JP2548838B2 - Core collapse heat removal system for pressurized water reactor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressurized water nuclear reactor, and more particularly to a core collapse heat removal apparatus applicable to emergency core cooling equipment of the nuclear reactor.

[0002]

2. Description of the Related Art FIG. 4 schematically shows a primary cooling system of a typical conventional two-loop pressurized water reactor having two steam generators 2 and two primary coolant pumps 3, respectively.
The primary cooling system equipment includes a reactor vessel 1, a steam generator 2, a primary coolant circulation pump 3, and a primary cooling system loop 6 including primary coolant pipes 5 and 7 connecting these components to form a closed circuit. And a pressurizer 4 and the like. Core in the reactor vessel 1
The primary coolant heated in 10 is conveyed from the reactor vessel 1 through the high temperature side pipe 5 of each loop 6 to the U-shaped heat transfer pipe 8 in the vertically arranged steam generator 2, where the heat transfer pipe 8 It exchanges heat with the secondary coolant flowing around it. The primary coolant thus cooled by the steam generator 2 is provided with a head of water by the primary coolant circulation pump 3, and is returned to the reactor vessel 1 again through the low temperature side pipe 7.

However, an accident in which the primary cooling system pressure is drastically reduced and the emergency core cooling equipment operates,
For example, at the time of a primary coolant loss accident due to a breakage accident at a location such as the piping of the primary cooling system as shown by reference numeral 9, the primary coolant flows out of the system from the breakage location 9 of the core, and
Is exposed once. In this case, the reactor is designed to be shut down immediately after the accident, but since nuclear fuel exists in the core, core decay heat is generated even after the reactor is shut down. If the core is exposed for a long period of time and the core is not cooled sufficiently, it is assumed that this decay heat may lead to the worst situation such as core melting. Therefore, in the event of a primary coolant loss accident, emergency core cooling water is injected into the primary cooling system, and the injected cooling water is efficiently injected into the core,
Moreover, since it is important to supply and accumulate it at an early stage, emergency core cooling equipment is provided.

The conventional emergency core cooling equipment is similar to the accumulator injection system equipment consisting of the accumulator injection tank 12 and the high pressure injection system equipment including the high pressure injection pump 19 which requires an external drive source such as an AC power source. In addition, the low-pressure injection system equipment including the low-pressure injection pump 18 that requires an external drive source such as an AC power source. Although only one pressure-accumulation injection tank 12 is shown in FIG. 4, one pressure-accumulation injection tank is usually used for each loop of the primary cooling system, and the pressure-accumulation injection tank 12 is always used. The boric acid water 13 is pressurized and maintained by the nitrogen gas 11, and in the unlikely event of a coolant loss accident, the check valve 15 automatically opens due to the depressurization of the primary cooling system, and the primary Boric acid water 13 is injected into the low temperature side pipe 7 of the cooling system.
In addition, the low-pressure injection pump 18 and the high-pressure injection pump 19 use a fuel replacement water tank 20 that stores boric acid water as a water source to fill the reactor cavities when refueling, and reduce the pressure of the primary cooling system. High-pressure injection pump 1 under the control of a controller connected to a means (not shown) for detecting
It is operated sequentially from 9 and is designed to inject water into the primary cooling system.

As the low-pressure injection pump 18, a residual heat removal pump used when shutting down the reactor in a cold state is used. Further, the low-pressure injection pump 18 recycles the water accumulated in the bottom sump (not shown) of the containment vessel 16 after the water in the refueling water tank 20 is used up,
Also connected to the bottom sump, the low pressure injection system requires a heat exchanger (not shown) to cool the recirculated water. In addition, the refueling water tank 20 contains
A containment spray system is connected to reduce the leakage of radioactive material from 16. The containment vessel spray system includes a containment vessel spray pump 21, which requires an external drive source such as an AC power source, a heat exchanger 22, and a containment vessel spray 23.
And The secondary side of both the heat exchanger 22 and the above-mentioned heat exchanger of the low-pressure injection system is connected to the reactor auxiliary cooling water system (not shown). It is designed to radiate heat.

[0006]

As described above, in the conventional emergency core cooling system for a pressurized water reactor, a large amount of emergency cooling water is urgently supplied to the low temperature side pipe 7 of the primary cooling system loop immediately after the occurrence of the accident. In order to inject and accumulate in the reactor vessel 1,
Even if there is no problem in using the accumulator injection facility, that is, the above-mentioned accumulator water injection tank 12, in order to replenish the evaporation and emission of the coolant due to the core decay heat over a long period thereafter, an AC power source or the like is used. It relies on a dynamic system-based safety system (referred to as an active safety system) such as the low-pressure injection pump 18 and the high-pressure injection pump 19 which require an external drive source. The active safety system is excellent in terms of accident convergence and prevention of expansion, but since it includes equipment such as a pump that requires an external drive source such as an AC power source, its operation is complicated and operation is difficult. Is not reliable, and there is no problem in safety.

Accordingly, it is an object of the present invention to minimize the use of dynamic equipment to reliable equipment such as valves,
An object of the present invention is to provide an accident static core decay heat removal device capable of removing decay heat substantially statically.

[0008]

In order to achieve this object, according to the invention described in claim 1, there is provided a reactor vessel having a lid at the top and an inlet nozzle and an outlet nozzle for the primary coolant. A core disposed in the reactor vessel, and a water chamber partitioned into an inlet chamber and an outlet chamber, the inlet chamber and the outlet chamber of the water chamber having an inlet nozzle and an outlet nozzle of a primary coolant, respectively. A steam generator having a plurality of U-shaped pipes communicating with the inlet chamber and the outlet chamber at both ends, and is connected to the steam generator, and is provided around the U-shaped pipe. A secondary cooling system having an inlet pipe and an outlet pipe for circulating and supplying a secondary coolant, a coolant circulation pump, a hot leg pipe connecting an outlet nozzle of the reactor vessel and an inlet nozzle of the steam generator. And an outlet nozzle of the steam generator and the A core collapse heat removal device of a pressurized water reactor having a cold leg pipe connecting an inlet nozzle of a sub-reactor container via the coolant circulation pump, a first decompression means connected to a lid of the reactor container. A first water source disposed above the secondary cooling system and communicating with the secondary cooling system via a pipe having a valve; and a second pressure reducing means connected to the secondary cooling system, A hot water pipe and a cold leg pipe are provided above the pipe, and a pipe having a valve is connected to the hot leg pipe and the cold leg pipe. The pipe has a second water source communicating with the inside of the reactor vessel. The steam generator has its inlet nozzle disposed below the outlet nozzle of the reactor vessel, and the second water source is the water discharged when the valve is opened in the pipe connected to the second water source. , At least enough water to submerge the hot leg piping and cold leg piping.

In order to achieve the above object, according to the invention described in claim 2, a reactor vessel having a lid at the top and an inlet nozzle and an outlet nozzle for the primary coolant, and A reactor core disposed in a reactor vessel, and a water chamber partitioned into an inlet chamber and an outlet chamber, the inlet chamber and the outlet chamber of the water chamber having an inlet nozzle and an outlet nozzle of a primary coolant, respectively. A steam generator in which a plurality of U-shaped pipes communicate with the inlet chamber and the outlet chamber at both ends, and the steam generator is connected to the steam generator and a secondary coolant is circulated around the U-shaped pipe. Secondary cooling system having an inlet pipe and an outlet pipe for cooling, a coolant circulation pump, a hot leg pipe connecting the outlet nozzle of the reactor vessel and the inlet nozzle of the steam generator, and the outlet of the steam generator Inserting the nozzle and the reactor vessel A core decay heat removal device of a pressurized water reactor having a cold leg pipe connecting a nozzle via the coolant circulation pump is disposed above the secondary cooling system, and is connected via a pipe having a valve. A first water source communicating with a secondary cooling system, a decompression unit connected to the secondary cooling system, a hot pipe and a cold leg pipe are provided above the pipe, and a pipe having a valve is connected, And a second water source communicating with the reactor vessel via a pipe. The steam generator has a vent pipe provided in an inlet chamber of the water chamber, which is arranged horizontally, and the second water source is the valve of the valve in a pipe connected to the second water source. The water discharged at the time of opening the valve has a water capacity sufficient to submerge at least the hottleg pipe and the cold leg pipe.

[0010]

[Operation] During normal reactor operation, the primary coolant that entered the reactor vessel from the cold leg piping connected to the inlet nozzle of the reactor vessel is heated in the reactor core, and is discharged from the outlet vessel of the reactor vessel. It goes out, passes through the hot leg pipe, goes from the inlet chamber of the water chamber of the steam generator to the outlet chamber through the inside of the U-shaped heat transfer tube, and is pressurized by the circulation pump from here and fed again into the reactor vessel. It The primary coolant is cooled by exchanging heat with the secondary coolant flowing around the heat transfer pipe as it passes through the inside of the heat transfer tube, while the secondary coolant is heated to become steam, which drives the steam turbine for power generation. Used for.

For example, when a coolant loss accident such as a pipe breakage accident occurs in the primary cooling system, in order to prevent the worst virtual accident such as core melting due to decay heat, the core decay heat removal apparatus of the present invention is used. Is activated. That is, when the pressure of the primary cooling system is decreased due to the loss of the coolant, in the case of the first embodiment,
The first depressurizing means is operated to release the non-condensable gas such as hydrogen gas and oxygen gas generated in the reactor core into the containment vessel from the valve of the pipe connected to the lid of the reactor vessel. The valve provided in the pipe connected to the water source is opened, and the second
Water from a water source is injected into the reactor vessel. The second water source is disposed above the hot leg pipe and the cold leg pipe, and has a sufficiently large capacity. Therefore, when the valve is opened, water is discharged due to the head difference, and the hot leg pipe and the cold leg pipe are cooled. Submerge the leg piping.

Therefore, the non-condensable gas does not flow into the primary cooling system from the breakage point of the primary cooling system, and in the invention described in claim 1, the inlet nozzle of the steam generator is of the reactor vessel. Since it is located below the outlet nozzle, a loop seal is formed between the inlet nozzle and the outlet nozzle. Further, in the invention according to claim 2, the steam generator is arranged horizontally. Since the vent chamber having the valve is provided in the water chamber, the non-condensable gas does not interfere with the natural circulation of the primary coolant through the heat transfer tube. Using the natural circulation of the primary coolant, the second pressure reducing means connected to the secondary cooling system is operated to remove decay heat by exchanging heat with the secondary coolant in the steam generator. While depressurizing the secondary cooling system, open the valve of the first water source arranged above the secondary cooling system, and inject the water of the first water source into the secondary cooling system due to the head difference, Heat is exchanged with the primary coolant flowing through the heat transfer tube by natural circulation,
Thus, the decay heat of the core is removed by using the steam generator.

[0013]

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or corresponding parts. Referring to the drawings, FIGS. 1 and 2 show an emergency core cooling facility according to a first embodiment of the present invention applied to a pressurized water nuclear power plant. In FIG. 1, the pressurized water nuclear power plant generally has a primary cooling system of 2 to 4 loops according to its output scale, but in the example shown in the figure, the steam generator 2
And two loops each having two primary coolant pumps 3 (only one loop is shown) schematically shows a primary cooling system of a nuclear power plant. The primary cooling system equipment includes a reactor vessel 1 and steam generation. Vessel 2, primary coolant circulation pump 3, hot leg piping 5 that connects these to form a closed circuit,
A primary cooling system loop 6 including a cold leg pipe 7 and a pressurizer 4 are included.

The primary coolant heated in the core 10 in the reactor vessel 1 is a steam generator from the outlet nozzle 1a of the reactor vessel 1 through the hot leg piping 5 of each loop 6 and the inlet nozzle 2a. Enter the water chamber 2b of No.2, and from here, the U-shaped heat transfer tube
It is conveyed to the (U-shaped tube) 8 and exchanges heat with the secondary coolant flowing around the heat transfer tube 8. The primary coolant thus cooled by the steam generator 2 exits the steam generator 2 from the outlet nozzle 2c, is given a head of water by the primary coolant circulation pump 3, and passes through the cold leg pipe 7 to the inlet nozzle 1b. Is returned to the reactor vessel 1 again. The water chamber 2b of the steam generator 2 is
The partition plate 2d divides the hot leg side portion (inlet chamber) having the inlet nozzle 2a and the cold leg side portion (outlet chamber) having the outlet nozzle 2c. The U-shaped heat transfer tube 8 described above is a tube. One end communicates with the hot leg side portion and the other end communicates with the cold leg side portion via the plate 2e.
Further, as shown best in FIG. 2, the vertically installed steam generator 2 has an inlet nozzle 2a whose outlet nozzle 1a is in the reactor vessel 1.
Since it is arranged so as to be located higher, the outlet nozzle 1a of the reactor vessel 1 and the inlet nozzle 2a of the steam generator 2
A loop seal 17 that prevents non-condensable gases such as hydrogen gas and dissolved gas from flowing into the steam generator 2 is formed in the piping portion between them. The purpose of this loop seal 17 is to prevent non-condensable gas from entering the steam generator 2 as described above.

A water supply pipe (inlet pipe) 28 and a steam pipe (outlet pipe) 29 constituting a secondary cooling system are connected to the steam generator 2, and the secondary side of the steam generator 2 is connected from the water supply pipe 28. The feed water flowing into the inside is heated by exchanging heat with the primary coolant through the heat transfer tube 8, becomes steam, and leaves the steam generator 2 from the steam pipe 29,
It is sent to a steam turbine (not shown). This water pipe 28
The steam pipe 29 is connected to a condensate tank (first water source) 30 via a pipe 32 having a valve 31. ) 3
A pipe 36 having 5 is connected. The condensate tank 30 is arranged at least above the water supply pipe 28. The pressurizer 4 is connected to a pipe 25 having a plurality of (two in the embodiment) relief valves 24 each having a large capacity of 8 inches in a reactor having an output of 300,000 KWe, for example. Pipe having a vent valve (first pressure reducing means) 26 at the top of the lid 1c.
27 is connected. An emergency storage tank (second water source) 50 is installed at least above the hot leg and cold leg pipes 5 and 7 of the primary cooling system loop 6. The storage tank 50 is provided with a valve 33 for directly injecting stored water into the containment vessel 16 and a valve 34 for injecting stored water into the reactor vessel 1. In the figure, valves 26, 31, 3
Although only one of each of 4, 33 and 35 is shown, a plurality of them can be provided in parallel to form a redundant system.

In the emergency core cooling equipment having the above-described structure, when an unillustrated control device receives a first signal of the pressure drop of the primary cooling system from a well-known pressure detecting means (not shown) at the time of an accident, Under the control of the control device, the vent valve 26 provided in the pipe 27 connected to the lid body 1c of the reactor vessel 1 opens, and in the reactor core 10 that interferes with the natural circulation of the coolant as described later. The generated non-condensable gas such as hydrogen gas, oxygen gas, nitrogen gas and the like are discharged from the reactor vessel 1 into the containment vessel 16. Also, by the signal of the pressure drop,
The relief valve 24 of the pressurizer 4 is also opened to early reduce the pressure of the primary cooling system. As a result, when the pressure of the primary cooling system further decreases and the second signal is transmitted, the valves 33 and 34 of the emergency stored water tank 50 are opened, and the stored water is stored in the containment vessel 16 and the core 10 due to the head difference. And inject. By pouring water by opening the valves 33 and 34,
At least the hot leg pipe 5 and the cold leg pipe 7 of the primary cooling system loop 6 are submerged. On the other hand, the relief valve 35 connected to the secondary cooling system of the steam generator 2 has the first
Signal or another signal to open the valve to depressurize the secondary side of the steam generator to near atmospheric pressure, then open valve 31 of the condensate tank 30 to move the water in the condensate tank 30 to the head difference. To inject water to the secondary side of the steam generator.

In this state, the containment vessel 16 is filled with water to a level exceeding at least the hot leg pipe 5 and the cold leg pipe 7 of the primary cooling system loop 6 as described above, and the coolant is lost. The break point 9 that caused the accident was also flooded. Therefore, the decay heat generated in the core 10 is transported to the steam generator 2 by natural circulation of the water in the core 10, the water in the containment vessel 16 and the water in the sound primary cooling system loop 6, and the steam generator 2 In, the heat is exchanged with the secondary side water injected from the condensate tank 30 and removed. During such natural circulation, since the breakage point 9 is submerged, the non-condensable gas does not enter from the break point 9 and the non-condensable gas enters the coolant of the sound primary cooling system loop 6. , The non-condensable gas advances to the heat transfer pipe 8 of the steam generator 2 at the loop seal 17 because the loop seal 17 is provided on the inlet nozzle 2a side of the steam generator 2. Will not be reached.

Next, with reference to FIG. 3, a second embodiment of the core collapse heat removal apparatus according to the present invention will be described with respect to differences from the first embodiment. In FIG. 3, the outer side of the storage container 16 is covered by an outer shield 37, which is preferably a steel plate structure and is arranged on the outer side with a space therebetween. Also, the storage container
An annular gravity drop tank (second water source) 38 is defined inside the 16 by a concrete wall 39, and the gravity drop tank 38 is filled with water. In the embodiment, this gravity drop tank 38 extends up to about 10 m above the reactor core 10 so that water can be injected by a water head difference as described later.
It also plays the role of the refueling water tank 20 described in connection with. In the first embodiment, the pipe 25 having the relief valve 24 is open to the space inside the containment vessel 16, but in the second embodiment, the pipe 25 having the relief valve 24 penetrates the concrete wall 39 and falls by gravity. It extends into the tank 38 and opens there. Further, in the embodiment of FIG. 1, since the steam generator 2 is of the vertical type, in order to prevent the non-condensable gas from reaching the heat transfer tube 8, the outlet nozzle 1a of the reactor vessel 1 and the steam generator are prevented. Two
The loop seal 17 is provided between the inlet nozzle 2a and the inlet nozzle 2a, and the vent valve 26 is provided in the lid 1c of the reactor vessel 1.
In the embodiment, since the steam generator 40 is placed horizontally, instead of the loop seal 17, a pipe (vent pipe) 42 having a degassing valve 41 is connected to the inlet chamber on the hot leg side of the water chamber 40a. There is. In addition to the valve 31, the pipe 32 of the condensate tank 30 is provided with a turbine-driven auxiliary water supply pump 43 and a motor-driven replenishment water supply pump 44 for backup.

Next, the operation of the emergency core cooling equipment of the second embodiment at the time of the primary coolant loss accident will be described below. At the beginning of the accident, the pressure in the primary cooling system was high to medium pressure,
In order to inject water for core cooling at this time, it is preferable to rapidly depressurize the primary cooling system and use the accumulator injection tank 12. Therefore, when the pressure detection means detects the pressure drop of the primary cooling system in the early stage of the accident and the first signal is output from the control device, the primary cooling system is promptly operated by the operating pressure of the accumulator injection tank (second water source) 12 (implementation). In the example, the pressure is reduced to 50 Kg / cm ² or less,
The relief valve 24 of the pressurizer 4 is opened to flush the vapor into the gravity drop tank 38 rather than into the space within the containment vessel 16. As a result, the primary cooling system falls below the operating pressure of the pressure-accumulation injection tank 12, and the pressure-accumulated water is discharged into the core 10 to cool the core 10. During the middle of the accident, the pressure in the primary cooling system was medium to low pressure.At this time, a considerable amount of water was required to inject water for core cooling, and the accumulator injection tank was used. Uses a large-capacity gravity drop tank 38 because the equipment becomes too large. Therefore, when the pressure detecting means detects a further lower pressure and the control device transmits the second signal, the valve 46 provided in the pipe 45 communicating with the cold leg pipe 7 and the gravity drop tank 38 is opened, and the gravity force is reduced. Drop tank
The water in 38 is poured into the core 10 by the water head difference, and the core 10 is cooled. At this stage, the water contained in the pressure accumulating injection tank 12 and the gravity falling tank 38 causes the primary cooling system loop 6
At least the hot leg piping 5 and the cold leg piping 7 are submerged as shown. In this way, in the event of a loss of coolant, emergency core cooling water can be injected into the primary cooling system, and the injected cooling water can be efficiently and early supplied and accumulated in the core.

On the other hand, thereafter, during long-term cooling in which the pressure in the primary cooling system and the pressure in the containment vessel are substantially equal to each other, the water that submerges the reactor core is naturally circulated to the steam generator 40. It is allowed to flow to remove the decay heat of the core 10. For this purpose, the relief valve 35 is opened to reduce the pressure on the secondary side of the steam generator, then the valve 31 of the pipe 32 connected to the condensate tank 30 is opened, and the secondary side of the condensate tank 30 due to a water head difference Supply water to the water supply pipe 28. In this state, as described above, the containment vessel 16 is filled with water up to a level at least exceeding the hot leg pipe 5 and the cold leg pipe 7 of the primary cooling system loop 6, causing the loss of coolant accident. The broken point 9 which has become is also submerged. Therefore, the decay heat generated in the core 10 is sent to the steam generator 40 by natural circulation of the water in the core 10, the water in the containment vessel 16 and the sound water in the healthy primary cooling system loop 6 as in the first embodiment. In the steam generator 40, heat is exchanged with the water on the secondary side injected from the condensate tank 30 through the heat transfer tube 8, the water is boiled, and is discharged to the atmosphere through the relief valve 35. Are removed by During such natural circulation, since the breakage point 9 is submerged, the non-condensable gas does not enter from the break point 9 and the non-condensable gas enters the coolant of the sound primary cooling system loop 6. However, since the vent valve 41 of the pipe 42 provided on the hot leg side of the water chamber 40a of the steam generator 40 is open, this non-condensable gas is discharged into the containment vessel without accumulating. It does not interfere with the natural circulation.

[0021]

As described above, according to the present invention, in order to prevent the non-condensable gas generated in the core in the accident of loss of coolant from interfering with the natural circulation of coolant, the space between the reactor vessel and the steam generator is reduced. Since the gas accumulation prevention means is installed in the system, the steam generator can be used to naturally circulate the coolant in the primary cooling system loop, and a low-pressure injection pump and high-pressure injection that requires an external drive source such as an AC power source are required. Since there is no need to rely on a conventional safety system (called an active safety system), which mainly consists of dynamic equipment such as a pump, the operation is simple and the safety system is highly reliable. In particular, since the steam generator is a commonly used facility, no additional facility is required if it is used, which simplifies the facility and improves economic efficiency. Since it is designed for core heat removal, it has an excellent cooling function.

Further, in a preferred embodiment, the pipe having a relief valve and connected to the pressurizer at one end is opened at the other end into the gravity drop tank, so that in the event of an accident, a dynamic device is used. The inside of the storage container can be depressurized without depending on the conventional storage container spray system including a certain storage container spray pump, which greatly contributes to the improvement of the reliability of the safety system.

[Brief description of drawings]

FIG. 1 is a schematic view of a pressurized water reactor including a core collapse heat removal device according to a first embodiment of the present invention.

FIG. 2 is an enlarged partial sectional view of a loop seal provided in the primary cooling system of the pressurized water reactor of FIG.

FIG. 3 is a schematic diagram of a pressurized water reactor including a core collapse heat removal device according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram of a pressurized water reactor including a conventional core collapse heat removal device.

[Explanation of symbols]

 1 Reactor vessel 1a Outlet nozzle 1b Inlet nozzle 1c Lid 2 Steam generator 2a Inlet nozzle 2b Water chamber 2c Outlet nozzle 3 Coolant circulation pump 5 Hot leg pipe 7 Cold leg pipe 8 Heat transfer pipe (U-shaped pipe) 10 Core 12 Accumulation tank (second water source) 17 Loop seal 26 Relief valve (first pressure reducing means) 28 Water supply pipe (inlet pipe) 29 Steam pipe (outlet pipe) 30 Condensate tank (first water source) 31 Pipe 32 valve 32 No. 1 Pipe for connecting the water source to the secondary cooling system 35 Relief valve (second pressure reducing means) 38 Gravity drop tank (second water source) 40 Steam generator 40a Water chamber 42 Pipe (vent pipe) 45 Second water source for reactor vessel Piping to communicate with 46 46 Piping 45 valve 50 Emergency storage tank (second water source)

Claims (2)

(57) [Claims] 1. A reactor vessel having a lid at the top and having a primary coolant inlet nozzle and an outlet nozzle, a reactor core disposed in the reactor vessel, and an inlet chamber and an outlet chamber. A water chamber, and the inlet chamber and the outlet chamber of the water chamber are arranged vertically with an inlet nozzle and an outlet nozzle of the primary coolant, respectively, and a plurality of U are provided in the inlet chamber and the outlet chamber.
A secondary having a steam generator having pipes communicating at both ends, and an inlet pipe and an outlet pipe connected to the steam generator and circulatingly supplying a secondary coolant around the U-shaped pipe. A cooling system, a coolant circulation pump, a hot leg pipe connecting the outlet nozzle of the reactor vessel and the inlet nozzle of the steam generator, the outlet nozzle of the steam generator and the inlet nozzle of the reactor vessel are cooled. In a core decay heat removal device for a pressurized water nuclear reactor having a cold leg pipe connected via a material circulation pump, a first decompression means connected to a lid of the reactor vessel and a secondary cooling system A first water source disposed above and communicating with the secondary cooling system via a pipe having a valve; a second pressure reducing means connected to the secondary cooling system; and the hot leg pipe and the cold leg pipe. Is also placed above And a second water source that is connected to a pipe having a valve and communicates with the inside of the reactor vessel by the pipe, and the steam generator has the inlet nozzle located below the outlet nozzle of the reactor vessel. The second water source has a sufficient water capacity to submerge at least the hot leg pipe and the cold leg pipe by the water released when the valve is opened in the pipe connected to the second water source. A core collapse heat removal device for a pressurized water reactor characterized by the above. 2. A reactor vessel having a lid at the top and having an inlet nozzle and an outlet nozzle for the primary coolant, a reactor core arranged in the reactor vessel, and an inlet chamber and an outlet chamber. A water chamber, the inlet chamber and the outlet chamber of the water chamber each have an inlet nozzle and an outlet nozzle of a primary coolant, and a plurality of U-shaped pipes communicate with the inlet chamber and the outlet chamber at both ends. A steam generator, a secondary cooling system connected to the steam generator, having an inlet pipe and an outlet pipe for circulating and supplying a secondary coolant around the U-shaped pipe, and a coolant circulation pump. A hot leg pipe connecting an outlet nozzle of the reactor vessel and an inlet nozzle of the steam generator;
In the core collapse heat removal apparatus of a pressurized water reactor having an outlet nozzle of the steam generator and a cold leg pipe connecting the inlet nozzle of the reactor vessel through the coolant circulation pump, from the secondary cooling system. A first water source which is disposed above and communicates with the secondary cooling system via a pipe having a valve, a decompression means connected to the secondary cooling system, and the hot leg pipe and the cold leg pipe. And a second water source connected to a pipe having a valve, which is arranged above and connected to the reactor vessel via the pipe, the steam generator is arranged horizontally, and the water A vent pipe provided in an inlet chamber of the chamber, wherein the second water source is at least the hot leg pipe and the cold pipe due to water released when the valve in the pipe connected to the second water source is opened. Leg piping A pressurized water reactor core decay heat removal device, characterized in that it has a water capacity sufficient to flooding.