JPH0580637B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a device for trapping contaminated gas inside a building having a heat source therein, and particularly relates to a device for trapping contaminated gas inside a building suitable for trapping contaminated gas. .

[Background of the invention]

As an example of a device for trapping contaminated gas in a building that has a heat source inside, we use a device for trapping contaminated gas during periodic inspections (hereinafter referred to as periodic inspections) inside the reactor building of conventional boiling water nuclear power generation facilities. 1st
It is shown in FIG. 6 and FIG. 17. Figure 17 is E of Figure 16.
-E' sectional view. This device is intended to prevent the spread of radioactive materials even in the unlikely event of an accident, and the spread of contaminated gas into the reactor building is not a problem. In the conventional system, ventilation air is blown out from the outlet of the air supply duct 4 installed approximately 4 meters above the floor surface of the building, and a portion of it is sent to the reactor well 1,
Dryer/separator equipment temporary storage pool (hereinafter referred to as dryer/separator pool) 2, and spent fuel storage pool (hereinafter referred to as fuel pool) 3
Contaminated air 8 containing radioactive substances generated from the surface of the pool is sucked in through an embedded duct 7 on the wall of the pool. The other airflow is sucked in by the suction port of the exhaust duct 5 installed about 5m above the floor facing the air supply duct 4, and after removing contaminants with the airflow sucked in by the embedded duct 7 through a filter, it is passed through the main exhaust pipe. It began to be guided and released to the outside.

However, the opening of the embedded duct 7 is installed approximately 70mm above the pool water surface, and water may flow into the duct due to earthquakes or other rippling of the pool water when the pool is filled with water. A drain and isolation valve were installed to prevent water from flowing. Furthermore, since the duct is installed under the floor around the pool, there is a lot of interference with reinforcement, piping, etc., and a large number of man-hours are required for construction. When radioactive substances are emitted from the pool, it is desired to further improve the efficiency of capturing the radioactive substances.

Publicly known examples of preventing pool water from flowing into ducts are JP-A-53-131585 and JP-A-55-24612.
No. 55-46141. In addition, as a publicly known example of prevention of pollution diffusion, JP-A-55-
No. 48698, JP-A-56-46496 and JP-A-58-
There is No. 33596.

[Purpose of the invention]

An object of the present invention is to provide a device for trapping contaminated gas inside a building, which can reduce contamination by radioactive substances and further reduce radiation exposure of workers during maintenance and inspection.

[Summary of the invention]

A feature of the present invention is that in a building having a pool in which an object containing a radioactive substance is placed underwater and where the water temperature is higher than the space above, an air supply port is provided surrounding the pool to cause air to flow upward; The air supply port is connected to a blower via an air supply duct, an exhaust port is provided above the pool for exhausting contaminated gas, and the exhaust port is connected to a suction device via an exhaust duct.

[Embodiments of the invention]

Figures 18, 19, 20, and 21 show the E-E', F-F', and G-G' cross sections of Figure 16 in the conventional reactor building ventilation system, and the
This figure shows the distribution of contaminated air in the section H-H' in Figure 7.
These figures show the contaminant concentration distribution in the reactor building (concentration near the pool) using numerical simulation.
FIG. 2 is a schematic diagram of the results of determining the concentration (area where the concentration is 5% or more when taken as 100%) and the airflow state. Since the pool water temperature is higher (40 to 50 degrees Celsius) compared to the ventilation air blowout temperature (18 to 30 degrees Celsius), an upward air current occurs near spent fuel pool 3, as shown in Figures 18 and 20. Air containing radioactive contaminants from the pool flows and stagnates above the pool. FIG. 21 shows the range of contamination on the ceiling surface, and when the contaminants adhere to and accumulate on the ceiling surface, they turn into dust and fall onto the floor surface.

In this way, for the first time, numerical simulations have quantitatively revealed that the duct opening of the embedded duct in the conventional ventilation system is small.

Figures 23 and 24 are diagrams modeling the effects of inertial force 9 due to ventilation and buoyancy 10 due to heat generation in the pool 20 on the concentration distribution shape of indoor pollutants. This corresponds to the contaminant concentration distribution according to the conventional method shown in FIG. As you can see from the diagram, pool 2
The buoyant force 10 generated by the heat generation of 0 determines the airflow pattern within the building and is the largest cause of pollutant dispersion. Furthermore, in the conventional system, the inertial force 9 is orthogonal to the buoyant force 10 caused by the heat generation source, and the buoyant force 10, which is a natural phenomenon, is not effectively utilized.
Therefore, in the present invention, as shown in FIG. 22, ventilation air is blown out from air supply ducts 4a and 4b installed on the floor at the outer periphery of the pool (heat source) 20, thereby forcing air over the pool (heat source). A rising air current is created, and radioactive pollutants generated from a pool (heat source) are carried on this air current and are efficiently exhausted from an exhaust duct 5 installed on a ceiling truss located above the pool (heat source). In the present invention, unlike the conventional system, the inertial force 9 due to ventilation and the buoyant force 10 are in the same direction, making the most effective use of the buoyant force 10 which is a natural phenomenon. Furthermore, the most distinctive feature of the present invention is that an upward air curtain is formed around the pool. The air curtain almost completely blocks radioactive contaminants in the air above the pool from spreading in the lateral direction, and they are efficiently removed by the exhaust duct 5 on the top of the pool.

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

FIG. 1 schematically shows the duct configuration and the principle of operation in a contaminated gas trapping device for a nuclear reactor building.

According to FIG. 1, the contaminated gas trapping device in the reactor building has the following configuration. An air supply duct 4 is installed on the floor of the outer periphery of the pool (heat source) 20 of the building, and ventilation air is blown out from the air supply port 11 by a blower 41. Also, the pool (heat source)
An exhaust duct 5 is installed above the exhaust port 12 .
The more contaminated gas 8 is sucked in by a suction device 42 in the ventilation device 40. At that time, the contaminated gas 8 is filtered by the filter 43. Note that the air supply duct 4 and exhaust duct 5 shown in the figure may be embedded in the wall of the building.

Details of the cross section of the embodiment shown in FIG. 1 are shown in FIG. 2, details of the A-A' cross section in FIG. 2 are shown in FIG. 3, and details of the B-B' cross section in FIG. As shown in the figure. In addition, Figure 5 shows the concentration distribution of pollutants in Figure 4 (area with a concentration of 5% or more when the concentration near the pool with the conventional ventilation method is 100%) and the airflow state, determined by numerical simulation. This is a summary of the results obtained.

According to FIGS. 2, 3, and 4, the apparatus for trapping contaminated gas inside a building according to the present invention has the following configuration. On the floor around the building pool,
Air supply ducts 4a and 4b are installed, and ventilation air is blown out from a plurality of openings in each duct using a blower. In addition, an exhaust duct 5 is installed on the ceiling truss 6.
a, 5b, 5c, 5d, and 5e are installed, and contaminated air is sucked in by a suction device through a plurality of openings.
These exhaust ducts 5c, 5d, 5e are connected to the truss beam 6.
It is placed in a position to avoid interference with the exhaust duct 5.
It continues to a and 5b. A duct that rises vertically downwards on the wall on the spent fuel pool side leads to the exhaust treatment equipment located on the lower floor of the building. Therefore, the ventilation air blown out from the ducts installed on the floor around the pool creates a forced upward airflow around the pool due to inertia.
It is sucked into the opening of an exhaust duct installed approximately 15 meters above the pool. As a result, an upward air curtain is formed around the pool. In addition, radioactive pollutants generated on the pool surface are efficiently sucked into the opening of the exhaust duct installed above the pool due to buoyancy, and after being filtered by the filter in the exhaust treatment equipment on the lower floor, It is released to the outside through the main exhaust stack.

According to FIG. 5, radioactive contaminants 8 generated by evaporation of pool water during periodic inspections are almost completely prevented from dispersing horizontally above the pool by the above-mentioned forced upward air curtain, and due to buoyancy. Because they are transported to the sky above the pool and efficiently exhausted there, the concentration distribution of pollutants (areas with a concentration of 5% or more when the concentration near the pool with conventional ventilation method is 100%) is very close to the sky above the pool. Limited.
This contaminant area is extremely small compared to the contaminant concentration distribution according to the conventional ventilation method shown in FIG. Figure 6 shows the relationship between the relative concentration of radioactive contaminants near the pool surface (concentration when the concentration near the pool with conventional ventilation method is taken as 100%) and the blowing speed at the opening of the supply air duct. This is what is shown. As a result of investigating the blowout speed in the range of 5m/s to 20m/s with the blowout air volume being the same as that of the conventional ventilation system, it was found that when the blowout speed was 5m/s (approximately the same as the blowout speed in the conventional ventilation method), the upward flow It can be seen that by forming a good air curtain, the concentration of pollutants near the pool surface is reduced to about half that of the conventional ventilation system. In other words,
The ventilation system of the present invention improves the pollutant collection rate by about twice as much as that of conventional ventilation systems.

Figure 7 shows the relative concentration of radioactive contaminants near the ceiling (concentration near the pool with conventional ventilation system).
This figure shows the relationship between the concentration (assumed to be 100%) and the blowing speed at the opening of the air supply duct.
As a result of investigating the blowout speed in the range of 5m/s to 20m/s with the same blowout air volume as the conventional type,
At a blowing speed of 5 m/s (approximately the same blowing speed as in the conventional ventilation method), due to the formation of a good upward air curtain, the concentration of pollutants near the ceiling surface is lower than the relative concentration of 16% in the conventional ventilation method. It decreases to about 1/4. In other words, the ventilation system of the present invention can reduce the amount of contaminants adhering to the ceiling surface to about 1/4 compared to the conventional ventilation system.

By the way, in order to properly form the upward air curtain used in this embodiment, it is necessary to consider the velocity distribution of the suction velocity at the opening of the exhaust duct 5. 8, 9, 10, and 11 all show cross-sectional views taken along line B-B' in FIG. This figure shows the concentration distribution and the influence on airflow conditions. FIG. 8 shows the airflow state in the room when the suction speed (5 m/s) is uniform and flatly distributed. As can be seen from the figure, a good upward air curtain was not formed. Additionally, it took more than 20 minutes to achieve steady airflow conditions. 9th
The figure shows the suction velocity distribution at the opening located above the air supply port in the exhaust duct (5 m/s), and the suction velocity at the opening located above the heat generating source (1.25 m/s). This shows the indoor airflow condition when the number is increased four times. As can be seen from the figure, a good upward air curtain is formed. Steady state at this time was achieved within 10 minutes after blowing out. Further, FIG. 10 shows the concentration of contaminants under the airflow state shown in FIG. 8. Contaminants (areas with a concentration of 5% or more when the concentration near the pool with conventional ventilation method is 100%) are spread throughout the building. 11th
The figure shows the concentration of contaminants under the airflow condition shown in FIG. 9. Contaminants are confined near the pool surface by the upward air curtain and are well distributed.

Figure 25 shows the case where the suction speed at the opening located above the air supply port in the exhaust duct is 5 m/s, and the ratio between this speed and the suction speed at the opening located above the heat generating source is changed. This shows the concentration near the indoor ceiling (concentration when the concentration near the pool with conventional ventilation system is taken as 100%). As can be seen from the figure, when the speed ratio is 4, the concentration is the lowest.

As a result of the above, when forming an upward air curtain, it is preferable that the suction speed at the opening of the exhaust duct 5 located above the air supply port is approximately four times the suction speed located above the heat generation source. desirable to obtain an upward air curtain.

FIG. 12 shows a sectional view of the exhaust duct 5 of FIG. 9. In the opening of the exhaust duct 5, no damper is provided at the opening located above the air supply port, but a damper 15 is provided at the inlet of the opening located above the heat generation source, as shown in the figure. This damper 15 makes it possible to make the flow resistance of the opening located above the air supply port smaller than that of the opening located above the heat generation source. The pumping speed at the opening located above the heat generating source can be made higher than the pumping speed at the opening located above the heat generating source.

FIG. 13 is a sectional view taken along the line BB in FIG. 2, showing a modification of the contaminant gas trapping device. In the air supply ducts 4c and 4d in the figure, the openings of the air supply ports are inclined at a certain angle from the vertical direction toward the center of the pool (heat source). In this case, ventilation air is blown diagonally upward from the opening of the air supply duct as shown in the figure. This method of ventilation narrows the distribution of contaminants above the pool (heat source). As a result, the length of the exhaust duct 5e installed on the ceiling truss located above the pool (heat source) can be shortened, and the efficiency of collecting pollutants can be further improved.

Similarly, FIG. 14 is a sectional view taken along line BB' in FIG. 2, showing a modification of the pollutant gas trapping device of the present invention. The air supply ducts 4e and 4f in the figure are configured to blow ventilation air downward from the duct openings. This ventilation further increases the rate of rise of the upward air curtain around the pool, as shown in the figure, and further helps block the spread of contaminants.

Furthermore, FIG. 26 shows a modification of the pollutant gas trapping device of the present invention, which is a sectional view taken along the line B-B' in FIG. The air supply ducts 4g and 4h in the figure have the function of supplying ventilation air. Contaminants are removed from exhaust ducts 5a and 5b installed above the pool.
and exhaust from 5e. In this modification, the fifth
Compared to the trapping device of the embodiment shown in the figure, the trapping efficiency performance is poor, but it can be applied when the amount of pollutants generated from the pool is relatively small.

FIG. 15 shows an example in which the polluted gas trapping device of the present invention is applied to a building containing casting equipment.
In this case, the casting 30 and the mold 31 become heat sources.
In this application example, outdoor air is blown upward by a blower 41 through an air supply duct 4 through an opening of an air supply port 11 installed on the outer periphery of a mold 31 which is a heat source. Contaminant gas 50 such as dust generated from the casting equipment is carried on this rising airflow, and is efficiently captured and sucked through the opening of the exhaust port 12 of the exhaust duct 5 located above the heat generation source. Further, the contaminated gas is exhausted to the outside by a suction device 42 through a filter 43 in the ventilation device 40. In this application example as well, by making the inertial force due to ventilation in the same direction as the buoyant force due to the heat source, it is possible to efficiently trap polluted gas generated from the vicinity of the heat source. By the way, the 15th
In the application example shown in the figure, the device was constructed by separating the air supply system and exhaust system using outdoor air, but the paper supply system and exhaust system are connected via a heat exchanger to circulate indoor air. It is also possible to configure a trapping device for contaminated gases.

According to this embodiment, as shown in FIGS. 5 to 14, an upward air curtain is created around the pool (heat source) in the reactor building to prevent contaminants from spreading into the work area. This technology improves the pollutant collection efficiency by more than double compared to conventional ventilation air conditioning equipment, reduces the amount of pollutants adhering to the ceiling to about 1/4, and further improves the efficiency of workers working in the work area. It has the effect of reducing the amount of radiation exposure to about 1/4. In addition, there are the following effects.

(1) Embedded ducts in conventional ventilation and air conditioning equipment are
Due to their thick plates, they account for most of the ductwork in the building. In the present invention, since there is no embedded duct, the amount of ducts in the entire reactor building is significantly reduced (about 20% reduction).

(2) There is no need for isolation valves, remote control switches, etc. associated with embedded ducts, resulting in improved rationalization of ventilation and air conditioning equipment.

(3) There is no need to adjust the interference with reinforcement, piping, etc. around the pool, greatly improving workability.

(4) In the current ventilation air conditioning equipment, mode switching was performed to change the exhaust air volume of each pool-embedded duct depending on the work being done in the pool, but this will no longer be necessary with the new system, so the control system will be significantly simplified. It becomes.

(5) Compared to the conventional buried duct system, maintenance and inspection efficiency is greatly improved.

〔Effect of the invention〕

According to the present invention, the air supply ports are arranged to surround the pool, which is the heat source, and the exit is arranged in the information about the pool, so that when radioactive pollutants are released from the pool, they can be distributed to the surrounding area. Dispersion can be limited and it can be captured efficiently. Therefore, contamination inside the building due to radioactive substances can be reduced, and radiation exposure of workers during maintenance inspections can be further reduced.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing a trapping device for contaminated gas in a building according to the present invention, Fig. 2 is a plan sectional view of Fig. 1, Fig. 3 is a sectional view taken along the line A-A' of Fig. 2, and Fig. 4 Figure, 5th
8 to 11, and 13 to 14 respectively correspond to the sectional views taken along line B-B' in FIG. 2, and FIG. A diagram showing the relationship between the relative concentration of radioactive contaminants near the pool surface and the blowing velocity at the opening of the supply air duct. A diagram showing the relationship with the blowing velocity at the opening, FIG. 12 is a sectional view showing an example of an exhaust duct, FIG. 15 is a system diagram showing another embodiment of the device of the present invention, and FIG. 16 is a conventional Plan of the reactor building showing ventilation and air conditioning equipment, Figures 17 and 1
Figure 8 is a sectional view taken along line E-E' in Figure 16, and Figure 1
9 and 20 are a sectional view taken along the line F-F' and a sectional view taken along the line G-G' of FIG. 16, and FIG. 21 is a sectional view taken along the line 17
The sectional views taken along line H-H' in the figure, Figures 22, 23, and 24 are Figures 5, 18, and 20, respectively.
Figure 25 is a diagram showing the relative concentration of pollutants near the ceiling surface, and Figure 26 is a diagram corresponding to Figure 2.
This figure corresponds to a sectional view taken along the line B' and shows yet another embodiment of the present invention. 1... Reactor well, 2... Dryer/separator equipment temporary storage pool, 3... Spent fuel storage pool, 4... Air supply duct, 5... Exhaust duct, 6...
... Ceiling truss, 7 ... Embedded duct, 8 ... Contaminated air, 9 ... Inertial force, 10 ... Buoyancy, 11 ... Air supply port, 12 ... Exhaust port, 15 ... Damper, 20 ...
...pool, 30...casting, 31...mold, 40...
...Ventilation device, 41...Blower, 42...Suction device, 43...Filter, 50...Contaminated gas such as dust.

Claims (1)

[Scope of Claims] 1. In a building having a pool in which an object containing a radioactive substance is placed underwater and the water temperature is higher than the space above, an air supply port is provided surrounding the pool to cause air to flow upward. , the air supply port is connected to a blower via an air supply duct, an exhaust port is provided above the pool for exhausting contaminated gas, and the exhaust port is connected to a suction device via an exhaust duct. A capture device inside the building. 2 In claim 1, the exhaust port is divided into a plurality of openings, and the flow resistance of the opening located above the air supply port is made smaller than the flow resistance of the opening located above the pool; A device for trapping polluted gas in a building, characterized in that the exhaust speed at an opening located above an air supply port is greater than the exhaust speed at an opening located above a pool. 3. The device for trapping polluted gas in a building according to claim 1, characterized in that the opening of the air supply port is inclined by a predetermined angle from the vertical direction toward the center of the pool.