JPH0833774B2 - Reactor pressure control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a reactor pressure control device for controlling the reactor pressure of a boiling water nuclear power plant.

(Prior Art) Conventionally, in order to stop a nuclear reactor of a boiling water nuclear power plant, first, a main stop valve provided in a main steam pipe from the nuclear reactor to the turbine is fully closed. Next, using the reactor pressure control device, the bypass valve provided in the steam pipe that bypasses the turbine from the reactor to the condenser is controlled to send the main steam from the reactor directly to the condenser. The reactor pressure was gradually reduced from the rated pressure and the control rod was operated to shut down the reactor.

At this time, the pressure vessel of the nuclear reactor has a restriction of mechanical thermal stress, and a rapid change of the reactor water temperature is not preferable.

For this reason, the reactor pressure control device performs pressure reduction control while keeping the rate of change of reactor water temperature within a certain range.

(Problems to be Solved by the Invention) However, the conventional reactor pressure control device uses a Bourdon tube and a differential transformer as a pressure detector for detecting the reactor pressure, and is linear near the rated pressure. Since it has the detection characteristics of, it has a non-linear detection characteristic in the low pressure region of 10 kg / cm ² g or less. Therefore, the reactor pressure in the low pressure region cannot be detected correctly, and
Below kg / cm ² g is out of the control range, the decompression control must be performed manually by the operator. However, in the low pressure region, the amount of operation of the bypass valve is large, and the manual operation by the operator for a long time is a heavy burden, and there is a problem that it is difficult to perform depressurization control to keep the rate of change of the reactor water temperature within a certain range. .

Therefore, the present invention provides a reactor pressure control device capable of automatically performing decompression control while keeping the rate of change of reactor water temperature within a certain range even in a low pressure region where the reactor pressure is 10 kg / cm ² g or less. The purpose is to do.

[Structure of the Invention] (Means for Solving Problems) The present invention provides a bypass valve opening jack and a low pressure detector for detecting the reactor pressure in order to correctly detect the reactor pressure in a low pressure region. A non-linear compensation element that corrects the non-linear characteristic of the pressure region to a linear characteristic, and the pressure for calculating the reactor pressure target value at predetermined time intervals based on the relationship between the reactor water temperature and the saturated vapor pressure by inputting the reactor water temperature. A target value calculation means is provided to control the bypass valve using the bypass valve opening jack so that the corrected reactor pressure from the non-linear compensation element follows the reactor pressure target value calculated by the pressure target value calculation means. It is a thing.

(Operation) As a result, even in the low pressure region where the reactor pressure is 10 kg / cm ² g or less, the decompression control can be automatically performed while keeping the rate of change of the reactor water temperature within a certain range.

(Embodiment) FIG. 1 shows a system configuration in which a reactor pressure control device according to an embodiment of the present invention is applied to a boiling water nuclear power plant.

Steam from the nuclear reactor 1 passes through a main steam pipe 2, and one of them is sent to a steam turbine 5 directly connected to a generator 4 via a main stop valve 3. The other is sent to the condenser 7 via the turbine bypass valve 6. The outlet steam of the steam turbine 5 is cooled by the condenser 7 and becomes condensed water, which passes through the condensate pipe 8 and is sent to the feed water heater 10 by the condensate pump 9. Condensed water is heated by the feed water heater 10 and sent to the reactor 1 again by the feed water pump 11.

On the other hand, the reactor pressure and the reactor water temperature in the reactor 1 are detected by the pressure detector 12 and the temperature detector 13, respectively. The reactor pressure P from the pressure detector 12 is input to a non-linear compensating element 16 for correcting the reactor pressure P via a sampler 15A which inputs a signal for each sampling period in the reactor pressure control device 14. The reactor water temperature T from the temperature detector 13 is also input to the target pressure value calculating means 17 via the sampler 15A in the reactor pressure control device 14. This pressure target value calculation means 17 is a function generator 18 for calculating a target pressure change rate PD from the input reactor water temperature T, and a sampler 15A.
When sampling starts, that is, the reactor pressure P at the start of control is set as an initial value, and the target pressure change rate PD calculated by the function generator 18 is added to this for each sampling cycle, and the addition result is the reactor pressure target value. It consists of an integrator 19 that outputs as PA. This reactor pressure target value PA and the corrected reactor pressure PC from the above-mentioned non-linear compensation element 16 are input to the adder 20, and the deviation thereof is linked with the A control element 21, the B control element 22 and the sampler 15A. By-pass valve controller 2 via sampler 15B which outputs a signal for each sampling cycle
It is output to 3 as a valve opening request signal a. Where A
The control element 21 is a bypass valve control device for the deviation from the adder 20.
For converting the valve opening request signal a to 23,
The B control element 22 is for providing a predetermined limit when the change is large or not within a certain range.
The bypass valve opening jack opening setting device 24 in the bypass valve control device 23 inputs the valve opening request signal a from the reactor pressure control device 14 and receives the valve opening target value a ′ of the bypass valve 6.
For calculating. The valve opening target value a'calculated by the bypass valve opening jack opening setter 24 is added together with the actual valve opening b'from the C control element 25 to which the valve opening signal b of the bypass valve 6 is input. Input to the container 26. The adder 26 is for taking a deviation between the input valve opening target value a'and the actual valve opening b '.
The deviation is the bypass valve opening jack opening controller
The signal is input to 27, becomes a control signal c, and is output to the bypass valve 6.

With the above configuration, when the nuclear reactor 1 is operating normally, the bypass valve 6 is closed and the main stop valve 3 is open. As a result, the main steam from the reactor 1 is fed into the main steam pipe 2
, The steam turbine 5 is driven through the main stop valve 3 and the generator 4 is rotated to obtain the generator output.

When shutting down the reactor 1 from this state, the generator 4 and the system are shut off, the main stop valve 3 is closed to shut off the supply of main steam to the steam turbine 5, and the steam turbine 5 is shut down.

Next, by using a conventional reactor pressure control device (not shown), the bypass valve 6 is gradually opened and the main steam from the reactor 1 is sent to the condenser 7 to keep the rate of change of the reactor water temperature T within a certain range ( −55 ° C / H
Keep the following) and reduce the pressure to the rated pressure of 10 kg / cm ² g.

Now, when the reactor pressure P reaches 10 kg / cm ² g, the reactor pressure control device 14 is started. Then, the sampler 15A
Inputs the reactor pressure P from the pressure detector 12 and the reactor water temperature T from the temperature detector 13 into the reactor pressure control device at a predetermined sampling period. As shown in FIG. 2, the function generator 18 in the pressure target value calculation means 17 determines the current reactor water temperature T ₁
Input, and set the reactor water temperature T ₂ after the sampling period Δt seconds to T ₂
= T ₁ + Δt × (target temperature drop rate). further,
From the relationship between the reactor water temperature T and the saturation pressure of the reactor ₁ , the reactor pressures P ₁ and P ₂ are calculated when the reactor water temperature is T ₁ and T ₂ , and the target pressure change rate
PD is calculated by PD = P ₂ −P ₁ , and this is output to the integrator 19. The integrator 19 sets the reactor pressure P ₁ when the reactor pressure controller 14 is started at time t ₁ as an initial value, adds the input target pressure change rate PD (= P ₂ −P ₁ ), and Target pressure PA
Output as (= P ₂ ).

On the other hand, when the reactor pressure P detected by the pressure detector 12 is 10 kg / cm ² g or less, the non-linear compensation element 16 has non-linear characteristics and the correct reactor pressure cannot be detected. The input reactor pressure P from the pressure detector 12 is linearized, and the corrected reactor pressure PC is output.

The adder 20 outputs the deviation between the pressure target value PA from the integrator 19 and the corrected reactor pressure PC from the nonlinear compensation element 16 to the A control element 21. The A control element 21 converts this into a valve opening request signal a to the bypass valve 6, while the B control element 22 imposes a predetermined limit on this, and the valve opening request signal a is bypassed via the sampler 15B. Output to the control device 23. The bypass valve opening jack opening setting device 24 in the bypass valve opening jack control device 23 calculates the valve opening target value a ′ of the bypass valve 6 based on the valve opening request signal a. The adder 26 inputs this valve opening target value a ′ and the actual valve opening b ′ from the C control element 25, and outputs the deviation thereof to the bypass valve opening jack opening controller 27. Based on this, the bypass valve opening jack opening controller 27 outputs the control signal C to operate the bypass valve 6 to control the main steam sent from the reactor 1 to the condenser 7 via the bypass valve 6, The reactor pressure P is reduced from P ₁ to P ₂ in Δt seconds. As a result, the reactor water temperature T determined by the saturated vapor pressure after Δt seconds can be T ₂ .

Generally, if the reactor water temperature is Tn in the n-th sampling cycle, the target reactor water temperature Tn ₊₁ after Δt seconds is Tn _+1.
= Tn + Δt × (target temperature decrease rate), the reactor pressure Pn _{+ 1} corresponding to the reactor water temperature tn _{+ 1} is calculated, and the target pressure change rate PD is PD = Pn
₊₁ −Pn and set the reactor pressure target value PA And By adjusting the reactor pressure target value PA thus calculated as a target value by the bypass valve 6 and the bypass valve opening jack control device 23, the corrected reactor pressure PC from the non-linear compensation element 16 is feedback-controlled. , Δt seconds later, the reactor water temperature T can be set to Tn ₊₁ .

As described above, according to the present embodiment, in the low pressure region, the pressure reduction control of the reactor can be automatically performed while keeping the rate of change of the reactor water temperature T within a certain range.

In the present embodiment, the pressure reduction control of 10 kg / cm ² g or less was described, but the conventional reactor pressure control device was not used at all, and the pressure reduction control from the rated pressure to 10 kg / cm ² g or less was also performed with this atom. Of course, it is also possible to make the furnace pressure control device 14 carry out.

As described above, according to the present invention, even in the low pressure region of 10 kg / cm ² g or less, the pressure reduction control can be automatically performed while keeping the reactor water temperature change rate within a certain range. It is possible to obtain a reactor pressure control device that greatly contributes to the improvement of the operating rate of the plant by eliminating the long-term depressurization operation by the operator when the reactor is stopped.

[Brief description of drawings]

FIG. 1 is a system configuration diagram in which a reactor pressure control device according to an embodiment of the present invention is applied to a boiling water nuclear power plant, and FIG.
FIG. 3 is an explanatory view of characteristic changes of reactor pressure and reactor water temperature when the plant is stopped, and FIG. 3 is an explanatory view of input / output characteristics of the nonlinear compensation element of FIG. 1 ... Reactor, 2 ... Main steam piping, 3 ... Main stop valve, 4 ...
… Generator, 5 …… Steam turbine, 6 …… Bypass valve, 7
… Condenser, 8 …… Condenser pipe, 9 …… Condensate pump, 10 ……
Water heater, 11 …… Water pump, 12 …… Pressure detector, 13
...... Temperature detector, 14 ...... Reactor pressure control device, 15A, 15b
…… Sampler, 16 …… Nonlinear compensation element, 17 …… Pressure target value calculation means, 18 …… Function generator, 19 …… Integrator, 20,2
6 …… Adder, 21,22,25 …… Control element, 23 …… Bypass valve opening jack controller, 24 …… Bypass valve opening jack opening setter, 27 …… Bypass valve opening jack opening controller.

Claims (1)

[Claims] Claim: What is claimed is: 1. By controlling the opening of a bypass valve provided in a steam pipe that bypasses the turbine to the condenser and bypasses the turbine, keeping the rate of change of the reactor water temperature within a certain range. In a reactor pressure control device that performs depressurization control, a target pressure value calculating means for calculating a target reactor pressure value from the detected reactor water temperature, and a non-linearity for correcting the non-linear characteristics of a pressure detector for detecting the reactor pressure. A compensating element and a bypass valve opening jack control device for controlling the bypass valve according to a deviation between the reactor pressure value corrected by the non-linear compensating element and the reactor pressure target value calculated by the pressure target value calculating means. A reactor pressure control device comprising: