JPS582796A - Device and method of decontaminating equipment contaminated with radioactive material - 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 The present invention is applicable to decontamination of radioactive substances, such as 54 Mn 4IE@, which adhere to the surfaces of primary system equipment and pipes of atomic couplants. Related to decontamination equipment and method.

＾Fast Breeder - In power plants, fuel cladding tubes and core structural materials are irradiated with neutrons during operation, causing
A large amount of radioactive nuclides such as QCo, 紫◆, and blood are produced. These radionuclides elute into the coolant due to corrosion of core structural materials and fuel cladding materials.

The radionuclides released into the coolant are deposited on the warmer and piping surfaces of the primary cooling system while flowing together with the coolant within the primary cooling system. These radionuclides become a source of radiation exposure for workers during nuclear reactor maintenance inspections and repairs.

For example, in the case of a large-scale fast breeder on the scale of an experimental reactor, it is predicted that the radiation intensity at the main m-hour and near the pipes will reach about 10 roentgen/hour 2 to 3' years after the start of operation.

Therefore, during repair, it is necessary to remove radionuclides from such mats. Also, when disposing of III equipment that is no longer needed due to partial updating,
It is important to decontaminate and reduce attached radioactivity.

Here, "Mn" is "F'e (np)" Mn, "Co is 58Nl (ip) 58Co, 60Co is "Co (nr)
A nuclear reaction of 60Co produces nitrogen.

Stainless steel is used as the core structural material or fuel cladding material of fast breeder reactors. In this case, Fe, Ni.

Cobalt, whose main component is Cr, is mixed as an impurity. By reducing the content of cobalt, which is an impurity, it is possible to reduce the production of 60CO.On the other hand, 58CO is produced from nickel, which is the main component, but the half-life of 58CO is short. The main reason is that the elution into sodium is lower than that of 54Mn. The contribution to the radiation intensity of equipment and piping is small. On the other hand, 54Mn is produced from iron, which is the main component of stainless steel, and it also has the property of being easily eluted into the sodium coolant from stainless steel materials such as core structural materials and cladding tubes. device,
It accounts for the majority of radiation sources in piping, and there is no way to reduce it in the future.

For the above reasons, in the decontamination of fast reactor equipment, 54.
Decontamination of Mn is the most important step in reducing attached radioactivity.

Generally, methods for decontaminating radioactive substances adhering to equipment include 11) rubbing the surface with a brush, (2) cleaning with ultrasonic waves, and (3) chemical decontamination. 50
When considering the decontamination of a part of the primary system of a fast breeder reactor used in a 1116 sl metallic sodium coolant of 0υ or more, the radioactive substances attached to the am are JIK attached to the surface of the filter material. 1. Diffusion into the interior of the material. 111 for decontaminating sodium by washing, alcohol washing, etc., which has penetrated grain boundaries etc.
．． teha i is tt a and decontamination door! . This rounding 1.
Naturally, decontamination cannot be achieved by mechanical methods such as the above-mentioned brush cleaning method or ultra-chanical wave cleaning.

Chemical decontamination and washing with acids such as nitric acid, phosphoric acid, and citric acid are being researched as decontamination methods for the primary system II of rounded fast breeder reactors. In addition to the fact that the equipment is strongly corroded by the chemical solution and cannot be reused, there are also problems such as the treatment of A-liquid.
accompanies.

In addition, metallic sodium, which is used as a coolant in the primary cooling system of fast breeder reactors, reacts violently with the chemical solution used for underwater chemical cleaning while generating water volume, making it extremely difficult to decontaminate these. must be thoroughly washed of sodium.

In conclusion, as currently being developed for light water reactor power plants, system decontamination that decontaminates part or all of a nuclear reactor plant cannot be carried out using the above-mentioned friendly chemical cleaning method. And nine.

This invention was made in view of the nine conventional drawbacks mentioned above.
Fast reactor cooling fil! Particularly 5 attached to aS such as utensils etc.
Decontamination of major radionuclides such as 4Mn can be easily carried out, OTa works at appropriate intervals without requiring manual labor, and it is possible to decontaminate MS without damaging it due to corrosion. The purpose of the present invention is to provide an apparatus and method for decontaminating equipment contaminated with radioactive substances, such that the equipment can be easily reused after maintenance.

In this invention, metal sodium is filled into a container containing ms whose am is contaminated with a radioactive substance such as 54M, and the metal sodium is heated preferably to 450°C.
A decontamination device for equipment contaminated with radioactive substances, in which a getter material made of nickel or a nickel-based alloy is placed in a flow path that is heated and circulated, and whose surfaces are contaminated with radioactive substances. The contaminated equipment is immersed in metallic sodium, and the metallic sodium is fluidized while being heated to preferably 450"a or more, so that the contaminated radioactive substances in the vessel are eluted into the metallic sodium, and the nickel is leached into the metallic sodium. Alternatively, a method for decontaminating equipment contaminated with radioactive materials may be used, which is characterized by recovering nickel into a getter material made of an alloy containing nickel as a main component.

An embodiment of the present invention will be explained in detail below. 1st
The figure is an overall view showing an apparatus for decontaminating equipment contaminated with radioactive substances, showing an embodiment of the present invention. In this decontamination device, metal sodium 2 is filled in each container 1 made of stainless steel or the like and sealed with seven lunges 3, and inside this container 1 there is a Mn decontamination device made of nickel getter material at the bottom. 4, and above it is provided a table 5 through which liquid can freely flow, and on this table 5 is placed the equipment to be decontaminated, that is, the equipment to which the radioactive substance UN is attached. An outflow pipe 7 is provided at the top of the container 1 to allow the metal sodium 2 filled in the container 1 to flow out, and an inflow pipe 9 is provided at the bottom to allow the metal sodium 2 to flow into the container 1 from the outflow pipe 7 via the electromagnetic pump 8. 9 has a suction pipe 11 8Ff connected thereto via a pulp 10, and a tank 12 is provided at one end of this pipe 11. Naoyoshi! s1) The upper part 8 of the IJ rim is filled with rounded argon (person R) to prevent it from contacting oxygen and burning.
It is filled with a gas-like cover gas. Similarly, the space 15 above the sodium chloride 14 in the tank 12 is also filled with cover gas.

This device circulates the metal sodium 2 in the container 1B1 through the flow path leading to the electromagnetic pump 8 -> the intake pipe 9 -> the removal device 4 -> the object to be decontaminated 6 -> the outflow pipe γ -> the electromagnetic pump 8 by the operation of the electromagnetic pump 8. Particularly strangely, the radioactive substances attached around the object to be decontaminated 6 are eluted, and the radioactive substances in the metal sodium eluted by the removing device 4 are captured. Note that when this device is stopped, all the ml sodium 2 is drained into the tank 12, and the decontamination object 6 in the container is taken out from the top of the container a1 by opening and closing the 7-lunge 3. When operating the , first open the flank 3 and insert the inside of the container 1 (
Then, the equipment 6 to be decontaminated is inserted into the stand 5, and after that, the 7th room 3 is closed. Then, the inside of the paper chamber Ill is evacuated by an exhaust system (not shown). And pulp 10-
Then, suck up the IJum 14 in the tank 12 and pour it into the container.

Fill the inside with metallic sodium 2. After filling a certain amount of metal sodium, the pulp 10 is closed.

Next is 8I! A cover gas (input gas) is supplied to the space 13 in the upper part of the chamber 1 by a cover gas supply system shown in the figure until the pressure becomes close to normal pressure.

and 1) in the container 1 by means of a heating device (not shown).
Heat so that the temperature of 1its sodium becomes 450°C or higher. , the temperature is raised to a predetermined temperature of 450° C. or higher, and the pump 8 circulates metallic sodium.

It remains in this normal state for a certain period of time, and at this time it adheres to the surface of the object 6 to be decontaminated. 'S4M is gradually dissolved into this metal sodium, and this gold-sodium containing 54Mn is injected from the upper part through the pipe pump 8 to the lower part of SS1, and the nickel getter is removed by the 54M and removal device 4.
54M and flowing to the upper part of the container, Mn in the metallic sodium is captured by this removal device while passing through the removal device 4.

54Mn has been removed and the 9sodium is returned to the decontaminated body 60
Mn attached to the surface is eluted. While repeating such an operation for a certain period of time, the Mn that adheres to the object to be decontaminated 6 is decontaminated and all recovered in the removal station 4.

Next, after a certain period of time, the decontamination is complete and the circle is round.

Using pulp 10, all metal sodium 2 is transferred to tank 1.
After 9 days, 41J11 was cooled to room temperature and after 9 days,
72 Remove the object to be decontaminated by turning 3, at this point 54
As shown in Figs. 3 and 4, the Mno removal moth holder 4 consists of a cylinder 16 made of metal such as stainless steel or nickel, and a plate with mesh or holes provided at the top and bottom of the cylinder 11116. It is round and has a trap 19, which is made by wrapping a thin nickel plate in the same cylinder 1, and a trap 20 filled with a material such as nickel. By enlarging the contact area with the nickel getter surface while the sodium passes through, the 54In in the gold-metal sodium is efficiently collected on the nickel material.

Note that the decontamination effect of the present invention is limited to metals during decontamination.
It depends on the temperature of IJum and decontamination time, but for example,
91llll contaminated with 54Mn and made of 98U8-304
In the case of Ia, at a metal sodium heating temperature of 550°C, 2
After 40 hours of decontamination, 85 't41 #4 were removed. Decontamination tends to be completed in a shorter time as the temperature of sodium metal is higher, and it is effective at temperatures above 450°C. In addition, the Mn removal device 4 can be used repeatedly for a long period of time.

Next, other embodiments of the present invention will be described.

In the above embodiment, the Mn removal device 4 and the object to be decontaminated 6 were housed in the container 7a1, but as shown in FIG. These are different from A1! ! With 21.

A similar effect can be obtained by connecting the valve with a pipe 7.9 and a pump 8 and circulating sodium 2 between them. The removal device 4 is inserted and removed by removing the seven flange 22. This method can be used, for example, in case a1 in Figure 4.
If this is replaced with the reactor primary system vessel, by adding a device consisting of pipe 7.9, 4 pump 8, capacity 8B21, and Mn removal device 4 to this reactor vessel, the contamination in the reactor plant can be removed. - It is possible to decontaminate part or all of the contaminated equipment. Namely.

It also enables "system decontamination."

As detailed above, according to the present invention, instead of using a cleaning solution such as acid as in the past, cleaning can be easily and efficiently done by simply immersing it in metallic sodium, the same coolant used in the sounding reactor, for a while. It can decontaminate nine radioactive substances attached to equipment.

This is easy to do without any manual effort, and it won't corrode the equipment or cause it to roll up into pieces. Therefore, it is extremely advantageous when maintaining the equipment and reusing it in the future.

! 9. The present invention is suitable for rounded remote control, which is extremely simple to operate, and can greatly contribute to reducing the radiation exposure of operators.

4, riamom single *vi* - FIG. 1 is a configuration diagram of an apparatus showing an embodiment of the present invention.

@Figures 2 and 113 are S4Mn# used in the present invention.
FIG. 4 is a partially cutaway perspective view showing the shape of the removing device, and FIG. 4 is a configuration diagram of the device showing another embodiment of the present invention.

1... Container, 2... Metallic sodium, 4... Excluding -
Equipment, 6...The surface is contaminated with radioactive substances.
11 (object to be decontaminated), 7... Outflow pipe, 8... Electromagnetic pump, 9... Inflow pipe.

Figure 1 /? Ia

Claims (1)

[Scope of Claims] 11) A container for storing 1IIII whose surface is contaminated with a radioactive substance, round metal sodium filled in the container, a flow path for circulating the metal sodium through the container, and a getter material made of nickel or an alloy containing nickel as a main component disposed in the flow path;
1. decontamination equipment. (2) Place the getter material in the flow path inside the container.
1. Claim 1: A decontamination device for molds contaminated with radioactive materials. (3) A decontamination device for a vessel contaminated with radioactive materials as claimed in claim 1, characterized in that a getter material is placed in a flow path outside the container. (4) Heat fl dll sodium at 450'C in a container.
A decontamination device for equipment contaminated with radioactive substances as set forth in claim 1, characterized in that it is equipped with a heating device that heats the equipment to a temperature higher than that of the previous claim. (5) A device whose surface is contaminated with radioactive material is immersed in metallic sodium, and the metallic sodium is allowed to flow to remove the contaminated radioactive material from the device into the metallic sodium. A decontamination method for equipment contaminated with radioactive materials, which is characterized by recovering the discharged material into a getter material made of nickel or an alloy containing nickel. (6) Patent claim OwA, Box 5, characterized in that the metallic sodium flowing in the container is heated to 450"O or more.
Decontamination method for radioactive substances ÷ contaminated equipment as described in Section 9.