JPH0373837B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a nuclear reactor water level control device, and particularly relates to a reactor water supply control device having a reactor feed water regulating valve and a reactor purification device having a blowdown flow rate regulating valve. The present invention relates to a reactor water level control device that controls the water level of a reactor in a boiling water nuclear power plant equipped with a reactor during startup and shutdown of the reactor.

[Conventional technology]

Conventionally, in this type of nuclear reactor, water level control is performed by a water supply control device during normal operation. However, reactor water level control during reactor startup and shutdown has traditionally relied on manual operations by operators.
In other words, when the reactor water level shows an upward trend, the blowdown flow control valve of the reactor purification system is opened to return reactor water to the condenser, and when the reactor water level shows a downward trend, the water supply is turned off. The reactor water level is manually controlled by opening the reactor water adjustment valve in the control device and supplying water to the reactor. When starting and shutting down a nuclear reactor, operators must also manually operate the control rods. Therefore, manual water level control operations, together with manual operation of the control rods, place a burden on the operators. There is.

[Problem to be solved by the invention]

Therefore, from the perspective of reducing the burden on operators and preventing operator errors, it is desirable to improve the reactor water level control system during reactor startup and shutdown, so that it can be automatically controlled. It is rare.

If automatic control is simply desired, it may be thought that it would be sufficient to obtain a signal to maintain a desired water level and control each valve using this signal. However, if this is only the case, it may be fine if there is no limit to the valve opening degree, but a problem will arise if the valve is set so that it must be opened at least to a certain degree.

For example, a case where it is better to maintain a constant valve opening is when it is desired to prevent thermal fatigue of equipment due to repeated temperature changes (thermal cycles).

Generally, in this type of device, as shown schematically in FIG. 3, water supply b from a water supply regulating valve a is injected from a hole d of a doughnut-shaped stargear c as shown by an arrow e and enters the inside of a furnace f. , this water is usually at room temperature, around 30°C. However, the water in the furnace is at a high temperature, reaching 280 degrees Celsius when the furnace pressure is 70 ata. Therefore, due to this temperature difference, if the water supply is repeated intermittently, temperature changes will occur repeatedly, causing fatigue in the materials of the equipment, leading to cracks and damage to the equipment. To prevent this, avoid opening the valve from a fully closed state and causing rapid cooling, and keep it open at least a certain degree at all times to maintain a constant temperature distribution. .

As mentioned above, there are cases where it is desirable to maintain a constant minimum valve opening, and in this case, it is desirable to have a configuration in which such a constant minimum opening can be set arbitrarily, and if there is no limit, the entire range It is better to have something that can be controlled. Such a configuration cannot be achieved by a simple configuration in which the valve opening degree is automatically controlled using a desired water level signal.

The present invention was made based on the above-mentioned knowledge, and its purpose is to provide a water level control device that can automatically control the reactor water level and also that can set limits on the valve opening degree. The objective is to reduce the burden on operators by providing reliable and stable control of the reactor water level.

[Means to solve the problem]

In order to achieve the above object, in the present invention,
A nuclear reactor that controls the water level of a reactor in a boiling water nuclear power plant, which is equipped with a water supply control device having a reactor water supply control valve and a reactor purification device having a blowdown flow rate control valve, during reactor startup and shutdown. In the water level control device, the output of the main water level controller, which calculates the deviation between the water level set value and the detected water level value and creates a request signal for the valve opening degree, is input to the lower limit millimeter, and the lower limit millimeter is preset by the water supply adjustment valve. The lower limit of the opening of the opening is set, and the water level is controlled by adjusting the water supply regulating valve according to the signal from the lower limit millimeter.If a request signal is received that is lower than the opening of the lower limit, the input of the lower limit millimeter is set. The blowdown flow rate regulating valve is adjusted based on the output deviation signal, thereby controlling the reactor water level.

[Effect]

As a result of the above configuration, the minimum opening degree of the water supply regulating valve can be set arbitrarily using the lower limit limiter, so the minimum can be set to 0%, or a certain amount of flow rate can be secured to maintain heat. When you want to suppress changes, you can easily set a desired minimum opening degree. Furthermore, the set water level and actual (detected value)
Depending on the deviation from the water level, the water supply adjustment valve and, if necessary, the blowdown adjustment valve can be controlled to achieve automatic and stable water level control. Of course, continuous control is also possible. Moreover, the blowdown regulating valve is properly controlled according to a predetermined program. This greatly reduces the burden on the operator and makes water level control stable and reliable.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In this example, the present invention is applied to a boiling water nuclear power plant.

FIG. 1 is a system diagram of this example. In the figure, numeral 5 indicates a reactor feed water adjustment valve, and this feed water adjustment valve 5 forms a part of the water supply control device. 6 is a blowdown flow rate regulating valve, and this valve 6 forms a part of the furnace purification device. The water level in the reactor 3 is adjusted by these valves 5 and 6.

FIG. 2 is a block diagram showing the water level control device of this example. Water level setting value 7 and water level detection value 8
The deviation _S1 from the lower limiter 11 is inputted to the lower limiter 11, and the signal _S3 from the lower limiter 11 plays the role of adjusting the water supply regulating valve 5 to control the water level. In addition, this lower limit limiter 11 is used to set the lower limit of the opening degree of the water supply regulating valve 5 in advance, and when a request signal that is below the lower limit set in this way is received, the input/output deviation of the lower limit limiter is set. The blowdown flow rate regulating valve 6 is adjusted based on the signal.

By adjusting the valves 5 and 6 in this manner, the reactor 3
water level is controlled.

More specifically, the configuration of this embodiment is as follows.

The water level detection value 8 shown in FIG. 2 is measured by the water level detector 81 shown in FIG. There are various methods of measuring the water level, but in this example, as is commonly used, a reference level device 82 is provided, and the pressure P ₁ between the reference level device 82 and the water level detector 81 is used as a reference. The water level is measured using the pressure P ₂ between the water level and the water level detector 81 and the pressure difference ΔP between this pressure P ₂ and the water level.

The water level set value 7 shown in FIG. 2 is determined as appropriate depending on the conditions, and this set value 7 and the detected value 8 are compared.

In FIG. 1, reference numeral 1 denotes a bypass valve, which serves to guide steam from the nuclear reactor 3 to the condenser 2 as indicated by arrow A, depending on the situation. 4a and 4b are pumps. 4
1 is a check valve that allows the flow to flow only in the direction of the arrow.

This water level control device controls the water level of the reactor 3 when the reactor 3 is started or stopped.As an example, let us assume that the reactor is in the nuclear heating stage and explain the operation of this device at this stage. do. At this time, the reactor pressure slowly rises due to the increase in reactor output due to the withdrawal of the control rods. When the reactor pressure reaches the rated value, the bypass valve 1 is opened by the pressure control device, and steam is guided to the condenser 2 to control the reactor pressure at a constant level.

In this operating state, the amount of inflow and outflow of cooling water that affects the reactor water level is as follows. First, as the cooling water flowing into the reactor 3, the feed water flow rate (arrow B
) and cooling water from the control rod drive hydraulic system. On the other hand, the cooling water flowing out from the reactor 3 includes a steam flow rate (arrow A) flowing into the condenser 2 through the bypass valve 1 and a dump steam flow flowing into the condenser 2 through the blowdown flow rate adjustment valve 6. There is a flow rate (arrow C).

Of the above inflow and outflow flow rates, the cooling water from the control rod driving hydraulic system is always constant, so there is no need to particularly control it. Further, the steam flow rate is determined by the opening degree of the bypass valve 1 under reactor pressure control.
Therefore, the water level in the reactor is ultimately controlled by adjusting the amount of water flowing into and out of the reactor 3 using the feed water adjustment valve 5 and the blowdown flow rate adjustment valve 6, as mentioned at the beginning. Become.

In other words, if the reactor water level shows a rising trend,
The blowdown flow rate adjustment valve 6 is opened to dump reactor water to the condenser 2 to lower the water level. Conversely, if the reactor water level shows a downward trend, the water supply adjustment valve 5 is opened to supply water to the reactor 3. to raise the water level.

Next, water level control in this case will be explained using the control block diagram shown in FIG.

The water level set value 7 is determined in advance, and this set value 7
The deviation S ₁ between the reactor water level detection value (water level signal) 8 from the water level detector 81 mentioned above is determined by the main water level controller 9.
The output signal _S2 is sent to the lower limiter 1 via the M/A operator (manual/automatic operator) 10.
1. Since this output signal S ₂ represents the deviation between the set value 7 and the detected value 8 which is the actual measurement value,
A signal S ₃ outputted from the lower limiter 11 based on the output signal S ₂ becomes an opening request signal for the water supply regulating valve 5 .

For example, the water level setting value is 100cm and the water level detection value is 90cm.
Suppose it was. Since the set value is entered as + and the detected value is entered as -, +10 cm is the deviation. This signal is corrected by the main water level controller 9 by multiplying it by a coefficient. In a configuration where the valve opening is commanded as a percentage, if you set the valve to open 100% with a deviation of +10cm,
This coefficient may be set to proportional gain K=10. Therefore, if the deviation is +10cm, that is, the water level is 10cm lower than the setting, the lower limiter 11
A command to open the valve by % is given to the water supply regulating valve 5. The valve 5 (FIG. 1) is therefore fully opened, water is supplied from the valve 5 in the direction of arrow B, and the water level rises. If, +
If 100% valve opening is too large at 10 cm, the value of K can be set to a small value, and this can be set arbitrarily.

Next, a case where the water level is higher than the setting will be explained. If detected water level 8 is 110cm, the deviation is -10cm
It is. The output signal from the main water level controller 9 is -100% multiplied by the proportional gain K=10. As described above, the minimum opening degree of the water supply regulating valve 5 is set by the lower limiter 11, and in this example, it is assumed that this minimum setting value is set to the opening degree equivalent to 0%. Therefore, since the opening degree is -100%, that is, the fully closed signal, the water supply regulating valve 5 is fully closed.

In this situation, a case where the water level continues to rise even though the valve 5 is fully closed (minimum opening degree) will be explained. In this case, the minimum opening degree of the lower limiter 11 is set to 0%, that is, -100%. and,
Even if the opening degree of this water supply regulating valve reaches -100% (fully closed), if a signal indicating that the measured reactor water level still exceeds the set point is given, the input/output deviation of the lower limiter 11 Signal 12 increases steadily. Suppose that this signal 12 is, for example, a signal to set the opening degree of the blowdown flow rate adjustment valve to 100% (that is, to fully open the valve). Then, this signal 12 enters the opening computing unit 14 via the M/A operating unit 13. This signal 12 serves as a command to open the blowdown flow rate regulating valve 6, but it is appropriately corrected by this calculator 14 to become a command signal _S4 . In other words, the signal 12 indicating 100% valve opening is currently coming, but if this is too large, this calculator 14 multiplies it by a correction coefficient of 0.5 to correct it to a signal indicating 50% valve opening. Therefore, this 50% valve opening command is applied to the blowdown flow rate regulating valve 6 via the pressure correction circuit 15.
is opened by the amount specified by the command. As a result, water is blown down from the reactor 3 through the valve 5,
The water level will go down and will be able to maintain an appropriate level.
Note that the pressure correction circuit 15 corrects the command signal S ₄ based on the reactor pressure signal 16. In other words, the flow rate flowing through the blowdown regulating valve 6 changes depending on the pressure of the water flow applied to the blowdown regulating valve 6, so it plays a role of appropriately correcting the valve opening degree according to the pressure. Reactor pressure ranges from 1ata to 70ata
On the other hand, the pressure inside the condenser 2 is in a vacuum state and is about 0.1 ata, so the pressure difference ΔP' before and after the blowdown pressure regulating valve 6 is
ΔP' is in the range of 0.9 to 70, and naturally the flow velocity in the valve 6 will vary depending on the differential pressure. This is because the flow rate is proportional to the square root of the differential pressure. Therefore, an appropriate discharge flow rate should be ensured by opening the valve at an appropriate amount depending on the differential pressure.

In other words, if the water level is higher than the set value like this,
In other words, when the reactor water level shows an upward trend, the output signal of the main water level controller 9 decreases, and the opening degree of the feed water regulating valve 5 is accordingly reduced. (equivalent to 0% opening of the water supply adjustment valve 5) (in this case, the opening of the water supply adjustment valve 5 is equivalent to 0%)
(fully closed), if the water level rises, the output signal of the main water level controller 9 becomes negative. As a result, the input/output deviation signal 12 of the lower limiter 11 increases to the positive side. The signal is input to the opening computing unit 14 via the M/A operating unit 13. After this is appropriately adjusted by the opening calculator 14, the output signal is sent to the pressure correction circuit 1 based on the reactor pressure signal 16.
The flow rate is optimally adjusted at step 5 and input to the blowdown flow rate adjustment valve 6. As a result, the blowdown flow rate regulating valve 6 is opened at an optimal opening degree, and excess reactor water is returned to the condenser, so that the reactor water level is maintained at an optimal value.

In the above embodiment, the valve 5 is controlled by the lower limiter 11.
The maximum opening of valve 5 was set to 0%, but as already mentioned, there are cases where it is better not to fully close valve 5.
At this time, the lower limit can be arbitrarily set to about 0.5 to 1%.

Further, in the above example, the lower limiter 11 is provided only on the water supply regulating valve 5, but it is also possible to provide a limiter on the blowdown regulating valve 6 in order to provide the same effect. In this case, it is provided as an upper limiter for the valve 6. This is effective in solving the pressure problem in the flow system of the blowdown regulating valve 6. Specifically, in addition to the correction circuit 15 that corrects the gain of the opening degree calculator 14 of the blowdown flow rate adjustment valve 6 based on the reactor pressure signal 16 detected separately, It can be configured with an upper limiter.

As mentioned above, the reactor water level control system of this embodiment is as follows:
The deviation between the reactor water level set value and the detected water level value in a boiling water nuclear power plant is input to the lower limiter, and the water level is controlled by adjusting the water supply regulating valve based on the signal from the lower limiter. sets a lower limit of the opening degree of the water supply regulating valve in advance, and when a request signal is received below the opening degree of the lower limit, adjusts the blowdown flow rate regulating valve based on the input/output deviation signal of the lower limit limiter; Since the reactor water level is controlled in this way, the feed water adjustment valve and the blowdown flow rate adjustment valve can be automatically and continuously controlled even when the reactor is started or stopped. Therefore, excellent practical effects have been confirmed in that the burden on the operator can be reduced, the reactor water level control itself can be performed reliably, stably, and with good control, and in this case, the valve opening can be arbitrarily limited.

[Effects of the Invention] According to the reactor water level control device of the present invention, the output of the main water level controller can be used in the range from the blowdown flow rate adjustment valve fully open (-100%) to the feed water adjustment valve fully open (+100%). Since the water supply adjustment valve and blowdown flow rate adjustment valve can be used differently depending on the polarity region, the water level can be automatically controlled over a wide range, and the valve opening can be limited. It has many practical effects and greatly contributes to reducing the burden on operators and stabilizing water level control. In particular, since the valve opening degree can be limited in advance, remarkable practical effects can be obtained when applied to cases where the valve opening degree needs to be limited.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention,
Figure 1 is a schematic system configuration diagram around the reactor, and Figure 2 is a block diagram of reactor water level control. FIG. 3 is a schematic diagram showing the water supply of a general nuclear reactor. 3... Nuclear reactor, 5... Water supply adjustment valve, 6... Blowdown flow rate adjustment valve, 7... Water level setting value, 8...
Water level detection value (water level signal), 11...lower limit limiter,
12... Deviation signal.

Claims (1)

[Claims] 1. A water supply control device having a reactor water supply regulating valve;
In a reactor water level control device that controls the water level of a reactor in a boiling water nuclear power plant equipped with a reactor purification device having a blowdown flow rate adjustment valve at the time of reactor startup and shutdown, water level setting value and water level detection are used. The output of the main water level controller, which calculates the deviation from the value and creates the valve opening request signal, is input to the lower limiter.
The lower limit limiter sets the lower limit of the opening degree of the water supply adjustment valve in advance, and controls the water level by adjusting the water supply adjustment valve according to the signal from the lower limit limiter. 1. A nuclear reactor water level control system, characterized in that, when the blowdown flow rate is exceeded, the blowdown flow rate adjustment valve is adjusted based on the input/output deviation signal of the lower limiter, thereby controlling the reactor water level. 2. The blowdown flow rate adjustment valve is adjusted via an opening calculator, and the gain of the opening calculator is corrected based on a separately detected reactor pressure signal and is made dependent on the reactor pressure signal. The reactor water level control device according to claim 1, further comprising an upper limit limiter.