KR102023032B1 - Method for manufacturing reactor vessel with sintered copper microporous coating and reactor vessel manufactured by the same - Google Patents

Abstract

The present invention is to improve the critical heat flux of the outer surface of the reactor vessel to effectively cool the core melt, to prepare a coating containing copper particles (step 1), applying the coating on the surface of the reactor vessel outer wall (step 2) and sintering the coating to form a sintered layer (step 3), wherein the sintered layer comprises a method for producing a reactor vessel including a reentrant-type cavity and a reactor vessel manufactured accordingly. to provide.

Description

Method for manufacturing reactor vessel manufactured by copper porous sinter coating and reactor vessel manufactured by this method {Method for manufacturing reactor vessel with sintered copper microporous coating and reactor vessel manufactured by the same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a reactor vessel and a reactor vessel manufactured by the same, and more particularly, to improve cooling efficiency by forming a copper particle sintered layer on the outer wall of the reactor vessel.

In the event of a serious accident in a nuclear power plant, nuclear fuel and surrounding structures melt in the reactor, creating a core melt inside the reactor. The core melt generates heat continuously and releases fission products, radioactive materials, which can cause enormous human and property damage. Therefore, the core melt should be cooled well in a short time to minimize the breakage of the structure and the release of radioactive fission products.

In reactors with a heat output of 3000 MWt or less, the in-vessel retention strategy uses gravity to fill the reactor compartment with coolant to cool the outer wall of the reactor vessel by natural circulation of the coolant to trap the core melt in the furnace. have. However, this method is known to have a lot of uncertainty in terms of practical application for the reactor with a high output of about 4000 MWt due to the lack of heat removal by external wall cooling.

In the case where the output of the reactor is not heat removed by cooling the outer wall in the reactor, the core melt may be discharged to the outside through the reactor due to heat concentration phenomenon occurring in the metal melt layer formed on the upper part of the melt. Since the coolant is already filled in the reactor compartment, a vapor explosion occurs due to the contact of the discharged core melt with the coolant, resulting in a breakdown of the reactor compartment or a breakdown of the reactor vessel and associated piping, which impairs the airtightness of the containment vessel, which in turn stores the radioactive material. There is a risk of release to the outside of the container.

Korea Patent Registration 10-1651576

The present invention is to provide a method for forming a coating layer and a method for producing a reactor vessel, and a reactor vessel manufactured by the same to effectively cool down the core melt generated inside the reactor in the event of a serious accident of nuclear power plant to prevent breakage of the reactor vessel and release of radioactive material. The purpose is to.

It is an object of the present invention to provide a method for forming a coating layer and a method for manufacturing a reactor vessel, and a reactor vessel manufactured thereby, which can improve the critical heat flux to increase the heat transfer efficiency of the reactor vessel outer wall.

The present invention includes the steps of preparing a coating agent containing copper particles (step 1), applying the coating agent on the surface of the reactor vessel outer wall (step 2) and sintering the coating agent to form a sintered layer (step 3) And the sintered layer comprises a reentrant-type cavity.

The copper particles may have an average diameter of 10 to 67 μm.

The sintered layer may have a thickness of 78 to 428 μm.

The sintered layer may have a porosity of 0.6 to 0.7.

The copper particles may be contained in 70 to 90% by weight based on 100% by weight of the coating agent.

The present invention includes a copper particle sintered layer on an outer wall surface, and the sintered layer includes a reactor vessel including recessed holes.

The copper particles may have an average diameter of 10 to 67 μm.

The sintered layer may have a thickness of 78 to 428 μm.

The sintered layer may have a porosity of 0.6 to 0.7.

According to the coating layer forming method and the reactor vessel manufacturing method according to an embodiment of the present invention, it is possible to improve the cooling efficiency of the outer wall of the reactor vessel and further prevent the radiation leakage damage caused by the discharge of the core melt during a serious accident.

According to the coating layer forming method and the reactor vessel manufacturing method according to an embodiment of the present invention, the critical heat flux and boiling heat transfer coefficient are significantly increased to enable the in-vessel retention strategy even for reactors with high heat output during core melting. .

1 is a SEM plan view showing a coating layer including a reentrant hole formed in accordance with Example 1 of the present invention.
2 is a SEM cross-sectional view showing a coating layer including a reentrant hole formed in accordance with an embodiment of the present invention.
3 and 4 are graphs showing the critical heat flux and the boiling heat transfer coefficient of the coating layer formed according to the embodiment of the present invention, respectively.
5 shows a boiling heat transfer curve when a heat flux is given to an outer wall of a copper substrate according to an embodiment and a comparative example of the present invention.
FIG. 6 illustrates boiling heat transfer according to a position at which a heat flux is applied to an outer wall of a copper substrate in an embodiment of the present invention.
7 illustrates a reactor vessel according to an embodiment of the present invention.
Figure 8 shows the critical heat flux margin of the reactor vessel according to the embodiment and comparative example of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for clarity, and the elements denoted by the same reference numerals in the drawings are the same elements. In addition, the same reference numerals are used throughout the drawings for parts having similar functions and functions. In addition, "comprising" any component throughout the specification means that, unless specifically stated otherwise, it may further include other components without excluding other components.

The present invention includes the steps of preparing a copper substrate (step A), applying a coating agent containing copper particles to the copper substrate (step B), and sintering the coating agent to form a coating layer (step C) The coating layer may include a reentrant-type cavity, and may provide a method of forming a coating layer through copper porous sintering.

Hereinafter, the coating layer forming method of the present invention will be described in detail.

In step A, the copper substrate may mean a substrate containing copper as a main component. After polishing the surface of the copper substrate, it may be prepared by washing with alcohol or acetone and drying.

Step B is a step of preparing and applying a coating agent containing copper particles to form a copper particle coating layer on a copper substrate. The coating layer can improve the critical heat flux and the boiling heat transfer coefficient when a heat flux is given to the copper substrate.

The coating agent may include copper particles, diluents, binders, and the like, and the rest may be water.

Copper particles included in the coating agent may have an average diameter of 10 to 67 ㎛. If the average diameter of the copper particles is larger than 67 μm, densification does not proceed during sintering, and it is difficult to form a high-density copper particle coating layer. On the other hand, if the average diameter of the copper particles is less than 10 ㎛, the total surface area of the copper particles is increased, as a result of which the amount of the binder to be added to the coating agent increases, there is a problem that the shrinkage after sintering increases.

The copper particles may be contained in 70 to 90% by weight based on 100% by weight of the coating agent. If it is less than 70% by weight, the shrinkage rate during sintering may increase, thereby lowering the precision. In addition, when the content of the binder and water is relatively reduced at more than 90% by weight, the formation of the coating layer may be impossible or the composition of the coating agent may be uneven.

The manufacturing method of the said copper particle is not specifically limited, For example, the thing manufactured by the water spray method, the gas spray method, the reduction method, or the crushing method can be used.

The coating agent may include a diluent. The diluent may include butane, pentane, hexane, cyclohexane, nonane, decaine or higher homologs and coatings thereof.

The coating agent may comprise a binder. The binder may function as a binder for bonding the copper particles to each other, and may function as a dispersant for uniformly dispersing the copper particles in the coating agent. Examples of the binder include starch, organic substances such as agar, and water-soluble resins such as polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and water-soluble nylon. The content of the binder is preferably 0.2 to 5% by weight of the entire coating. If less than 0.2% by weight, the bonding of the copper particles constituting the coating layer is weak, and if more than 5% by weight, the porosity in the coating layer is excessively increased after sintering.

In the coating agent, various additives such as plasticizers, antioxidants, degreasing accelerators, and surfactants may be added as necessary.

The coating layer may be formed in anticipation of a shrinkage amount due to sintering when the coating agent is applied to a copper substrate.

Step C is a step of forming a coating layer on the copper substrate by sintering the coating agent prepared as described above. When firing in a sintering furnace, sintering may be performed with a degreasing process.

The coating layer may have a thickness of 78 to 428 μm. In one embodiment, the thickness, porosity, etc. of the coating layer may be differently formed according to the angle and intensity of the heat flux emitted through the copper substrate.

The coating layer may have a porous fine concavo-convex structure in which concave holes are formed therein, and an average porosity may be 0.6 to 0.7. The reentrant hole can improve the heat transfer coefficient by increasing the frequency of generation of nuclear boiling bubbles.

The porosity ε is obtained by the following equation.

V _t : volume of coating layer

m _cp : weight of copper particles

ρ _cp : density of copper particles (= 8.96 g / cm ³ )

In forming the coating layer, it is preferable to sinter in the absence of oxygen. For example, it is preferable to set it as a non-oxidizing atmosphere, such as under reduced pressure, under vacuum, or high purity nitrogen and argon. This can prevent deterioration of properties due to metal oxidation. The sintering step can be carried out in two or more steps. For example, primary sintering and secondary sintering with different sintering conditions can be performed. In this case, the sintering temperature of secondary sintering can be made higher than the sintering temperature of primary sintering. Accordingly, the efficiency of sintering can be further improved.

Method of Making a Reactor Vessel

The present invention includes the steps of preparing a coating agent containing copper particles (step 1), applying the coating agent on the surface of the reactor vessel outer wall (step 2) and sintering the coating agent to form a sintered layer (step 3) And the sintered layer comprises a reentrant-type cavity.

Hereinafter, the reactor vessel manufacturing method of the present invention will be described in detail.

Step 1 is a step of preparing a coating agent containing the copper particles to form a copper particle sintered layer on the outer wall of the reactor vessel. The copper particle sintered layer is configured to effectively remove the decay heat generated in the core melt during a serious accident by improving the critical heat flux of the outer wall of the reactor vessel.

The coating agent may include copper particles, diluents, binders, and the like, and the rest may be water.

Copper particles included in the coating agent may have an average diameter of 10 to 67 ㎛. If the average diameter of the copper particles is larger than 67 µm, densification does not proceed during sintering, and it is difficult to form a high-density copper particle sintered layer. On the other hand, if the average diameter of the copper particles is less than 10 ㎛, the total surface area of the copper particles is increased, as a result of which the amount of the binder to be added to the coating agent increases, there is a problem that the shrinkage after sintering increases.

The copper particles may be contained in 70 to 90% by weight based on 100% by weight of the coating agent. If it is less than 70% by weight, the shrinkage rate during sintering may increase, thereby lowering the precision. In addition, when the content of the binder and water is relatively reduced at more than 90% by weight, the formation of the sintered layer may be impossible or the composition of the coating may be uneven.

The manufacturing method of the said copper particle is not specifically limited, For example, the thing manufactured by the water spray method, the gas spray method, the reduction method, or the crushing method can be used.

The coating agent may include a diluent. The diluent may include butane, pentane, hexane, cyclohexane, nonane, decaine or higher homologs and coatings thereof.

The coating agent may comprise a binder. The binder may function as a binder for bonding the copper particles to each other, and may function as a dispersant for uniformly dispersing the copper particles in the coating agent. Examples of the binder include starch, organic substances such as agar, and water-soluble resins such as polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and water-soluble nylon. The content of the binder is preferably 0.2 to 5% by weight of the entire coating. In the case of less than 0.2% by weight, the bonding of the copper particles constituting the sintered layer is weak. In the case of more than 5% by weight, the porosity in the sintered layer is excessively increased after sintering.

In the coating agent, various additives such as plasticizers, antioxidants, degreasing accelerators, and surfactants may be added as necessary.

A method of manufacturing a reactor vessel according to an embodiment of the present invention includes applying a coating agent prepared as described above to the reactor vessel outer wall and baking in a sintering furnace to form a sintered layer. According to the formation angle of the outer wall of the reactor vessel when the coating agent is applied, the amount of shrinkage due to sintering may be expected to form a sintered layer. When firing in a sintering furnace, sintering may be performed with a degreasing process.

The sintered layer may have a thickness of 78 to 428 μm. In one embodiment, the thickness, porosity, etc. of the sintered layer may be differently formed according to the angle and intensity of the heat flux at which the heat of collapse of the core melt is released.

The sintered layer may have a porous fine concavo-convex structure in which concave holes are formed therein, and an average porosity may be 0.6 to 0.7. The reentrant hole can improve the heat transfer coefficient by increasing the frequency of generation of nuclear boiling bubbles.

The porosity ε is obtained by the following equation.

V _t : volume of the sintered layer

m _cp : weight of copper particles

ρ _cp : density of copper particles (= 8.96 g / cm ³ )

At the time of forming the sintered layer, it is preferable to sinter in the absence of oxygen. For example, it is preferable to set it as a non-oxidizing atmosphere, such as under reduced pressure, under vacuum, or high purity nitrogen and argon. This can prevent deterioration of properties due to metal oxidation. The sintering step can be carried out in two or more steps. For example, primary sintering and secondary sintering with different sintering conditions can be performed. In this case, the sintering temperature of secondary sintering can be made higher than the sintering temperature of primary sintering. Accordingly, the efficiency of sintering can be further improved.

Reactor vessel

The reactor vessel according to the embodiment of the present invention includes a copper particle sintered layer on the surface of the reactor vessel outer wall, the sintered layer includes a reentrant hole.

7 illustrates a reactor including a reactor vessel in accordance with an embodiment of the present invention. Referring to FIG. 7, a reactor vessel 10, a shield vessel 20 which forms a reactor cavity 15 by accommodating the reactor vessel so as to be spaced apart from the reactor vessel, and a containment vessel accommodating the reactor vessel and the shield vessel. 30, a cooling water 2 is disposed between the reactor cavity, the containment vessel, and the shielding vessel.

The reactor vessel outer wall may be formed of a metal material such as copper, and the lower portion of the reactor vessel may have a hemispherical shape convex downward. The sintered layer 11 formed on the reactor vessel outer wall absorbs heat transferred through the outer wall of the reactor vessel 10 by the coolant 2 disposed between the reactor cavity and the containment vessel and the shield vessel. Helps to cool the outer wall of the).

In the event of a serious accident, the high melt heat of the core melt causes the cooling water to boil off the outer wall and may fail to reach the critical heat flux point, which is the boiling point. Further, when the critical heat flux is reached, the heat transfer surface may be covered with steam generated by boiling, which may render it impossible to perform effective heat transfer. Therefore, in the worst case, the reactor pressure vessel may be broken, and the core may have a high radioactive core melt.

The sintered layer formed according to the embodiment of the present invention increases the critical heat flux and the boiling heat transfer coefficient of the outer wall of the reactor vessel so that the amount of decay heat generated in the core melt does not exceed the critical heat flux. It also prevents particle desorption from the reactor vessel outer wall surface for more than 40 years of reactor operation, increasing durability and long-term reliability.

Copper particles constituting the copper particle sintered layer may have an average diameter of 10 to 67 ㎛. If the average diameter of copper particle | grains is larger than 67 micrometers, densification does not advance at the time of sintering, and it is difficult to form a high-density copper particle sintering layer. On the other hand, when the average diameter of copper particle is less than 10 micrometers, there exists a problem that the total surface area of a copper particle becomes large and shrinkage rate after sintering becomes large.

The sintered layer may have a thickness of 78 to 428 μm. The sintered layer formed on the outer wall of the reactor vessel may be formed thicker in the region where the heat flux in which the collapse heat of the core melt is released.

The sintered layer may have a porous fine concavo-convex structure in which concave holes are formed therein, and an average porosity may be 0.6 to 0.7. The reentrant hole can improve the heat transfer coefficient by increasing the frequency of generation of nuclear boiling bubbles.

The porosity ε is obtained by the following equation.

V _t : volume of the sintered layer

m _cp : weight of copper particles

ρ _cp : density of copper particles (= 8.96 g / cm ³ )

Hereinafter, preferred embodiments of the present invention will be described in detail. However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited to the following examples.

Example 1

The copper substrate was sanded with 600 grit of sand paper and then sonicated with isopropyl alcohol for 15 minutes. The copper substrate was washed with distilled water and dried with compressed air. A coating agent in which a copper powder having an average particle size of 67 μm was mixed at a weight ratio of butane and 5: 1 was uniformly applied onto the planar copper substrate. The copper substrate coated with the coating was placed on a hot plate at 100 ° C. for 10 minutes and the butane was evaporated to dry the copper powder. The dried copper substrate was placed in a sintering furnace, and argon was blown into the sintering furnace, followed by sintering at 1000 ° C. for 10 minutes. The coating on the copper substrate was sintered to form a coating layer having a thickness of 78 μm, 120 μm, 200 μm, 296 μm, 360 μm, 428 μm, and then naturally cooled in a furnace. When the temperature of the sintering furnace is lowered to 100 ℃ or less, the copper substrate was taken out, sonicated in 5% acetic acid for 5 minutes, rinsed with distilled water and dried with compressed air.

Example 2

The reaction was carried out under the same conditions as in Example 1, except that the average particle size of the copper powder in Example 1 was 25 μm.

Example 3

The reaction was carried out under the same conditions as in Example 1, except that the average particle size of the copper powder in Example 1 was 10 μm.

Example 4

A coating agent in which a copper powder having an average particle size of 67 μm was mixed at a weight ratio of butane and 5: 1 was uniformly applied onto a copper substrate. The coating on the copper substrate was sintered in a sintering furnace to form a coating layer having a thickness of 296 μm, and then cooled in a furnace. After the sintering process, the copper substrate was washed with 5% acetic acid followed by acetone in a sonication bath and then rinsed with distilled water to coat the copper substrate. Thereafter, heat flux was applied above the horizontal surface.

Example 5

The reaction was performed under the same conditions as in Example 4, except that the thickness of the coating layer in Example 4 was 360 μm.

Example 6

The reaction was performed under the same conditions as in Example 4, except that the thickness of the coating layer in Example 4 was 428 μm.

Comparative Example 1

An uncoated copper substrate was prepared.

Experimental Example 1

1 and 2 show that a large number of reentrant-type cavities were formed by the coating according to Example 4. It was found that the copper particles were firmly fixed because they were surface coated by sintering the copper particles.

Experimental Example 2

Critical heat flux (CHF) and boiling heat transfer coefficient of the copper substrate coated according to Examples 1 to 3 are shown in FIGS. 3 and 4 in comparison with Comparative Example 1. It was found that the particle size and thickness at which the critical heat flux and the boiling heat transfer coefficient were increased to the maximum were 67 μm and 296 μm, respectively.

Experimental Example 3

The boiling heat transfer curve when the heat flux is given above the horizontal surface of the copper substrate coated by Example 4 is shown in FIG. In the case of coating, the critical heat flux increased about 2 times and the boiling heat transfer coefficient increased 3 to 8 times.

Experimental Example 4

The heat flux is measured at 90 °, 135 °, and 180 ° to change the angle at which the heat flux is applied to the copper substrate coated by Example 4 and the copper substrate according to Comparative Example 1, and is shown in FIG. 6. It can be seen that the coating on the surface significantly increases both the critical heat flux and the boiling heat transfer coefficient, and in particular, the critical heat flux is about 1.4 MW / m ² even when the heat flux is applied to the bottom of the horizontal surface (180 °). Could.

Experimental Example 5

The results of applying the method according to Example 4 and Comparative Example 1 to the actual APR1400 reactor are shown in FIG. 8. As a result of comparing the critical heat flux according to the angle at which the heat flux is applied (90 ° to 180 °), it was confirmed that the critical heat flux of the reactor including the sintered layer was high at all measurement angles.

Through the above experimental examples, it was found that when the copper particles were sintered to the copper substrate, the critical heat flux and the boiling heat transfer coefficient were significantly increased as compared with the case where the copper particles were not sintered. When applied to the reactor vessel, in the event of a serious accident that the core is melted, the core melt is rapidly cooled through the copper particle sintered layer coated on the outer wall of the reactor in accordance with an embodiment of the present invention to prevent melt damage of the reactor vessel and nuclear power safety It can be seen that can be improved.

It is intended that the invention not be limited by the foregoing embodiments and the accompanying drawings, but rather by the claims appended hereto. Accordingly, various forms of substitution, modification, and alteration may be made by those skilled in the art without departing from the technical spirit of the present invention described in the claims, which are also within the scope of the present invention. something to do.

1: core melt
2: coolant
10: reactor vessel
11: sintered layer
15: reactor cavity
20: shielded container
30: containment

Claims (9)

Preparing a coating agent containing copper particles having an average diameter of 10 to 67 μm (step 1);
Applying the coating to the surface of the reactor vessel outer wall (step 2); And
Sintering the coating to form a sintered layer having a thickness of 78 to 428 μm for cooling the reactor vessel outer wall (step 3),
And the sintered layer comprises a reentrant-type cavity.
delete delete The method of claim 1,
The sintered layer,
A method for producing a reactor vessel, characterized in that the porosity is 0.6 to 0.7.
The method of claim 1,
The copper particles,
Reactor container manufacturing method characterized in that it contains 70 to 90% by weight based on 100% by weight of the coating agent.
A copper particle sintered layer having a thickness of 78 to 428 μm for cooling the reactor vessel outer wall on the outer wall surface,
The copper particles have an average diameter of 10 to 67 ㎛,
The sintered layer is a reactor vessel, characterized in that it comprises a recess hole.
delete delete The method of claim 6,
The sintered layer,
A reactor vessel having a porosity of 0.6 to 0.7.

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