JPS5950398A - 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 relates to an emergency gas treatment device for discharging contaminated air from inside a reactor building of a nuclear facility having a nuclear reactor such as a nuclear power plant.

[Technical background of the invention]

4. Reactor piping ruptures during operation of a nuclear power plant, etc.
■If an accident occurs, there is a risk that the inside of the reactor building will be contaminated by radioactive materials. For this reason, in the past, in the event of such an accident, the reactor building was isolated from the outside world, and an emergency gas treatment system was used to maintain negative pressure inside the building to prevent air from directly leaking outside. The contaminated air inside the building is filtered and then diluted and released outdoors.

As shown in the system diagram in Figure 1, a specific example of such equipment is such that the normal ventilation air conditioning system in the reactor building 1 is stopped by an isolation signal at the same time as an accident occurs, and the system penetrates the inside of the reactor building 1. The air conditioning ducts inside the reactor building are closed off by valves and the reactor building is separated from the outside.

Then, the contaminated air flowing into the filter row 4 through the isolation valve 3 of the exhaust flow path 2 is transferred to the demi-mess 4 constituting the filter row 4.
a, heating coil 4b for relative humidity control, filter 4c
1 High performance particle filter 4d.

After the radioactive contaminants are removed as much as possible by the iodine removal charcoal filter 4e and the high-performance particle filter 4f, the air is discharged to the final exhaust line 6 by the exhaust fan 5. Further, the flow rate of air to the emergency gas processing device is maintained at a set flow rate by opening and closing a flow rate regulating valve 8 by a flow rate control system 7.

[Problems with background technology]

However, the conventional emergency gas treatment equipment has the following drawbacks.

Therefore, in anticipation of an emergency, the reactor building should be airtight so that the amount of air leakage per hour can be kept to less than 1/24 of the free nitrogen interstitial volume in the building when the negative pressure inside the building is about a few millimeters of water. However, in reality, even if the differential pressure between the inside and outside of the building is constant, the air leakage rate starts from a good airtight state at the beginning of construction, but gradually deteriorates over time, and eventually reaches the maximum level. There is 1 workability to reach the leakage tolerance.

For this reason, in conventional devices that treat contaminated air using a constant flow rate control method, it is necessary to set the flow rate to an appropriate amount based on the airtight seal condition, but this is extremely difficult. If the set flow rate is too low, there is a risk that the necessary differential pressure will not be obtained and the contaminated air inside the building will leak directly from the building to the outside.On the other hand, if the set flow rate is Since e-air is processed and exhausted more than necessary, this also inevitably increases the amount of radioactive materials released outdoors.

Moreover, the appropriate flow rate to maintain the differential pressure appropriately is influenced by wind speed and other external conditions, and it is nearly impossible to set the appropriate flow rate while taking into account these factors in addition to the aging of the airtight seal.

In addition, the design flow rate of the exhaust fan of the emergency gas treatment equipment is generally designed according to the maximum allowable leakage capacity of the building, but in the early stage of construction when the airtightness is good, the set flow rate is extremely low. It becomes a small one.

There is a problem in that it is difficult to obtain stable operating conditions for the exhaust.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned problems of the conventional equipment, and makes it possible to reduce the amount of radioactive substances released outside the reactor building and the radioactive substances inside the building, regardless of changes in the reactor building over time. The purpose is to provide emergency gas treatment equipment.

[Summary of the invention]

In order to achieve the above object, an emergency gas treatment device according to the present invention purifies contaminated air inside a nuclear reactor building using an exhaust flow path equipped with a filter row and an exhaust fan, and discharges the purified air to the outside. A return air flow path is connected to the downstream exhaust flow path to return some of the purified air to the reactor P building, and a flow rate adjustment valve is installed in the 8-air VIL path to maintain a constant running pressure inside and outside the reactor building. The outline of this is to maintain the following.

[Embodiments of the invention]

An example of the actual journey of the present invention will be explained in detail below based on FIG. 2.

Incidentally, the same numbers are given to the same members as in the conventional equipment d.

Isolation valves 3, 3 are provided upstream of the exhaust flow path 2 led out from the reactor building 1, and a filter row 4 is provided following the isolation valves 3, 3. This filter array 4 is a demister 4a
, heating coil 4b for relative temperature control, filter 4c
, a Finotota 4d for high-performance particles, a charcoal filter for removing iodine 4e, and a filter for high-performance particles 4f, which removes radioactive contaminants from contaminated air from the reactor building 1. 4, an exhaust fan 5 is provided, and this exhaust fan 5
The purified air is discharged to the final exhaust system 6.

Further, one end of the return air flow path 9 is connected to the exhaust flow path 2 downstream of the exhaust fan 5 and upstream of the final exhaust system 6, and the other end of this return air flow path 9 is connected to the reactor building (■). , a part of the air purified by the filter rows 4 is returned to the reactor building.

A flow rate regulating valve 10 is provided in the middle of the return air passage 9,
This flow rate adjustment valve 10 is used to measure the differential pressure inside and outside the building.

The opening degree is adjusted based on a signal from the control system 11, and the return air flow rate is controlled. Furthermore, a cooling device 12 is provided in the return air flow path 9 to prevent the temperature rise of the surrounding air inside the reactor building 1 due to the purified air heated by the heating coil 4b for relative humidity control being returned directly into the reactor building 1. are doing.

Further, a flow fine adjustment valve 13 is provided between the exhaust fan 5 and the I'ij final exhaust system 6 in order to improve the reliability of control. Further, the capacities of the return air flow path 9, the flow rate regulating valve 10 provided in the return air flow path 9, and the cooling device 12 are set to such an extent that the entire amount of the discharge flow train of the exhaust fan 5 can pass therethrough.

In addition, Figure 3 is a graph showing the change in radioactivity concentration inside the building, and the calculation is based on the air leakage per hour into the building, 41'
% of the building airtightness design value] Assuming that this is 1/48 of the free space volume inside the building, the exhaust fan discharge flow rate pattern is different between the case where air is not returned into the building as in the conventional device and the case where air is not returned into the building as in the conventional device. This is a comparison with the case where air is returned to the building. As is clear from this figure, when using the bag according to the present invention, the radioactivity concentration inside the building is reduced by almost half compared to the conventional method. Furthermore,
As the amount of radioactive material inside the building is reduced, the amount of radioactive material released outdoors will also be halved.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, the exhaust volume is directly controlled by the pressure difference between the inside and outside of the reactor building. There is no need to change or adjust the set flow rate depending on the condition of the building's airtight seal, and the discharge flow rate itself is kept almost constant without narrowing down the discharge flow can of the exhaust fan like in the past, and the exhaust flow rate can be adjusted. By doing so, a portion of the air was returned to the building, which stabilized the operating conditions of the exhaust fan and maximized the purification effect of the filter array.

By returning the air purified by the filter array into the building, it is possible to reduce the amount of radioactive material inside the iSM and also to reduce the amount of radioactive material released outside the building.

Further, by providing the cooling device d in the return air flow path, there are many advantages such as being able to suppress the temperature rise of the air inside the building and relaxing the equipment design temperature conditions.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a conventional emergency gas processing equipment, Fig. 2 is a system diagram of an emergency gas processing equipment according to the present invention, and Fig. 3 shows transient changes in radioactivity concentration inside the building at the time of an accident. It is a graph. DESCRIPTION OF SYMBOLS 1... Reactor building, 2... Exhaust flow path, 4... Filter row, 5... Exhaust fan, 9... Return air flow path, 10
...Flow rate adjustment valve, 12...? Yayoso trade. Applicant's agent Kiyoshi Inomata 545

Claims (1)

[Scope of Claims] 1. An exhaust flow path that atomizes contaminated air inside the reactor building through a filter row and discharges it to the outside by an exhaust fan;
In order to return the air purified in the exhaust flow path into the reactor building, an "exhaust flow path ζ" is installed downstream of the exhaust fan.
The connecting return air flow path is characterized by comprising a flush control valve provided in the return air flow path in order to control the air flow path in the return air flow path and keep the differential pressure between the inside and outside of the reactor building constant. emergency gas treatment equipment. 2. The emergency gas processing device according to claim 1, wherein the return air passage is equipped with a cooling device.