JPS59157599A - Emergency gas processing device - 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 provides a method for filtering radioactive material-contaminated air inside the reactor and building in the event of a nuclear reactor accident in a nuclear facility having a nuclear reactor such as a nuclear power plant. The present invention relates to an emergency gas treatment device that removes radioactive substances contained in the gas and then dilutes and discharges them outdoors, and particularly relates to an emergency gas treatment device that can improve reliability.

[Technical background of the invention]

Generally, if an accident such as a pipe rupture occurs during nuclear reactor operation, there is a risk that the inside of the reactor building will be contaminated by leaked radioactive materials. Therefore, in such cases, the inside of the building must be maintained at a negative pressure to prevent direct air leakage to the outside, and the air inside the building must be filtered to remove the radioactive materials it contains before being diluted and released outdoors. method is adopted.

Conventionally, as an emergency gas treatment device used for such a purpose, a device having a structure shown in FIG. 1 has been used.

In this system, in the event of a nuclear reactor accident, the normal ventilation air conditioning system is stopped by an isolation signal in the reactor building 1, and the supply air duct is stopped in the air conditioning duct that penetrates the reactor building 1. 2 is closed by supply-side isolation valves 3a and 3b, and exhaust duct 4 is closed by exhaust-side isolation valves 5a and 5b, respectively, so that the reactor building 1 is isolated from the outside. After that, the air inside the building is led to an emergency gas treatment device installed outside the building and treated.

This emergency gas treatment device is formed on the downstream side of a main pipe 6 branched from the upstream side of the exhaust side isolation valve 5a of the exhaust duct 4, and in order to improve the reliability of the system, the main pipe 6 is connected to a branch pipe. It is branched into an A system consisting of 6A and a B system consisting of a branch pipe 6B, and is configured so that each system can be switched and operated as necessary. For example, only the A system is used during filter processing, and the B system is on standby as a backup system.

In this case, the air inside the building is first supplied to the main pipe 6 branching from the exhaust duct 4, the system switching valve 7, and the filter row population valve 8.
After passing through the filter row 9A and removing as much radioactive material as possible, it is discharged to the final exhaust system 12 via the filter row outlet valve 10A1 and the exhaust fan IIA. be done. The filter row 9A includes a demister 9a and a heating coil 9b for controlling relative humidity.
, pre-filter 9c, pre-high performance particle filter 9
d, a charcoal filter for unremoved particles 9e, a post-installed high-performance particle filter 9f, etc. are arranged in order from the upstream side to the downstream side.

In this case, the filter row artificial valve 8B of the B system is fully closed.

The exhaust flow rate of this emergency gas treatment equipment is the amount that will maintain the air pressure inside the reactor building at a constant negative pressure below atmospheric pressure even in the event of an accident, and is determined during the system test before use. It is determined in advance according to the actual building leakage amount so that the building negative pressure is equal to or higher than , and the value is set by adjusting the opening degree of the filter row outlet valve 10A.

By the way, when one filter row population valve 8A is fully closed and the other filter inlet valve 8B is fully open and the operating system of the emergency gas treatment device is switched from system A to system B (4), no exhaust gas is sent to system A. Due to the decay heat of the radioactive substances adsorbed on the charcoal filter 9e for removing 5 elements, the temperature of the charcoal filter 9e for removing 5 elements increases. There is a risk of ignition. For this purpose, as shown in FIG. 1, the filter row bypass valve 13 arranged between both filter rows 9A and 9B is opened, and the normally open filter row outlet piping bypass valve 14 and bypass piping 15 are connected to the B system on the operating side. A bypass airflow of about 10% of the exhaust flow rate also flows through the unremoved charcoal filter 9e in the filter row 9 of the A system, which is the side where the operation is stopped, so that cooling can be performed. Here, the exhaust flow rate of approximately 10 cm is used as the necessary air volume for cooling the decay heat of the unremoved charcoal filter 9e because the self-ignition temperature of the unremoved charcoal filter 9e is approximately 290°C. This is because it is necessary to allow a sufficient margin to keep the temperature below this temperature. Such a method is usually called a bypass tie line method.

In addition, the filter row population valve 8A and the filter row outlet valve 1
0A has an interlock with the exhaust fan IIA, and in order to clarify the operating system, it is closed when the exhaust fan IIA stops operating. this .

The same applies to the B system side.

[Problems with background technology]

The conventional emergency gas processing apparatus described above has several problems as described below.

In other words, the reactor building 1 is designed to be airtight in order to suppress the amount of air leakage per hour when the negative pressure inside the building is about a few millimeters of water column to about 1 of the free space volume of the building, assuming an emergency. Designed. However, in reality, the amount of air leakage gradually decreases from the airtight state at the initial stage of construction due to aging of the airtight seal, and there is a possibility that the amount of air leakage will eventually reach the maximum allowable amount of leakage. The design flow rate of the one-way valve regular gas treatment equipment exhaust fan is generally designed according to the maximum leakage capacity of the building, so if the airtightness is good at the beginning of construction, the set flow rate may be very small. Therefore, there is a drawback that it is difficult to obtain a stable operating state of the exhaust fan.

In addition, with conventional equipment that uses a bypass tie line method to cool the decay heat of radioactive materials adsorbed on the charcoal filter for iodine removal, a portion of the exhaust flow is used as bypass airflow, so it is difficult to If the airtightness is good, there is a risk that the required amount of cooling air for decay heat cannot be secured.

Furthermore, since the air used to cool this decay heat is air led from the reactor building, it is necessary to remove radioactive materials. However, as mentioned above, if the required cooling air volume for decay heat cannot be secured and the air temperature rises in the iodine removal charcoal filter section where decay heat exists, the iodine removal efficiency of the iodine removal charcoal filter will decrease. The air temperature in the charcoal filter for iodine removal is stable at about 99 degrees Celsius or higher until about 150 degrees Celsius, but when it reaches about 200 degrees Celsius, it decreases to about 90 degrees Celsius, and further increases to about 250 degrees Celsius.
Since it is known that the decay heat decreases to about 60q6, the bypass air for cooling the decay heat is
Some of the radioactive iodine may not be removed (7) and may be diluted and released into the atmosphere.

[Purpose of the invention]

The present invention was developed in view of the current situation, and it is possible to ensure a stable operating state of the exhaust fan and a sufficient air volume to cool down the decay heat, thereby significantly improving the reliability of equipment. The purpose is to provide an emergency gas processing device that can

[Summary of the Invention] As a means for achieving the above-mentioned object, the present invention is directed to the outlet side of the filter row on the operating side, by guiding a part of the treated air that has passed through this filter row to the outlet side of the filter row on the standby side. A backflow system is provided to cause the filter row to flow backwards, and a return system is provided on the inlet side of the standby filter row to guide the backflowing air to the inlet side of the operating system and recirculate the operating system,
Furthermore, the present invention is characterized in that a cooler is provided in at least one of the backflow system and the return system.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

(8) In FIG. 2, reference numeral 1 is the reactor building, and the air supply duct 2 of the air conditioning duct that passes through the reactor building 1 has isolation valves 3a and 3b on the air supply side, and the exhaust duct 4 has isolation valves 3a and 3b. Exhaust side isolation valves 5a and 5b are provided, respectively. In the outdoor-installed emergency gas treatment system, the base end of the main pipe 60 having the system switching valve 7 is connected to the upstream part of the exhaust side isolation valve 5a of the exhaust duct 4 to guide air inside the building. It has become.

The tip side of the main pipe 6 is connected to a branch pipe 6 as shown in FIG.
The A system and the B system are constructed by branching into two branches consisting of A and 6B, and are mutually switched and operated, and the outlet ends of both systems are connected to a single final exhaust system 12.

As shown in FIG. 2, each system includes, from the upstream side, filter row artificial valves 8A, 8B, filter rows 9A, 9B, filter row outlet valves 10A, 1013, and exhaust fan 1.
1A and IIB are provided in sequence, and each filter row "9A and 9B includes a demister 9a, a heating coil 9b for controlling relative humidity, a pre-filter 9c, a pre-installed high-performance particle filter 9d, and a charcoal filter for removing iodine. 9e, and a rear high-performance particle filter 9f, etc. Also, each system's filter row population valve 8
A, 8B and filter row outlet valve 10A, IOB
'' has an interlock with the exhaust fans IIA and nB of each system, and in order to clarify the operation system, it is closed when the exhaust fans 11A and IIB stop operating. After being filtered by the filter row 9A or 9B of that system, the air introduced into the building is diluted and discharged outdoors via the final exhaust system 12.

At the exit side position of the exhaust fan IIA of the A system, there is a second
As shown in the figure, the final exhaust system bypass piping 16 has a bypass valve 17A that controls the bypass flow rate by adjusting the opening degree and a cooler 18A that prevents the temperature of the bypass airflow from rising.
The proximal end of the bypass pipe 16A is connected between the filter rows 9B of the 13 systems and the filter row outlet valve 10B. Furthermore, as shown in FIG. 2, the base end of the final exhaust system bypass piping 16B, which has the same function as the A system, a bypass valve 17B and a cooler 18B, is connected to the exit side position of the exhaust fan IIB of the B system. The tip of this bypass piping 16B is connected between the filter row 9A of the A system and the filter row outlet valve 10A.

Furthermore, the filter row inlet valves 8A, 8B of both systems and the filter rows 9A, 9B are interconnected via a recirculation pipe 19 having a normally open recirculation valve 20, as shown in FIG. There is.

Next, the effect will be explained.

In the event of a nuclear reactor accident, the normal ventilation air conditioning system is stopped by an isolation signal within the reactor building, and the air supply duct 2 of the air conditioning duct that penetrates the reactor building 1 is closed by the isolation valve on the air supply side. 3a and 3b, and the exhaust duct 4 is closed by exhaust side isolation valves 5a and 5b, respectively, so that the inside of the reactor building 1 is isolated from the outside. Then, the air inside the building is directed to the emergency gas treatment equipment.

Here, if the A system is the operating side and the B system is the standby side, the air inside the building will be transferred to the exhaust duct 4. Main pipe (11) 6, System switching valve 79 Branch pipe 6A, Filter row population valve 8
A to the filter row 9A, where radioactive contaminants are removed as much as possible, and then passed through the filter row outlet valve 10A and the exhaust fan IIA to the final exhaust system 12.
is discharged.

By the way, the exhaust flow rate of the emergency gas treatment equipment is determined in advance according to the actual building leakage amount so that the specified building negative pressure is achieved during a system test before use, and this is determined by the filter row outlet valve 1.
It is set by adjusting the opening degree of 0A, , IOB, but in a state of good airtightness such as in the early stages of construction, the set flow rate becomes very small, and the exhaust fans IIA, II
In some cases, it may be difficult to obtain stable operating condition B.

Therefore, in such a case, the exhaust fan I of the driving side system
During operation of the IA, the bypass valve 17A of the bypass pipe 16A branching from the final exhaust system 12 is opened, and its opening degree is adjusted manually or automatically to divert a portion of the exhaust flow rate to the filter row 9B of the standby system. to the side and cause the flow to flow backwards through this filter row 9B. Then, the bypass airflow that has flown backward is passed through a recirculation pipe 19 having a recirculation valve 2o (12) to a filter row 9A of the operating side system.
to the inlet side and recirculate the driving side system. As a result, a sufficient exhaust flow rate is obtained, and a stable operating state of the exhaust fan IIA is ensured.

At this time, a part of the exhaust flow is transferred to the standby side filter row 9B.
However, since radioactive substances and the like have been sufficiently removed in advance by the filter row 9A on the operating side, they will not adversely affect the performance of the filter row 9B on the standby side.

If the airtightness of the reactor building 1 airtight seal deteriorates over time and there is a risk that the negative pressure inside the reactor building 1 will fall below a specified value, for example, measure the differential pressure inside and outside the reactor building 1. The opening degree of the bypass valve 17A is automatically or manually adjusted based on instructions from a differential pressure gauge (not shown), etc., to reduce the flow rate of the bypass airflow. As a result, the negative pressure inside the reactor building 1 is always kept above the specified value. It is possible to keep it.

On the other hand, when switching from system A to system B, which is the operation system of the emergency gas treatment equipment, close the filter row population valve 8A and filter row outlet valve 10A of system A that has been operated so far, and stop the exhaust fan IIA. At the same time, the filter row population valve 8B and filter row outlet valve 10B of system B, which were on standby, were opened, and the exhaust fan IIB was opened.
Start driving. - And the bypass valve 17B of the final exhaust system bypass piping 16B branching from the final exhaust system 12
A part of the exhaust flow is led to the outlet side of the filter row 9A of the A system whose operation has been stopped, and this filter row 9A is caused to flow backward, and the reversed air flows through the recirculation pipe 19 having the recirculation valve 20. to the input side of the filter row 9B of the B system,
This B line is recirculated.

Since sufficient air can flow through the filter row 9A whose operation has been stopped, the decay heat of the radioactive substance adsorbed on the iodine removal charcoal filter 9e of the filter row 9A causes the temperature of the iodine removal charcoal filter 9e to rise. This can effectively prevent the metal from rising and igniting. In addition, a cooler 18B is provided in the bypass pipe 16B, and since the temperature increase due to the compression heat and the decay heat caused by the exhaust fan IIB is removed here, the air temperature in the iodine removal charcoal filter 98 increases. It is possible to effectively prevent the unremoved efficiency from decreasing as a result of this.

In addition, even if the unremoved efficiency of the filter row 9A of the A system decreases due to the inability to secure the necessary air volume for decay heat cooling, the air that flows backward through the filter row 9A can be recirculated through the B system. Therefore, there is no risk that part of the 5m radioactive area will be diluted and released directly into the atmosphere.

In the above embodiment, the A system is set as the operating side and the B system is set as the standby side, and the operations and switching operations are explained. However, the same operations can be performed even if the B system is set as the operating side and the A system is set as the standby side. can be controlled by , and exactly the same effect can be obtained.

FIG. 3 shows another embodiment of the present invention, which is applied to an indoor emergency gas processing device.

In this type of emergency gas treatment equipment installed in the reactor building 1, the base end of the main pipe 6 opens into the reactor building 1, as shown in FIG. ) The tip is connected to the final exhaust system 12 via the parallel A and B systems. Each of the systems includes filter row artificial valves 8A and 8 having the same functions and configurations as in the embodiment described above.
B, filter rows 9A, 9B, filter row outlet valve 10A
, IOB, and exhaust fan IIA, 11. B are provided respectively. However, in the case of indoor installation,
As shown in Figure 3, each exhaust fan IIA and IIB are each filter row 9A, 9B
It is installed on the upstream side of the

In addition, each of the filter rows 9A, 9B and the filter row outlet valve 1
0A and IOB are mutually connected via a recirculation pipe 19 having a normally open recirculation valve 20 as shown in FIG. The filter array 91] or 9A is guided to the outlet side of the filter array 91] or 9A, and flows back through the filter array 9B or 9A. The reversed air is then connected between the filter rows 9B, 9A and the exhaust fans IIB, IIA, bypass valves: t7B, 17A and the cooler 18B.

(16) Bypass piping 16B with 18A, through 16A
- is released into the reactor building 1, and then guided to the inlet side of the operating system and recirculated through the operating system.

Next, the operation will be explained assuming that the A system is on the operating side and the B system is on the standby side.

In the event of a nuclear reactor accident, the opening operations of filter row population valve 8A, filter row outlet valve 10A, and exhaust fan IIA
Upon activation, the air in the reactor building 1 is guided to the A system, filtered, and then discharged to the final exhaust system 12. Then, a part of this exhaust flow is guided to the outlet side of the filter row 9B on the standby side through the recirculation piping 19 as necessary.
The water flows backward through this filter row 9B. The air flowing back is discharged into the reactor building 1 via the bypass pipe 16B, introduced from the open end of the main pipe 6, and recirculated through the A system.

On the other hand, when switching the operation system of the emergency gas treatment device from system A to system B, the filter row population valve 8A of system A
, the filter outlet valve 111A is closed and the exhaust fan IIA is stopped, and at the same time, the filter row population valve 8B and the filter row exit valve 1 of the B system are closed. Open OB and start exhaust fan IIB. Then, the - part of the exhaust flow is guided to the outlet side of the filter row 9 of the A system through the recirculation pipe 19, and is caused to flow backward through the filter row 9A, and the reversed air is sent to the reactor via the bypass pipe 16A. It is discharged into the building 1 and recirculated through the B system via the main piping 6.

Therefore, even in the case of an indoor-installed emergency gas processing device, the same effects as those of the outdoor-installed emergency gas processing device described above can be expected.

In both of the above embodiments, the coolers 18A and 18B are provided in the bypass pipes 16A and 16B, but they may be provided in the recirculation pipe 19 if necessary.

〔Effect of the invention〕

As explained above, the present invention guides a part of the exhaust flow rate of the operating side gas processing system to the outlet side of the filter row of the standby side gas processing system, causes it to flow backwards, and directs this reversed air to the operating side gas processing system. Since the exhaust gas is returned and recirculated, a sufficient flow rate can be ensured even when the building is airtight, such as in the early stages of construction, and a stable operating condition of the exhaust fan can be obtained.

Furthermore, since the required air volume for cooling the decay heat of the radioactive substance adsorbed on the iodine removal charcoal filter can be ensured, ignition or a decrease in iodine removal efficiency can be effectively prevented. Since a cooler is provided in the system to suppress the temperature rise of the airflow, the above effect can be further enhanced.

In addition, since the air that flows back through the filter row on the standby side is recirculated through the operating system, even if the iodine removal efficiency decreases, there is no risk that some radioactive iodine will be diluted and released into the atmosphere without being removed. .

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of a conventional emergency gas processing device installed outdoors, FIG. 2 is a system diagram showing an example of an emergency gas processing device installed outdoors according to the present invention, and FIG. FIG. 2 is a system diagram showing an example of an emergency gas treatment device installed indoors. (19) 1... Reactor building, 4... Exhaust duct, 6... Main piping, 8A, 8B... Filter row inlet valve, 9A, 9B
...filter row, IOA, IOB...filter row outlet valve, IIA, IIB...exhaust fan, 16
A, 16B... Baiba x layout L 17A. 17B...Bypass valve, 18A, 18B...Cooler, 19...Recirculation piping, addition...Recirculation valve. Applicant's agent Kiyoshi Inomata (20)

Claims (1)

[Claims] 1) A plurality of gas processing systems are installed in parallel, each having a filter row and an exhaust fan, and which are switched and controlled so that any system is on the operating side and the other system is on the standby side. In an emergency gas treatment system that guides the air inside the reactor building to the operation side system in the event of a nuclear reactor accident, filters it, dilutes it, and releases it outdoors, this filter row is installed on the outlet side of the operation side filter row. A backflow system is provided that guides a portion of the treated air that has passed through to the outlet side of the standby filter row and flows back through the standby filter row, and directs the air that has flowed back to the inlet side of the standby filter row to the operating side system. 1. An emergency scum processing device comprising: a return system for recirculating the operating system by leading to the inlet side of the system; and a cooler for at least one of the backflow system and the return system. 2) A final exhaust system installed outside the reactor building with an exhaust fan on the outlet side of the filter row, and a bypass valve and cooler between the outlet side of the operating exhaust fan and the exit side of the standby filter row. Claim 1, characterized in that the filters are connected by bypass piping to form a backflow system, and the inlet sides of both filter rows are connected to each other by recirculation piping having recirculation valves to form a return system. emergency gas treatment equipment. 3) The filter row has an exhaust fan installed on the inlet side of a detached house, and the outlet sides of both filter rows are interconnected with recirculation piping with a recirculation valve to form a backflow system. Claim 1 is characterized in that the exhaust fan and filter row of the exhaust fan and the inlet side of the operating side exhaust fan are interconnected by bypass piping having a bypass valve and a cooler to form a return system. emergency gas treatment equipment.