JPH05164881A - Operating range monitoring device for nuclear reactor - Google Patents

Abstract

PURPOSE:To obtain an accurate operating point by allowing an operating section to operate flow in a reactor core in response to the flow direction of a suspension side jet pump in a process where one recirculation pump is suspended and another recirculation pump at the sound side is lowered in speed. CONSTITUTION:Out of various process quantities 10 outputted out of a nuclear power plant (both A series signals and B series signals are outputted), recirculation pump speed signals 11, jet pump flow signals 12, recirculation pump differential pressure signals 13, and recirculation pump operation/ suspension signals 14 are inputted to a normal/reverse flow judging section 15. Normal/reverse flow judging signals 16, the jet pump flow signals 12 and the recirculation pump operation/suspension signals 14 are inputted into a reactor core flow operating section 17, so that flow in a reactor core is thereby operated. And yet, reactor core flow signals 18 outputted from the reactor core flow operating section 17 is inputted into an operation range judging section 20 which makes judgement on the operation range of the nuclear power plant, together with nuclear reactor output signals 19, and the aforesaid output, that is, the operation range judging signals are outputted to a display means 21 and an interlock circuit 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear power plant operating area monitoring apparatus, and in a state where one recirculation pump is stopped, a calculation error of a core flow rate which occurs in the process of controlling the deceleration of a sound side pump. It relates to a lost operating area monitoring device.

[0002]

2. Description of the Related Art The operating region of a nuclear power plant is usually defined by the reactor power and the core flow rate, and the state of the nuclear power plant is in a region where it does not hinder the operation (eg, unstable region, recirculation pump cavitation region, etc.). When there is a deviation, the interlock is operated to limit the output increase and decrease so that the operation area is not exceeded.

The reactor recirculation system has a reactor core 2 housed in a reactor pressure vessel 1, an A system and a system A arranged in a ring around the reactor core 2 as shown in the configuration diagram of FIG. A plurality of jet pumps 3a, 3 classified into two systems of B system
b, and a reactor water circulation pump A for driving the jet pumps 3a, 3b to circulate the reactor water to the core 2.
Two recirculation pumps 4a and 4b of the system and the B system are provided, and generally one recirculation pump drives about 10 jet pumps. In addition, the core flow rate of the reactor water indicated by the thick arrow 5 flowing in the reactor core 2 is the jet pumps 3a, 3
Individual flow rates 6a and 6b obtained from the differential pressure detector installed in b.
Is measured and these are summed up to calculate. Further, thin line arrows 5a in the figure indicate the flow direction of the reactor water in each part in the reactor.

If one of the two recirculation pumps 4a and 4b is stopped due to some abnormality during operation of the reactor, one recirculation pump of FIG. 4 is initially stopped. As shown in the configuration diagram at that time, since the driving force from the recirculation pump 4a to the plurality of jet pumps 3a in the A system disappears at the initial stage of stopping the recirculation pump 4a, the flow rate 6a of each jet pump 3a is once It becomes zero. However, since the B system recirculation pump 4b on the sound side is in the high speed (90 to 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 side.

For this reason, the flow rate to the core is reduced by the amount of flow back to the jet pump 3a, and the differential pressure signal from the differential pressure detector does not normally have directional characteristics. Even if the flow rates 6a and 6b of the jet pumps 3a and 3b are simply added, the core flow rate will not be correct. Therefore,
When one recirculation pump 4a is stopped, a correction calculation (flow rate of sound side jet pump-flow rate of stop side jet pump) is performed by the back flow calculation circuit provided in the operating area monitoring device (not shown) by this stop signal to perform core calculation. The flow rate is calculated.

On the other hand, as an operating procedure in a nuclear power plant, it is specified that the speed of the recirculation pump on the healthy side is decreased when an abnormality occurs in which one recirculation pump is stopped. This is because in the reactor recirculation system, when one system stops, the pressure loss in the healthy system decreases, and as a result, the flow rate of the sound side jet pump is 1.3 to 1.4% of the rated flow rate.
This is due to the fact that the double-sided increase is not preferable, and that when the recirculation pump on the stop side is restarted, the recirculation pump on the sound side must be reduced to the minimum speed.

However, in the process of lowering the speed of the healthy side recirculation pump, the speed of the B side recirculation pump 4b on the healthy side is changed as shown in the configuration diagram when one recirculation pump is stopped in FIG. Generally, when the value is reduced to about 40% of the rated value, the reverse flow in the A system jet pump 3a on the stop side is stopped, and when the recirculation pump 4b is further decelerated, the flow of the A system jet pump 3a is changed to a forward flow. .. This is because the natural circulation force (convection) also exists on the stop side of the A system, so that the recirculation pump 4b of the B system is decelerated, and the pushing force by the drive of the sound jet pump 3b is weakened. This is because the natural circulation force in the A system is overcome.

[0008]

When one of the recirculation pumps is stopped 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. At the initial stage of the loss of driving force, the flow becomes a reverse flow, and then when the speed of the sound side recirculation pump is reduced, it becomes a normal flow again.

However, in the conventional operation area monitor, when the driving force of the one-sided recirculation pump is lost, the core flow rate calculation is performed through the backflow calculation circuit regardless of the speed of the sound side recirculation pump. Since the correction calculation is performed by the correction calculation, the flow rate of the stop-side jet pump is calculated so that the flow rate is significantly lower than the actual flow rate when the flow direction is changed to the normal flow.

For this reason, it is judged that the reactor has deviated from the stable operating region, and in some cases, in order to maintain this stable region, the interlock for prohibiting the speed drop of the sound side recirculation pump works to lower the speed. There was a problem that there was a possibility that it could not be done. In particular, recently, more efficient operation of nuclear power plants is being studied by expanding the operating range (expanding the operating range to high power and low core flow rate). It is also an important parameter.

The object of the present invention is to input various process signals in a nuclear power plant to stop one recirculation pump and to reduce the speed of the healthy side recirculation pump.
It is an object of the present invention to provide a reactor operating area monitoring device capable of performing a core flow rate calculation corresponding to switching of the flow direction of a jet pump on the stop side to obtain an accurate operating point.

[0012]

[Means for Solving the Problems] In an operating area monitoring device based on an operating point determined by a reactor output and a core flow rate of a nuclear power plant, a plant operating parameter for determining an operating state of a plurality of reactor water circulation pumps. And forward / backflow determination section that determines whether the flow direction of the reactor water is normal flow or reverse flow, and the core flow rate that adds or subtracts the core flow rate based on the flow state of the reactor water determined by this forward / backflow determination section. An arithmetic unit is provided.

[0013]

[Operation] When one of the two recirculation pumps stops,
At the initial stage of the stop, the flow rate of the sound jet pump on the sound side is high, and therefore the flow of the reactor water in the stop jet pump becomes a reverse flow. Therefore, when calculating the core flow rate, one reactor recycle pump stop signal is sent to the core flow rate calculation unit. The backflow calculation circuit performs backflow correction calculation for subtracting the backflow.

However, if one of the recirculation pumps is stopped, the sound side jet pump will be overloaded, so that control is performed to reduce the speed of the sound side recirculation pump. As a result, when the flow rate of the sound jet pump decreases, the stop jet pump is not affected, 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 determination unit, a signal for stopping one recirculation pump, a signal for the recirculation pump speed being less than a specified value, a signal for the flow rate of the jet pump being less than a specified value, and a differential pressure for the recirculation pump being specified. On condition that both signals below the value are input, it is judged that the reverse flow of the flow of the jet pump on the stop side has stopped and switched to the normal flow, and the forward / reverse flow judgment signal is output. An addition operation is performed without passing through a backflow operation circuit to calculate a correct core flow rate, obtain an accurate operating point, and output it to the operation area determination unit to perform operation area determination.

[0016]

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

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

The details of the forward / backward flow determining unit 15 are shown in FIG.
The recirculation pump speed signal as shown in the logic schematic of
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 sound side is around 40%, the backflow is stopped, so the judgment value is less than the specified value. From the jet pump flow signal 12,
Alternatively, from the signal 24 when the flow rate of the B system jet pump is less than the specified value and the recirculation pump differential pressure signal 13, a signal 25 when the differential pressure of the A system or B system recirculation pump is less than the specified value. (Because the driving force of the sound side recirculation pump and the natural circulation force of the stop side recirculation system are balanced in the vicinity where the backflow in the stop side jet pump is stopped, the differential pressure and the jet pump flow rate are close to zero).

In addition, the recirculation pump run / stop signal 14
From, signal 26 when one of the recirculation pumps is stopped
Is generated by the AND logic 27 that outputs the normal / reverse flow determination signal 16 indicating that the reverse flow has stopped and the flow has changed to the normal flow. In addition, the positive / negative output from AND logic 27
The backflow determination signal 16 is held by itself, and when the operation of the recirculation pump 4a is restarted, the two recirculation pumps 4a and 4b are
Is set to be reset when it starts up.

In the core flow rate calculation unit 17, the jet pump flow rate signal 12 and the recirculation pump operation / stop signal 14 are input, and if one recirculation pump is stopped, the reverse flow is calculated by the reverse flow calculation circuit. Compensation calculation (flow rate of sound side jet pump −
If the forward / reverse flow determination signal 16 is also added to the flow rate of the stop side jet pump), the core flow rate is calculated by addition calculation (flow rate of the sound side jet pump + flow rate of the stop side jet pump). The core flow rate signal 18 is output.

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

Further, since the recirculation pump differential pressure signal 13 in both the A system and the B system is the specified value or more, the signal 25 is not output. Further, the jet pump flow rate signal 12 does not output the signal 24 because the A system and the B system have the specified values or more. Therefore,
No forward / backflow determination signal 16 is output from the forward / reverse flow determination unit 15, and the core flow rate calculation unit 17 adds the flow rates 6a and 6b of the A system and B system jet pumps 3a and 3b without correction calculation. Core flow rate signal 18 is output.

Next, as shown in FIG. 4, when one of the two recirculation pumps 4a and 4b is stopped, the sound side recirculation pump 3b operates at high speed in the initial stage. The driving force of this jet pump 3b
The flow rate of the stop jet pump 3a is high and the resistance has decreased, so that part of the reactor water from the sound jet pump 3b flows into the stop jet pump 3a of the A system, and the stop jet The flow of the pump 3a flows backward.

Recirculation pump run / stop signal 14 at this time
Since the stop information of the recirculation pump 4a is included, the forward / backflow determination unit 15 outputs the signal 26 for stopping only one recirculation pump. Also, the recirculation pump differential pressure signal 13
In the B system, a signal 25 is output because it is above the specified value, but in the A system it is below the specified value. Further, the jet pump flow rate signal 12 is output above the specified value in the B system, but below the specified value in the A system, 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%, but the B system recirculation pump 4b is 0% or more and is equal to or more than the specified value. Therefore, the signal 23 is not output. Therefore, although the forward / backflow determination signal 16 is not output from the forward / backflow determination unit 15, the core flow rate calculation unit 17 outputs the stop / restart signal of the recirculation pump 4a to the input operation / stop signal 14 of the recirculation pump. Therefore, when calculating the core flow rate, the backflow calculation circuit performs the reverse flow correction calculation for subtracting the reverse flow amount in the jet pump 3a of the A system, and the highly accurate core flow rate signal 18 is output.

Further, as shown in FIG. 5, since the recirculation pump 4a is stopped, the sound side jet pump 3b is
The recirculation pump 4b on the sound side is controlled for speed reduction in consideration of the overload of the
%, The jet pump 3a on the stop side of system A
The flow from the sound-side jet pump 3b flowing into the cylinder is stopped, and the flow of the stop-side jet pump 3a temporarily stops by the natural circulation force of the reactor water and then turns to a normal flow.

At this time, in the forward / reverse flow determining unit 15, a signal 26 for stopping only one recirculation pump is output from the stop information of the recirculation pump 4a of the operation / stop signal 14 of the recirculation pump, and the recirculation pump is output. The differential pressure signal 13 is the A system recirculation pump 4
The signal 25 is output because the differential pressure of a is less than the specified value.

Further, the jet pump flow rate signal 12 is A system,
The signal 24 is output because the B system is below the specified value. Further, the recirculation pump speed signal 11 is 0% for the A system, and B
Since the system is also below the specified value, signal 23 is output. When the condition of the AND logic 27 is satisfied, the forward / backflow determination signal 15 is output from the forward / backflow determination unit 15 at the time when the reverse flow in the stop side jet pump 3a of the A system is stopped and switched to the normal flow. To be done.

Therefore, in the core flow rate calculation unit 17, the recirculation pump 4a is sent to the input operation / stop signal 14 of the recirculation pump.
Although the stop information is included, since the forward / reverse flow determination signal 16 is input, when calculating the core flow rate, the flow rate 6a of the A system jet pump 3a is automatically added to the addition calculation from the subtraction by the reverse flow calculation circuit. (Backflow calculation is performed before switching), an accurate core flow rate signal 18 is obtained and output to the operating region determination unit 20. 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
When a and 4b are activated, they are reset.

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 the backflow calculation) is used as the process computer input 1. In addition, each A, B system jet pump 3
The flow rates of a and 3b are input, and the added value is used as the computer input 2. (The input value before the backflow calculation is input to the computer and the addition calculation is performed inside the computer.) Using these inputs 1 and 2, input 3 is made.

This input 3 is a multi-switch input. The multi-switching input generally means that if one of the first and second inputs is defective, the normal input is judged to be the representative input and is output. If both inputs are normal, priority is given. The input is used as a representative input. Here, the first input is set to be prioritized. Here, when the input 1 becomes less than a certain specified flow rate, that is, the speed of the sound side recirculation pump is reduced, and the input becomes defective near the backflow stop (this function is also set. It is common in process calculators and the input value is above or below the specified value and it is considered as an input failure).

Therefore, if the computer input 3 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 3 after the recirculation pump is stopped, The second input is input 3 when the backflow is stopped
Will be input to the operating region determination unit 20 as a representative value of. As described above, according to the one embodiment and the other embodiments, an accurate core flow rate can be obtained even in the speed-down process after stopping one recirculation pump.

[0033]

As described above, according to the present invention, even when various kinds of reactor water change due to 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, it is possible to improve the reliability of the operation of the nuclear power plant and reduce the burden on the operator.

[Brief description of drawings]

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

FIG. 2 is a logical diagram of a forward / backflow determining unit.

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

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

FIG. 5 is a configuration diagram showing the latter half of a period when one recirculation pump of the nuclear reactor recirculation system is stopped.

[Explanation of symbols]

2 ... Core, 3a, 3b ... Jet pump, 4a, 4b ...
Recirculation pump, 5a ... Reactor water flow direction in each part of the furnace, 10 ...
Process amount, 11 ... Recirculation pump speed signal, 12 ... Jet pump flow rate signal, 13 ... Recirculation pump differential pressure signal, 14 ... Recirculation pump operation / stop signal, 15 ... Forward / reverse flow determination unit, 16 ...
Forward / reverse flow determination signal, 17 ... Core flow rate calculation unit, 18 ... Core flow rate signal, 19 ... Reactor output signal, 20 ... Operating region determination unit, 21 ...
Display device, 22 ... Interlock circuit, 23 ... Signal when recirculation pump speed is 0% or more and below specified value, 24 ... A
Signal when the flow rate of the system or B system jet pump is less than the specified value, 25 ... Signal when the differential pressure of the A system or B system recirculation pump is less than the specified value, 26 ... 1 of the recirculation pump Signal when stand is stopped, 27 ... AND logic.

Claims (1)

[Claims] 1. An operating area monitoring device based on an operating point defined by a reactor output and a core flow rate of a nuclear power plant, wherein plant operating parameters for judging operating states of reactor water circulation pumps of a plurality of systems and system-by-system A forward / backflow determination unit that determines whether the flow direction of the reactor water is normal flow or a reverse flow, and a core flow rate calculation unit that adds or subtracts the core flow rate according to the flow state of the reactor water determined by this forward / backflow determination unit are provided. A device for monitoring the operating area of a nuclear reactor.