JPH0644060B2 - Reactor emergency water injection system - Google Patents

Description

TECHNICAL FIELD The present invention relates to, for example, an emergency water injection device for a nuclear power plant having a pressurized water nuclear reactor, and more particularly to an accumulator water injection tank thereof.

[Prior Art] FIG. 7 is a system diagram showing a primary cooling system of a two-loop nuclear power plant having two steam generators and two primary coolant pumps. The primary coolant heated in the core 10 in the reactor vessel 1 is transferred from the reactor vessel 1 to the U-shaped heat transfer tube 8 in the steam generator 2 through the high temperature side pipe 5 of the primary cooling system closed loop 6, Therefore, heat is exchanged with the secondary coolant flowing around the heat transfer tube 8. The primary coolant pump 3 gives a water head to the primary coolant cooled by the steam generator 2,
It is returned to the inside of the reactor vessel 1 again via the low temperature side pipe 7.

In such a primary cooling system, when the accident in which the pressure is drastically reduced and the emergency water injection device operates, for example, the primary cooling loss accident accompanying the breakage accident of the piping of the primary cooling system, the pipe breakage point The core 10 is once exposed due to the outflow of the primary coolant from 9 to the outside of the system, and then the core 10 is eventually submerged by the operation of the emergency water injection device.

In this case, the reactor is shut down immediately after the accident, but it is still necessary to remove core decay heat after the reactor is shut down.
If the core is not sufficiently cooled and the exposed state of the core continues for a long period of time, it is expected that decay heat may lead to the worst situation such as core melting. Therefore, it is important for the emergency water injection device to efficiently and early supply and accumulate the emergency cooling water injected into the primary cooling system in the core in the event of the loss of the primary coolant.

Conventionally, such an accumulator water injection device has been used in the accumulator water injection tank 12
And a low pressure injection pump 18 and a high pressure injection pump 19. As shown in FIG. 7, the accumulator water injection tank 12 contains injection water 13 as emergency cooling water, and pressurized nitrogen gas 11 is enclosed in the upper part of the liquid surface. Further, the liquid phase portion is connected to the low temperature side pipe 7 through the pipe 14 via the check valve 15, and at the time of the primary cooling loss accident, the pressure of the primary cooling system is the holding pressure of the water injection tank 12 (the pressure of the pressurized sealed gas). ) When the temperature drops below, the check valve 15 automatically operates to inject a large amount of the injected water 13 into the primary cooling system.

Further, since the low-pressure injection pump 18 and the high-pressure injection pump 19 of the accumulator water injection device need to supply the emergency cooling water to the core 10 for a long time even after the water injection tank 12 releases the injection water 13. Inject water held in a large capacity water source tank (not shown) into the primary cooling system.

The reason for having two types of pumps 18 and 19 is that the pump head is low, but the low-pressure injection pump 18 has a relatively large flow rate, and the high head that can inject even at a relatively high primary system pressure although it has a small flow rate. By combining with the high pressure injection pump 19 of
This is because appropriate safety injection can be performed even for various primary cooling system pressure changes.

Figures 7 and 8 show how the primary cooling system pressure changes during a typical loss of primary coolant and how the emergency core cooling water is injected from this conventional emergency water injection system. It will be described with reference to FIG. During normal operation, the primary cooling system is kept at a high pressure (A in Fig. 8), but the low temperature side pipe 7 of the primary cooling system breaks (occurrence of the primary coolant loss accident) and the primary cooling water breaks. Ejecting from 9, the pressure in the primary cooling system drops rapidly as shown by curve 20. During this time,
The water coolant in the reactor vessel 1 becomes empty, but when the primary cooling system pressure drops below the holding pressure of the water injection tank 12 (B in FIG. 8), the injection water 13 from the water injection tank 12 reverses. It is automatically injected into the low temperature side pipe 7 through the stop valve 15 and the pipe 14. The injection flow rate from the water injection tank 12 changes as shown by the curve 21 in FIG. 8, the injection water 13 is completely discharged, and the injection is completed. On the other hand, the pressure drop of the primary cooling system is detected, the low-pressure injection pump 18 and the high-pressure injection pump 19 are started, and water injection is continued for a long time (curves 22 and 23 in FIG. 8).

The lower plenum part 17 of the reactor vessel 1 which has once been emptied by the water injection is first filled with water (this stage is called a refill stage), and then the downcomer part 16 is filled with water, and the head of the downcomer part 16 causes The core 10 is gradually submerged (this stage is called the core re-submersion stage). The reason why the speed at which the reactor core 10 is submerged is slow is that steam causes steam to be generated in the high-temperature nuclear reactor core 10 and causes pressure loss when the steam is discharged to the outside of the primary cooling system. Therefore, a large amount of water should be injected at the beginning of the refill stage and the core resubmersion stage, and the lower plenum 1
7. It is necessary to fill the downcomer part 16 with water, but after the early stage of the core re-flooding stage, since the core flooding speed is slow, it is not necessary to inject much water.

[Problems to be Solved by the Invention] As described above, the conventional device requires three types of devices, that is, a pressure-accumulation type water injection tank, a low-pressure injection pump, and a high-pressure injection pump, to complicate the system. However, there is a problem that the reliability is lowered and the cost is increased accordingly.
It is an object of the present invention to provide an emergency water injection device for a nuclear reactor that promptly solves such problems.

[Means for Solving Problems] To this end, the present invention provides an emergency water injection device for a nuclear reactor, which includes an accumulator water injection tank that communicates with a reactor primary cooling system via a communication pipe having a check valve. The outlet of the spiral diode is provided in fluid communication with the inlet of the communication pipe in the water injection tank, and the outlet of the first inflow pipe having an inlet opening to the lower part in the accumulator injection tank is provided with the inner peripheral surface of the spiral diode. The outlet of the second inflow pipe, which has an inlet opening in the circumferential direction along the above and which opens at the upper part in the pressure accumulating injection tank, with respect to the flow from the outlet of the first inflow pipe. It is characterized in that it is opened in the direction in which the flow from the second flow pipe collides.

[Operation] The check valve of the communication pipe is closed during normal operation of the plant. For example, when the internal pressure of the primary cooling system falls below the operating pressure of the check valve due to the loss of coolant in the primary cooling system, the check valve automatically opens and the injected water in the accumulator water injection tank , Enters into the spiral diode from both of the second inflow pipes and is injected at high speed into the primary cooling system via the communication pipe. At this time, since the outlets of the first and second inflow pipes are opened in the direction in which the flows from the outlets collide, the injected water flowing from the first and second inflow pipes into the spiral diode swirls. High-speed discharge from the communication tube through the inlet without substantially swirling in the diode. When this high-speed injection causes the water level in the pressure-accumulation water tank to drop, and when it reaches below the inlet of the second inflow pipe at the top of the pressure-accumulation injection tank, the injection water enters the spiral diode only from the first inflow pipe. Moreover, since there is no collision flow from the second inflow pipe, the injected water swirls in the spiral diode, and the flow to the communication pipe is throttled by the action of the centrifugal force. Therefore, it flows through the communication pipe. The flow rate of the injected water is reduced during the injection, and the accumulator water injection device shifts to the slow discharge stage.

[Embodiment] Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or corresponding portions.

FIG. 1 shows the present invention implemented in a primary cooling system of a two-loop plant having two steam generators and two primary coolant pumps, and the primary cooling system equipment of a pressurized water reactor is the same as the conventional one. In addition, it comprises a reactor vessel 1, a steam generator 2, a primary coolant pump 3, a primary cooling system closed loop 6 consisting of a primary coolant pipe connecting these, and a pressurizer 4.

The primary coolant heated in the reactor core 10 in the reactor vessel 1 passes from the reactor vessel 1 through the high temperature side pipe 5 to the U inside the steam generator 2.
The heat is transferred to the letter-shaped heat transfer tube 8 and exchanges heat with the secondary coolant flowing around the heat transfer tube 8. Then, the primary coolant cooled by the steam generator 2 is provided with a water head by the primary coolant pump 3, and is supplied again into the reactor vessel 1 through the low temperature side pipe 7. In the steam generator 2, the water cooling material of the secondary cooling system containing no radioactive substance is converted into steam and supplied to a turbine system (not shown).

The emergency water injection device connected to this primary cooling system equipment is a pressure accumulation water injection tank 101 for injecting an emergency and a large amount of emergency cooling water into the low temperature side pipe 7 of the primary cooling system loop and accumulating it in the reactor vessel 1 immediately after the accident. Is equipped with. The injection tank 101 has injection water 13 therein as emergency cooling water, and pressurized nitrogen gas 11 is sealed in the upper part of the liquid surface. In addition, the liquid phase portion communicates with the low temperature side pipe 7 through a check valve 15 and an injection water discharge pipe (communication pipe) 102.

According to the present invention, in order to eliminate the need for the conventional low-high pressure injection pump and its associated valve device (see FIG. 7), the water injection tank 101
Is configured as follows. That is, in FIG. 1 to FIG. 3, the communication pipe 102 having the check valve 15 communicates with the low temperature side pipe 7 of the primary cooling system at one end on the inlet side, and the other end 102 a from the bottom of the water injection tank 101. It extends into the interior. Communication pipe 1
The other end 102a of 02 is opened in the center of the spiral diode 103 which is a substantially cylindrical housing in the water injection tank 101, and the communication pipe 1
It is the entrance to 02. In this spiral diode 103,
A small flow pipe (first inflow) connected tangentially to the cylindrical inner peripheral surface 103c of the spiral diode 103 in fluid communication with the inside of the spiral diode 103 and two outlets 103a and 103b. Pipe) 104, large flow pipe (second inflow pipe) 105
Is provided, and one end (inlet) 104a of the small flow pipe 104 is provided.
Is open at the lower part in the pressure-accumulation injection tank 101. The large flow pipe 105 is bent at a right angle in the middle and extends upward, and its upper end (inlet) 105a is opened at the upper part in the pressure accumulation tank 101.

It is necessary that one end 104a of the small flow pipe 104 and the upper end 105a of the large flow pipe 105 are separated by a predetermined height.
Is not necessarily connected to the spiral diode 103 in a tangential direction, and the large flow tube 105 does not necessarily need to extend at a right angle to the small flow tube 104. For example, one end 1 of the small flow pipe 104
As long as the height between 04a and the upper end 105a of the large flow pipe 105 is sufficiently secured, the small flow pipe 104 has the relationship shown in FIG.
Also, the large flow pipe 105 may be arranged.

Next, the behavior when, for example, the primary coolant piping breaks and a primary coolant loss accident occurs will be described. If a breakage point 9 occurs in the low temperature side pipe 7 of the primary cooling system and the pressure of the primary cooling system decreases due to the loss of the coolant, the check valve will continue to operate as before.
15 (Fig. 1) is activated and the injection is automatically started. At the initial stage of such injection, the water injection tank 12
The water level of the injected water 13 in the large flow pipe 105 is as shown in FIG.
Is above the upper end 105a of the. In this state, inject water
Although 13 is directed to the inside of the spiral diode 103 through one end 104a of the small flow pipe 104 and the upper end 105a of the large flow pipe 105, the two outlets 103a and 103b of the small flow pipe 104 and the large flow pipe 105 face each other. Therefore, the two injected water streams enter the communication pipe 102 through the inlet 102a while colliding.

When the water level drops below the upper end 105a of the large flow tube 105 as shown in FIG. 4, the flow to the swirl diode is only from the small flow tube 104, so that the flow in FIG. As shown in the drawing, the centrifugal force is generated, and the action causes the flow rate in the communication pipe 102 to be reduced. Therefore, it becomes possible to flow a large flow rate at the beginning of the injection and a small flow rate at the latter stage.

[Effects of the Invention] As described above, when the emergency water injection device according to the present invention is used, the water level in the water injection tank is automatically detected, the outflow rate of the infused water decreases during the infusion, and the infusion time is extended. As a result, not only the low-pressure injection pump, which was indispensable for conventional emergency core cooling equipment, can be omitted, but the moving parts can be eliminated altogether, which simplifies the system and provides high reliability. It is possible to obtain a high degree and to realize cost reduction.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a reactor primary cooling system equipped with an emergency core cooling system having an emergency water injection device according to the present invention, and FIG. 2 shows a case where a pressure accumulation water tank of the emergency water injection device of FIG. 1 is full. Fig. 3 is a schematic diagram showing Fig. 3, a sectional view taken along the line III-III in Fig. 2, and Fig. 4 is a schematic diagram showing the accumulator water injection tank in the emergency water injection device in Fig. 1 when water is reduced, Fig. 5 Is the fourth
FIG. 6 is a cross-sectional view taken along the line V-V in FIG. 6, FIG. 6 is a cross-sectional view showing another arrangement example of the inflow pipe with respect to the spiral diode, and FIG. 7 is an emergency core cooling equipment having a conventional emergency water injection device. FIG. 8 is a schematic diagram of the reactor primary cooling system provided, and is a curve diagram showing a flow rate characteristic injected from the conventional emergency water injection device to the primary cooling system in the event of a loss of pressurized water reactor primary coolant. 13 ... Injection water, 15 ... Check valve 101 ... Accumulation water injection tank 102 ... Communication pipe (injection water discharge pipe) 102a ... Communication pipe inlet (other end of water injection water discharge pipe) 103 ... Swirl diode 103a ... First inflow Pipe outlet 103b ... Second inlet pipe outlet 103c ... Spiral diode inner peripheral surface 104 ... First inlet pipe (small flow pipe) 104a ... First inlet pipe inlet (one end of small flow pipe) 105 ... Second inflow pipe (large flow pipe) 105a ... Inlet of second inflow pipe (one end of large flow pipe)

Claims (1)

[Claims] 1. An emergency water injection device for a nuclear reactor, comprising an accumulator water injection tank communicating with a primary reactor cooling system via a communication pipe having a check valve, wherein a swirl is provided at an inlet of the communication pipe in the accumulator water injection tank. An outlet of the diode is provided in a fluid communication relationship, and an outlet of the first inflow pipe having an inlet opening to a lower portion in the same accumulator injection tank is opened in the circumferential direction along the inner peripheral surface of the spiral diode, An outlet of a second inflow pipe having an inlet opening at an upper part in the accumulator injection tank;
The second from the flow from the outlet of the first inflow pipe
An emergency water injection device for a nuclear reactor, characterized in that it is opened in the direction in which the flow from the flow pipe of the reactor collides.