JPS60247196A - Emergency core cooling device for boiling-water type 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 a boiling water nuclear reactor (hereinafter referred to as BWR),
For example, the present invention relates to an emergency core cooling system for a boiling water reactor that cools the core in the event of a pipe rupture accident.

[Technical Background of the Invention] A boiling water reactor generally has the following configuration. That is, a reactor containment vessel is installed within the reactor building, and a reactor pressure vessel is installed within the reactor containment vessel, supported by a pedestal. This reactor pressure vessel houses a reactor core consisting of a plurality of fuel assemblies, control rods, etc., and cooling water. The above-mentioned cooling water flows from the bottom to the top of the core, and as it does so, its temperature rises due to the heat of reaction in the core, resulting in a two-layer flow of water and steam. The cooling water, now in a two-layered flow state, flows into the steam-water separator above the core and is separated into water and steam. The separated steam flows into a steam dryer installed above the steam separator and is dried into dry steam, which is transferred to the turbine system via the main steam pipe connected to the reactor pressure vessel, There, it is used for power generation.

In a boiling water reactor with the above configuration, various types of piping rupture accidents are expected. For example, if the recirculation piping that makes up the recirculation system ruptures, a cooling water loss accident may occur in which cooling water flows out from the rupture point. Occur.

If such a loss of cooling water accident occurs, it is expected that the water level in the reactor pressure vessel will gradually drop, exposing the reactor core. If the reactor core remains exposed for a long time, the temperature of the fuel installed in the reactor core may rise, which may impair the integrity of the reactor core. On the other hand, cooling water flows out from the fractured opening of the fractured recirculation pipe, and as a result, the temperature and pressure inside the reactor containment vessel rise, and there is a concern that this may lead to a secondary disaster. Therefore, in order to cool the reactor core in the event of such a loss of cooling water accident,
An emergency core cooling system is installed.

A conventional emergency core cooling system will be described below with reference to FIG. FIG. 5 is a system diagram showing a schematic configuration of a conventional emergency core cooling system. Reference numeral 1 in the figure indicates a reactor containment vessel, and a reactor pressure vessel 2 is installed within this reactor containment vessel 1. Cooling water 3 and a reactor core 4 are housed within this reactor pressure vessel 2 . The reactor core 4 is
It is composed of a plurality of fuel assemblies, control rods, etc. (not shown). Furthermore, a water supply pipe 5 and a main steam pipe 7 are connected to the inside of the reactor pressure vessel 2 . As described above, dry steam generated within the reactor pressure vessel 2 is supplied to a turbine system (not shown) via this main steam pipe 7. Note that main steam isolation valves 8 and 9 are inserted into the main steam pipe 7. Further, a main steam relief pipe 10 is branched and connected to the main steam pipe, and a main steam relief valve 11 is inserted into the main steam relief pipe 10. In the figure, numerals 12, 13 and 14 indicate valves.

The emergency core cooling system is composed of three sections: Section 1, Section 8, and Section C (the sections are indicated by broken lines in the figure), and the sections will be explained in order below.

The first category is the low-pressure core spray system L that supplies water to the reactor core 4 to spray cool it when the reactor pressure is low.
1, and a first low-pressure water injection system (2) for submerging and cooling the core 4. The low-pressure core spray system (2) includes a low-pressure core spray pipe 24 installed from the suppression pool 23 to the reactor pressure vessel 2, and a low-pressure core spray pipe 24 installed inside the reactor pressure vessel 2 connected to the tip of the low-pressure core spray pipe 24. Spray nozzle 25 and 1. It is composed of a low-pressure core spray pump 26 inserted in the low-pressure spray pipe 24, and cools the core 4 by spraying the cooling water in the suppression boule 23 onto the core 4. Also, the first
The low pressure water injection system IL is.

A low-pressure water injection pipe 27 arranged from the suppression pool 23 to the reactor pressure vessel 2, and this low-pressure water injection pipe 2
7 and a low-pressure water injection pump 28 inserted into the suppression pool 7, the cooling water in the suppression pool 23 is supplied into the reactor pressure vessel 2 to cool the reactor core 4 by submersion. The low pressure core spray pump 26 and low pressure water injection pump 28 are
Both are powered by the station power source 1!29, and are connected to an emergency diesel generator 30 so that they can be driven even if the station power source 29 is lost.

A residual heat removal system heat exchanger 31 is connected to the low pressure water injection pipe 27.
is connected via a bypass pipe 32, and a reactor auxiliary equipment cooler 33 is connected to this residual heat removal system heat exchanger 31. That is, the cooling water from the suppression boule 23 is not directly supplied into the reactor pressure vessel 2, but is cooled and supplied via the residual heat removal system heat exchanger 31. The supplied cooling water flows into the reactor containment vessel 1 through, for example, a break in the piping, and circulates through the suppression boule 23. This cools the reactor containment vessel 1. Note that 33° and 34.35 in the figure are valves inserted in the low-pressure core spray pipe 24, and 36.
Reference numerals 37 and 38 indicate valves inserted in the low-pressure water injection pipe 27, and reference numerals 39 and 40 indicate valves 8 inserted in the bypass pipe 32.゛Next, the eight categories will be explained. Section 8 has a second low-pressure water injection system 41, and the upper part of this second low-pressure water injection system is connected to two low-pressure water injection system piping 42 arranged from the suppression pool 23 to the reactor pressure vessel 2. 4
3, and low-pressure water injection pumps 44 and 45 inserted into these low-pressure water injection system pipes 42 and 43, respectively. When an accident occurs, the low-pressure water injection pumps 44 and 45 are driven to supply cooling water in the suppression pool 23 into the reactor pressure vessel 2, thereby cooling the reactor core 4 by submersion. A residual heat removal system heat exchanger 46 is connected to the low pressure water injection system piping 42 via a bypass piping 47, and a reactor auxiliary equipment cooler 48 is connected to this residual heat removal system heat exchanger 46. There is. That is, similar to the low pressure water injection system 22 in the above section,
The cooling water in the suppression pool 23 is cooled through the residual heat removal system heat exchanger 47 and supplied into the reactor pressure vessel 2.

The supplied cooling water flows into the reactor containment vessel 1 from, for example, a break in the pipe and circulates through the suppression boule 23 . This cools the reactor containment vessel 1. The two low-pressure water injection pumps 44 and 45 are both connected to the in-house type 8!29, and are configured so that they can be driven even if the in-house power source 29 is lost.
Connected to emergency diesel power generator 1lI50. In the figure, numerals 51, 52, and 53 indicate valves inserted in the low-pressure water injection pipe 42, numerals 54, 55, and 56 indicate valves inserted in the low-pressure water injection pipe 43, and numerals 57 and 58 indicate valves inserted in the low-pressure water injection pipe 43. A valve inserted into bypass piping 47 is shown.

Next, the configuration of section C will be explained. This C section has a high-pressure core spray system 61, which includes a high-pressure core spray pipe 63 disposed from the suppression boul 23 or condensate storage tank 62 to the reactor pressure vessel 2, A spray nozzle 64 installed in the reactor pressure vessel 2 and connected to the tip of the high pressure core spray pipe 63, and a high pressure core spray pump 65 inserted into the high pressure spray pipe 63. It is made up of spikes. Then, the cooling water in the suppression boule 2'3 or the condensate storage tank 62 is transferred to the spray nozzle 6.
4 to the reactor core 4 to cool the reactor core 4.

The high-pressure core spray pump 55 is connected to the in-station power source 29 and also to the emergency diesel power generation 1167. It is configured so that it can be driven even if the main unit 29 is lost. Reference numerals 68, 69, 70 and 71 in the figure indicate valves inserted in the high pressure core spray pipe 63.

In this way, emergency core cooling systems fall into three categories A.

It is composed of B and C, and even if a failure occurs in either section, the core 4 can be reliably cooled by the other sections.

[Problems in the background art] According to the above configuration, the sections F and 8 have both the function of cooling the reactor core 4 and the function of cooling the reactor containment vessel 1, but the section C has the function of cooling the reactor core 4 and the reactor containment vessel 1. 4
Since it consists only of the high-pressure core spray system 11 that cools the reactor core 4, it is impossible to cool the reactor containment vessel 1 even though it is possible to cool the reactor core 4. Therefore, if the function of cooling the reactor containment vessels 1 in the sections 1 and 8 is lost (which almost never happens in reality), the problem is that the temperature rise inside the reactor containment vessel 1 cannot be suppressed. Therefore, it was required that all of Section H, Section B, and Section C be equipped with a function to cool the reactor containment vessel 1. Providing an equal cooling function to the three sections is also required from the following points.

In other words, it has been confirmed that the current BWR equipment has a large safety margin, especially in the emergency core cooling system. Therefore, it is required to reduce the number of pumps, etc. in the emergency core cooling system. In this case, as mentioned above, in the case of an emergency core cooling system, the equipment must have redundancy and versatility, and it is necessary to reduce the number of pumps without losing such redundancy and versatility. be. In other words, all of the above-mentioned sections B, B and C are equally equipped with cooling functions, thereby maintaining the above-mentioned multiplicity and versatility,
On top of that, it is necessary to reduce the number of pumps, etc.

[Purpose of the invention]

The present invention has been made based on the above points, and its purpose is to provide a function for cooling the reactor containment vessel in all sections, so that both the reactor core and the reactor containment vessel can be cooled in the event of an accident. An object of the present invention is to provide an emergency core cooling system for a boiling water reactor, which enables reliable cooling and simplifies equipment.

[Summary of the invention]

That is, the emergency cooling system for a boiling water type nuclear reactor according to the present invention is a boiling water type nuclear reactor equipped with a reactor containment vessel and a reactor pressure vessel installed in the reactor containment vessel and containing a reactor core and coolant. In a nuclear reactor, a first low-pressure water injection system having a heat exchange mechanism and supplying coolant into the reactor pressure vessel in an emergency to cool the reactor core by flooding, and a first low pressure water injection system having a heat exchange mechanism to supply coolant in an emergency. a second low-pressure water injection system that supplies water into the reactor pressure vessel to submerge the reactor core; a high-pressure core spray system that sprays coolant into the reactor core in an emergency to drown the reactor; and the high-pressure core spray system. The reactor containment vessel spray mechanism is provided in the reactor containment vessel and sprays coolant into the reactor containment vessel.

[Embodiments of the invention]

A first embodiment of the present invention will be described below with reference to FIG. Note that parts that are the same as those in the prior art are denoted by the same reference numerals, and their explanations will be omitted. FIG. 1 is a system diagram showing the configuration of an emergency core cooling system according to this embodiment. The high-pressure core spray piping 63 of section C is connected to the reactor containment vessel spray mechanism 1.
01 is connected. This reactor containment vessel spray mechanism 101 includes a reactor containment vessel spray pipe 102 that is branch-connected to the high-pressure core spray pipe 63, and a reactor containment vessel spray pipe 102 within the reactor containment vessel 1.
Spray mechanism connected to the tip of.

103, and is configured to cool the inside of the reactor containment vessel 1 by the reactor containment vessel spray mechanism 101 having such a configuration. Further, a residual heat removal system heat exchanger 105 is connected to the high pressure core spray pipe 53 between the branch connection position of the reactor containment vessel spray mechanism LL and the high pressure core spray pump 55 via a bypass pipe 104. A reactor auxiliary equipment cooler 106 is connected to this residual heat removal system heat exchanger 105. That is, when spraying cooling water into the reactor containment vessel 1, the cooling water from the suppression pool 23 or the condensate storage tank 52 is cooled by the residual heat removal system heat exchanger 105 and then sprayed. In the figure, reference numeral 107 indicates a valve inserted in the reactor containment vessel spray pipe 102, and reference numerals 108 and 109 indicate valves inserted in the bypass pipe 104.

As described above, according to the first embodiment, even if a situation occurs in which the 100-100 and 8th divisions fail, the reactor containment vessel spray mechanism 101 is provided in the C division, so the reactor core 4 Cooling is performed by the high-pressure core spray system 11, and the reactor containment vessel 1 can be cooled by the reactor containment vessel spray mechanism ALL, which is extremely effective in maintaining safety. In particular, since the cooling water sprayed by the reactor containment vessel spray mechanism 2 is cooled by the residual heat removal system heat exchanger 105, the reactor containment vessel 1 can be efficiently cooled.

Next, a second embodiment will be described with reference to FIG.

In this second embodiment, the first low-pressure water injection system 22 is divided into only the first low-pressure water injection system 22, the low-pressure spray system 21 is deleted, and the second low-pressure spray system 41 constituting eight sections is connected to the low-pressure water injection pipe 43 and the low-pressure water injection pump. 45 is deleted to make one system, and the residual heat removal system heat exchanger 105 and the reactor auxiliary equipment cooler 106 in the first embodiment are also deleted. The other configurations are the same as those of the first embodiment.

According to the above configuration, in the first section, when operating the first low-pressure water injection system 21, the cooling water from the suppression boule 23 is cooled through the residual heat removal system heat exchanger 31 to cool the reactor pressure vessel 21. By supplying the cooling water to the reactor containment vessel 1, it is possible to not only cool the reactor core 4, but also remove the heat of the cooling water from the suppression boule 23, and this heat-removed cooling water is supplied to the reactor containment vessel 1. The reactor containment vessel 1 can therefore be effectively cooled. This is the same for the 8 categories, low pressure water injection distribution! ! 42 and the low-pressure water injection pump 44, the reactor core 4 and the reactor containment vessel 1 can be effectively cooled.

Furthermore, in the C category, as in the first embodiment, both the high-pressure core spray system 11 and the reactor containment vessel spray mechanism 101 are installed, so that both the reactor core 4 and the reactor containment vessel 1 can be effectively sprayed. can be cooled to

In this way, all sections A, B, and C have the function of cooling the reactor core 4 and the reactor containment vessel 1, so even if any two sections should fail, the reactor core 4 and the reactor It becomes possible to reliably cool the reactor containment vessel 1. For example, consider the following accident, which is the most severe case that would never occur in reality.

First, it is assumed that the low-pressure water injection pipe 27 of the low-pressure water injection system 22 in the first section breaks inside the reactor containment vessel 1 . And in-house power supply 2
9 is lost, and at the same time 8 categories of emergency diesel power generation 1!
Suppose that 150 also breaks down. In this case, only the C category operates properly. The C-class cooling system in this embodiment has a high-pressure core spray system LL (+5) that cools the reactor core 4 and a reactor containment vessel spray mechanism 101 that cools the inside of the reactor containment vessel 1. It becomes possible to effectively cool not only the cooling chamber but also the reactor containment vessel 1 whose temperature is about to rise by the fracture flow flowing out from the fracture port of the low-pressure water injection pipe 27. Also, in the case of this second embodiment Compared to the first embodiment, one pump and one piping system are removed in the F section and the 8th section.This is A.

This is because the B and C sections each have a function of cooling the reactor core 4 and a function of cooling the reactor containment vessel 1, which simplifies the equipment while maintaining redundancy and versatility as a cooling device. This is extremely effective in reducing costs. This will be explained with reference to FIG. In Figure 4, the horizontal axis shows the number of ECC5 pumps, and the vertical axis shows the maximum temperature of the reactor containment vessel (PCV) at the time of the accident (the current value is 1) and the standardized cost (
FIG. 10 is a diagram showing the relationship between these variables as the number of pumps changes, assuming that the current value is 1. Also, the line diagram is PCV in the conventional case! The water change diagram E shows the i degree change in PCv of this example.
Diagram F shows the change in temperature, and diagram F shows the change in cost, and diagram G shows the pcvm degree limit. As is clear from FIG. 4, in the conventional case, as the number of pumps decreases, the PCV temperature increases, and when the number of pumps reaches 3°, the PCV temperature exceeds the limit value. On the other hand, in the case of this embodiment, even if the number of pumps is reduced, the PC
The V temperature increases only slightly, and there is sufficient margin for the above-mentioned limit value. Also, costs have fallen significantly at this time.

Next, a third embodiment will be described with reference to FIG.

This third embodiment replaces the eight-section residual heat removal system heat exchanger 46 of the second embodiment with a C-section high-pressure core spray system fLL and atomic This configuration is used in common with the reactor containment vessel spray mechanism 101.

Therefore, not only can the same effects as in the second embodiment be achieved, but also the cooling water cooled by the residual heat removal system heat exchanger 46 can be transferred to the reactor core 4 and the reactor containment volume f! i
1, it is possible to effectively cool the air.

(Effects of the Invention) As detailed above, the emergency core cooling system for a boiling water reactor according to the present invention consists of a reactor containment vessel, a nuclear reactor installed in the reactor containment vessel, and containing a reactor core and coolant. a first low-pressure water injection system that has a heat exchange mechanism and supplies coolant into the reactor pressure vessel in an emergency to cool the reactor core by submersion; a second low-pressure water injection system that has an exchange mechanism and supplies coolant into the reactor pressure vessel in an emergency to submerge the reactor core; and a high-pressure reactor core that cools the reactor core by spraying coolant to the reactor core in an emergency. The reactor containment vessel spray mechanism is provided in the high-pressure core spray system and sprays coolant into the reactor containment vessel.

Therefore, in the event of an accident such as a loss of coolant accident, not only the reactor core but also the reactor containment vessel can be reliably cooled, making it possible to significantly improve safety and simplifying equipment. This is extremely effective in reducing costs.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of an emergency core cooling system showing a first embodiment of the present invention, Fig. 2 is a system diagram of an emergency core cooling system showing a second embodiment, and Fig. 3 is a system diagram of an emergency core cooling system showing a second embodiment. A system diagram of an emergency core cooling system showing an embodiment, FIG. 4 is a diagram for explaining the effect, and FIG. 5 is a system diagram of an emergency core cooling system showing a conventional example. 1... Reactor containment vessel, 2... Reactor pressure vessel, 3
...Cooling water, 4...Core, A, B, C...Cooling device classification, 21...First low pressure water injection system, 41-...Second low pressure water injection system, 61...・High-pressure core spray system, 1 History 1...Reactor containment vessel spray mechanism.

Claims (2)

[Claims] (1) In a boiling water reactor equipped with a reactor containment vessel and a reactor pressure vessel installed inside the reactor containment vessel and containing a reactor core and coolant, the boiling water reactor has a heat exchange mechanism and coolant is supplied in case of an emergency. a first low-pressure water injection system that supplies coolant into the reactor pressure vessel to cool the reactor core by submersion; and a heat exchange mechanism that supplies coolant into the reactor pressure vessel to cool the reactor core by submerging water in an emergency. a second low-pressure water injection system that sprays coolant into the reactor core in an emergency to cool the reactor core; and a high-pressure core spray system that is installed in the high-pressure core spray system and sprays coolant into the reactor containment vessel. An emergency core cooling system characterized by comprising a reactor containment vessel spray mechanism. (2) The reactor containment vessel spray mechanism includes a reactor containment vessel spray pipe that is branch-connected to the high pressure core spray mechanism of the high pressure core spray system, and a reactor containment vessel spray pipe that is located within the reactor containment vessel. 2. The emergency core cooling system for a boiling water reactor according to claim 1, further comprising a spray mechanism connected to the tip of the boiling water reactor.