JPH03209193A - Vent device for nuclear reactor container - Google Patents

Abstract

PURPOSE:To prevent environmental pollution due to fission products (FP) accumulated in a nuclear reactor by leading the gaseous atmosphere in the container of a plant, where an accident occurs, into pressure control water of a wet well. CONSTITUTION:After a serious accident occurs, blind flanges 27 and 127 are detached and a building connection pipe 28 is connected, and a wet well isolating valve, air operating valves 25 and 26, and air operating valves 124 and 125 of an adjacent plant are successively opened. The gaseous atmosphere in a dry well 4 of a nuclear reactor container 2 rises in pressure control water 6 of a wet well 5 through a vent tube 7 and has FP removed in a certain degree, and thereafter, it is led to the adjacent plant through pipes 11, 14, and 28 and is discharged into pressure control water 106 of a wet well 105 through a pipe 121. Thus, the gaseous atmosphere in the nuclear reactor container 2 of the plant where the accident occurs is discharged to the dry well 104 of the adjacent plant to prevent the damage of the container 2 due to an excessive pressure. The gaseous atmosphere is subjected to scrubbing by pressure control water 6 and 106 and FP pollution is very reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a nuclear reactor containment vessel venting device used in a nuclear power plant.

(Prior art) Reactor containment vessels used in nuclear power plants are installed for the purpose of preventing fission products (hereinafter referred to as FP) accumulated in the reactor from being released into the environment in the event of an accident. It has been done. Although this is unlikely to happen in a nuclear power plant with such a reactor containment vessel, an abnormal event may occur and the means of supplying cooling water to the reactor pressure vessel may be completely lost. It is a good idea to take measures to ensure that the safety of nuclear power plants is not lost even in the event of an accident in which the nuclear power plant loses its safety, or an accident in which the heat removal function is completely lost from the reactor containment vessel (hereinafter referred to as a "severe accident"). It is being done. Based on the knowledge of probabilistic safety evaluation to date, the flow of severe accidents can be broadly divided into the following two cases. One of these is the case where the means of supplying cooling water to the reactor pressure vessel is completely lost. At this time, a core meltdown occurs first, and after the molten core penetrates the reactor pressure vessel, it becomes dry. released into the well. After that, the inside of the reactor containment vessel is pressurized by the decay heat of the molten core, and the melting reactor? The reactor containment vessel suffered overpressure failure due to non-condensable gases such as Co, H, etc. generated from the core-concrete reaction between the core concrete and the concrete that constitutes the drywell floor, and a large amount of FP was released into the environment. It will be released. The other case is when overpressure failure of the reactor containment vessel first occurs due to the complete loss of the heat removal function from the reactor containment vessel. This causes the pressure suppression water in the wet well to boil under reduced pressure, which causes the cooling water replenishment means for the reactor pressure vessel 8, which uses this water as a water source, to lose its function, resulting in core meltdown. The molten core then penetrates the reactor pressure vessel and is released into the dry well, but since the containment vessel has already been damaged by overpressure, a large amount of FP will be released into the environment. In any of the above cases, it is important to prevent overpressure damage to the reactor containment vessel in order to prevent a large amount of FP from being released into the environment, and methods for this purpose are being studied. In order to prevent overpressure damage to the reactor containment vessel,
Before the reactor containment vessel reaches its failure limit pressure, the FP damping effect in the reactor containment vessel and pressure suppression water etc.
After reducing the amount of released FP due to the P removal effect, it is necessary to release the atmospheric gas inside the reactor containment vessel to the environment (hereinafter referred to as containment vessel venting) to suppress the pressure rise inside the reactor containment vessel. Specifically, by connecting the reactor containment vessel of the plant where the accident occurred and the reactor containment vessel of the adjacent plant, the pressure increase in the reactor containment vessel of the plant where the accident occurred will be alleviated, and the FP will be placed inside the containment vessel. Containment vessel venting system that attenuates all FPs, including rare gases, by keeping them confined for a long period of time, and removes FPs with pressure suppression water from the plant where the accident occurred and adjacent plants, reducing the amount of FPs released into the environment. is being considered. (Problem to be Solved by the Invention) Various connection methods have been considered for connecting the above-mentioned containment vessel vent system with adjacent plants, but it is difficult to find a method that adheres to the single failure standard and isolation function requirements of the containment vessel. If the design is carried out, the amount of valves and piping will increase,
This will have a major impact on current plant design.
Furthermore, since FP is vented to adjacent plants, there is also the problem that if FP is released from the accident plant, the adjacent plants will be contaminated. Therefore, it is necessary to design the equipment in a way that minimizes the impact on the current plant design and prevents contamination of adjacent plants as much as possible. Therefore, an object of the present invention is to provide a containment vessel venting system for a nuclear power plant where multiple bases are located, which has a simple configuration, is connected to an adjacent plant, and minimizes contamination of the adjacent plant. [Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention makes maximum use of the existing equipment and connects the vent to the adjacent plant to a wet well pressure suppression underwater And so.

Specifically, as shown in FIG. 1, inert gas dry well and wet well side exhaust pipes 9 and 11 having openings in the dry well 4 and wet well 5, respectively, and these pipes 9 and 1l are The installed air-operated reactor containment vessel first isolation valves 10 and 12, the connection pipe 14 that connects the downstream side of the reactor containment vessel first isolation valve on each exhaust pipe, and the wet well side exhaust pipe. A discharge pipe 17 that directly connects the pipe between the first isolation valve 12 and the second isolation valve 13 of 11 and the atmospheric discharge port 20, and a discharge valve 18 and a rupture disk 19 installed on the discharge pipe 17 of the adjacent plant; The condensing pipe 21 has an opening in the pressure suppression water of the wet well and is connected to the confluence 22 on the inert gas system connecting pipe 14 through the reactor containment vessel through-hole, and the condensing pipe 2l of the adjacent plant. A condensation pipe isolation valve 24 installed in the building connecting pipe 23 connecting this confluence point with the relevant part of the adjacent plant and a second air actuator installed in the secondary containment facility part of the pipe 23 of the adjacent plant valve 25
, a blind flange 27 installed outside the secondary containment facility, and a first air-operated valve 26 installed in the connection pipe 14 connecting the discharge pipe 17 and the dry well side exhaust pipe 9. To provide a containment vessel vent system featuring the following features. (Function) In a reactor containment vessel having a containment vessel venting apparatus configured in this way, atmospheric gas inside the containment vessel of the plant where the accident occurred is transferred from the gas phase of the wet well to the adjacent plant where the accident did not occur. It can be led directly into the wet well pressure suppression water, and then when the internal pressure of the containment vessel of an adjacent plant increases, the atmospheric gas inside the containment vessel can be directly released from the wet well gas phase portion to the atmosphere discharge port. Furthermore, even if the water level in the wet well of the plant where the accident occurred rises during the course of concluding a severe accident, it has a function that allows atmospheric gas within the containment vessel to be directly guided from the dry well into the pressure suppression water in the wet well of the adjacent plant. There is. In addition, there are piping for releasing the atmospheric gas inside the containment vessel into the environment, piping for guiding the atmospheric gas inside the containment vessel of the plant where the accident occurred into the pressure suppression water of the adjacent plant, and because these pipings penetrate the containment vessel, they are connected to the containment vessel. At least two isolation valves are required for each. The present invention can be constructed using only these minimum necessary devices and satisfies all three functions mentioned above. (Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to FIG. In FIG. 1, a reactor containment vessel 2, 102 is housed in a secondary containment facility 83, 103, and a reactor pressure vessel 1, 101 is disposed within this reactor containment vessel 2, 102. ing. This reactor containment vessel 2,102 is mainly 2
The space that accommodates the reactor containment vessel 1, 101 is a dry well 4, 104, and the space that accommodates the pressure suppression water 6 is a wet well 5, 105. The dry well 4, 104 and the wet well 5, 105 communicate with each other through a vent pipe 7, 107. A vacuum breaker valve 8, 108 that opens in the event of an accident is provided above the wet well 5, 105.

The dry well 4, 104 has an inert gas dry well side exhaust pipe (hereinafter referred to as dry well side exhaust pipe).
9, 1.09 are connected via a dry well first isolation well 10. Further, in the gas phase portion of the wet well 6, 106, an inert gas-based wet well side exhaust pipe (hereinafter referred to as wet well side exhaust pipe) 11, 111 is connected to a wet well first isolation valve 12, 112 and a second isolation valve. 13 and 113, and the other end is open into the secondary storage facility. the wet well 6,
The condensing pipes 21, 121 with one end open in the pressure suppression water 6, 106 are connected to the dry well side exhaust pipes 9, 109 via condensing pipe isolation valves 24, 124. The first isolation valve 12 of the dry well side exhaust pipe 9, 109 and the wet well side exhaust pipe 11, 111
, 112 and the second isolation valves 13, 113 are connected via the first air-operated valves 26, 126 to the connecting pipes 14, 114.
connected by. The connecting pipes 14, 114 further include discharge valves 18, 118, rupture disks 19,
119 to exhaust pipes 17 and 117 that lead gas to exhaust towers 20 and 120, which are air discharge ports.
The dry well side exhaust pipe 9 of each plant,
Connection parts 22, 122 with other piping of 109 are second air operated valves 25, 125 and blind flanges 27, 127.
The buildings are connected by this junction 28.
In the above configuration. The operation of the embodiment will be explained assuming that a severe accident occurs in the reactor containment vessel 2 and the containment vessel is pressurized. After a severe accident occurs, when it is decided to vent the containment vessel, the blind flange 27
．． 127 and connect the building connecting pipe 28. All the isolation valves and air-operated valves in the figure are closed by the reactor containment isolation signal due to high pressure in the reactor containment vessel or high radioactivity in the reactor containment vessel. For this reason, the first wet well
The isolation valve 12, the first and second air-operated valves 26 and 25, and the second and first air-operated valves 125 and 124 of the adjacent plant are sequentially opened manually. As a result, the atmospheric gas in the dry well 4 of the reactor containment vessel 2 rises through the vent pipe 7 into the pressure suppression water 6 of the wet well 5, and after a certain amount of FP is removed (hereinafter referred to as scrubbing), it becomes inert. Gas system wet well side exhaust piping l1. Connecting pipe l
4 and the building end pipe 28 to an adjacent plant, and is directly discharged into the pressure suppression water 106 of the wet well 105 via the condensation pipe 121. This released atmospheric gas in the containment vessel of the accident plant is scrubbed again and transferred to the gas phase of the wet well 105 of the adjacent plant. Therefore, the pressure in the gas phase increases and the vacuum breaker valve 108
is activated, the atmospheric gas accumulated in the wet well gas phase flows into the dry well 104. In this way, the atmospheric gas in the containment vessel of the plant where the accident occurred is released into the dry well of the adjacent plant, which alleviates the increase in the internal pressure of the containment vessel of the plant where the accident occurred, causing overpressure damage to the containment vessel of the plant where the accident occurred. is prevented. Furthermore, even if the atmospheric gas in the containment vessel of the plant where the accident occurred contains a high concentration of FP, the atmospheric gas released into the dry well 104 of the adjacent plant where the accident did not occur will be the pressure suppression water 6, 106, the particulate FP concentration in the atmospheric gas is low.
Contamination by FP in the dry well 104 of the adjacent plant can be kept to an extremely low level. After a sufficient period of time, if the internal pressure of the containment vessel of the adjacent plant rises and reaches the vent pressure or higher, the wet well first isolation valve 112 installed in the inert gas system wet well side exhaust pipe 111 Then, open the discharge valve 118 installed in the pressure-reinforced discharge pipe 117 that branches from the wet side exhaust pipe 111 and opens to the atmosphere discharge port (exhaust tower) 120. Rupture disk 11 on discharge pipe 117
9 is designed to be damaged at pressure exceeding the containment vessel vent pressure, so the gas phase part of the wet well 105 and the atmosphere discharge port 120 are connected, and the atmospheric gas of the dry well 104 is discharged from the vent pipe 107 into the pressure suppression water 106. After further scrubbing, the gas is directly discharged from the wet well gas phase to the atmospheric discharge port (exhaust tower) 120. In this case, the amount of FP released into the environment can be kept extremely low because it remains in the dry well 104 for a long time and is sufficiently attenuated, and is further scrubbed by the pressure suppression water 106. In addition, during the process of resolving the severe accident, the water level of the wet well in the plant where the accident occurred rose and the wet well side exhaust pipe 1L
may become submerged, making it impossible to vent the containment vessel. In such a case, wetwell first isolation valve 1
2 and open the dry well first isolation valve 10, the atmospheric gas in the containment vessel of the plant where the accident occurred can be directly guided from the dry well side exhaust pipe 9 into the wet well pressure suppression water of the adjacent plant. The building junction 28 will be installed using an appropriate method, including underground burial, taking into account economic efficiency and plant design.

Next, the second embodiment will be explained based on FIG. 2. First, in FIG. 2, parts that are the same as those in FIG. This example describes a plant in which the reactor containment vessel through-hole for piping that guides the containment vessel atmospheric gas of the newly installed accident plant into the pressure suppression water of another plant does not exist on the wet well side but only on the dry well side. This applies to The difference from the first embodiment is that a condensing pipe 31 leads the containment vessel atmospheric gas of the accident plant to pressure suppression water 106 of another plant.
, 131 are inserted into or connected to the vent pipes 30, 130 via the dry wells 4, 104. Even in this case, the atmospheric gas in the containment vessel of the plant where the accident occurred is directly led into the pressure suppression water 6, 106 of the adjacent plant, and the same function as in the first embodiment is expected.

〔Effect of the invention〕

In a nuclear power plant with such a reactor containment vessel, if a severe accident occurs and the pressure inside the reactor containment increases and FP is released into the containment vessel, the reactor containment vessel of an adjacent plant may be affected. The free space volume can be used to alleviate the increase in internal pressure in the reactor containment vessel of the plant, and all FPs including rare gases can be attenuated. In addition, gas containing FP is scrubbed by pressure suppression water from the plant where the accident occurred and adjacent plants, so FP is released into the environment.
The amount can be kept extremely low. As a result, in the event of a severe accident, it is possible to prevent overpressure damage to the containment vessel and to prevent a large amount of FP from being released into the environment. It is possible to provide a containment vessel venting facility that achieves such effects with the minimum required valve and piping configuration, and that makes it possible to suppress contamination in the dry well of an adjacent plant to the lowest possible level. This has a very beneficial effect from the viewpoint of economic efficiency of the containment vent equipment and property protection of adjacent plants.

[Brief explanation of drawings]

Claims (1)

[Claims] In a nuclear power plant where multiple plants are located, a reactor pressure vessel, a reactor containment vessel that stores this reactor pressure vessel, a secondary containment facility surrounding this reactor containment vessel, and the reactor containment vessel A dry well formed in the upper part of the interior of the container and accommodating the reactor pressure vessel, a wet well containing pressure suppression water housed below the reactor pressure vessel, and a dry well having an opening in each of the dry well and the wet well. A side exhaust pipe and a wet well side exhaust pipe, a dry well first isolation valve and a wet well first isolation valve installed in each of these exhaust pipes, and a first isolation valve of each of the dry well and wet well side exhaust pipes. The connection pipe connecting the downstream side, the wet well side exhaust pipe, the first wet well isolation valve, and the first wet well
A discharge pipe that connects the pipe between the second isolation valves arranged downstream of the isolation valve and the atmospheric discharge port, a discharge valve and a rupture disk installed in the discharge pipe, and a rupture disk housed in the wet well. A condensing pipe that has an opening in the pressure suppression water and is connected to the dry well side exhaust pipe via a reactor containment vessel through hole, a condensing pipe isolation valve installed in this condensing pipe, and adjacent to this confluence point. A building connecting pipe that connects the relevant part of the plant, a second air-operated valve installed in a part of the building connecting pipe inside the secondary containment facility, and a blind flange installed outside the secondary containment facility; A nuclear reactor containment vessel venting device comprising: a first air-operated valve installed in a connecting pipe connecting the discharge pipe and the dry well side exhaust pipe.