JP2000075095A - Decontamination device of radioactivity contaminated matter and recovery method for abrasive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decontaminate components and structures with high speed solid- liquid discharge flow of steam injector and abrasive and reduce secondary waste generation and suppress recontamination by applying hardly crashed ceramics particles. SOLUTION: To a steam water mixing nozzle 2 of a steam injector consisting of a water nozzle 1 and a steam nozzle 3, abrasive 13 is supplied to grind oxide film and metal parent material of object to be processed 5. Compressed air and abrasive are sent with pressure to building-embedded pipes of nuclear facilities to grind oxide film and metal parent material inside the pipes. The building concrete of the nuclear facility is ground by a portable grinding device for supplying compressed air and abrasive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to radioactively contaminated equipment and structural materials (buildings, buildings, etc.) composed of metal and concrete during the operation of nuclear facilities or the decommissioning of nuclear reactors.
Equipment for decontamination of radioactive contaminants to remove radioactive contaminants or oxide film, which is a major source of contaminants, from pipes, tanks, steam turbines, etc., and separation of grinding powder adhering to abrasive particles used for decontamination The present invention also relates to a method for collecting abrasives for collecting and reusing the abrasives.

[0002]

2. Description of the Related Art Conventionally, as a decontamination device for radioactively contaminated equipment, structural materials, etc. (1) For example, in Japanese Patent Application Laid-Open No. 10-85634, "A two-phase jet consisting of a steam jet and a water jet is generated. A jet processing apparatus that applies the two-phase jet to a finishing process of machining, a deposit on a metal surface in a surface cleaning process, and deburring accompanying machining, etc. "is disclosed.

(2) An apparatus has already been put into practical use for removing plastic rust from the inner surface of a pipe by grinding a plastic ball with a grindstone under pressure to a buried pipe on a building floor by water pressure. (3) A mechanical crusher with large impact and reaction such as a chipping hammer such as a hand-held small vibration chisel, a concrete cutter, or a giant breaker (a gigantic vibrating wedge attached to the arm of a heavy machine), or an electromagnetic device The Japan Atomic Energy Research Institute (JAERI-Tech) discloses an apparatus for partially decontaminating building concrete using a large-scale heating device that crushes concrete by heat using induction or microwaves.

(4) Grinding powder (material to be processed) adhered to ceramic particles of an abrasive (projection material) is removed by baking to remove the grinding powder, and a method of removing a surface adhering substance of the projection material to collect the abrasive is known, for example. It is disclosed in JP-A-9-225835.

(5) Injection of partially stabilized zirconia-based sintered particles containing zirconium oxide as a main component and yttrium oxide added for blast decontamination of metal waste generated during operation of a nuclear facility and decommissioning of a nuclear reactor. A decontamination method and a decontamination apparatus to be performed are disclosed in, for example, JP-A-9-218986.

[0006]

In the prior art (1), a two-phase jet consisting of a steam jet and a water jet has a decontamination effect on the loosely adhered contamination on the metal surface of the object to be treated. is there. However, it is difficult to grind up to the metal base material only by the jet by the water pressure. Therefore, there is a problem that the contaminants (hard contaminants) in the metal base material and the oxide film generated by corrosion of the metal base material cannot be removed by grinding.

In the prior art (2), since the plastic ball with a grindstone is relatively large, there is a problem that it is difficult to apply it to a small-diameter pipe of about 80 A embedded in the building frame of a nuclear facility.

In the prior art (3), chipping hammers, concrete cutters, giant breakers, etc. have large vibrations and noises in the equipment, and electromagnetic induction and microwaves generate electromagnetic noises. Protection measures are needed. In addition, a hand-held measuring device such as a survey meter is separately used for confirmation measurement after concrete decontamination. However, since the measurement is performed manually, there is a problem that the number of work steps is enormous.

In the prior art (4), the method of firing the ceramic particles is effective in removing the deposit.
However, the particles cannot be reused without cooling. In order to continuously and repeatedly reuse ceramic particles as an abrasive, there is a problem that a simple apparatus is required.

In the prior art (5), which relates to the above item (4), the grinding powder fixed to the abrasive cannot be separated by the cyclone separator. Since the grinding powder contains a radioactive substance, when the abrasive is reused, the object may be re-contaminated. In addition, if grinding powder adheres around the abrasive, there is a problem that the grinding ability is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a radioactive contaminant capable of reliably decontaminating radioactivity taken into equipment and structural materials by a high-speed solid jet comprising a steam injector and an abrasive. The present invention provides a decontamination apparatus of the type described above. Another object of the present invention is to provide a method for decontaminating radioactive contaminants that can reduce the amount of secondary waste generated and suppress recontamination by using ceramics that are difficult to crush.

Further, the present invention is a method for separating an abrasive, wherein the abrasive used in the decontamination apparatus for radioactive contaminants is reused, so that the abrasive powder attached to the abrasive particles can be separated and reused. Is to provide.

[0013]

The invention according to claim 1 is
A water nozzle having a cylindrical portion sealed at one end and a tapered portion gradually reduced in diameter at the other end opening of the cylindrical portion and a jetting hole at the tip of the tapered portion, and the water nozzle from the outer peripheral side of the cylindrical portion of the water nozzle. A steam nozzle that covers the tapered portion and extends on an extension of the tapered portion and is fitted concentrically to the water nozzle; a mixing nozzle provided at an end of the tapered portion of the steam nozzle; An abrasive supply pipe connected to a side surface of the nozzle, and an abrasive supply connected to the abrasive supply pipe via a supply valve are provided.

According to a second aspect of the present invention, a supply-side connector for supplying compressed air and abrasives is connected to one of the buried pipes buried in a building of a nuclear facility, and the inside of the buried pipe is connected to the other of the buried pipes. A discharge-side connector for discharging the decontaminated abrasive, grinding powder and compressed air is connected, and the abrasive used for the decontamination is collected and reused in the discharge-side connector. And a filter is connected to the grinding powder discharge side of the cyclone separator.

According to a third aspect of the present invention, there is provided a decontamination apparatus main body,
An abrasive supply / recovery device connected via a supply hose for supplying abrasive to the decontamination device body and a recovery hose for recovering the decontaminated abrasive, and a compressed air supply hose connected to the abrasive supply / recovery device And a blast gun, an abrasive collection pipe, a scattering prevention brush, a radiation detector and a measuring unit are integrally incorporated in the decontamination apparatus main body. Is characterized in that the abrasive feeder, cyclone separator and dust collector are integrally incorporated.

According to a fourth aspect of the present invention, the decontamination apparatus main body is provided with a rail for moving the radiation detector from the main body toward the building concrete floor, and the radiation detector is mounted along the rail. It is characterized in that it is configured to scan and measure radiation on the concrete floor of the building.

According to a fifth aspect of the present invention, the abrasive is partially stabilized zirconia-based sintered particles containing zirconium oxide as a main component and yttrium oxide added thereto, and has a spherical, cylindrical, or square particle shape. It is characterized by being shaped or crushed.

The invention according to claim 6 is provided with two rollers arranged in parallel so as to rotate in opposite directions while being pressed against each other by a spring force, and is used for decontamination between the mating surfaces of the two rollers. The abrasive is supplied, and the abrasive is compressed and polished with the pressing force of the roller to separate grinding powder adhering to the abrasive, thereby collecting the abrasive.

According to a seventh aspect of the present invention, an abrasive used for decontamination is supplied between a facing fixed disk and a rotating disk having an opening at the center, and the pressing force and the rotating force between the disks are used. The method is characterized in that the abrasive is compressed and polished to separate grinding powder adhering to the abrasive.

[0020] In the invention according to claim 8, the abrasive used for decontamination is supplied into a mortar, and the abrasive is compressed and polished by mechanically rotating a pestle to adhere to the abrasive. It is characterized in that the grinding powder is separated.

According to a ninth aspect of the present invention, the abrasive used for decontamination is supplied to a closed container, and the closed container is attached to a vibrating device or the like, and vibrated to vibrate the abrasives or the abrasive and the closed container. Abrasives are collected by separating grinding powder adhering to the abrasives by friction and collision with the inner wall.

According to a tenth aspect of the present invention, the abrasive used for decontamination is sent to a cyclone separator to separate grinding powder adhering to the abrasive, recovering the abrasive, and removing the recovered abrasive. The grinding powder is reused for decontamination, and collected by a filter connected to the grinding powder discharge side of the cyclone separator.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of an apparatus for removing radioactive contaminants according to the present invention will be described with reference to FIGS. 1 (a) and 1 (b). FIG. 1A is a longitudinal sectional view partially showing a basic configuration of a radioactive contaminant decontamination apparatus by a piping system for explaining a first embodiment according to the present invention, and FIG. FIG.
FIG. 2A is an enlarged longitudinal sectional view of part A, and part A partially shows the mixing nozzle 2 and the abrasive supply pipe 10.

In FIG. 1, reference numeral 1 denotes a water nozzle for jetting a liquid-phase water jet, and the water nozzle 1 is provided with a cylindrical portion 1a having one end sealed and an opening at the other end of the cylindrical portion 1a. It has a conical tapered portion 1b formed with a reduced diameter, and an outlet 1c at the tip of the tapered portion 1b.

A water supply pipe 8 is connected to the sealed end of the cylindrical portion 1a of the water nozzle 1 via a water supply valve 9, and water is supplied into the water nozzle 1 through the water supply pipe 8 and flows therein. The water that has flowed into the water nozzle 1 is configured such that a water jet 14 is jetted from the jet hole 1c in a cylindrical shape.

The steam nozzle 3 is provided so as to cover the tapered portion 1b from substantially the outer peripheral side of the central portion of the cylindrical portion 1a of the water nozzle 1 and to cover the water jet 14 extending on an extension of the tapered portion 1b. Have been. The steam nozzle 3 is fitted around the water nozzle 1 concentrically. Steam nozzle 3
Has a cylindrical portion 3a, a curved portion 3b located downstream of the cylindrical portion 3a, and an injection port 3c at the tip of the curved portion 3b. The curved portion 3b has a tapered conical shape depressed inward.

The injection port 3c of the steam nozzle 3 has a curved portion 3b
Of the water nozzle 1 of FIG. The cross section perpendicular to the axial direction formed by the water nozzle 1 and the steam nozzle 3 is an annular cross section, and this annular cross section has a minimum cross section 3 d before reaching the injection port 3 c of the steam nozzle 3.

The area of the minimum cross section 3d is set to be larger than a value set so as to thermally balance the supersonic water jet 15 and the water jet 14 described later. The water nozzle 1 is disposed so as to be movable in the axial direction with respect to the steam nozzle 3, and the area of the minimum cross section 3d can be made by moving the water nozzle 1 in the axial direction.

A steam supply pipe 6 is connected to the cylindrical portion 3 a of the steam nozzle 3 via a steam supply valve 7, and a vapor flow 4 in a gas phase is supplied from the steam supply pipe 6 into the steam nozzle 3. Is done. When the steam flow 4 passes through the minimum cross-section 3d, it becomes supersonic and becomes a high-speed steam jet, that is, a supersonic water jet 15.

The mixing nozzle 2 is connected to the injection hole 3c of the steam nozzle 3 smoothly. The mixing nozzle 2 is formed to have a tapered shape, and an injection hole 2a is formed at the tip of the mixing nozzle 2 at a right angle to the axial direction.

An abrasive supply pipe 10 is connected in a substantially vertical direction to a substantially central portion of the mixing nozzle 2, and an abrasive supply device 11 is connected to the abrasive supply pipe 10 through an abrasive supply valve 12. I have. The abrasive supply unit 11 is filled with a granular abrasive 13, and the abrasive 13 falls through the abrasive supply pipe 10 into the mixing nozzle 2 and is supplied.

Since the supersonic water jet 15 is excessively supplied to the water jet 14 beyond the heat balance, the supersonic water jet 15 is injected from the outer peripheral surface of the cylindrical water jet 14 into the mixing nozzle 2. Thus, a supersonic water jet 15 composed of the water jet 14 and water vapor is formed.

Since the abrasive 13 is supplied to the mixing nozzle 2 from the abrasive supply pipe 10, the supersonic water jet 15 and the abrasive
The high-speed solid-liquid jet 16 composed of 13 jets 2a of the mixing nozzle 2
Squirted from. Here, the water jet 14 is, for example, about 10 m / se.
The supersonic water jet 15 has a flow velocity of about 500 m / sec.

The high-speed solid-liquid jet 16 ejected from the injection hole 2a
Is directly injected as a free jet onto the workpiece 5 placed at a fixed distance from the injection hole 2a. The high-speed solid-liquid jet 16 injected from the injection hole 2a of the mixing nozzle 2
Collide with Thus, the abrasive 13 in the high-speed solid-liquid jet 16
As a result, the surface of the workpiece 5 is ground, and the radioactivity taken into the workpiece 5 can be reliably removed.

Next, the function and effect of the first embodiment will be described. High-speed solid-liquid jet described in the first embodiment
When the object 5, for example, a metal surface is ground to remove radioactivity at 16, it is necessary to select particles that are hard to be crushed in order to reduce the used abrasive generated as secondary waste. Further, in the case of the crushed shape, the stress is concentrated at the corners and crushed, so that a spherical shape is desirable. Spherical ceramic particles shown in Table 1 are known as particles having excellent wear resistance and being hardly crushed.

[0036]

[Table 1]

If the specific gravity of the particles is heavy, the grinding ability is large, and if the hardness and the fracture toughness of the particles are large, it is difficult to be crushed.
Therefore, 95% by weight zirconium oxide (ZrO
₂ ) Select partially stabilized zirconia-based sintered particles composed of 5 wt% yttrium oxide (Y ₂ O ₃ ).

FIG. 2 shows the result of a grinding test of carbon steel as the workpiece 5 to confirm the effect of the first embodiment. Spherical partially stabilized zirconia sintered particles having an average particle diameter of 95 μm are used as the abrasive 13, and the supersonic water jet and the high-speed solid-liquid jet 16 made of the abrasive are converted to carbon steel by the decontamination apparatus shown in FIG. Was sprayed for 30 seconds. Thereafter, the surface roughness of the carbon steel was measured with a surface roughness meter.

FIG. 2A shows the surface roughness of the carbon steel before the test, and FIG. 2B shows the surface roughness of the carbon steel after the test. Uneven machining marks can be confirmed on the carbon steel before the test. On the other hand, as shown in FIG. 2 (b), it can be confirmed that the surface of the carbon steel irradiated with the high-speed solid-liquid jet 16 is uneven because the carbon steel surface is ground by the abrasive. .

In the conventional jet processing apparatus without abrasive material (Japanese Patent Laid-Open No. 10-85634), when the supersonic water jet 15 collides, the vapor bubbles disappear and cavitation is generated, so that the carbon steel surface is generated. , The surface roughness of the carbon steel hardly changed from that before the test.

As described above, according to the present embodiment, since the metal surface of the object to be processed can be ground by the supersonic water jet and the high-speed solid-liquid jet composed of the abrasive, the equipment and the structural material contaminated with radioactivity. (Piping, tanks, steam turbines, etc.) can remove oxide film, which is a major source of pollution.

Therefore, during periodic inspection of equipment and structural materials in the nuclear reactor, in order to reduce the radiation exposure of workers, the radioactive decontamination device according to the present embodiment is used to prevent radioactive contamination. The present invention is applicable to decontamination of used equipment or reduction of metal waste by decontamination of used equipment and structural materials (radioactive metal waste).

Next, a third embodiment of the apparatus for decontaminating radioactive contaminants according to the present invention will be described with reference to FIG. FIG. 3 is a basic configuration diagram of a decontamination apparatus for decontaminating radioactivity by using a buried pipe 17 embedded in a building floor 18 of a nuclear facility as an object to be treated in the present embodiment. This buried piping 17
Are connected to a supply-side connector 24 and a discharge-side connector 25. A supply hose 20 of the compressed air supply 19 is connected to an abrasive supply 22 through an air supply valve 21. The buried pipe 17 and the abrasive supply device 22 are connected by a supply-side connection device 24 via a connection valve 23. An abrasive 31 is filled in the abrasive supply 22.

On the other hand, the outlet side of the buried pipe is connected to the discharge side connector 25.
Is connected to a cyclone separator 27 via an abrasive discharge pipe 26, and the cyclone separator 27 is connected to a filter 29 via a grinding powder discharge pipe 28.

In this state, air is supplied from the compressed air supply device 19 through the supply hose 20 so that the abrasive material is supplied from the abrasive material supply device 22.
31 is supplied to the buried pipe 17. The abrasive 31 flows in the buried pipe 17 in a swirling flow, and the oxide film formed on the inner surface of the buried pipe 17 and the metal base material of the buried pipe 17 are ground.

The abrasive and the grinding powder are sent to a cyclone separator 27 connected to the outlet side of the buried pipe 17. The abrasive separated by the cyclone separator 27 is collected in an abrasive collection tank 30 connected to a lower portion of the cyclone separator 27, and the grinding powder flows into the filter 29 through a grinding powder discharge pipe 28 and is collected by the filter 29. The abrasive recovered in the abrasive recovery tank 30 is returned to the abrasive feeder 22 again,
Reused repeatedly for decontamination.

Next, the operation and effect of this embodiment will be described. When grinding the oxide film and the metal base material formed on the inner surface of the buried pipe 17 by supplying the abrasive material 31 into the buried pipe 17,
The shape of the particles of the abrasive 31 is desirably a crushed shape, a columnar shape, or a square shape, because the shape of the particles in the spherical shape flows so as to slide in the embedded pipe 17. Among these, the crushed shape has a large grinding ability because it is ground at corners.

However, since stress concentrates on the corners,
Partially stabilized zirconia sintered compact particles (Zr
(O ₂ : 95 wt%, Y ₂ O ₃ : 5 wt%), they are easily crushed as compared with spherical particles. The particle shape having a higher grinding ability than spherical particles and less crushable than crushed particles is a columnar or square shape having a small number of corner portions.

Also in this shape, the diameter (φ) and height (h1) of the columnar particles are larger when φ = h1 than the height (L1) and the length (L2) of the rectangular particles. As for (h2), when L1 = L2 = h2, the metal surface of the buried pipe 17 can be ground uniformly. This is because, for example, when φ <h1, the h1 surface of the columnar particles easily comes into contact with the inner surface of the buried pipe 17, so that the columnar particles flow through the inner surface of the buried pipe 17 so as to slide.

Columnar particles having a shape close to a square due to partially stabilized zirconia-based sintered particles that are difficult to be crushed are disclosed in
It can be manufactured by compression molding and extrusion molding by tabletting or roll pressing disclosed in Japanese Patent No. 6352. The square shape can be manufactured by compression molding, roll molding, tape molding, extrusion molding, and casting.

Therefore, the diameter is 0.4 to 0.6 mm and the height is 0.4
A grinding test was carried out using columnar particles of about 0.6 mm as an abrasive, flowing the inner surface of the carbon steel buried pipe at a supply pressure of compressed air of 0.6 MPa, and repeatedly using the abrasive initially charged 100 times. FIGS. 4A and 4B show the results.

FIG. 4 shows the result of measuring the particle size distribution of the grinding powder after separating the abrasive and the grinding powder after the grinding test by a cyclone separator. FIG. 4A shows the particle size distribution of the grinding powder,
FIG. 4B shows the particle size distribution after the grinding powder has been dissolved in a mixed aqueous solution of nitric acid and hydrochloric acid.

The grinding powder before the acid treatment is a mixture of the dust crushed by the abrasive and the grinding powder of carbon steel.
In most cases, it was 70 μm or less. However, if the grinding powder of carbon steel is dissolved in a mixed aqueous solution of nitric acid and hydrochloric acid, only the crushed powder of the abrasive will be produced.
m.

As described above, the spherical partially stabilized zirconia sintered particles, which will be described later, are hardly crushed by repeated use of about 200 times as shown in FIG. 11, but cylindrical particles are crushed. Crushed powder is collected on the filter.

However, the crushing ratio was about 20% of the initial charge even after 100 repeated uses. FIG. 11 shows the relationship between the relative speed depending on the presence or absence of grinding powder and the number of times of repeated use.

According to the present embodiment, the crushed, columnar, and square abrasives are buried in the buried piping 17 by the supply pressure of the compressed air.
And the inner metal base material of the buried pipe 17 can be ground, so that the buried pipe 17 contaminated by radioactivity at the nuclear facility can be decontaminated. In addition, since partially stabilized zirconia-based sintered particles containing zirconium oxide as a main component and yttrium oxide added at 5 wt% are used as an abrasive, the particles are hard to be crushed, and the used waste generated as a secondary waste is used. Abrasive materials can be reduced.

Next, a third embodiment of the apparatus for decontaminating radioactive contaminants according to the present invention will be described with reference to FIG. FIG. 5 is a basic configuration diagram schematically showing a decontamination device for partially decontaminating the concrete floor surface 40 contaminated with radioactivity by partially grinding the building concrete floor surface 40 in the present embodiment. .

The decontamination apparatus for radioactive contaminants according to the present embodiment is mainly composed of a decontamination apparatus main body 32, an abrasive supply / recovery apparatus 33, and a compressed air supply unit 34 as shown in FIG. I have. The decontamination device main body 32 and the abrasive supply / recovery device 33 are connected by an abrasive supply hose 35 and an abrasive recovery hose 36. The abrasive material supply / recovery device 33 and the compressed air supply device 34 are connected by a compressed air supply hose 37.

The decontamination device main body 32, the abrasive supply / recovery device 33, and the compressed air supply device 34 are each provided with wheels 38 and are portable. A blast gun 39 connected to an abrasive supply hose 35 is attached to a lower part of the decontamination apparatus main body 32 toward the concrete floor surface 40. An abrasive recovery pipe 41 connected to an abrasive recovery hose 36 for abrasive recovery is mounted outside the blast gun 39.

A brush 42 for preventing scattering is attached to the tip of the abrasive recovery pipe 41 so as to be in contact with the concrete floor surface 40. Blast gun 39 and abrasive recovery pipe 41 are moving mechanism
The blast gun is held by the moving mechanism 43.
39 and the abrasive recovery pipe 41 are configured to be able to move up, down, left and right.

A rail extends from the front to the lower surface of the decontamination device main body 32.
A radiation detector 45 is installed on the rail 44. The signal from the radiation detector 45 is sent to a measurement unit 46 including a signal processing device, a wave height analyzer, and a data processing device to inform an operator of the radioactivity level of the concrete floor surface 40.

A hand-push handle 47 is attached to the decontamination apparatus main body 32 so that an operator can push it by hand. Abrasive material supply and recovery device 33 consists of abrasive material supply device 48, cyclone separator 4
9, a dust collector 50 including a blower and a filter.

Next, the operation and effect of this embodiment will be described. The blast gun 39 and the abrasive recovery pipe 41 are
Is located above the decontamination device main body 32, and the radiation detector 45
Is located at the lower part of the decontamination apparatus main body 32 down the rail 44.
In this state, the worker holds the hand-push handle 47 and moves to the decontamination apparatus main body 32 to measure the radioactivity level of the concrete floor surface 40.

Since the abrasive supply hose 35 and the abrasive recovery hose 36 can be extended up to 20 m, the decontamination apparatus main body 32 can be moved over a wide range. When the contamination of the concrete floor surface 40 is detected, the radiation detector 45 is moved to the front of the decontamination device main body 32 along the rail 44, and the blast gun 39 and the abrasive recovery pipe 41 are moved downward by the moving mechanism 43. Lower it.

According to the present embodiment, the compressed air supply device 34
The abrasive in the abrasive feeder 48 is sent to the blast gun 39 by the supply pressure from, and the concrete on the concrete floor 40 can be ground. Further, the grinding powder and the abrasive of the concrete are sucked from the collection pipe 41 by the blower of the dust collector 50, the abrasive and the grinding powder are separated by the cyclone separator 49, and the abrasive is returned to the abrasive feeder 48. The grinding powder is reused and collected by the filter of the dust collector 50.

Next, an apparatus for testing abrasives used in the apparatus for decontaminating radioactive contaminants according to the present invention will be described with reference to FIG. FIG. 6 schematically shows a vertical cross section of a test device for confirming the durability of the abrasive used in the first to third embodiments. This test apparatus applies abrasive 13 to a blast gun 53 in a grinding chamber 52 by a supply pressure from a compressed air supply 51.
Alternatively, the specimen 54 was ground by supplying 31. The abrasive and grinding powder in the grinding chamber 52 are guided to the cyclone separator 55 and separated, and the abrasive 13 or 31 is returned to the abrasive feeder 56 for reuse, and the grinding powder is connected to the downstream side of the cyclone separator 55. The collected dust is collected in the filter inside the dust collector 57.

Using the above-described test apparatus, the abrasive 13 or 31
Using a partially stabilized zirconia particle having an average particle diameter of 250 μm, a grinding test was performed on the carbon steel of the test piece 54 at a supply pressure of 0.6 MPa. As a result, the carbon steel grinding speed was only about 70% of the initial grinding speed when the abrasive 13 or 31 was used 50 times.

When the abrasive particles were observed with an optical microscope to investigate the cause, it was observed that carbon steel grinding powder adhered to the surface of the particles in a skin-like manner, and this grinding powder adhered to the abrasive particles. By doing so, it was found that the grinding speed was reduced.

As a method for removing grinding powder, see Japanese Patent Application Laid-Open
As disclosed in JP-A-225835, there is a method of firing an abrasive. Although this method is effective in removing deposits, it has problems such as the necessity of an apparatus for firing and the need to cool the abrasive before reuse.

As described in the second embodiment, there is a method in which grinding powder is dissolved with an aqueous solution of an inorganic acid such as nitric acid or hydrochloric acid. However, when the used aqueous solution of an inorganic acid is discarded, neutralization is performed. Because of the necessity of treatment, there were problems such as an increase in secondary waste. Therefore, an apparatus capable of reliably separating the grinding powder adhering to the abrasive particles with a relatively simple apparatus will be described below.

Next, referring to FIG. 7, a first embodiment of a method for collecting abrasives according to the present invention for separating abrasive powder attached to abrasive particles used for decontamination and recovering the abrasives. Will be described.

In FIG. 7, a pair of rollers 59 are mounted on a fixed base 66 via a bearing 67, and these rollers 59 rotate in opposite directions while being pressed against each other by the force of a spring 58. The decontaminated abrasive 60 used for decontamination is supplied between the mating surfaces of the two rollers 59, and the abrasive 60 after decontamination is compressed and polished by the pressing force of the roller 59.

As a result, the grinding powder adhering to the surface of the abrasive 60 after decontamination is broken, and the grinding powder is separated from the abrasive 60 after decontamination. Abrasive after treatment passed through two rollers 59
A mixed powder 61 of 60 and grinding powder is received by a tray 62 and collected. The mixed powder 61 of the abrasive and the grinding powder received and collected in the tray 62 is returned to, for example, the grinding chamber 52 shown in FIG. 6 and separated by the cyclone separator 55. The abrasive is recovered and reused, and the grinding powder is reused. Is collected in a filter in the dust collector 57.

Next, a second embodiment of the method for collecting abrasives according to the present invention will be described with reference to FIG. Between the facing fixed disk 63 and the rotating disk 64 having an opening cylindrical portion 69 at the center,
The abrasive 60 used for decontamination is supplied from the opening cylindrical portion 69, and the abrasive 60 is polished while being compressed by the pressing force and the rotational force between the disks 63 and 64.

Thus, the grinding powder adhering to the surface of the abrasive 60 is broken, and the powder 61 mixed with the grinding powder is separated from the abrasive 60. The fixed disk 63 has a mixed powder 61 of abrasive and grinding powder.
A large number of uneven grooves 65 are formed so as to be easily discharged, and a mixed powder 61 of the abrasive 60 and the grinding powder is discharged from this portion.

The processed abrasive discharged from the disks 63 and 64
The mixed powder 61 of 60 and the grinding powder is received by a tray 67 and collected.
Mixed powder 61 of abrasive and grinding powder collected in tray 67
Is returned to, for example, the grinding chamber 52 shown in FIG. 6 and separated by the cyclone separator 55, the abrasive is collected and reused, and the grinding powder is collected by the filter in the dust collector 57.

Next, a third embodiment of the method for collecting abrasives according to the present invention will be described with reference to FIG. The abrasive 60 used for decontamination is supplied into a mortar 68, and a pestle 71 connected to a support rod 70 is mechanically rotated to grind the abrasive 60 while compressing the abrasive. As a result, the grinding powder adhering to the surface of the abrasive 60 is broken, and the grinding powder is separated from the abrasive 60. The mixed powder of the abrasive and the grinding powder after the treatment is returned to, for example, the grinding chamber 52 shown in FIG. 6 and separated by the cyclone separator 55, the abrasive is reused, and the grinding powder is collected by the filter in the dust collector 57. I do.

Next, a fourth embodiment of the method for collecting abrasives according to the present invention will be described with reference to FIG. Reference numeral 72 in FIG. 10 denotes a closed container, in which the abrasive 60 used for decontamination is supplied into the closed container 72, and the closed container 72 is fixed to a vibration device 74 via a mounting member 73. The vibrating device 74 is vibrated to separate the abrasives 60 from each other or the abrasive powder adhered to the surface of the abrasive 60 by friction and collision between the abrasive 60 and the inner wall of the closed vessel 72.

The mixed powder of the abrasive and the grinding powder after the treatment is returned to, for example, the grinding chamber 52 shown in FIG. 6 and separated by the cyclone separator 55, the abrasive is reused, and the grinding powder is collected by the dust collector.
Collect in the filter inside 57.

Next, in order to confirm the effects in the first to fourth embodiments of the above-mentioned method for separating abrasives with reference to FIG. 11, the grinding powder adhering to the abrasives is separated, and the apparatus shown in FIG. 6 is used. The results of a carbon steel grinding test performed repeatedly using abrasives will be described.

FIG. 11 also shows, for comparison, the results of a grinding test performed without separating the grinding powder adhering to the abrasive.
The test conditions were as follows: supply pressure: 0.6 MPa, abrasive: average particle size
250 μm spherical partially stabilized zirconia particles were used.

When the grinding powder adhering to the abrasive material in a skin-like manner was separated, the carbon steel was ground at a substantially constant grinding speed up to a repetitive use of 300 times. On the other hand, when the grinding powder was not separated, the grinding speed was reduced to about 70% of the initial grinding speed at the 50th use.

As described above, by separating the grinding powder adhering to the abrasive, it is possible to decontaminate equipment and structural materials contaminated with radioactivity with stable decontamination performance. Moreover, since the grinding powder contains a radioactive substance, recontamination of equipment and structural materials can be suppressed.

Next, FIGS. 12 (a), 12 (b), 13 (a),
The operation and effect of the embodiment of the method for separating abrasives will be described with reference to (b). FIG. 12 (a) shows the particle size distribution of the abrasive used in the test shown in FIG. 11 before the test and the particle size distribution of the abrasive at the 300th repeated use (shown in the figure after the test). Is shown. FIG. 12B shows the particle size distribution of the grinding powder separated by the cyclone separator and collected by the filter.

As apparent from FIG. 12 (a), the particles of the abrasive before the test were distributed in the range of 120 to 370 μm with the peak at 250 μm, and this particle size range was tested even after 300 repeated use. Little change was observed from the previous particle size distribution. Further, as is clear from FIG. 12B, the particle size of the grinding powder is distributed to 100 μm or less.

Thus, when partially stabilized zirconia particles are used as abrasives for blast decontamination of radioactively contaminated equipment and structural materials, the abrasives and the radioactive ground powder can be easily separated by a cyclone separator. Since it can be separated, it is possible to suppress re-contamination of equipment and structural materials.

On the other hand, the test results shown in FIG. 13 show that among the ceramic materials shown in Table 1, zirconium oxide particles (67 wt% ZrO ₂ , 30 wt% S
iO ₂ ). This particle is the AEA Technolo
gy (UK) has applied it to blast-contaminated abrasives (MA Guan, et al .: Wat Abrasive ParticleImp
act as Nuclear Decontamination Technique, SPECTRU
M'90, pp. 269-271, 1990).

The particles before the test, like the partially stabilized zirconia particles, are distributed in the range of 120 to 400 μm with a peak at approximately 250 μm. However, since the abrasive was crushed gradually when repeatedly used, the particle size distribution over a wide range of 20 to 400 μm was exhibited when the abrasive was repeatedly used 30 times. The particle size distribution of the grinding powder was 50 μm or less, and the grinding powder and the crushed particles of the abrasive moved to the filter side.

As described above, zirconium oxide particles (67
(wt% ZrO ₂ , 30wt% SiO ₂ ) was crushed when used for dry blasting abrasives, so used abrasives (secondary waste) used for decontamination of radioactively contaminated equipment and structural materials There is a problem that occurs in large quantities.

When the surface of the ground carbon steel was analyzed for zirconium (Zr), which is the main component of the abrasive, by an electron probe microanalyzer, Zr was detected from the entire surface. This is made of zirconium oxide particles (67 wt% ZrO ₂ ,
It is considered that 30 wt% SiO ₂ ) was crushed and the crushed powder was driven into the carbon steel surface.

Therefore, if these particles are used for decontamination of equipment and structural materials contaminated with radioactivity, the radioactive substance is injected into the metal surface together with the crushed powder, and there is a high possibility that the radioactivity cannot be completely removed.

On the other hand, since the spherical partially stabilized zirconia particles were hardly crushed, the ground carbon steel surface was not detected even when Zr was analyzed by an electron probe microanalyzer. Further, as described in the second embodiment, the crushed, square, and columnar particles are easily crushed as compared with the spherical particles, and there is a concern that crushed powder may enter the metal surface. .

To confirm this, a grinding test of carbon steel was performed using crushed particles, and Zr analysis of the metal surface was performed by an electron probe microanalyzer. As a result, Zr was hardly detected from the metal surface.

This has a great effect on the fracture toughness.
Fracture toughness indicates toughness, and the greater the value of fracture toughness, the more tough. Since the partially stabilized zirconia particles have higher fracture toughness than other ceramics, it is considered that almost no crushed powder was injected into the metal surface.

Therefore, when the partially stabilized zirconia particles are used as an abrasive for blasting, the radioactivity can be reliably decontaminated from equipment and structural materials contaminated with the radioactivity without being affected by the particle shape.

[0096]

According to the present invention, the following effects can be obtained. (1) According to the first aspect of the present invention, a high-speed solid-liquid jet composed of a steam jet, a water jet and an abrasive can grind a metal base material, so that radioactive substances can be reliably obtained from equipment and structural materials contaminated with radioactivity. Can be removed. Further, according to the invention of claim 5, by using partially stabilized zirconia particles as the abrasive, the abrasive is hard to be crushed, so that the amount of used abrasive generated can be greatly reduced.

(2) According to the second aspect of the present invention, the inner surface of a buried pipe buried in a building of a nuclear facility has partially stabilized zirconia in which the shape of particles pumped by air pressure is crushed, square and cylindrical. Since the particles can be ground, radioactive substances can be reliably removed from the inner surface of the pipe contaminated with radioactivity.
In addition, since the partially stabilized zirconia particles are hard to be crushed, the amount of used abrasives can be significantly reduced.

(3) According to the invention of claim 4, since the floor concrete of the building of the nuclear power facility can be ground by the partially stabilized zirconia particles pumped by air pressure, the radioactive material is contaminated from the inner surface of the pipe contaminated with radioactivity. Can be reliably removed. In addition, since the partially stabilized zirconia particles are hard to be crushed, the amount of used abrasives can be significantly reduced.

(4) According to the fifth aspect of the present invention, when partially stabilized zirconia particles are used as the abrasive, the crushed powder is driven into the metal surface even if the particle shape is crushed, square, cylindrical or spherical. Never be. Therefore, according to the invention of claim 3, by using the particles, blast decontamination of used equipment and structural materials (radioactive metal waste) generated at the time of operation of a nuclear facility and at the time of reactor decommissioning, Radioactivity can be reliably removed from radioactive metal waste.

(5) According to claims 6 to 10,
Grinding powder that adheres to the abrasive can be separated or removed by a mechanical compression or breaking method. Therefore, the system configuration of the decontamination apparatus can be simplified, and the object to be decontaminated can be continuously decontaminated with stable decontamination performance and without recontamination.

[Brief description of the drawings]

FIG. 1A is a schematic cross-sectional view showing a first embodiment of a radioactive contaminant decontamination apparatus according to the present invention, and FIG.
FIG.

FIG. 2 (a) is a waveform diagram showing the surface roughness of a carbon steel specimen before the test for explaining the operation and effect of the first embodiment of the present invention, and FIG. 2 (b) is the surface after the test. FIG. 4 is a waveform chart showing roughness.

FIG. 3 is a basic configuration diagram for explaining a second embodiment of the radioactive contaminant decontamination apparatus according to the present invention.

FIG. 4 (a) is a particle size distribution diagram of grinding powder separated by a cyclone separator in the decontamination apparatus in FIG. 3,
(B) is a particle size distribution diagram after the grinding powder is dissolved in an acid.

FIG. 5 is a basic configuration diagram showing a third embodiment of a radioactive contaminant decontamination apparatus according to the present invention in a partial cross section.

FIG. 6 is a schematic cross-sectional view for explaining an abrasive testing device in the radioactive contaminant decontamination device according to the present invention.

FIG. 7 is a perspective view schematically showing a part of the first embodiment of the method for collecting abrasives according to the present invention.

FIG. 8 is a partially cutaway perspective view for explaining a second embodiment of the method for collecting abrasives according to the present invention.

FIG. 9 is a partially schematic perspective view for explaining a third embodiment of the method for collecting abrasives according to the present invention.

FIG. 10 is a side view showing a partial cross section for explaining a fourth embodiment of the method for collecting abrasives according to the present invention.

FIG. 11 is a characteristic diagram showing a grinding speed of carbon steel when an abrasive is repeatedly used in the embodiment of the method for recovering an abrasive according to the present invention.

12A is a particle size distribution diagram of a partially stabilized zirconia abrasive in the embodiment of the method for recovering abrasive material according to the present invention, and FIG. 12B is a particle size distribution diagram of the same grinding powder.

FIG. 13 (a) is a particle size distribution diagram of a zirconium oxide abrasive in the embodiment of the method for collecting abrasives according to the present invention, and FIG. 13 (b) is a particle size distribution diagram of the same grinding powder.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Water nozzle, 1a ... Cylindrical part, 1b ... Taper part, 1c ...
Injection hole, 2 ... mixing nozzle, 2a ... injection port, 3 ... steam nozzle, 3a ... cylindrical part, 3b ... curved part, 3c ... injection hole,
3d: minimum cross section, 4: steam flow, 5: workpiece, 6 ...
Steam supply pipe, 7 ... Steam supply valve, 8 ... Water supply pipe, 9 ... Water supply valve, 10 ... Abrasive supply pipe, 11 ... Abrasive supply, 12 ... Abrasive supply valve, 13 ... Abrasive, 14 ... Water jet, 15… Supersonic water jet, 16… High-speed solid-liquid jet, 17… Buried piping, 18… Building floor, 19
... compressed air supply, 20 ... supply hose, 21 ... air supply valve,
22 ... abrasive supply device, 23 ... connection valve, 24 ... supply side connection device, 25
… Discharge-side connector, 26… Abrasive discharge pipe, 27… Cyclone separator, 28… Abrasive powder discharge pipe, 29… Filter, 30… Abrasive collection tank, 31… Abrasive, 32… Decontamination device body, 33… Abrasive supply and recovery device, 34 ... Compressed air supply, 35 ... Abrasive supply hose, 36 ... Abrasive recovery hose, 37 ... Compressed air supply hose, 38 ... Wheels, 39 ... Blast gun, 40 ... Concrete floor surface, 41 ... Abrasive collection pipe, 42 ... Splash prevention brush, 43 ...
Moving mechanism, 44… Rail, 45… Radiation detector, 46… Measurement unit, 47… Hand push handle, 48… Abrasive material feeder, 49…
Cyclone separator, 50: dust collector, 51: compressed air supply, 52: grinding chamber, 53: blast gun, 54: test specimen, 55
... cyclone separator, 56 ... abrasive supply, 57 ... dust collector, 58 ... spring, 59 ... roller, 60 ... abrasive after decontamination, 61 ... mixed powder, 62 ... tray, 63 ... fixed disk, 64 ... rotating disk , 65 ... Uneven groove, 66 ... Fixed base, 67 ... Bearing, 68 ...
Mortar, 69: open cylinder, 70: support rod, 71: pestle, 72: sealed container, 73: mounting member, 74: vibration device.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masami Toda 1 Tokoba Toshiba-cho, Koyuki-ku, Kawasaki-shi, Kanagawa Pref. No. 1 In the head office of Toshiba Corporation (72) Nao Narabayashi Inventor, 8-8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside of Toshiba Yokohama Office Co., Ltd. No. 1 Toshiba Plant Construction Co., Ltd.

Claims (10)

[Claims] A water nozzle having a cylindrical portion having one end sealed, a tapered portion gradually reduced in diameter at an opening of the other end of the cylindrical portion, and a jet hole at a tip of the tapered portion; and the cylindrical portion of the water nozzle. A steam nozzle that covers the tapered portion from the outer peripheral side of the portion and extends on an extension of the tapered portion and is fitted concentrically to the water nozzle, and is provided at an end of the tapered portion of the steam nozzle. A radioactive contaminant comprising: a mixing nozzle; an abrasive supply pipe connected to a side surface of the mixing nozzle; and an abrasive supply connected to the abrasive supply pipe via a supply valve. Decontamination equipment. 2. An abrasive which is connected to a supply-side connector for supplying compressed air and an abrasive to one of buried pipes buried in a building of a nuclear facility, and decontaminated the inside of the buried pipe to the other of the buried pipes. A discharge-side connector for discharging grinding powder and compressed air is connected, and a cyclone separator for collecting the abrasive used for the decontamination and separating the abrasive into reusable abrasive and grinding powder is connected to the discharge-side connector. A decontamination apparatus for radioactive contaminants, wherein a filter is connected to the side of the cyclone separator where the grinding powder is discharged. 3. A decontamination apparatus main body, an abrasive supply / recovery apparatus connected via a supply hose for supplying an abrasive to the decontamination apparatus main body and a recovery hose for recovering the abrasive after decontamination, It consists of a compressed air supply unit connected to the material supply and recovery unit via a compressed air supply hose, and the blast gun, abrasive collection tube, scattering prevention brush, radiation detector and measurement unit are integrated into the decontamination device body. A decontamination apparatus for radioactive contaminants, wherein the abrasive supply and recovery device is integrated with an abrasive supply, a cyclone separator and a dust collector. 4. The decontamination apparatus main body is provided with a rail for moving the radiation detector from the main body to the building concrete floor surface, and scans the radiation detector along the rail to form the building concrete. The apparatus for decontaminating radioactive contaminants according to claim 3, wherein the apparatus is configured to measure radiation on a floor surface. 5. The abrasive is partially stabilized zirconia-based sintered particles to which zirconium oxide is a main component and yttrium oxide is added, and the particle shape is spherical, cylindrical, square or crushed. 4. The decontamination apparatus for radioactive contaminants according to claim 1, wherein: 6. Two rollers are provided in parallel and arranged in parallel so that they rotate in opposite directions while being pressed against each other by a spring force, and the abrasive used for decontamination is supplied between the mating surfaces of the two rollers. Recovering the abrasive by compressing and polishing the abrasive with the pressing force of the roller to separate abrasive powder adhering to the abrasive and recovering the abrasive. 7. An abrasive used for decontamination is supplied between a stationary disk facing the rotating disk and a rotating disk having an opening in the center.
A method for collecting abrasives, comprising compressing and polishing the abrasives with the pressing force and rotational force of the disks to separate abrasive powder attached to the abrasives and recovering the abrasives. 8. An abrasive used for decontamination is supplied into a mortar, and a pestle is mechanically rotated to compress and polish the abrasive, thereby separating grinding powder adhering to the abrasive. A method for collecting abrasives, comprising recovering abrasives. 9. An abrasive used for decontamination is supplied to a closed container, and the closed container is vibrated to adhere to the abrasive by friction and collision between the abrasives or between the abrasive and the inner wall of the closed container. A method for collecting abrasives, comprising separating abrasive powder and collecting abrasives. 10. The abrasive used for decontamination is sent to a cyclone separator to separate grinding powder adhering to the abrasive, and the abrasive is recovered. The recovered abrasive is reused for decontamination. And recovering the abrasive powder with a filter connected to the abrasive powder discharge side of the cyclone separator.