JP2022181928A - Device and method for treating oxygen - Google Patents

Abstract

To provide a device and a method for treating oxygen capable of efficiently reducing oxygen concentration in a reactor containment vessel.SOLUTION: An oxygen treatment device for treating oxygen in a reactor containment vessel includes: an oxygen treatment vessel; an oxygen treatment material that is filled in the oxygen treatment vessel and reacts with oxygen to form an oxide; a heating device for heating the oxygen treatment material; a gas introduction pipe for introducing a gas into the oxygen treatment vessel from inside of the reactor containment vessel; and a gas return pipe for returning the gas from inside of the oxygen treatment vessel into the reactor containment vessel.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD Embodiments of the present invention relate to an oxygen treatment apparatus and an oxygen treatment method.

When a severe reactor accident involving severe core damage occurs in a BWR reactor, the reaction between zirconium contained in the molten core and cooling water (Metal-Water reaction: Zr + H ₂ O → ZrO ₂ + H ₂ ) (hereinafter , MW reaction) and the radioactive decomposition of water (H ₂ O→H ₂ +0.5O ₂ ) generate hydrogen and oxygen.

Hydrogen is produced in large quantities and is the main cause of containment overpressure leading to containment failure. To avoid this, a depressurization operation called containment vessel venting is performed.

In the containment vessel vent, measures are taken to install filter vent equipment that can collect radioactive materials contained in the containment vessel in order to prevent the release of radioactive materials to the outside.

However, at the Fukushima Daiichi Nuclear Power Station, before the depressurization operation was performed, the hydrogen accumulated in the containment vessel leaked from the upper part of the containment vessel, causing a hydrogen explosion in which oxygen contained in the air reacted with hydrogen, causing the containment vessel to collapse. Since damage events were confirmed, it is considered necessary to take measures to reduce the amount of hydrogen in the containment vessel before venting the containment vessel.

As part of such countermeasures, various methods for treating hydrogen have been investigated.

For example, Patent Literature 1 proposes catalytic hydrogen combustion in which a catalyst is used to react hydrogen and oxygen. However, this method requires a large amount of catalyst because the reaction temperature is high, the pressure in the containment vessel may rise due to the high temperature after the reaction, and the catalytic function is impaired due to carbon monoxide poisoning. However, the amount of oxygen is insufficient for the amount of hydrogen in the containment vessel, so it is necessary to supply oxygen from the outside, which is dangerous.

Japanese Patent No. 3596843

Even if the amount of hydrogen, which is the main factor that promotes overpressure of the containment vessel, is reduced, a hydrogen explosion will occur inside the containment vessel if the concentration of oxygen produced by radioactive decomposition of water approaches the explosion limit concentration (5 vol%). Danger arises. Therefore, it is necessary to reduce oxygen in the containment vessel as well as hydrogen treatment. For example, even if the pressure inside the containment vessel has not risen to a level that requires containment venting, it may become necessary to vent the containment vessel when the concentration of oxygen approaches the explosive limit concentration.

In the current method, a combination of hydrogen treatment with metal oxides and catalytic hydrogen combustion (PAR) using oxygen is being considered. There is a concern that the system configuration will become complicated, that the scale of the entire apparatus will increase, and that the price will increase. Also, in oxygen removal by catalytic hydrogen combustion (PAR), catalytic function may be lost due to reaction inhibition.

Typical examples of reaction inhibitors include water vapor generated when water evaporates due to the heat generated by the MW reaction, carbon monoxide generated by the reaction between the concrete that makes up the building and the molten core, and cable melting, and radioactive decomposition products. Typical examples include cesium iodide, inorganic iodine, and methyl iodide.

As described above, in a nuclear power plant, etc., it is possible to prevent the occurrence of a hydrogen explosion by reducing the oxygen concentration in addition to the hydrogen concentration, and to prevent the release of radioactive materials to the outside by reducing the possibility of containment vessel venting. It is required to do so.

The present invention has been made in response to such conventional circumstances, and its object is to provide an oxygen treatment apparatus and an oxygen treatment method capable of efficiently reducing the oxygen concentration in a nuclear reactor containment vessel. It is in.

An oxygen treatment apparatus according to an embodiment is an oxygen treatment apparatus for treating oxygen in a nuclear reactor containment vessel, and includes an oxygen treatment vessel, an oxygen treatment vessel filled in the oxygen treatment vessel, and an oxygen treatment that reacts with oxygen to form an oxide. a heating device for heating the oxygen treatment material; a gas introduction pipe for introducing gas from inside the reactor containment vessel into the oxygen treatment vessel; and from inside the oxygen treatment vessel into the reactor containment vessel. and a gas return pipe for returning gas to.

The figure which shows the structure of the oxygen treatment apparatus of embodiment. The figure which shows the structure of the oxygen treatment apparatus of other embodiment. The figure which shows the structure of the oxygen treatment apparatus of other embodiment. The figure which shows the structure of the oxygen treatment apparatus of other embodiment.

Hereinafter, an oxygen treatment apparatus and an oxygen treatment method according to embodiments will be described with reference to the drawings.

FIG. 1 shows the configuration of an oxygen treatment device 10 according to an embodiment. As shown in FIG. 1, the oxygen treatment apparatus 10 includes an oxygen treatment container 11, and the oxygen treatment container 11 is filled with an oxygen treatment material 12 that reacts with oxygen to form an oxide. . A heating device 13 for heating the oxygen treatment material 12 filled inside is provided around the oxygen treatment container 11 .

The oxygen treatment apparatus 10 also includes a gas introduction pipe 2 for introducing a gas to be oxygenated from the reactor containment vessel 1 into the oxygen treatment vessel 11 , A gas return line 3 is provided for returning the treated gas. The gas introduction pipe 2 is provided with a blower 4 for circulating gas and an inlet valve 5 for adjusting opening and closing of the inlet. On the other hand, the gas return pipe 3 is provided with an outlet valve 6 for adjusting opening/closing of the outlet. It should be noted that the heating device 13 does not necessarily need to be provided around the oxygen treatment container 11, and may be provided in the gas introduction pipe 2 or the like to heat the gas to a predetermined temperature before being introduced into the oxygen treatment container 11. good.

In the oxygen treatment apparatus 10 configured as described above, the oxygen treatment material 12 in the oxygen treatment container 11 is heated in advance by the heating device 13, the inlet valve 5 and the outlet valve 6 are opened, and the blower 4 is started to operate the reactor. The gas in the containment vessel 1 is introduced into the oxygen treatment vessel 11 through the inlet pipe 2 and reacted with the oxygen treatment material 12 to remove oxygen in the gas. The treated gas is returned into the containment vessel 1 through the gas return pipe 3 .

In the oxygen treatment apparatus 10 having the above configuration, the oxygen treatment material 12 to be filled in the oxygen treatment container 11 includes, for example, metals generated when the hydrogen treatment material described later is reduced, such as nickel (Ni), copper (Cu), Iron (Fe), cobalt (Co), chromium (Cr), manganese (Mn), etc. can be used. In the oxygen treatment in the oxygen treatment device 10, these metals react with oxygen to form metal oxides, removing the oxygen in the gas.

The form of the oxygen treating material 12 can be a filling layer composed of a compact such as metal from the viewpoint of reducing the pressure loss of the device. In this case, a filling layer is produced by combining a plurality of molded bodies made of a single metal, etc., or several types of molded bodies containing two or more types of metals, etc. It can be in a porous form like a body. Also, the shape of the compact may be a grain shape.

The combination of the oxygen treatment materials 12 as described above can be achieved by utilizing the differences in the maximum oxidation rate of metals, etc., the range of reaction temperature, the amount of heat generated, etc., and by devising the filling method of the compact, thereby improving the reaction rate and temperature. Provide control.

As for the control of the reaction rate, it is also effective to change the particle size of the treatment material. Taking the case of the oxygen treatment material 12 as an example, even if the filling amount is the same, the larger the particle size of the compact, the lower the reaction rate as the gas diffuses into the inside of the compact. As the ratio of the treatment material on the surface of the compact increases, the reaction speed increases. Based on the relationship between the particle size and the reaction rate, the size of the compact is effective in controlling the reaction, and the particle size is preferably 0.1 to 100 mm.

The gas introduced from the reactor containment vessel 1 contains the aforementioned reaction inhibitors (water vapor, carbon monoxide, cesium iodide, inorganic iodine, methyl iodide, etc.). Therefore, as will be described later, if a reaction inhibitor removal device is not provided upstream of the oxygen treatment vessel 11, the oxygen treatment material 12 should be selected from metals that are less affected by reaction inhibitors, such as copper and manganese. is preferred. In this case, when copper is used as the oxygen treating material 12, the heating temperature is preferably about 200 to 500.degree. Further, when manganese is used as the oxygen treatment material 12, the heating temperature is preferably about 150 to 250.degree.

On the other hand, when metals that are often affected by reaction inhibitors, such as nickel that reacts with carbon monoxide to generate harmful nickel carbonyl and iron that reacts with high-temperature steam to generate hydrogen, are used as the oxygen treatment material 12 . , will be more affected by reaction inhibitors.

On the other hand, as shown in FIG. 2, when the reaction inhibitor removing device 14 is provided on the upstream side of the oxygen treatment container 11, there is no need to consider the influence of reaction inhibitors, and it is possible to use the oxygen treatment material 12 as the oxygen treatment material 12. Wider selection of available materials. For example, it is possible to use nickel, iron, or the like as the oxygen treatment material 12 . The reaction inhibitor removal device 14 can use an absorption tower for removing radioactive iodine, a cooler or demister for removing water vapor, an oxidation catalyst for removing carbon monoxide by oxidation, and the like. In FIG. 2, parts corresponding to those in the embodiment shown in FIG. 1 are given the same reference numerals, and overlapping explanations are omitted.

FIG. 3 shows another embodiment, showing an example in which a hydrogen treatment device 20 is inserted in the gas introduction pipe 2 of the oxygen treatment device 10 . The hydrogen treatment apparatus 20 includes a hydrogen treatment vessel 21 , a hydrogen treatment material 22 filled in the hydrogen treatment vessel 21 , and a heating device 23 for heating the hydrogen treatment material 22 . The hydrogen treatment device 20 may be installed on the gas return pipe 3 side of the oxygen treatment device 10 . In FIG. 3, parts corresponding to those in the embodiment shown in FIG. 1 are given the same reference numerals, and overlapping explanations are omitted.

As the hydrogen treatment material 22 in the hydrogen treatment apparatus 20, metal oxides suitable for hydrogen treatment, and non-stoichiometric oxides and metals (hereinafter referred to as metals, etc.) produced by reduction after hydrogen treatment are also suitable as oxygen treatment materials. things are preferred. As _the hydrogen treatment _material 22, for example, NiO, CuO, _Fe2O3 , _Co3O4 , _{Cr2O2 , MnO2} , etc. can be used, and two or more of these can be used.

The metal oxide serving as the hydrogen treatment material 22 differs in the maximum value of the reaction rate of hydrogen treatment, the range of reaction temperature, and the amount of heat generated. For example, copper (II) oxide has a higher maximum reaction rate than other metal oxides at 200° C. or higher, and also has the highest calorific value per amount of hydrogen treated. In addition, nickel (II) oxide reacts at 300° C. or higher, and its reaction rate is about 1/3 that of copper oxide, but its calorific value per amount of hydrogen treated is about 1/10 that of copper oxide.

Considering the maximum reaction rate of metal oxides, the range of reaction temperature, the amount of heat generated, etc., it is preferable that the hydrogen treatment material 22 is arranged by combining two or more kinds of metal oxides.

The hydrogen treatment material 22 can be a filling layer composed of a compact such as a metal oxide from the viewpoint of reducing the pressure loss of the apparatus. In this case, a filling layer is prepared by combining a plurality of molded bodies made of a single metal oxide or the like, or several types of molded bodies containing two or more kinds of metal oxides are produced, and these are appropriately filled to form a filling layer. Alternatively, it may be in a porous form such as a sintered body. Also, the shape of the compact may be a grain shape.

Such a structure of the hydrogen treatment material 22 is mainly aimed at reaction control of hydrogen and oxygen and temperature control.

For example, when a layer comprising a copper oxide compact is arranged upstream and a layer comprising a nickel oxide compact is arranged downstream thereof, the heat generated by the hydrogen treatment reaction of the upstream copper oxide compact causes the downstream nickel oxide is heated. Therefore, the reaction temperature of the downstream nickel oxide compact can be controlled by the amount of copper oxide compact placed upstream.

The reaction rate is controlled by changing the type of metal oxide placed downstream. For example, when it is desired to increase the reaction rate in the downstream nickel oxide molded body, it is conceivable to fill the nickel oxide molded body with a certain proportion of copper oxide. Further, when it is desired to suppress the reaction rate of the downstream nickel oxide molded article, it is conceivable to mix a fixed proportion of a metal oxide having a slow reaction rate or a substance inert to the hydrogen treatment reaction into the nickel oxide molded article. Substances inert to the hydrotreating reaction include, for example, activated alumina, water glass, alumina cement, talc, and cerium oxide.

By controlling the reaction rate and temperature by the methods described above, the temperature environment in which the hydrogen treatment material 22 is placed in the hydrogen treatment apparatus 20 and the temperature environment in the latter stage can be controlled.

As for the control of the reaction rate, it is also effective to change the particle size of the treatment material. Taking the case of the hydrogen treatment material 22 as an example, even if the filling amount is the same, the larger the particle size of the compact, the lower the reaction rate due to gas diffusion into the inside of the compact. As the ratio of the treatment material on the surface of the compact increases, the reaction speed increases. Based on the relationship between the particle size and the reaction rate, the size of the compact is effective in controlling the reaction, and the particle size is preferably 0.1 to 100 mm.

When the hydrogen treatment material 22 is copper (II) oxide and the oxygen treatment material 12 is copper, the reactions of hydrogen treatment and oxygen treatment are as follows.
CuO+ _H2 →Cu+ _H2O (formula 1)
Cu+0.5O ₂ →CuO (Formula 2)
The generated water vapor flows downstream of the hydrogen treatment device 20, that is, to the oxygen treatment device 10 as a post-reaction fluid.

Oxygen generated by the hydrogen treatment material 22 is adsorbed by the oxygen treatment material 12 of the oxygen treatment device 10 .

In the hydrogen treatment material 22 of the hydrogen treatment device 20 , as the reaction progresses, the metal oxides are reduced, and the main reaction site moves to the outlet side of the hydrogen treatment device 22 . Hydrogen moves unreacted to the site where the metal oxide has been reduced, and reacts when it moves to the position where the metal oxide exists. In addition, in the temperature range where oxygen can react, an adsorption reaction of oxygen occurs at the site where the metal oxide has been reduced, and the metal oxide is regenerated.

The hydrogen treatment material 22 reduced by the hydrogen treatment in the hydrogen treatment device 20 can be reused by filling it as the oxygen treatment material 12 in the oxygen treatment device 10 . Further, the oxygen treatment material 12 oxidized by the oxygen treatment in the oxygen treatment device 10 can be reused by filling it as the hydrogen treatment material 22 in the hydrogen treatment device 20 .

From the above viewpoint, the oxygen treatment container 11 and the hydrogen treatment container 21 are not separated, and the oxygen treatment material 12 and the hydrogen treatment material 22 are mixed in one treatment container, so that one treatment can be performed. Hydrogenation and oxygenation may be performed in a container.

That is, for example, like the hydrogen oxygen treatment device 30 shown in FIG. and further, metal oxides such as nickel oxide (II), copper oxide (II), cobalt oxide (II, III), manganese oxide (IV), iron oxide (III), chromium oxide (III), etc. The hydrogen oxygen treatment material 22 is filled and heated by the heating device 33 . In FIG. 4, parts corresponding to those in the embodiment shown in FIG. 1 are given the same reference numerals, and overlapping explanations are omitted.

With such a configuration, hydrogen and oxygen can be treated simultaneously, and the apparatus for treating hydrogen and oxygen can be integrated, thereby making it possible to eliminate the increase in size and complexity of the apparatus. In addition, it is possible to suppress the influence of the reaction-inhibiting fluid on the oxygen treatment by taking measures such as performing the oxygen treatment after the hydrogen treatment.

Although several embodiments of the invention have been described above, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

1... Reactor containment vessel, 2... Gas introduction pipe, 3... Gas return pipe, 4... Blower, 5... Inlet valve, 6... Outlet valve, 10... Oxygen treatment device, 11... Oxygen Treatment container 12 Oxygen treatment material 13 Heating device 14 Reaction inhibitor removal device 20 Hydrogen treatment device 21 Hydrogen treatment container 22 Hydrogen treatment material 23 Heating Apparatus, 30... Oxygen treatment apparatus, 31... Oxygen treatment container, 33... Heating device.

Claims (8)

An oxygen treatment device for treating oxygen in a nuclear reactor containment vessel,
an oxygen treatment vessel;
an oxygen treatment material filled in the oxygen treatment container and reacting with oxygen to form an oxide;
a heating device for heating the oxygenating material;
a gas introduction pipe for introducing gas from the reactor containment vessel into the oxygen treatment vessel;
a gas return pipe for returning gas from the oxygen treatment vessel to the reactor containment vessel;
An oxygen treatment device comprising:
An oxygen treatment apparatus according to claim 1, wherein
The oxygen treatment apparatus, wherein the oxygen treatment material is at least one of Ni, Cu, Fe, Co, Cr, and Mn.
The oxygen treatment device according to claim 1 or 2,
The oxygen treatment device, wherein the oxygen treatment material has a particle size of 0.1 to 100 millimeters.
The oxygen treatment apparatus according to any one of claims 1 to 3,
The oxygen treatment apparatus according to claim 1, wherein the gas introduction pipe is provided with a reaction inhibitor removing device for removing a reaction inhibitor that inhibits the reaction of the oxygen treatment material.
The oxygen treatment device according to any one of claims 1 to 4;
A hydrogen treatment device having a hydrogen treatment material made of an oxide that reacts with hydrogen and is reduced by being inserted in either the gas introduction pipe or the gas return pipe,
An oxygen treatment method, characterized by treating oxygen and hydrogen in the reactor containment vessel.
The oxygen treatment method according to claim 5,
filling the hydrogen treatment device with the oxygen treatment material oxidized in the oxygen treatment device;
An oxygen treatment method, comprising: filling the oxygen treatment device with the hydrogen treatment material reduced in the hydrogen treatment device.
The oxygen treatment device according to any one of claims 1 to 4;
a hydrogen treatment material filled in the oxygen treatment container and made of an oxide that reacts with hydrogen and is reduced;
An oxygen treatment method, characterized by treating oxygen and hydrogen in the reactor containment vessel.
The oxygen treatment method according to any one of claims 5 to 7,
The oxygen treatment method, wherein the hydrogen treatment material is at least one of NiO, CuO, Fe ₂ O ₃ , Co ₃ O ₄ , Cr ₂ O ₂ and MnO ₂ .

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