermore, because the set value of the reactor water temperature change rate is controlled based on the amount of fluctuation in the reactor water level even at high pressure, it does not enter the unstable region determined by the relationship between the temperature and pressure inside the reactor at high pressure. Thus, the nuclear reactor can be stably controlled in a short time.

According to the present invention, by controlling the set value of the reactor water temperature change rate based on the fluctuation amount of the reactor water level, it is possible to enter an unstable region determined by the relationship between the temperature and pressure in the reactor at the time of startup. As a result, the reactor can be stably controlled in a short time. Furthermore, starting efficiency can be improved.
As described above, in the present invention, since the temperature change rate value setting is adjusted based on the monitoring of the unstable state, it is possible to always obtain the optimum temperature change rate and to shorten the start-up time.
Further, it is not necessary for the operator to frequently monitor the unstable state and adjust the rate of temperature change, thereby reducing the work load.

  Embodiments of a reactor system and a reactor control method according to the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a nuclear reactor system to which a natural circulation boiling water nuclear reactor according to the present invention is applied.

As shown in FIG. 1, a natural circulation boiling water reactor (hereinafter referred to as “natural circulation reactor”) included in a natural circulation reactor system includes a plurality of fuel rods inside a reactor pressure vessel 6. A core 4 having a control rod 3 inserted into the gap.
In addition, a control rod driving device 44 that drives the control rod 3 in the core 4 so that the control rod 3 can be inserted and removed in the vertical direction is provided below the reactor pressure vessel 6. A main steam pipe 12 and a water supply pipe 13 are connected to the reactor pressure vessel 6, and a cylindrical shroud 5 is disposed inside the reactor pressure vessel 6 so as to surround the reactor core 4.

  Inside the shroud 5, an ascending passage for the coolant to rise in the direction of the arrow shown in the figure is formed, and the coolant descends in the gap between the shroud 5 and the reactor pressure vessel 6. A downcomer that is a descending flow path is formed. A cylindrical chimney 9 is disposed above the shroud 5, and an air-water separator (separator) 10 and a steam dryer (dryer) 11 are disposed above the chimney 9.

  Inside the chimney in the reactor pressure vessel 6, the gas-liquid two-phase coolant boiled in the core 4 passes, and the gas-liquid two-phase coolant and the liquid single-phase coolant that passes through the downcomer Due to the difference in density, a circulation flow path is formed in which the coolant goes down the downcomer and then moves to the core 4 side and passes through the core 4 and rises in the chimney 9. Then, when the mixed flow of the cooling water and water vapor that has risen in the chimney 9 passes through the steam / water separator 10, the steam is separated by the steam / water separator 10. The single-phase cooling water separated from the steam separator 10 descends again and passes through the lower part of the reactor pressure vessel 6 and is sent to the core 4 in the shroud 5.

  Further, the steam separated by the steam separator 10 is further removed from the water droplets by the steam dryer 11 and supplied to the turbine 18 via the main steam pipe 12. The turbine 18 and the generator 21 connected to the turbine 18 are rotated by the flow force of the steam to generate power.

  The steam that has rotated the turbine 18 is introduced into the condenser 23 through the extraction line and condensed. Cooling water (condensate) condensed in the condenser 23 is returned to the reactor pressure vessel 6 from the feed water pipe 13 by the feed water pump 24. Further, the water supply pipe 13 is provided with a flow rate adjusting valve 25, and the flow rate of the cooling water flowing back into the reactor pressure vessel 6 is adjusted by the flow rate adjusting valve 25, whereby the atoms in the reactor pressure vessel 6 are adjusted. Reactor water level can be controlled. Further, the feed water pipe 13 is provided with a feed water heater (not shown). In this feed water heater, the steam extracted from the middle stage of the turbine 18 rises to a suitable temperature. It is heated and injected into the reactor pressure vessel 6.

  The main steam pipe 12 is provided with a main steam isolation valve (not shown) and a turbine steam flow rate adjusting valve 28 for adjusting the amount of steam introduced into the turbine 18, and an escape pipe and bypass pipe 30 (not shown) are connected. Yes. When the turbine steam flow control valve 28 is throttled, the turbine bypass valve 31 provided in the bypass pipe 30 is opened, and the condenser 23 is directly connected via the bypass pipe 30 without introducing a part of the steam into the turbine 18. To be introduced. When the main steam isolation valve is closed, the safety valve provided in the escape pipe is opened, and the steam generated in the nuclear reactor is introduced into a suppression pool (not shown) in the containment vessel to condense the steam. It is supposed to be.

  In the embodiment of the present invention, the output control device 41 moves the control rod 3 up and down inside the reactor pressure vessel 6 based on the reactor water temperature change rate set for the reactor pressure vessel 6. A control rod operation signal 51 to be supplied to the control rod drive control device 42 to be moved is generated. In addition, the water supply control device 43 adjusts the water supply pump 24, the flow rate adjustment valve 25, and the drainage flow rate adjustment valve 88 based on the reactor water level signal 52 detected from the detector provided in the water supply pipe 19 of the natural circulation system. A feed water flow rate and a drain flow rate signal for the reactor pressure vessel 6 are generated. Further, the process computer 45 issues a command according to a predetermined process so as to control the output control device 41 and the water supply control device 43.

  A temperature increase rate setting unit 48 having a reactor water temperature change rate setting function for adjusting the set value of the reactor water temperature change rate based on the fluctuation amount of the reactor water level signal is added to the water supply control device 43. The temperature increase rate setting unit 48 can be added to either the output control device 41 or the process computer 45 instead of the water supply control device 43. The temperature increase rate setting unit 48 having the reactor water temperature change rate setting function controls the reactor water temperature increase rate setting value 53 based on the fluctuation amount of the reactor water level.

  Further, the interlock signal generation unit 49 of the water supply control device 43 generates a control rod drive inhibition signal 54 and a selection control rod insertion signal when the instability of the water level becomes greater than a certain level based on the reactor water level signal 52. 55 is supplied to the control rod drive controller 42. By supplying a drive control signal from the control rod drive control device 42 to the control rod drive device 44, the control rod drive device 44 performs the drive for blocking the control rod 3 and selectively inserting the control rod 3. Execute.

  Then, the temperature rise rate setting unit 48 having the reactor water temperature change rate setting function, for example, the amount of change in the reactor water level so as to be outside the unstable region generated according to the temperature and pressure inside the reactor pressure vessel. By controlling the reactor water temperature rise rate set value 53 based on the above, the reactor can be stably controlled in a short time so that it does not enter the unstable region determined by the temperature-pressure relationship in the reactor at startup. Like to do.

  A neutron flux detector 47 is provided inside the reactor pressure vessel 6 and the amount of neutron flux generated by the nuclear reaction process is detected by a detection signal from the neutron flux detector 47. The neutron flux monitoring device 46 that detects the bundle supplies a reactor output 56 corresponding to the detected amount of neutron flux to the output control device 41.

  The reactor pressure vessel 6 has a thermometer (not shown) for measuring the temperature of the cooling water in the reactor, and a pressure gauge (not shown) for measuring the pressure of the cooling water in the reactor at the lower part thereof. The reactor pressure signal 57 and the temperature signal are supplied to the output control device 41. The pressure gauge may be an absolute value gauge or a differential pressure gauge.

  Hereinafter, based on FIGS. 2-5, the detailed structure of the temperature rise rate setting part 48 of the water supply control apparatus 43 and the interlock signal generation part 49 is demonstrated. 2 to 5 are diagrams showing the temperature increase rate setting unit 48 and the interlock signal generation unit 49 of the water supply control device 43 shown in FIG. 1 in more detail. Portions common to FIG. 1 are given the same reference numerals. The description of the function of the apparatus part already described in FIG. 1 is omitted.

  In FIG. 2, the temperature increase rate setting unit 48 having a reactor water temperature change rate setting function is based on a water level signal 62 detected from a water level detector 61 provided in the water supply pipe 19 of the natural circulation system for Δt seconds. The maximum value calculation unit 63 and the minimum value calculation unit 64 for Δt seconds calculate the maximum value for Δt seconds and the minimum value for Δt seconds. Then, the subtractor 65 subtracts the minimum value for Δt seconds from the calculated maximum value for Δt seconds. Further, a water level fluctuation set value 67 is supplied to the subtractor 66, and the output of the subtracter 65 is subtracted from the water level fluctuation set value 67 in the subtractor 66.

  Then, the subtraction output value of the subtractor 66 is proportionally calculated and integrated by the proportional calculation unit 68 and the integral calculation unit 69, and the proportional calculation value and the integral calculation value are added by the adder 70. The added output value of the adder 70 is output to the output control device 41 as a temperature change rate set value 72 after the upper limit value is limited by the limiter 71.

  Thereby, when the fluctuation amount of the reactor water level based on the reactor water level signal 62 is large, the set value 72 of the reactor water temperature change rate is decreased, and when the fluctuation amount of the reactor water level based on the reactor water level signal 62 is small. The set value 72 of the reactor water temperature change rate is increased.

  Further, in FIG. 3, the temperature rise rate setting unit 48 having another reactor water temperature change rate setting function is supplied with a water level signal 62 detected from a water level detector 61 provided in the water supply pipe 19 of the natural circulation system. The Then, the fast Fourier transform unit 73 performs fast Fourier transform on the water level signal 62, thereby transforming the water level signal 62 in the time domain into the frequency domain. Next, the amplitude of the designated band is extracted from the water level signal 62 converted into the frequency domain by the amplitude extracting unit 74 of the designated band. The amplitude extraction output value of the amplitude extraction unit 74 is subtracted from the water level fluctuation set value 67 in the subtractor 66, and the output of the subtractor 66 is supplied to the proportional calculation unit 68 and the integral calculation unit 69.

  Then, proportional calculation and integral calculation are performed by the proportional calculation unit 68 and the integral calculation unit 69, and the proportional calculation value and the integral calculation value are added by the adder 70. The added output value of the adder 70 is output to the output control device 41 as the temperature change rate set value 72 after the upper limit value is limited by the limiter 71.

  As a result, the maximum amplitude of the specified frequency range is calculated by fast Fourier transforming the reactor water level signal 62, and when the maximum amplitude is large, the set value 72 of the reactor water temperature change rate is decreased, and when the maximum amplitude is small. The set value 72 of the reactor water temperature change rate is increased.

FIG. 4 is a block diagram showing the detailed configuration of the interlock signal generator.
In FIG. 4, the interlock signal generator 49 of the water supply control device 43 is supplied with a water level signal 62 detected from a water level detector 61 provided in the water supply pipe 19 of the natural circulation system. Based on this water level advance 62, the maximum value calculation unit 63 for Δt seconds and the minimum value calculation unit 64 for Δt seconds calculate the maximum value for Δt seconds and the minimum value for Δt seconds, and the subtractor 65 calculates Δt seconds. The minimum value of Δt seconds is subtracted from the maximum value of. The output of the subtracter 65 is supplied to the subtractor 66 where it is subtracted from the water level fluctuation set value 67.

  Then, the subtraction output value of the subtractor 66 is supplied to the comparator 77 and the comparator 78. The comparator 77 amplifies the subtraction output value of the subtractor 66 in proportion to the control rod drive inhibition set value 75 to generate the control rod drive inhibition signal 54. Further, the comparator 78 amplifies the subtraction output value of the subtractor 66 in proportion to the setting value 76 for selecting the selection control rod, and generates the selection control rod insertion signal 55. Then, the control rod drive inhibition signal 54 and the selection control rod insertion signal 55 are supplied to the control rod drive control device 42.

  Further, when the fluctuation amount of the reactor water level signal 62 is larger than a preset set value 67, an interlock signal generating unit 49 of the water supply control device 43 having a function of outputting a control rod insertion signal 55 selected in advance. May be added to the output control device 41, the water supply control device 43, or the process computer 45.

  Further, when the fluctuation amount of the reactor water level signal 62 is larger than a preset set value 67, the output control is performed on the interlock signal generation unit 49 of the water supply control device 43 having a function of outputting the control rod drive inhibition signal 54. You may make it add to the apparatus 41 or the process computer 45. FIG.

  Further, the maximum amplitude of the specified frequency range is calculated by fast Fourier transforming the reactor water level signal 62, and when the maximum amplitude is larger than a preset value 67, the control rod insertion signal 55 or You may make it add the interlock signal generation part 49 of the water supply control apparatus 43 which has the function to output the control-rod drive element signal 55 to the output control apparatus 41 or the process computer 45. FIG.

FIG. 5 is a block configuration diagram showing a detailed configuration of another temperature increase rate setting unit.
In the temperature increase rate setting unit 48 having another reactor water temperature change rate setting function in FIG. 5, the reactor pressure signal 81 and the core inlet temperature signal 82 are supplied to the temperature change rate set value calculation unit 83. Further, the saturated water enthalpy table 85, the compressed water enthalpy table 86, the core flow rate, and other constants 87 stored in the storage memory 84 are supplied to the temperature change rate set value calculation unit 83.

The temperature change rate set value calculation unit 83 uses the saturated water enthalpy table 85, the compressed water enthalpy table 86, the core flow rate, and other constants 87 to calculate the reactor pressure based on the reactor pressure signal 81 as a previously stored function. The temperature change rate set value calculation output value is based on a function such that the higher the temperature change rate set value 72 is, the higher the temperature change rate set value 72 is, the lower the core inlet temperature is based on the core inlet temperature signal 82. Is calculated and output.
The temperature change rate set value calculation output value is output to the output control device 41 as the temperature change rate set value 72 after the upper limit value is limited by the limiter 71.

  Here, as described above, the function stored in advance in the temperature change rate set value calculation unit 83 has a higher temperature change rate set value as the reactor pressure is higher, and a higher temperature change rate set value as the core inlet temperature is lower. A specific example of this function will be described.

  A specific example of a function is shown for the flow instability phenomenon that occurs due to the start of boiling at the chimney 9 outlet. When the pressure in the upper plenum of the reactor pressure vessel 6 is P, it is unstable if it is assumed that the pressure at the outlet of the chimney 9 can be calculated by P-ΔP1 and the pressure at the core inlet can be calculated by P-ΔP2 (ΔP1, ΔP2 are constants) The core power Q at the limit that does not cause the error can be approximated by the following equation (1).

[Equation 1]
Q = W × [hsat (P−ΔP1) −hf (P−ΔP2, T)]
here,
W: Core inlet flow rate
hsat: Enthalpy of saturated water
hf: Enthalpy of compressed water
P: Upper plenum pressure
P-ΔP1: Chimney outlet pressure
P-ΔP2: Core inlet pressure

  hsat: saturated water enthalpy and hf: compressed water enthalpy are stored in the storage memory 84 as a saturated water enthalpy table 85 and a compressed water enthalpy table 86, and the table value to the temperature change rate set value calculation unit 83 is stored. The value can be obtained by extrapolation of.

  At this time, if the value is stored in advance assuming that the core inlet flow rate is also constant, the core power Q at which the instability does not occur is the pressure P in the upper plenum portion of the reactor pressure vessel 6 (P is the normal reactor) Used as a pressure signal) and the temperature T at the core inlet. Since steam is not extracted at the beginning of the temperature rise and pressure increase, it can be approximated that Q and the temperature change rate are proportional. Therefore, the temperature change rate set value can be obtained by the following equation (2).

[Equation 2]
Set temperature change rate = α × W × [hsat (P−ΔP1) −hf (P−ΔP2, T)], (α is a constant)

  FIG. 6 is a diagram showing the enthalpy of saturated water stored in the saturated water enthalpy table 85, and FIG. 7 is a diagram showing the enthalpy of compressed water stored in the compressed water enthalpy table 86.

  As can be seen from this figure, at least the reactor pressure signal 81 and the temperature signal 82 of the core inlet inside the reactor pressure vessel 6 are input, and the set value 72 of the reactor water temperature change rate is determined by a function stored in advance. can do. The reactor water temperature change rate setting function may be added to the output control device 41 or the process computer 45.

  Further, the reactor power set value is calculated from at least the reactor pressure signal 81 and the temperature signal 82 at the core inlet inside the reactor pressure vessel 6 by a function stored in advance. When the reactor output signal 56 based on the detection of the neutron flux inside the reactor pressure vessel 6 exceeds the calculated reactor output set value, a control rod insertion signal 55 selected in advance is output. The interlock signal generator 49 of the water supply control device 43 having this function may be added to the output control device 41 or the process computer 45 instead of the water supply control device 43.

  Further, the reactor power set value is calculated from at least the reactor pressure signal 81 and the temperature signal 82 at the core inlet inside the reactor pressure vessel 6 by a function stored in advance. When the reactor output signal 56 based on the detection of the neutron flux inside the reactor pressure vessel 6 exceeds the reactor output set value, the control rod drive inhibition signal 54 is output. The interlock signal generator 49 of the water supply control device 43 having this function may be added to the output control device 41, the water supply control device 43, or the process computer 45 instead of the water supply control device 43.

Next, regarding the control of the set value of the specific reactor water temperature change rate according to the present embodiment, the diagram illustrating the control of the set value of the reactor water temperature change rate shown in FIG. 8, and the reactor water temperature change shown in FIG. This will be described with reference to a flowchart showing the control operation of the rate setting value.
9 is the temperature increase rate setting unit 48 of the water supply control device 43.

First, the temperature increase rate setting unit 48 detects the fluctuation amount of the reactor water level based on the reactor water level signal detected from the natural circulation system (step S1).
Next, the temperature increase rate setting unit 48 determines whether or not the fluctuation amount of the reactor water level is larger than a predetermined value (step S2).

Subsequently, the temperature increase rate setting unit 48 determines the reactor water temperature change rate set for the reactor pressure vessel 6 when the variation amount of the reactor water level is larger than a predetermined value in the determination step S2. The set value is lowered (step S3).
Further, the temperature rise rate setting unit 48 sets the reactor water temperature change rate set for the reactor pressure vessel 6 when the fluctuation amount of the reactor water level is smaller than a predetermined value in the determination step S2. Is increased (step S4).

Here, the temperature increase rate setting unit 48 determines whether or not the set value of the reactor water temperature change rate is outside the unstable region at the time of low pressure P1, that is, the inside of the reactor pressure vessel 6 at the time of startup (time T1). It is determined whether or not the set value of the reactor water temperature change rate is set so as to be outside the unstable region generated according to the pressure and temperature (step S5).
FIG. 8 is a diagram for explaining the control of the set value of the reactor water temperature change rate corresponding to the reactor power. As shown in FIG. 8, the temperature increase rate setting unit 48 is a low pressure at startup. At time P1, as shown from the time point T1 to the time point T2, the reactor power is increased until just before entering the unstable region so as to be outside the unstable region. Here, since the relationship in which the reactor output increases or decreases in accordance with the set value of the reactor water temperature change rate is known, the temperature increase rate setting unit 48 maintains the stable region until immediately before entering the unstable region. To be controlled.

  In the flowchart of FIG. 9 again, the reactor water is set so as to be out of the unstable region that occurs according to the pressure and temperature inside the reactor pressure vessel 6 at the time of start-up (time T1) at which the pressure P1 is low in the judgment step S5. If it is determined that the set value of the temperature change rate is set, then the temperature increase rate setting unit 48 determines whether or not the pressure has increased from the low pressure P1 to the high pressure P2 (step S6). ). That is, the temperature increase rate setting unit 48 determines whether or not the pressure inside the reactor pressure vessel 6 has reached a predetermined high pressure rating corresponding to the high pressure P2 from the low pressure P1.

  In the determination step S5, the reactor water temperature change rate is set so as to be outside the unstable region that occurs according to the pressure inside the reactor pressure vessel 6 and the temperature inside the reactor pressure vessel 6 at the time of startup (time T1). When the value is not set and when the pressure does not increase from the low pressure P1 to the high pressure P2 in the determination step S6, the process returns to step S1 and the determination and processing from step S1 to step S6 are repeated.

Next, when the pressure rises from the low pressure P1 to the high pressure P2 in the determination step S6, the temperature increase rate setting unit 48 calculates the fluctuation amount of the reactor water level based on the reactor water level signal detected from the natural circulation system. Detect (step S7).
Then, the temperature increase rate setting unit 48 determines whether or not the fluctuation amount of the reactor water level is larger than a predetermined value (step S8).

  The temperature rise rate setting unit 48 sets the set value of the reactor water temperature change rate set for the reactor pressure vessel 6 when the fluctuation amount of the reactor water level is larger than a predetermined value in the determination step S8. When the fluctuation amount of the reactor water level is smaller than a predetermined value, the set value of the reactor water temperature change rate is increased (step S10).

Subsequently, the temperature rise rate setting unit 48 sets the set value of the reactor water temperature change rate so that it is outside the unstable region generated according to the pressure and temperature inside the reactor pressure vessel 6 at high pressure P2. It is determined whether or not (step S11).
Then, the temperature rise rate setting unit 48 sets the reactor water temperature change rate so that it is outside the unstable region that occurs according to the pressure and temperature inside the reactor pressure vessel 6 at the high pressure P2 in the judgment step S11. Is set, it is determined whether or not the pressure inside the reactor pressure vessel 6 has reached a preset target value pressure (step S12).

When the set value of the reactor water temperature change rate is not set so as to be outside the unstable region generated according to the pressure and temperature inside the reactor pressure vessel 6 at the high pressure P2 in the determination step S11, and in the determination step S12 If the pressure inside the reactor pressure vessel 6 does not reach the preset target value pressure, the process returns to step S7, and the determination and processing from step S7 to step S12 are repeated.
When the pressure inside the reactor pressure vessel 6 reaches a preset target value pressure in the determination step S12, the process is terminated.
In FIG. 9, two different instability avoidance processes (S1 to S5 and S7 to S11) are applied according to the determination conditions of P1 and P2. However, only one P1 or three or more determination conditions are set, respectively. Different instability avoidance processing may be performed.
As described above, according to the present embodiment, in the natural circulation boiling water reactor, the reactor water level is fed back to control the temperature raising and boosting process at the time of startup, so the water level exceeds the limit value. It is possible to prevent scrum from occurring. At the same time, it is possible to set the maximum temperature change rate within a range where the stability of the reactor can be ensured, and to shorten the startup time.

  The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention described in the claims. It goes without saying that the embodiment is included.

It is a mimetic diagram showing the whole composition of one embodiment of the nuclear reactor system provided with the natural circulation type nuclear reactor of this embodiment. It is a block block diagram which shows the detailed structure of a temperature rise rate setting part. It is a block block diagram which shows the detailed structure of another temperature rise rate setting part. It is a block block diagram which shows the detailed structure of an interlock signal generation part. It is a block block diagram which shows the detailed structure of another temperature rise rate setting part. It is a figure which shows the enthalpy of saturated water. It is a figure which shows the enthalpy of compressed water. It is a figure explaining the control of the set value of the reactor water temperature change rate. It is a flowchart which shows the control operation of the setting value of the reactor water temperature change rate.

Explanation of symbols

1 ... Fuel rod, 3 ... Control rod, 4 ... Core, 5 ... Shroud, 6 ... Reactor pressure vessel, 8 ... Control rod drive, 9 ... Chimney, 10 ... Steam separator (Separator), 11 ... Steam dryer (dryer), 12 ... Main steam pipe, 13 ... Water feed pipe, 18 ... Turbine, 21 ... Generator, 23 ... Condenser, 24 ... Feed water pump , 25 ... Flow control valve, 30 ... Bypass pipe, 31 ... Turbine bypass valve, 41 ... Output control device, 42 ... Control rod drive control device, 43 ... Feed water control device, 44 ... Control rod drive Equipment, 45 ... process computer, 46 ... neutron flux monitoring equipment, 47 ... neutron flux detector, 48 ... temperature rise rate setting part, 49 ... interlock signal generation part

Claims (12)

Natural circulation in which a coolant ascending channel and descending channel are formed inside the reactor pressure vessel, and the coolant is circulated by the density difference between the coolant in the ascending channel and the coolant in the descending channel. In a nuclear reactor system having a system,
An output control unit for generating a control rod operation signal for extracting and inserting the control rod inside the reactor pressure vessel based on the reactor water temperature change rate;
A water supply control unit that generates a feed water flow rate to the reactor pressure vessel and a waste water flow rate signal from the reactor based on a reactor water level signal detected from the natural circulation system;
A process calculation unit that supervises the output control unit and the water supply control unit;
A reactor water temperature change rate setting function for adjusting the set value of the reactor water temperature change rate based on the fluctuation amount of the reactor water level signal is added to any one of the output control unit, the water supply control unit, or the process calculation unit. Reactor system characterized by that. The reactor water temperature change rate setting function is
When the fluctuation amount of the reactor water level based on the reactor water level signal is large, the set value of the reactor water temperature change rate is reduced,
2. The reactor system according to claim 1, wherein a set value of the reactor water temperature change rate is increased when a fluctuation amount of the reactor water level based on the reactor water level signal is small. The reactor water temperature change rate setting function is
Calculates the maximum amplitude of the frequency range of the reactor water level signal specified by converting Fourier,
When the maximum amplitude is large, lower the set value of the reactor water temperature change rate,
The reactor system according to claim 1, wherein when the maximum amplitude is small, the set value of the reactor water temperature change rate is increased. Natural circulation in which a coolant ascending channel and descending channel are formed inside the reactor pressure vessel, and the coolant is circulated by the density difference between the coolant in the ascending channel and the coolant in the descending channel. In a nuclear reactor system having a system,
Output control for generating a control rod operation signal for extracting and inserting a control rod inside the reactor pressure vessel based on a reactor water temperature change rate and a reactor pressure signal indicating the pressure inside the reactor pressure vessel And
A water supply control unit that generates a feed water flow rate to the reactor pressure vessel and a waste water flow rate signal from the reactor based on a reactor water level signal detected from the natural circulation system;
A process calculation unit that supervises the output control unit and the water supply control unit;
Reactor water temperature change rate setting function that receives at least the reactor pressure signal and the temperature signal of the core inlet inside the reactor pressure vessel as input, and determines the set value of the reactor water temperature change rate according to a previously stored function Is added to any one of the output control unit, the water supply control unit, and the process calculation unit. The previously stored function is:
The higher the reactor pressure based on the reactor pressure signal, the higher the temperature change rate set value,
5. The nuclear reactor system according to claim 4, wherein the reactor system function is such that the temperature change rate set value becomes higher as the temperature at the core inlet is lower based on the temperature signal at the core inlet. Natural circulation in which a coolant ascending channel and descending channel are formed inside the reactor pressure vessel, and the coolant is circulated by the density difference between the coolant in the ascending channel and the coolant in the descending channel. In a nuclear reactor system having a system,
Based on the reactor water temperature change rate and the reactor pressure signal indicating the pressure inside the reactor pressure vessel, an output for generating a control rod operation signal for extracting and inserting the control rod inside the reactor pressure vessel A control unit;
A water supply control unit that generates a feed water flow rate to the reactor pressure vessel and a waste water flow rate signal from the reactor based on a reactor water level signal detected from the natural circulation system;
A process calculation unit that supervises the output control unit and the water supply control unit;
When the fluctuation amount of the reactor water level signal is larger than a preset value, a function of outputting a control rod insertion signal selected in advance is any of the output control unit, the water supply control unit, or the process calculation unit. A nuclear reactor system characterized by the addition of crab. Natural circulation in which a coolant ascending channel and descending channel are formed inside the reactor pressure vessel, and the coolant is circulated by the density difference between the coolant in the ascending channel and the coolant in the descending channel. In a nuclear reactor system having a system,
Output control for generating a control rod operation signal for extracting and inserting a control rod inside the reactor pressure vessel based on a reactor water temperature change rate and a reactor pressure signal indicating the pressure inside the reactor pressure vessel And
A water supply control unit that generates a feed water flow rate to the reactor pressure vessel and a waste water flow rate signal from the reactor based on a reactor water level signal detected from the natural circulation system;
A process calculation unit that supervises the output control unit and the water supply control unit;
When the amount of fluctuation of the reactor water level signal is larger than a preset value, a function of outputting a control rod drive inhibition signal is added to any of the output control unit, the water supply control unit, or the process calculation unit Reactor system characterized by that. Natural circulation in which a coolant ascending channel and descending channel are formed inside the reactor pressure vessel, and the coolant is circulated by the density difference between the coolant in the ascending channel and the coolant in the descending channel. In a nuclear reactor system having a system,
Output control for generating a control rod operation signal for extracting and inserting a control rod inside the reactor pressure vessel based on a reactor water temperature change rate and a reactor pressure signal indicating the pressure inside the reactor pressure vessel And
A water supply control unit that generates a feed water flow rate to the reactor pressure vessel and a waste water flow rate signal from the reactor based on a reactor water level signal detected from the natural circulation system;
A process calculation unit that supervises the output control unit and the water supply control unit;
Function The reactor water level signal and converts Fourier calculates the maximum amplitude of the frequency range specified, if the maximum amplitude is larger than the set value that is set in advance, for outputting an insertion signal preselected control rod Is added to any one of the output control unit, the water supply control unit, and the process calculation unit. Natural circulation in which a coolant ascending channel and descending channel are formed inside the reactor pressure vessel, and the coolant is circulated by the density difference between the coolant in the ascending channel and the coolant in the descending channel. In a nuclear reactor system having a system,
Output control for generating a control rod operation signal for extracting and inserting a control rod inside the reactor pressure vessel based on a reactor water temperature change rate and a reactor pressure signal indicating the pressure inside the reactor pressure vessel And
A water supply control unit that generates a feed water flow rate to the reactor pressure vessel and a waste water flow rate signal from the reactor based on a reactor water level signal detected from the natural circulation system;
A process calculation unit that supervises the output control unit and the water supply control unit;
Calculates the maximum amplitude of the frequency range of the reactor water level signal specified by converting Fourier, the maximum when the amplitude is greater than the set value set in advance, the output function of outputting a control rod drive inhibit signal A nuclear reactor system added to any one of a control unit, the water supply control unit, and the process calculation unit. Natural circulation in which a coolant ascending channel and descending channel are formed inside the reactor pressure vessel, and the coolant is circulated by the density difference between the coolant in the ascending channel and the coolant in the descending channel. In a nuclear reactor system having a system,
Output control for generating a control rod operation signal for extracting and inserting a control rod inside the reactor pressure vessel based on a reactor water temperature change rate and a reactor pressure signal indicating the pressure inside the reactor pressure vessel And
A water supply control unit that generates a feed water flow rate to the reactor pressure vessel and a waste water flow rate signal from the reactor based on a reactor water level signal detected from the natural circulation system;
A process calculation unit that supervises the output control unit and the water supply control unit;
At least the reactor pressure signal and the temperature signal at the core inlet inside the reactor pressure vessel are used to calculate a reactor output set value by a function stored in advance, and based on the detection of the neutron flux inside the reactor pressure vessel When the furnace output signal exceeds the furnace output set value, a function of outputting a control rod insertion signal selected in advance is added to any one of the output control unit, the water supply control unit, or the process calculation unit. Characteristic reactor system. The previously stored function is:
The higher the reactor pressure based on the reactor pressure signal, the higher the temperature change rate set value,
The reactor system according to claim 10, wherein the reactor system is a function such that the temperature change rate set value increases as the temperature at the core inlet is lower based on the temperature signal at the core inlet. Natural circulation in which a coolant ascending channel and descending channel are formed inside the reactor pressure vessel, and the coolant is circulated by the density difference between the coolant in the ascending channel and the coolant in the descending channel. In a nuclear reactor system having a system,
Output control for generating a control rod operation signal for extracting and inserting a control rod inside the reactor pressure vessel based on a reactor water temperature change rate and a reactor pressure signal indicating the pressure inside the reactor pressure vessel And
A water supply control unit that generates a feed water flow rate to the reactor pressure vessel and a waste water flow rate signal from the reactor based on a reactor water level signal detected from the natural circulation system;
A process calculation unit that supervises the output control unit and the water supply control unit;
At least the reactor pressure signal and the temperature signal at the core inlet inside the reactor pressure vessel are used to calculate a reactor output set value by a function stored in advance, and based on detection of the neutron flux inside the reactor pressure vessel A function of outputting a control rod drive inhibition signal when the furnace output signal exceeds the furnace output set value is added to any one of the output control unit, the water supply control unit, or the process calculation unit. Reactor system.

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