JPS6026480B2 - Nuclear power plant output control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an output control device for a nuclear power plant, and more particularly, to a power control device for a nuclear power plant, in particular at least two systems for forcibly circulating coolant into a nuclear reactor core through a coolant mixing lamp section installed in front of the reactor core. This invention relates to a new output control device for a nuclear power plant that minimizes output fluctuations when operating a boiling water nuclear power plant equipped with a recirculation system in an unstable region.

Generally, when controlling the output of a boiling water nuclear power plant,
This is done by making the recirculation flow rate of the reactor core flow variable. Figure 1 is a block diagram showing the relationship between the recirculation system equipment and control system of a typical boiling water nuclear power plant. In the figure, 1 is the reactor, 2A and 2B are the recirculation system piping, and 3
A, 3B are recirculation pumps, 4A, 4B are electric motors, 5A,
5B is a variable frequency power supply; 6A and 6B are controllers for the variable frequency power supplies 5A and 5B; 7A and 7B are frequency request signals;
8 is a main controller, 10A is a main steam flow rate signal, 10B is a load setting signal, and 11 is a deviation device that takes the deviation of each of the signals LOA and 10B and outputs a deviation signal 11A.

As is clear from Figure 1, the recirculation system piping 2 of the reactor 1
Recirculation pumps 3A and 3B installed in A and 2B are electric motors 4A
, 4B, and the rotational speed of the electric motors 4A, 4B is variably controlled by variably controlling the frequency of the power supplied from the variable frequency power sources 5A, 5B.

The coolant sent into the reactor 1 from the recirculation pumps 3A and 3B passes through jet pumps placed around the outer periphery of the reactor core, and after being thoroughly mixed in a common plenum formed at the bottom of the core, the coolant is mixed across the ocean. , passed through the reactor core. The frequency request signals 7A, 7B are given from the main controller 8 based on the deviation 11A between the main steam flow rate signal 10A and the load setting signal 10B. However, in the operating range of conventional recirculation systems, it has become clear that, depending on the characteristics of the equipment, oscillations with a certain period occur within a certain flow rate range of the recirculation flow rate.

This recirculation flow rate oscillations can create core flow rate oscillations, which can result in fluctuations in power plant output and high-cycle vibration-induced stress on reactor components, such as the jet pumps, in the reactor wirework. Conventionally, this required measures such as limiting the control range of the recirculation system and relying on the skilled operation of operators when increasing the output at power plant start-up.
Therefore, the object of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
Even when producing reactor output that corresponds to the unstable region of the recirculation system where the recirculation flow rate oscillates, it is possible to operate without oscillations in the recirculation flow rate, reducing output oscillations and high cycle fatigue of equipment. An object of the present invention is to provide a new output control device for a nuclear power plant that can solve the problem.

FIG. 2 is a partial block diagram of an output control device for a nuclear power plant according to an embodiment of the present invention. The difference from the configuration shown in FIG. 201 and another frequency request signal 2 as its output.
0A, 208 is obtained and given to the controllers 6A, 6B.

FIG. 3 is a schematic configuration diagram showing the detailed configuration of the operating device 20 in FIG. A judgment command device compares the lower limit PI and upper limit P2 of the applicable frequency and outputs a signal 21B when PI≦8ASP2; 23 and 24 are switch relays that are turned on depending on the output signal 21B of the judgment command device 21; 22 is a A bias signal generator 25 generates a bias signal 22A corresponding to P2-PI, and 25 generates the bias signal 22A from the input frequency request signal 8A.
a subtracter that subtracts and outputs a frequency request signal 20B;
26 is an adder that adds the bias signal 22A to the input frequency request signal 8A and outputs the frequency request signal 20A. The operation of the configuration as described above will be explained below with reference to the characteristic diagram shown in FIG.

By the way, in FIGS. 4a and 4b, the vertical axis shows the variable frequency power supply 5A,
5B is taken from 0 to 100% of the variable frequency range, and time t is taken as the axis, and the figure a shows the frequency request signal 8A,
b indicates the frequency request signals 20A and 20B, respectively. Note that the range of PI to P2% of the vertical axis frequency is an unstable region of the recirculation system. Now, when controlling the output of the reactor 1, the main steam flow rate is 10A and the load setting signal is 10A.
It is assumed that the main controller 8 performs control calculations based on the deviation signal 11A obtained by inputting B into the deviation device 11, and the obtained frequency request signal 8A changes as shown in FIG. 4a with time t. . In such a case, in the slave output control device as shown in FIG. The recirculation system exhibits unstable behavior during the period from time t3, which is reached, to time L, which is above P-shape, causing various problems.

On the other hand, according to the configurations shown in FIGS. 2 and 3, while the frequency request signal 8A is between P2 and PI, the bias signal 2 from the bias signal generator 22 is applied to the signal 8A.
2A is added through the switch relay 23 and the adder 26, and simultaneously subtracted through the switch relay 24 and the subtracter 25, and as shown in FIG. It is applied to controllers 6A and 68 of variable frequency power supplies 5A and 5B. Both recirculation pumps 3A, 3B operate at constant speed with respect to each other.
Although it is generally desirable to perform so-called symmetrical driving, depending on the driving conditions, there may be a permissible range in which speed differences are within a predetermined range, excluding prohibited ranges in which extreme speed differences may occur. do. The two request signals 20A, 20B generally have values corresponding to a speed difference within their allowable range.

The coolants supplied at different speeds from the recirculation pumps 3A and 3B are mixed in the lower core plenum in the reactor 1 and circulated into the reactor core. Two frequency request signals 20A, 2
Since 0B changes stepwise in the unstable region between P2 and PI, the recirculation system passes through the unstable region at the maximum response speed of the variable frequency power supplies 5A and 5B. Therefore, it is possible to minimize the influence of instability caused by the characteristics of the recirculation system equipment. As described above, according to the present invention, the unstable characteristics of the recirculation system equipment of a nuclear power plant can be minimized, thereby reducing the instability of the power plant output that is applied to the power system and the high level of reactor equipment. The output of a nuclear power plant is effective in minimizing cycle fatigue, improving the operating performance of the nuclear power plant by expanding the operating range of the recirculation system, and reducing the burden on operators. It is possible to obtain a control device.

Brief Description of the Drawings Fig. 1 is a block diagram showing the relationship between recirculation system equipment and control system of a general boiling water nuclear power plant, and Fig. 2 shows the output of a nuclear power plant according to an embodiment of the present invention. A partial block diagram of the control device, FIG. 3 is a schematic configuration diagram showing the detailed configuration of the operating device in FIG. 2, and FIGS. 4a and 4b are characteristic diagrams for explaining the operation of FIGS. It is.

1... Nuclear reactor, 3A, 3B... Recirculation pump,
5A, 5B. ...Variable frequency power supply, 6A, 6B.
・・・． ...Controller, 8...Main controller, 11...
... Deviation device, 20 ... Operating device, 22 ...
...・Bias signal generator.

Many Z prisoners Many Z prisoners multi-a diagram Multi 4 figures

Claims (1)

[Scope of Claims] 1. At least 2 forcible circulation of coolant into the reactor core through a coolant mixing and stirring section disposed in front of the reactor core.
The recirculation system of the system, the recirculation pump provided for each recirculation system to drive this recirculation system, the electric motor that drives this recirculation pump, and the flow rate and load requirements of the recirculation system. a first control means for generating a required frequency signal for the electric motor; and when the required frequency signal is not included in a predetermined specific frequency range, the required frequency signal is directly used as a control frequency signal corresponding to each electric motor; When the requested frequency signal is included in the frequency domain, the requested frequency signal is converted into a one-sided average value and at least two control frequency signals not included in the frequency domain, and these signals are converted into at least two control frequency signals that are not included in the frequency domain. a second control means for outputting;
An output control device for a nuclear power plant, comprising a device for controlling the frequency of each of the electric motors based on the output of the second control means. 2. In the output control device for a nuclear power plant according to claim 1, the second control means is configured to control the required frequency signal when the required frequency signal is in a predetermined frequency range. out of the frequency range,
1. An output control device for a nuclear power plant, comprising an arithmetic means for adding at least two appropriate biases such that the sum becomes zero, and outputting the result as a control frequency signal.