JPH0348198A - Decontamination method and device for liquid metal cooled nuclear reactor equipment and nuclear reactor facility equipped with the device - Google Patents

Abstract

PURPOSE:To remove contaminants on a surface of equipment uniformly and to leave no impurity in a coolant by raising a concentration of elements which accelarate a dissolving velocity of radioactive substances contained in a circulating liquid metal, when the equipment is decontaminated. CONSTITUTION:A lid of a dissolution tank 1 is opened and then an equipment 3 which is an object to be decontaminated, is soaked into a liquid Na 2 in the dissolution tank 1, and after that, the lid is put on the tank and an inert gas is filled to an upper space in the dissolution tank 1. Subsequently, each temperature of a heater 4 and a cooler 7 is set, respectively. Then, a pump 9 is actuated and therewith the liquid Na 2 which contains a high concentration oxygen is made to circulate through the dissolution tank 1, a piping, a concentration controller 6, another piping, a trap 21, a pump 9 and the dissolution tank 1 again, in series. With this procedure, a surface of the equipment dissolves out uniformly and radioactive corrosion products which thermally diffuse on the surface, dissolve into the liquid Na.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a decontamination method and a decontamination device for liquid metal cooled nuclear reactor equipment, and in particular, to a decontamination method and a decontamination device for liquid metal cooled nuclear reactor equipment, and in particular, for decontamination of liquid metal wetted surfaces of equipment contaminated with radioactive substances. The present invention relates to a decontamination method and device suitable for efficiently removing.

[Prior Art] In light water reactors, which are a type of nuclear reactor, it is known that radioactive corrosion products in the primary coolant adhere as oxides to surfaces of equipment that come into contact with the primary coolant. Therefore, in order to reduce the dose rate of primary equipment.

All that is required is to remove the radioactive corrosion products adhering to the equipment surface, that is, the oxides on the equipment surface. For this reason, conventional decontamination technology for light water reactors dissolves only the oxides in one piece of equipment, and uses a weakly acidic decontamination agent that hardly dissolves the stainless steel base material, allowing surface oxidation to occur without damaging the equipment itself. Only things are dissolved and removed.

An alternative method is to use chemical decontamination agents to remove radioactive corrosion products from equipment surfaces.

In addition, as related to conventional technology, there is ``Actual and future technical issues of decontamination technology in nuclear facilities'' published by Sangyo Gijutsu Publishing.

[Problem M to be Solved by the Invention] In nuclear reactor systems that use liquid metal as a coolant, stainless steel, which has good coexistence with liquid metal, is used as the base material of the primary cooling system equipment. Therefore.

As in the prior art described above, as long as a weakly acidic decontaminating agent is used, the internal body of a single device is rarely damaged by the decontaminating agent.

However, unlike light water reactors, liquid metal cooled reactors are -
Due to the high temperature of the water coolant, its radioactive corrosion products do not adhere to the equipment surface but are thermally diffused into the equipment base material. It is said that the effective penetration distance of radioactive corrosion products thermally diffused into the base material of the equipment, which is the cause of the accumulation of corrosion, is several μm from the surface. That is, when decontaminating the primary cooling system equipment of a liquid metal cooled nuclear reactor device, it is necessary to uniformly melt and scrape off the surface of the equipment base material itself. For this reason, as long as weakly acidic decontamination agents used in light water reactors are used,
It is difficult to decontaminate radioactive corrosion products that have entered the equipment base material.

If a strong acid decontamination agent is used instead of a weak acid decontamination agent, it becomes possible to dissolve the surface of the equipment base material. However, because the reaction occurs rapidly, it is difficult to uniformly dissolve the surface of the device. Moreover.

If there is a stress residual area in a welded part of a device, there is a problem in that the area will be selectively melted.

When chemical decontamination is used to decontaminate the primary cooling system equipment of liquid metal cooled nuclear reactors, it is possible to decontaminate the primary cooling system equipment, but since the main component of the decontamination agent is water, the equipment after decontamination must be When loaded into a cooling system, another problem arises: residual moisture on the equipment decomposes into oxygen and hydrogen in the liquid metal, which act as impurities and accelerate corrosion of the equipment. Furthermore, in liquid metal cooled nuclear reactor equipment, a cold trap is installed to remove impurities from the primary coolant, but bringing residual moisture into the primary cooling system increases the load on this cold trap. , there is also the problem of shortening its lifespan.

The object of the present invention is to provide a decontamination method and decontamination device that can uniformly dissolve the surface of the primary cooling system equipment of a liquid metal cooled nuclear reactor device and that does not leave impurities such as residual moisture in the coolant. Another object of the present invention is to provide a nuclear reactor system equipped with this decontamination device.

[Means for solving the problem] The above purpose is to prevent the elution of radioactive substances such as oxygen contained in the circulating liquid metal during decontamination when decontaminating nuclear reactor equipment that uses liquid metal as a coolant. This is achieved by increasing the rate-accelerating element concentration.

The above object can also be achieved by increasing the temperature of the liquid metal during decontamination.

The above objective can also be achieved by increasing the circulation rate of liquid metal during decontamination.

[Operation] During normal operation of the nuclear reactor system, the concentration of elements that accelerate the elution rate of radioactive substances, such as oxygen, contained in the liquid metal is lowered. This is because when such elements are contained in the liquid metal, they scrape the surface of the base material of primary cooling system equipment such as piping, reducing its wall thickness. In the present invention, the phenomenon that has been a problem in the past is actively utilized and the concentration of the above elements is increased during decontamination to accelerate the dissolution rate on the surface of the equipment and decontaminate it.

The surface of the device is scraped uniformly, and since liquid metal is used during actual operation, it is possible to avoid residual impurities that cause problems during actual operation, and to avoid selective dissolution of stress-remaining parts of the device.

When controlling the concentration of the above-mentioned elements, a dedicated concentration control device may be provided. Furthermore, the concentration of the element can be increased by increasing the temperature of the liquid metal being circulated.

In addition to the above, it is known that, as an in-shell phenomenon, when the flow rate of circulating liquid metal is increased, the thickness of equipment that comes into contact with the liquid metal progresses. Therefore, when performing decontamination using such a phenomenon.

By increasing the circulation speed during decontamination, it is possible to uniformly dissolve the surface of a single device. Combining the phenomena described above,
During decontamination, more efficient decontamination can be achieved by circulating liquid metal containing a high concentration of the above elements at high speed.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of a decontamination apparatus according to an embodiment of the present invention. The decontamination device according to this embodiment includes a dissolution tank 1, a pump 9 for circulating the liquid metal 2 placed in the dissolution tank 1, and a concentration control device installed in the middle of the circulation path 14 and 15 for the liquid metal 2. It consists of 6.

The equipment 3 to be decontaminated is immersed in the liquid metal in the dissolution tank 1 so that at least the entire part to be decontaminated is buried. The liquid metal 2 used is preferably the same liquid metal as the liquid metal that the equipment 3 to be decontaminated actually comes into contact with during nuclear reactor operation, and in this embodiment, liquid sodium is used. The concentration control device 6 controls the concentration of a radioactive substance elution rate accelerating element contained in the liquid sodium 2, which is oxygen in this embodiment.

In addition to the above-described configuration, the decontamination apparatus of this embodiment is provided with a heater 4 on the outer periphery of the dissolution tank 1, the amount of which is controlled by a power source 5, and is controlled so that the temperature of the liquid sodium 2 is constant. be done. Further, a cooler 7 is provided on the outer periphery of the concentration control device 6, and the oxygen concentration in the liquid sodium is controlled to a predetermined concentration. Note that a heat insulating material (not shown) is attached to each component and piping of the decontamination apparatus to prevent the temperature of the liquid sodium 2 from decreasing. Further, an inert gas such as argon is sealed in the space above the liquid level in the dissolution tank 1 as a cover gas.

As mentioned above, the concentration control device 6 controls the concentration of the element that accelerates the elution rate of radioactive substances contained in the liquid sodium 2. In this embodiment, the temperature of the liquid sodium 2 in the concentration control device 6 is controlled. By controlling the element concentration, in this example, the oxygen concentration is controlled. FIG. 2 is a detailed configuration diagram of this concentration control bag 'I16.

In FIG. 6, the concentration control device 6 according to this embodiment is
A container 6a is provided for retaining liquid sodium 2 flowing from the dissolution tank 1 via a pipe 14, controlling the oxygen concentration, and returning it to the dissolution tank 1 via a pipe 15. Oxygen is supplied at a constant pressure from the buffer tank 16 through the oxygen supply pipe 8 to the space (cover gas) 22 above the liquid level of the liquid sodium 2 in the container 6a. 2 to saturation solubility. Inlet piping 1
4 opens into the cover gas section 22, and the liquid sodium 2 flowing from the pipe 14 passes through the oxygen in the cover gas section 22 and comes into sufficient contact with the oxygen, and then becomes the liquid sodium 2.
It looks like it will fall to the liquid level. The oxygen pressure in the cover gas section 22 is measured by a pressure gauge 17, and the pressure controller 18
is the supply control valve 2o and the release control valve 1 based on this measured value.
9 to keep the oxygen pressure in the buffer tank 16 constant. Thereby, the oxygen pressure in the cover gas section 22 is controlled to be constant.

In FIG. 2, the cooler 7 shown in FIG. and a temperature controller 13 that controls the air flow rate of the blower 11 to maintain the temperature of the liquid sodium 2 at a predetermined value based on the measurement a.

The temperature of the liquid sodium 2 in the container 6a is controlled to be the lowest temperature at which oxygen does not precipitate within the decontamination device.

When performing decontamination using the decontamination apparatus configured as described above, first, open the lid of the dissolution tank 1 and immerse the equipment 3 to be decontaminated in the liquid sodium 2 in the dissolution tank 1, then close the lid and leave the dissolution tank. The upper space in 1 is filled with inert gas. Then, the temperatures of the heater 4 and cooler 7 are set. Then, the pump 9 is started, and the liquid sodium 2 containing a high concentration of oxygen is pumped into the dissolving tank 1° piping 14. Concentration control device6. Piping 15. Circulate with pump 9° dissolution tank 1. By remaining in this state for a required period of time, the surface of the equipment 3 to be decontaminated is uniformly dissolved, and the radioactive corrosion products thermally diffused on the surface are eluted into the liquid sodium. As a result, the dose rate of the equipment 3 to be decontaminated is significantly reduced.

Next, the principle by which decontamination progresses according to the above-described embodiment will be explained using FIGS. 3 and 4.

Figure 3 shows the empirical formula (RoL, Eichelberger) determined by R.L. Eichelberger.
；“The 5olility of Oxyga
n 1nLiquid 5odiu+++: AReco
“mended Expression”, AI-AB
FIG. In addition, Figure 4 is a graph showing the dependence of the dissolution rate of stainless steel in liquid sodium on 1 degree oxygen using the sodium temperature as a parameter (Maruyama et al., ``Evaluation of corrosion rate of austenitic stainless steel in high-temperature sodium''. Formula J, 26, 327 (1984,) B Journal of the Atomic Energy Society).

Normally, in liquid sodium cooled fast reactors, in order to prevent corrosion of equipment during reactor operation (melting of metal on surfaces of equipment in contact with liquid sodium), oxygen in liquid sodium 2, an impurity, The oxygen concentration is captured and removed, and the oxygen concentration is limited to a few ppm or less.In this example, this principle is used in reverse, and in order to accelerate the corrosion mentioned above during decontamination, it is circulated in the decontamination equipment. Actively increase the oxygen concentration in liquid sodium 2. According to the graph shown in Figure 3,
The temperature of liquid sodium 2 in oxygen concentration control device 6 is 3
It can be seen that it is preferable to control the temperature to 00°C or higher.

An example of operating conditions in the decontamination equipment is shown in Figures 3 and 4, where the sodium temperature in the concentration control device 6 is set at approximately 480°C.
Make it. This results in an oxygen concentration of approximately 11,000 pp. Therefore, the temperature of liquid sodium 2 in dissolution tank 1 was set to about 5
At 00℃, the dissolution rate of stainless steel is approximately 4μm/
Becomes the moon. Normally, the depth at which radioactive corrosion products are thermally diffused into the metal base material is about several micrometers, so under these conditions, decontamination will be completed in about two months. Also, increase the oxygen concentration to about 1100
When the sodium temperature in the dissolving tank 1 is set to 0 pp and about 550° C., the dissolution rate of stainless steel is about 10 μm/month, and in this case, decontamination is completed in about one month or less. From FIGS. 3 and 4, the dissolution rate can be determined by controlling the temperature of liquid sodium, so the time required to complete decontamination can be determined.

In addition, in the above-mentioned example, the oxygen concentration in the liquid sodium was controlled by controlling the temperature of the liquid sodium, but the present invention is not limited to this, and the oxygen concentration may be controlled by other methods. Needless to say, anything is fine. Furthermore, although oxygen was used in the above embodiment as the element that accelerates the dissolution rate of radioactive substances, the present invention is not limited to this, and any other element may be used as long as it accelerates the dissolution of the metal surface. can do. Furthermore, in this embodiment, only the oxygen concentration was changed, but for example, instead of the concentration control device 6, the pump 9 can be deactivated to control the flow rate of the circulating liquid sodium. Can be dyed. This is because there is a general phenomenon that the higher the flow rate of liquid sodium, the faster the rate at which the metal surface is dissolved by the liquid sodium. Therefore, by increasing the circulation speed of liquid sodium and increasing the amount of oxygen contained, the speed of decontamination can be further improved.

FIG. 5 is a configuration diagram of a decontamination apparatus according to a second embodiment of the present invention. The decontamination device according to this embodiment is basically the same as the decontamination device explained in FIG.
The only difference is that For example, in the decontamination equipment shown in FIG. There is also the possibility that the concentration in liquid sodium increases as dissolution progresses, reducing the dissolution rate. Therefore, the trap 21 is provided in the liquid sodium circulation path for the purpose of collecting the radioactive corrosion products dissolved in the liquid sodium and suppressing re-deposition and a decrease in the dissolution rate.

Trap 21 contains radioactive cobalt-60 and manganese-5.
It is filled with a mesh or foil film made of nickel or an alloy mainly composed of nickel, which has a high ability to trap radioactive corrosion products such as No. 4. It is preferable that the area of the mesh or foil film in contact with the liquid sodium is sufficiently larger than the total area of the decontamination target equipment and the decontamination equipment in contact with the liquid sodium. As a result, the rate at which radioactive corrosion products once dissolved in liquid sodium re-adhere to decontamination target equipment and decontamination equipment is extremely reduced, reducing the time required for decontamination, and furthermore, Decrease in wall thickness can be reduced.

Each of the above-mentioned embodiments is an example in which the decontamination equipment is provided separately from the reactor equipment, and when using this decontamination equipment, the reactor equipment is disassembled, the equipment to be decontaminated is taken out, and the decontamination equipment is removed from the melting tank. It is necessary to put it in l. However, it may be more convenient if the equipment can be decontaminated without disassembling the reactor equipment.

Therefore, in the nuclear reactor system shown in FIG. 6, a decontamination device is incorporated into the primary cooling system of the nuclear reactor system.

A circulation pump 25 and an intermediate heat exchanger 26 are connected to the reactor 23 of the nuclear reactor system shown in FIG. 6 to constitute a primary cooling system, and the reactor 23→circulation pump 25→intermediate heat exchanger 26
→The reactor 23 and liquid sodium are circulated by the circulation pump 25. A secondary cooling system inlet pipe 27 and an outlet pipe 28 are connected to the intermediate heat exchanger 26, and the medium flowing through the secondary cooling system and the liquid sodium flowing through the primary cooling system are heated in this intermediate heat exchanger 26. The exchange is scheduled to take place.

The nuclear reactor device in this embodiment has the above-mentioned circulation pump 25.
A decontamination device for decontaminating the intermediate heat exchanger 26 is provided.

This decontamination device includes an oxygen concentration control device 6, a trap 21 and a cold trap 36 provided before and after the oxygen concentration control device 6, and is connected in parallel with the circulation pump 25 between the inlet pipe and the outlet pipe of the circulation pump 25. .

They are connected via valves 29.33 and 30, 31.34, respectively. In addition, this decontamination equipment is equipped with a pump 9,
The pump 9 has one end connected to the outlet side of the intermediate heat exchanger 26 and the water cooling system piping via valves 32 and 35, and the other end connected to the trap 21.

In the above-described configuration, when decontaminating the circulation pump 25, the valve 29 is closed and the valve 33 is opened.

Valve 31 is closed and valves 30, 34 are opened. As a result, the circulation pump 25. Cold trap 36° concentration control device 6. A liquid sodium circulation path consisting of a closed loop of traps 21 is configured. Then, the temperature of the cold trap 36 is raised (if the temperature of the cold trap 36 is low, oxygen will precipitate in the cold trap 36).

), the concentration control device 6 increases the oxygen concentration in the liquid sodium in the same manner as in the embodiment described above, and the circulation pump 25 circulates the liquid sodium into the closed loop.

As a result, the liquid sodium contact surface of the circulation pump 25 is dissolved, and the eluted radioactive corrosion products are collected in the trap 21. After the decontamination is completed in this way, the function of the concentration control device 6 is stopped, and the cooler 37 of the cold trap 36 is activated to cool the cold trap 36. As a result, oxygen as an impurity in the liquid sodium circulating in the closed loop is collected in the cold trap 36, and liquid sodium with a high oxygen concentration is removed from the circulation pump 25. After that, even if valves 33 and 34 are closed and valves 29 and 30 and 31 are opened to disconnect the decontamination equipment from the primary cooling system and operate the reactor equipment, the oxygen concentration in the liquid sodium will not be reduced. Therefore, there is no problem with driving.

When decontaminating the intermediate heat exchanger 26, the valves 33, 30.
32 is closed, and valves 34, 31, and 35 are opened. As a result, intermediate heat exchanger 26 → pump 9 → trap 21 → concentration control device M6 → cold trap 36 → intermediate heat exchanger 2
6 closed loops are constructed. When the concentration control device 6 increases the oxygen concentration in the liquid sodium and the pump 9 circulates the liquid sodium in the closed loop (at this time, the temperature of the cold trap 36 is raised in the same manner as described above), intermediate heat exchange occurs. The liquid sodium wetted surface of vessel 26 is dissolved and radioactive corrosion products are captured in trap 21. After decontamination, oxygen in the liquid sodium is removed by the cold trap 36 in the same manner as described above, and then the decontamination device is separated from the next cooling system.

In the example described above, since decontamination is performed using liquid sodium flowing into the primary cooling system, it is necessary to remove oxygen in the liquid sodium using the cold trap 36 after decontamination.

However, it goes without saying that instead of providing the cold trap 36 in the decontamination device, a cold trap originally provided in the primary cooling system, which is not shown in FIG. 6, may be used. Therefore, a cold trap is not necessarily required in the decontamination equipment. Further, the trap 21 is not necessarily required. Further, as with the decontamination apparatus described above, it is possible to use a configuration in which decontamination is performed by increasing the circulation speed of liquid sodium, or in combination with oxygen concentration control, instead of controlling the oxygen concentration.

[Effects of the Invention] According to the present invention, since the dissolution rate is slower than that of chemical cleaning, the metal base material of equipment to be decontaminated can be uniformly dissolved, and the equipment base material can be dissolved more than necessary. Stainless steel does not need to be stored away, and since it is decontaminated with the same liquid metal that equipment to be decontaminated normally comes into contact with without using acid or water, stress residual areas such as welds will selectively corrode. There is no problem of underwater corrosion of steel. Furthermore, since a decontamination agent whose main medium is water is not used, no moisture remains after decontamination, and there is no need to worry about moisture being brought into the primary cooling system.

Therefore, there is no problem that the load on the cold trap that removes the cold trap increases.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a decontamination device according to a first embodiment of the present invention,
Figure 2 is a detailed configuration diagram of the concentration control device shown in Figure 1;
The figure is a graph showing the temperature dependence of the saturated oxygen concentration dissolved in liquid sodium, Figure 4 is a graph showing the oxygen concentration dependence of the dissolution rate of stainless steel using liquid sodium temperature as a parameter, and Figure 5 is a graph showing the present invention. FIG. 6 is a block diagram of a primary cooling system of a nuclear reactor device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Dissolution tank, 2... Liquid metal, 3... Decontamination target equipment, 6... Concentration control device, 8... Radioactive substance dissolution rate accelerating element supply pipe, 9... Pump, 21... Trap, 23... Nuclear reactor, 25... Circulation pump, 26
...Intermediate heat exchanger, 36...Cold trap.

Claims (1)

[Claims] 1. In a decontamination method for removing radioactive substances accumulated on liquid metal contact surfaces of liquid metal cooled nuclear reactor equipment, the concentration of elements that accelerate the elution rate of radioactive substances contained in circulating liquid metal. 1. A method for decontaminating liquid metal cooled nuclear reactor equipment, the method comprising: increasing the temperature during decontamination, and removing contaminants on the surface of contaminated reactor equipment using the element that accelerates the elution rate of radioactive substances. 2. In a decontamination method for removing radioactive substances accumulated on liquid metal contact surfaces of liquid metal cooled nuclear reactor equipment, the temperature of the circulating liquid metal is increased during decontamination, and the liquid metal with this increased temperature is circulated. A decontamination method for liquid metal cooled nuclear reactor equipment, which is characterized by removing contaminants on the surface of contaminated nuclear reactor equipment. 3. In a decontamination method for removing radioactive materials accumulated on liquid metal contact surfaces of liquid metal cooled nuclear reactor equipment, the circulation speed of the circulating liquid metal is increased during decontamination, and the accelerated liquid metal is circulated. A decontamination method for liquid metal cooled nuclear reactor equipment, which is characterized by removing contaminants on the surface of contaminated nuclear reactor equipment. 4. In a decontamination device that removes radioactive substances accumulated on liquid metal contact surfaces of liquid metal cooled nuclear reactor equipment, there is a dissolution tank that houses the equipment to be decontaminated, and a dissolution tank that houses the equipment to be decontaminated. A liquid metal placed in a tank, a pump that circulates the liquid metal in the dissolution tank, and a pump that is installed in the middle of the circulation path of the liquid metal to remove the concentration of an element that accelerates the elution rate of radioactive substances contained in the liquid metal. 1. A decontamination device for liquid metal cooled nuclear reactor equipment, comprising: an accelerated element concentration control device that increases the concentration during contamination. 5. In a decontamination device that removes radioactive substances accumulated on liquid metal contact surfaces of liquid metal cooled nuclear reactor equipment, there is a dissolution tank that houses the equipment to be decontaminated, and a dissolution tank that houses the equipment to be decontaminated. A liquid metal cooling type atom comprising: a liquid metal placed in a tank; a pump that circulates the liquid metal in the dissolution tank; and a temperature control device that increases the temperature of the liquid metal during decontamination. Decontamination equipment for furnace equipment. 6. In a decontamination device that removes radioactive substances accumulated on liquid metal contact surfaces of liquid metal cooled nuclear reactor equipment, there is a dissolution tank that houses the equipment to be decontaminated, and a dissolution tank that houses the equipment to be decontaminated. Liquid metal cooling characterized by comprising: liquid metal placed in a tank; a pump that circulates the liquid metal in the dissolution tank; and a circulation speed control device that increases the circulation speed of the liquid metal during decontamination. Decontamination equipment for type nuclear reactor equipment. 7. In a decontamination device that removes radioactive substances accumulated on liquid metal contact surfaces of liquid metal cooled nuclear reactor equipment, there is a dissolution tank that houses the equipment to be decontaminated, and a dissolution tank that houses the equipment to be decontaminated. A liquid metal placed in a tank, a pump that circulates the liquid metal in the dissolution tank, and a pump that is installed in the middle of the circulation path of the liquid metal to remove the concentration of an element that accelerates the elution rate of radioactive substances contained in the liquid metal. At least two of the following three control devices: an accelerated element concentration control device that increases the concentration during decontamination, a temperature control device that increases the temperature of the liquid metal during decontamination, and a circulation speed control device that increases the circulation speed of the liquid metal during decontamination. A decontamination device for liquid metal cooled nuclear reactor equipment, comprising: 8. In a decontamination device that removes radioactive substances accumulated on liquid metal contact surfaces of liquid metal cooled nuclear reactor equipment, there is a dissolution tank that houses equipment to be decontaminated, and a dissolution tank that houses the equipment to be decontaminated. A liquid metal placed in a tank, a pump that circulates the liquid metal in the dissolution tank, and a pump that is installed in the middle of the circulation path of the liquid metal to remove the concentration of an element that accelerates the elution rate of radioactive substances contained in the liquid metal. A liquid metal comprising: an accelerated element concentration control device that increases the concentration during decontamination; a temperature control device that increases the temperature of the liquid metal during decontamination; and a circulation speed control device that increases the circulation speed of the liquid metal during decontamination. Decontamination equipment for cooled nuclear reactor equipment. 9. Exclusion of liquid metal cooled nuclear reactor equipment according to any one of claims 4 to 8, characterized in that a trap for capturing radioactive substances eluted into the liquid metal is provided before or after the melting tank. Dyeing equipment. 10. In a nuclear reactor system comprising a nuclear reactor, a primary cooling system that uses liquid metal as the primary coolant of the reactor, and a circulation pump that circulates the liquid metal in the primary cooling system, in the middle of the primary cooling system. A means for cutting off the front and back of the equipment provided, a liquid metal path that separately constitutes a closed loop for the liquid metal including the equipment when the equipment is cut off by the means, and a liquid metal path provided in the middle of the liquid metal path for removing the equipment. 1. A nuclear reactor system comprising: an accelerating element concentration control device that increases the concentration of an element that accelerates the elution rate of radioactive substances contained in the liquid metal in the path during the oxidation process. 11. In a nuclear reactor system comprising a nuclear reactor, a primary cooling system that uses liquid metal as the primary coolant of the reactor, and a circulation pump that circulates the liquid metal in the primary cooling system, in the middle of the primary cooling system. A means for cutting off the front and back of the equipment provided, a liquid metal path that separately constitutes a closed loop for the liquid metal including the equipment when the equipment is cut off by the means, and a liquid metal path provided in the middle of the liquid metal path for removing the equipment. an accelerating element concentration control device that increases the concentration of a radioactive substance elution rate accelerating element contained in the liquid metal in the route during decontamination; a temperature control device that increases the temperature of the liquid metal in the route during decontamination; and a temperature control device that increases the temperature of the liquid metal in the route during decontamination. A nuclear reactor device comprising one or both of two control devices of a circulation speed control device that increases the circulation speed of liquid metal. 12. The nuclear reactor device according to claim 10 or 11, characterized in that a trap for capturing eluted radioactive material is provided in the closed loop.