JP2011047667A - Nuclear reactor pipe and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide nuclear reactor pipes efficiently controlling the elution of a metal to cooling water and the growth of oxidized film, and a method for manufacturing the same. <P>SOLUTION: The pipes 27, 29, 30 composing a nuclear reactor are characterized in that a coating film composed of zirconium titanate, in which the atomic ratio of titanium and zirconium is 1:1, is formed in at least one part of the inner surface. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pipe constituting a nuclear reactor and a method for manufacturing the same, and more particularly to a reactor pipe and a method for manufacturing a reactor pipe in which elution of corrosion products and film growth are suppressed by coating.

In the piping of boiling water reactor (BWR) and the primary system piping of pressurized water reactor (PWR), a trace amount of metal dissolved from the inner surface of the wetted pipe may adhere to the fuel cladding tube of the core. is there. Further, the adhered metal may be activated by being irradiated with neutrons and then released into the cooling water and reattached to the wetted surface of the pipe to increase the radiation dose rate on the pipe surface.
Further, it is known that the activated metal is taken into the oxide film formed on the wetted surface by high-temperature water when it reattaches to the wetted surface of the pipe.
For this reason, the radiation dose rate on the pipe surface can be lowered by suppressing the elution of the metal into the cooling water and the growth of the oxide film.

  On the other hand, since the secondary piping of the pressurized water reactor (PWR) is completely cut off from the primary piping, the radiation dose rate as described above does not increase. However, in order to solve the problem of deterioration due to corrosion, it is required to suppress metal elution and oxide film growth even in the secondary piping.

As a conventional technology that suppresses metal elution and oxide film growth in such pipes, the pipes are exposed to high-temperature water or steam prior to actual use to improve the corrosion resistance by applying a surface oxide film in advance. There is a method (for example, Non-Patent Document 1).
In addition, a technique is known in which semiconductor oxide fine particles are attached to a pipe to suppress stress corrosion cracking (SCC) by a photocatalytic reaction (for example, Patent Document 1).

JP 2001-228289 A

ASAY R H, et al., Trans Am Nucl Soc, Vol.55, P.560-561 (1987) JST #: E0387B

However, in the technique of Non-Patent Document 1 in which a surface oxide film is applied in advance, since the inherent corrosion resistance of the metal is used, a dramatic improvement in corrosion resistance cannot be expected.
Also, in the technique of Patent Document 2 in which semiconductor oxide fine particles are adhered, since most of the liquid contact surface of the pipe is exposed, the effect of drastically suppressing metal elution and film growth cannot be expected.

  The present invention has been made to solve such problems, and provides a reactor pipe and a method for manufacturing the reactor pipe that effectively suppress the elution of metal into cooling water and the growth of an oxide film. With the goal.

  The reactor pipe according to the present invention is a pipe constituting the nuclear reactor, and a coating film made of zirconium titanate having an atomic ratio of titanium and zirconium of 1: 1 is formed on at least a part of the inner surface. It is characterized by being.

  According to the present invention, it is possible to prevent the metal from eluting from the wetted surface of the piping that circulates the cooling water to the reactor, and to suppress the growth of the oxide film, thereby reducing the radiation dose rate on the surface of this piping. A reactor pipe and a method for manufacturing the reactor pipe are provided.

Schematic of a boiling water reactor (BWR) system. Schematic of a pressurized water reactor (PWR) system.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
First, a nuclear reactor system to which the nuclear reactor piping according to the present invention is applied will be described with reference to FIGS. 1 and 2. In a boiling water reactor (BWR) system 10 (hereinafter referred to as a BWR system 10) shown in FIG. 1, a pressure vessel 11 contains a core 14 made of a fuel assembly and cooling water, and is further connected to various pipes. Connected. The core 14 is supported by the core shroud 12, and cooling water is circulated from the outside to the inside of the core shroud 12 by the jet pump 13.

The steam generated in the core 14 is adjusted by the moisture separator 15 and the steam dryer 16 and then introduced into the turbine 18 through the main steam pipe 17.
The thermal energy of the introduced steam is converted into kinetic energy for rotating the turbine 18, and then converted into electrical energy in a generator (not shown). The steam that has passed through the turbine 18 is reduced in temperature and pressure, and further condensed in the condenser 19 to become condensed water.
This condensed water is removed from the corrosion eluate (metal ions) eluted upstream by the condensate purification system 23, and then fed to the feed water heater 25 by the condensate pump 24 as feed water and heated. Further, the heated water supply is returned to the pressure vessel 11 via the water supply pipe 27 by the water supply pump 26.

  In this way, in the BWR system 10, the corrosion eluate contained in the condensed water is removed by the condensate purification system 23 (hollow fiber membrane condensate filtration device and condensate demineralizer) and is constantly purified. However, the metal ions eluted in the feed water passing through the downstream of the condensate purification system 23 (for example, the feed water pipe 27) are very dilute, but are brought into the pressure vessel 11, and the fuel covering of the core 14 is covered. It concentrates on the surface of a tube (not shown) and precipitates as an oxide.

The oxide deposited on the fuel cladding tube is activated by neutron irradiation, then released into the cooling water, and purified by the liquid contact surface of the recirculation pipe 29 forcibly circulated by the recirculation pump 28 and the filter demineralizer 31. The situation where it adheres again to the liquid contact surface of the water purification system pipe 30 occurs.
Further, when an oxide film grows on the liquid contact surface of the recirculation pipe 29 and the reactor water purification system pipe 30, a situation occurs in which the activated oxide is taken in and accumulates in the growing oxide film.
If accumulation due to such redeposition of the activated oxide and growth of the oxide film proceeds, there is a concern that the radiation dose rate on the pipe surface in the recirculation pipe 29 and the reactor water purification system pipe 30 may increase. .

A pressurized water reactor (PWR) system 50 (hereinafter referred to as a PWR system 50) shown in FIG. 2 circulates pressurized water heated by a pressurized water reactor 51 and pressurized by a pressurizer 53 by a primary pump 54. A primary cooling system to be introduced into the steam generator 55 and a secondary cooling system that generates steam via a heat transfer tube (not shown) provided in the steam generator 55 to drive the high-pressure turbine 60 and the low-pressure turbine 62. It consists of and.
Further, the PWR system 50 transforms electric power generated from the generator 63 connected coaxially with the rotating high-pressure turbine 60 and the low-pressure turbine 62 by the main transformer 64 and transmits the electric power through the transmission line 65. Further, seawater is sent to the condenser 66 by the circulating water pump 67, and the steam that has passed through the high-pressure turbine 60 and the low-pressure turbine 62 is cooled to be condensed water.

  The primary cooling system is accommodated in the reactor containment vessel 52 together with the pipes connecting the main components described above. The secondary cooling system further includes a high-pressure feed water heater 56, a feed water pump 57, a deaerator 58, a main steam isolation valve 59, a moisture separator heater 61, a ground condenser 68, a condensate demineralizer 69, and the like. They are connected to each other.

  Also, in the piping of the primary cooling system of the PWR system 50, as in the piping of the BWR system 10, when accumulation due to the reattachment of the activated oxide and the growth of the oxide film proceeds, the radiation dose on the surface of the piping There is a concern that the rate will rise. In addition, there is a concern about deterioration due to corrosion in the piping of the secondary cooling system.

Therefore, in order to improve the corrosion resistance of the piping as described above (hereinafter referred to as “reactor piping”), the atomic ratio of titanium and zirconium is 1: 1 on at least a part of the inner surface of the reactor piping. A coating film made of zirconium titanate is formed.
Thereby, in the part which formed the said coating film of the reactor piping, the elution of a metal ion and the growth of an oxide film can be suppressed, and the effect which makes the radiation dose rate on the piping surface low is acquired.

  The reason for suppressing the elution of metal ions and the growth of oxide film by forming such a coating film is that the wetted surface of the reactor piping is covered with the zirconium titanate film and is in direct contact with the reactor water. This is thought to be due to the lack of

  The coating film made of zirconium titanate described above is stable with no elution in the reactor water of the actual nuclear system, and remarkably improves the corrosion resistance of the reactor piping against the reactor water. Furthermore, such a coating film can be formed with high adhesion strength to a metal substrate that forms the liquid contact surface of the reactor pipe by a so-called chemical solution method.

  The coating film preferably has a thickness of 0.01 μm or more and 10 μm or less. The reason for this is that when the film thickness is less than 0.01 μm, the coating film cannot uniformly cover the liquid contact surface of the reactor piping, and the liquid contact surface is partially exposed and the corrosion resistance decreases rapidly. Because. On the other hand, when the film thickness is thicker than 10 μm, the adhesion strength of the coating film to the wetted surface is lowered, so that the coating film is cracked, the corrosion resistance of the wetted surface is lowered, and the coating film is peeled off. This is because it occurs.

Next, a method for manufacturing a reactor pipe according to the present invention will be described.
In order to form a coating film on the inner surface (wetted surface) of the reactor piping member, first, a titanium-zirconium-based compound solution having an atomic ratio of titanium to zirconium of 1: 1 is applied to the inner surface.
Next, the reactor piping member coated with these solutions is heat-treated to form a coating film made of zirconium titanate.

Here, the solution containing a titanium-zirconium-based compound is a solution containing a complex of these metal elements, a solution containing an alkoxide compound of these metal elements, a solution containing a salt of these metal elements, It includes a sol produced by hydrolysis of a metal element compound.
As a solvent for these solutions, water, alcohols such as butanol and isopropyl alcohol, other organic solvents, and mixtures thereof are used.
As the complex, alkoxide compound, and salt of titanium and zirconium metal elements, any one can be used as long as it is soluble in the aforementioned solvent.
Examples of the metal element compound that forms a sol by hydrolysis include alkoxide compounds and salts. These are not particularly limited as long as they are soluble in the aforementioned solvent.

Examples of methods for applying these solutions to the inner surface of the reactor piping member include dipping and spraying. As such an application method, an optimum method may be adopted according to the size and shape of the reactor piping member on which the coating film is to be formed.
Next, the reactor piping member coated with these solutions is heat-treated. As a heating method, the reactor piping member coated with the solution may be held in an electric furnace and the entire reactor piping member may be heated, or only the coating portion of the reactor piping member is heated by infrared rays or the like. It is also possible to do it. Furthermore, it is not limited to these heating methods, A well-known heating method is employ | adopted.

And it is preferable to perform heat processing temperature at 80 to 600 degreeC.
If the heat treatment temperature is lower than 80 ° C., the thermal decomposition of the zirconium titanate precursor is insufficient and a dense film cannot be obtained, and the formed film is unstable and causes problems such as aging and peeling. To do.
On the other hand, when the heat treatment temperature is higher than 600 ° C., the structure of the metal that is the base material of the reactor piping member changes, and characteristics such as fatigue strength and creep strength are deteriorated. Note that the heat treatment atmosphere is an atmosphere containing oxygen such as in the air.
By this heat treatment, a coating film made of zirconium titanate is formed on the surface of the reactor piping member.

  The above-described method for manufacturing a reactor piping member of the present invention is a so-called chemical solution method, which is a simple process, does not require the use of an expensive apparatus, and has a large cost even though the cost is low. This is an extremely practical method that can be applied to a member or a complex-shaped nuclear reactor piping member. At the same time, it is possible to form a uniform film, and there is an advantage that there is almost no change in the surface roughness of the reactor piping member due to the coating operation, and no processing after the coating operation is required.

A test piece prepared by processing carbon steel SS400 into a strip shape of 40 mm × 20 mm × 1 mm was prepared.
An isopropyl alcohol solution containing 5 mol% of a titanium-zirconium alkoxide having an atomic ratio of titanium to zirconium of 1: 1 was applied to the surface of the test piece by dipping.
After application, the test piece was heat-treated at 400 ° C. for 10 minutes in the atmosphere to form a coating film. This process was repeated three times to adjust the film thickness.

The film thickness of the coating film formed on the surface of the test piece was about 1 μm, and the coating film was made of amorphous zirconium titanate.
The test piece on which the coating film was formed was subjected to a corrosion resistance test in high-temperature high-pressure water simulating an actual machine.

  In this test, the test piece is held at 280 ° C. and 7 MPa for 1000 hours in pure water. Corrosion resistance is evaluated by analyzing the weight change of the test piece before and after the test and analyzing the immersed water.

  As a result, the test piece on which a coating film made of amorphous zirconium titanate having a thickness of about 1 μm was formed showed almost no change in weight before and after the test. In addition, elution of metal ions into water was not observed.

(Comparative Example 1)
As Comparative Example 1, a corrosion resistance test was performed in the same manner as in Example 1 on a test piece made of the carbon steel SS400 base material on which the above-described coating film was not formed. As a result, a remarkable oxide film was observed on the surface of the test piece by visual observation or microscopic observation, and a significant weight increase was recognized. Furthermore, elution of metal ions into water was observed.

As described above, it was confirmed that the reactor piping such as the reactor piping member of the example exhibited high corrosion resistance by forming a coating film made of zirconium titanate on the surface.
Further, in the method of manufacturing a reactor pipe according to the embodiment, since it is based on a chemical solution method, it is inexpensive and can form a high quality coating film regardless of the shape and size.

  Therefore, it can be said that the present invention suppresses the elution of metal components from the surface of the in-furnace equipment, reduces the amount of metal ions deposited on the fuel rod surface, and reduces the amount of radioactive corrosion products generated. .

  Furthermore, it is demonstrated that the growth rate of the oxide film such as piping is reduced, and it can be said that the activation of the activated corrosion product into the oxide film is suppressed.

  As a result, the radiation dose rate on the pipe surface can be lowered, which greatly contributes to the safety of the nuclear system.

  DESCRIPTION OF SYMBOLS 10 ... BWR system (nuclear system), 11 ... Pressure vessel, 12 ... Core shroud, 13 ... Jet pump, 14 ... Core, 15 ... Moisture separator, 16 ... Steam dryer, 17 ... Main steam pipe, 18 ... Turbine , 19 ... Condenser, 23 ... Condensate purification system, 24 ... Condensate pump, 25 ... Feed water heater, 26 ... Feed water pump, 27 ... Feed water piping, 28 ... Recirculation pump, 29 ... Recirculation piping, 30 ... Reactor water purification system piping, 31 ... filtration desalter, 50 ... PWR system (nuclear power system), 51 ... pressurized water reactor, 52 ... reactor containment vessel, 53 ... pressurizer, 54 ... primary pump, 55 ... steam Generator: 56 ... High pressure feed heater, 57 ... Feed water pump, 58 ... Deaerator, 59 ... Main steam isolation valve, 60 ... High pressure turbine, 61 ... Moisture separation heater, 62 ... Low pressure turbine, 63 ... Generator 64 ... Main transformer, 65 ... Wire, 66 ... condenser 67 ... circulating water pump, 68 ... ground capacitor, 69 ... condensate demineralizer.

Claims (5)

Piping constituting a nuclear reactor, wherein a coating film made of zirconium titanate having an atomic ratio of titanium to zirconium of 1: 1 is formed on at least a part of the inner surface. . The reactor pipe according to claim 1, wherein the coating film has a thickness of 0.01 μm or more and 10 μm or less. Applying a titanium-zirconium-based compound solution having an atomic ratio of titanium and zirconium of 1: 1 to at least a part of the inner surface of a pipe constituting the nuclear reactor;
And a step of forming a coating film made of zirconium titanate by heat-treating the pipe to which the solution is applied. The said heat processing is performed at the temperature of 80 to 600 degreeC, The manufacturing method of the reactor piping of Claim 3 characterized by the above-mentioned. The method for manufacturing a reactor pipe according to claim 3 or 4, wherein the coating film has a thickness of 0.01 µm or more and 10 µm or less.

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