JPH0112238Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a boiling water reactor (hereinafter referred to as
This invention relates to a pump power supply system for BWR (BWR) that prevents all pumps from tripping at the same time even in the event of pump power loss, alleviates the sudden decrease in core flow rate due to pump tripping, and maintains the integrity of fuel rods.

In a BWR plant with multiple internal pumps as coolant recirculation pumps, the moment of inertia of the pump motor is
Very small compared to set recirculation type pump motors. Therefore, the coastdown characteristic of the rotation speed when the pump power supply is lost is about 1/5 to 1/10 faster than that of the conventional MG set system. Therefore,
In a BWR plant with an internal pump, if the pump power is lost during output operation, the recirculation flow rate will sharply decrease, which will impair the heat removal effect of the coolant from the fuel rods, threatening the integrity of the fuel rods. That is,
In a BWR plant, a decrease in core flow rate leads to a decrease in power output, but the heat flux from the fuel rods has a certain time constant, and if the core flow rate decreases faster than this time constant, the heat flux will decrease. Because of the mismatch between the decrease in heat flux and the decrease in flow rate, the heat flux from the fuel rods is not removed, which is unfavorable in terms of the health of the fuel rods.

The purpose of this invention was to eliminate the above-mentioned drawbacks. By separating the internal pump power supply system, all pumps will not trip at the same time, and even when the core flow rate decreases due to loss of pump power supply. An object of the present invention is to provide a power supply device for an internal pump that maintains the health of fuel.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic diagram of a power supply device for a conventional MG set type BWR plant.
Normally, the two recirculation pump motors 1 are connected from the main generator 2 to separate busbars 4 via separate station transformers (3, hereinafter referred to as station transformers), so that power loss in both systems does not occur at the same time. I have made sure that there is no such thing. Even if an abnormality occurs upstream of station 3 and the power to two recirculation pump motors 1 is lost at the same time, in the conventional MG set plant, the moment of inertia of the recirculation pump motors is large, and the core flow rate due to pump tripping is reduced. The decrease is gradual and does not represent a severe transient change. On the other hand, FIG. 2 shows a case where such a method is applied to an internal pump plant. Internal pump is conventional MG
Usually, around 10 internal pumps are used as recirculation pumps, which have a smaller pump capacity than recirculation pumps in set plants. FIG. 2 shows a schematic diagram of the power supply device in the case where the number of pumps is 10, as an example. Internal pump motor 8
As in the case of the MG set platform shown in Fig. 1, half of the units are connected to separate busbars. If power is lost in both systems at the same time due to an abnormality in the power system, the inertia of the pumps is small, so even if the configuration is similar to that shown in Figure 1, the core flow rate will decrease quickly and cause a very severe transient change. Become.

Next, a power supply device according to the present invention is shown in FIG.
The internal pump system consists of 10 internal pumps, and half of the 10 internal pump motors 8 that drive these internal pumps are connected to the phase separation bus 7 through the station transformer 3.
The remaining half is the starting transformer (6b, hereinafter abbreviated as starting transformer)
It is connected to another bus bar 4b via. Here, 6 is used for starting up the plant, etc.
This system is also provided in conventional plants and is shown in dotted lines in FIGS. 1, 2 and 3. In the present invention, power for half of the internal pump motors 8b is supplied from this startup 6b not only when starting up the plant but also at all times. Normally, the busbar of this generator 6b is in a separate system from the busbar 7 of the main generator 2, and it is rare that an abnormality occurs in both of them at the same time, resulting in power loss.

Next, the operation of the present invention will be explained. In the conventional power supply apparatus as shown in FIGS. 1 and 2, the pump power supply is completely lost when there is an abnormality in the main generator 2 or an abnormality in the system. In the power supply device according to the present invention as shown in FIG. Only half of the pump motors are connected to the busbar, and the other half of the pump motors are supplied with power from the busbar on the side of the generator 6b and will not trip. Since it is rare for the bus on the station side and the bus on the generating side to lose power at the same time, it is rare for such a power supply to cause all internal pumps to trip at the same time, compared to the power supply shown in Figure 2. Make it smaller stochastically.

Next, the effects of the present invention will be explained. As mentioned above, in the power supply system of the present invention as shown in Figure 3, even if an abnormality occurred that would cause all pumps to trip at the same time, only half of the pumps would trip at the same time, and a sudden decrease in core flow rate could be avoided. It will be done.
The fourth section compares the transient changes in surface heat flux and core flow rate when a power loss occurs in a plant with a power supply device as shown in Fig. 2 and a plant with a power supply device according to the present invention as shown in Fig. 3. As shown in the figure. In the figure, curve 1
is the surface heat flux of the present invention, curve 2 is the conventional example, curve 3 is
curve 4 shows the core flow rate of the present invention, and curve 4 shows the conventional example. The surface heat flux is determined by the fuel rod time constant (approximately 5
~7 seconds) determines how it will fall, so the two are almost the same. On the other hand, there is a large difference in the core flow rate between when all internal pumps trip and when half of the internal pumps trip, and the mismatch between the surface heat flux and the flow rate is smaller in the case according to the present invention. Therefore, if the present invention is used, even in the event of a total power loss, all internal pumps will not trip and the core flow rate will not suddenly decrease, so that the integrity of the fuel during a transient situation can be sufficiently maintained. The device described here is an example in which there are 10 internal pump motors and these are divided into two systems, and the same method as the present invention can be used even if the number of pump motors or the number of system separations is different. It goes without saying that similar effects can be obtained by selecting the optimal power supply (this can be confirmed through analysis).

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a power supply system for a conventional MG set type BWR plant, Fig. 2 is a schematic diagram of a power supply system for a similar internal pump plant, and Fig. 3 is a schematic diagram of a power supply system for a similar internal pump plant. A schematic system diagram showing the power supply equipment of the plant. Figure 4 is a curve showing a comparison of surface heat flux and transient change in core flow rate when a power loss occurs for the power supply equipment shown in Figures 2 and 3. It is a diagram. 1... Recirculation MG set drive motor, 2... Main generator, 3... Station transformer (station transformer), 4... Bus bar,
5...Main transformer, 6...Starting transformer (starting), 7
...Phase separation bus bar, 8...Internal pump motor.

Claims (1)

[Scope of utility model registration request] a plurality of first internal pumps and a plurality of second internal pumps;
In an internal pump power supply device that supplies power to an internal pump system consisting of an internal pump, the first internal pump is connected to the station transformer and the first starting transformer and supplies power only to the first internal pump. 1. A power supply device for an internal pump, comprising a first busbar and a second busbar connected only to a second starting transformer and supplying power only to a second internal pump.