JPS62284293A - 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] 3. Detailed Description of the Invention and Objectives of the Invention] (Field of Industrial Application) The present invention relates to an emergency core cooling system for dealing with abnormal situations such as a loss of coolant accident in a nuclear power plant. .

(Prior Art) Generally, an emergency core cooling system used in a boiling water nuclear power plant has the configuration shown in FIG. A plurality of core cooling water injection pipes 3, 4, 5, 6.7 are connected to each other.

Each core cooling water injection pipe 3.4, 5.6.7 is independent from each other, and each water injection pump 8a, 3b, 8C, 3d
, 8e are injected into the reactor pressure vessel 2.

Each core cooling water injection pipe 3, 4, 5, 6.7 has a normally closed isolation valve 9a, 9b outside the reactor containment vessel 1.

9C, 9 (f, 9ee and check valves 10a, 10b
, 10c.

10(j, 10e are each arranged in series,
Depending on the function of injecting water into the reactor pressure vessel 2, high pressure core spray system piping 7. Divided into low pressure core spray system piping 3° and low pressure water injection system piping 4, 5.6. The suction side piping 11e of the high pressure core spray system pump is connected to both the condensate storage tank 12 and the pressure suppression pool 13. The condensate storage tank 12 is the first water source for the high-pressure spray pump 8e.
The water inside is used, and when this runs out, pressure suppression pool 1
3 water is used.

Also, the suction side piping 11a and ll of each of the low pressure core spray system pump 8a and the low pressure water injection system pumps 8b, 8C, and 8d.
b, IIC, lld are connected to the pressure suppression pool 13. In addition, emergency diesel power generation 1114a,
14b and 14e are provided. Further, heat exchangers 15b and 15a are installed in the discharge side pipes 4 and 5 of the low-pressure injection system pump for removing residual heat.

If a loss of coolant accident occurs in which the water level in the reactor pressure vessel 2 drops for some reason, the water injection pumps 8a to 8e of the emergency core cooling system are activated all at once, and the isolation valves 9a to 9e are activated. When the reactor pressure vessel 2 is opened, cooling water is injected into the reactor pressure vessel 2 to prevent accidents within the nuclear power plant.

At this time, sufficient quality control is performed on each pump and valve so that the normally closed isolation valves 9a to 9e open at the same time and the water injection pumps 8a to 8e are started at the same time, and the reliability is high.

Additionally, a containment vessel spray system is provided to reduce pressure and temperature within the containment vessel in the event of a loss of coolant accident. As shown in FIG. 3, by switching from the low pressure injection system, water in the pressure suppression pool 13 is transferred to the heat exchanger 15a.
and 151), and then sprayed into the containment vessel. That is, the electric control valves 22a and 22
By closing b, the low pressure water injection system pumps 8b and 8C
The water in the pressure suppression pool 13 that has been pressurized is transferred to the heat exchanger 15a.
and 15b, thereby cooling the pool water. This water is sprayed into the dry well 25 from the spray headers 20a, 20b by closing the electric control valves 9b and 9C and opening the electric control valves 23a, 23b, 23c, 23d. At the same time, the control valve 24a
, spray header 21a by opening 24b.
, 21b into the wet well 26. This reduces the pressure and temperature inside the containment vessel and maintains the integrity of the containment vessel. This containment vessel spray system is designed so that even if one system is inoperative, the remaining system can sufficiently reduce the pressure and temperature within the containment vessel in the event of loss of coolant.

(Problems to be Solved by the Invention) However, if the emergency diesel generators 14a, 14b fail due to loss of external power supply, or if the low pressure water injection system pumps Bb, 6c fail, or if the electric control valve 23a , 2'3b, 23c, 2
3d does not open, or if the containment spray system fails due to a combination of these events, there is a risk that the containment vessel 1 will be damaged. In this case, the high-temperature water in the reactor pressure vessel 2 is flowing out into the containment vessel 1, so the water in the pressure suppression pool 13 is at a high temperature. Effective NPSH of spray system pump 8e, low pressure spray system pump 8a, and low pressure water injection system pump 8d
There is a risk that cavitation may occur within the pump. In such a situation, the function of the pumps may not be ensured and the core may not be able to be cooled, and in the worst case, the core may melt.

In view of the above-mentioned circumstances, the present invention provides an emergency core cooling system that effectively cools the reactor core even when the containment vessel spray system does not operate, the containment vessel is damaged, and the water temperature in the pressure suppression pool rises. It is intended for the purpose of

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides an emergency core cooling system for a nuclear reactor that is composed of a high pressure core spray system, a low pressure core spray system, and a low pressure injection system. In the device, a heat exchanger for removing residual heat is installed upstream of the water injection pump of the low pressure injection system, and the outlet piping of the heat exchanger is connected to the suction side piping of the water injection pump of the high pressure core spray system. At least one of the piping and the piping connecting the heat exchange outlet piping and the water injection pump suction side piping of the low-pressure core spray system is installed.

(Function) Therefore, according to the present invention, even if the containment vessel spray system does not operate in the event of a loss of coolant accident and the containment vessel is damaged, the pressure within the containment vessel decreases and the water temperature of the pressure suppression pool increases. A heat exchanger for decay heat removal is installed upstream of the low-pressure water injection system pump to ensure effective NPSH of the low-pressure water injection pump.
Alternatively, if the cause of the containment vessel spray system's non-operation is the low-pressure water injection pump's non-operation, install it in the piping that connects the above heat exchanger outlet piping with the high-pressure spray system pump suction side and the low-pressure spray system pump suction side piping. By opening the electric valve, water cooled by the heat exchanger is supplied to the high-pressure spray system pump and low-pressure spray system pump, ensuring effective NPSH for both pumps and enabling effective cooling of the reactor core. .

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a system diagram of an embodiment of the present invention, and the same parts as those in FIG. 2 already described are given the same reference numerals, and detailed explanation thereof will be omitted. In the same figure,
Heat exchangers 15a and 15b for residual heat removal are each connected to piping 1.
6a, 27a, 16b, 27b connect the suction side pipes 11c and 11 of the low pressure water injection system pumps 8C and 8b.
(11, - installed. Also, heat exchanger outlet piping 2
Pipes 17a and 17b branch from 7a and 27b, and are connected to the suction side piping 11 of the low-pressure spray pump 8a, respectively.
a and the suction side piping 11e of the high-pressure spray system pump 8e. Generally, electric normally closed valves 18a and 18b are installed in the pipes 1γa and 17b, respectively.

Next, the operation of this embodiment will be explained.

According to the emergency core cooling system of this embodiment, if the containment vessel spray system does not operate and the containment vessel is damaged for a reason other than the inoperation of the low-pressure water injection system pumps 8b and 8C, the water temperature in the pressure suppression pool 13 increases, cavitation may occur in the high-pressure spray system pump Be, low-pressure spray system pump 8a, and low-pressure water injection system pump 8d, but after confirming the operation of the low-pressure water injection system pumps 8b and 8C, the electric valves 22a and 22b are By closing, water from the pool 13 cooled by the heat exchangers 15a and 15b is supplied to the low pressure water injection pumps 8C and 8b, thereby cooling the core.

In addition, due to the inoperation of low pressure injection system pumps 8C and 8b,
Even if the containment vessel spray system does not operate and the containment vessel 1 is damaged and the water temperature in the pressure suppression pool 13 rises, after confirming that the low pressure water injection system pumps 8b and 8C are inoperable, the electric valves 22a, 22b and The heat exchanger 15 is closed by closing the electric valves 19a and 19b and opening the electric valves 18a and 18b, and then closing the electric valves 28a and 28b.
Since the pool water cooled by a and 15b is supplied to the high pressure spray system pump 8e and the low pressure spray system pump 8a, cavitation of the pumps can be prevented and the core can be effectively cooled.

[Effects of the Invention] As explained above, according to the present invention, even in a situation where the containment vessel spray system does not operate and the containment vessel is damaged, cavitation does not occur in all water injection pumps. Therefore, since the core is effectively cooled, there is an excellent effect of preventing core melting.

[Brief explanation of drawings]

Fig. 1 is a system diagram of an embodiment of the present invention, Fig. 2 is a system diagram of a conventional emergency core cooling system in a boiling water nuclear power plant, and Fig. 3 is a system diagram of a conventional emergency core cooling system in a boiling water nuclear power plant. FIG. 1 is a system diagram of a conventional containment vessel spray system in a water-type nuclear power plant. 1...Containment vessel 2...Reactor pressure vessel 3...Low pressure spray system piping 4-6...Low pressure injection system piping 7...High pressure spray system piping 8a-8e...Water injection pump 9a- 9e... Isolation valves 10a-10e... Check valves 118-lie... Infusion pump suction side piping 12...
Condensate storage tank 13...Pressure suppression pool 14a, 14b, 14e...Emergency power generation diesel 15a, 15b...Heat exchanger 18a, 16b...Heat exchanger inlet piping 17a,
17b... Heat exchanger outlet branch piping 27a, 27
b...Heat exchanger outlet piping (8733) Agent: Yoshiaki Inomata, patent attorney (and one other person) Figure 3.

Claims (1)

[Claims] In an emergency core cooling system for a nuclear reactor consisting of a high-pressure core spray system, a low-pressure core spray system, and a low-pressure injection system, a heat exchanger for removing residual heat is installed upstream of the water injection pump of the low-pressure injection system, and The least of the piping that connects the outlet piping of the heat exchanger and the water injection pump suction side piping of the high pressure core spray system, or the piping that connects the heat exchange outlet piping and the water injection pump suction side piping of the low pressure core spray system. An emergency core cooling system for a nuclear reactor, characterized in that one side of the pipe is installed.