JP3829271B2 - Reactor internal structure unloading method and metal powder recovery device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for recovering metal powder generated when a nuclear plant internal structure or the like is cut.
[0002]
[Prior art]
In the reactor internal structure in the BWR power plant, replacement with new materials or the like, or disposal after the end of its useful life is under consideration. In existing reactors, the reactor structure itself is activated or attached with radioactive cladding, and therefore, cutting for replacement and dismantling is mainly performed in water from the viewpoint of reducing exposure. For example, a structure such as a reactor shroud is cut in the reactor, transported from the reactor to a storage pool, shredded for volume reduction in the storage pool, and then transported. As a cutting method, there are mechanical cutting with a cutter or a water jet containing an auxiliary material, or thermal cutting with plasma or electric discharge.
[0003]
When the structure is cut, metal powder is generated. Large metal powder (particle diameter of several mm) is deposited on the bottom, but small powder (several μm) is floating in water. As a method for recovering such metal powder, for example, Japanese Patent Application Laid-Open No. 10-123285 proposes sucking the metal powder together with water with a pump and then recovering it with filter filtration.
[0004]
Cutting of the structure is mainly performed in water as described above, but cutting in the air is also possible. When cutting in the air, the metal powder floating in the air is collected using an air filter.
[0005]
[Problems to be solved by the invention]
However, in general, filter filtration devices are equipped with pumps, pipes, mounts, etc., require a large space, and the filters and filter containers after metal powder recovery have a high dose, which themselves are radioactive waste. It becomes a thing.
[0006]
In addition, there is a concern about exposure during maintenance of the filter device, particularly during filter replacement work.
[0007]
An object of the present invention is to recover metal powder generated by cutting without causing problems such as an increase in radioactive waste or exposure when the reactor internal structure is cut and carried out.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, the metal powder recovery device of the present invention is configured to perform plasma gas cutting of a nonmagnetic metal material of the reactor internal structure when carrying out plasma gas cutting of the reactor internal structure. The generated metal powder is collected by being attracted to a magnet.
[0009]
The present invention is based on the following new findings by the inventors. The reactor internal structure is mainly made of austenitic stainless steel or nickel-base alloy and is non-magnetic. However, for example, when stainless steel is thermally cut with plasma gas, it has been found that the cut metal powder has magnetism. The reason is considered as follows. That is, Cr having a low boiling point evaporates due to heat at the time of cutting, and Cr is condensed again in the cooling process. When the Cr content increases, the austenite phase changes from a ferrite phase (magnetic body), so that the cut metal powder of austenitic stainless steel has magnetism. At this time, the metal powder includes those in which the entire metal powder is ferritized and those in which a part of the ferritic metal is adhered. Further, since the cut portion becomes high temperature, as shown in the Raman spectrum measurement result of FIG. 7, magnetic Fe ₃ O ₄ oxide is generated on the surface of the cut metal powder. Since the whole or the surface of the metal powder has magnetism due to the phase change and the generation of oxide, the metal powder can be recovered by a magnet when the material is originally non-magnetic.
[0010]
According to the above configuration, since only the portion that directly adsorbs the metal powder is the radioactive waste, an increase in the radioactive waste can be suppressed. Further, the portion directly adsorbed with the metal powder may be discarded after use, so that it is not exposed.
[0015]
The present invention also relates to a metal powder recovery device for magnetically attracting and recovering metal powder generated when a non-magnetic metal material of austenitic stainless steel or nickel base alloy is cut by plasma gas. A magnet storage container that is freely stored, and a drive unit that moves the magnet closer to or away from the inner wall surface of the magnet storage container. The metal powder is adsorbed on the outer wall surface of the container, and the adsorption of the metal powder is released when the metal powder is separated from the inner wall surface of the magnet storage container.
[0016]
Furthermore, the present invention is a metal powder recovery device for recovering metal powder generated by plasma gas cutting of austenitic stainless steel or nickel-based alloy non-magnetic metal material by magnetism, in which a magnet is housed. When the magnet is attracted to the outer wall surface of the magnet housing container when the magnet has a certain polarity, the polarity is reversed. The feature is that the adsorption of the metal powder is released.
[0017]
According to each said structure, since it is only a magnet storage container that contacts metal powder directly, the increase in radioactive waste can be suppressed. Moreover, since the magnet storage container after use should just be discarded, it is not exposed.
[0020]
The present invention also provides a suction pump for sucking together with water the metal powder generated when plasma gas cutting of a non-magnetic metal material of austenitic stainless steel or nickel base alloy in water, and taking the water into the metal from the water And a magnetic recovery means for recovering powder by magnetic adsorption with a magnet.
[0021]
In order to collect the metal powder contained in the water sucked by the suction pump, a filter is usually used. However, if the metal powder concentration is high, the filter is clogged in a short time and must be replaced. At this time, there is a possibility of exposure. According to the above configuration, the metal powder is adsorbed by the magnetic recovery means and the metal powder concentration is lowered. Therefore, it is possible to reduce the replacement frequency of the filter provided at the subsequent stage of the magnetic recovery means and to suppress the exposure.
[0022]
In constructing the above metal powder recovery device, the following elements can be added.
[0023]
(1) The magnet is a magnetic material or an electromagnet including any of iron, cobalt, samarium, neodymium, boron, and praseodymium.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a conceptual diagram showing a state in which metal powder is collected by the metal powder collecting apparatus according to the present invention. The work pit 15 is filled with water, and a gantry 12 is installed in the work pit 15, and the reactor structure 1, which is a material to be cut, is placed on the gantry 12. The structure 1 is made of a nonmagnetic metal (for example, austenitic stainless steel or inconel steel). The work pit 15 may not be filled with water and may be in the air.
[0025]
In the work pit 15, the cutting device 2 is suspended from above, and is disposed opposite to the portion of the structure 1 to be cut. The cutting device 2 thermally cuts the structure 1 with a gas, electric discharge or laser cutting device. When the structure 1 is thermally cut, metal powder 7 is generated from the structure 1, and the metal powder 7 is deposited on the bottom of the work pit 15. A work carriage 13 is provided above the work pit 15, and the operator 14 operates the collection guide 8 with the magnet 3 attached to the tip from the work carriage 13 in the work pit 15, so that the metal powder 7 Perform recovery work.
[0026]
FIG. 2 shows the detailed structure of the magnet 3 mounting portion at the tip of the collection guide 8. As shown in the figure, the magnet 3 is housed in a rectangular parallelepiped magnet housing container 9. The collection guide 8 is connected to the upper surface of the magnet storage container 9 via a lever lock coupler 17. A drive cylinder 18 is provided in the magnet storage container 9, and the magnet 3 is fixed to the lower end of the drive cylinder 18. A gas supply / exhaust line 16 is connected to the drive cylinder 18, and the drive cylinder 18 is driven by supplying or exhausting pressurized gas through the gas supply / exhaust line 16.
[0027]
Next, an operation of recovering the metal powder generated when the reactor internal structure is cut by the metal powder recovery apparatus having the above configuration will be described. FIG. 6 shows a series of work steps for carrying out the reactor internal structure including the metal powder recovery work.
[0028]
First, when the structure 1 is cut, as shown in FIG. 1, the structure 1 is placed on the gantry 12 in the work pit 15, and the cutting device 2 is positioned at a position where the structure 1 is to be cut. Then, the structure 1 is thermally cut (step S1: hereinafter, step numbers are those for FIG. 6). At this time, metal powder 7 is generated along with the cutting. The operator 14 operates the collection guide 8 to move the magnet storage container 9 to a place where the metal powder 7 is deposited (step S2). Then, as shown in FIG. 2, high-pressure gas is supplied to the supply line side of the gas supply / exhaust line 16 as indicated by the arrow in FIG. 2, and the magnet 3 is moved downward to approach the bottom surface of the magnet storage container 9. Let Then, the magnetic attraction force of the magnet 3 acts through the plate on the bottom surface of the magnet storage container 9, and the metal powder 7 is adsorbed on the bottom surface of the magnet storage container 9. At this time, the operator 14 operates the collection guide 18 up, down, left, and right to sufficiently adsorb the metal powder 7 on the bottom surface of the magnet storage container 9 (step S3).
[0029]
Next, the operator 14 operates the collection guide 18 in a state where the metal powder 7 is adsorbed on the bottom surface of the magnet storage container 9, and in FIG. 1, the magnet storage container 9 is moved upward and further to the right. And move. Then, as shown in FIG. 3, the magnet storage container 9 is positioned above the collection container 4 installed at the bottom of the work pit 15 (step S4). In this state, the high-pressure gas supplied to the drive cylinder 18 is exhausted through the exhaust line side of the gas supply / exhaust line 16 as shown by the arrows in FIG. 4, and the magnet 3 is moved upward. The magnet storage container 9 is separated from the bottom surface. Then, since the magnetic attraction force of the magnet 3 acting through the plate on the bottom surface of the magnet storage container 9 is inversely proportional to the square of the distance, the attraction force decreases, and the metal powder adsorbed on the bottom surface of the magnet storage container 9 7 leaves the bottom surface and falls into the collection container 4 (step S5).
[0030]
By repeating the recovery operation described above, all the deposited metal powder 7 can be recovered in the recovery container 4 (step S6). At the end of the collection operation, as shown in FIG. 5, the operator 14 operates the lever lock coupler 17 provided at the connection portion between the collection guide 8 and the magnet storage container 9 with the lever opening / closing jig 19. Then, the magnet storage container 9 is separated from the collection guide 18. At this time, the gas supply / exhaust line 16 is also disconnected in the middle. Thereby, only the magnet storage container 9 can be discarded (step S7). Then, the cut structure 1 is stored in the work pit 15 for a certain period and then carried out (step S8).
[0031]
According to the present embodiment, since only the metal powder 7 and the magnet storage container 9 are added as waste, an increase in waste can be suppressed.
[0032]
Moreover, when the structure 1 is a reactor internal structure, the metal powder 7 generated by cutting contains a radioactive substance, but according to the present embodiment, the length of the recovery guide 8 is changed. Alternatively, the surface of the magnet storage container 9 is washed with water, so that it can be recovered by remote control from a position where the radiation dose can be allowed.
[0033]
(Embodiment 2)
8 to 10 show a second embodiment of the present invention. In the present embodiment, a plate-like magnet 20 is provided in the magnet housing container 9 so as to be rotatable around a support shaft 21 that is disposed horizontally. An operation rope 10 is connected to the magnet 20, and the magnet 3 rotates by operating the operation rope 10. Here, when the operation rope 10 is not operated, the magnet 20 is configured such that the N pole comes close to the bottom surface of the magnet storage container 9.
[0034]
In the above configuration, when the operation rope 10 is not operated, the N pole of the magnet 20 is located close to the bottom surface of the magnet storage container 9, and the metal powder 7 is adsorbed on the bottom surface of the magnet storage container 9. When the operation rope 10 is pulled up, the magnet 20 rotates as shown by the arrow in FIG. 10, the N pole moves away from the bottom surface of the magnet storage container 9, and the attracting force decreases. The powder 7 leaves the bottom surface of the magnet storage container 9 and falls into the collection container 4.
[0035]
Thereafter, when the operation rope 10 is returned, the magnet 20 rotates in the reverse direction, and the N pole is located at the bottom of the magnet storage container 9. Thereby, the metal powder 7 can be collected again. Further, for the metal powder 7 that can be adsorbed by the S pole, the S pole is positioned at the bottom of the magnet storage container 9 while the operation rope 10 is pulled, and after the metal powder 7 is recovered, the upper part of the recovery container 4 is recovered. If the operation rope 10 is returned, recovery and reuse are possible.
[0036]
Reference Example 1 FIGS. 11 to 12 show Reference Example 1 of the present invention. In this reference example , a rod-like or plate-like magnet 30 is locked to the magnet chuck 8A at the tip of the collection guide 8. An operation rope 10 is attached to the magnet chuck 8A, and when the operation rope 10 is pulled up, the magnet 30 of the magnet chuck 8A is unlocked.
[0037]
In the above configuration, the metal powder 7 is attracted to the magnet 30 by operating the collection guide 8 as indicated by the arrow in FIG. In this state, when the magnet 30 is brought above the collection container 4 and the operation rope 10 is pulled up, the magnet chuck 8A releases the lock of the magnet 30, and the magnet 30 collects the metal powder 7 while adsorbing it. Falls into the container 4. Thereby, the metal powder 7 can be recovered in the recovery container 4.
[0038]
In the present embodiment, since the metal powder 7 is brought into direct contact with the magnet 30, the magnet 30 is disposable every time, but since the collection part is constituted by only the magnet 30, the metal powder deposited on the narrow part Convenient to recover 7.
[0039]
Reference Example 2 FIGS. 13 to 16 show Reference Example 2 of the present invention. In this reference example , a cylindrical magnet 40 is provided, and tires 41 are attached to both ends of the magnet 40. A support member 42 is attached to the central axis of the tire 41, the tire 41 is supported by the support member 42 and rotates, and the magnet 40 rotates as the tire 41 rotates. Further, the tip of the collection guide 8 is fixed to the support member 42.
[0040]
Further, a box-shaped collection container 43 is provided so as to face the cylindrical surface of the magnet 40, and the collection container 43 is supported on the rotation shaft of the tire 41. The opening of the collection container 43 is opposed to the cylindrical surface of the magnet 40, and the peeling member 44 whose tip is always in contact with the cylindrical surface of the magnet 40 is located above the opening of the collection container 43. Is attached. A small-diameter tire 45 is rotatably attached to the collection container 43.
[0041]
In the above configuration, when the metal powder recovery device is installed at the bottom of the work pit 15 and the recovery guide 8 is operated in the horizontal direction as shown in FIG. 15, the tire 41 moves while rotating on the bottom of the work pit 15. As a result, the magnet 40 rotates. At this time, if the metal powder 7 is deposited on the bottom of the work pit 15, the magnet 40 rotates while adsorbing the metal powder 7 on the cylindrical surface. Then, the metal powder 7 adsorbed on the cylindrical surface is peeled off from the cylindrical surface of the magnet 40 by the stripping member 44 and recovered in the recovery container 43.
[0042]
When a certain amount of the metal powder 7 is collected, the metal powder 7 is deposited only on the stripping member 44 and its periphery, and is not taken into the collection container 43 and may spill out of the container. In that case, as shown in FIG. 16, the collection guide 8 is pulled upward and the collection container 43 is vertically oriented, so that the metal powder 7 falls to the bottom of the collection container 43 and can be collected again. It becomes.
[0043]
According to the present embodiment, the metal powder 7 can be easily recovered even if the cutting portion is wide and the metal powder 7 is scattered over a wide area at the bottom of the work pit 15.
[0044]
( Third Embodiment) FIG. 17 shows a third embodiment of the present invention. The present embodiment is for recovering the metal powder 7 having a small particle diameter diffused into water when the structure 1 is cut, and includes a water intake 50, a suction pump 51, a recovery container 52, and a purification filter 53. Yes. In addition, a plurality of rod-shaped or plate-shaped magnets 54 are installed inside the recoverability container 52.
[0045]
In the above configuration, the metal powder 7 is sucked together with water from the water intake 50 and is introduced into the collection container 52 through the pipe 55. Since a plurality of magnets 54 are installed inside the collection container 52, the metal powder 7 in the water is adsorbed by the magnets 54 while passing through the collection container 52. The water that has passed through the recovery container 52 is introduced into the purification filter 53, where the remaining metal powder 7 is recovered. In general, it is introduced directly from the suction pump 51 into the purification filter 53, but it is introduced into the purification filter 53 by installing a collection container 52 in the preceding stage of the purification filter 53 as in the present embodiment. Therefore, the consumption of the purification filter 53 is greatly reduced, and the generation of waste can be greatly suppressed.
[0046]
According to the present embodiment, the metal powder 7 having a small particle size that diffuses upward can be easily recovered, like the metal powder 7 having a large particle size deposited in the lower part.
[0047]
【The invention's effect】
As described above, according to the present invention, the metal powder generated when cutting a nonmagnetic metal material such as a reactor structure is made radioactive by utilizing the fact that the nonmagnetic metal material is magnetized by plasma gas cutting. The waste can be collected without increasing it.
[0048]
Also, the structure of the metal powder recovery device is simple, and it is not wasted if it is discarded when the recovery operation is completed. Therefore, it becomes possible to prevent an operator's exposure.
[Brief description of the drawings]
FIG. 1 is a diagram showing a state in which metal powder is adsorbed by a metal powder recovery apparatus according to Embodiment 1 of the present invention.
FIG. 2 is an enlarged perspective view of a magnet mounting portion in FIG.
FIG. 3 is a diagram showing a state in which metal powder is collected in a collection container by the metal powder collection device according to Embodiment 1 of the present invention.
4 is an enlarged perspective view of a magnet mounting portion in FIG. 3. FIG.
FIG. 5 is a perspective view showing a state where a magnet mounting portion is separated from a collection guide.
FIG. 6 is a flowchart showing a procedure for carrying out a reactor internal structure.
FIG. 7 is a diagram showing the results of Raman spectrum measurement.
FIG. 8 is a perspective view showing a state in which metal powder is adsorbed by the metal powder recovery device according to Embodiment 2 of the present invention.
9 is a view showing a state in which the metal powder adsorbed by the metal powder recovery device of FIG. 8 is recovered in a recovery container.
FIG. 10 is a diagram illustrating the behavior of a magnet in a magnet storage container.
FIG. 11 is a perspective view showing a state in which metal powder is adsorbed by the metal powder recovery apparatus according to Reference Example 1 of the present invention.
12 is a view showing a state in which the metal powder adsorbed by the metal powder recovery device of FIG. 11 is recovered in a recovery container.
FIG. 13 is a perspective view showing a state in which metal powder is adsorbed by the metal powder recovery device according to Reference Example 2 of the present invention.
14 is an enlarged perspective view of a portion that adsorbs metal powder in the metal powder recovery device of FIG. 13;
FIG. 15 is a diagram showing a state in which the metal powder is recovered by moving the metal powder recovery device in the horizontal direction.
FIG. 16 is a diagram showing a state in which the metal powder is recovered by moving the metal powder recovery device upward.
FIG. 17 is a diagram showing a configuration of a metal powder recovery device according to Embodiment 3 of the present invention.

Claims (4)

A metal powder recovery device that collects metal powder generated by plasma gas cutting of austenitic stainless steel or nickel-based alloy non-magnetic metal material by magnetism, and the magnet is movably stored inside A storage container, and driving means for moving the magnet closer to or away from the inner wall surface of the magnet storage container, and when the magnet approaches the inner wall surface of the magnet storage container, An apparatus for recovering metal powder, wherein the metal powder is adsorbed and desorbed when separated from the inner wall surface of the magnet storage container. A metal powder recovery device for magnetically attracting and recovering metal powder generated when a non-magnetic metal material of austenitic stainless steel or nickel-base alloy is cut by plasma gas, and a magnet storage container in which a magnet is stored; Magnetic pole reversing means for reversing the polarity of the magnet, and the magnet adsorbs the metal powder on the outer wall surface of the magnet storage container when the magnet has a certain polarity, and adsorbs the metal powder when the polarity is reversed. Metal powder recovery device characterized by unwinding. A suction pump for sucking together with water the metal powder generated when plasma gas cutting is performed on a non-magnetic metal material of austenitic stainless steel or nickel base alloy in water, and the metal powder is magnetized from the water by a magnet. A metal powder recovery device comprising a magnetic recovery means for adsorbing and recovering. The metal powder recovery apparatus according to any one of claims 1 to 3, wherein the magnet is a magnetic material or an electromagnet including any one of iron, cobalt, samarium, neodymium, boron, and praseodymium. apparatus.

Images