JP3015713B2 - Method and apparatus for decontamination treatment of metal waste - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for decontaminating metal waste contaminated with radioactive substances generated during the operation, periodic inspection and decommissioning of nuclear facilities.

[0002]

2. Description of the Related Art For example, as a decontamination treatment technique for metal waste contaminated with radioactive substances, there are (1) a sand blast method in which sand is sprayed onto a metal waste at a high pressure from a nozzle,
There are known (2) an ice blast method of spraying ice particles to decontaminate, and (3) an ice blast method of spraying dry ice particles to decontaminate. These decontamination techniques are effective in removing oxide films, paints, oils, etc. loosely attached to metal waste.

However, since the decontamination methods (2) and (3) hardly grind the metal base material, the removal of radioactive contamination that has entered a part of the oxide film, paint and metal base material that has firmly adhered is removed. This technique is not suitable for In the decontamination method (1), sand is inexpensive but difficult to reuse, so there is a problem that a large amount of secondary waste is generated.

Further, as a method of grinding and decontaminating a part of a metal base material, a decontamination technique using a ceramic material as a blast material is known. For example, when aluminum oxide particles are sprayed onto the surface of a metal waste to decontaminate, a part of the metal base material is ground so that an oxide film or paint that is firmly attached can be effectively removed.
However, aluminum oxide particles have a wide particle size range and are liable to be crushed, and thus have a problem that a large amount of secondary waste is generated.

[0005] To solve these problems, AEA Techno
A blast decontamination method using zirconium oxide particles to which silicon oxide is added as a blast material has been performed by logy (UK). (MA Gugan, et al .: Wat Abrasive Parti
cle Impact as A Nuclear Decontamination Technique,
SPECTRUM '90, pp.269-271, 1990)

[0006]

This blast material has spherical particles, and although the grinding speed of the metal base material is lower than that of aluminum oxide, it is hard to be crushed. Therefore, there is an advantage that the blast material can be repeatedly reused as a blast material. .

However, since the blast material has a wide range of particle size, when particles having a predetermined particle size or less are separated and reused, the blast material having a small particle size is used in addition to the grinding powder. Is a secondary waste, and when repeatedly reused for a long period of time, it is gradually crushed and powdered, so that there is a problem that the crushed powder becomes a secondary waste.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the use of a hard-to-crush ceramic material applicable as a blast material can reduce the amount of secondary waste generated due to decontamination, and An object of the present invention is to provide a method and apparatus for decontaminating radioactive metal waste that can prevent cross-contamination of metal waste.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a decontamination treatment method in which a blast material is sprayed onto a treated surface of a metal waste to perform a blast treatment, wherein the blast material comprises zirconium oxide and yttrium oxide added to yttrium oxide. Particles, and the addition amount of the yttrium oxide is 6
% By weight (but not including 0). The blast material has a spherical shape close to a true sphere, and has a particle diameter of more than 50 μm.

[0010] The apparatus for decontaminating metal waste using the blast material is provided so as to face a decontamination tank having a hopper connected to a lower portion thereof and a metal waste treatment surface disposed in the decontamination tank. Injection nozzle, a blast material supply device connected to the injection nozzle via a compressed air supply line, a circulation line connected to the injection nozzle, and connected between the circulation line and the hopper. A circulation pump, a grinding powder separation device installed via a supply pump and a supply line connected to the hopper, a separation tank connected to the grinding powder separation device via a separation line, and the grinding powder separation device. And a collection line connecting the decontamination tank.

The angle between the spray nozzle and the metal surface of the metal surface treatment apparatus is 60 to 90 °, and the distance between the spray nozzle and the metal surface is
It is characterized in that it is held at 100 mm or less. Further, the grinding powder separating apparatus is characterized by comprising a liquid cyclone separator capable of separating particles having a particle size of 50 μm or less and particles having a particle size of more than 50 μm.

A method of treating a used blast material is characterized in that particles of 50 μm or less separated by the above-mentioned grinding powder separation device are solidified with cement. Among the particles having a particle diameter of 50 μm or less, a metal base material grinding powder is dissolved with an inorganic acid, neutralized and solidified with cement, and the inorganic acid is a sulfuric acid or nitric acid solution. The method is characterized in that the particles having a size of 50 μm or less and the used blast material are mixed and solidified with cement.

[0013]

The zirconium oxide particles are less likely to be crushed than the ceramic particles obtained by adding silicon oxide to aluminum oxide or zirconium oxide, so that stable decontamination performance can be obtained even when reused repeatedly. In particular, zirconium oxide spherical particles obtained by adding yttrium oxide to zirconium oxide at a weight ratio of 6% or less, preferably about 5%, have excellent wear resistance.

Further, by narrowing the particle size distribution width of the blast material, the grinding powder and the used blast material can be easily separated. Therefore, the radioactive material contained in the grinding powder and the blast material can be easily separated, preventing cross-contamination (cross-contamination) when the blast material is reused repeatedly and generating secondary waste due to decontamination processing operations. The amount can be reduced.

Further, in the decontamination treatment apparatus, the angle between the injection nozzle and the metal waste processing surface is maintained at 60 to 90 °, and the distance between the injection nozzle and the metal surface is maintained at 100 mm or less, whereby the metal grinding speed is increased. Therefore, when decontamination of metal waste is performed under these conditions, radioactivity can be removed in a short time, and decontamination work efficiency is improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a method and an apparatus for decontaminating metal waste according to the present invention will be described with reference to FIG. FIG.
Corresponds to claim 1 of the present invention and claims 9 to 13
FIG. 2 is a configuration diagram for describing a decontamination processing method by a blast method and a decontamination processing apparatus for describing an example of the present invention.
That is, in FIG. 1, reference numeral 1 denotes a metal surface treatment device for metal waste, and the metal surface treatment device 1 includes a decontamination tank 2,
An injection nozzle 3 provided in the decontamination tank 2 and a decontamination tank 2
And a hopper 4 and the like connected to the lower part. In the decontamination tank 2, a metal waste 5 is movably arranged on a gantry, and a lower part of the decontamination tank 2 and an upper part of the hopper 4 communicate with each other.

In the drawing, reference numeral 6 denotes a blast material supply device. The blast material supply device 6 includes a circulation pump 8 for supplying a mixture 7 of blast material and water in the hopper 4 to the injection nozzle 3 and a circulation of the mixture. The line 9, the compressor 10 for supplying high-pressure air to the injection nozzle 3, and the blast material are spherical ceramics obtained by adding yttrium oxide to zirconium oxide. It is composed of a high-pressure air supply line 11.

In the drawing, reference numeral 12 denotes a grinding powder separating device,
It separates fine powder such as grinding powder during or after decontamination processing. The grinding powder separation device 12 includes a supply pump 13 connected to the hopper 4 and a supply line 14 connected to the supply pump 13.
, A separation line 17 for supplying fine powder such as grinding powder connected to the upper part of the liquid cyclone separator 15 to the separation tank 16, and a grinding powder connected to the lower part of the hydrocyclone separator 15. Collection line for returning blast material after separation of fine powder such as to hopper 4
It consists of 18 and.

Next, the operation of the first embodiment will be described. The metal waste 5 is set in the decontamination tank 2 and the injection nozzle 3
, A mixed liquid 7 of blast material and water in the hopper 4 is supplied by a circulation pump 8 through a circulation line 9. At the same time, the compressor 10 supplies high-pressure air to the injection nozzle 3 through the supply compressed air line 11.

When the mixed solution 7 is sprayed and sprayed on the processing surface of the metal waste 5, a part of the metal base material of the metal waste 5 is ground and adheres to the processing surface of the metal waste 5. The remaining oxide film or paint is removed. The injected liquid mixture 7 is collected in the hopper 4 and repeatedly reused through the circulation line 9.

On the other hand, the ground powder such as metal base material powder, oxide film or paint in the hopper 4 is supplied to a supply pump.
The powder 13 is supplied to the cyclone separator 15 through the supply line 14 together with the mixed liquid 7 of the blast material, and the grinding powder is collected in the separation tank 16 through the separation line 17. The used blast material is returned to the hopper 4 through the collection line 18 and is repeatedly reused in the decontamination processing of the metal waste 5.

Next, a second embodiment according to the third and tenth aspects of the present invention will be described with reference to FIG. FIG. 2 shows the results of measuring the metal grinding speed of various types of blast materials using the metal waste decontamination treatment apparatus shown in FIG. 1. The three types of blast materials shown in Table 1 were ground as metal waste. The test was performed on carbon steel.

[0023]

[Table 1]

The test conditions were as follows: the supply pressure from the compressor 10 was 0.4 MPa, and the distance between the injection nozzle 3 and the metal waste 5 was 80 m.
m, the angle between the injection nozzle and the metal waste 5 was 45 ° for aluminum oxide, and 90 ° for zirconium oxide.

As can be seen from the results of this test, Test No. 1
Aluminum oxide is spherical because of the shape of the particles,
Although the initial grinding speed was several times higher than that of zirconium oxide, repeated use resulted in crushing of the aluminum oxide particles and a sharp decrease in the grinding speed. Test No. Since zirconium oxides 2 and 3 have a spherical particle shape,
Although the grinding speed was small, it was hard to be crushed, so that the grinding speed was hardly reduced even after repeated reuse.

From the above, it has been found that zirconium oxide is harder to be crushed than aluminum oxide, so that a constant grinding speed can be obtained even if it is reused repeatedly.
Therefore, when zirconium oxide particles are used for the blast material, stable decontamination performance can be obtained.

Next, a third embodiment of the present invention will be described.
An example will be described. Test No. used in the second embodiment. 2
Zirconium oxide is a blast material applied by AEA Technology (UK) for blast decontamination. Test No. The zirconium oxide No. 3 is a blast material applied to the method and apparatus for decontaminating metal waste of the present invention. The grinding speed is almost the same for both blast materials, and a substantially constant grinding speed appears even when reused repeatedly.

The blast material after use was observed with a scanning electron microscope. With respect to zirconium oxide of No. 3, almost no change was observed in the particle shape. In the zirconium oxide of No. 2, crushing was observed in some particles.

Since a large amount of metal waste is generated at the time of reactor decommissioning, when blasting such metal waste, it is difficult to crush the blast material that can be repeatedly reused for a long time from the viewpoint of reducing secondary waste. is necessary.

Therefore, in order to evaluate the difficulty of crushing when the spherical zirconium oxide particles are repeatedly reused as a blast material, a compressive breaking strength was measured using a table type precision universal testing machine (model: AGS-D) manufactured by Shimadzu Corporation. Was measured.
The measurement results are shown below. The test No. shown in Table 2 was used. 4 is the test No. Similar to 3, zirconium oxide particles containing zirconium oxide as a main component and 5% yttrium oxide added thereto, but are manufactured by different manufacturers.

[0031]

[Table 2]

Test No. The zirconium oxide particles to which 30% of silicon oxide 2 was added were destroyed at 5.8N. Meanwhile, the test
No. 3 and Test No. The zirconium oxide particles to which about 5% of yttrium oxide 4 was added were destroyed at around 12N.
From this measurement result, it was found that the zirconium oxide particles to which yttrium oxide was added had a higher compressive fracture strength than the zirconium oxide particles to which silicon oxide was added.

As described above, zirconium oxide particles to which yttrium oxide has been added have a high compressive breaking strength. Therefore, when applied to a blasting material for blasting metal waste, it is stable even when repeatedly used for a long time. The decontamination performance is improved, and the amount of secondary waste generated can be reduced because it is hardly crushed.

Next, a fourth embodiment according to claims 10 and 11 of the present invention will be described. When blasting the surface of metal waste, the grinding force of the metal base material is expressed by the following equation.

F = W · / t · g K = F · s = W · v ² / 2g where F: collision force (N) K: work (J) W: blast material weight (kg) v: Velocity at the time of collision of blast material (m / sec) t: Collision time (sec) s: Displacement (m) g: Gravitational acceleration (9.8 m / sec ² )

Since the impact force of each blast material increases as the impact time is reduced, a hard blast material having a high repulsion force is selected. Power increases. In addition, since the work amount is proportional to the square of the injection speed of the blast material, it increases when the injection pressure is high and the distance between the injection nozzle and the metal surface is short.

In the fourth embodiment, the effect of the above equation was confirmed for a case where zirconium oxide particles to which yttrium oxide was added were used as a blast material, and a condition range usable for decontamination treatment of metal waste was determined. Things. A fourth embodiment is shown in FIGS. FIG. 3 shows the test results of the effect of the distance between the injection nozzle 3 and the metal waste 5 on the grinding speed of the metal waste 5 using the blasting apparatus of FIG. 3 shows the results of an effect test of the angle between the metal waste 3 and the metal waste 5. The test conditions are shown in Table 1 above.
Test No. shown in Using zirconium oxide particles of No. 3 under the following conditions.

[0038]

[Table 3]

In the effect test of the distance of the injection nozzle shown in FIG. 3, the metal base material was ground at a substantially constant grinding speed up to 80 mm, and the grinding speed gradually decreased when the grinding speed was higher than 80 mm. From this, when metal waste is blasted using zirconium oxide particles as a blast material, radioactivity can be removed in a short time if the distance between the injection nozzle and the metal waste is kept at 80 mm or less.

In the effect test of the angle of the injection nozzle shown in FIG. 4, the grinding speed gradually increased up to 60 °, and a substantially constant grinding speed was obtained from 60 to 90 °. From this, when blasting metal waste using zirconium oxide particles as a blast material, radioactivity can be removed in a short time if the angle of the injection nozzle is maintained at 60 to 90 °.

The grinding speed of the metal base material increases as the supply pressure increases, but it is easy to handle to remove the oxide film on the surface of the metal base material and the contamination that has entered a part of the metal base material. Therefore, a pressure (less than 1 MPa) easily obtained with an inexpensive compressor is sufficient.

Next, a fifth embodiment corresponding to claims 4 to 6 of the present invention will be described with reference to FIGS. Fifth
In Example 1, the particle size distribution of the grinding powder after blasting stainless steel using zirconium oxide particles to which yttrium oxide was added as a blast material was measured. By performing this measurement, the separation performance of the grinding powder separation device 12 for separating the blast material and the grinding powder shown in FIG. 1 can be determined.

FIG. 5 shows the results of the test No. shown in Table 1. 3 shows the particle size distribution of zirconium oxide particles to which yttrium oxide 3 was added before the test. The particle size of the zirconium oxide particles before the test is distributed in a range of approximately 60 to 150 μm.

FIG. 6 shows the particle size distribution after the test (after the blast treatment), and the number of particles having a particle size of 50 μm or less was increased as compared with that before the test. FIG. 7 shows that the particles of 50 μm or less increased after the test,
In order to confirm that it is grinding powder of stainless steel base material,
The particle size distribution after the zirconium oxide particles are put in sulfur and the grinding powder is dissolved is shown.

As can be seen from the measurement results, particles having a particle size of 50 μm or less were dissolved after dissolution in sulfuric acid, and showed the same tendency as the particle size distribution before the test. Since zirconium oxide has acid resistance, the dissolved particles of 50 μm or less are ground powder of a stainless steel base material.

Next, a sixth embodiment of the present invention will be described with reference to FIGS. The liquid cyclone separator 15 shown in FIG. 1 has a performance capable of separating particles of 50 μm or less and particles of more than 50 μm based on the fifth embodiment.
The particles passing through the recovery line 18 connected to the lower part of the hydrocyclone separator 15 are returned to the hopper 4 and reused repeatedly, and the particles having a particle size of 50 μm or less pass through the separation line 17 connected to the upper part of the hydrocyclone separator 15. pass.

FIG. 8 shows the result of measuring the particle size distribution of the particles collected from the separation line 17 of FIG. As can be seen from the measurement results, the particles passing through the separation line 17 are 50 μm
Only the following were measured, and particles exceeding 50 μm were not measured.

According to the above fifth and sixth embodiments, the grinding powder separating apparatus 12 for separating the blast material and the grinding powder shown in FIG. 1 has a performance capable of separating particles of 50 μm or less and particles of more than 50 μm. By having the above, the radioactivity removed from the metal waste can be separated into the separation tank 16, so that mutual contamination of the metal waste when the blast material is reused repeatedly can be prevented.

Further, compared to aluminum oxide particles or zirconium oxide particles to which silicon oxide is added, it is hard to be crushed. Therefore, when reused for a long period of time, only the grinding powder becomes waste, which is accompanied by decontamination treatment. The amount of secondary waste generated can be reduced.

Next, a seventh embodiment of the present invention corresponding to claims 6 to 8 and 12 will be described with reference to FIG. In the seventh embodiment, the performance of the grinding powder separation device 12 shown in the first embodiment (FIG. 1) is enhanced to prevent cross-contamination of metal waste when the blast material is repeatedly reused. It is. That is, the seventh embodiment differs from the first embodiment in that a collection tank 19 is provided, and the collection line 18 for the liquid cyclone separator 15 is connected to the decontamination tank 2 without being connected to the collection tank.
19, the circulation pump 8 is connected to the collection liquid storage section 20 of the collection tank 19, and the circulation pump 8 is connected to the circulation line 9,
The circulation line 9 is connected to the injection nozzle 3.

In this embodiment, the liquid mixture 7 in the hopper 4 is introduced into the liquid cyclone separator 15 via the supply line 14 by the supply pump 13. Particles exceeding 50 μm in the mixed liquid 7 separated by the hydrocyclone separator 15 are collected as a collecting liquid in a collecting liquid storage section 20 of a collecting tank 19 through a collecting line 18. On the other hand, particles having a size of 50 μm or less are introduced into a separation tank 16 via a separation line 17.

On the other hand, the recovery liquid containing particles exceeding 50 μm in the recovery liquid storage section 20 is injected from the injection nozzle 3 via the circulation line 9 by the circulation pump 8, and is repeatedly reused as a blast material.

As described above, in the present embodiment, the addition of the collection tank 19 to the grinding powder separation device 12 shown in FIG. 1 causes 50 μm which causes cross-contamination (cross contamination).
Grinding powder (metal base material, oxide film, etc.) of m or less can be almost separated from the blast material to be reused. Therefore,
Even when the blast material is repeatedly reused for a long period of time, contamination of the blast material itself or cross contamination of metal waste can be prevented.

Next, when disposing of used zirconium oxide particles or grinding powder generated after the end of decontamination, zirconium oxide itself is the same ceramic material as aluminum oxide which is a cement material, so that it is mixed with grinding powder. It is possible to easily solidify the cement.

Further, since the grinding powder is metal (mainly Fe) particles, if it is solidified and cemented in this state, it may react with groundwater at the disposal site to generate hydrogen gas. . In order to prevent this, the grinding powder can be easily dissolved with sulfuric acid as shown in the fifth embodiment, so that it is also possible to neutralize with caustic soda and solidify the cement.

Therefore, when metal waste is blasted in a nuclear power plant, sulfuric acid used in the nuclear power plant is used. However, when metal waste is blasted in a reprocessing plant, Nitric acid used in the facility can be used to dissolve the grinding powder.

The present invention, in addition to the above-described embodiments, is characterized in that the zirconium oxide particles added with yttrium oxide used in the present invention are not easily crushed even when repeatedly reused as a blast material for a long period of time. The reason for the excellent separation of particles is that the sphericity (maximum diameter / minimum diameter) of the particles is 1.03.
One factor is the fact that the shape is close to a true sphere of about 1.05.

The zirconium oxide particles have an average particle size
Since the particles are manufactured in the range of 62 to 310 μm, and the sphericity of these particles is within the above range, similar performance can be obtained even when these particles are used as a blast material.

[0059]

According to the present invention, the following effects can be obtained. (1) By using spherical ceramic particles obtained by adding yttrium oxide to zirconium oxide as a blast material, it is difficult to be crushed as compared with conventional aluminum oxide particles or zirconium oxide particles added with silicon oxide. Stable decontamination performance can be obtained even when reused.

(2) The angle between the injection nozzle and the metal surface is 60 to 90
° The distance between the injection nozzle and the metal surface is 100 mm or less, and the grinding speed of the metal base material is high, so that radioactivity can be removed from metal waste in a short time.

(3) Since most of the grinding powder has a particle diameter of 50 μm or less, the separation device for separating the blast material and the grinding powder has a performance capable of separating particles of 50 μm or less and particles of more than 50 μm. In addition, the radioactivity removed from the metal waste can be easily separated from the blast material. Therefore, when the blast material is repeatedly reused, contamination of the blast material itself and cross-contamination of metal waste can be prevented.

(4) Due to the effects of the above items (1) and (3), during the decontamination treatment, only the oxide film on the surface of the metal waste or the metal base material is generated as secondary waste. The amount of secondary waste generated can be reduced as compared with zirconium oxide particles to which aluminum oxide or silicon oxide is added.

(5) The used zirconium oxide particles generated after the completion of decontamination can be easily solidified with cement and disposed of in a stable state because the particles themselves are the same ceramic material as aluminum oxide as a cement material. Is possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a metal waste decontamination treatment apparatus for explaining a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the grinding speed of carbon steel and the average number of times of use of various blast materials for explaining a second embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a distance between an injection nozzle and a surface of a metal waste on the grinding speed of carbon steel for explaining a fourth embodiment of the present invention.

FIG. 4 is a characteristic diagram showing a relationship between an injection nozzle and an angle of a metal waste surface on a grinding speed of carbon steel for explaining a fourth embodiment of the present invention.

FIG. 5 is a particle size distribution diagram showing a pre-test particle size of zirconium oxide particles to which yttrium oxide is added for explaining a fifth embodiment of the present invention.

FIG. 6 is a particle size distribution diagram showing the post-test particle size of zirconium oxide particles to which yttrium oxide is added for explaining a fifth embodiment of the present invention.

FIG. 7 is a particle size distribution diagram showing the particle size after dissolving zirconium oxide particles to which yttrium oxide has been added in an acid to explain a fifth embodiment of the present invention.

FIG. 8 is a particle size distribution diagram showing a particle size of a metal base material ground powder separated by a liquid cyclone separator for explaining a sixth embodiment of the present invention.

FIG. 9 is a configuration diagram showing a metal waste decontamination treatment apparatus for explaining a seventh embodiment according to the present invention.

[Explanation of symbols]

1: Metal surface treatment device, 2: decontamination tank, 3: injection nozzle,
4 hopper, 5 metal waste, 6 blast material supply device, 7 mixed liquid, 8 circulation pump, 9 circulation line, 10
... Compressor, 11 ... Compressed air supply line, 12 ... Abrasive powder separator, 13 ... Supply pump, 14 ... Supply line, 15 ... Liquid cyclone separator, 16 ... Separation tank, 17 ... Separation line,
18 ... collection line, 19 ... collection tank, 20 ... collection liquid storage part.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Kanezaki 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Toshiba Corporation Yokohama Office (72) Inventor Minoru Hiraki 3-7-1 Nishishinbashi, Minato-ku, Tokyo Toshiba (56) References JP-A-5-188198 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G21F 9/28

Claims (13)

(57) [Claims] 1. A decontamination treatment method in which a blast material is sprayed on a treated surface of a metal waste, wherein spherical ceramic particles obtained by adding yttrium oxide to zirconium oxide are used as the blast material. Waste decontamination method. 2. The addition amount of the yttrium oxide to the zirconium oxide is not more than 6% by weight (however, 0% or less).
2. The method for decontamination treatment of metal waste according to claim 1, wherein: 3. The method for decontaminating metal waste according to claim 1, wherein the blast material is formed in a spherical shape close to a true sphere. 4. The method according to claim 1, wherein the blast material has a particle size exceeding 50 μm. 5. The method according to claim 1, wherein ceramic particles having a size of more than 50 μm separated from the used blast material after the blasting treatment are reused, and particles having a size of 50 μm or less are solidified with cement. Dyeing treatment method. 6. The decontamination of metal waste according to claim 1, wherein the metal base material ground powder contained in the particles having a size of 50 μm or less is dissolved with an inorganic acid, neutralized, and then solidified with cement. Processing method. 7. The method for decontaminating metal waste according to claim 1, wherein the particles having a size of 50 μm or less and the used blast material are mixed and solidified with cement. 8. The method according to claim 1, wherein the inorganic acid is a sulfuric acid or nitric acid solution. 9. A decontamination tank having a lower portion connected to a hopper, an injection nozzle provided in the decontamination tank so as to face a processing surface of metal waste, and a compressed air supply line connected to the injection nozzle. Blast material supply device connected via a circulating line, a circulation line connected to the injection nozzle, a circulation pump connected between the circulation line and the hopper, a supply pump and a supply line connected to the hopper And a separation tank connected to the grinding powder separation device via a separation line, and a collection line connecting the grinding powder separation device and the decontamination tank. An apparatus for decontaminating metal waste. 10. The metal waste decontamination treatment apparatus according to claim 9, wherein the angle between the spray nozzle and the metal waste treatment surface is maintained at 60 to 90 °. 11. The distance between the injection nozzle and the metal surface is set to 1
The metal waste decontamination treatment apparatus according to claim 9, wherein the apparatus is held at 00 mm or less. 12. The decontamination of metal waste according to claim 9, wherein said grinding powder separation device comprises a liquid cyclone separator capable of separating particles having a particle size of 50 μm or less and particles having a particle size exceeding 50 μm. Processing equipment. 13. A collection line is connected to the grinding powder separation device, a collection tank having a collection liquid storage section is connected to the collection line, and a circulation pump is connected to the collection liquid storage section.
The metal waste decontamination treatment apparatus according to claim 9, wherein a circulation line is connected to a discharge port of the circulation pump, and the circulation line is connected to the injection nozzle.