JPS61231308A - Method of controlling feed pump for nuclear reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for controlling water supply to a nuclear reactor, and particularly to a method for controlling water supply to a nuclear reactor when switching the operation mode of a water supply pump.

[Technical Background of the Invention and its Problems] For example, a feed water pump for a boiling water nuclear reactor with a rated output of I100 MW is composed of WI number of turbine-driven pumps and motor-driven pumps. However, when the reactor output is low, a motor-driven water punch (hereinafter referred to as M'-"
A turbine-driven water pump (hereinafter referred to as T-RFP) is used in the process of increasing the power.

Furthermore, since another T-RFP is activated in the process of increasing the output, the number of T-RFPs in operation is increased. A method of controlling the flow rate when switching the operation mode of the water supply pump will be described below with reference to the drawings.

FIG. 4 is a system diagram of a water supply system consisting of two M-RFPs and two T-RFPs. In the figure, the steam generated in the reactor 1 passes through the main steam pipe 2 and drives the turbine 3, so the steam generated in the reactor 1 is directly connected to the turbine 3. 11a4 generates electricity.

The steam that has done work in the turbine 3 is condensed and stored in the condenser 5. The water stored in the condensate a5 is pressurized by the condensate pump 6, pushed into the feed water pump suction header 7 on the feed water pump suction side, branched to each feed water pump, and merged again at the feed water pump discharge header 8 to the reactor reactor. Injected into 1.

Among the water supply pumps in this water supply system, T-RFP9 and 10
are driven by turbines 13 and 14, respectively, and turbines 13 and 14 are driven by steam control valves 15, respectively.
and 16.

The water supply from T-RFPs 9 and 10 is controlled by the water supply control system by operating steam control valves 15.16 to adjust the rotational speed of turbines 33.14. In addition, the water supply from other water pumps M-RFPll and 12 is
Flow control valve (hereinafter abbreviated as FCV) provided on the discharge side of M-RFPll, 12 by the water supply control system 17.1
It is controlled by operating 8. Water pump 9.1
A feed water recirculation line returning to the condenser 5 is provided on the discharge side of the 0.11.12. This feed water recirculation line is provided to ensure the minimum flow rate (hereinafter referred to as minimum flow) required to protect each pump from overheating even when the water supply from the water pumps 9.10.11.12 is low. There is.

In order to adjust such a minimum flow, a flow rate adjustment valve (hereinafter referred to as a minimum 70-valve) 19, 20.21.2
2 is provided, minimum flow valve 19.20.2
1.22 is controlled by a minimum flow control system.

By the way, when switching the water supply pump operation mode, changes in the water supply flow rate from the water supply pump to be started or stopped and the opening and closing of the minimum flow valve act as disturbances on the water supply flow rate. This will be explained, for example, by assuming that the rated flow rate of the T-RFPI unit is 50% of the rated total water supply flow rate, and the rated flow rate of one M-RFP unit is 25% of the rated total water supply flow rate, and switching the water pump operation mode.

When switching the operation mode from M-RFP11 operation to T-RFP9 operation, the water supply flow rate from T-RFP9 is increased and the water supply flow rate from M-RFPil is decreased, but at the beginning of this process, T-RFP
In order to ensure the minimum flow of T-RFP 9, the minimum flow valve 19 is closed in advance, and as the water supply flow rate from T-RFP 9 increases and the minimum flow can be ensured, the minimum flow valve 19 is gradually closed. Ta.

Further from T-RFP9 operation: When starting T-RFP10 and switching the operation mode to T-RFP2 operation, increase the water supply flow rate from T-RFPlo and
The water supply flow rate from P9 is reduced, but in order to ensure the minimum flow of T-RF PIO in this process, the minimum flow valve 20 is opened in advance, and the T-R
The minimum flow valve 20 was gradually closed as the water supply flow rate from the FPIO became secure.

However, with such conventional technology, when automatically controlling the minimum flow, it is impossible to control the minimum flow valve at an arbitrary opening degree, and once the minimum flow valve starts to close, a constant change determined by the opening speed of the minimum flow valve occurs. It closes at a high rate and ends up fully open.

On the other hand, in boiling water reactors, fluctuations in water level are strictly limited from the standpoint of cooling the reactor core. That is, the structure is such that the main turbine trip is activated when the water level rises, and the reactor scram and emergency core cooling system are activated when the water level drops. Therefore, the switching operation of the water pump operation mode should be performed carefully by experienced operators.
It was going on for a long time. Even if this water supply pump operation mode switching operation is performed using a computer instead of manual operation by an operator, if the configuration of the conventional water supply control device remains unchanged, it will still take a long time, and the automatic control of the minimum flow valve will also have the problems described above. occurs. This will be explained with reference to FIG. 5, which shows a conventional water supply control device, and FIG. 6, which shows changes in head with respect to minimum flow disturbances.

In FIG. 5, the water level controller 31 is a proportional-integral (PI)
It is composed of a controller and a series compensator, and outputs a water level signal 32 . as a feedback signal to the water level controller 31 . Total feed water flow ω signal 33. There is a mode (three-element control) using the three steam hot stone signals 34 and a mode (single-element control) using only the water level signal 32. The reactor output when switching from M-RFP11 operation to T-RFP9 operation is approximately 25
%, and single-element control mode is normally used at such low outputs. Water level controller output 35 is selector switch 3
6.37° It is sent as a water supply command to each pump via 38 and 39. Note that 40, 41, 42, and 43 are water supply command output terminals 44°45, and 46.47 are manual water supply command input terminals. In FIG. 5, M connected to the changeover switch 38
- Only RFPll is in automatic mode, T-RFP9 is in manual mode for speed increase, and the other two T-RFPlo, M
- RFP12 is not involved in the switching. T-RFP9
Even if the speed increases, water supply will not start unless the discharge pressure of the T-RFP 9 becomes equal to or higher than the water supply pump discharge header pressure. Here, it is assumed that the discharge pressure of T-RFP9 has already been increased to the water supply pump discharge header pressure, and the speed increase command signal value required for this pressure increase is added as a bias to the water supply command value of T-RFP9. do. Therefore, when a speed increase command is input to the manual operation device of the T-RFP 9, water supply from the T-RFP 9 is started, the total supply and water flow increase, and the water level rises. This rise in water level is fed back to the water level controller 31, the water level controller output 35 decreases, and the water supply from the M-RFPll is throttled and eventually becomes zero.

Then, when the input signal to the operating end of the changeover switch 36 becomes equal to the water level controller output 35, the mode is changed to automatic mode. Since the water pump operation mode is switched using fluctuations in the water level in this way, only small fluctuations in the water level are allowed in the case of a nuclear reactor, and therefore this switching takes a long time.

Next, using FIG. 6, it will be explained that the minimum flow valve cannot be controlled at an arbitrary opening degree using the conventional control method. In the figure, 51 is a curve showing the pressure against the flow rate flowing into the water supply pump suction header, and 52 is a curve showing the pressure at the water supply pump discharge header against the total water supply flow rate.

Now, M-RFPll and T-RFP9 are working,
If the total water supply flow rate is QO, that is, operating at point A on the curve 52, the head at this time is HO.

The total water supply flow 11Qo is controlled to be constant by adjusting the water supply from M-RFPII. That is, the water supply pump header pressure remains at HO and remains unchanged. T-RFP
The minimum flow valve 9 is open and the flow rate flowing into the water pump suction header is Ql (>QO). Here, the operating point on the curve 51 is shown as 8. T-R,F
The water supply flow rate from P9 is Q2, and the head height HO on the curve 53 showing the discharge pressure of T-RFP9 with the rotation speed constant
In other words, it is operating at 0 point. In order to clarify the influence of the minimum flow rate, T,,7 RF P,9
The rotation speed of is constant. When the minimum flow valve 19 is adjusted and the minimum flow is decreased by ql, the operating point moves from point 8 to point D on the curve 51, and the head increases by h. Therefore, the discharge pressure of the T-RFP 9 also increases, and the rotation speed characteristic curve shifts from the curve 53 to the curve 54. And T-RFP
9 moves from the 0 point on the curve 53 to the point where the head on the curve 54 is HO, that is, the E point. When moving from point 0 to point E, the water supply flow rate from T - R, F P 9 increases by q2. Therefore, the suction flow rate of T-RFP9 is Q2-Q
This means that it has increased by l.

The magnitude relationship between q2 and ql is determined by the slopes of the curves 51 and 54 around their respective operating points. Normal Q2 >ql
This is the relationship. That is, when the minimum flow valve is closed, the suction flow rate of the T-RFP 9 increases. Conversely, when the minimum 70-valve is further opened, the T
- The suction flow rate of RFP9 decreases. On the other hand, the automatic control device (including interlock) for the minimum flow valve is usually configured to open the minimum flow valve when the suction flow rate is below the minimum flow, and close it when the suction* amount exceeds the minimum flow. ing. Therefore, once the minimum flow valve 19 begins to close, the suction flow rate increases, the minimum flow control device further closes the minimum flow valve 19, and the minimum flow valve 19 is fully opened due to the time constant unique to the minimum flow valve. On the contrary, once the minimum flow valve 70-valve 19 starts to open, it becomes fully open due to the time constant specific to the minimum flow valve, causing a problem that continuous control of the minimum flow valve 19 becomes impossible.

As explained above, from the operation of one M-RFP to the T-RF
Continuous automatic control of the minimum flow valve is not possible when switching the operation mode to P1 unit operation, but this
Switching the operation mode from one unit operation to two T-RFP units operation or the water level controller is a three-element control or the water supply turbine 13 is not simply a manual input to the operating end of the changeover switch 36.
Even if a deviation signal from the actual rotational speed is input, the above-mentioned problem will occur.

Furthermore, even in a water supply control system in which a control device (PID controller) for controlling the water supply flow rate of each water supply pump is added to the water level controller 31 in a cascade as shown in FIG. Even if a speed increase command is input to the operating end of the controller, the same problem as described above will occur. In addition, in Fig. 7, 61.62° 63 and 64 are T-RFP, respectively.
9. T-RF PIO.

These are the water supply flow rate signals of M-RFPll and M-RFP12, and 65.66, 67, and 68 are the signals of T-RFP9. T
- It is a flow rate controller (PID controller) for RFPIO, M-RFPll, and M-RFP12.

[Object of the Invention] The present invention has been made in view of the above circumstances, and its purpose is to reduce fluctuations in the reactor water level and to enable continuous automatic control of the minimum flow valve when switching the operation mode of the reactor feed water pump. An object of the present invention is to provide a method for controlling a reactor feed water pump to achieve the desired results.

[Summary of the Invention] In order to achieve the above object, the present invention provides a water level controller and a flow rate controller that controls the discharge flow rate of each of the water pumps in a water supply control system of a nuclear power plant having a plurality of water supply pumps. is provided for each water supply pump, and a gain conversion section is provided in the water supply command signal transmitted from the water level controller to each flow rate controller, and the gain value of the gain conversion section is changed to operate the water supply pump. The present invention relates to a nuclear reactor feed water pump control method that switches modes.

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

FIG. 1 is a block diagram of an embodiment of the present invention, in which a water level controller 31 includes a water level signal 32. A feedwater flow rate signal 33 and a steam flow rate signal 34 are input.

Variable gain 71.72.73.7 for water level controller output 35
Multiply by 4 to calculate each water pump, i.e. T-RFP9.7-R.
The water supply command value to FPIO, 1vl-RFPll, and M-RFP12 is the water supply flow rate signal 61°6 of each pump.
2, 63.64 is negatively fed back and the deviation signal is sent to each water supply bottle 7T-RFP9. T-RFPlo, M-RFPll
, M-RF PI3 flow controller 65, 66, 67,
68. Each flow controller 65.613.67,6
8 (PID controller) outputs a rotation speed command and an FCV opening command, which are the amount of water supply flow rate operation for each water supply pump.

Next, F of the water supply pump operation mode of this embodiment with the above configuration.
JJ replacement will be explained.

Now, assuming that the reactor output is 25%, the feedwater flow rate signals of each feedwater pump are 0% for 61, 0% for 62, and 25% for 63.
%, 64 indicates 0%. Here, the water level controller 31 is set in single element mode. Next, when switching the water pump operation mode from M-RFPll to T-RFP9, the variable gain 71 of the T-RFP9 to start and the variable gain 73 of the M-RFPll to stop are changed as shown in FIG. 2. .

That is, the variable gain 73 of M-RFPll is set to gain 1.
T-RFP decreases linearly from gain O to
The variable gain 71 of No. 9 is changed so as to increase linearly from a gain of O to a gain of 1. Also, T-R
The gains 72.74 of FPlo and M-RFP12 are left as O.

When you switch the water pump operation mode as described above,
Since the water supply command of each water supply pump is changed while the water level controller is always operating and is not dependent on the fluctuation of the water level as in the conventional case, the fluctuation of the water level is small and the time required for switching can be shortened. Furthermore, since the water supply flow rate of each water supply pump is controlled, the continuous control of the minimum flow valve does not cause the problems of the conventional system, and normal minimum flow control using negative feedback of the pump suction flow rate signal is possible.

Figure 3 shows how T-RFP9 according to the present invention can be used to
An example of gain change setting when switching the operation mode between two units is shown in P9.10. That is, when the reactor output is 50%, the water pump operation mode is switched from operating one T-RFP9 to operating two T-RFP9.10 by changing the variable gain 71 of the T-RFP9 from gain 1 to gain 0. 5, the variable gain 72 of T-RFPlo is changed so as to increase linearly from the gain 0 to the gain 0.5.

Gains 13 and 14 of M-RFPll and M-RFP12 are left unchanged at O. By switching the water pump operation mode in this manner, fluctuations in the water level are small and the time required for switching can be shortened. Furthermore, since the water supply flow rate of each water supply pump is controlled, minimum 70 continuous control is possible.

[Effects of the Invention] As explained above, according to the reactor feed water pump control method of the present invention, since water level fluctuations are not used as in the conventional method, the water level fluctuations are small and the water pump operation mode can be switched in a short time. Moreover, the minimum of each water pump is 70
- An excellent effect is achieved in that continuous automatic control of the valve becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram for explaining the gain change setting when switching the operation mode from M-RFP to T-RFP according to the present invention, and FIG. 3 is a diagram of the present invention. A diagram for explaining gain change settings when switching from one T-RFP to two T-RFP operation mode according to the invention,
Fig. 4 is a system diagram of a conventional reactor water supply system consisting of two M-RFPs and two T-RFPs, Fig. 5 is a block diagram of the water supply controller when switching the conventional feedwater pump operation mode, and Fig. 6 The figure is a head curve explaining the interference of minimum f〇-, No. 7
The figure is a diagram for explaining conventional water supply pump operation mode switching control using a water supply controller equipped with a flow rate controller. 1... Nuclear reactor, 2... Main steam pipe 3...
Turbine, 4... Generator 5... Condenser,
6...Condensate pump 7...Water pump suction header 8...Water pump discharge header 9.10...-T-RFP 11, 12...M-RFP 13, 14...Water supply turbine 15 , 16... Water supply turbine steam control valve 17, 18...
・・FCV 19, 20.21.22・・Minimum flow valve 31・
...Water level controller 36, 37.38.39...Manual/automatic changeover switch 65, 6B, 67, 68...Flow rate controller (873
3) Agent Patent attorney Yoshiaki Inomata (and 1 other person) Figure 1 FfrM Figure 2 Figure 3 Figure 7 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] In a water supply control system of a nuclear power plant having a plurality of water supply pumps, a water level controller and a flow rate controller for controlling the discharge flow rate of each of the water supply pumps are arranged for each water supply pump, and each flow rate is controlled from the water level controller. A reactor feed water pump control method, characterized in that a gain converter is provided in a water supply command signal transmitted to a controller, and the operation mode of the feed water pump is switched by changing the gain value of the gain converter.