JPH0576599B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a device (hereinafter abbreviated as FCS) for controlling the concentration of combustible gas in a nuclear reactor containment vessel, and particularly relates to a device for controlling the concentration of combustible gas in a nuclear reactor containment vessel. This invention relates to a portable combustible gas concentration control device that can be transported and used in a plant where an accident has occurred.

[Background of the invention]

FCS is used in the event of a loss of coolant accident in a nuclear reactor (hereinafter referred to as
The flammable gases (hydrogen and oxygen) generated in the reactor containment vessel are set at the flammable limit concentration (abbreviated as LOCA).
This device controls the concentration of combustible gases by actively burning them before they reach 4Vol% and oxygen 5Vol%.

The mechanism by which combustible gas is generated is the generation of hydrogen due to the water-metal reaction that occurs when the fuel rods are exposed and heated up during LOCA, and the generation of hydrogen and oxygen due to the radiolysis of water by fission products.

Conventionally, as countermeasures against the generation of hydrogen due to water-metal reactions, the inside of the containment vessel is replaced with inert gas (nitrogen gas) in advance to suppress the oxygen concentration, and hydrogen and oxygen generated by radiolysis of water are replaced in advance. The common method of dealing with the occurrence of this problem was to use FCS.

Figures 6 and 7 show conventional FCS.
Usually two units are installed in one plant. The system includes a blower 1, a heater 2, a recombiner 3, a cooler 4, a steam separator 5, a main pipe 6, a recirculation pipe 7, an inlet flow control valve 8, a recirculation flow control valve 9, and a recirculation flow control valve. It consists of 10. The function is as follows: A blower 1 sucks in combustible gas from a dry well 11, a heater 2 heats it to about 720°C, and the gas is guided to a recombiner 3. Hydrogen and oxygen are recombined in the recombiner 3, and the generated water vapor is returned to water in the cooler 4. The steam/water separator 5 has the function of separating water and unburned gas, and branching a portion of the separated gas to a recirculation pipe 7 and returning it to the suction pipe. The recirculation pipe 7 is a facility for preventing excessive recombination and damage to the system when the concentration of flammable gas in the dry well increases due to a major rupture accident or the like. Water and unburned gas leaving the steam/water separator 5 are transferred from the residual heat removal system to the cooler 4.
It returns to the suppression chamber 12 along with the spray cooling water supplied for cooling. In the suppression chamber 12, when the pressure increases due to the return gas from the FCS, the vacuum breaker 13 opens and gas flows into the dry well 11 to maintain the pressure balance. The suction gas flow rate is controlled to be constant by automatic control of the inlet flow control valve 9 and the recirculation flow control valve 10. Furthermore, the temperature of the outlet gas of the recombiner 3 is also controlled by the automatic controller.

To operate this system, first, the containment vessel isolation valves 14 and 15 are opened within 30 minutes after the accident, and then the heater 2 is turned on to start warming up. Since the recombiner 3 reaches a predetermined temperature within three hours after the start of warm-up, the flow rate is set to the normal operating state and the recombiner 3 enters the operating state.

Regarding the radiolysis of water, the generation of hydrogen and oxygen due to the radiolysis of water does not continue until the fission products finish decaying, and when the hydrogen concentration in the gas phase increases to a certain extent, water in still water (non-boiling water) It has become clear that the amount of hydrogen and oxygen generated by decomposition and the amount of hydrogen and oxygen reduced by recombination reach an equilibrium state, and water decomposition essentially stops progressing any further. Therefore, hydrogen due to radiolysis of water,
The idea that FCS that deals with oxygen generation is not necessary has become commonplace, and a recent plant rationalization proposal to eliminate FCS has been proposed and is about to be implemented.

However, even in this case, the idea is not to delete all of them to ensure a safety margin, but to place at least one unit in the nuclear power plant and transport it to the accident plant in the event of an accident, in order to deal with the worst case scenario. is becoming solidified. If you try to achieve this by simply making the conventional FCS portable,
Traditionally, FCS was designed with the assumption that it would be installed in each plant, so power supplies, cooling systems, etc. had to be supplied from the plant, and it was difficult to install these equipment in each plant. Even if FCS is removed, its effects are not fully utilized, and there is an urgent need to resolve this drawback.

[Purpose of the invention]

An object of the present invention is to provide a portable combustible gas concentration control device in which the FCS itself has all the functions necessary to operate the FCS and is integrated with a transport vehicle.

[Summary of the invention]

The present invention provides an upstream main pipe that can be freely connected to a dry well in a reactor containment vessel via a pipe joint, a blower that applies a driving force to the fluid that has passed through the main pipe, and a blower that provides a driving force to the fluid that has passed through the main pipe. A heater that heats the passing fluid using the exhaust heat of the transport vehicle, a recombiner that recombines the heated fluid, and a closed recirculation system that cools the fluid discharged from the recombiner. a cooling facility; a steam and water separator that separates the fluid that has passed through the cooling facility into steam and water; and a passage that supplies the fluid that has passed through the steam and water separator to a suppression chamber in the reactor containment vessel. A device for controlling the concentration of combustible gas in a reactor containment vessel, comprising the suppression chamber and a downstream main pipe connectable via another pipe joint; This is a portable combustible gas concentration control device in which the transport vehicle is equipped with a power supply system to the device for controlling the concentration of combustible gas.

[Embodiments of the invention]

A specific embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

In the embodiment of the present invention, the main system includes a blower 1, a heater 2, a recombiner 3, a cooler 4, a steam separator 5, a main pipe 6, and a main pipe joint 27.
These are the same as conventional FCS and have the same functions.

The embodiment of the present invention is structurally characterized by the heater 2, cooler 4, piping joint 27, power supply system, and transport vehicle, and these will be described in detail below.

(a) Heater The heater 2 uses exhaust gas led from the engine of the transport vehicle through the exhaust pipe 23 as a heat source. That is, in the heater 2, the recombiner 3 is surrounded by a spiral pipe 16, and the atmospheric gas in the dry well 11 passes through the spiral pipe 16 so that the gas receives the heat generated by the recombination. It's getting easier. This spiral piping 16 has a double piping structure as shown in FIG. The structure allows for heat exchange.

This system also includes a bypass pipe 17 that guides the exhaust gas directly to the outlet exhaust pipe 23 without passing it through the spiral pipe 16 in order to adjust the temperature of the heater 2, a bypass flow control valve 18 that adjusts the bypass flow rate, and a bypass flow control valve 18 that controls the bypass flow rate. A heater thermometer 19 is provided which sends a signal to the valve 18.

The inlet temperature of the recombiner 3 requires heating to about 720°C. The temperature of the exhaust gas immediately after the engine of a typical car today is approximately 800°C. Therefore, it is possible to maintain the temperature of the exhaust gas in the spiral pipe 16 at 720° C. or higher by wrapping a heat insulating material around the exhaust pipe 23 to prevent heating.

In addition, when the FCS is operated at its rated heat capacity,
As for whether the amount of heat required to heat up to 720°C can be supplied from the exhaust gas, it was found that it is fully possible as shown below.

Calorie balance under the condition that the power source is a generator that supplies the necessary power for the FCS.

The required power excluding the FCS heater is approximately 50kw/h
(In the present invention, the heat source of the heater uses car exhaust gas.) Therefore, the required output P of the engine required to generate this is P = 50 × 10 ³ × 1.36 × 10 ^-3 (PS/ w) = 68PS Considering this, the generator, and other efficiencies, the engine is
Suppose you are driving at 100PS.

Further, if the fuel consumption rate of the engine is 200g/PS·h, the fuel consumption rate W per hour of a 100PS engine is W=0.2×100=20Kg/h.

The calorific value of gasoline is approximately 10,000 kcal/Kg, so an engine with a 100 PS output generates 10,000 x 20 = 2 x 10 ⁵ kcal/h per hour. Of this, approximately 35% is dissipated as exhaust gas, so 2 x 10 ⁵ x 0.35 = 70,000 kcal/h.

On the other hand, the flow rate when the FCS is operating at its rated value is 250.
m ³ /h, this flow rate is 700℃ (20℃ → 720℃
°C) The amount of heat required to heat the gas is the specific heat of the gas.
Assuming 0.25kcal/Kg and density 1.2Kg/m ³ (20℃ air), Q=250×1.2×0.25×700=50000kcal/h.

Therefore, if the engine is operating at 100PS, the engine's exhaust gas will generate enough heat to heat the flow rate of the FCS operating at rated operation to 720℃, which is necessary for the recombination reaction. It can be seen that it has

In fact, once the FCS starts its rated operation, the reaction heat from the recombiner 3 can also be used as a heat source for the heater 2, so the engine output as described above is not required.

(b) Cooler The cooling equipment, the main component of which is the cooler 4, has a closed circulation system configuration consisting of the cooler 4, radiator 20, fan 21, pump 22, and exhaust equipment. In order to cool the high-temperature steam that entered the cooler 4 from the recombiner 3 and return it to water, the high-temperature gas fluid that entered the cooler 4 from the recombiner 3 is cooled again and is sent to the suppression chamber at a low temperature. It is provided to reduce the temperature condition of the flow path piping from the recombiner 3 to the suppression chamber. With this cooling equipment, it is possible to cool the fluid after the recombination process without supplying cooling water from the outside. That is,
The water sprayed into the cooler 4 is transferred to the radiator 20
The water is then cooled and sprayed again into the cooler 4 by the pump 22. The capacity of the radiator 20 is such that it can dissipate approximately 50,000 kcal/h of heat required to lower the temperature from the outlet of the recombiner 4 to approximately 770°C to the temperature returned to the suppression chamber 12 of 120°C. There is a need.

(c) Piping joint Since the present invention is portable, the dry well 11
The connecting portion of the piping 6 for taking suction from the pump and returning it to the suppression chamber 12 must have a joint structure. Since the FCS forms the PCV boundary, it is necessary to be very careful about leakage, but during the period when it is necessary to activate the FCS in the event of an accident, the pressure inside the PCV has returned to almost atmospheric pressure.
A bolted structure using a flange is sufficient for the piping joint. Also, the joint part 27 of the pipe 6
By making a part of the front part (see FIG. 1) a flexible tube, it is possible to create a structure in which the joint can be easily connected.

(d) Power System A power system for driving the blower 1, valves 9, 18, fan 21, pump 22, etc. is supplied from a generator 25 driven by the engine 24 of the transport vehicle. The required power excluding the power for FCS heater 2 is approximately
Since it is 50kw/h, the engine output that drives it is 68PS, and even considering the efficiency of the generator 25 and drive gear 26, the engine output is
100PS is enough. A 100PS engine is the average output of a general passenger car, so there is no need to make the engine particularly large. The generator 25 is driven by switching from the traveling gear of the transport vehicle to the generator driving gear. Therefore, some modification of the transmission is required.

(e) Transport vehicle The transport vehicle has an engine of 100 PS or more, and
A medium-sized truck (4 to 4.5 tons) is appropriate because it needs to be large enough to carry the FCS and generator. The transport vehicle is equipped with a beam arm to stabilize the vehicle body, similar to a crane truck. This beam arm is used to stabilize the vehicle during operation. Further, the exhaust pipe 23 of the transport vehicle has an exhaust port 27 having a joint structure, and is connected to the exhaust port opening of the building during operation, so that the exhaust gas is discharged outdoors. Note that the exhaust pipe 23 is partially flexible and has a structure that allows easy connection at the joint.

Next, the operation and function of the FCS in this embodiment of the present invention will be explained in detail.

When the FCS according to the embodiment of the present invention described above is installed in an accident plant, the installation site requires a large space that can be accessed by a transport vehicle.
Alternatively, the entrance for carrying large items could be considered. At the FCS installation site, piping leading to the containment vessel dry well 11 and piping leading to the suppression chamber 12 are opened, and the suction piping and return piping of the FCS of the present invention carried in are connected to the piping. In addition, exhaust gas is guided to the outside of the building by connecting the exhaust pipe 23 of the transport vehicle to an exhaust port opened to the outside. Once the FCS is in place, the beam arm is taken out and the transport vehicle is secured to prevent it from moving. Next, the suction part and the outlet part of the main pipe 6 of the FCS are connected with the pipe joint 27, and the isolation valve 14,
Open 15. Furthermore, the transmission of the transport vehicle is converted into a generator 2.
The engine 2 of the transport vehicle is switched to the drive gear 26 of 5.
4 to start generating electricity and warming up the heater 2. Therefore, at this point, blower 1, cooling water pump 2
2 starts. Heater 2 reaches the specified temperature (approximately 720℃)
When the flow rate is reached, the bypass flow rate control valve 18 is controlled to start normal operation.

According to the embodiments of the present invention described above, the conventional
Compared to the case where FCS is simply made portable, the following unique effects can be achieved.

(1) Rationalization of plant design When simply transporting a conventional FCS to the accident plant, it is necessary to prepare power supply equipment and cooling equipment for each plant, but with the FCS according to the present invention, all the functions required by the FCS are provided by the FCS itself. Since the FCS has power supply equipment and cooling equipment for each plant, it is not necessary to install it in each plant, and the cost of the entire site can be reduced significantly. Furthermore, since no power source is required for the FCS, it is possible to reduce the capacity of the on-site power source such as an emergency diesel generator.

(2) Simplification of preparation work for operation In the present invention, since the cooling water of the cooler 4 is of a closed recirculation type, there is no need to supply cooling water from the outside, and therefore there is no need to connect cooling water piping. This simplifies installation work.

(3) Improved safety In the present invention, since the cooling water of the cooler 4 is of a closed recirculation type, there is no connection of piping for supplying cooling water from the outside. Therefore, there is no leakage of cooling water from the connection, improving safety (cooling water is directly connected to the PCV).
Since it comes into contact with the atmosphere, it may contain radioactivity. ).

(4) Improved maintainability In the portable FCS of the present invention, which is separated from the reactor building and on standby, the FCS itself is equipped with power supply equipment and cooling system equipment, so these equipment can be used regardless of the plant operating status. , system maintenance becomes possible.

(5) Improved operability In the present invention, the power supply equipment and cooling system equipment are owned by the FCS itself, so in the event of an accident, the usage status of the on-site power supply and the operating mode status of the RHR system (reactor residual heat removal system) (conventional
If the FCS is simply brought in, it will be supplied with cooling water from the RHR system, but it will be possible to operate the FCS at will, improving operability.

FIGS. 8 to 13 show modified examples of the present invention. In each figure, parts given the same reference numerals as in FIGS. 1 to 7 indicate the same or corresponding parts. These will be explained below.

In the embodiment shown in FIGS. 8 and 9, a tube heat exchange method is used instead of a spray method in which the cooling water of the cooler 4 is brought into direct contact with the atmosphere of the containment vessel. In other words, the cooler 4 shell side (or tube side)
In this structure, the unburned gas discharged from the recombiner 3 is circulated through cooling water to the tube side (or shell side) for heat exchange.

According to this embodiment, since the cooling water does not come into direct contact with the containment vessel atmosphere, the cooling water can be circulated in a clean state free of fission products. Therefore, even if cooling water were to leak out of the system from, for example, a seal portion of the pump 22, there is no possibility of contaminating the surrounding area.

In the embodiment shown in FIGS. 10 and 11, the cooler 4
This is the case when is air cooled. The cooler 4 consists of a plurality of tubes 28, each tube having a fin. The gas exiting the recombiner 4 is cooled by cold air blown from the fan 21 while passing through each tube 28 . In this embodiment, since the only dynamic device is the fan 21, the structure is simple, and since no cooling water or the like that may leak outside the system is used, safety is extremely high.

In the embodiment shown in FIGS. 12 and 13, the power source for driving the blower 1, pump 22, fan 21, etc. is supplied from the on-site power source without loading a generator 25 driven by the engine 24 of the transport vehicle. This is what I did. In this case, a power cable 29 is provided in the FCS main body, and is connected to an in-house power outlet to receive power. According to this embodiment, a dedicated generator driven by the engine of the transport vehicle and a mechanism for driving the generator are not required, and the structure of the transport vehicle is simplified, thereby facilitating maintenance and inspection.

As described above, FIGS. 1 to 5 of the present invention
In each of the embodiments shown in Figures 8 to 11, the FCS itself has the functions required by the FCS, which eliminates the need for power supply equipment and cooling system equipment for the FCS in each plant, reducing the cost of the entire site. is drastically reduced.

Additionally, since no power source is required for the FCS, it is also possible to reduce the capacity of the on-site power source such as an emergency diesel generator.

In all the embodiments of the present invention, the cooling water of the cooler 4 is in a closed recirculation system, so there is no need to supply cooling water from the outside, eliminating the need for piping connection work, and simplifying the installation work. .

In addition, in all the embodiments of the present invention, the cooling water of the cooler 4 is of a closed recirculation type, so there is no piping connection for supplying cooling water from the outside.
Therefore, there is no leakage of cooling water from the connection part, and safety is improved.

In all of the embodiments of the present invention, the portable FCS is separated from the reactor building to prepare for an accident. Maintenance is possible.

Further, FIGS. 1 to 5 and 8 to 1 of the present invention
In each example shown in Figure 1, the power supply equipment and cooling equipment are FCS.
Since you own your own power supply, you can check the usage status of the on-site power supply in the event of an accident.
Regardless of the operation mode status of the RHR system (if conventional FCS was simply brought in, cooling water would be supplied from the RHR system), and in all embodiments of the present invention, the operation mode of the RHR system It becomes possible to operate the FCS arbitrarily regardless of the situation, improving drivability.

〔Effect of the invention〕

According to the present invention, there is provided a portable combustible gas concentration control device that is integrated with a transport vehicle and reduces the dependence of functions necessary for operating an FCS (combustible gas concentration control device) on external devices. can. Therefore,
By simply installing one device of the present invention in a power plant, it is possible to deal with any accident that occurs in any plant, and the cost of installing a combustible gas concentration control device in one power plant can be significantly reduced compared to the conventional method.

[Brief explanation of the drawing]

Figures 1 to 5 are diagrams showing one embodiment of the device of the present invention, Figures 1 and 2 are system diagrams, Figure 3 is an explanatory diagram explaining the structure of the main part, and Figure 4 is a reproduction diagram. 5 is a diagram explaining the overall structure, FIG. 6 is a system diagram of the conventional device, FIG. 7 is a diagram explaining the structure of the main part of FIG. 6, FIG. FIG. 9 is a system diagram showing the second embodiment of the present invention, FIG.
Figure 1 is a system diagram showing the third embodiment of the present invention;
13 are system diagrams showing a fourth embodiment of the present invention. 1... Blower, 2... Heater, 3... Recombiner, 4... Cooler, 5... Steam water separator, 6... Main piping, 7... Recirculation piping, 8... Cooling water stop valve, 9
... Inlet flow control valve, 10 ... Recirculation flow control valve, 11 ... Drywell, 12 ... Suppression chamber, 13 ... Vacuum breaker, 1
4... Isolation valve (suction side), 15... Isolation valve (discharge side), 16... Spiral double piping, 17... Exhaust gas bypass pipe, 18... Bypass flow rate control valve,
19...Thermometer, 20...Radiator, 21...
Fan, 22...Pump, 23...Exhaust pipe, 24
... Engine, 25 ... Generator, 26 ... Generator drive gear, 27 ... Piping joint, 28 ... Cooler tube, 29 ... External power supply cable.

Claims (1)

[Scope of Claims] 1. An upstream main pipe that can be freely connected to a dry well in the reactor containment vessel via a pipe joint, a blower that applies driving force to the fluid that has passed through the main pipe, and the main pipe. A heater that heats the fluid that has passed through the piping using the exhaust heat of the transport vehicle, a recombiner that recombines the heated fluid, and a closed recirculation that cools the fluid discharged from the recombiner. a steam and water separator that separates the fluid that has passed through the cooling equipment into steam and water, and supplies the fluid that has passed through the steam and water separator to a suppression chamber in the reactor containment vessel. A device for controlling the concentration of combustible gas in a reactor containment vessel, comprising a main pipe on the downstream side that can be freely connected to the suppression chamber through another pipe joint as a passage for controlling the suppression chamber, and the reactor containment vessel. A portable combustible gas concentration control device, wherein the transport vehicle is equipped with a power supply system to the device for controlling the concentration of flammable gas in the container. 2. In claim 1, the portable combustible device is characterized in that the power supply equipment connected to the power supply system is a generator that is driven by the engine of a transport vehicle and is equipped on the transport vehicle. Sexual gas concentration control device. 3. In claim 1 or 2, the cooling of the cooling equipment is performed by air cooling consisting of a plurality of tubes with fins for passing the fluid to be cooled and a fan that blows air into the tubes. A portable combustible gas concentration control device characterized by: