JPS60235092A - Emergency core cooling device 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 an emergency core cooling system for a nuclear reactor, and in particular to an emergency core cooling system for a nuclear reactor, which can quickly replenish coolant in the event of a loss of coolant accident due to a rupture of a reactor pipe or the like. Relating to a reactor emergency core cooling system.

[Technical background of the invention and its problems] Coolant plays a very important role in water-cooled nuclear reactors such as boiling water reactors, pressurized wood reactors, and natural circulation reactors. Various measures have been taken to replenish coolant in the event of a loss of coolant in the reactor pressure vessel due to pipe rupture, etc.

This will be explained with reference to FIG. 1, which is a schematic diagram of a general natural circulation nuclear reactor. As shown in the figure, a cylindrical shroud 2 is provided concentrically within a reactor pressure vessel 1, and a reactor core 3 is disposed within the shroud 2.

Further, a downcomer portion 4 having an annular cross section is formed by the inner wall surface of the reactor pressure vessel 1 and the shroud 2, and a plurality of heat exchangers 5 are provided above the downcomer portion 4.

Thus, the coolant in the core 3 is heated by the heat generated in the core 3 and rises through the riser section 6 in the upper part of the core 3 while boiling, and the steam generated there is condensed in the heat exchanger 5. It falls into the downcomer section 4. Here, the density of the coolant in the core 3 and the riser part 6 and the downcomer part 4 are
Since a driving force is generated due to the difference in the density of the coolant in the downcomer section 4, the coolant in the downcomer section 4 descends and flows into the lower part of the reactor core 3, and further flows into the reactor core 3, thereby performing natural circulation cooling.

On the other hand, in order to cope with a loss of coolant accident due to a rupture of a pipe connected to the reactor pressure vessel 1, conventionally, as shown in FIG. It is placed higher than the pressure vessel 1. The reactor pressure vessel 1 and the water tank 7 are connected by a pipe 9 via a normally closed valve 8. In the unlikely event that a loss of coolant accident occurs, the valve 8 is opened and the coolant in the water tank 7 is replenished into the reactor pressure vessel 1 by gravity to maintain the reactor core in a flooded state. It is.

However, in this case of supplying the coolant only by gravity, there is a problem that the coolant cannot be supplied until the pressure inside the reactor pressure vessel 1 is sufficiently reduced. Furthermore, the flow rate after the start of coolant supply is such that the pressure inside the reactor pressure vessel 1 is lower than that in the water tank 7.
The problem is that the pressure decreases because it is higher than the internal pressure.

[Object of the Invention] The present invention has been made in view of the above circumstances, and its object is to provide a nuclear reactor that can promptly and in large quantities supply coolant into a reactor pressure vessel in the event of a loss of coolant accident. The objective is to provide an emergency core cooling system.

[Summary of the Invention 1] In order to achieve the above-mentioned object, the present invention provides a method for distributing steam generated in a reactor pressure vessel at a higher location than the reactor in the event of a loss of coolant accident due to rupture of reactor pipes, etc. This system relates to a reactor emergency core cooling system that allows the coolant in the water tank to be quickly injected into the reactor core by guiding the coolant into the water tank and making the pressure in the water tank equal to the pressure in the reactor pressure vessel. .

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 3 and 4. Note that the same parts in the figure as in FIG. 2 are given the same reference numerals and will be explained. As shown in the figure, a water tank 7 for storing coolant is placed higher than the reactor pressure vessel 1, and the space between the reactor pressure vessel 1 and the water tank 7 is normally closed. It is connected by piping 9 via a valve 8. Also, piping 1 for introducing steam generated in the reactor pressure vessel 1 into the water tank 7 in the event of a loss of coolant accident.
1 is disposed between the upper part of the reactor pressure vessel 1 and the upper part of the water tank 7, and a valve 10 is installed in the middle of this piping 11 in a normally closed state. Furthermore, a differential pressure gauge 12 for measuring the pressure difference between the reactor pressure vessel 1 and the water tank 7 is connected to the reactor pressure vessel 1 and the water tank 7.
It is attached to the differential pressure pipe 13 provided between.

Now, assuming that a coolant loss accident occurs,
When a loss of coolant accident occurs, the valve 10 is immediately opened and the steam generated in the reactor pressure vessel 1 is guided through the pipe 11 above the water level of the water tank 7.

Then, the pressure in the reactor pressure vessel 1 decreases while the pressure in the water tank 7 increases, so that the pressure in the reactor pressure vessel 1 and the pressure in the water tank 7 become approximately equal after a while. The pressure difference between the two is monitored by a differential pressure gauge 12 provided in the differential pressure pipe 13, and when the differential pressure becomes sufficiently small, a pressure difference between the two is monitored by a differential pressure gauge 12 provided in the pipe 9 that connects the water tank 7 and the reactor pressure vessel 1. When the valve 8 is opened, water in the water tank 7 is immediately injected into the reactor pressure vessel 1 via the pipe 9.

Furthermore, if a floating plate (not shown) is placed on the water surface of the water tank 7 and the steam from the reactor pressure vessel 1 is introduced onto this floating plate, the condensation of the introduced steam will be reduced. Cooling water can be injected into the reactor pressure vessel 1 more quickly.

FIG. 4 is a diagram showing changes in the amount of coolant supplied after a pipe rupture. ) does not fall sufficiently, the cooling water in the water tank will not flow into the reactor pressure vessel. On the other hand, in the case of the present invention, as shown by the solid line, the pressure d in the water tank (double-dashed line) increases with time, so the coolant supply amount C is cooled even when the pressure in the reactor pressure vessel is high. Water will be supplied. Therefore, it can be seen that the drop in the water level in the reactor pressure vessel can be suppressed to a minimum. To further explain this with respect to the diagram in Figure 5 that shows the change in water level in the reactor pressure vessel after a pipe rupture occurs, in the case of the conventional equipment, the change e in the water level in the reactor pressure vessel after a rupture occurs is , as shown by the dotted line, and it takes a considerable amount of time for the water level to recover.In contrast, in the case of the present invention, the water level change t is smaller than the conventional water level change e, as shown by the solid line. It turns out that it is small. Therefore, the time required to restore the water level is also much shorter than in conventional devices. Note that the top position of the core is indicated by g (dotted chain line).

[Effects of the Invention] According to the reactor emergency core cooling system of the present invention, it is possible to quickly supply a large amount of coolant in the event of a cold member loss accident in a nuclear reactor, so that the reactor pressure vessel is The time required for water level recovery can be shortened, and heating phenomena in the reactor core can be reliably prevented. Therefore, the reliability of the core cooling of the nuclear reactor is increased, which has the excellent effect of improving its safety.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a conventional natural circulation nuclear reactor, Figure 2 is a schematic diagram of a conventional nuclear reactor plant, Figure 3 is a schematic diagram of an embodiment of the present invention, and Figure 4 is a piping diagram. FIG. 5 is a diagram showing the amount of coolant supplied and pressure changes in the reactor pressure vessel and the water tank after a pipe break occurs. FIG. 5 is a diagram showing changes in the water level in the reactor pressure vessel after a pipe break occurs. 1...Reactor pressure vessel 3...Reactor core 7...Water tank
8.10... Valve 9.11... Piping 12... Differential pressure gauge Agent Patent attorney Noriyuki Chika (and 1 other person) Figure 1

Claims (2)

[Claims] (1) In the reactor emergency core cooling system that supplies coolant to the reactor core in the reactor pressure vessel in the event of a loss of coolant accident due to a rupture of a reactor pipe, etc., the water head difference between the reactor pressure vessel and the An emergency core cooling system for a nuclear reactor, characterized in that a water tank having a water tank is provided, and piping is provided to guide steam generated in the reactor pressure vessel to the water tank at the time of the loss of coolant accident. (2) The emergency reactor core cooling system according to claim 1, wherein a floating plate is placed on the water surface in the water tank and steam from the reactor pressure vessel is introduced onto the floating plate.