JP2001083284A - Heat-transfer pipe for feedwater heater, feedwater using such heat-transfer pipe and method for manufacturing such hear-transfer pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively restrain the elution of chromium by composing a heat-transfer pipe of stainless steel containing chrome and forming a nickel ferrite oxide film with a specific on the surface of the heat-transfer pipe. SOLUTION: A gas 5 as a treatment medium is fed from a supply pipe 3 by placing a hollow pipe that is formed through such processes as dissolving, ingot-making, rolling and pickling with stainless steel containing chromium and a heat-transfer pipe 2 in an electric furnace 1. In other words, the temperature in the electric furnace 1 is set at 220 deg.C or higher inject the gas 5 (for example, air) whose oxide concentration is 20 to 100% from a gas inlet 3a and effuse the gas 5 from a gas outlet 3b. The effused gas 5 is continuously or intermittently supplied to the inner and outer peripheral surfaces of the heat-transfer pipe 2 whose surface is treated in the pickling process. As a result, an nickel-ferrite oxide film is generated on the surface of the heat-transfer pipe 2. The thickness of the film is set at 0.01 to 5 μm. If the thinner than 0.01 μm, in this case, the effect of the restraint on the elution of chromium is insufficient. If the thickness is 5 μm or thicker, it takes excess time for treatment because the thickness includes an unnecessary part. An especially effective thickness is 0.1 to 3 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feed water heater provided in a nuclear power plant or the like, a heat transfer tube of the feed water heater, and a technique for manufacturing the heat transfer tube. The present invention relates to a heat transfer tube for a feed water heater, which can effectively suppress the elution of chromium, a feed water heater using the heat transfer tube, and a method for manufacturing the heat transfer tube.

[0002]

2. Description of the Related Art Generally, stainless steel containing chromium (Cr) is applied to a heat transfer tube of a feed water heater provided in a nuclear power plant. Conventionally, as this heat transfer tube,
After the extrusion step or the drawing step in the production stage, a pickling treatment is performed to use an acid-free coating on the surface.

However, it has been found that in such equipment using a heat transfer tube of a feed water heater having no oxide film on the surface, a large amount of chromium elutes from the surface of the heat transfer tube during operation of the reactor. According to recent research, increasing the amount of chromium in the reactor increases the amount of Co-60 ions in the reactor water, and points out problems such as deterioration of equipment performance due to chromium adhering to equipment in the reactor. Have been.

[0004] In order to reduce the amount of chromium in the reactor, it is necessary to suppress the elution of chromium from the heat transfer tube of the feed water heater, which is the main source. Not been. As a known technique similar to chromium elution suppression, there has been proposed a technique of forming an oxide film on the surface of a heat transfer tube in a high-temperature atmosphere to thereby suppress the elution of cobalt (for example, Japanese Patent Application Laid-Open No. 62-858).
94, JP-A-61-245094, etc.).

[0005]

However, in the above-mentioned prior art, chromium elution from the heat transfer tube of the feed water heater is not always sufficient, for example, the formation of an oxide film is unstable and the obtained film thickness is not uniform. Can not be suppressed. For this reason, the heat transfer tube of the feed water heater is still one of the main sources of cobalt, the main element of the main nuclide Co-60 in nuclear power plants.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a heat transfer tube for a feed water heater and a feed water heater using the heat transfer tube, in which elution of chromium can be effectively suppressed. It is in.

Another object of the present invention is to form a nickel ferrite oxide film layer on the surface of a heat transfer tube as a means for suppressing chromium elution, and to form the nickel ferrite oxide film layer uniformly and efficiently at that time. It is an object of the present invention to provide a method for manufacturing a heat transfer tube for a feed water heater which can be used.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a heat transfer tube for a feed water heater made of chromium-containing stainless steel, the surface of which has a thickness of 0 mm. Provided is a heat transfer tube for a feed water heater, wherein a nickel ferrite oxide film having a thickness of 0.01 to 5 μm is formed.

According to the heat transfer tube for a feed water heater of the present invention, elution of chromium from the heat transfer tube in the feed water heater during operation can be effectively and stably suppressed. That is, under the prior art, the type and thickness of an effective oxide film as a means for suppressing chromium elution from a heat transfer tube for a feed water heater were not always clear, but a nickel ferrite having a thickness of 0.01 to 5 μm was not clear. According to the heat transfer tube having the oxide film formed thereon, chromium elution from the heat transfer tube can be extremely effectively suppressed.

[0010] If the thickness of the nickel ferrite oxide film is less than 0.01 µm, the required effect of suppressing chromium elution is not sufficiently exhibited. Conversely, if the thickness exceeds 5 μm, the thickness becomes unnecessary, and extra processing time is required. In the present invention, particularly effective nickel ferrite oxide film thickness is,
It is in the range of 0.1 to 3 μm.

According to a second aspect of the present invention, there is provided a feed water heater installed in a water supply system of a nuclear reactor, wherein the feed water heater is constituted by using the heat transfer tube according to the first aspect.

According to the present invention, it is possible to effectively reduce the amount of chromium in a nuclear reactor and, consequently, reduce Co-60 ions.
Problems such as deterioration of equipment performance in the nuclear reactor can be solved.

By the way, under the processing conditions by the conventional cobalt suppression technology, the thickness of the oxide film is generally thin, and the effect of suppressing chromium is low. Therefore, it is necessary to thicken the oxide film, but under the conventional processing conditions according to the above-described known techniques and the like, the generation rate of the oxide film is low,
There is a problem that it takes much time to form an oxide film having a required thickness. Also, because there is no convection of the atmosphere gas,
There is also a problem that the oxide film becomes non-uniform and the effect of suppressing chromium elution of the heat transfer tube is not constant.

Therefore, according to the manufacturing method of the present invention, when a nickel ferrite oxide film layer is formed on the surface of the heat transfer tube,
An object of the present invention is to improve a heating condition or a heating method so that a nickel ferrite oxide film layer can be formed uniformly and efficiently.

According to the third aspect of the present invention, after a hollow tube is manufactured from a chromium-containing stainless steel through steps such as melting, ingot-forming, and rolling, the hollow tube is manufactured under a processing medium atmosphere having an oxygen concentration of 20 to 100%. The present invention provides a method for manufacturing a heat transfer tube for a feed water heater, which comprises performing a surface treatment of heating to 220 ° C. or more.

According to the present invention, it is possible to cope with shortening of a processing time for obtaining a thickness of a nickel ferrite oxide film necessary for suppressing chromium elution of a heat transfer tube material for a feed water heater. That is, the thickness of the nickel ferrite oxide film having the effect of suppressing chromium elution of the heat transfer tube for the feed water heater is 0.01 μm or more. In order to obtain this nickel ferrite oxide film thickness, the present invention promotes oxidation of the heat transfer tube surface by supplying a large amount of oxygen, thereby increasing the generation rate of the ferrite oxide film and shortening the processing time. be able to. If the oxygen concentration in the atmosphere of the processing medium is less than 20%, the oxidation becomes insufficient. The heating temperature is 220 ° C
If it is lower than this, a sufficient effect cannot be obtained at a use temperature of the feed water heater corresponding to this temperature.

According to a fourth aspect of the present invention, in the method for producing a heat transfer tube for a feed water heater according to the third aspect, the treatment medium may be:
Provided is a method for manufacturing a heat transfer tube for a feed water heater, characterized by using air or steam, or those obtained by adding ozone or hydrogen peroxide thereto.

According to the present invention, the processing time can be further reduced. That is, in the case of water vapor, the substance itself functions as an oxidizing agent, and when ozone or hydrogen peroxide is added to air or water vapor, the functions of these oxidizing agents are enhanced. For this reason, oxidation of the heat transfer tube surface can be further promoted as compared with the case where oxygen is used alone. Thereby, the generation speed of the nickel ferrite oxide film can be increased, and the processing time can be further reduced.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a heat transfer tube for a feed water heater according to the third aspect, wherein the processing medium is passed through high-frequency plasma for use. .

According to the present invention, the processing time can be further reduced. That is, oxygen in the processing medium is radicalized by passing high-frequency plasma, thereby increasing the function as an oxidizing agent and promoting oxidation of the surface of the heat transfer tube as compared with the case of using oxygen alone.
Thereby, the generation rate of the nickel ferrite oxide film can be increased, and the processing time can be shortened.

According to a sixth aspect of the present invention, in the method for manufacturing a heat transfer tube for a feed water heater according to the third aspect, a pure water having a dissolved oxygen concentration of 200 ppb or more is used as a treatment medium. Provide a way.

According to the present invention, the thickness of the nickel ferrite oxide film required for suppressing the elution of chromium in the heat transfer tube material for the feed water heater can be made uniform. In the case of the present invention, although the processing time becomes longer, a more uniform oxide film can be formed as compared with the case where the processing is performed in the still air or in the steam. The reason why the dissolved oxygen concentration of pure water is specified as described above is that if the concentration is less than 200 ppb, a dense oxide film cannot be obtained.

According to a seventh aspect of the present invention, in the method for manufacturing a heat transfer tube for a feed water heater according to any one of the third to sixth aspects, the heating by the electric furnace and the fluid supply of the processing medium are continuously or intermittently performed. A method for producing a heat transfer tube for a feed water heater is provided.

According to the present invention, the nickel ferrite required for suppressing the elution of chromium in the heat transfer tube material for the feed water heater as compared with the case where the processing medium is kept stationary by flowing the processing medium continuously or intermittently. Oxide film thickness can be more uniformly generated.

According to an eighth aspect of the present invention, in the method for manufacturing a heat transfer tube for a feed water heater according to any one of the third to sixth aspects, the heating by current supply to the heat transfer tube for the feed water heater and the fluid supply of the processing medium are performed. Provided is a method for manufacturing a heat transfer tube for a feed water heater, which is performed continuously or intermittently.

According to the present invention, a heating step for forming an oxide film of nickel ferrite necessary for suppressing chromium elution,
In addition, it is possible to satisfactorily cope with a process for making the thickness uniform. That is, the size of the heat treatment area can be reduced by supplying the current, and the temperature of the heat transfer tube can be made uniform. In addition, by supplying the current continuously or intermittently, a more uniform oxide film can be generated as compared with the case where the processing medium is processed at rest.

According to a ninth aspect of the present invention, in the method for manufacturing a heat transfer tube for a feed water heater according to any one of the third to sixth aspects, induction heating by a high-frequency current to the heat transfer tube for the feed water heater and fluid supply of the processing medium are performed. And a method for producing a heat transfer tube for a feed water heater, wherein the method is carried out continuously or intermittently.

According to the present invention, the same effects as those of the claims can be obtained.

According to a tenth aspect of the present invention, in the method for producing a heat transfer tube for a feed water heater according to any one of the third to ninth aspects, the heating step and the supply step of the processing medium are performed in the pickling step in the production stage. A method for manufacturing a heat transfer tube for a feed water heater, which is performed later, is provided.

According to the present invention, the thickness of each heat transfer tube can be easily made uniform by incorporating the heating and medium supply steps into the stage after the acid cleaning treatment in the manufacturing process. The thickness of the heat transfer tube can be made uniform, and variations in the thickness of each heat transfer tube can be reduced.

According to an eleventh aspect of the present invention, in the method for producing a heat transfer tube for a feed water heater according to any one of the third to ninth aspects, the heating step and the supplying step of the processing medium are performed in a hydrogen atmosphere in the production stage. Provided is a method for manufacturing a heat transfer tube for a feed water heater, which is performed immediately after the final heat treatment step.

According to the present invention, the heating step is included in the step after the final heat treatment in the hydrogen atmosphere in the manufacturing step, so that the thickness of the heat transfer tube is made uniform and one heat transfer tube is provided.
Variations in book thickness can also be reduced.

According to a twelfth aspect of the present invention, in the method for manufacturing a heat transfer tube for a feed water heater according to any one of the third to ninth aspects, the heating step and the supplying step of the processing medium are performed by assembling the heat transfer tube for the feed water heater. A method for manufacturing a heat transfer tube for a feed water heater, which is performed later, is provided.

According to the present invention, since the heating and medium supply steps can be performed after the production of the feed water heater, the processing time can be reduced.

[0035]

Embodiments of the present invention will be described below with reference to the drawings. In the following embodiment, for example, SUS304 is applied as stainless steel containing chromium, which is a material of the heat transfer tube for the feed water heater. However, even if the material is other than SUS304, stainless steel containing chromium can be applied in substantially the same manner.

First Embodiment (FIGS. 1 to 4) FIG. 1 is a schematic view for explaining a heat treatment step in the method for manufacturing a heat transfer tube according to the present embodiment, and FIG. 2 is a view showing a flow of all steps. It is. 3 and 4 are explanatory diagrams of the operation.

First, all steps of the manufacturing method will be described with reference to FIG. As shown in FIG. 2, in this embodiment, after the raw material melting step (S101) and the ingot making step (S102), a bar is formed by a rolling step (S103). Then, the heating step (S104) and the hot extrusion step (S1)
05), the pipe is roughly processed, and the pickling step (S106)
Surface treatment.

Next, after the cold drawing step (S107), the heat treatment step (S108) and the pickling step (S109) are repeated a required number of times, the finish drawing step (S110) is performed, and after the final heat treatment step (S111). , Pickling process (S112)
To perform the surface treatment again.

Thereafter, the heat treatment step of the present invention (S11)
3) is performed, and then a bending step (S114) is performed to complete the U-tube (S115).

Referring to FIG. 1, the details of the heat treatment step of the present invention in step S113 will be described.

As shown in FIG. 1, in this embodiment, a hollow tube as a heat transfer tube (the illustrated one is a straight tube before being bent into a U-shape, Hereinafter, all the tubes including the U-shaped one are referred to as “heat transfer tubes” 2, and a gas as a processing medium is supplied to the heat transfer tubes 2 by a supply pipe 3.
Supplied from

The supply pipe 3 has a gas inlet 3 a outside the electric furnace 1, and a heat exchange pipe section inside the electric furnace 1.
An outlet 3 toward the end of the heat transfer tube 2 and an intermediate portion on the outer peripheral surface side
b. A gas outlet 4 for discharging the blown gas out of the furnace is provided in a furnace wall portion of the electric furnace 1 away from the gas outlet 3b.

When performing the heat treatment, the temperature in the electric furnace 1 is set to 220 ° C. or higher, and a gas (for example, air) having an oxygen concentration of 20 to 100% is injected from the gas inlet 3 a.
Gas is blown out from the blowout port 3b. The blown gas 5
It is supplied continuously or intermittently to the inner and outer peripheral surfaces of the heat transfer tube 2 whose surface has been treated in the pickling step (S112) shown in FIG. As a result, a nickel ferrite oxide film is formed on the surface of the heat transfer tube 2.

FIG. 3 shows that the oxygen concentration in the gas is 20 to 100.
% In which the formation time of the nickel ferrite oxide film according to the method of the present embodiment is shown as a relative formation time with respect to the formation time of the nickel ferrite oxide film having an effect of suppressing chromium in the atmosphere. . At an oxygen concentration of 30%, it is about 0.8
And the generation time is shortened, and when the oxygen concentration is 40% or more, about 0.1% is obtained.
It can be seen that it is reduced to 6.

FIG. 4 shows the results of examining the variation (%) in the thickness of the nickel ferrite oxide film in various heating atmospheres. As apparent from FIG. 4, the variation A of the thickness of the nickel ferrite oxide film formed in the still air is about 30%, whereas the gas (oxygen concentration 40 %)
B1 when the gas (oxygen concentration 40%) is intermittently supplied under the same heating method is 10% or less, and the variation B1 when the gas is continuously supplied is less than 10%. It can be seen that it is greatly reduced as compared with.

Second Embodiment (FIGS. 1 and 5) Also in this embodiment, the heat treatment method using the electric furnace 1 shown in FIG. 1 is applied. However, as a processing medium supplied into the electric furnace 1 from the gas inlet 3a, in addition to a gas having an oxygen concentration of 20 to 100%, steam, hydrogen peroxide or ozone is injected. Alternatively, in addition to the same gas, a gas having an oxygen concentration of 20 to 100% through high-frequency plasma is injected as in the following embodiment. By using such a processing medium, a nickel ferrite oxide film is formed on the heat transfer tube 2.

FIG. 5 shows the formation time of the nickel ferrite oxide film by the method of the present embodiment as a relative formation time with respect to the formation time of the nickel ferrite oxide film having a chromium suppressing effect in the atmosphere. This figure 5
As is clear from the above, compared to C in the case of heating in the atmosphere,
When a gas with an oxygen concentration of 40% is supplied, D1 and an oxygen concentration of 4
D2 when 5% water vapor is added to 0% gas, D3 when 5% hydrogen peroxide is added, and D when ozone is added.
4 and D5 in the case of gas passed through high-frequency plasma, the generation time of the nickel ferrite oxide film is shortened, and it can be seen that each is reduced to about 0.6.

Although not shown, even if the oxygen concentration of the injected gas is variously changed in the range of 20 to 100%, or if the addition ratio of water vapor or hydrogen peroxide is variously changed, substantially the same effects as described above can be obtained. You.

Third Embodiment (FIGS. 6 and 7) FIG. 6 is a schematic diagram for explaining the heat treatment step in the method for manufacturing a heat transfer tube according to the present embodiment, and FIG. 7 is an explanatory diagram of the operation.

In this embodiment, water, for example, pure water is used as the heating medium. The dissolved oxygen concentration of this pure water is 200p
pb or more. FIG. 6 shows a superheating facility using this pure water. A heat exchanger chamber 7 is provided in a heating vessel 6 accommodating the heat transfer tube 2 via a partition wall, and water 8 is circulated in the heating vessel 6 and the heat exchanger chamber 7 by water circulation pipes 8a and 8b. Has become. The water circulation pipe 8a has a pump 9 for forced circulation.

When performing the heat treatment, the heat transfer tube 2 in the heating vessel 6 is heated by circulating water 8 at 220 ° C. or higher. The water 8 is continuously or intermittently supplied to the inner and outer peripheral surfaces of the heat transfer tube 2 which has been subjected to the surface treatment in the pickling step (S112) shown in FIG. As a result, a nickel ferrite oxide film is formed on the surface of the heat transfer tube 2.

FIG. 7 shows the results of examining the variation (%) in the thickness of the nickel ferrite oxide film formed according to this embodiment in various heating atmospheres. As is apparent from FIG. 3, the variation E in the thickness of the nickel ferrite oxide film formed in the still air is about 30%, whereas the variation in water (2
80 ° C.) and the intermittent supply F2 are both 10% or less, and it can be seen that the degree of variation is significantly reduced as compared with the conventional case. Thereby, according to the present embodiment, it can be confirmed that a uniform film is formed.

Fourth Embodiment (FIG. 8) In this embodiment, the heat treatment method using the electric furnace 1 shown in FIG. 1 is applied, and the processing medium supplied into the electric furnace 1 from the gas inlet 3a has an oxygen concentration of 20 to In addition to 100% gas, steam, hydrogen peroxide or ozone is injected continuously or intermittently. Alternatively, in addition to the gas, a gas having an oxygen concentration of 20 to 100% through high frequency plasma is continuously or intermittently injected. By using such a processing medium, a nickel ferrite oxide film is formed on the heat transfer tube 2.

FIG. 8 shows the variation (%) in the thickness of the nickel ferrite oxide film according to the method of the present embodiment as a relative generation time to the generation time of the nickel ferrite oxide film having a chromium suppressing effect in the atmosphere. Things. As is clear from FIG. 8, in the case of heating G in the still air, the thickness variation is as high as about 30%. On the other hand, when the gas having the oxygen concentration of 40% is continuously supplied, H1 is added. When the gas having the oxygen concentration of 40% is intermittently supplied every 5 minutes, H2 is added. H3 when hydrogen is supplied continuously, and 5% of hydrogen peroxide
In addition, H4 when continuously supplied, H5 when continuously supplied with ozone, and H6 when continuously supplied with gas through high-frequency plasma, the thickness variation of the nickel ferrite oxide film is not uniform. When the value is about 15% or less, the value is more than half. That is, a uniform film having small variations can be obtained.

Fifth Embodiment (FIGS. 9 and 10) In the present embodiment, heating by current supply to the heat transfer tube for the feed water heater and fluid supply of the processing medium are performed continuously or intermittently. In the present embodiment and the following sixth embodiment, the heat treatment process according to the present invention is performed after the completion of the U-shaped tube (S115), unlike the case shown in FIG.

FIG. 9 is a schematic diagram for explaining a heat treatment step in the method for manufacturing a heat transfer tube according to the present embodiment.
FIG. 10 is an operation explanatory view.

As shown in FIG. 9, a heat transfer tube 2 bent in a U-shape is arranged in a heating vessel 11 having an air layer 10, and electrodes 12 and 13 are connected to both ends of the heat transfer tube 2. Each of the electrodes 12 and 13 is connected to an externally provided power supply 14 via a wiring 15 to apply a current. The supply current is, for example, a direct current, but may be an alternating current. The supply of the heating medium 5 is performed in the same manner as in each of the above embodiments. That is, the supply pipe 3, the gas outlet 4, and the like are provided, for example, in substantially the same manner as in FIG.

During film formation, a current is supplied to the heat transfer tube 2 in the heating vessel 11 through the electrodes 12 and 13 at both ends, and gas is continuously or intermittently supplied into the heating vessel 11 from the gas inlet 3a. Supply. Thereby, a ferrite oxide film having a chromium suppressing effect is generated. The temperature conditions and the like are the same as in the above embodiments.

According to this embodiment, it is possible to satisfactorily cope with a heating step for forming an oxide film of nickel ferrite necessary for suppressing chromium elution and a step for making the thickness uniform. That is, the size of the heat treatment area can be reduced by supplying the current, and the temperature of the heat transfer tube can be made uniform. In addition, by supplying the current continuously or intermittently, a more uniform oxide film can be generated as compared with the case where the processing medium is processed at rest.

FIG. 10 shows the variation (%) in the thickness of the nickel ferrite oxide film formed according to this embodiment.
The results of examining various heating atmospheres are shown. As is apparent from FIG. 10, the variation I of the thickness of the nickel ferrite oxide film generated in the still air is about 30%, whereas the gas having the oxygen concentration of 40% is supplied under the heating method in the present embodiment. Variation J1 when supplied continuously
And the variation J2 when a gas having an oxygen concentration of 40% is intermittently supplied every 5 minutes is 10% or less, and it can be seen that the variation degree is significantly reduced as compared with the conventional case. Thereby, according to the present embodiment, it can be confirmed that a uniform film is formed.

Sixth Embodiment (FIGS. 11 and 12) This embodiment is a modification of the above-described fifth embodiment, in which the heat transfer tube 2 is induction-heated by a high-frequency current.

FIG. 11 is a schematic diagram for explaining a heat treatment step in the method for manufacturing a heat transfer tube according to the present embodiment, and FIG. 12 is an operation explanatory diagram.

As shown in FIG. 11, a coil 16 for induction heating is provided in a heating vessel 11 having an air space 10,
The heat transfer tube 2 bent in a letter shape is arranged in the coil 16. A high-frequency current is supplied to the coil 16 from a power supply 17 installed outside via a wiring 18. The supply of the heating medium 5 is performed in the same manner as in each of the above embodiments. That is, the supply pipe 3, the gas outlet 4, and the like are provided, for example, in substantially the same manner as in FIG.

During the film formation, the heat transfer tube 2 in the heating vessel 11 is induction-heated by a high-frequency current, and gas or steam is supplied into the heating vessel 11 continuously or intermittently from the gas inlet 3a. Thereby, a ferrite oxide film having a chromium suppressing effect is generated. The temperature conditions and the like are the same as in the above embodiments.

According to the present embodiment, a heating step for forming an oxide film of nickel ferrite necessary for suppressing chromium elution and a step for making the thickness uniform can be satisfactorily handled. That is, the size of the heat treatment area can be reduced by supplying the current, and the temperature of the heat transfer tube can be made uniform. In addition, by supplying the current continuously or intermittently, a more uniform oxide film can be generated as compared with the case where the processing medium is processed at rest.

FIG. 12 shows the variation (%) in the thickness of the nickel ferrite oxide film formed according to the present embodiment.
The results of examining various heating atmospheres are shown. As is apparent from FIG. 12, the variation K of the thickness of the nickel ferrite oxide film generated in the still air is about 30%, whereas the gas having the oxygen concentration of 40% is supplied under the heating method in the present embodiment. Variation L1 when supplying continuously
And the variation L2 in the case of continuously supplying a gas having an oxygen concentration of 40% and water vapor added at 5% are both around 10%, and it can be seen that the variation degree is greatly reduced as compared with the related art. Thereby, according to the present embodiment, it can be confirmed that a uniform film is formed.

Seventh Embodiment (FIGS. 13 and 14) In this embodiment, the manufacturing steps in the first embodiment (FIG. 2)
This is a modification of the first embodiment.

FIG. 13 shows a first modification.
That is, in this example, the pickling step (S112) before the heat treatment step (S113) of the present invention is omitted from the manufacturing steps shown in FIG. The other steps are the same as those in FIG. 2, so that step symbols S201 to S214 are added to FIG. 13 and the description is omitted.

FIG. 14 shows a second modification. That is, in this example, the raw material dissolving step (S30
1) After forming a bar by the ingot forming step (S302) and the rolling step (S303), the extruding step (S304) and the pickling step (S305) are performed.

Next, a rolling or drawing step (S306)
After repeating the heat treatment step (S307) and the pickling step (S308) as many times as necessary, a drawing / drawing step (S309) is performed, and a bending step (S311) is performed after the final heat treatment step (S310).

After the surface treatment is again performed in the pickling step (S312), the heat treatment step (S31) of the present invention is performed.
3) is performed, and the U-shaped tube is completed (S314).

Therefore, this example is applied to the above-described fifth and sixth embodiments.

Eighth Embodiment (FIGS. 15 to 17) In this embodiment, the heating step and the processing medium supply step are performed after the assembly of the heat transfer tube for the feed water heater.

FIG. 15 is a schematic diagram for explaining the heat treatment step in the method for manufacturing a heat transfer tube according to the present embodiment, and uses a gas as a heating medium. FIG.
FIG. FIG. 17 is a modified example of FIG. 15, in which a liquid is used as a heating medium.

In the embodiment shown in FIG. 15, in a state in which a plurality of electric heating tubes 2 are arranged in the casing 19a of the feed water heater 19, high-temperature gas is supplied to all of the heat transfer tubes 2 at a time to perform oxidation. A heat treatment for forming a film is performed. That is, the space in the casing 19 a is partitioned by the header 20, and each U-shaped heat transfer tube 2 is arranged in one space 19 b partitioned by the header 20. Both ends of each heat transfer tube 2 are open to the other space 19 c via holes formed in the header 20.

The gas supply pipe 21 has one gas inlet 21
a and gas outlets 21b and 21c branched into two,
These gas outlets 21b and 21c are connected to the casing 19a.
It opens to each space 19b, 19c inside. The gas supply pipe 21 is passed through the heater 22 and the gas inlet 2
The gas supplied from 1a is heated by the heater 22 to the same temperature as in each of the above-described embodiments, and is then blown out into the spaces 19b and 19c in the casing 19a. The casing 19a is provided with gas outlets 23a and 23b for discharging gas from the respective spaces 19b and 19c.

In such a configuration, the casing 19
When the gas 5 serving as a heating medium is supplied into a, the gas blown out from one of the gas outlets 21b of the gas supply pipe 21 heats the outer peripheral surface of the heat transfer pipe 2 and is used for forming an oxide film. The gas blown out from the other gas outlet 21c is
The heat is passed through the inner peripheral surface of the heat transfer tube 2 and the portion is heated to provide an oxide film.

FIG. 16 shows the variation (%) in the thickness of the nickel ferrite oxide film formed according to this embodiment.
The results of examining various heating atmospheres are shown. As is clear from FIG. 16, the variation M of the thickness of the nickel ferrite oxide film generated in the still air is about 30%, whereas the gas having the oxygen concentration of 40% is supplied under the heating method in the present embodiment. Variation N1 when supplied continuously
And the variation N2 in the case of continuously supplying a gas having an oxygen concentration of 40% and water vapor added at 5% is around 10%, and it can be seen that the variation degree is significantly reduced as compared with the conventional case. Thereby, according to the present embodiment, it can be confirmed that a uniform film is formed.

In the embodiment shown in FIG. 17, the construction and operation of the feed water heater are substantially the same as those in FIG. 15, but differ in that a liquid is used instead of gas. That is, the plurality of electric heating tubes 2 are connected to the casing 19 of the feed water heater 19.
In a state where the heat transfer tubes 2 are disposed in the heat transfer tube 2, a high-temperature liquid is supplied to all the heat transfer tubes 2 at a time to perform a heat treatment for forming an oxide film. That is, the space in the casing 19 a is partitioned by the header 20, and each U-shaped heat transfer tube 2 is arranged in one space 19 b partitioned by the header 20. Both ends of each heat transfer tube 2 are open to the other space 19 c via holes formed in the header 20.

The liquid supply pipe 24 has a pump 25 and is formed in a loop shape.
4a and 24b. These liquid outlets 24a, 24
b is open to each space 19b, 19c in the casing 19a. The liquid supply pipe 24 is connected to the heater 22
After the liquid is heated by the heater 22 to the same temperature as that of each of the above-described embodiments, each of the spaces 1 in the casing 19a is heated.
9b and 19c are blown out. The casing 19a is provided with liquid recirculation ports 24c and 24d for recirculating the liquid from the spaces 19b and 19c.

In such a configuration, the casing 19
When a liquid 26 as a heating medium is supplied into the liquid supply pipe 24, the liquid 26 blown out from one liquid outlet 24a of the liquid supply pipe 24 heats the outer peripheral surface of the heat transfer tube 2 and is used for forming an oxide film. The liquid blown out from the other liquid outlet 24b is passed through the inner peripheral surface of the heat transfer tube 2 and heats that portion to form an oxide film.

According to the embodiment shown in FIG.
The same effect as that of the embodiment shown in FIG. 15 is obtained.

[0083]

As described in detail above, according to the present invention, a nickel ferrite oxide film required for suppressing chromium elution can be sufficiently and uniformly formed on the surface of a heat transfer tube for a feed water heater. And by adding the oxygen concentration and the additive together with the oxygen concentration increase, it is also possible to shorten the processing time for obtaining the thickness of the nickel ferrite oxide film necessary for suppressing chromium elution of the heat transfer tube material for feed water heaters. Becomes In addition, the gas or liquid as the heat treatment medium can be made to flow uniformly or intermittently to make the nickel ferrite oxide film thickness uniform,
Further, the heating area can be reduced in size by the heating method using current and high frequency, and the thickness of the nickel ferrite oxide film can be made uniform by making the heat transfer tube temperature uniform.
Furthermore, by introducing the nickel ferrite oxide film generation process into the manufacturing process, it is possible to make the nickel ferrite oxide film thickness more uniform, and shorten the time by performing the nickel ferrite oxide film generation process after manufacturing the feedwater heater. By flowing the processing solvent continuously or intermittently, the thickness of the nickel ferrite oxide coating on the heat transfer tube can be made uniform. The heat transfer tube obtained by the method of the present invention and the feedwater heater using the same provide an excellent effect of reducing the exposure of the nuclear reactor.

[Brief description of the drawings]

FIG. 1 is a schematic view for explaining a heat treatment step in a method for manufacturing a heat transfer tube according to a first embodiment of the present invention.

FIG. 2 is a view showing a flow of all steps of the embodiment.

FIG. 3 is an operation explanatory view of the embodiment.

FIG. 4 is a diagram illustrating the operation of the embodiment.

FIG. 5 is an operation explanatory view according to a second embodiment of the present invention.

FIG. 6 is a schematic diagram for explaining a heat treatment step in the method for manufacturing a heat transfer tube according to the third embodiment of the present invention.

FIG. 7 is an operation explanatory view of the embodiment.

FIG. 8 is an operation explanatory view of a fourth embodiment of the present invention.

FIG. 9 is a schematic diagram for explaining a heat treatment step in the method for manufacturing a heat transfer tube according to the fifth embodiment of the present invention.

FIG. 10 is an operation explanatory view of the embodiment.

FIG. 11 is a view showing a modification of the fifth embodiment of the present invention.

FIG. 12 is an operation explanatory view according to the embodiment.

FIG. 13 is a view showing a seventh embodiment of the present invention.

FIG. 14 is a diagram showing a modification of FIG. 13;

FIG. 15 is a schematic diagram for explaining a heat treatment step in the method for manufacturing a heat transfer tube according to the eighth embodiment of the present invention.

FIG. 16 is an operation explanatory view of the embodiment.

FIG. 17 is a view showing a modification of FIG. 15;

[Explanation of symbols]

 Reference Signs List 1 electric furnace 2 heat transfer pipe 3 supply pipe 3a gas inlet 3b outlet 4 gas outlet 5 heating medium 6 heating vessel 7 heat exchanger room 8 water 8a, 8b water circulation pipe 9 pump 10 air layer 11 heating vessel 12, 13 electrode 14 Power supply 15 Wiring 16 Coil 17 Power supply 18 Wiring 19 Feed water heater 19a Casing 19b, 19c Space 20 Header 21 Gas supply pipe 21a Gas inlet 21b, 21c Gas outlet 22 Heater 23a, 23b Gas outlet 24 Liquid supply pipe 24a, 24b Liquid outlet 24c, 24d Liquid recirculation port 25 Pump

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) G21D 3/00 G21D 3/00 M (72) Inventor Nagayoshi Ichikawa No. 2 Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kawasaki, Kanagawa Prefecture No. 1 F-term in Toshiba Hamakawasaki Plant (reference) 4K062 AA05 BA14 BA20 EA02 FA04 FA06 FA16 FA20 GA10

Claims (12)

[Claims] 1. A heat transfer tube for a feed water heater made of chromium-containing stainless steel, wherein a nickel ferrite oxide film having a thickness of 0.01 to 5 μm is formed on a surface of the heat transfer tube. Dexterous heat transfer tube. 2. A feed water heater installed in a feed water system of a nuclear reactor, wherein the feed water heater is constituted by using the heat transfer tube according to claim 1. 3. A stainless steel containing chromium,
After manufacturing the hollow tube through the steps of melting, ingot making, rolling, etc.,
In a processing medium atmosphere having an oxygen concentration of 20 to 100%, 2
A method for producing a heat transfer tube for a feed water heater, comprising performing a surface treatment of heating to 20 ° C. or more. 4. The method for producing a heat transfer tube for a feed water heater according to claim 3, wherein the processing medium is air or steam, or a mixture of these air and ozone or hydrogen peroxide. Heat transfer tube manufacturing method. 5. The method for producing a heat transfer tube for a feed water heater according to claim 3, wherein the treatment medium is passed through high-frequency plasma for use. 6. The method for producing a heat transfer tube for a feed water heater according to claim 3, wherein the dissolved oxygen concentration in the treatment medium is 200 ppb.
A method for producing a heat transfer tube for a feed water heater, comprising using pure water as described above. 7. The method for producing a heat transfer tube for a feed water heater according to claim 3, wherein the heating by the electric furnace and the fluid supply of the processing medium are performed continuously or intermittently. Of manufacturing heat transfer tubes for feed water heaters. 8. The method for manufacturing a heat transfer tube for a feed water heater according to any one of claims 3 to 6, wherein heating by current supply to the heat transfer tube for the feed water heater and fluid supply of the processing medium are performed continuously or intermittently. A method for producing a heat transfer tube for a feed water heater, the method comprising: 9. The method for manufacturing a heat transfer tube for a feed water heater according to any one of claims 3 to 6, wherein induction heating by a high-frequency current and fluid supply of a processing medium are continuously or intermittently applied to the heat transfer tube for the feed water heater. A method for producing a heat transfer tube for a feed water heater, comprising: 10. The method for producing a heat transfer tube for a feed water heater according to any one of claims 3 to 9, wherein the heating step and the supply step of the processing medium are performed after the pickling step in the production stage. Method for manufacturing a heat transfer tube for a feed water heater. 11. The method for manufacturing a heat transfer tube for a feed water heater according to any one of claims 3 to 9, wherein the heating step and the supply step of the processing medium are performed immediately after the final heat treatment step in a hydrogen atmosphere in the manufacturing stage. A method for producing a heat transfer tube for a feed water heater, comprising: 12. The method for producing a heat transfer tube for a feed water heater according to any one of claims 3 to 9, wherein the heating step and the supplying step of the processing medium are performed after the heat transfer tube for the feed water heater is assembled. Method for manufacturing a heat transfer tube for a feed water heater.