JPH11211886A - Recovering method after full closure of main steam isolation valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the excessive fluctuations of reactor pressure and reactor water level, to take the pressure equalizing action of a main steam pipe without disturbance, to reduce the load of an operating operator and to take a recovering action itself quickly and surely. SOLUTION: In the recovering method after a main steam isolation valve 2 is fully closed, a main steam relief safety valve 3 is automatically opened when the pressure of a reactor 1 rises to the operating pressure of the main steam relief safety valve 3 or when the water level of the reactor 1 rises to the prescribed upper limit value, and the main steam relief safety valve 3 is automatically closed when the pressure of the reactor 1 is lowered to the operating pressure lower limit value of the main steam relief safety valve 3 or when the water level of the reactor 1 is lowered to the prescribed lower limit value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recovery method after a main steam isolation valve is fully closed in an improved boiling water nuclear power plant.

[0002]

2. Description of the Related Art FIG. 5 shows main reactor parameters and behavior of a main steam isolation valve (hereinafter referred to as ΔSIV) after fully closed. That is, when the ΜSIV fully closed event occurs, the behavior of the nuclear power plant is such that the reactor scram is generated by the ΜSIV being fully closed as shown in FIG. 5, and the reactor pressure rises and the reactor water level decreases. Occur. When the reactor pressure rises and the main steam relief valve (hereinafter referred to as SRV) reaches the reactor pressure high set value,
The SRV performs a valve opening operation to suppress the reactor pressure. When the reactor pressure rises above the reactor pressure set value, the turbine bypass valve (hereinafter referred to as ΤBV) opens automatically.

[0003] The restoring operation is performed as a first step by the SR
The V repeatedly opens and closes and discharges energy stored in the reactor to the suppression pool, while suppressing an increase in the reactor pressure. In the meantime, the coolant in the reactor is circulated only by the coolant recirculation pump, and is not injected from the water supply pump, so that the coolant inside the reactor is not subcooled by the decay heat generated when the reactor is stopped Then, since the coolant expands, the reactor water level gradually rises.

When the reactor pressure and the reactor water level are sufficiently suppressed by repeating the above-mentioned opening and closing of the SRV, the second stage of the recovery operation is to open the equalization valve of the main steam pipe as the equalization operation of the main steam pipe. By operating the valve, ΜSIV
The main recovery operation is to equalize the reactor side and turbine side isolated by closing the valve, and to open the ΜSIV after the equalization is completed.

Hereinafter, a conventional mechanism of a recovery method after the main steam isolation valve is fully closed will be described with reference to FIGS. 6 and 7A and 7B. FIG. 6 is a schematic configuration diagram showing a boiling water nuclear power plant, and FIGS.
It is a sequence diagram which shows the conventional example of RV relief valve function and reactor pressure setting change.

[0006] When the ΜSIV fully closed event occurs, as shown in FIG. 6, the reactor side where the reactor pressure vessel 1 is installed and the turbine side are quickly separated from each other with the ΜSIV2 as a boundary, and the reactor scram is Occur.

[0007] As a first stage of the recovery operation, the isolated reactor pressure vessel 1 continues to generate steam while the cooling water temperature is high, and the reactor pressure continues to rise. The pressure in the reactor pressure vessel 1 is released to the suppression pool 4 by using the relief valve function of the SRV 3 to release the increased pressure in the reactor, thereby suppressing the reactor pressure.

Here, regarding the valve opening operation of the SRV3,
As shown in the sequence diagram of FIG. 7 (A), the operation is performed by automatic opening when the reactor pressure reaches the SRV operation set value with the increase of the reactor pressure, or by manual opening operation determined by the operator. Has become. During the SRV opening operation, the reactor water level rises temporarily due to swelling. However, if the SRV 3 is opened for a long time, the reactor water level is discharged along with the discharge of the reactor coolant to the suppression pool 4. Gradually decreases, so when opening and closing the SRV3,
The reactor water level is adjusted such that the reactor water level does not reach the level at which the feed water pump 5 trips and the level at which the emergency core cooling system pump (ECCS pump) operates.

In the pressure equalization operation of the main steam pipe as the second stage of the recovery operation, the condenser 6 is kept in a vacuum state in order to prevent leakage of radioactive substances on the turbine side.
ΜWhen the turbine side is isolated after the SIV is fully closed, the pressure on the turbine side rapidly decreases. Further, when the reactor pressure rises above the reactor pressure set value, the ΤBV 7 opens automatically and a line directly connected to the condenser 6 is formed, so that the turbine side becomes negative pressure. As a result, a large pressure difference occurs between the reactor side and the turbine side.

As described above, if the ΔSIV2 has a differential pressure greater than the system design value before and after the ΔSIV2, the valve opening operation cannot be performed. Therefore, after sufficiently suppressing the reactor pressure and the reactor water level, the pressure equalizing valve 8 is opened to equalize the pressure on the reactor side and the turbine side, and the ΜSIV2 is fully opened.

When equalizing the pressure on the reactor side and the turbine side, in order to prevent automatic opening of the ΤBV7,
The reactor pressure setting will be changed to the upper limit. This is shown in the interlock diagram of FIG. As shown in FIG. 7 (B), in the manual mode, the operator continuously presses and sets the push button (PB), and in the following mode, a predetermined pressure is applied as a bias to the nuclear pressure value. Value is added and set.

In FIG. 6, the steam generated in the reactor pressure vessel 1 passes through the SRV 3 and the ＩＶSIV 2 inserted in the main steam pipe 9, and the flow rate thereof is controlled by a steam control valve 10 so that the steam turbine 11 To be supplied to the rotation of the steam turbine 11. Thereby, the steam turbine 11
Is directly driven to generate electric power.

[0013]

However, in the above-mentioned conventional restoring method after the main steam isolation valve is fully closed, when the SRV 3 is operated in accordance with the increase in the reactor pressure, it operates only by monitoring the present reactor pressure. When the SRV 3 starts the opening operation, the reactor pressure sharply decreases, and the reactor water level sharply rises due to the swelling effect. Therefore, if the SRV 3 is opened in a state where the reactor water level is high, there is a possibility that the reactor water level at which the feedwater pump 5 shown in FIG. 6 trips will be reached.

If the SRV 3 is open for a long time, the reactor water level will rapidly decrease due to the discharge of the reactor coolant to the suppression pool 4 and the stop of swelling during the SRV valve closing operation. This may lead to a reactor water level at which the emergency core cooling system pump operates.

Further, in order to equalize the isolated reactor side and the turbine side, in order to prevent the opening operation of the ΔBV7 which hinders the equalizing operation, it is necessary to change the reactor set pressure to the upper limit value. However, at present, since the pressure set value must be continuously changed manually, it takes time, and as a result, one operator is required.

Even if the reactor pressure setting is changed to the upper limit, if the reactor pressure rises higher than the set value,
Since the BV 7 is opened, the pressure is released even when the equalizing operation of the main steam pipe 9 is performed, which hinders the recovery operation. As a result, a long recovery time is required.

The present invention has been made in view of the above circumstances, and suppresses excessive fluctuations in reactor pressure and reactor water level during a recovery operation in the event of a main steam isolation valve fully closed event. An object of the present invention is to provide a recovery method after a main steam isolation valve is fully closed, which enables a pressure equalization operation of a steam pipe to be performed without disturbance, reduces a burden on an operator, and promptly and reliably performs a recovery operation itself. And

[0018]

In order to solve the above-mentioned problems, the invention according to claim 1 is an invention in which a main steam isolation valve installed in a main steam pipe so as to isolate a reactor side and a turbine side is provided. When a closing event occurs, after opening and closing the main steam release safety valve to release the energy stored in the reactor, in the restoration method after the main steam isolation valve is fully closed, which equalizes the main steam pipe, While the pressure of the reactor rises to the main steam relief safety valve operating pressure or when the water level of the reactor rises to a predetermined upper limit, the main steam relief safety valve is automatically opened, while the pressure of the reactor is The main steam release safety valve is automatically closed when the operating pressure lower limit value of the main steam release safety valve or the water level of the reactor falls to a predetermined lower limit value.

According to a second aspect of the present invention, when a main steam isolation valve installed in a main steam pipe is fully closed so that the reactor side and the turbine side can be isolated, the main steam release safety valve is opened and closed. After releasing the energy stored in the reactor,
In the method for restoring the main steam isolation valve after fully closing the main steam pipe for equalizing the main steam pipe, in addition to the opening and closing conditions of the main steam release safety valve due to the reactor pressure high, the main steam isolation valve may be closed when the main steam isolation valve is fully closed. A high and low set value of a water level at which the relief safety valve operates is set within a water level at which the water supply pump for supplying water to the reactor trips and a water level at which the emergency core cooling system pump operates.

According to a third aspect of the present invention, when the main steam isolation valve installed in the main steam pipe is fully closed so that the reactor side and the turbine side can be isolated, the main steam release safety valve is opened and closed. After releasing the energy stored in the reactor,
In the method for restoring the main steam isolation valve after the main steam isolation valve is fully closed for performing the equalization operation of the main steam pipe, when the main steam isolation valve is fully closed, the relief valve function operating pressure set value of the main steam relief safety valve is set to the atomic pressure. It is characterized in that it is set to a value lower than the relief valve function operating pressure set value of the main steam relief safety valve due to the furnace pressure.

According to a fourth aspect of the present invention, when a main steam isolation valve installed in a main steam pipe so that the reactor side and the turbine side can be isolated from each other, a main steam release safety valve is opened and closed. After releasing the energy stored in the reactor,
In the restoration method after the main steam isolation valve is fully closed, which performs the equalization operation of the main steam pipe, the pressure setting of the reactor is automatically changed to an upper limit value when the main steam isolation valve is fully closed. And

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a control circuit diagram for opening and closing a main steam release safety valve in a first embodiment of a recovery method after the main steam isolation valve is fully closed according to the present invention, and FIG. 2 is an interlock diagram of FIG. . The configuration of the boiling water nuclear power plant applied in the first embodiment is the same as that in FIG. 6 and will be described using the same reference numerals.

As shown in FIG. 1, the steam generated in the reactor pressure vessel 1 passes through the SRV 3 and the ΜSIV 2 inserted in the main steam pipe 9, and its flow rate is controlled by a steam control valve (not shown). The steam is guided to a turbine and used for rotation of the steam turbine. Thereby, the generator directly connected to the steam turbine is driven to generate electric power.

Further, the reactor pressure vessel 1 is provided with a pressure detector 13 for detecting the vapor pressure thereof and a water level detector 14 for detecting a water level in the reactor pressure vessel 1.

In this embodiment, an SRV opening / closing control circuit 15 for controlling the opening / closing of the SRV 3 is provided.
The switching control circuit 15 controls the opening and closing of the SRV 3 in order to release the pressure in the reactor pressure vessel 1 to the suppression pool 4 when the fully closed event of the ΜSIV 2 occurs.

The SRV switching control circuit 15 has a plurality of comparators 16a to 16e.
6c and 16e compare the output signal from the pressure detector 13 with the set value and output a signal when the output signal exceeds the set value, and the comparators 16b and 16d output the signal from the water level detector 14 Outputs a signal when the output signal exceeds the set value as compared with the set value.

As shown in FIGS. 1 and 2, the comparator 16
The set value of a is a value (reactor pressure A) lower than the SRV3 relief valve function operating pressure set value due to the reactor pressure high,
The set value of the comparator 16c is SRV3 based on the reactor pressure high.
Of the relief valve function operating pressure (reactor pressure high)
The set value of the comparator 16e is the lower limit value of the relief valve function operating pressure (reactor pressure AA) of the SRV3. Further, the comparator 16
The set value of b is a predetermined upper limit of the reactor water level (reactor water level B), and the set value of the comparator 16d is a predetermined lower limit of the reactor water level (reactor water level BB).

The SRV opening / closing control circuit 15 has a judging section 17, and this judging section 17 has an OR circuit 18, an AND circuit 19,
An OR circuit 18 including an OR circuit 20 and an OR circuit 21
Outputs a signal to the AND circuit 19 when a signal is output from either of the comparators 16a or 16b. When both the 時 に SIV fully closed signal and the output signal of the OR circuit 18 are input to the AND circuit 19,
Output the signal.

In addition to the signal from the AND circuit 19, a signal from the comparator 16c or a signal for manual opening is input to the OR circuit 20, and when one of these signals is output, the signal is output to the SRV3. Outputs open signal. The OR circuit 21 outputs a close signal to the SRV 3 when a signal is output from one of the comparator 16d and the comparator 16e.

Next, a first embodiment of a recovery method after the main steam isolation valve is fully closed according to the present invention will be described.

When the fully closed event of SIV2 occurs, FIG.
As shown in FIG. 2 and FIG. 2, the ΜSIV fully closed signal is input to the AND circuit 19, and the pressure in the reactor pressure vessel 1 is lower than the SRV 3 relief valve function operating pressure set value due to the reactor pressure high (reactor pressure A ) To the comparator 16a
Or the water level of the reactor pressure vessel 1 rises to a predetermined upper limit (reactor water level B) and the comparator 16b
Output from the OR circuit 18, AND
An open signal is output to the SRV3 via the circuit 19 and the OR circuit 20, and the SRV3 automatically performs a valve opening operation. As a result, it is possible to prevent the reactor water level at which the feedwater pump is tripped due to the reactor pressure rise and the water level rise due to swelling occurring.

On the other hand, the reactor pressure decreases to the operating pressure lower limit value of the SRV 3 (reactor pressure AA) and a signal is output from the comparator 16d, or the water level of the reactor pressure vessel 1 is reduced to a predetermined lower limit value (reactor pressure AA). When the signal has been output from the comparator 16e after falling to the reactor water level BB), the SR
A closing signal is output to V3, and SRV3 automatically performs a valve closing operation. This makes it possible to suppress fluctuations in the reactor pressure and the reactor water level.

In this embodiment, the predetermined upper limit of the water level (reactor water level B), which is the set value of the comparator 16b, is set to a value lower than the water level at which the water supply pump trips, and the setting of the comparator 16d is set. The predetermined lower limit of the water level (reactor water level BB) is set to a value higher than the water level at which the emergency core cooling system pump operates, that is, the water pump at which the SRV 3 operates when the SIV 2 is fully closed is set to the water supply pump. Is set within the water level at which the emergency core cooling system pump operates from the water level at which the trip occurs.

Therefore, it is possible to prevent the reactor water level from reaching the water level at which the feed water pump trips and the water level at which the emergency core cooling system pump operates, and to suppress the fluctuation of the reactor water level. Recovery operation after fully closed can be performed smoothly.

Further, in this embodiment, by setting the set value of the comparator 16a to a value (reactor pressure A) lower than the set value of the SRV3 relief valve function operating pressure due to the reactor pressure high, the ΔSIV fully closed signal , The pressure in the reactor is reduced at a timing earlier than the opening operation of the SRV 3 due to the normal reactor pressure high, and it is possible to prevent the reactor pressure from rising above the reactor pressure set value.

As a result, the valve opening operation of the TBV 7 caused by the reactor pressure reaching the reactor pressure set value can be suppressed, and when the equalizing operation of the main steam pipe 9 is performed, the reactor TBV even if pressure rises
The obstruction of the equalizing operation by the opening of the valve 7 can be prevented.

In the recovery method after the main steam isolation valve is fully closed according to the present embodiment, the main parameters and the behavior of the main valve are compared with the conventional main parameters and the behavior of the main valve shown in FIG. Considering the occurrence of the ΜSIV fully-closed event, the SRV3 becomes faster than the conventional SRV due to the reactor pressure A acting only when the ΜSIV is fully closed.
Opens and begins to throttle reactor pressure.

At the time of the first SRV operation, since the pressure rise is considerably large, when the reactor pressure reaches the upper limit of the reactor pressure set value changed when the ΜSIV fully closed signal is input, the ΤBV is opened. After that, since the rate of increase of the reactor pressure becomes slower, the reactor pressure is reduced by the reactor pressure A, which is lower than the reactor pressure set value. Operation can be suppressed.

The opening and closing operation of the SRV 3 can be performed by adjusting the reactor water level. Therefore, when the water level is rising, the reactor water level (water level at which the feedwater pump trips) taking into account the rising of the water level due to swelling is considered. ) Since the SRV 3 performs the valve-opening operation at the lower reactor water level B, it is possible to prevent the feed water pump from reaching the reactor water level that trips and before reaching the water level at which the emergency core cooling system pump operates. Since the SRV 3 performs the closing operation according to the reactor water level BB, it is possible to prevent the reactor water level from reaching the level at which the emergency core cooling system pump operates.

In this embodiment, since the SRV 3 is opened and closed by monitoring both the reactor pressure and the reactor water level, one operation time of the SRV 3 is shortened.
It is considered that the number of times of opening and closing of V3 increases.

FIG. 3 is a circuit diagram for automatically changing a reactor pressure set value in a second embodiment of the recovery method after the main steam isolation valve is fully closed according to the present invention, and FIG. 4 is an interlock diagram of FIG. is there. The same parts as those in the first embodiment include:
The description is given with the same reference numerals.

As shown in FIGS. 3 and 4, the pressure signal in the furnace obtained by the pressure detector 13 is output to the adder 22 and also to the subtractor 23. Adder 2
2 is to add a predetermined pressure signal as a bias to the pressure signal in the reactor when the reactor pressure setting is the follow-up mode,
Is output to the pressure setting circuit 25 via Further, in the case of the manual mode, the driving operator presses a push button (PB).
Is pressed, and the pressure setting signal is output to the pressure setting circuit 25 via the contact 26.

Further, the subtractor 23 obtains a difference between the pressure signal in the furnace and the pressure signal from the pressure setting circuit 25, and outputs a closing signal to the 信号 BV7 via the pressure regulator 27 when the difference is-. ΤBV7 is closed. On the other hand, when the result of the subtraction by the subtractor 23 is +, an open signal is output to the ΤBV7 via the pressure regulator 27 to open the ΤBV7.

When the ΜSIV fully closed signal is received, the contact 28 is closed and the contacts 24 and 26 are opened, the reactor pressure setting is changed to the upper limit value via the pressure setting circuit 25, and the subtractor 23 Results in-. As a result, the closing signal passes through the pressure regulator 27 and becomes {BV7
ΤBV7 is closed.

Therefore, in this embodiment, when the ΜSIV fully closed signal is input, the reactor pressure setting is automatically and instantaneously changed to the upper limit value. Therefore, the reactor pressure in the first stage of the recovery operation after the MSIV is fully closed is set. Unless the reactor pressure rises above the reactor pressure set value even during an operation for suppressing fluctuations in the reactor water level, unnecessary opening operation of the TBV 7 can be suppressed. Also, when the pressure equalizing operation of the main steam pipe 9 is started in the second stage of the recovery operation, the TBV 7
Can be prevented from opening.

As described above, according to the present embodiment, when the 圧 力 SIV fully closed event occurs, the reactor pressure set value is automatically and instantaneously changed to the upper limit value, so that the timing of suppressing the valve opening operation of ΤBV7 becomes faster. Accordingly, the equalizing operation of the main steam pipe 9 can be performed promptly, and the restoring operation can be performed quickly and reliably.

[0048]

As described above, according to the first aspect of the present invention,
According to the described invention, in addition to reactor pressure monitoring,
When fully closed, the SRV can automatically open and close even when the reactor water level fluctuates, and it is possible to automatically suppress fluctuations in the reactor pressure and the reactor water level.

According to the second aspect of the present invention, when the SIV is fully closed, the SRV can be opened and closed even if the reactor water level fluctuates. By setting the water level within the water level at which the core cooling system pump operates, it is possible to prevent the water level at which the water supply pump trips and the water level at which the emergency core cooling system pump operates to be reached.

According to the third aspect of the present invention, when the SIV is fully closed, the SRV is operated within the reactor pressure setting upper limit by operating the SRV so that the SRV opening operation pressure is within the reactor pressure setting upper limit. It is possible to suppress the disturbance, prevent disturbance due to the TBV opening operation, and perform a smooth and quick recovery operation.

According to the fourth aspect of the present invention, when the ΜSIV fully closed event occurs, the reactor pressure setting is instantaneously changed to the upper limit value.
Can be suppressed, and unnecessary TBV opening operation can be prevented even when pressure equalizing operation of the main steam pipe is performed.

[Brief description of the drawings]

FIG. 1 is a control circuit diagram for opening and closing a main steam release safety valve in a first embodiment of a recovery method after a main steam isolation valve is fully closed according to the present invention.

FIG. 2 is an interlock diagram of FIG.

FIG. 3 is a circuit diagram for automatically changing a reactor pressure set value in a second embodiment of the recovery method after the main steam isolation valve is fully closed according to the present invention.

FIG. 4 is an interlock diagram of FIG. 3;

FIG. 5 is a timing chart showing main reactor parameters and main valve behavior after the main steam isolation valve is fully closed.

FIG. 6 is a schematic configuration diagram showing a boiling water nuclear power plant.

FIGS. 7A and 7B are sequence diagrams showing a conventional example of a conventional SRV relief valve function and a change in reactor pressure setting.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reactor pressure vessel 2 Main steam isolation valve (主 SIV) 3 Main steam relief safety valve (SRV) 4 Suppression pool 5 Feedwater pump 6 Condenser 7 Turbine bypass valve (ΤBV) 8 Equalization valve 9 Main steam pipe 10 Steam control valve 11 Steam turbine 12 Generator 13 Pressure detector 14 Water level detector 15 SRV switching control circuit 16a to 16e Comparator 17 Judgment unit 18 OR circuit 19 AND circuit 20 OR circuit 21 OR circuit 22 Adder 23 Subtractor 24 Contact 25 Pressure setting circuit 26 contacts 27 pressure regulator 28 contacts

Claims (4)

[Claims] When a main steam isolation valve installed in a main steam pipe is fully closed so that a reactor side and a turbine side can be isolated from each other, a main steam release safety valve is opened and closed to accumulate in the reactor. After releasing the energy, the pressure in the reactor increases to the operating pressure of the main steam release safety valve, or the reactor While the main steam release safety valve is automatically opened when the water level of the reactor rises to a predetermined upper limit, the reactor pressure has decreased to the main steam release safety valve operating pressure lower limit value or the reactor water level to a predetermined lower limit value. A method for automatically closing the main steam release safety valve when the main steam isolation valve is fully closed. 2. In the event that a main steam isolation valve installed in a main steam pipe so that the reactor side and the turbine side can be isolated from each other occurs, a main steam release safety valve is opened and closed to accumulate in the reactor. In the method for restoring the main steam isolation valve after the main steam isolation valve is fully closed after releasing the energy that has been released, the main steam isolation valve is opened and closed due to the reactor pressure high, and the main steam isolation safety valve is opened and closed. When the valve is fully closed, the main steam release safety valve operates at a high or low water level set within a water level at which a water supply pump for supplying water to the reactor trips and a water level at which an emergency core cooling system pump operates. Recovery method after the main steam isolation valve is fully closed. 3. When a main steam isolation valve installed in a main steam pipe so that the reactor side and the turbine side can be isolated from each other, a main steam release safety valve is opened and closed to accumulate in the reactor. In the restoring method after the main steam isolation valve is fully closed after performing the pressure equalizing operation of the main steam pipe after releasing the energy that has been released, when the main steam isolation valve is fully closed, the relief function of the main steam relief safety valve is activated. A recovery method after the main steam isolation valve is fully closed, wherein a pressure set value is set to a value lower than a relief valve function operating pressure set value of the main steam relief safety valve due to the reactor pressure high. 4. When a main steam isolation valve installed in a main steam pipe is fully closed so that the reactor side and the turbine side can be isolated from each other, a main steam release safety valve is opened and closed to accumulate in the reactor. In the recovery method after the main steam isolation valve is fully closed after performing the equalizing operation of the main steam pipe after releasing the energy that has been released, when the main steam isolation valve is fully closed, the pressure setting of the reactor is automatically set to an upper limit. Recovery method after fully closing the main steam isolation valve, characterized by changing to a value.