JPS62140099A - Corrosion protective film formation method of nuclear power plant and device thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing a corrosion-resistant film in a nuclear power plant, such as boiling water nuclear power plant, which produces an oxide film on reactor piping, etc. Driving method) and equipment related to 9.

(Technical day before the invention) In general, the inside of the nuclear reactor in nuclear power generation plans 1 to +3 is as follows:
Produces radionuclides by activation with neutrons. These radionuclides are incorporated into the oxide film during the formation of the oxide film on the primary cooling system piping and the piping of the equipment connected to it, and as a result, the surrounding area of the primary cooling rJl system and the equipment connected to it. As a result of this, it is predicted that workers working in nuclear power plants will be exposed to radiation during periodic inspections.

In order to improve the safety and reliability of nuclear power generation facilities, it is extremely important to reduce the exposure of the above-mentioned workers. Therefore, as a means to prevent workers from being exposed to radiation, we reduce the amount of impurities that are brought into the reactor and become radioactive.
It is desired to reduce the linear m rate of radionuclides taken into the oxide film of the primary cooling system piping and the equipment piping.

On the other hand, the stainless steel pipes used in the primary cooling system and equipment connected thereto initially develop a chromium-rich film on their surfaces, and then develop a chromium-rich coating on their surfaces.

Corrosion progresses due to the diffusion of ions toward the outside of the skin and the diffusion of oxygen toward the inside of the film. Furthermore, it is said that the chromium film layer increases corrosion resistance by producing an oxide of Fe5o4 called magnetite. into spinel oxide.

2 To 2 I Fe O + COCo - Fe2O4 + "e When a nuclear reactor starts operating, an oxide film is formed on the inner surface of the stainless steel tube used in the reactor's primary cooling system, which matches the operating temperature conditions of the reactor. At the same time, the water in the nuclear reactor is irradiated with neutrons, causing, for example, Co-58, Co
Radioactive nuclides such as -60 are produced and increase.

That is, magnetite (Fe304
) In the reactor water (7) Ill' as the film is formed.
JJ Sexual nuclide-c Al CO58, C0608 is incorporated into the film as Kasbinel oxide, so when the primary cooling system is made of the stainless steel piping, the radiation ω rate of this primary cooling system increases, and the reactor plan During the periodic inspection of 1-, it is predicted that those engaged in overhauling and inspecting the primary cooling Ul system and equipment connected to it will be exposed to radiation.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and improves safety and reliability by preventing the generation of radioactive nuclei in the reactor primary cooling system and related equipment, and reducing the linear m rate. It is an object of the present invention to provide a method and apparatus for producing a corrosion-resistant coating for a nuclear reactor plant, which can improve the corrosion resistance of a nuclear reactor plant.

[Summary of the invention]

The present invention makes the pressure fluid from the dissolved oxygen supply source have a constant oxygen concentration before heating the nuclear reactor core, and pumps it through the control rod drive water-cooled Jul system to the reactor and primary cooling system. This method generates an oxide film on the primary cooling system and related equipment by driving a recirculation pump and heating the reactor water to a high temperature using Joule heat generated by the recirculation pump.

Furthermore, the present invention installs a recirculation system equipped with a recirculation pump in a nuclear reactor, connects a primary cooling fJI system to this, and installs a dissolved oxygen 12 sensor in this primary cooling system. and a dissolved oxygen supply source are connected by a control rod drive water cooling system, and the control rod drive water cooling NI system is connected to a flow rate regulating valve and C, R that are controlled by detecting the pressure of the reactor.

A D pump is installed, and the recirculation pump and C, R, and D pumps are driven before the nuclear heating of the reactor, and the reactor water is heated with Joule heat from this recirculation pump, and the C, R, and D pumps pressurize it. The structure is such that an oxide film is formed at a constant oxygen concentration.

[Embodiments of the invention]

Hereinafter, the present invention will be described with reference to an illustrated embodiment.

In FIG. 1, reference numeral 1 in J3 is a boiling water reactor designated by J5L in nuclear power generation plans 1 to 1, and this reactor 1 is equipped with a recirculation system 3 equipped with a recirculation pump 2. A primary cooling system 4 of the nuclear reactor 1 is connected to this recirculation system 3. Additionally, a dissolved oxygen sensor 5 is attached to the primary cooling system 4, which is composed of a reactor water dissolved oxygen meter 5a and a reactor dissolved oxygen control system 5b. - electrically connected to the demineralized water supply valve 7 installed in the water supply pipe 6; Furthermore, the above nuclear reactor 1
A control rod drive mechanism (not shown) installed at the bottom of the control rod drive mechanism (not shown) and a dissolved oxygen supply source 8 consisting of a condensate storage tank are connected to a control rod drive water cooling system 9 and a V! The dissolved oxygen supply source 8 stores water sufficiently containing dissolved oxygen.

Furthermore, the control rod drive water cooling system 9 is provided with a flow rate adjustment valve 10, a dissolved oxygen meter 5a, and a C, R, D pump (pump for control rod drive vJ device) 11. A pressure sensor 12 attached to the furnace 1 is connected to the flow rate regulating valve 1.
0 to detect the pressure inside the furnace. A desalinated water supply pipe 6 is connected to the control rod driving water cooling system 9, and when the desalted water supply valve 7 is opened, the desalted water in the desalted water supply pipe 6 is supplied to the control rod driving water cooling system 9. It joins the water containing dissolved oxygen in the water cooling system 9 and is supplied to the nuclear reactor.

On the other hand, in the water cooling system 4, a salt tower 13 for use in the reactor coolant purification system is installed, and this filtration and desalination tower 13 is installed.
An oxygen gas supply source 14 is connected to the water cooling system 4 near the water cooling system 4 via an on-off valve 15 .

The nuclear reactor 1 and the steam turbine 16 are connected by two main steam pipes, and a condenser 17 is connected to the steam turbine 16. The well 17a and the primary cooling system 4 are the waste treatment system 1.
8 is connected by a reactor water dump pipe 19.

Furthermore, the lower part of the condenser hot well 17a and the reactor 1 are connected by a feed water recirculation system 20 and a water supply line 28 having an on-off valve 28a, and one end of this feed water recirculation system 20 is It is connected to the upper part of the condenser 17. In addition, the water supply recirculation system 20 includes a condensate pump 20a, a condensate filter 21, and a condenser JS2j! 522
are arranged in this order, and a recovery line 23 for recovering excess condensate is connected to the feed water recirculation system 20 at the discharge side of the condensate demineralization tower 22. Further, the other end of this recovery line 23 is connected to the condenser hot well 17a,
In this recovery line 23, the dissolved oxygen supply source 8 and the condensate transfer pump 24 are installed.

Note that an exhaust gas system 26 equipped with a vacuum ejector 25 is connected to the condenser 17, and this condenser 17
A predetermined degree of vacuum is maintained by a vacuum ejector 25. Further, the on-off valve 28a of the water supply line 28 is open during normal operation of the nuclear reactor 1.

Hereinafter, the effects of the present invention will be explained.

Now, before the reactor is started for the first time in the evening, a bleed film operation is performed to generate a corrosion-resistant coating.

The reactor 1 is filled with water in advance. Next, the recirculation pump 2 and the C, R, D pumps 11 are driven, and while the pressure in the reactor is raised to a high pressure (11), the rotation speed of the recirculation pump 2 is increased, and the rotation speed of the recirculation pump 2 is increased. Joule heat is used to raise the temperature of the reactor water. When the reactor pressure due to thermal expansion of the reactor water reaches its upper limit due to the upper limit of the reactor water temperature, the flow rate adjustment valve 10 is throttled by a signal from the pressure sensor 12 to maintain the pressure in the reactor 1 constant. ), the reactor water temperature increases.

In order to maintain the reactor water temperature at about 280°C during normal reactor operation, in reactor 1, the saturation temperature must be 280°C.
As mentioned above, it is necessary to maintain a high pressure state (P), but in such a high temperature and high pressure state, stress corrosion due to high dissolved oxygen on the stainless steel pipes that make up the primary cooling system 4 of the reactor 1 can occur. From the viewpoint of cracking, it is essential to control the dissolved oxygen in the reactor water, and in addition, it is necessary to maintain the dissolved oxygen concentration in the reactor water as high as possible in order to form a dense, corrosion-resistant oxide film. desired.

On the other hand, during normal reactor operation in J5, the dissolved oxygen in the reactor water is approximately 200 to 300 PP due to the radiolysis effect of the cooling water.
b, and the stress IO due to stainless steel material! 4 The maintenance standard for preventing corrosion cracking is 400PPb or less.

Therefore, considering the above points, the reactor dissolved oxygen was reduced to 400
In order to maintain PI"11, the concentration of dissolved oxygen in the control rod drive system cold fJl water supplied to reactor 1 must be controlled i2++
This controls dissolved oxygen in the reactor water.

Immediately, use the vacuum ejector 25 to remove the condenser hot well 1.
7a is maintained in a vacuum state to generate degassed water, the condensate pump 20a is driven, the condensate is purified by the condensate filter 21 and the condensate demineralization tower 12, and then passed through the feedwater recirculation system 20. Continuously recirculate and purify.

Next, using the recovery line 23 connected to the discharge side of the condensate IB2 salt bath 22, a part of the purified deaerated water is used as a water source for the C, R, D pumps 11, and the C, R, D pumps 11
The demineralized water with saturated dissolved oxygen is fed into the demineralized water supply pipe 9.
The degassed water and demineralized water with saturated dissolved oxygen are mixed and supplied to the reactor 1, and at the same time, the dissolved oxygen concentration is monitored by the reactor water dissolved oxygen meter 5a. On the other hand, the dissolved oxygen concentration in the reactor water is continuously monitored by the dissolved oxygen sensor 5, and the demineralized water supply valve 7 is controlled based on the detection signal from the dissolved oxygen sensor 5 to maintain the reactor water oxygen at 400 PPb. This controls the dissolved oxygen in the reactor water to 4 Q Q PPb.

In addition, in this step, dissolved oxygen in the reactor water is consumed to form a dense anti-corrosion oxide film on the primary cooling system 4 and the equipment connected to it, increasing the reactor dissolved oxygen concentration to 4Q.
Q When it is no longer possible to maintain the level of PPb, open the on-off valve 15 to supply oxygen from the oxygen gas supply source 14 to the reactor 1 through the primary cooling system 4, and remove the dissolved acid in the reactor water from the reactor water. Q Control to PPb.

In this way, the present invention drives the C, R, and D pumps 11 to pressurize the nuclear reactor 1, and at the same time heats the reactor 1 using Joule heat of the recirculation pump 2 to achieve high temperature and high pressure. At the same time, by controlling the dissolved oxygen concentration in the control rod drive water cooling system 9, the reactor dissolved oxygen is maintained constant, and the primary cooling system 4 and these are Creates a dense, corrosion-resistant oxide film on connected equipment.

Therefore, the present invention can reduce radionuclides by the oxide film formed on the primary cooling system and the inner surface of these devices after nuclear heating, and also suppress the upper limit of the linear ω factor of piping and devices, It is possible to prevent workers from being exposed to radiation.

Furthermore, the pre-flaming operation method according to the present invention is not limited to the operation before nuclear heating; for example, the corrosion-resistant oxide skin-inducing operation may be performed during the early stage of nuclear heating when the radioactivity concentration is low. Of course.

On the other hand, in the present invention, an oxide film is formed on the primary cooling system 4 and the m-units connected thereto, as shown in the graph of FIG. 2. In other words, when the untreated adhesion radioactivity curve that does not generate an oxide film is subjected to the brefilming treatment according to the present invention to produce a corrosion-protective oxide film, the adhesion radioactivity amount curve (■) The radioactivity remains constant without increasing even after approximately 2000 hours.

〔Effect of the invention〕

As described above, according to the present invention, the pressure inside the reactor 1 is maintained at a high pressure by driving the recirculation pump 2 and the C, R, I) pump 11 before nuclear heating in the reactor, and the recirculation pump The reactor water is heated with 2 Joule heat and an oxide film is generated at a certain dissolved oxygen concentration, which not only reduces radioactive nuclides, but also reduces the number of lines in the reactor piping and equipment. It is possible to improve safety by suppressing the upper bound of the radiation rate and reducing radiation exposure for workers.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of the anti-corrosion film generating apparatus of nuclear power generation plans 1 to 1 of the present invention, and FIG. 2 is a graph showing the relationship between the amount of attached radioactivity and the immersion time. DESCRIPTION OF SYMBOLS 1... Nuclear reactor, 2... Recirculation pump, 4... Primary cooling system, 5... Dissolved oxygen sensor, 6... Desalinated water supply pipe, 7... Desalinated water supply valve, 8 ...dissolved oxygen source,
9... Control drive water cooling 7J] system, 10... Flow rate adjustment valve, 11... C, R, D... Pump, 12... Pressure cylinder, 14... Oxygen supply source, 23...Collection line.

Claims (1)

[Claims] 1. Before nuclear heating in a nuclear reactor, pressurized fluid from a dissolved oxygen supply source is made to have a constant oxygen concentration, and this is pumped through a control rod drive water cooling system to the reactor and primary cooling system. By driving the reactor's recirculation pump and heating the reactor water to a high temperature using Joule heat generated by the recirculation pump, an oxide film was generated on the primary cooling system and equipment connected to it. A method for producing a corrosion-resistant coating for a nuclear power plant, characterized by the following. 2. A recirculation system equipped with a recirculation pump is provided in the reactor, a primary cooling system is connected to this, a dissolved oxygen sensor is attached to this primary cooling system, and a control rod connects the reactor and the dissolved oxygen supply source. a flow rate regulating valve connected to the drive water cooling system and controlled by detecting the pressure of the reactor to the control rod drive water cooling system;
R and D pumps are installed, and the recirculation pump and C, R, D pump are driven before nuclear heating of the reactor, and the reactor water is heated with Joule heat from the recirculation pump, and the C, R, and D pumps are used to heat the reactor water. A corrosion-resistant film generation device for a nuclear power plant, characterized in that it generates an oxide film under pressure at a constant oxygen concentration.