JP6065458B2 - Metal grating for use in reactor containment - Google Patents

Description

  The present invention is a nuclear reactor that does not cause coating peeling or significant corrosion in a non-stationary environment of high-pressure hot water that is hypothesized at the time of design in a nuclear reactor containment vessel, and is excellent in corrosion resistance in a steady use environment. The present invention relates to a metal grating used in a containment vessel.

  Metal gratings have been used in the gas phase part of nuclear reactor containment vessels. Metallic gratings are normally used in the gas phase, and are required to have corrosion resistance and scratch resistance because they are used as a work floor.

  In the unsteady environment of high-pressure hot water assumed at the time of the containment design accident, a large amount of cooling water circulates to cool the inside of the container. The coating film that peels off under that condition is calculated as a foreign substance that places a load on the circulation pump.

  JEAG 4628-2010 “Guidelines for Coating in the Reactor Containment Vessel” is for evaluating the peelability in the unsteady environment of high-pressure hot water at about 170 ° C. for the coating film used in the reactor containment vessel. Tests simulating radiation and high-temperature and high-pressure hydrothermal environments are prescribed.

  Because of these required characteristics, the coating of unpainted hot-dip galvanized steel that has been inexpensive and excellent in these characteristics and does not peel in an unsteady environment has been used for a long time.

  However, as a non-stationary environment assumed at the time of the design accident of the containment vessel, when hot dip galvanizing is exposed to hot water or steam at a high temperature of 120 ° C to 170 ° C, corrosion rapidly progresses, resulting in a white zinc corrosion product. Turned out to produce. If the hot dip galvanized steel grating is exposed to an unsteady environment due to a decrease in cooling function in the reactor containment vessel, the replacement of the grating due to the loss of galvanization or a large amount of white zinc corrosion products during subsequent recovery The inside of the containment vessel needs to be cleaned due to the occurrence of this, and there is a concern about the adverse effect on the stability of the gas composition of the gas phase atmosphere in the containment vessel due to the corrosion reaction.

  In order to solve the above problems, the present invention does not cause coating peeling or significant corrosion in the unsteady environment of high-pressure hot water imaginary at the time of design, and is excellent in scratch resistance and corrosion resistance in a steady use environment. Another object of the present invention is to provide a metal grating that can be used for a long time.

  In order to achieve the above-mentioned object, the present inventors paid attention to strong steel materials and stainless steel materials because grating is also used to suspend and install heavy objects as a work floor. And about these steel materials, the corrosion test and the peeling test were done in the environment of high-temperature hot water or steam, and various knowledge was acquired and this invention was reached | attained.

  That is, the present invention is as follows.

(1) a steel material subjected to hot dipping containing 100 g / ^{m 2} or more 1000 g / ^{m 2} less than zinc or aluminum or 97Mass% as a base material,
A chemical conversion coating is provided on the surface,
Furthermore, a metal used in a reactor containment vessel having excellent hot water resistance and corrosion resistance, characterized in that an epoxy resin coating film having a thickness of 50 μm or more and less than 1000 μm that does not contain metal powder as an anticorrosive pigment is provided on the upper layer. Made of grating.

(2) The metal grating according to (1) above, wherein the thickness of the epoxy resin coating film is 100 μm or more and less than 1000 μm.

(3) The metal grating according to the above (1) or (2), wherein the chemical conversion treatment is a chromate treatment or a zinc phosphate treatment.

(4) A nuclear reactor containment vessel in which the metal grating according to any one of the above (1) to (3) is disposed at an appropriate position in the reactor containment vessel.

  The metallic grating in the reactor containment vessel of the present invention is excellent in corrosion resistance and scratch resistance in a steady use environment, and can be used for a long period of time including work for handling heavy objects like conventional gratings. is there. Moreover, corrosion and peeling of the coating film do not occur even in an unsteady environment of high-pressure hot water imaginary at the time of design. As a result, it is possible to reduce the load on the circulating pump in the container in an emergency, improve the stability of the atmosphere in the containment vessel, and to repair, replace, and clean the grating when returning from the emergency to the steady state. Reduction is also possible.

The present invention is directed to metal gratings used in a reactor containment vessel. The substrate of the grating is generally structural rolled steel material stipulated in JIS G 3101 from the standpoint of the strength and the establishment of the weight of the working floor.

  In the present invention, an epoxy resin-based coating film that does not contain metal powder as a rust-preventing pigment is formed by an epoxy resin-based paint mainly composed of an epoxy resin. Examples of such epoxy resin-based paints include those in which an epoxy resin, a curing agent, and other additives are blended. A main agent and a curing agent for various known epoxy resins can be used, and the kind thereof is not particularly limited.

In addition , the coating film containing a metal zinc powder and / or a metal aluminum powder is formed by the rust preventive coating material containing a metal zinc powder and / or a metal aluminum powder as a rust preventive pigment. As the metal zinc powder and metal aluminum powder, zinc powder having a particle diameter of about 1 to 50 μm, aluminum powder, scaly zinc powder having a major axis of about 1 to 50 μm, scaly aluminum powder, etc. are generally used. . The shape of these metal powders is preferably a scaly shape from the viewpoint of having high corrosion resistance even when the thickness of the coating film is reduced. Examples of the rust preventive paint include zinc rich paint and rust preventive paint to which an aluminum filler is added. Zinc rich paint is a paint containing about 70% by mass or more of metallic zinc powder in the coating film, and an organic zinc rich paint using an organic spreading agent and an inorganic zinc rich paint using an inorganic spreading agent. There is. Known organic and inorganic spreading agents can be used, and the kind thereof is not particularly limited. Examples of organic spreading agents include epoxy resins and alkyd resins, and examples of inorganic spreading agents include alkali silicates. A paint in which metallic aluminum powder is mixed with zinc rich paint may also be used.

  The above-mentioned coating film should be dried at room temperature after applying an epoxy resin paint or rust preventive paint by a general painting method such as spray coating using airless spray or air spray, brush coating, roller coating, etc. Can be formed. Moreover, a coating film can be firmly formed by baking after coating and making it harden | cure.

  Next, the form for implementing this invention is demonstrated in detail.

(Embodiment 1: Grating based on steel material subjected to hot dipping)
In the present embodiment, sub Namarima others to the steel subjected to hot dipping containing aluminum as a base material. Grating with anti-corrosion by metal plating can be used for parts where damage in the depth direction from the metal surface is about several tens of microns and a wide damage of 5 mm or more is expected at work, which is advantageous in terms of cost. It becomes.

Metal plating on the steel material surface, it is necessary to include zinc and aluminum can be expected sacrificial protection effect on steel, to grant corrosion resistance under steady use environment, nitrous Namarima other aluminum 5 It is preferable to contain 0 mass% or more, and more preferably 97 mass% or more. In addition to zinc and aluminum, the metal to be plated may contain a metal such as tin or magnesium less than 50 mass%, more preferably less than 3 mass%.

Adhesion amount alone molten plating metal zinc or aluminum, it is necessary from the viewpoint of imparting corrosion resistance for a long period of time 100 g / m ² or more. On the other hand, when the adhesion amount of the hot dip metal is increased, the effect is saturated, and when the adhesion amount is 1000 g / m ² or more, there is a concern about unevenness of the plating surface and distortion of the steel material.

  As described above, a steel material subjected to hot dip plating containing zinc or aluminum is corroded in a high temperature steam environment. The grating according to the present invention is provided with a chemical conversion treatment film on the surface of the hot-dip plated steel material, and further provided with an epoxy resin coating film having a predetermined thickness not including metal powder as a rust preventive pigment on the upper layer. Corrosion can be suppressed. When an epoxy resin-based paint that does not contain metal powder is applied to the hot-dip plated steel material, it is necessary to provide an epoxy resin-based coating film having a dry film thickness of 50 μm or more, more preferably 100 μm or more. When the thickness of the coating film is less than 50 μm, the steel material is easily corroded by being exposed to a high temperature steam environment assuming a non-stationary environment (hot water test). On the other hand, when the thickness of the coating film is 1000 μm or more, the coating film peels off after the hot water test. In addition, when an epoxy resin-based paint containing metal powder is applied on the outermost surface, the coating film becomes brittle and tattered when exposed to a high-temperature steam environment.

  On the other hand, when the surface of the hot-dip plated steel is left as plated, or when it is lightly blasted so that the hot-dip plating does not peel off, the coating film coated with an epoxy resin paint is used. In the hot water test, peeling occurs. However, a chemical conversion treatment is applied to the surface of the hot dipped steel, and a chemical conversion treatment film is provided on the surface, and an epoxy resin paint having a dry film thickness of 50 μm or more and less than 1000 μm is applied to the surface. Corrosion is suppressed without causing coating film peeling.

  Examples of the chemical conversion treatment include chromate treatment, zinc phosphate treatment, iron phosphate treatment, chromium phosphate treatment, and the like. In particular, the film formed by chromate treatment or zinc phosphate treatment has excellent adhesion and corrosion resistance with epoxy resin paints, so that corrosion resistance is not exerted on hot-dipped steel materials without causing film peeling even in high-temperature steam environments. Can be granted. The thickness of the chemical conversion coating is not particularly limited. Adhesion of epoxy resin coatings to hot dipped steel can be sufficiently enhanced, and by protecting the surface of hot dipped steel with epoxy resin coatings, hot water resistance and corrosion resistance can be imparted to hot dipped steel From this point of view, it is desirable that the chemical conversion coating covers the entire surface. The concentration, temperature, and treatment time of the treatment liquid are appropriately adjusted so that the chemical conversion treatment film covers the entire base.

  In addition, it is preferable to wash | clean a hot dipped steel material as a pre-process of chemical conversion treatment, and to remove the surface stain | pollution | contamination, an oxide film, etc.

In the first embodiment, the coating form for making the metal grating excellent in hot water resistance and corrosion resistance has been described for the two types of materials. However, when the metal grating is used for the work floor in the containment vessel, the water content depends on the work contents. Sometimes it gets wet. From the viewpoint of anti-slip, when the epoxy resin-based coating film is the outermost surface, it is desirable to use an anti-slip paint provided with appropriate irregularities on the surface. Non-slip method is to apply epoxy resin paint containing anti-slip agent, or to spray anti-slip agent with proper shape on the surface before the epoxy resin-based coating dries. Any method of fixing the inhibitor may be used.

  The metal gratings of the present invention are both excellent in hot water resistance and corrosion resistance. According to the characteristics of each material, the metal gratings are excellent in economic efficiency and long-term by being disposed at appropriate positions in the reactor containment vessel. It will be in service.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example and a comparative example, this invention is not limited only to a following example.

  The produced metal grating was subjected to a steady-state corrosion resistance test, a 140 ° C. corrosion resistance test, a slip test, a hot water test, and a scratch resistance test by the following methods.

[Standing corrosion resistance test]
We investigated rusting during long-term service in a steady environment. Water was regularly sprayed on the metal grating in the laboratory, and the state of corrosion of the substrate and peeling of the coating film after 6 months was confirmed. As for the coating test material, a soot reaching the base metal was put on the surface, and the spread of corrosion from the soot portion was confirmed.
If the surface corrosion or the spread of corrosion from the coating film is not confirmed, it is judged as “good”, the area of rusting or swelling of the coating film is less than 2%, or the progress of corrosion under the coating from the heel part is 1. If the deformation is within 0mm and can be used continuously, it is marked as "Yes", the area of rusting and swelling of the coating is 2% or more, or the progress of corrosion under coating from the heel is 1.0mm Exceeding the steady use, the corrosion is expanded and the long-term continuous use is a concern, and it was judged as “No”.

[140 ° C corrosion resistance test]
The effect on the gas phase and continued use due to repair depend on the corrosion of the substrate and the state of peeling of the coating. Therefore, after exposure to steam at 140 ° C for 48 hours, corrosion products and corrosion below the coating It was evaluated whether or not such changes were observed.
“Good” indicates that the surface does not show any deformation such as corrosion products or corrosion under the coating film, and “Yes” indicates that the surface of the deformation is repaired with less than 10% and can be used continuously. A case where the deformation area was 10% or more and there was a concern about the influence on the gas phase portion during corrosion or the continued use after repair was judged as “impossible” as x.

[Slidability test]
Glidability when used as a work floor was evaluated by ASTM E303 using a British portable skid resistance tester.
In BNP (British Pundulum Number), 40 or more was judged as “good”, “less than 40” was judged as “good”, and less than 40 was judged as “good”, and less than 5 was judged as “impossible”.

[Hot water test]
In order to prevent the adverse effect on the strainer, the hot water resistance of the coated steel material was evaluated under the conditions specified in JEAG 4628-2010 “Guidelines for Coating in Reactor Containment Vessels”. The case where the coating film was not peeled was judged as “good” as “good”, and the case where the coating film was peeled off was judged as “impossible” as x.

[Scratch resistance test]
About coated steel materials, when used as a work floor, as a rust resistance when metal objects such as tools fall, a steel weight of 300g is dropped from a height of 0.5m, and depending on the presence or absence of wrinkles reaching the base Scratch resistance was evaluated. In the drop test, the case where there was no wrinkle was judged as “good” as “good”, and the case where there was a wrinkle was judged as “impossible” as x.

(Examples 1 to 3 , Comparative Examples 1 to 8)
As hot dipping steel as a base material, galvanized steel, Oh Rui using molten aluminum plating steel.

<Chemical conversion treatment>
A chemical conversion film was prepared by the following method.
1) Chemical conversion treatment of zinc phosphate system on hot dip galvanized surface is degreasing (using Nippon Paint "Surf Cleaner") → water washing → surface conditioning (using Nippon Paint "Surf Fine") → water washing → phosphoric acid Zinc-based chemical conversion treatment (using “Surf Cleaner” manufactured by Nippon Paint) → washing with water → drying was performed.
2) The chromate-based chemical conversion treatment on the hot dip galvanized surface was carried out in the order of degreasing (same as above) → water washing → acid washing → water washing → chromic acid treatment → water washing → drying.
3) The conversion treatment to the molten aluminum plating surface was the same chromate conversion treatment as in 2) above.

  For comparison, a test material that was subjected to sweep blasting using a spinel-based abrasive to such an extent that the metallic luster of the plating surface disappeared, and a test material that had been untreated as hot-plated were used.

<Paint>
The epoxy resin-based paint was spray-coated with Dainippon Paint Eponics (indicated by “Ep” in the table). A non-slip type epoxy resin paint that imparts anti-slip as a work floor was coated with a Chinese paint high floor 930 (indicated by “NS-Ep” in the table).

  Table 1 shows the evaluation results of the metal gratings produced in the examples and comparative examples.

From the results of Table 1, the composition of the plating metal, zinc or aluminum that sacrificial protection exerted on the steel material can be expected, the inclusion in the plating layer, good results have been obtained at corrosion tests at steady state and 140 ° C. I understand that.

The adhesion amount of zinc or aluminum is required to be 100 g / m ² or more from the viewpoint of long-term corrosion prevention. When the adhesion amount is small (Comparative Example 1), the anticorrosion effect at the steady state is inferior. On the other hand, when the adhesion amount is 1000 g / m ² or more (Comparative Example 3), the anticorrosion effect is saturated, and there are concerns about unevenness on the plating surface and distortion of the steel material.

  Moreover, when the dry film thickness of a coating film is less than 50 micrometers (comparative example 5), the evaluation in a 140 degreeC corrosion resistance test is inferior, and as shown in an Example, the epoxy resin-type coating material with a dry film thickness of 100 micrometers is shown. It can be seen that by forming the coating film, corrosion of the plating layer in a high-temperature steam environment can be suppressed. On the other hand, when the dry film thickness of the coating film of the epoxy resin coating is 1000 μm or more (Comparative Example 4), an example in which the coating film peels after the hot water test is observed is not preferable.

  When the surface of the hot dip plated steel material is left as plated without being subjected to chemical conversion treatment (Comparative Example 2), or when a mild blasting treatment is performed (Comparative Example 7), evaluation in a 140 ° C. corrosion resistance test Is inferior, and the coated film peels off in a high temperature steam environment. This shows that it is necessary to perform chemical conversion treatment such as chromate treatment and zinc phosphate treatment on the plating surface before coating. When an epoxy resin-based paint containing metallic zinc powder is applied (Comparative Example 8), the coated film becomes tattered in a high-temperature steam environment, so it may be necessary to form a coated film that does not contain metallic zinc. Recognize.

Claims (4)

A steel material subjected to hot dipping including 97 mass% or more of zinc or aluminum of 100 g / m ² or more and less than 1000 g / m ² is used as a base material.
A chemical conversion coating is provided on the surface,
Furthermore, a metal used in a reactor containment vessel having excellent hot water resistance and corrosion resistance, characterized in that an epoxy resin coating film having a thickness of 50 μm or more and less than 1000 μm that does not contain metal powder as an anticorrosive pigment is provided on the upper layer. Made of grating. The metal grating according to claim 1, wherein the thickness of the epoxy resin coating film is 100 µm or more and less than 1000 µm. The metal grating according to claim 1 or 2, wherein the chemical conversion treatment is a chromate treatment or a zinc phosphate treatment. A nuclear reactor containment vessel in which the metal grating according to any one of claims 1 to 3 is disposed at an appropriate location in the reactor containment vessel.