JPH05164892A - Inflammable gas control device for nuclear reactor - Google Patents

Abstract

PURPOSE:To make up a device of static units, and thereby enable the device to be surely operated at the time of accidents by filling the inside of a container the opening of which is formed due to an increase in temperature, pressure and the like, with a hydrogen absorbing alloy and inert gas. CONSTITUTION:A plural number of inflammable gas control devices 13 is arranged within an atomic reactor housing container while being dispersed. Each control device 13 is made up of a container 25, a hydrogen absorbing alloy 26 which is filled in the container, and of inert gas 21, and the specific quantity of hydrogen is absorbed and stored in the alloy 26 in advance. When an accident happens to the atomic reactor, temperature, pressure and the like within the atomic reactor housing container are abruptly and progressively increased. A cap 23 is damaged because inner gas 27 is expanded as temperature is increased. The alloy 26 is emitted outside from an opening, and the temperature of the alloy 26 is increased because of combustible reaction of hydrogen which has been absorbed and stored. This situation thereby allows the particles of the alloy 26 to be of ignition sources for hydrogen emitted out of a reactor core and the like, so that the combustible reaction of hydrogen and oxygen in the environment is accelerated. This situation consequently results in an explosion phenomenon due to accumulated hydrogen, thereby preventing the atomic reactor housing container from being damaged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustible gas control device for a nuclear reactor for processing a large amount of combustible gas such as hydrogen gas and oxygen discharged into a reactor containment vessel containing a nuclear reactor. ..

[0002]

2. Description of the Related Art As a device for treating a large amount of hydrogen gas released in a nuclear reactor, for example, in an accident, into a reactor containment vessel for storing a nuclear reactor, a combustible fuel used in a boiling water nuclear power plant is used. Generally, a volatile gas concentration control device and an igniter used in a pressurized water nuclear power plant in the United States are known.

The combustible gas concentration control system is described in the document "Boiling water nuclear power plant combustible gas concentration control system TL.
R-002-A ”and the like. Its basic configuration is, as shown in FIG. 5, a blower 1, a heater 2, a recombiner 3,
The cooler 4 and the steam separator 5 are connected in series, and are composed of a plurality of valves 7, 8 and 9 and a pipe 10 connecting them.

The operation of this device requires cooling water and electric power supplied from the outside. Reference numeral 11 in the figure is a bypass pipe. Further, the reactor containment vessel 12 is filled with an inert gas during the operation of the reactor, and the oxygen concentration is maintained in a diluted state (3.5 to 4.0% or less).

If a nuclear reactor accident occurs, hydrogen is released into the reactor containment vessel 12 due to the oxidation reaction of the fuel cladding, and hydrogen and oxygen are released due to the radiolysis of water. The newly released hydrogen and oxygen are sucked by the blower 1 and introduced into the apparatus together with a mixed gas of oxygen and nitrogen which is present in the reactor containment vessel 12 in advance.

The gas introduced into the apparatus is heated to a predetermined temperature by the heater 2 and then sent to the recombiner 3 where it is converted into water by the recombination reaction of hydrogen and oxygen. Will be returned. Then, it is sent to the cooler 4, the gas is cooled, the steam is returned to water, and after passing through the steam separator 5, it is returned to the reactor containment vessel 12.

In this way, hydrogen and oxygen are treated so that the concentrations of hydrogen and oxygen in the reactor containment vessel 12 do not exceed the flammability limits of 4% hydrogen concentration and 5% oxygen concentration at the same time. Maintained at. As a result, it is possible to prevent the explosion due to the rapid and extensive combustion of hydrogen and oxygen, and the integrity of the containment vessel is maintained.

The igniter is based on the document "NUREG / CR-2486 Fi
nal Results of the Hydrogen Igniter Experimental P
rogram ”etc., the reactor containment vessel 12
Hydrogen gas generated in the reactor containment vessel 12 is generated by arranging a number of ignition plugs etc. It is used as an ignition source for the above, and is a system in which hydrogen gas is directly burned in the reactor containment vessel 12 for processing.

In this system, the reactor containment vessel 12 is generally in an air atmosphere, and oxygen existing before the accident reacts with a large amount of hydrogen released in a wide range and rapidly. A large explosion occurs, and by gradually burning and processing the hydrogen so that the reactor containment vessel 12 is not damaged by it, it is possible to prevent the hydrogen concentration from increasing in a wide range. It is a thing.

[0010]

All of the conventional methods require a relatively large amount of electric power for heating, and the combustible gas concentration control device has cooling water in addition to a rotating device called a blower. Up to need. Therefore, in order to exert a predetermined function when necessary, it is necessary to use a utility such as electric power, and for example, it is necessary to perform a periodic operation test approximately every 3 months in preparation for an accident.

On the other hand, in the next generation of nuclear power development, the introduction of static equipment into the safety system is becoming the world trend, and the flammability of a nuclear reactor composed of static equipment that does not require external utility It is desired to provide a volatile gas control device.

The present invention has been made to solve the above problems, and provides a combustible gas control device for a nuclear reactor, which is composed of static equipment that does not require utilities such as an external heater, blower and power supply device. The purpose is to do.

[0013]

SUMMARY OF THE INVENTION According to the present invention, an opening is formed in a part of the reactor containment vessel by using any one of an ambient temperature, a pressure, a relative humidity and a radiation level or a combination thereof as an operating force. It is characterized in that it is composed of a container to be formed, a hydrogen storage alloy housed in the container and absorbing a predetermined amount of hydrogen, and an inert gas filled in the container.

In the flammable gas control system of this nuclear reactor, the size and weight of each container are taken into consideration so that a person can easily carry them. Then, in the reactor containment vessel, a plurality of combustible gas control devices for the nuclear reactor are preliminarily distributed and arranged at predetermined positions.

[0015]

[Function] At the time of a reactor accident, the temperature, pressure, relative humidity and radiation level in the reactor containment vessel are all significantly increased, and the ambient temperature, pressure, relative humidity and Since the radiation level is also significantly increased, a significant change of one or more of them becomes an operating force, and an opening is formed in a part of the lower portion of the container containing the hydrogen storage alloy.

As a result, the hydrogen storage alloy contained inside is exposed from the lower portion of the container with the opening opened and gradually released to the outside. On the surface of the released hydrogen storage alloy, a predetermined amount of hydrogen that has been absorbed and stored inside the alloy in advance and oxygen in the reactor containment vessel undergo a combustion reaction, and the temperature of the alloy rises.

As the temperature rises, the hydrogen storage capacity of the alloy decreases, and by continuing to release hydrogen, the combustion reaction on the surface of the alloy continues and the temperature of the alloy remarkably rises. During this time,
The alloy particles continue to release hydrogen and burn while collapsing into finer particles due to volume change during hydrogen release or volume change due to heating, and consume oxygen in the reactor containment vessel.

On the other hand, the particles of the alloy, which have thus become hot due to the combustion reaction of hydrogen and oxygen on the surface of the alloy, are released into the reactor containment vessel at the time of accident from the hydrogen released from the reactor core. It acts as an ignition source of and promotes the combustion of hydrogen and oxygen for treatment. In this way, it is possible to prevent the occurrence of a rapid explosion phenomenon of hydrogen and oxygen over a wide range, and to prevent the destruction of the reactor containment vessel due to a rapid increase in pressure.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a flammable gas control device for a nuclear reactor according to the present invention will be described with reference to FIGS. FIG. 1 shows an example in which a flammable gas control device 13 is installed in the reactor containment vessel 12. In FIG. 1, reference numeral 14 is a core, 15 is an internal pump,
Reference numeral 16 is a pressure suppression chamber, 17 is pool water, 18 is a main steam pipe, 19 is a water supply pipe, and 20 is a pedestal. here,
The reactor 11 is housed in a reactor containment vessel 12, and in the reactor containment vessel 12, a plurality of combustible gas control devices 13 are dispersedly arranged at predetermined positions. FIG. 2 is a basic configuration diagram of the combustible gas control device 13 in FIG.

The combustible gas control device 13 of a nuclear reactor comprises a container 25 composed of a casing 21, a hopper 22, a cap 23 and legs 24, a hydrogen storage alloy 26 filled in the container 25 and an inert gas. It is composed of gas 27, and a predetermined amount of hydrogen is previously absorbed and stored in the hydrogen storage alloy 26. Below the combustible gas control device 13 of the nuclear reactor, a receiver 31 illustrated in FIG. 3 is arranged as necessary. This receptor
31 is composed of a side plate 32 and a net 33 stretched on the bottom surface.

Next, a case where the inside of the reactor containment vessel 12 is in an air atmosphere will be described as an example. In addition, hydrogen storage alloy 26
There are alloys having a property of generating heat with absorption of hydrogen and alloys having a property of absorbing heat. However, an alloy having a property of generating heat with absorption and storage of hydrogen will be described as an example. Furthermore, the case where the combustible gas control device for a nuclear reactor according to the present invention starts its operation when the ambient temperature thereof significantly increases will be described as an example.

The inside of the reactor containment vessel 12 is cooled by an air conditioning facility (not shown) during normal operation of the reactor or during shutdown of the reactor, so that flammable gas control distributed in the reactor containment vessel 12 is controlled. The device 13 is also cooled and stored. Therefore, the hydrogen storage alloy 26 contained in the container 25 constituting the combustible gas control device 13 is also maintained in a cold temperature state, and the hydrogen absorbed therein is stably stored.
Further, since the container 25 is filled with the inert gas 27, the hydrogen storage alloy 26 contained in the container 25 is
It can be stably stored for a long time without deterioration.

By the way, in the unlikely event of a nuclear reactor accident, a large amount of steam or heat is released inside the reactor containment vessel 12, and as a result, the internal temperature, pressure, relative humidity and radiation level remarkably increase. To rise. Moreover, if the accident event progresses beyond the design criteria such that the emergency core cooling system does not operate due to some unforeseen event, as experienced at the Three Mile Power Station in the United States, the fuel cladding that constitutes the core (not shown) A large amount of hydrogen is released inside the reactor containment vessel 12 due to the significant oxidation reaction of the tube.

Further, hydrogen and oxygen are released into the reactor containment vessel 12 by the radiolysis of water. At the time of such an accident event, the reactor combustible gas control device 13 according to the present invention operates in the following procedure to burn and process a large amount of hydrogen released inside the reactor containment vessel 12. You can

Since the ambient temperature of the combustible gas control device 13 of the reactor according to the present invention also remarkably rises as the temperature inside the reactor containment vessel 12 remarkably rises, the hydrogen storage alloy 26 and the inside thereof are filled. The inert gas 27 expands and stress concentrates on the cap 23 located under the container 25, and the cap 23 is damaged.

When the cap 23 is damaged, the hydrogen storage alloy 26 contained in the container 25 is exposed through the opening of the damaged portion and gradually released to the outside. When the hydrogen storage alloy 26 is exposed and released, it is released by radiolysis of a predetermined amount of hydrogen that has been absorbed and stored in the alloy in advance and oxygen and water existing in the reactor containment vessel 12 in advance. A combustion reaction with oxygen occurs on the surface of the hydrogen storage alloy 26, and the temperature of the hydrogen storage alloy 26 rises.

With the increase, the hydrogen storage capacity of the hydrogen storage alloy 26 is reduced and hydrogen is continuously released, so that the combustion reaction on the surface of the hydrogen storage alloy 26 is continued and the temperature of the hydrogen storage alloy 26 is significantly increased. .. During this period, the particles of the hydrogen storage alloy 26 continue to release and burn hydrogen while collapsing into finer particles according to the situation such as volume change at the time of hydrogen release or volume change due to heating.

Particles of the hydrogen storage alloy 26, which have been heated to a high temperature by the combustion reaction of hydrogen on the surface of the hydrogen storage alloy 26 in this manner, are discharged from the reactor core (not shown) of the reactor 11 due to the accident. It acts as an ignition source for the hydrogen released into the inside of 12 and promotes the combustion reaction of hydrogen and oxygen in the atmosphere for treatment. As a result, hydrogen accumulates and exceeds the deflagration limit, causing a rapid explosion phenomenon of hydrogen, which causes the pressure inside the reactor containment vessel 12 to rise rapidly, destroying the reactor containment vessel 12 itself. It is possible to prevent the occurrence of the situation.

Incidentally, the receiver 31 arranged below the combustible gas control device 13 of the nuclear reactor temporarily holds the falling hydrogen storage alloy 26 on the net 33, if necessary. As a result, the hydrogen acts as an ignition source for hydrogen that passes through the net 33 and rises, further promoting the combustion reaction. The hydrogen storage alloy 26 decomposed into fine particles on the net 33 is
While falling downward from the hole of 33, it acts as an ignition source of surrounding hydrogen and oxygen and promotes the combustion reaction.

The combustible gas control device 13 for a nuclear reactor according to the present embodiment configured and operated as described above uses the thermal energy released in the event of an accident as the operation start energy of the combustible gas control device 13 for a nuclear reactor. Since it is used, it does not require any external utility and will reliably start operation in the event of a nuclear reactor accident.

After that, the property peculiar to the hydrogen storage alloy 26 that hydrogen stored inside is released when heat is applied,
Due to the unique action of the hydrogen storage alloy 26, in which the presence of oxygen in the surroundings causes a gentle combustion on the surface, the particles of the hydrogen storage alloy 26 are heated to a high temperature state, and the reactor containment vessel is heated.
12 Acts as an ignition source for starting the combustion of hydrogen and oxygen mixed in the atmosphere inside.

As a result, a large amount of hydrogen released into the reactor containment vessel 12 is processed by a gentle combustion reaction with oxygen, so that the hydrogen is accumulated over a wide range and reaches the explosion limit. Moreover, it is possible to prevent the occurrence of a situation in which the nuclear reactor containment vessel 12 is destroyed by exploding in a wide range.

In this way, the function of the nuclear reactor containment vessel 12 for trapping radioactive material is maintained by the action of the combustible gas control device 13. Moreover, since the combustible gas control device 13 of the present embodiment is composed entirely of static equipment, it is not necessary to carry out the periodical operation test, which has been conventionally required, every three months. In addition, it does not require any utility from the outside and is sure to operate in the event of an accident. further,
Since it can be easily carried, it is possible to easily check its operating performance, etc., by using a separate test facility if necessary.

Further, since the replacement is easy, the workability is improved, and the replacement system is provided with spare parts, so that various inspections, which were conventionally concentrated during the periodic inspection period of the reactor, can be performed at a certain time. It is also possible to shift and implement.

Next, another embodiment of the combustible gas control device for a nuclear reactor according to the present invention will be described with reference to FIG. In FIG. 4, the combustible gas control device 41 at the time of a nuclear reactor accident has a main body casing 42, a cap 43, a hinge 44, a saucer 45, a hydrogen storage alloy 46 filled inside, an inert gas 47, and a lower part thereof independently. It is composed of a collection tray 48 arranged. A predetermined amount of hydrogen is absorbed and stored in the hydrogen storage alloy 46 in advance.

In the combustible gas control device 41 for a nuclear reactor configured as described above, when the ambient temperature rises remarkably due to the thermal energy released in the event of a nuclear reactor accident and the time lasts for a predetermined time, the cap 43 An opening is formed in the central portion of the cap 43 by melting the metal or the like that has blocked the opening at the center of the cap 43. When an opening is formed in the center of the cap 43, the hydrogen storage alloy 46 flows out to the upper surface of the pan 45.

At that position, the temperature rises remarkably by the same action as in the above-mentioned embodiment, and it acts as an ignition source for the combustion reaction of hydrogen and oxygen around the tray 45. After that, when the particles of the hydrogen-absorbing alloy 46 on the upper surface of the receiving tray 45 collapse and become finer particles with the passage of time, they fall from the opening of the receiving tray 45 and are collected in the collecting tray 48 located below, and they are also deposited there. Acts as a fire source.

The particles falling during this period effectively act as an ignition source for the combustion reaction of hydrogen and oxygen existing around them. On the other hand, when the hydrogen storage alloy 46 on the pan 45 decreases due to the falling of particles, the hydrogen storage alloy 46 in an amount corresponding to the decreased amount newly flows out from the opening and is replenished, and the ignition source continues to be effective. Provided to.

Further, when carrying the combustible gas control device 41 of the nuclear reactor, by rotating the pan 45 around the hinge 44 and storing it along the main body casing 42,
It can be easily carried.

Next, the operation when the reactor containment vessel 12 is filled with an inert gas will be described. When a nuclear reactor accident occurs, radiation emitted from radioactive materials released into the reactor containment vessel 12 accelerates radiolysis of water, and hydrogen and oxygen are released into the reactor containment vessel 12. Also, depending on the progress of the accident, a large amount of hydrogen is released due to the remarkable oxidation reaction of the fuel cladding tube as described above.

In such a situation, when the combustible gas control device 13 (41) of the reactor according to the present embodiment operates, the combustion reaction of hydrogen and oxygen generated on the surface of the hydrogen storage alloy causes the reactor containment vessel 12 As a result of the consumption of oxygen therein, the oxygen concentration in the reactor containment vessel 12 is maintained below the flammability limit of 5%, and the integrity of the reactor containment vessel 12 is maintained.

If necessary, the hydrogen storage alloy 26
By adding an appropriate catalyst such as palladium or platinum to the surface of (46), the combustion reaction with hydrogen at low oxygen concentration can be promoted.

In each of the above-mentioned embodiments, a significant increase in ambient temperature is used as the operating force, but the material and shape of the cap 23 (43) are deformed by a significant increase in ambient pressure to form an opening. By substituting the ones described above, it is possible to obtain the same operation and effect as those of the above-mentioned embodiment.

Further, since the relative humidity and the radiation level of the surroundings also remarkably increase at the time of an accident, one or more of these changes in temperature, pressure, relative humidity and radiation level are combined, and these changes are taken as the operating force. May be configured to form an opening. In addition, in order to make the operation of the case more reliable, it is also possible to adopt a method of remotely opening a small amount of explosive powder, a small valve, etc. or automatically opening or operating by an accident signal to provide an opening. It is possible.

In this case, it is necessary to regularly check the soundness of the ignition / explosion device, valves, etc., but if it is carried out at the same time as the performance test of the hydrogen storage alloy, the increase of the work amount is minimized. Can be suppressed to. Further, although electric power is required for remote ignition of explosives and actuation of small valves, the capacity thereof is extremely small.

Further, when the reactor containment vessel 12 is filled with an inert gas, a material that consumes oxygen in the atmosphere by causing a significant oxidation reaction by contact with oxygen instead of the hydrogen storage alloy. By using the
By consuming oxygen in the interior and maintaining it below the flammability limit, it is possible to prevent the explosive combustion of hydrogen and maintain the soundness of the reactor containment vessel 12. As a specific example, fine particles of iron or a compound to which an appropriate catalyst is added, a metal material such as sodium or magnesium, or the like can be used.

The embodiment of the present invention is as follows. (1) An opening is formed in the lower part as a significant operating force of the ambient temperature, pressure, relative humidity, and / or radiation level that changes due to the occurrence of a nuclear reactor accident, or a combination thereof. A container, a hydrogen storage alloy housed in the container and storing and storing a predetermined amount of hydrogen, and an inert gas filled in the container. (2) A container configured so that an opening is formed in the lower part automatically or by remote manual operation in the event of a nuclear reactor accident, and a predetermined amount of hydrogen stored in this container is absorbed. It is composed of a stored hydrogen storage alloy and an inert gas filled in the container. (3) In the flammable gas control device at the time of a nuclear reactor accident described in (1) and (2) above, instead of the hydrogen storage alloy in which a predetermined amount of hydrogen is absorbed and stored, a significant oxidation reaction occurs by contact with air. Use metals that consume oxygen due to

[0048]

According to the present invention, a static device is used,
In addition, since the operating principle is simple, it can operate reliably without the need for external utility supply in the event of an accident. Further, it is no longer necessary to carry out a periodical operation test, which has conventionally been required to be carried out approximately every three months. Furthermore, regarding performance tests for confirming aging deterioration, etc., it is easy to carry, so by exchanging with spare parts prepared in advance, you can confirm performance using appropriate test equipment at an appropriate time. Therefore, it is possible to disperse the work concentrated on the periodic inspection of the reactor. In this way, the present invention makes it possible to maintain the soundness of the reactor containment vessel in the event of a reactor accident.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a combustible gas control device for a nuclear reactor according to the present invention.

FIG. 2 is a side view showing a partial cross-section of the basic configuration of the combustible gas control device for a nuclear reactor in FIG.

FIG. 3 is a vertical cross-sectional view showing the receiver used in FIG.

FIG. 4 is a vertical cross-sectional view showing a partial side view of another embodiment of the flammable gas control device for a nuclear reactor according to the present invention.

FIG. 5 is a system diagram showing a basic configuration of a conventional combustible gas concentration control device.

[Explanation of symbols]

11 ... Reactor, 12 ... Reactor containment vessel, 13 ... Reactor flammable gas control device, 21 ... Casing, 22 ... Hopper, 23 ... Cap, 24 ... Leg, 25 ... Vessel, 26 ... Hydrogen storage alloy, 27 ... Inert gas, 31 ... Receptor, 32 ... Side plate, 33 ... Net, 41 ... Reactor flammable gas control device, 42 ... Main body casing, 43 ...
Cap, 44 ... Hinge, 45 ... Receptacle, 46 ... Hydrogen storage alloy, 47 ... Inert gas, 48 ... Recovery tray.

Claims (1)

[Claims] 1. A container in which an opening is formed in part by using an increase in ambient temperature, pressure, relative humidity and radiation level, or a combination thereof, installed in a reactor containment vessel as an operating force. A combustible gas control device for a nuclear reactor, comprising a hydrogen storage alloy housed in a container and absorbing a predetermined amount of hydrogen, and an inert gas filled in the container.