JPH0450798A - Emitted radiation reduction device - Google Patents

Abstract

PURPOSE:To secure the soundness of a nuclear reactor container and to reduce the exposure of its periphery by connecting vent piping which discharges the atmosphere in the nuclear reactor container to piping which links the filter device of an emergency gap processor with an air discharging cylinder. CONSTITUTION:If the gas pressure in the nuclear reactor container 2 rises for some reason to exceed designed pressure, an isolation value 16 installed in a suppression chamber 15 is opened and a 2nd isolation valve 19, a purging isolation valve 20, and while the exit valve 9 of emergency gas processing facilities are closed, a vent isolation tube 23 is opened to discharge high-pressure gas staying in the container 2 from the air discharge cylinder 10 through the vent piping 17, confluence piping 18, vent pipe 22, and piping 11. Further, when a piping part penetrating the suppression chamber 15 is unusable, the isolation valve 13 of a dry well part 12 is opened and similar operation is carried out. When the pressure in the container 2 drops below the designed pressure through a vent, the valve 16 and vent isolation valve 23 are closed and the emergency gas processing facilities 30 are actuated to remove radioactive material leaking form the container 2.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for controlling the release of radioactive materials into the surrounding environment and reducing the release of radioactive materials that occur during a reactor accident at a nuclear power plant. Relating to a reduction device.

(Conventional technology) Nuclear power plants are equipped with radioactive material release reduction devices to manage radioactive material leaked from the reactor containment vessel in the event of a nuclear reactor accident and to prevent its release into the surrounding environment. There is.

Figure 3 shows conventional radioactive substance reduction equipment. In FIG. 3, the reactor pressure vessel is protected by a reactor containment vessel 2 that houses the reactor pressure vessel 1 and a secondary reactor containment facility 3 that surrounds the reactor containment vessel 2. An emergency gas processing facility 30 is provided inside the secondary reactor containment facility 3 . This emergency gas processing equipment 30 connects a flow rate regulating valve 5 through a plurality of inlet valves 4 and two drying devices 6 for drying the sucked atmosphere inside the facility. Two blowers 7 are arranged in parallel to respectively suck the air. A filter device 8 is disposed on the discharge side of these blowers, and this filter device 8
Two outlet valves 9 are disposed in parallel on the downstream side of the exhaust pipe 10, and a plumber 1 that opens at the upper end of the exhaust pipe 10 is connected to the downstream side of the outlet valves 9.

Further, a vent pipe 14 equipped with an isolation valve 13 is connected to the dry well 12 of the reactor containment vessel 2 to scavenge the atmosphere, and a suppression chamber 15 that stores pool water is similarly equipped with an isolation valve 16. A vent pipe 17 is connected. The vent pipes 14 and 17 merge to form a confluence pipe 18, which is connected via a second isolation valve 19 to a pipe between the inlet valve 4 and the flow rate regulating valve 5 of the emergency gas processing equipment 30. Further, the confluence pipe 18 is branched on the upstream side of the second isolation valve 19 and connected to the ventilation system 21 of the reactor building via a purge isolation valve 20. In the above-described configuration, when a reactor accident occurs within the reactor containment vessel 2, the following operations are performed.

Isolation valve 13. installed in vent pipe 1.4.17 connected to reactor containment vessel 2 during reactor operation. The IS, second isolation valve 19, and purge isolation valve 20 are closed, the inlet valve 4, flow rate adjustment valve 5, and outlet valve of the emergency gas processing equipment 30 are closed, and the blower 7 is stopped and in a standby state. There is.

When a nuclear reactor accident occurs inside the reactor containment vessel 2, the pressure inside the reactor containment vessel increases and radioactive materials leak into the secondary reactor containment facility 3 according to the leakage rate of the reactor containment vessel 2. I'll come. Therefore, when a reactor accident signal occurs, the reactor secondary containment facility 3 is isolated, and at the same time, the inlet valve 4, flow rate adjustment valve 5, and outlet valve 9 of the emergency gas processing equipment 30 are opened, and the blower 7 is started. The atmosphere in the reactor secondary containment facility is maintained at negative pressure, and radioactive substances are removed using a drying device 6 and a filter device 8. As a result, even in the unlikely event of a nuclear reactor accident, the design was such that radioactive materials could be managed and removed.

(Problem to be solved by the invention) However, in the conventional radioactive material release reduction equipment described above, the emergency gas treatment equipment is designed to treat the atmosphere (atmospheric pressure state) of the secondary reactor containment facility. , cannot process high-pressure gas (about several kg/edg to 10 kg/cdg) or high-temperature steam. For example, if the internal pressure of the reactor containment increases due to some reason such as failure to inject cooling water into the reactor or failure to remove heat from the reactor after a nuclear reactor accident, the integrity of the reactor containment can be ensured. From this point of view, it is preferable to use equipment that can exhaust the gas in the reactor containment vessel.

However, in conventional equipment, even if the isolation valve 16 or the isolation valve 13 is opened and the second isolation valve 19 is opened in an attempt to lead the gas to the emergency gas processing equipment 30, the equipment may be damaged due to the small processing capacity and high gas pressure. There was a fear that it would become unusable in practice.

Another vent route is to open the isolation valve 16 or isolation valve 13, open the purge isolation valve 20, and lead to the reactor building ventilation system 21, but this route also leads to the reactor building ventilation system when the reactor building ventilation system is at normal pressure. Because of its design, there was concern that it could be damaged. In addition, since the secondary reactor containment facility 3 is in an isolated state, it cannot be introduced into the ventilation system and is discharged from the reactor containment vessel 2 into the secondary reactor containment facility, which is important for safety. There was a possibility of damage.

The present invention has been made based on the above circumstances, and in the event of a nuclear reactor accident, if the gas pressure inside the reactor containment vessel rises for some reason and there is a risk of damage, it is possible to release gas to the atmosphere. The purpose of this project is to provide equipment for reducing released radioactivity that can ensure the integrity of the reactor containment vessel, manage radioactive materials, and reduce exposure to surrounding areas.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, in the present invention, radioactive substances are removed from the air inside the building through a filter device during a reactor accident at a nuclear power plant, and the radioactive substances are A vent pipe for exhausting the atmosphere inside the reactor containment vessel is connected to a pipe connecting the filter device and the exhaust pipe of the emergency gas processing equipment for exhausting the removed air inside the building through the exhaust pipe. Provided is an emitted radioactivity reducing device characterized by:

(Function) In the emitted radioactivity reduction equipment configured in this way, when there is a risk that the gas pressure in the reactor containment vessel will rise above the design value, the reactor containment vessel isolation valve is opened and the filter device The integrity of the reactor containment vessel can be ensured by transferring high-pressure gas through the vent pipe that connects the exhaust stack to the piping that connects the exhaust stack, and allowing the gas inside the reactor containment vessel to flow from the exhaust stack. After venting is complete, radiation exposure to the surrounding area can be reduced by removing radioactive materials using emergency gas processing equipment.

(Example) FIG. 1 shows an example of the present invention. Note that the same parts as in FIG. 3 are given the same reference numerals, and the explanation of the structure of the parts will be omitted.

In FIG. 1, a vent pipe 22 is arranged downstream of the isolation valve 13.16, and branches from one of the purge pipes 14.17 and merging pipe 18 that connect to the second isolation valve 19 and the purge isolation valve 20, and is used for emergency purposes. It is connected to a pipe 11 between an outlet valve 9 and an exhaust stack 10 of the gas processing equipment. A vent isolation valve 23 having an isolation function is installed in the vent pipe 22.

In the above-described configuration, the vent pipe 142.17 and the confluence pipe 18 are steel pipes with a diameter of about 600 Ym, for example, and have a diameter of about 10 mm.
It should have the wall thickness of a cabinet, and be able to secure a pressure resistance of about 1101c/dg. Isolation valve 13.16 and second
The isolation valve 19 and the purge isolation valve 20 also have the same pressure resistance as described above.

Conventionally, the pressure capacity was the same as that of the reactor containment vessel, and the pressure was about 3 to 4.
kg/aj g, and the present invention has a structure with enhanced pressure resistance. Newly installed vent pipe 2
The diameter of the vent isolation valve 2 and the vent isolation valve 23 is approximately 3001 m, and this piping is a pipe equivalent to Schedule 40 based on JIS and can secure a pressure resistance of approximately 10 kg/cig.

Next, the outlet valve 9 of the emergency gas processing equipment and the pipe 11 connecting the outlet valve 9 and the exhaust stack 10 have a diameter of approximately 300 m, and are equivalent to Schedule 40 based on JIS.
The pressure resistance has been increased by about 10 kg/cdg, and the pressure is 0.2 to 0.3 kg, which is conventionally required for emergency gas processing equipment.
It has significantly improved pressure resistance compared to g/cafg.

In the above configuration, in the unlikely event that a nuclear reactor accident occurs, the gas pressure in the reactor containment vessel 2 rises due to some reason (a) that could be caused by failure of cooling water injection, failure of heat removal, etc. It is assumed that a situation occurs in which the design pressure of the reactor containment vessel 2 is exceeded.

In this case, the isolation valve 16 installed in the suppression chamber 15 is opened, the second isolation valve 19, the purge isolation valve 20, and the outlet valve 9 of the emergency gas processing equipment are closed, and the vent isolation valve 23 is opened. Therefore, the high pressure gas accumulated in the reactor containment vessel is discharged through the vent pipe 17, the merging pipe 18, and the vent pipe 2.
2 and the plumber 1 and are discharged from the exhaust stack 1o.

The venting start pressure at this time is selected within a range that exceeds the design pressure of the reactor containment vessel, 3 to 4 kg/alfg, and is within 10 kg/cdg, which does not damage the reactor containment vessel.

Radioactive materials generated in the reactor containment vessel are scrubbed with suppression pool water in the suppression chamber to remove radioactive particles and soluble radioactive iodine, so they do not need to pass through the filter device of the emergency gas processing equipment. Highly efficient removal is also achieved.

If the pressure in the reactor containment vessel drops below the design pressure due to venting, the isolation valve 16 and vent isolation valve 23 are closed and the emergency gas processing equipment is activated to prevent radioactive materials leaking from the reactor containment vessel. The same operation as in the conventional embodiment is performed to remove .

If the piping section that penetrates the suppression chamber cannot be used due to flooding or other reasons, open the isolation valve 13 in the dry well section and perform the above operation to bring the internal pressure of the reactor containment vessel to the design value. It is possible to lower it below.

When this example is used, in the event that the design pressure of the reactor containment vessel is exceeded, the reactor containment vessel, secondary reactor containment facility, and equipment important for safety installed therein can be High-pressure gas inside the reactor containment vessel can be released without causing damage.

In this case, the effect of reducing the release of radioactive substances is expected due to the removal effect of radioactive substances due to the scrubbing effect of the suppression pool water and the effect of releasing them to high places by releasing them from the top of the exhaust stack.

Furthermore, by merging the vent pipe with the piping of the existing emergency gas processing equipment, it can be made more economically efficient than leading the vent pipe alone to the top of the exhaust stack.

FIG. 2 shows an example of application of the present invention. In the embodiment shown in FIG. 1, the isolation valves 13, 16 and the vent isolation valve 23 are duplicated in parallel, and from the viewpoint of improving reliability, the valves are remotely driven using an emergency battery as a power source. Similarly, the emergency gas treatment equipment outlet valve 9, which closes when venting, is duplicated in series and remotely driven using an emergency battery as the power source, and a power source is provided upstream of the second isolation 19 and purge isolation valve 20. A remote stop valve 24 is installed using the battery as an emergency battery.

Further, on the pipe 11 leading to the exhaust pipe, and downstream of the vent pipe confluence, a radiation measurement element 25 and a flow meter 26 are provided.
are placed.

With this configuration, the amount of radioactivity released during venting can be managed.

〔Effect of the invention〕

As is clear from the above, in the numerical specific radioactivity reduction device of the present invention, in the unlikely event that the gas pressure in the reactor containment vessel becomes higher than the design pressure in the event of a nuclear reactor accident, the reactor containment vessel and reactor High-pressure gas can be pumped out of the exhaust stack without damaging the secondary containment facility and the safety-critical equipment installed therein.

[Brief explanation of drawings]

Fig. 1 is a system diagram of an emitted radioactivity reduction device showing one embodiment of the present invention, Fig. 2 is a system diagram showing another embodiment of the invention, and Fig. 3 is a conventional example of a numerical ratio radioactivity reduction device. FIG. 1... Reactor pressure vessel 2... Reactor containment vessel 3... Reactor secondary containment facility 8... Filter device 1
0... Exhaust pipe 11... Piping 13, 1
6... Isolation valve 14, 17, 22... Vent pipe 18... Merging pipe 23... Vent isolation valve 30... Emergency gas processing equipment agent Patent attorney Noriyuki Chika

Claims (1)

[Claims] The filter of emergency gas processing equipment that removes radioactive substances from the air inside a building through a filter device in the event of a reactor accident at a nuclear power plant, and exhausts the air inside the building from which the radioactive substances have been removed through an exhaust stack. A device for reducing emitted radioactivity, characterized in that a vent pipe for exhausting the atmosphere inside a reactor containment vessel is connected to a pipe connecting the device and an exhaust stack.