JP3108487B2 - Reactor operating area monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for monitoring the operating area of a nuclear power plant, and to reduce the calculation error of the core flow rate generated in the process of lowering the speed of the healthy pump when one recirculation pump is stopped. The present invention relates to a lost operating area monitoring device.

[0002]

2. Description of the Related Art The operating area of a nuclear power plant is usually defined by the reactor power and the core flow rate, and is set in an area where the operation of the nuclear power plant does not hinder the operation (for example, not in an unstable area or a recirculation pump cavitation area). It monitors that there is, and if it deviates from this stable region, it operates an interlock to limit output rise and fall so as not to deviate from the operation region.

The reactor recirculation system includes a core 2 housed in a reactor pressure vessel 1, an A system installed annularly around the core 2, as shown in the configuration diagram of FIG. A plurality of jet pumps 3a, 3 each of which is divided into two systems of B system
b, and a pump A for circulating reactor water for circulating reactor water to the reactor core 2 by driving the jet pumps 3a and 3b.
The system and the system B are provided with two recirculation pumps 4a and 4b, and generally one recirculation pump drives about 10 jet pumps. The core flow rate of the reactor water indicated by the thick arrow 5 flowing through the core 2 is determined by the jet pumps 3a, 3
b, the individual flow rates 6a, 6b obtained from the differential pressure detector
Are measured, and these are summed to calculate. Further, the thin arrow 5a in the figure indicates the flow direction of the reactor water in each part in the furnace.

If one of the two recirculation pumps 4a, 4b is stopped due to some abnormality during the operation of the reactor, an initial stop of one of the recirculation pumps shown in FIG. As shown in the configuration diagram at the time, since the driving force from the recirculation pump 4a to the plurality of jet pumps 3a of the A system disappears in the early stage of the stop of the recirculation pump 4a, the flow rate 6a of each jet pump 3a once becomes Becomes zero. However, since the B-system recirculation pump 4b on the healthy side is in the high-speed (90-100% speed) region near the normal rated output,
The driving force to the B-system jet pump 3b is large, and a part of the flow of the jet pump 3b flows backward to the stopped A-system jet pump 3a.

For this reason, the flow rate to the reactor core is reduced by the flow rate flowing back to the jet pump 3a, and the differential pressure signal from the differential pressure detector is not normally directional. Even if the flow rates 6a and 6b of the jet pumps 3a and 3b are simply added, a correct core flow rate cannot be obtained. Therefore,
When one of the recirculation pumps 4a is stopped, a correction operation (flow rate of the healthy jet pump−flow rate of the stopped jet pump) is performed by a backflow calculation circuit provided in an operation area monitoring device (not shown) in response to the stop signal to perform a core calculation. The flow rate is calculated.

On the other hand, as an operation procedure in the nuclear power plant, when an abnormality occurs in which one recirculation pump stops, the speed of the recirculation pump on the healthy side is reduced. This is because, in the reactor recirculation system, when one system stops, the pressure loss of the healthy system decreases, and as a result, the flow rate of the healthy side jet pump becomes 1.3 to 1.4 of the rated flow rate.
This is due to the fact that the recirculation pump on the stop side must be reduced to the minimum speed when the recirculation pump on the stop side is restarted.

However, in the process of lowering the speed of the sound-side recirculation pump, as shown in the configuration diagram when one recirculation pump is stopped in FIG. 5, the speed of the sound-side B-system recirculation pump 4b is reduced. Generally, when the pressure drops to nearly 40% of the rated value, the backflow in the A-system jet pump 3a on the stop side stops, and when the recirculation pump 4b is further lowered, the flow of the A-system jet pump 3a turns to a forward flow. . This is because the natural circulation force (convection) also exists on the stop side of the system A, and the pushing force due to the drive of the sound jet pump 3b is weakened by the lowering of the recirculation pump 4b of the system B, This is because the natural circulation force in the system A overcomes.

[0008]

When one of the recirculation pumps stops during the operation of the reactor, the flow of the reactor water by the jet pump is reduced by the jet pump on the side where the driving force from the recirculation pump is lost. In the early stage of the loss of the driving force, the flow reverses, and then returns to the normal flow when the speed of the healthy side recirculation pump is reduced.

However, in the conventional operating area monitoring apparatus, when the driving force of the one-system recirculation pump is lost, the core flow rate is calculated via the backflow calculation circuit regardless of the speed of the sound-side recirculation pump. In the state where the flow direction of the stop-side jet pump has changed to the positive flow, the flow rate is calculated as if the flow rate had dropped significantly from the actual value.

For this reason, it is determined that the state has deviated from the stable operation region of the reactor, and in some cases, an interlock for inhibiting the speed reduction of the sound side recirculation pump works to maintain the stable region, and There was a problem that there was a possibility that it could not be done. In particular, recently, the operation range has been expanded (the operation range has been expanded to high power and low core flow rate), and more efficient operation of the nuclear power plant has been considered. It is also an important parameter.

It is an object of the present invention to stop various recirculation pumps by inputting various process signals in a nuclear power plant and to reduce the speed of a healthy recirculation pump.
It is an object of the present invention to provide a reactor operating region monitoring apparatus capable of performing a core flow rate calculation corresponding to the switching of the flow direction of a stop jet pump to obtain an accurate operating point.

[0012]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
The operating region monitoring device for a nuclear reactor of the present invention
Of the reactor water by driving the jet pump
Start / stop signals and speeds of multiple recirculation pumps performing circulation
Signal and differential pressure signal and flow rate of the plurality of jet pumps
A signal is input and at least one of the recirculation pumps stops
Recirculation pump speed, differential pressure and jet pump flow
Output a positive flow signal when is less than the specified value,
Reset when the plurality of recirculation pumps are restarted
Forward / reverse flow determining unit, and the plurality of jet pumps
The flow signal and the start / stop signals of the plurality of recirculation pumps are
Input and at least one recirculation pump is stopped
In some cases, the stop side
Perform a backflow correction operation to reduce the flow rate of the
When the positive flow signal is input to the
Addition of pump flow and stop jet pump flow
Core flow calculation unit to obtain the core flow by performing
Nuclear reactor operation from the reactor power signal and the core flow signal
An operation area determination unit that performs the area determination is provided .

[0013]

[Action] When one of the two recirculation pumps stops,
In the early stage of the shutdown, the flow of the reactor water in the stop-side jet pump is reversed because the flow rate of the jet pump on the healthy side is large. Therefore, when calculating the core flow rate, the stoppage signal of one of the recirculation pumps is used to calculate the core flow rate. A backflow calculation circuit performs a backflow correction calculation for subtracting a backflow component.

However, if one of the recirculation pumps is stopped, the healthy jet pump is overloaded or the like. Therefore, control is performed to reduce the speed of the healthy recirculation pump. As a result, when the flow rate of the sound jet pump is reduced, there is no influence on the stop jet pump, and the flow of the reactor water of the stop jet pump is switched to the normal flow.

At this time, in the forward / reverse flow judging section, a signal for stopping one recirculation pump, a signal indicating that the recirculation pump speed is equal to or lower than a specified value, a signal indicating that the flow rate of the jet pump is equal to or lower than a specified value, and a differential pressure of the recirculation pump are specified. Under the condition that both the signals below the value are input, the reverse flow of the flow of the stop-side jet pump is stopped, it is determined that the flow has been switched to the normal flow, and a forward / reverse flow determination signal is output. An addition operation is performed without passing through a backflow operation circuit, a correct core flow rate is calculated, an accurate operation point is obtained, and the calculated operation point is output to an operation region determination unit to perform an operation region determination.

[0016]

An embodiment of the present invention will be described with reference to the drawings. Note that the same components as those of the above-described related art are denoted by the same reference numerals, and detailed description thereof will be omitted. According to the present invention, as shown in the block diagram of FIG. 1, among the various process quantities 10 (both signals of the A system and the B system are output) output from the nuclear power plant, both of the A and B systems are output. A forward / backflow determining unit 15 for receiving a recirculation pump speed signal 11, a jet pump flow signal 12, a recirculation pump differential pressure signal 13, and a recirculation pump operation / stop signal 14, and a forward / backflow determination unit 15 A core flow calculation unit 17 for calculating a core flow by inputting a forward / reverse flow determination signal 16 output from the above, a jet pump flow signal 12 of the process amount 10, and a start / stop signal 14 of a recirculation pump. It is configured.

The core flow rate signal 18 output from the core flow rate calculation section 17 is input to an operation area determination section 20 for determining an operation area of a nuclear power plant together with a reactor output signal 19 of the process amount 10. The output of the operation region determination signal is output to a display device 21 and an interlock circuit 22 (not shown).

The details of the normal / backflow judging section 15 are shown in FIG.
As shown in the logic diagram of FIG.
From 11, the signal 23 when the recirculation pump speed is 0% or more and equal to or less than the specified value (for example, normally, when the recirculation pump speed on the healthy side is around 40%, backflow stops, and the judgment value is equal to or less than the specified value. A), from the jet pump flow signal 12, the A system,
Alternatively, from the signal 24 when the flow rate of the jet pump of the B system is equal to or less than the specified value and the recirculation pump differential pressure signal 13, the signal 25 when the differential pressure of the recirculation pump of the A system or the B system is equal to or less than the specified value. (Because the driving force of the sound-side recirculation pump and the natural circulation force in the stop-side recirculation system are balanced in the vicinity where the backflow in the stop-side jet pump stops, the differential pressure and the jet pump flow rate are close to zero.)

Further, a recirculation pump operation / stop signal 14
From the signal 26 when one of the recirculation pumps is stopped
When both occur, the reverse flow is stopped, and the AND logic 27 outputs a forward / backward determination signal 16 indicating that the flow has changed to the forward flow. The positive and negative signals output from the AND logic 27
The backflow judging signal 16 is held by itself, and when the operation of the recirculation pump 4a is restarted, the two recirculation pumps 4a, 4b
Is reset by starting.

The core flow rate calculation unit 17 receives the jet pump flow rate signal 12 and the recirculation pump operation / stop signal 14, and if one recirculation pump is stopped, the backflow calculation circuit Compensation calculation (flow rate of healthy jet pump-
When the forward / reverse flow determination signal 16 is also added to the flow rate of the stop jet pump, the core flow rate is calculated by an addition operation (flow rate of the healthy jet pump + flow rate of the stop jet pump). A core flow signal 18 is output.

Next, the operation of the above configuration will be described. First, as shown in FIG. 3, when both of the A and B recirculation pumps 4a and 4b are operating normally, the flow rates 6a and 6b of the jet pumps 3a and 3b are naturally
b is also large and balanced, and the flows are all positive. In this case, in the forward / backflow determination unit 15,
Recirculation pump 1 by recirculation pump operation / stop signal 14
There is no signal 26 when only the standstill is stopped, and the recirculation pump speed signal 11
Is 0% or more and equal to or more than the specified value, the signal 23 is not output.

Since the recirculation pump differential pressure signal 13 is greater than a specified value in both the A system and the B system, no signal 25 is output. Further, the jet pump flow rate signal 12 does not output the signal 24 because the system A and the system B are above the specified values. Therefore,
The forward / backflow determination unit 15 does not output the forward / backflow determination signal 16, and the core flow rate calculation unit 17 adds the flow rates 6 a and 6 b of the jet pumps 3 a and 3 b for the A and B systems, and there is no correction calculation. Is output.

Next, as shown in FIG. 4, when one of the two recirculation pumps 4a and 4b is stopped, the healthy side recirculation pump 3b operates at a high speed in the initial stage. The driving force is used to drive the sound-side jet pump 3b.
Is high, and there is no flow of the stop-side jet pump 3a, and the resistance has been reduced, so that part of the reactor water from the sound-side jet pump 3b flows into the stop-side jet pump 3a of the A system, and the stop-side jet The flow of the pump 3a flows backward.

The recirculation pump operation / stop signal 14 at this time
Since stop information of the recirculation pump 4a is included, the forward / backflow determination unit 15 outputs a signal 26 for stopping only one recirculation pump. Recirculation pump differential pressure signal 13
Is higher than the specified value in system B, but is lower than the specified value in system A, so that signal 25 is output. Further, the jet pump flow signal 12 is higher than the specified value in the system B, but is lower than the specified value in the system A, so that the signal 24 is output.

However, the recirculation pump speed signal 11 indicates that the A-system recirculation pump 4a is stopped and its speed is 0%, while the B-system recirculation pump 4b is at 0% or more and at a specified value or more. Therefore, the signal 23 is not output. Therefore, although the forward / backflow determination signal 15 is not output from the forward / backflow determination unit 15, the core flow rate calculation unit 17 includes stop / stop information of the recirculation pump 4 a in the input recycle pump operation / stop signal 14. Since it is included, in the core flow rate calculation, a backflow correction calculation for subtracting the backflow component in the jet pump 3a of the A system by the backflow calculation circuit is performed, and a highly accurate core flow rate signal 18 is output.

Further, as shown in FIG. 5, when the recirculation pump 4a stops, the sound-side jet pump 3b
The recirculation pump 4b on the healthy side is speed-down controlled in consideration of the overload and the like, and its flow rate is, for example, 40% of the rated value.
%, The A-system stop-side jet pump 3a
The flow from the sound-side jet pump 3b flowing into the tank stops, and the flow of the stop-side jet pump 3a temporarily stops due to the natural circulation force of the reactor water, and then turns to a positive flow.

At this time, the forward / backflow judging section 15 outputs a signal 26 for stopping only one recirculation pump from the stop information of the recirculation pump 4a of the recirculation pump operation / stop signal 14, and the recirculation pump The differential pressure signal 13 is output from the A-system recirculation pump 4
The signal 25 is output because the differential pressure of a is equal to or less than the specified value.

Further, the jet pump flow signal 12 has an A system,
Since the value of the B system is equal to or less than the specified value, the signal 24 is output. Furthermore, the recirculation pump speed signal 11 is 0% for the A system,
Since the system is also below the specified value, the signal 23 is output. The condition of the AND logic 27 being satisfied means that the forward / backflow determination signal 16 is output from the forward / backflow determination unit 15 as the time when the backward flow in the stop jet pump 3a of the A system is stopped and switched to the forward flow. Is done.

Therefore, the core flow rate calculating section 17 applies the recirculation pump operation / stop signal 14 to the recirculation pump 4a.
However, since the forward / backflow determination signal 16 is input, the core flow rate calculation automatically subtracts the flow rate 6a of the A-system jet pump 3a from the backflow calculation circuit to the addition calculation. (The backflow calculation is performed before the switching), and an accurate core flow rate signal 18 is obtained and output to the operation region determination unit 20. Note that the forward / backflow determination signal 16 output from the AND logic 27 is held by itself, and when the operation of the recirculation pump 4a is restarted, the two recirculation pumps 4
It is reset when a and 4b are activated.

Another embodiment of the present invention is an apparatus using a process computer. That is, the output value of the conventional backflow calculation circuit (core flow rate obtained by backflow calculation) is set as the process computer input P. In addition, each of the A and B system jet pumps 3
Input the flow rates of a and 3b, and input the sum to a computer
Q. (An input value before the backflow operation is input to the computer and an addition operation is performed inside the computer.) The input R is created using the inputs P and Q.

The input R is a multi-switch input. In general, a multi-switch input is such that when one of the first input and the second input is defective, the normal input is determined as a representative input and output. If both inputs are normal, priority is given to the input. The input is a representative input. Here, the first input is set so as to be prioritized. Here, when the input P becomes equal to or less than a predetermined flow rate, that is, the speed of the sound-side recirculation pump is reduced, and an input failure is set near the stop of the backflow (this function is also set). This is common in process computers, and an input value is equal to or greater than or equal to a specified value, which is regarded as an input failure.)

Therefore, if the computer input R is input to the operation area determination unit 20 only when one recirculation pump is stopped, the first input becomes the representative value of the input R after the recirculation pump is stopped. When the backflow stops, the second input is input R
Is input to the operating region determination unit 20 as the representative value of As described above, according to the one embodiment and the other embodiments, it is possible to obtain an accurate core flow rate even in the process of lowering the speed after stopping one recirculation pump.

[0033]

As described above, according to the present invention, even when various kinds of reactor water are changed due to a partial stop of the recirculation pump, the state of the reactor water is accurately grasped and the core flow rate is always accurately obtained. Therefore, there is an effect that the reliability of the operation of the nuclear power plant can be improved and the burden on the operator can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an operation area monitoring apparatus according to the present invention.

FIG. 2 is a logic diagram of a forward / backward determining unit.

FIG. 3 is a configuration diagram showing a normal operation of the reactor recirculation system.

FIG. 4 is a configuration diagram showing an initial stage of stopping one recirculation pump of the reactor recirculation system.

FIG. 5 is a configuration diagram showing the latter half of the stoppage of one recirculation pump of the reactor recirculation system.

[Explanation of symbols]

2 core, 3a, 3b jet pump, 4a, 4b ...
Recirculation pump, 5a ... flow direction of reactor water in each part in the furnace, 10 ...
Process volume, 11: Recirculation pump speed signal, 12: Jet pump flow signal, 13: Recirculation pump differential pressure signal, 14: Recirculation pump operation / stop signal, 15: Forward / reverse flow judgment unit, 16 ...
Forward / backflow judgment signal, 17: core flow rate calculation unit, 18: core flow rate signal, 19: reactor output signal, 20: operation area judgment unit, 21 ...
Display device, 22: interlock circuit, 23: signal when the recirculation pump speed is 0% or more and not more than a specified value, 24: A
A signal when the flow rate of the jet pump of the system or the B system is equal to or less than a specified value, 25... A signal when the differential pressure of the recirculation pump of the A system or the B system is equal to or less than a specified value, 26. Signal when the stand is stopped, 27… AND logic.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G21C 17/032 G21D 3/04

Claims (1)

(57) [Claims] 1. A plurality of jet pumps are driven, respectively.
Multiple recirculation ports to circulate reactor water to the reactor core
Pump start / stop signal, speed signal, differential pressure signal and
Flow signals from multiple jet pumps are input and
At least one of the pumps stops and the recirculation pump speed and differential pressure
And the flow rate of the jet pump are
Output a positive flow signal when the plurality of recirculation pumps
A forward / backflow determination unit that is reset when restarted,
The flow signals of the plurality of jet pumps and the plurality of recirculations
A ring pump operation / stop signal is input and at least one
When the recirculation pump is stopped,
Subtract the stop jet pump flow from the pump flow
A backflow correction operation is performed, and the
If this occurs, the flow rate of the healthy jet pump and the
The core flow is calculated by adding the
A core flow rate calculation unit, a reactor output signal and the core
Operation area for determining the operating area of a nuclear reactor from the flow signal
Operating area monitoring device of the reactor, characterized in that a frequency band determination section.