JP6800833B2 - Oxygen concentration control equipment and oxygen concentration control method for buildings for nuclear power - Google Patents

Description

An embodiment of the present invention is an oxygen concentration control facility for a nuclear power building and a nuclear power building that realizes a fire protection function for a fire protection target device in a nuclear reactor facility or a facility related to nuclear power. Regarding the oxygen concentration control method.

For practical power reactors, in addition to the Fire Fighting Law and the Building Standards Law, in accordance with the new regulatory standards established by the Nuclear Regulatory Commission, the safety of reactor facilities should not be threatened by fire, and the reactor Equipment that has the functions of high temperature stop and cold stop, equipment that has the function of confining radioactive substances, and the emergency core cooling system pump room formed on the outside of the reactor containment vessel so that the cables will not lose their functions due to fire. In the valve room, emergency electrical equipment room, cable tray, etc., it is necessary to install local fire extinguishing equipment such as foam fire extinguishing device and local gas device, whole area fire extinguishing equipment such as whole area gas fire extinguishing device, and detector. Furthermore, although the inside of trenches in non-radiation controlled areas is generally not subject to fire extinguishing, it is necessary to install fire extinguishing equipment in trenches that accommodate cables with important functions in the event of an accident based on the new regulatory standards. There is.

As described above, in a practical power reactor, since there are many devices subject to fire protection and the range of protection is wide, the quantity of fire extinguishing equipment increases, and it is necessary to solve the problems of cost and arrangement feasibility. In addition, the installation of the above-mentioned digestive equipment and the like is a measure after a fire breaks out, and the fire itself cannot be prevented.

Further, Patent Document 1 discloses a technique for reducing an oxygen concentration by detecting an oxygen concentration in a building and supplying an inert gas into the building as a fire prevention measure in an unmanned warehouse or a factory. ing.

Japanese Unexamined Patent Publication No. 62-367

The above-mentioned Patent Document 1 is a technique of supplying an inert gas into an unmanned warehouse or a factory and keeping the internal pressure at a positive pressure from the external pressure (atmospheric pressure) in order to prevent the inflow of external oxygen. However, there are areas in the reactor facility where the internal pressure is controlled to be negative with respect to the external air pressure in order to prevent the diffusion of radioactive materials to the outside, such as the radiation control area in the secondary storage facility. .. Therefore, the technique of Patent Document 1 described above cannot be applied particularly in such a radiation controlled area.

The embodiment of the present invention has been made in consideration of the above circumstances, and is for nuclear power, which can surely prevent the occurrence of a fire in a fire protection target device in a building for nuclear power and can reduce the amount of fire extinguishing equipment. The purpose is to provide oxygen concentration control equipment and oxygen concentration control methods for buildings. Another object of the embodiment of the present invention is to provide an oxygen concentration control facility and an oxygen concentration control method for a building for nuclear power, which can surely prevent the diffusion of radioactive substances to the outside.

The oxygen concentration control facility of the building for nuclear power according to the embodiment of the present invention has a fire protection target area for accommodating the fire protection target device and a ventilation air conditioning system for ventilating the fire protection target area. Is connected to the fire protection target area and is provided with an air supply side switching damper and an air supply fan in order from the upstream side, and is connected to the fire protection target area and is connected to the exhaust fan and the exhaust side from the upstream side. A recirculation side switching damper is connected to an exhaust side duct provided with switching dampers in sequence, an upstream side of the exhaust side switching damper in the exhaust side duct, and a downstream side of the air supply side switching damper in the air supply side duct. A building for nuclear power, which is configured to have a recirculation side duct provided with an oxygen concentration meter for measuring the oxygen concentration in the fire protection target area, and a supply pipe to the air supply side duct. It has a nitrogen gas supply device that is connected via a duct to supply nitrogen gas, and a control device. The control device has an oxygen concentration measured by the oxygen concentration meter exceeding a set concentration at which a combustion phenomenon does not occur. At that time, the air supply side switching damper is fully closed, the recirculation side switching damper is fully opened, the exhaust side switching damper is adjusted to a predetermined opening degree, and the air supply fan and the exhaust fan are operated. It is characterized in that the nitrogen gas supply device is activated and the nitrogen gas from the nitrogen gas supply device is supplied to the fire protection target area.

The oxygen concentration control method for a building for nuclear power according to the embodiment of the present invention includes a fire protection target area for accommodating fire protection target equipment and a ventilation air conditioning system for ventilating the fire protection target area. Is connected to the fire protection target area and has an air supply side switching damper and an air supply fan in that order from the upstream side, and is connected to the fire protection target area and is connected to the exhaust fan and the exhaust side from the upstream side. A recirculation side switching damper is connected to an exhaust side duct gradually provided with a switching damper, an upstream side of the exhaust side switching damper in the exhaust side duct, and a downstream side of the air supply side switching damper in the air supply side duct. When the oxygen concentration in the fire protection target area exceeds the set concentration at which the combustion phenomenon does not occur in the building for nuclear power configured with the recirculation side duct provided with the above. The air side switching damper is fully closed, the recirculation side switching damper is fully opened, the exhaust side switching damper is adjusted to a predetermined opening degree, and the air supply fan, the exhaust fan, and the nitrogen gas supply device are operated. Is activated, and the nitrogen gas from the nitrogen gas supply device is supplied to the fire protection target area.

According to the embodiment of the present invention, it is possible to reliably prevent the occurrence of a fire in a fire protection target device in a building for nuclear power, and it is possible to reduce the amount of fire extinguishing equipment. In addition, the diffusion of radioactive substances to the outside can be reliably prevented.

The system diagram which shows the structure in the oxygen concentration control facility of the building for nuclear power which concerns on 1st Embodiment. The system diagram which shows the structure of the 1st nitrogen gas refining apparatus which is the nitrogen gas supply apparatus of FIG. (A) is a system diagram showing the configuration of the second nitrogen gas purification device which is the nitrogen gas supply device of FIG. 1, and (B) is a system showing the configuration of the third nitrogen gas purification device which is the nitrogen gas supply device of FIG. Figure. The flowchart which shows the procedure which the control device of FIG. 1 executes. The system diagram which shows the structure in the oxygen concentration control facility of the building for nuclear power which concerns on 2nd Embodiment. FIG. 5 is a flowchart showing a procedure executed by the control device of FIG. The system diagram which shows the structure in the oxygen concentration control facility of the building for nuclear power which concerns on 3rd Embodiment. The flowchart which shows the procedure which the control device of FIG. 7 executes. The system diagram which shows the structure in the oxygen concentration control facility of the building for nuclear power which concerns on 4th Embodiment. The flowchart which shows the procedure which the control device of FIG. 9 executes. The system diagram which shows the structure in the oxygen concentration control facility of the building for nuclear power which concerns on 5th Embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
[A] First Embodiment (FIGS. 1 to 4)
FIG. 1 is a system diagram showing a configuration in an oxygen concentration control facility of a building for nuclear power according to the first embodiment. Buildings for nuclear power, that is, nuclear reactor facilities such as nuclear power plants, or facilities related to nuclear power such as experimental reactors and fuel reprocessing facilities are provided with a fire protection target area 11 for accommodating fire protection target equipment 10. There is. Here, the fire protection target area 11 includes, for example, an emergency core cooling system pump room, a valve room, an emergency electrical component room, a cable tray, etc. formed on the outside of the reactor containment vessel in the reactor facility.

A ventilation air-conditioning system 12 for ventilating and air-conditioning the above-mentioned fire protection target area 11 is installed in a building for nuclear power (reactor facility or facility related to nuclear power). As shown in FIG. 1, the ventilation / air conditioning system 12 includes an air supply system 13A having an air supply side duct 13, an exhaust system 14A having an exhaust side duct 14, and a recirculation system having a recirculation side duct 15. It has a system 15A and. Reference numeral 16 indicates a building skeleton.

The air supply side duct 13 is connected to the fire protection target area 11. In the fire protection target area 11, the air supply side switching damper 17, the filter unit 18, the air volume adjusting dampers 19A and 19B, the air supply fans 20A and 20B, and the backflow prevention dampers 21A and 21B are sequentially arranged and supplied from the upstream side. The air system 13A is configured. The air volume adjusting damper 19A, air supply fan 20A and backflow prevention damper 21A connected in series, and the air volume adjusting damper 19B, air supply fan 20B and backflow prevention damper 21B connected in series are arranged in parallel with the air supply side duct 13. Has been done. When at least one of the air supply fans 20A and 20B of the air supply system 13A is activated, the fluid (mainly air) from which dust and the like have been removed by the filter unit 18 is supplied to the fire protection target area 11.

The exhaust side duct 14 is connected to the fire protection target area 11. The air volume adjusting dampers 22A and 22B, the exhaust fans 23A and 23B, the backflow prevention dampers 24A and 24B, and the exhaust side switching damper 25 are sequentially arranged in the exhaust side duct 14 from the upstream side to form the exhaust system 14A. The directly connected air volume adjusting damper 22A, exhaust fan 23A and backflow prevention damper 24A, and the directly connected air volume adjusting damper 22B, exhaust fan 23B and backflow prevention damper 24B are arranged in parallel with the exhaust duct 14. By activating at least one of the exhaust fans 23A and 23B of the exhaust system 14A, the fluid (mainly air) in the fire protection target area 11 is discharged to the outside of the building skeleton 16.

The recirculation side duct 15 is the upstream side of the exhaust side switching damper 25 in the exhaust side duct 14 (that is, between the backflow prevention dampers 24A and 24B and the exhaust side switching damper 25) and the air supply side in the air supply side duct 13. The downstream side of the switching damper 17 (that is, between the air supply side switching damper 17 and the filter unit 18) is connected. The recirculation side switching damper 26 and the air volume adjusting damper 27 are sequentially arranged in the recirculation side duct 15 from the upstream side to form the recirculation system 15A. The recirculation system 15A returns the fluid in the exhaust side duct 14 to the air supply side duct 13 to circulate the fluid.

The oxygen concentration control facility 30 of the building for nuclear power in the second embodiment utilizes the above-mentioned ventilation and air conditioning system 12 to exert a fire prevention function on the fire protection target device 10 in the fire protection target area 11. It is configured to include an oxygen concentration meter 31, a nitrogen gas supply device 32, and a control device 33.

The oxygen concentration meter 31 is installed in the fire protection target area 11 and measures the oxygen concentration A1 in the fire protection target area 11. This measured value is transmitted to the control device 33.

The nitrogen gas supply device 32 is connected to the downstream side of the backflow prevention dampers 21A and 21B in the air supply side duct 13 (that is, between the backflow prevention dampers 21A and 21B and the fire protection target area 11) via the supply pipe 34. Then, nitrogen gas is supplied to the fire protection target area 11. A check valve 35 is provided in the supply pipe 34 to prevent backflow of fluid from the fire protection target area 11 to the nitrogen gas supply device 32. Specifically, the nitrogen gas supply device 32 includes a first nitrogen gas refining device 36 shown in FIG. 2, a second nitrogen gas refining device 37 shown in FIG. 3 (A), and a third nitrogen gas shown in FIG. 3 (B). Purification device 38 and the like.

As shown in FIG. 2, the first nitrogen gas purification device 36 purifies nitrogen gas by evaporating liquid nitrogen, and is a liquid nitrogen storage tank 39, an evaporator 40, a storage tank 41, a heater 42, and a safety valve. It is composed of 43 and a pressure regulating valve 44.

Liquid nitrogen is stored in the liquid nitrogen storage tank 39. The evaporator 40 is connected to a liquid nitrogen storage tank 39, and the liquid nitrogen in the liquid nitrogen storage tank 39 is evaporated (vaporized) to purify nitrogen gas. The storage tank 41 is connected to the evaporator 40 and temporarily stores the nitrogen gas purified by the evaporator 40. The heater 42 is connected to the storage tank 41 and heats the purified nitrogen gas. The safety valve 43 is installed in a pipe 45 that connects the storage tank 41 and the heater 42, and opens when the pressure in the pipe 45 exceeds a predetermined value. The pressure adjusting valve 44 is arranged in the pipe 45 and adjusts the pressure of the nitrogen gas guided to the air supply side duct 13 of the ventilation air conditioning system 12 (FIG. 1).

As shown in FIG. 3A, the second nitrogen gas refining apparatus 37 purifies nitrogen gas by adsorbing oxygen in the air to an adsorbent and removing it. The air compressor 46 and the activated carbon tank It includes 47, a suction tank 48, a storage tank 49, and a pressure regulating valve 50.

The air compressor 46 compresses the raw material air. The activated carbon tank 47 is connected to an air compressor 46 to adsorb impurities (for example, oil) in the air as a raw material. A plurality of (for example, two) adsorption tanks 48 are connected in parallel to the activated carbon tank 47, and oxygen is adsorbed and removed by the adsorbent to purify nitrogen gas. As the adsorbent, for example, molecular sieve charcoal that adsorbs oxygen molecules using coconut husk as a raw material is preferable. The storage tank 49 is connected to the adsorption layer 48 and temporarily stores the purified nitrogen gas. The pressure adjusting valve 50 is arranged in a pipe 51 connecting the storage tank 49 and the air supply side duct 13 of the ventilation air conditioning system 12 (FIG. 1), and adjusts the pressure of the nitrogen gas guided to the exhaust side duct 13. Reference numeral 52 in FIG. 3A indicates a stop valve.

As shown in FIG. 3B, the third nitrogen gas purification apparatus 38 purifies nitrogen gas by separating nitrogen and oxygen in the air by a polymer hollow fiber membrane 55, and is an air compressor 53. , The activated carbon tank 54, the polymer hollow fiber membrane 55, a storage tank 56, and a pressure regulating valve 57.

The air compressor 53 compresses the raw material air. The activated carbon tank 54 is connected to the air compressor 53 and adsorbs impurities (for example, oil) in the air of the raw material. The polymer hollow fiber membrane 55 is connected to an activated carbon tank 54 and permeates oxygen molecules to separate oxygen and nitrogen to purify nitrogen gas. The storage tank 56 is connected to the polymer hollow fiber membrane 55 and temporarily stores the purified nitrogen gas. The pressure adjusting valve 57 is arranged in a pipe 58 connecting the storage tank 56 and the air supply side duct 13 of the ventilation air conditioning system 12 (FIG. 1), and adjusts the pressure of nitrogen gas guided to the air supply side duct 13.

The control device 33 shown in FIG. 1 includes an oxygen concentration meter 31, an air supply side switching damper 17, an exhaust side switching damper 25, a recirculation side switching damper 26, air supply fans 20A and 20B, exhaust fans 23A and 23B, and nitrogen gas. It is electrically connected to the feeder 32. Then, the control device 33 compares the oxygen concentration A1 in the fire protection target area 11 measured by the oxygen concentration meter 31 with the set concentration A0, and as shown in the flowchart of FIG. 4, the air supply side switching damper. 17. Controls the exhaust side switching damper 25, the recirculation side switching damper 26, the air supply fan 20A or 20B, the exhaust fan 23A or 23B, and the nitrogen gas supply device 32.

Here, the set concentration A0 is an oxygen concentration at which a combustion phenomenon does not occur, and for example, a value of 12.5% oxygen concentration set in an inert gas fire extinguishing device for a computer room, a communication machine room, or the like is used. ..

As shown in FIG. 4, the control device 33 acquires the oxygen concentration A1 in the fire protection target area 11 from the oxygen concentration meter 31 (S11), and determines whether or not the oxygen concentration A1 exceeds the set concentration A0. (S12). When the oxygen concentration A1 in the fire protection target area 11 is equal to or less than the set concentration A0, the nitrogen gas supply (injection) from the nitrogen gas supply device 32 into the fire protection target area 11 is not performed (S13).

In step S12, when the oxygen concentration A1 in the fire protection target area 11 exceeds the set concentration A0, the control device 33 fully closes the air supply side switching damper 17 and fully opens the recirculation side switching damper 26. Operate to adjust the exhaust side switching damper 25 to a predetermined opening degree (for example, a minute opening degree). (S14). At this time, the control device 33 further activates the air supply fan 20A or 20B, activates the exhaust fan 23A or 23B, and activates the nitrogen gas supply device 32 (S15). By these operations, the nitrogen gas from the nitrogen gas supply device 32 circulates through the recirculation side duct 15 and is continuously supplied and injected into the fire protection target area 11 (S16). At this time, a part of the nitrogen-containing air in the fire protection target area 11 is discharged to the outside of the building skeleton 16 through the exhaust side switching damper 25.

After that, the control device 33 determines whether or not the oxygen concentration A1 in the fire protection target area 11 has become the set concentration A0 or less (S17), and if the oxygen concentration A1 still exceeds the set concentration A0, the control device 33 determines. The supply (injection) of nitrogen gas to the fire protection target area 11 by the nitrogen gas supply device 32 is continued (S18).

In step S17, when the oxygen concentration A1 in the fire protection target area 11 becomes equal to or less than the set concentration A0, the control device 33 opens the exhaust side switching damper 25 according to the type of the control area of the fire protection target area 11. Is changed (S19).

That is, when the fire protection target area 11 is a radiation control area, the control device 33 keeps the exhaust side switching damper 25 at a predetermined opening degree (for example, a minute opening degree). As a result, the nitrogen gas from the nitrogen gas supply device 32 is supplied to the fire protection target area 11, and a part of the nitrogen-containing air in the fire protection target area 11 passes through the exhaust side switching damper 25 to the building. It is discharged to the outside of the skeleton 16 and the inside of the fire protection target area 11 becomes a negative pressure state lower than the atmospheric pressure. When the fire protection target area 11 is a non-radiation control area, the control device 33 fully closes the exhaust side switching damper 25 and supplies nitrogen gas from the nitrogen gas supply device 32 to the fire protection target area. The inside of 11 is set to a positive pressure state higher than the atmospheric pressure.

Since it is configured as described above, according to the first embodiment, the following effects (1) to (7) are obtained.
(1) When the oxygen concentration A1 in the fire protection target area 11 exceeds the set concentration A0 at which the combustion phenomenon does not occur, the control device 33 fully closes the air supply side switching damper 17 to recirculate the side. Fully open the switching damper 26, adjust the exhaust side switching damper 25 to a predetermined opening (for example, a minute opening), start the air supply fan 20A or 20B, start the exhaust fan 23A or 23B, and nitrogen gas. The supply device 32 is activated to supply the nitrogen gas from the nitrogen gas supply device 32 to the fire protection target area 11. By supplying the nitrogen gas from the nitrogen gas supply device 32 to the fire protection target area 11 in this way, the oxygen concentration in the fire protection target area 11 decreases to the above set concentration A0 or less, so that the fire protection target area It is possible to reliably prevent the occurrence of a fire with respect to the fire protection target device 10 in the fire protection target area 11, and therefore, it is possible to reduce the amount of fire extinguishing equipment in the fire protection target area 11.

(2) Since the nitrogen gas from the nitrogen gas supply device 32 is supplied to the fire protection target area 11 by using the existing ventilation and air conditioning system 12 of the building for nuclear power (reactor facility or facility related to nuclear power). The number of newly installed fire extinguishing equipment can be reduced, and therefore, the quantity of fire extinguishing equipment can be reduced from this viewpoint as well, and the cost and arrangement space can be reduced.

(3) When the nitrogen gas is supplied from the nitrogen gas supply device 32, the exhaust side switching damper 25 is adjusted to a predetermined opening degree (for example, a minute opening degree), so that the air containing nitrogen in the fire protection target area 11 A part of the gas is discharged to the outside of the building frame 16 through the exhaust side switching damper 25, and the inside of the fire protection target area 11 becomes a negative pressure state lower than the atmospheric pressure. Therefore, when the fire protection target area 11 is a radiation control area, it is possible to reliably prevent radioactive substances from diffusing from the fire protection target area 11 to the outside.

(4) When the oxygen concentration A1 in the fire protection target area 11 becomes equal to or lower than the set concentration A0, and when the fire protection target area 11 is a non-radiation control area, the air supply side switching damper 17 and the exhaust side The switching damper 25 is fully closed, the recirculation side switching damper 26 is fully opened, the air supply fan 20A or 20B is started, the exhaust fan 23A or 23B is started, and the nitrogen gas supply device 32 is started. As a result, nitrogen gas is supplied from the nitrogen gas supply device 32 to the fire protection target area 11, and the inside of the fire protection target area 11 becomes a positive pressure state higher than the atmospheric pressure. As a result, the inflow of oxygen from the outside into the fire protection target area 11 is prevented, and the fire occurrence prevention effect on the fire protection target device 10 in the fire protection target area 11 can be further improved.

(5) By supplying the nitrogen gas from the nitrogen gas supply device 32 into the fire protection target area 11, the oxygen concentration A1 in the fire protection target area 11 becomes the set concentration A0 or less. As a result, the fire protection target area 11 becomes an atmosphere in which it is difficult for people to carry out activities due to dizziness, nausea, etc., so that it is possible to prevent terrorists from invading and malicious operations on equipment.

(6) When the nitrogen gas supply device 32 is composed of the first nitrogen gas purification device 36, the nitrogen gas supply device 32 can supply a large amount of high-purity nitrogen gas at one time. Therefore, the oxygen concentration A1 in the fire protection target area 11 can be shifted to a low oxygen concentration state of the set concentration A0 or less in a short time.

(7) When the nitrogen gas supply device 32 is composed of the second nitrogen gas purification device 37 or the third nitrogen gas purification device 38, the nitrogen gas supply device 32 purifies nitrogen gas using air as a raw material. , Nitrogen gas can be continuously supplied to the fire protection target area 11.

[B] Second embodiment (FIGS. 5 and 6)
FIG. 5 is a system diagram showing the configuration of the oxygen concentration control facility of the building for nuclear power according to the second embodiment. In this second embodiment, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The difference between the oxygen concentration control facility 60 of the nuclear structure in the second embodiment and the first embodiment is that the oxygen concentration meter 31 that detects the oxygen concentration in the fire protection target area 11 (in the second embodiment, this). The oxygen concentration meter 31 is referred to as a first oxygen concentration meter 61), and a second oxygen concentration meter 62 for measuring the oxygen concentration on the downstream side of the exhaust side switching damper 25 in the exhaust side duct 14 is provided in the exhaust side duct 14. Air volume adjustment damper 22A, exhaust fan 23A and backflow prevention damper 24A, and air volume adjustment damper 22B, exhaust fan 23B and backflow prevention damper 23B, air volume adjustment damper 22C, small air volume exhaust fan 63 and backflow prevention damper 24C is further arranged in parallel with the exhaust side duct 14, and the control device 64 supplies the oxygen gas from the nitrogen gas supply device 32 to the fire protection target area 11 in a state where the exhaust side switching damper 25 is fully opened. It is a point configured as such.

The second oxygen concentration meter 62 is installed on the downstream side of the exhaust side switching damper 25 in the exhaust side duct 14. The oxygen concentration A2 on the downstream side of the exhaust side switching damper 25 in the exhaust side duct 14 measured by the second oxygen concentration meter 62 is transmitted to the control device 64. Further, the air volume adjusting damper 22C, the small air volume exhaust fan 63, and the backflow prevention damper 24 are connected in series. Of these, the small air volume exhaust fan 63 is provided in the exhaust side duct 14 as described above, and has a smaller air volume than the exhaust fans 23A and 23B.

As shown in FIG. 6, the control device 64 learns the oxygen concentration A1 in the fire protection target area 11 from the first oxygen concentration meter 61 (S21), and whether or not the oxygen concentration A1 exceeds the set concentration A0. Is determined (S22). When the oxygen concentration A1 in the fire protection target area 11 is equal to or less than the set concentration A0, the control device 64 does not supply (inject) nitrogen gas from the nitrogen gas supply device 32 into the fire protection target area 11 (S23). ).

In step S22, when the oxygen concentration A1 in the fire protection target area 11 exceeds the set concentration A0, the control device 64 fully closes the air supply side switching damper 17 and the recirculation side switching damper 26 to exhaust the air. The side switching damper 25 is fully opened to activate the small air volume exhaust fan 63 and activate the nitrogen gas supply device 32 (S24). By these operations, the nitrogen gas from the nitrogen gas supply device 32 is supplied and injected into the fire protection target area 11 (S25). At the same time, the air in the fire protection target area 11 is quickly pushed out of the building skeleton 16 through the exhaust side switching damper 25 in the fully open state.

After that, the control device 64 learns the oxygen concentration A2 on the downstream side of the exhaust side switching damper 25 in the exhaust side duct 14 from the second oxygen concentration meter 62 (S26), and whether or not the oxygen concentration A2 is equal to or less than the set concentration A0. Is determined (S27). When the oxygen concentration A2 on the downstream side of the exhaust side switching damper 25 in the exhaust side duct 14 exceeds the set concentration A0, the nitrogen gas supply (injection) from the nitrogen gas supply device 32 into the fire protection target area 11 is continued. (S28).

When the oxygen concentration A2 becomes equal to or less than the set concentration A0 in step S27, the control device 64 changes the opening degree of the exhaust side switching damper 25 according to the type of the controlled area of the fire protection target area 11 (S29). That is, the control device 64 adjusts the exhaust side switching damper 25 to a predetermined opening degree (for example, a minute opening degree) when the fire protection target area 11 is a radiation control area, and the fire protection target area 11 is a non-radiation control area. In this case, the exhaust side switching damper 25 is fully closed.

Further, the control device 64 holds the air supply side switching damper 17 in the fully closed state, operates the recirculation side switching damper 26 in the fully open state, holds the nitrogen gas supply device 32 in the activated state, and holds the air supply fan 20A or 20B. Is activated, and the exhaust fan 23A or 23B is activated (S30). After that, the control device 64 stops the small air volume exhaust fan 63 (S31).

In steps S29 to S31, when the fire protection target area 11 is a radiation control area, the exhaust side switching damper 25 is adjusted to a predetermined opening degree (for example, a minute opening degree) from the nitrogen gas supply device 32. Nitrogen gas is continuously supplied to the fire protection target area 11, and a part of the air containing the nitrogen gas in the fire protection target area 11 is discharged to the outside of the building frame 16 through the exhaust side switching damper 25. As a result, the area 11 subject to fire protection is in a negative pressure state lower than the atmospheric pressure.

Further, in steps S29 to S31, when the fire protection target area 11 is a non-radiation control area, the exhaust side switching damper 25 is fully closed to protect the nitrogen gas from the nitrogen gas supply device 32 from fire. By continuously supplying the gas to the target area 11, the inside of the fire protection target area 11 becomes a positive pressure state higher than the atmospheric pressure.

Based on the above configuration, according to the second embodiment, the effects (2), (5), (6) and (7) of the first embodiment are obtained, and the following effects are obtained. The effects (8) to (10) are achieved.

(8) When the oxygen concentration A1 in the fire protection target area 11 exceeds the set concentration A0 at which the combustion phenomenon does not occur, the control device 64 fully closes the air supply side switching damper 17 and the recirculation side switching damper 26. The exhaust side switching damper 25 is fully opened to activate the small air volume exhaust fan 63 and the nitrogen gas supply device 32 to supply the nitrogen gas from the nitrogen gas supply device 32 to the fire protection target area 11. As a result, nitrogen gas from the nitrogen gas supply device 32 is supplied into the fire protection target area 11, and the air in the fire protection target area 11 is rapidly discharged. Therefore, the oxygen concentration A1 in the fire protection target area 11 Can be rapidly reduced to the set concentration A0 or less. As a result, it is possible to reliably prevent the occurrence of a fire with respect to the fire protection target device 10 in the fire protection target area 11, and therefore, it is possible to reduce the amount of fire extinguishing equipment in the fire protection target area 11.

(9) Exhaust side switching in the exhaust side duct 14 When the oxygen concentration A2 on the downstream side of the damper 25 is equal to or less than the set concentration A0 and the fire protection target area 11 is a non-radiation controlled area, the exhaust side is switched. The damper 25 is fully closed together with the air supply side switching damper 17, the recirculation side switching damper 26 is fully opened, the air supply fan 20A or 20B is started, the exhaust fan 23A or 23B is started, and the nitrogen gas supply device 32. Is started. As a result, nitrogen gas is supplied to the fire protection target area 11, and the inside of the fire protection target area 11 becomes a positive pressure state higher than the atmospheric pressure. As a result, the inflow of oxygen from the outside into the fire protection target area 11 is prevented, and the fire occurrence prevention effect on the fire protection target device 11 in the fire protection target area 11 can be further improved.

(10) When the oxygen concentration A2 on the downstream side of the exhaust side switching damper 25 in the exhaust side duct 14 becomes equal to or less than the set concentration A0 and the fire protection target area 11 is a radiation control area, the air supply side is switched. The damper 17 is fully closed, the exhaust side switching damper 25 is adjusted to a predetermined opening (for example, a minute opening), the recirculation side switching damper 26 is fully opened, the air supply fan 20A or 20B is started, and the exhaust is exhausted. The fan 23A or 23B is activated, and the nitrogen gas supply device 32 is activated. As a result, nitrogen gas is supplied to the fire protection target area 11, and the inside of the fire protection target area 11 becomes a negative pressure state lower than the atmospheric pressure. As a result, it is possible to reliably prevent radioactive substances from diffusing to the outside from the fire protection target area 11.

[C] Third Embodiment (FIGS. 7 and 8)
FIG. 7 is a system diagram showing the configuration of the oxygen concentration control facility of the building for nuclear power according to the third embodiment. In the third embodiment, the same parts as those in the first embodiment are designated by the same reference numerals as those in the first embodiment to simplify or omit the description.

The difference between the oxygen concentration control facility 70 of the building for nuclear power in the third embodiment from the first embodiment is that the control device 74 is when the oxygen concentration A1 in the fire protection target area 11 becomes the set concentration A0 or less. However, instead of the nitrogen gas supply device 32, the nitrogen gas is supplied to the fire protection target area 11 from a small-capacity replenishment nitrogen gas supply device 71 having a smaller nitrogen gas supply amount than the nitrogen gas supply device 32. This is the point.

The supply pipe 34 that connects the nitrogen gas supply device 32 to the air supply side duct 13 is connected to the supply nitrogen gas supply device 71 via the connection pipe 72 on the upstream side of the check valve 35, and the connection pipe 72. A check valve 73 is arranged in the air. The supplementary nitrogen gas supply device 71 and the stop valve 73 are electrically connected to the control device 74 and are controlled by the control device 74. The control device 74 executes the same control as the control device 33 of the first embodiment, and also executes the control shown in FIG.

That is, the control device 74 acquires the oxygen concentration A1 in the fire protection target area 11 from the oxygen concentration meter 31 (S41), and determines whether or not the oxygen concentration A1 is equal to or lower than the set concentration A0 (S42). If the oxygen concentration A1 in the fire protection target area 11 still exceeds the set concentration A0, the control device 74 continues to supply (inject) nitrogen gas to the fire protection target area 11 by the nitrogen gas supply device 32. (S43).

In step S42, when the oxygen concentration A1 in the fire protection target area 11 becomes equal to or less than the set concentration A0, the control device 74 stops the nitrogen gas supply device 32 (S44) and causes the replenishment nitrogen gas supply device 71 to be turned on. It is activated and the stop valve 73 is opened (S45). As a result, instead of the nitrogen gas supply device 32, a small-capacity replenishment nitrogen gas supply device 71 supplies nitrogen gas having a smaller supply amount than the nitrogen gas supply device 32 into the fire protection target area 11 via the stop valve 73. The oxygen concentration in the fire protection target area 11 is maintained at the set concentration A0 or less.

When the steps S44 and S45 are executed, as shown in step S14 of FIG. 4, the air supply side switching damper 17 is fully closed and the recirculation side switching damper 27 is fully opened. Further, as shown in step S15, the air supply fan 20A or 20B is in the activated state, and the exhaust fan 23A or 23B is also in the activated state. Further, as shown in step S19, the exhaust side switching damper 25 is adjusted to a predetermined opening degree (for example, a minute opening degree) when the fire protection target area 11 is a radiation control area, and is a fire protection target. When the area 11 is a non-radiation controlled area, it is fully closed.

Further, as shown in FIG. 3, the replenishment nitrogen gas supply device 71 purifies the nitrogen gas by adsorbing oxygen in the air with the adsorbent of the adsorption tank 48 and removing the second nitrogen gas purification device 37. Alternatively, it is a third nitrogen gas purification device 38 that purifies nitrogen gas by separating nitrogen and oxygen in the air with a polymer hollow thread film 55. The replenishment nitrogen gas supply device 71 is composed of the second nitrogen gas purification device 37 or the third nitrogen gas purification device 38, so that the replenishment nitrogen gas supply device 71 continuously supplies nitrogen gas from the air as a raw material. It will be possible to supply.

Since it is configured as described above, according to the third embodiment, in addition to the same effects as the effects (1) to (7) of the first embodiment, the following effects (11) and (12) Play.

(11) When the oxygen concentration A1 in the fire protection target area 11 becomes the set concentration A0 or less, the nitrogen gas is supplied from the small-capacity replenishment nitrogen gas supply device 71 having a smaller nitrogen gas supply amount than the nitrogen gas supply device 32. Is continuously supplied to the fire protection target area 11. Therefore, the oxygen concentration A1 in the fire protection target area 11 can be maintained in a low oxygen concentration state of the set concentration A0 or less, and the cost can be reduced by reducing the amount of nitrogen gas supplied to the fire protection target area 11.

(12) The replenishment nitrogen gas supply device 71 is configured to be connected to a supply pipe 34 for connecting the nitrogen gas supply device 32 to the air supply side duct 13 via a connection pipe 72. Therefore, the piping space for connecting the replenishment nitrogen gas supply device 71 to the air supply side duct 13 can be reduced, and the piping configuration of the replenishment nitrogen gas supply device 71 can be simplified.

[D] Fourth Embodiment (FIGS. 9 and 10)
FIG. 9 is a system diagram showing the configuration of the oxygen concentration control facility of the building for nuclear power according to the fourth embodiment. In this fourth embodiment, the same parts as those in the first and third embodiments are designated by the same reference numerals as those in the first and third embodiments to simplify or omit the description.

The oxygen concentration control equipment 80 of the building for nuclear power in the fourth embodiment is different from the first embodiment in that the air supply side switching damper 17, the exhaust side switching damper 25, the recirculation side switching damper 26, and the air supply fan 20A. And 20B, and the exhaust fans 23A and 23B, etc. are controlled to change the fire protection target area 11 in the low oxygen concentration state of the set concentration A0 or less to a state where people can enter, and the fire protection target area 11 The equipment necessary for people to enter the area is newly installed in the fire protection target area 11.

That is, the indicator light 81, the detector 82, and the fire extinguishing equipment 83 are installed in the fire protection target area 11 as the equipment necessary for a person to enter the fire protection target area 11. The indicator light 81 is lit in an oxygen concentration state where a person can enter. For example, the indicator light 81 is lit when the oxygen concentration in the fire protection target area 11 becomes 18% or more, and the inside of the fire protection target area 11 is lit. Notify that it is now accessible to people. Further, the detector 82 detects the occurrence of a fire in the fire protection target area 11.

The control device 84 executes the same control as the control device 33 of the first embodiment, and also executes the control shown in FIG. 10 in order to make the inside of the fire protection target area 11 accessible to humans. That is, for example, the control device 84 inputs a signal indicating that a person enters, that is, an outside air introduction signal, by operating the manually operable switch 85 (FIG. 9) (S51).

The control device 84 stops the operating nitrogen gas supply device 32 or the supplementary nitrogen gas supply device 71 by inputting the outside air introduction signal (S52). After executing step S52, the control device 84 fully opens the air supply side switching damper 17 and the exhaust side switching damper 25, and fully closes the recirculation side switching damper 26 (S53).

Next, the control device 84 activates the air supply fan 20A or 20B, activates the exhaust fan 23A or 23B (S54), and allows the outside air (air) outside the building skeleton 16 to pass through the air supply side duct 13 for fire protection. It is introduced into the area 11, and the air containing nitrogen gas in the fire protection target area 11 is discharged to the outside of the building skeleton 16 through the exhaust side duct 14. As a result, the inside of the fire protection target area 11 becomes an oxygen concentration state (for example, 18% or more) that can be accessed by a person, and the state is notified by lighting the indicator lamp 81.

Since it is configured as described above, the fourth embodiment also has the same effects (1) to (7), (11) and (12) as those of the first and third embodiments, and also has the following effects. The effects (13) to (15) are achieved.

(13) The equipment for changing the inside of the fire protection target area 11 to a state where people can enter is the existing ventilation air conditioning system 12 in the building for nuclear power (that is, the nuclear reactor facility or the facility related to nuclear power). Since it is configured by using it, no new equipment is required, and the cost and placement space can be reduced.

(14) In the fire protection target area 11, an indicator lamp 81 that lights up in an oxygen concentration state that allows people to enter is installed. Therefore, by checking the lighting state of the indicator lamp 81, it is possible to prevent a person from accidentally entering the fire protection target area 11 in the low oxygen concentration state.

(15) In addition to the fire extinguishing equipment 83, a detector 82 capable of detecting a fire is installed in the fire protection target area 11. Therefore, even if the oxygen concentration in the fire protection target area 11 is changed to an oxygen concentration that allows people to enter and a fire occurs, this fire is detected early by the detector 82 and the fire extinguishing equipment 83. The fire can be extinguished using.

[E] Fifth Embodiment (FIG. 11)
FIG. 11 is a system diagram showing the configuration of the oxygen concentration control facility of the building for nuclear power according to the fifth embodiment. In this fifth embodiment, the same parts as those in the first and third embodiments are designated by the same reference numerals as those in the first and third embodiments to simplify or omit the description.

The difference between the oxygen concentration control facility 90 of the building for nuclear power in the fifth embodiment from that of the first embodiment is that the system is boosted or inactive in the building for nuclear power (that is, the nuclear facility or the facility related to nuclear power). The point is that the nitrogen gas can be supplied from the nitrogen gas supply device 32 or the supply nitrogen gas supply device 71 to the nitrogen request system 91 that requires the supply of nitrogen in operation due to the conversion or the like.

That is, the nitrogen request system 91 is connected to the supply pipe 34 for connecting the nitrogen gas supply device 32 to the air supply side duct 13 via the supply pipe 92 on the downstream side of the check valve 35, and this transmission is performed. A check valve 93 is provided in the supply pipe 92. The stop valve 93 is electrically connected to the control device 94 and is controlled by the control device 94. The control device 94 executes the same control as the control device 33 of the first embodiment, and also controls the stop valve 93 as follows.

That is, the control device 94 inputs a signal that nitrogen should be supplied to the nitrogen request system 91 by operating, for example, a manually operable switch 95 when the nitrogen gas supply device 32 or the supply nitrogen gas supply device 71 is operating. At that time, the stop valve 93 is opened. As a result, excess nitrogen gas is supplied to the nitrogen request system 91 from the nitrogen gas supply device 32 or the supplementary nitrogen gas supply device 71.

Since it is configured as described above, the fifth embodiment also has the same effects (1) to (7), (11) and (12) as those of the first and third embodiments, and also has the following effects. It produces the effect (16).

(16) By supplying the nitrogen purified by the nitrogen gas supply device 32 or the supply nitrogen gas supply device 71 to the nitrogen request system 91, a new facility for supplying nitrogen to the nitrogen request system 91 is provided. There is no need to build, thus reducing cost and placement space.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention, and their replacements and changes can be made. Is included in the scope and gist of the invention, and is also included in the invention described in the claims and the equivalent scope thereof.

For example, also in the second embodiment, as shown by the two-point chain line in FIG. 5, when the oxygen concentration A1 in the fire protection target area 11 becomes equal to or less than the set concentration A0, or the exhaust side switching damper in the exhaust side duct 14 When the oxygen concentration A2 on the downstream side of 25 becomes equal to or less than the set concentration A0, the area subject to fire protection is replaced with the nitrogen gas supply device 32 and has a smaller capacity than the nitrogen gas supply device 32 for replenishment. Nitrogen gas may be supplied to 11.

10 ... Fire protection target equipment, 11 ... Fire protection target area, 12 ... Ventilation and air conditioning system, 13 ... Air supply side duct, 14 ... Exhaust side duct, 15 ... Recirculation side duct, 17 ... Air supply side switching damper, 20A, 20B ... Air supply fan, 23A, 23B ... Exhaust fan, 25 ... Exhaust side switching damper, 26 ... Recirculation side switching damper, 30 ... Oxygen concentration control equipment, 31 ... Oxygen concentration meter, 32 ... Nitrogen gas supply device, 33 ... Control device, 34 ... Supply pipe, 36 ... 1st nitrogen gas purification device, 37 ... 2nd nitrogen gas purification device, 38 ... 3rd nitrogen gas purification device, 39 ... Liquid nitrogen storage tank, 40 ... Evaporator, 46 ... Air Compressor, 48 ... adsorption tank, 53 ... air compressor, 55 ... polymer hollow thread film, 60 ... oxygen concentration control equipment, 61 ... first oxygen concentration meter, 62 ... second oxygen concentration meter, 63 ... small air volume exhaust Fan, 64 ... Control device, 70 ... Oxygen concentration control equipment, 71 ... Nitrogen gas supply device for replenishment, 74 ... Control device, 80 ... Oxygen concentration control equipment, 81 ... Indicator light, 82 ... Sensor, 83 ... Digestion equipment, 84 ... Control device, 90 ... Oxygen concentration control equipment, 91 ... Nitrogen requirement system, 94 ... Control device, A0 ... Set concentration, A1 ... Oxygen concentration in the fire protection target area, A2 ... Oxygen concentration in the exhaust side duct.

Claims (14)

It has a fire protection target area for accommodating fire protection target equipment and a ventilation and air conditioning system for ventilating this fire protection target area.
The ventilation and air conditioning system includes an air supply side duct that is connected to the fire protection target area and is sequentially provided with an air supply side switching damper and an air supply fan from the upstream side.
An exhaust side duct connected to the fire protection target area and sequentially equipped with an exhaust fan and an exhaust side switching damper from the upstream side,
There is a recirculation side duct provided with a recirculation side switching damper by connecting the upstream side of the exhaust side switching damper in the exhaust side duct and the downstream side of the air supply side switching damper in the air supply side duct. It is a building for nuclear power that was constructed in
An oxygen concentration meter that measures the oxygen concentration in the area subject to fire protection,
A nitrogen gas supply device that is connected to the air supply side duct via a supply pipe to supply nitrogen gas,
It has a control device, and when the oxygen concentration measured by the oxygen concentration meter exceeds the set concentration at which the combustion phenomenon does not occur, the control device fully closes the air supply side switching damper. The recirculation side switching damper is fully opened, the exhaust side switching damper is adjusted to a predetermined opening degree, the air supply fan, the exhaust fan and the nitrogen gas supply device are started, and the nitrogen gas supply device is used. An oxygen concentration control facility for a building for nuclear power, which is configured to supply the nitrogen gas of the above to the fire protection target area. It has a fire protection target area for accommodating fire protection target equipment and a ventilation and air conditioning system for ventilating this fire protection target area.
The ventilation and air conditioning system includes an air supply side duct that is connected to the fire protection target area and is sequentially provided with an air supply side switching damper and an air supply fan from the upstream side.
An exhaust side duct connected to the fire protection target area and sequentially equipped with an exhaust fan and an exhaust side switching damper from the upstream side,
There is a recirculation side duct provided with a recirculation side switching damper by connecting the upstream side of the exhaust side switching damper in the exhaust side duct and the downstream side of the air supply side switching damper in the air supply side duct. It is a building for nuclear power that was constructed in
A first oxygen concentration meter that measures the oxygen concentration in the fire protection target area,
A second oxygen concentration meter that measures the oxygen concentration in the exhaust side duct,
A small air volume exhaust fan provided in the exhaust side duct and having a smaller air volume than the exhaust fan,
A nitrogen gas supply device that is connected to the air supply side duct via a supply pipe to supply nitrogen gas,
It has a control device, and this control device includes the air supply side switching damper and the recirculation when the oxygen concentration measured by the first oxygen concentration meter exceeds a set concentration at which a combustion phenomenon does not occur. The side switching damper is fully closed, the exhaust side switching damper is fully opened, the small air volume exhaust fan and the nitrogen gas supply device are activated, and the oxygen gas from the nitrogen gas supply device is discharged to the fire protection target area. When the oxygen concentration measured by the second oxygen concentration meter becomes equal to or less than the set concentration, the air supply side switching damper is held in the fully closed state, and the recirculation side switching damper is supplied. Is fully opened, the nitrogen gas supply device is held in the activated state, the air supply fan and the exhaust fan are started to stop the small air volume exhaust fan, and the exhaust side switching damper is subject to the fire protection. When the area is a radiation controlled area, it is adjusted to a predetermined opening, and when the fire protection target area is a non-radiation controlled area, it is fully closed to continue supplying oxygen gas to the fire protection target area. Oxygen concentration control facility for nuclear buildings, which is characterized by being constructed. When the oxygen concentration in the fire protection target area measured by the oxygen concentration meter becomes equal to or less than the set concentration, the control device sets a predetermined exhaust side switching damper when the fire protection target area is a radiation control area. The building for nuclear power according to claim 1, wherein the building is maintained at an opening degree, and when the fire protection target area is a non-radiation controlled area, the exhaust side switching damper is controlled to be fully closed. Oxygen concentration control equipment. A supply nitrogen gas supply device having a capacity smaller than that of the nitrogen gas supply device is connected to the supply pipe connecting the nitrogen gas supply device to the air supply side duct.
When the oxygen concentration in the fire protection target area becomes equal to or lower than a predetermined concentration, the control device replaces the nitrogen gas supply device with a nitrogen gas supply amount smaller than that of the nitrogen gas supply device. The oxygen concentration control facility for a building for nuclear power according to any one of claims 1 to 3, wherein nitrogen gas is supplied from a supply device to the area subject to fire protection. In the area subject to fire protection, a digestive system, a detector capable of detecting a fire, and an indicator light that lights up in an oxygen concentration state accessible to humans are installed.
When the control device inputs a signal indicating that a person enters the fire protection target area, the nitrogen gas supply device or the supply nitrogen gas supply device is stopped, and the air supply side switching damper and the exhaust side switching damper are fully opened. Claims 1 to 4 are configured to operate, fully close the recirculation side switching damper, activate the air supply fan and the exhaust fan, and supply air to the fire protection target area. Oxygen concentration control equipment for nuclear buildings according to any one of the items. A nitrogen request system that requires the supply of nitrogen for the operation of a building for nuclear power is connected to the supply pipe that connects the nitrogen gas supply device to the air supply side duct.
When the control device inputs a signal to supply nitrogen to the nitrogen request system, the control device supplies excess nitrogen gas to the nitrogen request system from the nitrogen gas supply device or the supplementary nitrogen gas supply device. The oxygen concentration control facility for a building for nuclear power according to any one of claims 1 to 5, characterized in that it is configured. The nitrogen gas supply device is a device that purifies nitrogen gas by evaporating liquid nitrogen, a device that purifies nitrogen gas by adsorbing oxygen in the air to an adsorbent and removing it, or nitrogen and oxygen in the air. The oxygen concentration control facility for a building for nuclear power according to any one of claims 1 to 6, wherein the apparatus is an apparatus for purifying nitrogen gas by separating the gas with a polymer hollow thread film. The replenishment nitrogen gas supply device is a device for purifying nitrogen gas by adsorbing oxygen in the air to an adsorbent and removing it, or a device for separating nitrogen and oxygen in the air by a polymer hollow thread film to obtain nitrogen. The oxygen concentration control facility for a building for nuclear power according to any one of claims 4 to 6, which is an apparatus for purifying gas. It has a fire protection target area for accommodating fire protection target equipment and a ventilation and air conditioning system for ventilating this fire protection target area.
The ventilation and air conditioning system includes an air supply side duct that is connected to the fire protection target area and is sequentially provided with an air supply side switching damper and an air supply fan from the upstream side.
An exhaust side duct connected to the fire protection target area and sequentially equipped with an exhaust fan and an exhaust side switching damper from the upstream side,
There is a recirculation side duct provided with a recirculation side switching damper by connecting the upstream side of the exhaust side switching damper in the exhaust side duct and the downstream side of the air supply side switching damper in the air supply side duct. It is a building for nuclear power that was constructed in
When the oxygen concentration in the fire protection target area exceeds the set concentration at which the combustion phenomenon does not occur, the air supply side switching damper is fully closed, the recirculation side switching damper is fully opened, and the exhaust side is exhausted. The switching damper is adjusted to a predetermined opening degree to activate the air supply fan, the exhaust fan, and the nitrogen gas supply device, and supply the nitrogen gas from the nitrogen gas supply device to the fire protection target area. A characteristic oxygen concentration control method for buildings for nuclear power. It has a fire protection target area for accommodating fire protection target equipment and a ventilation and air conditioning system for ventilating this fire protection target area.
The ventilation and air conditioning system includes an air supply side duct that is connected to the fire protection target area and is sequentially provided with an air supply side switching damper and an air supply fan from the upstream side.
An exhaust side duct connected to the fire protection target area and sequentially equipped with an exhaust fan and an exhaust side switching damper from the upstream side,
There is a recirculation side duct provided with a recirculation side switching damper by connecting the upstream side of the exhaust side switching damper in the exhaust side duct and the downstream side of the air supply side switching damper in the air supply side duct. It is a building for nuclear power that was constructed in
When the oxygen concentration in the fire protection target area exceeds the set concentration at which the combustion phenomenon does not occur, the air supply side switching damper and the recirculation side switching damper are fully closed to fully open the exhaust side switching damper. By operating, the small air volume exhaust fan and the nitrogen gas supply device are activated to supply the nitrogen gas from the nitrogen gas supply device to the fire protection target area, and the oxygen concentration in the exhaust side duct is the said. When the concentration falls below the set concentration, the air supply side switching damper is held in the fully closed state, the recirculation side switching damper is fully opened, the nitrogen gas supply device is held in the activated state, and the air supply fan is operated. And the exhaust fan is started to stop the small air volume exhaust fan, and the exhaust side switching damper is adjusted to a predetermined opening degree when the fire protection target area is a radiation control area, and the fire protection target area is adjusted. A method for controlling the oxygen concentration of a building for nuclear power, which comprises performing a fully closed operation to continue supplying nitrogen gas to the area subject to fire protection when is a non-radiation controlled area. When the oxygen concentration in the fire protection target area becomes equal to or lower than the set concentration, if the fire protection target area is a radiation control area, the exhaust side switching damper is held at a predetermined opening degree, and the fire protection target area is maintained. The oxygen concentration control method for a building for nuclear power according to claim 9, wherein when is a non-radiation controlled area, the exhaust side switching damper is fully closed. When the oxygen concentration in the area subject to fire protection falls below a predetermined concentration, instead of the nitrogen gas supply device, a small-capacity replenishment nitrogen gas supply device having a smaller nitrogen gas supply amount than this nitrogen gas supply device The method for controlling the oxygen concentration of a building for nuclear power according to any one of claims 9 to 11, wherein nitrogen gas is supplied to the area subject to fire protection. When a person enters the area subject to fire protection, the nitrogen gas supply device or the supply nitrogen gas supply device is stopped, the air supply side switching damper and the exhaust side switching damper are fully opened, and the recirculation side switching damper is fully opened. The oxygen concentration of the building for nuclear power according to any one of claims 9 to 12, wherein the air supply fan and the exhaust fan are activated by the closing operation to supply air to the fire protection target area. Management method. When nitrogen should be supplied to the nitrogen-requiring system that requires the supply of nitrogen for the operation of the building for nuclear power, excess nitrogen gas is supplied to the nitrogen-requiring system from the nitrogen gas supply device or the supply nitrogen gas supply device. The method for controlling the oxygen concentration of a building for nuclear power according to any one of claims 9 to 13, characterized in that.

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