JP2000046994A - Device for preventing pump for reactor coolant purification system from tripping - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a signal for indicating that the difference between flow rates is large and keeps a pump from tripping, by controlling a blow down flow rate in a reactor coolant purification system. SOLUTION: An entrance line 2 of a reactor coolant purification system (CUW) and a reactor feed water line 11 are connected to a reactor pressure vessel 1. A CUW entrance flow meter 15, a regenerative heat exchanger 3, a non-regenerative heat exchanger 4, a CUW pump 5 and a filtration desalter 6 are connected to the CUW entrance line 2 in series. A branch point 30 is placed downstream from the filtration desalter 6. A CUW blow line 7 connected to a waste disposal system and a CUW exit line 8 connected to the reactor feed water 11 are linked to the branch point 30. The regenerative heat exchanger 3, a CUW exit flow meter 9 and the first check valve 10 are connected between the CUW exit line 8 and the reactor feed water line 11. Notably, the second check valve 32 is placed near the branch point 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump trip preventing device for a reactor coolant purification system (hereinafter referred to as "CUW") used in a boiling water nuclear power plant (hereinafter referred to as "BWR plant").

[0002]

2. Description of the Related Art In a BWR plant, when a nuclear reactor is started up and shut down, surplus water in the reactor due to volume expansion of cooling water of a control rod drive system (hereinafter referred to as CRD) and cooling water in heating of a reactor coolant. Occurs. For this reason, CUW
Exhaust water from the nuclear reactor is discharged using a line that discharges to the waste treatment system.

The CUW will be described with reference to FIG. CU
W is also intended to remove impurities in the reactor, and its structure is a reactor pressure vessel (hereinafter referred to as RPV).
1 through the CUW inlet line 2 to draw in the reactor coolant, and the water is cooled through the regenerative heat exchanger 3 and the non-regenerative heat exchanger 4, and is filtered from the discharge side of the CUW pump 5 to a desalination apparatus (hereinafter referred to as CF / CD) ) To 6 to remove impurities in the reactor coolant.

[0004] Thereafter, a branch point is located downstream of CF / CD6.
A line leading to the waste treatment system after 30 (hereinafter CUW)
(Hereinafter, referred to as a blow line 7) and a line (hereinafter, referred to as a CUW exit line 8) leading to a nuclear reactor again. RP
The CUW outlet line 8 reaching V1 is heated by the regenerative heat exchanger 3, and the water is returned to the RPV 1 through the CUW outlet flow meter 9, the check valve 10, and the reactor water supply line 11.

On the other hand, the CUW blow line 7 leading to the waste treatment system passes through the CUW blow down valve 12 and the blow down flow meter 13 to reach the waste treatment system. Incidentally, in FIG.
Is a reactor containment vessel, and 15 is a CUW inlet flow meter.

[0006] Normally, two CUWs are operated.
Is controlled at a constant value by the filtration and desalination apparatus 6. The flow rate control of the CUW blow line 7 is performed by a water supply control system 16 shown in FIG.

Next, the water supply control system will be described with reference to FIG. In the water supply control system 16, the reactor water level 17 and the reactor water level setting device 18 are compared by a comparator 19, and the reactor water level 17 opens and closes the CUW blowdown valve 12 according to the deviation of the reactor water level setting device 18, The flow rate of the CUW blow line 7 is adjusted, and the water level is controlled by the main water level controller 20.

When the reactor water level 17 is controlled by the blowdown flow rate, the turbine bypass valve (not shown) provided in the turbine system that generates a small amount of steam from the RPV 1 is closed, or the steam is discharged from the main turbine. Is not used, the pressure in the RPV 1 when the reactor is started up to a pressure of about 70 kg / cm ² and the pressure in the RPV 1 when the reactor is stopped are about 70 kg / cm ^2.
When the pressure is reduced from kg / cm ² .

In FIG. 4, reference numeral 21 denotes a main controller of the water supply control system 16, 22 denotes a T / D controller of a turbine system, 23 denotes an M / D controller of a miscellaneous drain system, and 24 denotes a reactor coolant. CUW controller for purification system, 25 is also CUW valve opening setting, 26 is CUW similarly
The actual valve opening. A CUW pipe break is detected using a CUW differential flow signal. Here, the difference flow signal of CUW will be described with reference to FIG.

This signal is output from the CUW inlet flow meter 15 by the CU.
W inlet flow signal 27, CUW outlet flow signal 28 from CUW outlet flow meter 9, CUW from CUW blowdown flow meter 13
The W blowdown flow rate signal 29 is input to the difference flow rate detection circuit 31, and a signal obtained by subtracting the CUW outlet flow rate signal 28 and the CUW blowdown flow rate signal 29 from the CUW inlet flow rate signal 27 is used as the difference flow rate.

If the CUW is in a normal state, the flow rate obtained by adding the CUW outlet flow rate signal 28 and the CUW blowdown flow rate signal 29 and the flow rate of the pipe of the CUW inlet line 2 leading from the reactor pressure vessel 1 to the CUW pump 5 (hereinafter referred to as the flow rate) , CUW inlet flow rate) are equal and the difference flow rate signal is 0.

If the CUW has a broken pipe, the flow rate obtained by adding the CUW outlet flow rate and the CUW blowdown flow rate to C
The UW inlet flow differs and a differential flow occurs. For this reason,
The occurrence of the differential flow rate detects a CUW pipe break. That is, when the difference is equal to or larger than the set value, the pump stops due to the large difference flow rate.

[0013]

Normally, the reactor water level is reduced by discharging surplus water due to cooling water injection by CRD.
Since 17 is controlled to be constant, C released to the waste treatment system
The UW blowdown flow rate is about 10 to 20 t / h. Immediately after the reactor becomes critical or when a large water level disturbance is injected by the control rod drive system, the operation of the water supply control system that suppresses the water level disturbance greatly changes the blowdown flow rate.

If the CUW blowdown flow rate exceeds the CUW inlet flow rate, the CUW outlet line 8 between the branch point 30 shown in FIG. Water flows backward. Especially CUW
When one pump 5 is operated, when the reactor water level recovers after the CUW blowdown flow rate exceeds the CUW inlet flow rate, the blowdown flow rate is reduced to reduce the discharge amount of the reactor water for controlling the reactor water level. Decreases below the CUW inlet flow rate.

However, at this time, since the water of the CUW outlet line 8 has been discharged, it must be filled with water.
Due to the water filling of the W outlet line 8, the flow rate is not supplied to the CUW outlet line 8, and the CUW differential flow signal increases,
There is a problem that the CUW pump 5 trips when the pipe break signal is detected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a reactor coolant purification system pump trip prevention device for preventing a pump trip due to a large difference in flow rate caused by an increase in a CUW blowdown flow rate. is there.

[0017]

According to the first aspect of the present invention, a reactor pressure vessel is connected to a reactor coolant purifying system inlet line and a reactor water supply line, and the reactor coolant purifying system inlet line is connected to the reactor coolant purifying system inlet line. Furnace coolant purification system inlet flow meter, regenerative heat exchanger,
A non-regenerative heat exchanger, a reactor coolant purification system pump, and a filter desalination unit are sequentially connected in series, and one of the two branches is formed by using a downstream pipe connected to the furnace or the desalination unit as a branch point. A reactor coolant purification system outlet line is connected, and the other is connected to a reactor coolant purification system blow line. The reactor purification system outlet line is connected to the regenerative heat exchanger, the reactor coolant purification system outlet flow meter, and a reverse flowmeter. A stop valve is connected in series and its downstream side is connected to the reactor water supply line, and the reactor coolant purification system blow line is connected in series with a blowdown valve and a blowdown flow meter, and the downstream side is connected to a waste treatment system. The reactor is characterized in that a second check valve is provided in the reactor coolant purification system outlet line that connects the branch point and the regenerative heat exchanger.

According to the first aspect of the present invention, a CUW blow line and a CUW
A second check valve is installed on the CUW outlet line side from the branch point to the outlet line to the regenerative heat exchanger, preferably near the branch point.

As a result, the CUW blowdown flow rate becomes
In the case where the flow rate exceeds the W inlet flow rate, it is possible to prevent the water from flowing out of the CUW outlet line and prevent the occurrence of the large difference flow rate signal due to the increase in the CUW blowdown flow rate. There is no effect on the differential flow signal used for detecting the CUW pipe breakage, and the pump trip function due to the large CUW differential flow rate due to the pipe breakage is not impaired.

A second aspect of the present invention is a reactor for controlling the flow rate of coolant flowing through the blow line by inputting signals from the reactor coolant purification system inlet flow meter and the blowdown flow meter to a differential flow rate detection circuit. It is characterized by being provided with a blow-down flow rate controller for a coolant purifying system.

According to the second aspect of the present invention, the method of controlling the CUW blowdown flow rate based on the CUW inlet flow rate is to prevent the CUW blowdown flow rate from exceeding the CUW inlet flow rate. Use a CUW blowdown controller using signal deviation.

By adjusting the CUW blowdown flow rate with this controller, it is possible to prevent the occurrence of a large differential flow rate signal due to an increase in the CUW blowdown flow rate. There is no effect on the differential flow signal used for detecting the CUW pipe breakage, and the pump trip function due to the large CUW differential flow rate due to the pipe breakage is not impaired.

According to a third aspect of the present invention, signals from the reactor coolant purifying system inlet flow meter and the blowdown flow meter are input to a difference flow rate detection circuit, and a difference caused by the generated signal from the difference flow rate detection circuit is set. An alarm circuit for generating an alarm when the value exceeds the value is provided.

According to the third aspect of the present invention, a deviation between the CUW inlet flow signal and the CUW blowdown flow is used to generate an alarm in a state where water is discharged (discharged) at the CUW outlet line. An alarm is generated when the value exceeds a certain set value. As a result, an increase in the CUW blowdown flow rate can be detected, and generation of a large differential flow rate signal due to the increase in the CUW blowdown flow rate can be prevented. There is no effect on the differential flow rate signal used for detecting the CUW pipe breakage, and the pump trip function due to the large CUW differential flow rate due to the pipe breakage is not impaired.

According to a fourth aspect of the present invention, a signal from the reactor coolant purifying system blowdown flow rate controller and a signal from a main water level controller for controlling a reactor water level in the reactor pressure vessel are input. Further, a low priority circuit for generating an output signal is provided to the reactor coolant purifying blowdown valve.

According to the fourth aspect of the present invention, the water supply control system includes C
UW blowdown flow controller and low value priority circuit (hereinafter referred to as LV
G), and the CUW blowdown flow controller has C
The difference between the UW inlet flow rate and the CUW blowdown flow rate is input, and the CUW blowdown flow controller outputs so that the difference becomes zero.

Then, the output from the LVG and the signal from the main water level controller output are input to the LVG, and the lower value is prioritized so that the CUW blowdown flow rate does not exceed the CUW inlet flow rate and the difference due to the increase in the CUW blowdown flow rate. Generation of a large flow rate signal can be prevented. There is no effect on the differential flow rate signal used for CUW pipe break detection.
The pump trip function due to the large W difference flow rate is not impaired.

According to a fifth aspect of the present invention, a signal is input from the reactor coolant purifying system inlet flow meter and the blowdown flow meter, and the coolant is discharged from the reactor coolant purifying system outlet line. Characterized in that a difference flow rate detection circuit for determining the difference is provided.

According to the fifth aspect of the present invention, the difference between the CUW blow-down flow rate and the CUW blow-down flow rate is determined by subtracting the CUW blow-down flow rate from the CUW inlet flow rate in order to determine the state of water drainage at the CUW outlet line. Considering the fluctuation of the CUW inlet flow rate and the CUW blowdown flow rate, the difference becomes positive, so that it is determined that the coolant is discharged from the CUW outlet line.

As a result, an increase in the CUW blowdown flow rate can be detected, and generation of a large differential flow rate signal due to an increase in the CUW blowdown flow rate can be prevented. There is no effect on the differential flow signal used for detecting the CUW pipe breakage, and the pump trip function due to the large CUW differential flow rate due to the pipe breakage is not impaired.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a trip prevention device for a reactor coolant purifying system pump according to the present invention will be described with reference to FIG. This embodiment corresponds to the first, third and fifth aspects of the invention. In FIG. 1, the same portions as those in FIG. 3 are denoted by the same reference numerals, and the description of the overlapping portions will be omitted.

That is, the present invention differs from the conventional example in that the second check valve 32 is provided in the CUW outlet line 8 connecting the branch point 30 and the regenerative heat exchanger 3. According to the third aspect of the present invention, the signals from the CUW inlet flowmeter 15 and the blowdown flowmeter 13 are input to the second differential flow rate detection circuit 34, and the difference caused by the generated signal from the differential flow rate detection circuit 34 is equal to or larger than the set value. That is, an alarm circuit 33 that generates an alarm 36 at the time of 35 is provided.

In the invention of claim 5, signals from the CUW inlet flow meter 15 and the blowdown flow meter 13 are inputted,
The difference flow rate detection circuit 31 for determining that the coolant (water) is leaking (discharging) from the outlet line 8 is provided.

According to the first aspect of the invention, the second check valve 32 prevents the CUW blowdown flow from flowing below the CUW inlet flow in order to prevent the CUW pump from tripping.
The second check valve 32 is provided near the branch point 30 of the CUW outlet line.

However, if the CUW blowdown flow rate is CU
When the flow rate exceeds the W inlet flow rate, the water from the branch point 30 to the check valve 10 (referred to as the first check valve 10) does not flow to the waste treatment system, and the coolant (water) drains. Prevent,
In addition, backflow can be prevented, and the CUW blowdown flow rate is CUW
By preventing the flow rate at the inlet from being exceeded, it is possible to prevent the generation of a large difference flow rate signal.

According to the third aspect of the present invention, a value obtained by subtracting the CUW inlet flow rate signal 27 from the CUW blowdown flow rate signal 29 is used to generate an alarm in a state where water is drained at the CUW outlet line, and the difference is equal to or greater than the set value. In the case where the CUW blowdown flow rate is increased, an increase in the CUW blowdown flow rate can be detected, and the occurrence of a large differential flow rate signal due to the increase in the CUW blowdown flow rate can be prevented.

According to the fifth aspect of the present invention, the method of determining the drainage state of the CUW outlet line based on the difference between the CUW blowdown flow rate and the CUW inlet flow rate is as follows. When the fluctuation of the CUW system flow rate is not considered, the CUW
When the difference obtained by subtracting the blowdown flow rate is 0 or more, it is determined that the water has drained, and this value is set as the set value.

In consideration of system fluctuations, if there is a fluctuation of 10% of the rated flow, the difference between the CUW inlet flow and the CUW blowdown flow is 10% of the rated flow.
At this time, it is determined that water has run out, and this value is set as a set value.
When the difference exceeds the set value, an alarm is issued and CUW
An increase in the blowdown flow rate can be detected, and the occurrence of a large differential flow rate signal due to an increase in the CUW blowdown flow rate can be prevented.

Next, a second embodiment of the trip prevention device for a reactor coolant purification system pump according to the present invention will be described with reference to FIG. This embodiment corresponds to the second and fourth aspects of the present invention. In FIG. 2, the same portions as those in FIG. 4 are denoted by the same reference numerals, and the description of the overlapping portions will be omitted.

That is, the parts of the present invention different from the conventional example are the CUW inlet flowmeter 15 and the blowdown flowmeter.
Signals 27 and 29 from 13 are input to a second comparator 39, and CUW
A CUW blowdown flow controller 40 for controlling the flow rate of the coolant flowing through the blow line 7 is provided.

Further, according to the invention of claim 4, a signal from the CUW blowdown flow rate controller 40 and a signal from the main water level controller 20 for controlling the reactor water level 17 in the reactor pressure vessel 1 are inputted, The CUW blowdown valve 12 is provided with a low priority circuit 41 for generating an output signal.

According to the second aspect of the present invention, C
Adjust the CUW blowdown using a CUW blowdown flow controller that uses the CUW blowdown flow deviation to control the UW blowdown flow. As a result, it is possible to prevent a large difference flow rate signal from being generated due to an increase in the CUW blowdown flow rate.

A fourth aspect is a control device for realizing the second aspect. That is, the CUW blowdown flow controller 9 is installed to control the deviation between the CUW inlet flow rate and the CUW blowdown flow rate to be zero. Further, a low value priority circuit (LVG) 41 is installed between the main water level controller 20 of the water supply control system and the CUW blowdown valve 12.

To the LVG 41, a signal generated from the CUW blowdown flow rate controller 40 in addition to a signal generated from the main water level controller 20 is input. If the signal generated from the main water level controller 20 is higher than the CUW blowdown flow rate 38 at the CUW inlet flow rate 37, the signal generated from the LVG 41 is the main water level controller 20.
Is selected.

If the signal from the main water level controller 20 indicates that the CUW blowdown flow rate 38 exceeds the CUW inlet flow rate 37, the CU
W blowdown flow controller 40 is CUW inlet flow 37 and CU
Since the deviation of the W blowdown flow rate 38 is controlled to be zero, the signal generated from the LVG 41 is selected from the signal from the CUW blowdown flow rate controller 40. All are CUW
The blow-down flow rate 38 does not exceed the CUW inlet flow rate 37, and a large differential flow rate signal due to an increase in the CUW blow-down flow rate 38 can be prevented.

[0046]

According to the present invention, even if the CUW blowdown flow rate increases during a water level disturbance, the CUW blowdown flow rate does not exceed the CUW inlet flow rate, and water is discharged from the CUW outlet line. By generating an alarm in an unusual state, it is possible to prevent a large difference flow rate signal from being generated due to an increase in CUW blowdown flow rate, and to prevent a CUW pump from being tripped due to a large erroneous CUW difference flow rate detection.

[Brief description of the drawings]

FIG. 1 is an apparatus and piping system diagram for explaining a first embodiment of a trip prevention device for a reactor coolant purification system pump according to the present invention.

FIG. 2 is an apparatus and piping block diagram for explaining a second embodiment of the trip prevention device for a reactor coolant purification system pump according to the present invention.

FIG. 3 is an apparatus and piping diagram for explaining a conventional trip prevention device for a reactor coolant purification system pump.

FIG. 4 is a block diagram of equipment and piping for explaining a water supply control system in FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... CUW inlet line, 3 ... Regenerative heat exchanger, 4 ... Non-regenerative heat exchanger, 5 ... CUW pump, 6
... Filter desalination equipment, 7 ... CUW blow line, 8 ... CUW
Outlet line, 9 ... CUW outlet flow meter, 10 ... Check valve, 11 ...
Reactor water supply line, 12 CUW blowdown valve, 13 blowdown flowmeter, 14 reactor containment vessel, 15 CUW inlet flowmeter, 16 feedwater control system, 17 reactor water level, 18 reactor water level Setting device, 19 ... Comparator, 20 ... Main water level controller, 21 ... Main controller, 22 ... T / D controller, 23 ... M / D controller, 24 ... C
UW controller, 25 CUW valve opening setting, 26 CUW valve actual opening, 27 CUW inlet flow signal, 28 CUW outlet flow signal, 29 CUW blowdown flow signal, 30 branch point, 31
... difference flow rate detection circuit, 32 ... second check valve, 33 ... alarm circuit,
34: second differential flow rate detection circuit, 35: difference is greater than set value, 36:
Alarm generation, 37: CUW inlet flow rate, 38: CUW blowdown flow rate, 39: second comparator, 40: CUW blowdown flow rate controller, 41: Low priority circuit (LVG).

Claims (5)

[Claims] A reactor pressure vessel is connected to a reactor coolant purification system inlet line and a reactor water supply line, and the reactor coolant purification system inlet line is connected to a reactor coolant purification system inlet flow meter, a regenerative heat A heat exchanger, a non-regenerative heat exchanger, a reactor coolant purifying system pump and a filter desalination unit are connected in series, and branch off in two directions with a downstream pipe connected to the furnace or the desalination unit as a branch point. One is connected to a reactor coolant purifying system outlet line, the other is connected to a reactor coolant purifying system blow line, and the reactor purifying system outlet line is connected to the regenerative heat exchanger, the reactor coolant purifying system outlet flow rate. A meter and a check valve are connected in series and the downstream side thereof is connected to the reactor water supply line, and the reactor coolant purification system blow line is connected with a blowdown valve and a blowdown flow meter in series and the downstream side thereof is waste. Connect to processing system And a second check valve is provided in the reactor coolant purification system outlet line connecting the branch point and the regenerative heat exchanger. Trip prevention device. 2. A reactor coolant purifying system blower which inputs signals from said reactor coolant purifying system inlet flowmeter and blowdown flowmeter to a differential flow rate detection circuit and controls a coolant flow rate flowing through said blow line. 2. The trip prevention device for a reactor coolant purification system pump according to claim 1, further comprising a down flow controller. 3. A signal from the reactor coolant purification system inlet flowmeter and blowdown flowmeter is input to a differential flow rate detection circuit, and an alarm is issued when a difference generated by the signal from the differential flow rate detection circuit exceeds a set value. 2. The trip prevention device for a reactor coolant purification system pump according to claim 1, further comprising an alarm circuit for generating the alarm. 4. A signal from the reactor coolant purifying system blowdown flow rate controller and a signal from a main water level controller for controlling a reactor water level in the reactor pressure vessel are inputted to the reactor. 3. A low-priority circuit for outputting an output signal to a coolant purifying blowdown valve.
A trip prevention device for a reactor coolant purification system pump according to the above. 5. A differential flow rate for inputting signals from the reactor coolant purifying system inlet flow meter and blowdown flow meter and determining that coolant is discharged from the reactor coolant purifying system outlet line. 5. The trip prevention device for a reactor coolant purification system pump according to claim 1, further comprising a detection circuit.