Radioactive contaminated metal decontamination system and method

Abstract

A radioactive contaminated metal decontamination system and method relate to the technical field of radioactive contaminated metal processing. The radioactive contaminated metal decontamination system includes a metal feeding device, a metal decontamination device, an abrasive purification device and a positive and negative pressure air source; the metal decontamination device includes a shell, a C-shaped conveyor belt assembly, a drum assembly, a nozzle, a clean material bin A and a dirty material bin A; the dust collection device includes a debris collection chamber, a dust buffer chamber, a dust hood A, and a dust hood B; the positive and negative pressure air source includes a positive pressure air supply device and a negative pressure dust collector. A radioactive contaminated metal decontamination method is based on the radioactive contaminated metal decontamination system, and the method is as follows: pretreatment and feeding; metal decontamination. The present invention uses abrasives to strike the metal surface at high speed, effectively stripping off stains, rust and oxide scale containing radioactive nuclides, achieving the effect of radioactive decontamination. By performing surface radioactive decontamination treatment on the abrasive, the recycling of abrasives in the radioactive contaminated metal decontamination process is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of radioactive contaminated metal treatment, in particular to a radioactive contaminated metal decontamination system and method. Background Art

[0002] With the rapid development of the nuclear industry, the amount of nuclear waste metal generated by nuclear power plants and nuclear enterprises has been increasing year by year. This waste metal is highly radioactive, with a half-life of thousands, tens of thousands, or even hundreds of thousands of years. If improperly disposed of, it can seriously pollute the environment. Currently, waste metal with radiation doses exceeding safety thresholds cannot be treated and can only be sealed in metal cans and permanently buried deep within the ground to ensure that it can be geologically sealed for tens or even hundreds of thousands of years without leakage.

[0003] Existing deep burial disposal solutions have the following shortcomings: 1. To ensure that radioactivity is prevented from leaking for tens of thousands of years, the metal canisters are designed to be extremely thick, requiring a significant amount of material to manufacture. Furthermore, as the output of nuclear scrap metal increases annually, the demand for metal canisters is also increasing. Furthermore, deep burial sites are extremely limited and difficult to find, requiring stable geological conditions, tens of thousands of years of earthquake-free conditions, and the presence of intact, unfractured granite. 2. After containing nuclear scrap metal, the canisters become contaminated with radioactivity, generating a certain amount of radioactivity themselves and making them unusable for other purposes. This effectively introduces new radioactive waste into the disposal process, resulting in waste volume expansion.

[0004] The International Atomic Energy Agency first proposed the concept of "radioactive waste minimization" in its 1992 technical document, "Minimization and Separation of Radioactive Waste." This "radioactive waste minimization" aims to reduce the quantity and activity of radioactive waste to reasonably achievable levels. This can be achieved by limiting the generation and spread of radioactive contamination and reducing the volume of nuclear waste storage, thereby minimizing the adverse environmental impacts of nuclear waste and lowering the cost of nuclear waste disposal. Clearly, the current deep burial disposal solution for radioactively contaminated metals cannot meet this "radioactive waste minimization" requirement. Furthermore, as the production of radioactively contaminated metals continues to increase, this contradiction becomes increasingly prominent. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a radioactive contaminated metal decontamination system and method, which is used for the decontamination of radioactive contaminated metals, provides a prerequisite for the reuse of radioactive contaminated metals, and solves the problem that the current disposal solutions for radioactive contaminated metals cannot meet the requirements of "radioactive waste minimization".

[0006] The technical solution of the present invention is: a radioactive contaminated metal decontamination system, comprising a metal feeding device, a metal decontamination device, an abrasive purification device and positive and negative pressure air sources;

[0007] The metal feeding device includes a metal feeding hopper, a vibrating spreader and a plate chain conveyor which are connected in sequence; an upper port for feeding metal fragments is provided at the upper end of the metal hopper, and a lower port for discharging metal fragments is provided at the lower end of the metal feeding hopper; a valve A for controlling the discharge of metal fragments is provided at the lower port of the metal feeding hopper; one end of the vibrating spreader is a high end and the other end is a low end, and the high end of the vibrating spreader is located directly below the lower end of the metal feeding hopper; one end of the plate chain conveyor is a feeding end and the other end is a discharging end, and the feeding end of the plate chain conveyor is arranged closely to the low end of the vibrating spreader;

[0008] The metal decontamination device includes an outer shell, a C-shaped conveyor belt assembly, a rotating drum assembly, a nozzle, a clean material bin A and a dirty material bin A; an inner cavity for decontaminating metal fragments is provided inside the outer shell, and a material inlet connected to the inner cavity is provided on one side of the outer shell, and the material inlet of the outer shell is arranged adjacent to the discharge end of the plate chain conveyor; the C-shaped conveyor belt assembly includes an upper turntable, a lower turntable and a conveyor belt, the upper turntable is located obliquely above the lower turntable, the conveyor belt is wound between the upper turntable and the lower turntable and is arranged in a C shape as a whole, so that outer arc area and inner arc area are formed on both sides of the conveyor belt respectively, and abrasive passage holes for abrasive to pass through are provided on the conveyor belt, and the conveyor belt divides the inner cavity of the outer shell from top to bottom into a metal decontamination sub-chamber and an abrasive collecting sub-chamber, the metal decontamination sub-chamber and the abrasive collecting sub-chamber are connected through the abrasive passage holes, the metal decontamination sub-chamber is connected with the material inlet of the outer shell, the metal decontamination sub-chamber is located in the inner arc area of the conveyor belt, and the abrasive collecting sub-chamber is located in the inner arc area of the conveyor belt. Outer arc area; the drum assembly includes a horizontally arranged drum and a motor for driving the drum to rotate, the drum is located in the inner arc area of the conveyor belt, and an arc-shaped gap is formed between the outer cylindrical surface of the drum and the upper surface of the conveyor belt; the nozzle is vertically arranged at the upper end of the metal decontamination sub-chamber of the shell, the upper port thereof is used to receive the pressurized airflow, and the lower port thereof is used to spray out the abrasive and the pressurized airflow, and a confluence port for receiving the abrasive is provided in the middle thereof; a clean abrasive inlet A and a clean abrasive discharge port A are provided on the clean material bin A; the clean abrasive discharge port A of the clean material bin A is connected with the confluence port of the nozzle through a pipe, and a valve A for controlling the discharge of the abrasive is provided on the clean abrasive discharge port A of the clean material bin A; a dirty abrasive inlet A and a dirty abrasive discharge port A are respectively provided at the top and lower end of the dirty material bin A, and a valve B for controlling the discharge of the abrasive is provided on the dirty abrasive discharge port A of the dirty material bin A, and the dirty material bin A is installed in the abrasive collecting sub-chamber of the shell, and the dirty abrasive inlet A thereon is located directly below the conveyor belt;

[0009] The abrasive purification device includes a feeding device, a discharging device, a steel ball cleaning chamber, a dry ice cleaning machine and a dust collecting device; the feeding device is provided with a feeding port A at the upper end, a discharging port A at the lower end, and a dust outlet A at the lower part of the outer wall between the feeding port A and the discharging port A; the discharging device is provided with a feeding port B at the upper end, a discharging port B at the lower end, and a water vapor outlet hole at the upper part of the outer wall between the feeding port B and the discharging port B; the steel ball cleaning chamber is provided with an inner cavity, and the outside of the steel ball cleaning chamber is provided with a dry ice inlet, an abrasive inlet, a dust collecting device and a dust collecting device in order from top to bottom. The abrasive outlet is connected to the discharge port A of the feeding device, and the abrasive outlet is connected to the feed port B of the discharging device. The abrasive outlet is provided with a valve X for controlling the discharge of the abrasive. The dry ice cleaning machine includes a main body and a spray gun that are interconnected. The spray gun is connected to the dry ice inlet of the steel ball cleaning chamber to spray dry ice particles into the inner cavity of the steel ball cleaning chamber. The dust collection device includes a debris collection chamber, a dust buffer chamber, a dust collection cover A, a dust collection cover B, a collection pipe A, a collection pipe B, a collection pipe C and a collection pipe D. The upper end of the debris collection chamber is provided with a debris collection pipe. The dust buffer chamber is provided with a dust inlet and a negative pressure interface from top to bottom, and a valve Y for controlling the on-off of the air path is provided on the negative pressure interface; the dust collecting hood A is provided with a port A for dust entry, a port B for dust discharge, and a port C for debris discharge from top to bottom, and the dust collecting hood A is fixedly connected to the lower end of the feeding device through port A, and the dust collecting hood A accommodates the dust outlet A of the feeding device through port A; the dust collecting hood B is provided with a port D for dust entry, a port E for dust discharge, and a port F for debris discharge from top to bottom The dust collecting hood B is fixedly connected to the outer wall of the lower end of the steel ball cleaning chamber through the port D, and the dust collecting hood B contains the dust outlet B of the steel ball cleaning chamber through the port D; the upper end of the collecting pipe A is connected to the port B of the dust collecting hood A, and the lower end is connected to the dust inlet of the dust buffer chamber; the upper end of the collecting pipe B is connected to the port E of the dust collecting hood B, and the lower end is connected to the dust inlet of the dust buffer chamber; the upper end of the collecting pipe C is connected to the port C of the dust collecting hood A, and the lower end is connected to the debris inlet of the debris collection chamber; the upper end of the collecting pipe D is connected to the port F of the dust collecting hood B, and the lower end is connected to the debris inlet of the debris collection chamber;

[0010] The positive and negative pressure air sources include a positive pressure air supply device and a negative pressure vacuum cleaner; the positive pressure air supply device is connected to the upper port of the nozzle and the main body of the dry ice cleaning machine through pipes; the negative pressure vacuum cleaner is connected to the negative pressure docking port of the dust buffer chamber through pipes.

[0011] A further technical solution of the present invention is: a dirty material bin B is installed on the feed port A of the feeding device, and a clean material bin B is installed on the discharge port B of the discharging device; the top and lower ends of the dirty material bin B are respectively provided with a dirty abrasive inlet B and a dirty abrasive discharge port B, the dirty abrasive discharge port B of the dirty material bin B is connected with the feed port A of the feeding device, and the dirty abrasive discharge port B of the dirty material bin B is provided with a valve C for controlling the discharge of abrasive; a clean abrasive inlet B and a clean abrasive discharge port B are provided on the clean material bin B, the clean abrasive inlet B of the clean material bin B is connected with the discharge port B of the discharging device, and the clean abrasive discharge port B of the clean material bin B is provided with a valve D for controlling the discharge of abrasive.

[0012] A further technical solution of the present invention is: the dirty abrasive discharge port A of the dirty material bin A is connected to the dirty abrasive inlet B of the dirty material bin B through a first screw conveyor; the clean abrasive inlet A of the clean material bin A is connected to the clean abrasive discharge port B of the clean material bin B through a second screw conveyor.

[0013] A further technical solution of the present invention is: a buffer hopper is provided between the feed port B of the discharging device and the abrasive outlet of the steel ball cleaning chamber, the top and lower ends of the buffer hopper are respectively provided with an upper inlet and a lower outlet, and a valve X for controlling the discharge of the abrasive is provided on the lower outlet of the buffer hopper, the upper inlet of the buffer hopper is connected to the abrasive outlet of the steel ball cleaning chamber, and the lower outlet of the buffer hopper is connected to the feed port B of the discharging device.

[0014] A further technical solution of the present invention is that the positive pressure air supply device comprises an air compressor, an air storage tank and a freeze dryer connected in sequence, and the positive pressure air supply device outputs a pressurized air flow through the freeze dryer.

[0015] A further technical solution of the present invention is: the feeding device is a screw feeder arranged at an inclination of 5-12° relative to the horizontal plane, one end of which is a high end and the other end is a low end, and the outside of the feed device is provided with an outer wall in the shape of a cylindrical tube, the feed port A is provided at the high end of the feeding device, the discharge port A is provided at the low end of the feeding device, and the dust outlet A is a micropore provided at the lower part of the outer wall of the feeding device and arranged in a dispersed manner. The micropores are distributed on the section between the feed port A and the discharge port A on the outer wall of the feeding device, and the micropores are used to screen out dust smaller than the abrasive.

[0016] A further technical solution of the present invention is: the discharging device is a screw feeder arranged at an inclination of 5-12° relative to the horizontal plane, one end of which is a high end and the other end is a low end, and the outside of the feed device is provided with a cylindrical tubular outer wall, the feed port B is provided at the high end of the discharging device, and the discharge port B is provided at the low end of the discharging device, the water vapor outlet is a micropore provided on the upper part of the outer wall of the discharging device and is dispersedly arranged, the micropores are distributed on the section between the feed port B and the discharge port B of the outer wall of the discharging device, the size of the micropores is smaller than the abrasive and is used to discharge water vapor; a spiral heating wire is wound around the outside of the outer wall of the discharging device.

[0017] The technical solution of the present invention is: a method for decontaminating radioactive contaminated metals, which is applied to the above-mentioned radioactive contaminated metal decontamination system, and the method is as follows:

[0018] S01, pre-treatment and loading:

[0019] A. Cutting the metal scraps into small scrap pieces using a metal cutting machine; the small scrap pieces include plate-shaped materials and three-dimensional materials. The plate-shaped materials have a length and width not exceeding 260 mm and a thickness not exceeding 50 mm. The three-dimensional materials have a length, width, and height not exceeding 200 mm and a thickness not exceeding 50 mm.

[0020] B. Put the small pieces of waste into the heat treatment furnace for oxidation treatment. The oxidation temperature is 900-950℃ and the oxidation time is 2-4 hours.

[0021] C. Put the oxidized small waste pieces into the metal hopper; the small waste pieces pass through the metal hopper, vibrating material spreader and plate chain conveyor in sequence and are put into the metal decontamination chamber of the shell;

[0022] S02, Metal Decontamination:

[0023] A. Drive the drum and conveyor belt to operate; confirm that there is sufficient abrasive stored in the net material bin A;

[0024] B. On the one hand, the valve on the pipeline between the air compressor, the air storage tank, and the freeze dryer is opened, so that the pressurized air output by the freeze dryer enters the nozzle through the upper port of the nozzle, thereby forming a negative pressure suction effect in the pipeline between the nozzle and the clean material bin A; on the other hand, the valve A on the clean abrasive discharge port A of the clean material bin A is opened. Under the action of negative pressure, the abrasive in the clean material bin A is discharged through the clean abrasive discharge port A and then enters the nozzle through the pipeline and the confluence port; on the other hand, the small pieces of waste in the metal decontamination sub-chamber are continuously turned over by the rotating drum and the conveyor belt, so that all surfaces of the small pieces of waste have the opportunity to be exposed to the abrasive spray range;

[0025] C. Based on the above three actions, the following effects are produced: the pressurized airflow entrains the abrasive and continuously ejects it from the lower port of the nozzle, impacting the various surfaces of the small waste pieces, thereby stripping away the stains, rust, and radioactive material layers on the surface of the small waste pieces, achieving the effect of radioactive decontamination; the stained abrasive falls through the abrasive passage holes on the conveyor belt into the dirty material bin A at the lower end of the abrasive collection sub-chamber;

[0026] In sub-step C of this step, the duration of the decontamination process is 5-7 minutes, and the total weight of the small waste pieces does not exceed 50 kg.

[0027] A further technical solution of the present invention is that it also includes an abrasive decontamination method subsequent to the radioactive contaminated metal decontamination method, which is subsequent to step S02 and is used to perform radioactive decontamination treatment on the abrasive; the method is as follows:

[0028] S03, prepare dry ice:

[0029] A. Prepare dry ice using a dry ice preparation device, which consists of a CO2 storage tank and a dry ice maker connected to each other via a gas pipeline. First, check the status of each valve on the dry ice maker's panel. The purge valve should be in the open position, and the gas phase valve, liquid phase valve, and vent valve should all be in the closed position. Then, open the CO2 storage tank's main vent valve and the dry ice maker's gas phase valve in sequence, and confirm that the pressure indicated on the gas phase valve pressure gauge is consistent with the pressure indicated on the CO2 storage tank's pressure gauge.

[0030] B. Open the vent valve on the dry ice machine, exhaust all the air, and then close the vent valve on the dry ice machine; open the gas phase valve of the dry ice machine, and confirm that the pressure displayed by the pressure gauge on the gas phase valve and the pressure displayed by the pressure gauge on the liquid phase valve are both between 1.2 and 2.1 MPa;

[0031] C. Start the dry ice making machine to produce dry ice pellets at a speed of 60 kg / h. After a certain period of time, transfer the prepared dry ice pellets to a dry ice storage box with insulation function for future use;

[0032] In sub-step A of this step, the pressure displayed on the pressure gauge on the gas phase valve is called the gas phase pressure, and the gas phase pressure should be controlled between 0.9 and 2.1 MPa;

[0033] In sub-step A of this step, if the gas phase pressure is within a ±8% floating range compared to the CO2 storage tank pressure, the two pressures are considered to be consistent;

[0034] In sub-step B of this procedure, the pressure displayed on the pressure gauge on the liquid phase valve is called the liquid phase pressure;

[0035] S04, device initialization:

[0036] A. Close valve X on the abrasive outlet of the steel ball cleaning chamber, open valve Y on the negative pressure interface of the dust buffer chamber, and start the negative pressure vacuum cleaner. On the one hand, the negative pressure is transmitted to the dust hood A through the pipeline, dust buffer chamber, and collection pipe A in sequence. On the other hand, the negative pressure is transmitted to the dust hood B through the pipeline, dust buffer chamber, and collection pipe B in sequence.

[0037] B, turn on the power supply of the heating wire to preheat the outer wall and inner cavity of the discharge device; put the abrasive to be purified into the dirty material bin B; put the prepared dry ice particles into the dry ice cleaning machine;

[0038] S05, abrasive primary filtration:

[0039] A, controls the feeding speed of the dirty material bin B, so that the abrasive to be purified is continuously fed into the inner cavity of the feeding device through the feed port A, and then moves to the discharge port A of the feeding device in accordance with the inclination angle of the feeding device and driven by the spiral blades inside the feeding device; during the movement of the abrasive, dust smaller than the abrasive is discharged through the dust outlet A of the feeding device, and then is received by the port A of the dust collecting hood A and enters the inner cavity of the dust collecting hood A; the debris with relatively large specific gravity in the abrasive falls under the action of its own gravity, and is discharged from the port C at the lower end of the dust collecting hood A, and then enters the inner cavity of the debris collecting chamber through the collection pipe C and the debris inlet of the debris collecting chamber; the debris with relatively small specific gravity in the abrasive is discharged from the port B in the middle of the dust collecting hood A under the action of negative pressure, and then passes through the collection pipe A, the dust buffer chamber and the pipeline in sequence and enters the negative pressure vacuum cleaner; at this point, the preliminary filtration of the abrasive is completed;

[0040] B. The abrasive that has completed the preliminary filtration is discharged through the discharge port A of the feeding device, and then enters the inner cavity of the steel ball cleaning chamber through the abrasive inlet of the steel ball cleaning chamber;

[0041] S06, abrasive cleaning:

[0042] A. Open the valve on the pipeline between the air compressor, air tank, and freeze dryer, allowing the pressurized airflow output by the freeze dryer to continuously enter the dry ice cleaning machine, providing the power for the dry ice particles to flow. Then, start the dry ice cleaning machine, causing the pressurized airflow to spray dry ice particles from the spray gun, striking the abrasive in the inner cavity of the steel ball cleaning chamber. On the one hand, under the continuous impact of the airflow and dry ice, the abrasive collides with each other in the inner cavity of the steel ball cleaning chamber, and the collision process strips away the dirt containing radionuclides on the abrasive surface. On the other hand, there is a temperature difference between the dry ice and the abrasive. When the dry ice collides with the abrasive, the physical reaction based on the temperature difference causes the different substances to shrink at different rates, thereby stripping away the dirt containing radionuclides on the abrasive surface.

[0043] During the cleaning process, the dirt containing radioactive nuclides peeled off from the surface of the abrasive is discharged through the dust outlet B, and then is contained by the port D of the dust hood B and enters the inner cavity of the dust hood B. The heavier part of the dirt falls under the action of its own gravity and is discharged from the port F at the bottom of the dust hood B, and then enters the inner cavity of the debris collection chamber through the collection pipe D and the debris inlet of the debris collection chamber. The lighter part of the dirt is discharged from the port E in the middle of the dust hood B under the action of negative pressure, and then enters and is trapped in the negative pressure vacuum cleaner through the collection pipe B, the dust inlet of the dust buffer chamber, the negative pressure interface and pipeline of the dust buffer chamber.

[0044] C. After cleaning for a certain period of time, open valve X on the steel ball cleaning chamber and valve Z on the buffer hopper, so that the abrasive in the inner cavity of the steel ball cleaning chamber is discharged through the abrasive outlet at the lower end of the steel ball cleaning chamber and then enters the buffer hopper through the pipeline;

[0045] In this step, the dry ice cleaning machine sprays dry ice at a rate of 30-200 kg / h and an air flow rate of 1.8-3.5 m 3 / min;

[0046] S07, abrasive drying:

[0047] The feeding speed of the buffer hopper is controlled so that the cleaned abrasive is continuously input into the inner cavity of the discharge device through the feed port B, and then moves toward the discharge port B of the discharge device in accordance with the inclination angle of the discharge device and driven by the spiral blades inside the discharge device. During the movement of the abrasive, the abrasive is heated by the preheated discharge device to achieve drying, and the water vapor generated by the evaporation of the abrasive is discharged to the outside through the water vapor outlet of the discharge device. The dried abrasive enters the clean material bin B for temporary storage.

[0048] Compared with the prior art, the present invention has the following advantages:

[0049] 1. It is used to decontaminate radioactive contaminated metals, providing a prerequisite for their reuse and resolving the problem that current disposal solutions for radioactive contaminated metals fail to meet the requirements of "radioactive waste minimization." Most radioactive contaminated metals are collected from nuclear power plants or nuclear industrial enterprises. Except for a small portion of metal (such as metal inside the reactor core) that is radioactively contaminated throughout, most metals are contaminated only on the surface.

[0050] 2. In the radioactive contaminated metal decontamination method, the radioactive contaminants on the metal surface undergo oxidation reaction through oxidation treatment to form an oxide scale that is easy to peel off, thereby improving the decontamination effect of the subsequent shot peening treatment. The metal surface is struck at high speed by abrasives (steel shots), effectively peeling off stains, rust and oxide scale containing radioactive nuclides, thereby achieving the effect of radioactive decontamination. By performing surface radioactive decontamination treatment on the abrasives (steel shots), the abrasives (steel shots) in the radioactive contaminated metal decontamination process are recycled, which is a key technology to ensure that the radioactive contaminated metal decontamination process does not produce secondary pollution.

[0051] 2. In the abrasive decontamination method, dry ice particles entrained in a pressurized airflow strike the abrasive (steel shot) surface, achieving radioactive decontamination of the abrasive (steel shot). On the one hand, under the continuous impact of the airflow and dry ice, the abrasives collide with each other, stripping away a small portion of radioactive contaminants from the abrasive surface. On the other hand, the temperature difference between the dry ice and the abrasive causes the different materials to shrink at different rates due to the physical reaction of the temperature difference, thereby stripping away the majority of the radioactive contaminants from the abrasive surface. Specifically, when the dry ice particles come into contact with the abrasive surface, they cause an embrittlement explosion, shrinking and loosening the contaminants. Subsequently, the dry ice particles instantly vaporize and expand 800 times, generating a powerful stripping force that quickly and thoroughly removes the contaminants from the surface, achieving a fast, efficient, safe, and energy-efficient cleaning effect.

[0052] The present invention is further described below with reference to the figures and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a structural schematic diagram of the present invention;

[0054] Figure 2 This is a schematic diagram of the positional relationship between the metal feeding device and the metal decontamination device;

[0055] Figure 3 It is a structural schematic diagram of an abrasive purification device;

[0056] Figure 4 for Figure 3 A magnified view of part A;

[0057] Figure 5 A diagram showing the gas path connections of various components based on pressure and gas flow communication;

[0058] Figure 6 Schematic diagram of the abrasive circulation flow route.

[0059] Legend: Metal hopper 11; Vibrating paving machine 12; Plate chain conveyor 13; Housing 21; Material inlet 211; Metal decontamination chamber 212; Abrasive collecting chamber 213; Upper rotary wheel 221; Lower rotary wheel 222; Conveyor belt 223; Rotating drum 231; Nozzle 24; Confluence port 241; Clean material bin A25; Clean abrasive inlet A251; Clean abrasive outlet A252; Dirty material bin A26; Dirty abrasive inlet A261; Dirty abrasive outlet A262; Feeding device 31; Feeding port A311; Discharging port A312; Discharging device 32; Feeding port B321; Discharging port B322; Steel ball cleaning chamber 33; Dry ice inlet 331; Abrasive inlet 332; Dust outlet B333; Abrasive Outlet 334; dry ice cleaning machine 34; main body 341; spray gun 342; debris collection chamber 35; debris inlet 351; dust buffer chamber 36; dust inlet 361; negative pressure docking port 362; dust hood A37; port B371; dust hood B38; port E381; collection pipe A391; collection pipe B392; collection pipe C393; collection pipe D394; air compressor 41; air storage tank 42; freeze dryer 43; valve A100; valve B200; valve X300; valve Y400; dirty material bin B500; valve C501; clean material bin B600; first screw conveyor 700; second screw conveyor 800; buffer hopper 900; valve Z901.

[0060] Special Notes: Figure 1 In order to avoid cluttered lines, the first screw conveyor and the second screw conveyor are not drawn; Figure 3 Due to limited image space, the main body of the dry ice cleaning machine is not shown; Figure 5 The arrow in the middle shows the direction of airflow; Figure 5 The structure of each component and the gas connection method of each component are prior art, so only a block diagram is provided; Figure 6 The arrow in the middle shows the flow direction of the abrasive. DETAILED DESCRIPTION Example 1

[0061] like Figure 1-6 As shown, the radioactive contaminated metal decontamination system includes a metal feeding device, a metal decontamination device, an abrasive purification device and positive and negative pressure air sources.

[0062] The metal feeding device includes a metal hopper 11, a vibrating spreader 12, and a plate chain conveyor 13, which are connected in sequence. The metal hopper 11 has an upper port for feeding metal fragments and a lower port for discharging metal fragments. The lower port of the metal hopper 11 is equipped with a valve A for controlling the discharge of metal fragments. The vibrating spreader 12 has one end as the upper end and the other end as the lower end, with the upper end of the vibrating spreader located directly below the lower end of the metal hopper. The plate chain conveyor 13 has one end as the feed end and the other end as the discharge end, with the feed end of the plate chain conveyor 13 positioned adjacent to the lower end of the vibrating spreader 12.

[0063] The metal decontamination device includes a housing 21, a C-shaped conveyor belt assembly, a rotating drum assembly, a nozzle 24, a clean material bin A25, and a dirty material bin A26. The housing 21 has an inner cavity and a material inlet 211 on one side. The material inlet 211 of the housing 21 is arranged adjacent to the plate chain conveyor 13. The C-shaped conveyor belt assembly includes an upper rotary wheel 221, a lower rotary wheel 222 and a conveyor belt 223. The upper rotary wheel 221 is located obliquely above the lower rotary wheel 222. The conveyor belt 223 is wound between the upper rotary wheel 221 and the lower rotary wheel 222 and is arranged in a C shape as a whole, so that the two sides of the conveyor belt 223 form an outer arc area and an inner arc area respectively. The conveyor belt 223 is provided with an abrasive passage hole for abrasive to pass through. The conveyor belt 223 divides the inner cavity of the outer shell 21 from top to bottom into a metal decontamination sub-cavity 212 and an abrasive collecting sub-cavity 213. The metal decontamination sub-cavity 212 and the abrasive collecting sub-cavity 213 are connected through the abrasive passage hole. The metal decontamination sub-cavity 212 is connected to the material inlet 211 of the outer shell 21. The metal decontamination sub-cavity 212 is located in the inner arc area of the conveyor belt 223, and the abrasive collecting sub-cavity 213 is located in the outer arc area of the conveyor belt 223. The drum assembly comprises a horizontally arranged drum 231 and a motor (not shown) for driving the drum 231. The drum 231 is located within the inner arc of the conveyor belt 223, forming an arc-shaped gap between the outer surface of the drum 231 and the upper surface of the conveyor belt 223. The nozzle 24 is vertically arranged at the upper end of the metal decontamination subchamber 212 of the housing 21. Its upper port is used to receive the pressurized airflow, and its lower port is used to eject the abrasive and pressurized airflow. A confluence port 241 for receiving the abrasive is located in the center of the nozzle. A clean abrasive inlet A251 and a clean abrasive outlet A252 are provided in the clean material bin A25. The clean abrasive outlet A252 of the clean material bin A25 is connected to the confluence port 241 of the nozzle 24 via a pipe. A valve A100 is provided at the clean abrasive outlet A252 of the clean material bin A25 to control the discharge of the abrasive. The top and bottom of the dirty material bin A26 are respectively provided with a dirty abrasive inlet A261 and a dirty abrasive outlet A262. The dirty abrasive outlet A262 of the dirty material bin A26 is provided with a valve B200 for controlling the discharge of abrasive. The dirty material bin A26 is installed in the abrasive collecting sub-chamber 213 of the outer shell 21, and the dirty abrasive inlet A261 thereon is located directly below the conveyor belt 223.

[0064] The abrasive purification device includes a feeder 31, a discharger 32, a steel ball cleaning chamber 33, a dry ice blaster 34, and a dust collection device. The feeder 31 has a feed port A311 at its top and a discharge port A312 at its bottom. A dust outlet A is located on the lower portion of the outer wall of the feeder 31 between the feed port A311 and the discharge port A312. The discharger 32 has a feed port B321 at its top and a discharge port B322 at its bottom. A vapor outlet is located on the upper portion of the outer wall of the discharger 32 between the feed port B321 and the discharge port B322. The steel ball cleaning chamber 33 has an internal cavity. From top to bottom, the exterior of the chamber is equipped with a dry ice inlet 331, an abrasive inlet 332, a dust outlet B333, and an abrasive outlet 334. The abrasive inlet 332 is connected to the discharge port A12 of the feed device 31, and the abrasive outlet 334 is connected to the feed port B321 of the discharge device 32. A valve X300 is provided on the abrasive outlet 334 to control the discharge of the abrasive. The dry ice cleaning machine 34 includes a main body 341 and a spray gun 342, which are interconnected. The spray gun 342 is connected to the dry ice inlet 331 of the steel ball cleaning chamber 33 to spray dry ice particles into the internal cavity of the chamber 33. The dust collection device includes a debris collection chamber 35, a dust buffer chamber 36, a dust hood A37, a dust hood B38, and collection pipes A391, B392, C393, and D394. A debris inlet 351 is provided at the top of the debris collection chamber 35. The dust buffer chamber 36 is provided with a dust inlet 361 and a negative pressure port 362, respectively, from top to bottom. The negative pressure port 362 is equipped with a valve Y400 for controlling the air flow. The dust hood A37 is provided with, from top to bottom, a dust inlet port A, a dust outlet port B371, and a debris outlet port C. Dust hood A37 is fixedly connected to the lower end of the feeder 31 via port A, and hood A37 accommodates the dust outlet A of the feeder 31 through port A. Dust hood B38 is provided with, from top to bottom, a dust inlet port D, a dust outlet port E381, and a debris outlet port F. Dust hood B38 is fixedly connected to the outer wall of the lower end of the steel ball cleaning chamber 33 via port D, and hood B38 accommodates the dust outlet B333 of the steel ball cleaning chamber 33 through port D. The upper end of collection pipe A391 is connected to port B371 of dust hood A37, and the lower end is connected to dust inlet 361 of dust buffer chamber 36. The upper end of collection pipe B392 is connected to port E381 of dust hood B38, and the lower end is connected to dust inlet 361 of dust buffer chamber 36. The upper end of collection pipe C393 is connected to port C of dust hood A37, and the lower end is connected to debris inlet 351 of debris collection chamber 35. The upper end of collection pipe D394 is connected to port F of dust hood B38, and the lower end is connected to debris inlet 351 of debris collection chamber 35.

[0065] The positive and negative pressure air sources include a positive pressure air supply device and a negative pressure vacuum cleaner (not shown). The positive pressure air supply device includes an air compressor 41, an air tank 42, and a freeze dryer 43, which are connected in sequence. The positive pressure air supply device outputs pressurized airflow through the freeze dryer 43, which is connected to the upper port of the nozzle 24 and the main body 341 of the dry ice cleaning machine 34 via pipes. The negative pressure vacuum cleaner is connected to the negative pressure docking port 362 of the dust buffer chamber 36 via a pipe.

[0066] Preferably, a dirty material bin B500 is mounted on the feed port A311 of the feed device 31, and a clean material bin B600 is mounted on the discharge port B322 of the discharge device 32. A dirty abrasive inlet B and a dirty abrasive outlet B are respectively provided at the top and bottom of the dirty material bin B500. The dirty abrasive outlet B of the dirty material bin B500 communicates with the feed port A311 of the feed device 31, and a valve C501 for controlling abrasive discharge is provided at the dirty abrasive outlet B of the dirty material bin B500. A clean abrasive inlet B and a clean abrasive outlet B are provided in the clean material bin B600. The clean abrasive inlet B of the clean material bin B600 communicates with the discharge port B322 of the discharge device 32, and a valve D601 for controlling abrasive discharge is provided at the clean abrasive outlet B of the clean material bin B600.

[0067] Preferably, the dirty abrasive outlet A of the dirty bin A26 is connected to the dirty abrasive inlet B of the dirty bin B500 via a first screw conveyor 700. The clean abrasive inlet A of the clean bin A25 is connected to the clean abrasive outlet B of the clean bin B600 via a second screw conveyor 800.

[0068] Preferably, a buffer hopper 900 is provided between the feed port B321 of the discharging device 32 and the abrasive outlet 334 of the steel ball cleaning chamber 33. The top and lower ends of the buffer hopper 900 are respectively provided with an upper inlet and a lower outlet. A valve Z901 for controlling the discharge of abrasive is provided on the lower outlet of the buffer hopper 900. The upper inlet of the buffer hopper 900 is connected to the abrasive outlet 334 of the steel ball cleaning chamber 33, and the lower outlet of the buffer hopper 900 is connected to the feed port B321 of the discharging device 32.

[0069] Preferably, the feed device 31 is a screw feeder arranged at an inclination of 5-12° relative to the horizontal plane, with one end being the high end and the other being the low end. The feed device 31 is provided with a cylindrical outer wall. The feed port A311 is provided at the high end of the feed device 31, and the discharge port A312 is provided at the low end of the feed device 31. The dust outlet A is micropores dispersedly arranged at the lower portion of the outer wall of the feed device 31. The micropores are distributed in the section between the feed port A311 and the discharge port A312 on the outer wall of the feed device 31. The micropores are used to screen out dust smaller than the abrasive. Based on this structure, on the one hand, the movement path of the abrasive within the feed device 31 is relatively long, thereby enabling a more complete primary filtration process. On the other hand, the rotation of the spiral blades within the feed device 31 allows the abrasive to be fully agitated during movement, thereby enabling a more complete primary filtration process.

[0070] Preferably, the discharge device 32 is a spiral feeder arranged at an angle of 5-12° relative to the horizontal plane, one end of which is the high end and the other end is the low end. The outside of the feed device 32 is provided with an outer wall in the shape of a cylindrical tube. The feed port B321 is provided at the high end of the discharge device 32, and the discharge port B322 is provided at the low end of the discharge device 32. The water vapor outlet is a dispersed micropore provided on the upper part of the outer wall of the discharge device 32. The micropores are distributed in the section between the feed port B321 and the discharge port B322 on the outer wall of the discharge device 32. The micropore size is smaller than the abrasive and is used to discharge water vapor. A spiral heating wire (not shown) is wound around the outer wall of the discharge device 32. Based on this structure, on the one hand, the movement path of the abrasive inside the discharge device 32 is relatively long, thereby making the drying process more sufficient. On the other hand, the rotation of the spiral blades inside the discharge device 32 makes the abrasive fully stirred during movement, thereby making the drying process more sufficient.

[0071] Briefly describe the working principle of the present invention:

[0072] A method for decontaminating radioactive contaminated metals is provided, based on the above-mentioned radioactive contaminated metal decontamination system, and the method is as follows:

[0073] S01, pre-treatment and loading:

[0074] A. Cutting the metal scraps into small scrap pieces using a metal cutting machine; the small scrap pieces include plate-shaped materials and three-dimensional materials. The plate-shaped materials have a length and width not exceeding 260 mm and a thickness not exceeding 50 mm. The three-dimensional materials have a length, width, and height not exceeding 200 mm and a thickness not exceeding 50 mm.

[0075] B. Put the small pieces of waste into the heat treatment furnace for oxidation treatment. The oxidation temperature is 900-950℃ and the oxidation time is 2-4 hours.

[0076] C. Put the oxidized small waste pieces into the metal upper hopper 11; the small waste pieces pass through the metal upper hopper 11, the vibrating paving machine 12 and the plate chain conveyor 13 in sequence and are put into the metal decontamination sub-cavity 212 of the shell 21.

[0077] S02, Metal Decontamination:

[0078] A. Drive the rotating drum 231 and the conveyor belt 223 to operate; confirm that there is sufficient abrasive stored in the clean material bin A25;

[0079] B. On the one hand, open the valve on the pipeline between the air compressor 41, the air tank 42, and the freeze dryer 43, allowing the pressurized air output by the freeze dryer 43 to enter the nozzle 24 through the upper port of the nozzle 24, thereby forming a negative pressure suction effect in the pipeline between the nozzle 24 and the clean material bin A25. On the other hand, open the valve A100 on the clean abrasive discharge port A of the clean material bin A25. Under the action of negative pressure, the abrasive in the clean material bin A25 is discharged through the clean abrasive discharge port A and then enters the nozzle 24 through the pipeline and the confluence port 241. On the other hand, the small pieces of waste in the metal decontamination sub-chamber 212 are continuously turned over by the rotating drum 231 and the conveyor belt 223, so that all surfaces of the small pieces of waste have the opportunity to be exposed to the abrasive spray range.

[0080] C. Based on the above three actions, the following effects are produced: the pressurized airflow carries the abrasive and is continuously ejected from the lower port of the nozzle 24, impacting the surfaces of the small waste pieces, thereby peeling off the stains, rust and radioactive material layers on the surfaces of the small waste pieces, achieving the effect of radioactive decontamination; the stained abrasive falls into the waste bin A26 at the lower end of the abrasive collection sub-chamber 213 through the abrasive passage holes on the conveyor belt 223.

[0081] In sub-step C of this step, the duration of the decontamination process is 5-7 minutes, and the total weight of the small waste pieces does not exceed 50 kg.

[0082] A method for decontaminating an abrasive, following step S02, for performing radioactive decontamination on the abrasive; the method is as follows:

[0083] S03, prepare dry ice:

[0084] A. Prepare dry ice using a dry ice preparation device, which includes a CO2 storage tank and a dry ice maker connected to each other via a gas pipeline. First, check the status of each valve on the equipment panel of the dry ice maker (the valves include the gas phase valve, liquid phase valve, vent valve, and purge valve). The purge valve should be in the open position, and the gas phase valve, liquid phase valve, and vent valve should all be in the closed position. Then, open the CO2 storage tank's main vent valve and the dry ice maker's gas phase valve in sequence, and confirm that the pressure displayed on the gas phase valve pressure gauge is consistent with the pressure displayed on the CO2 storage tank's pressure gauge.

[0085] B. Open the vent valve on the dry ice machine, exhaust all the air, and then close the vent valve on the dry ice machine; open the gas phase valve of the dry ice machine, and confirm that the pressure displayed by the pressure gauge on the gas phase valve and the pressure displayed by the pressure gauge on the liquid phase valve are both between 1.2 and 2.1 MPa;

[0086] C. Start the dry ice making machine to produce dry ice pellets. The ice making speed is controlled at 60kg / h. After a certain period of ice making, the prepared dry ice pellets are transferred to a dry ice storage box with insulation function for standby use.

[0087] In sub-step A of this step, the pressure displayed on the pressure gauge on the gas phase valve is called the gas phase pressure, and the gas phase pressure should be controlled between 0.9 and 2.1 MPa.

[0088] In sub-step A of this step, the gas phase pressure is considered to be consistent with the CO2 tank pressure within a floating range of ±8%.

[0089] In sub-step B of this procedure, the pressure displayed on the pressure gauge on the liquid phase valve is called the liquid phase pressure.

[0090] S04, device initialization:

[0091] A. Close valve X300 on the abrasive outlet 334 of the steel ball cleaning chamber 33, open valve Y400 on the negative pressure docking port 362 of the dust buffer chamber 36, and start the negative pressure vacuum cleaner. On the one hand, the negative pressure is transmitted to the dust hood A37 through the pipeline, dust buffer chamber 36, and collection pipe A391 in sequence. On the other hand, the negative pressure is transmitted to the dust hood B38 through the pipeline, dust buffer chamber 36, and collection pipe B392 in sequence.

[0092] B. Turn on the power supply of the heating wire to preheat the outer wall and inner cavity of the discharge device 32; put the abrasive to be purified into the dirty material bin B500; and put the prepared dry ice particles into the dry ice cleaning machine 34.

[0093] S05, abrasive primary filtration:

[0094] A. Control the feeding rate of the dirty material bin B500 so that the abrasive to be purified is continuously fed into the inner cavity of the feed device 31 through the feed port A311. Then, driven by the spiral blades within the feed device 31 and following the inclination of the feed device 31, it moves toward the discharge port A312 of the feed device 31. During this movement, dust particles smaller than the abrasive are discharged through the dust outlet A of the feed device 31. They are then received by port A of the dust hood A37 and enter the inner cavity of the dust hood A37. The relatively heavy debris in the abrasive falls under its own gravity and is discharged from port C at the lowest end of the dust hood A37. It then enters the inner cavity of the debris collection chamber 35 through the collection pipe C393 and the debris inlet 351 of the debris collection chamber 35. The relatively light-weight debris in the abrasive is discharged from the port B371 in the middle of the dust hood A37 under the action of negative pressure, and then passes through the collection pipe A391, the dust buffer chamber 36 and the pipeline in sequence, and enters the negative pressure vacuum cleaner; thus, the initial filtration of the abrasive is completed;

[0095] B. The abrasive that has completed the preliminary filtration is discharged through the discharge port A312 of the feeding device 31 , and then enters the inner cavity of the steel ball cleaning chamber 33 through the abrasive inlet 332 of the steel ball cleaning chamber 33 .

[0096] S06, abrasive cleaning:

[0097] A. Open the valve on the pipeline between the air compressor 41, the air tank 42 and the freeze dryer 43, so that the pressurized airflow output by the freeze dryer is continuously input into the dry ice cleaning machine 34 to provide power for the flow of dry ice particles. Then start the dry ice cleaning machine 34, so that the pressurized airflow entrained with dry ice particles is ejected from the spray gun 342 and hits the abrasive in the inner cavity of the steel ball cleaning chamber 33. On the one hand, under the continuous impact of the airflow and dry ice, the abrasive collides with each other in the inner cavity of the steel ball cleaning chamber 33, and the dirt containing radioactive nuclides on the surface of the abrasive is peeled off through the collision process. On the other hand, there is a temperature difference between the dry ice and the abrasive. When the dry ice collides with the abrasive, the physical reaction based on the temperature difference causes different substances to produce different contraction speeds, thereby peeling off the dirt containing radioactive nuclides on the surface of the abrasive;

[0098] During the cleaning process, radioactive dirt stripped from the abrasive surface is discharged through dust outlet B333 and then contained by port D of dust hood B38, entering the inner cavity of dust hood B. The heavier portion of the dirt falls under its own gravity and is discharged from port F at the bottom of dust hood B38, then enters the inner cavity of debris collection chamber 35 through collection pipe D394 and debris inlet 351 of debris collection chamber 35. The lighter portion of the dirt is discharged from port E381 in the middle of dust hood B38 under the action of negative pressure, then passes through collection pipe B392, dust inlet 361 of dust buffer chamber 36, negative pressure interface 362 of dust buffer chamber 36, and the pipeline, entering and being trapped in the negative pressure vacuum cleaner.

[0099] C. After cleaning for a certain period of time, open the valve X300 on the steel ball cleaning chamber 33 and open the valve Z901 on the buffer hopper 900, so that the abrasive in the inner cavity of the steel ball cleaning chamber 33 is discharged through the abrasive outlet 334 at the lower end of the steel ball cleaning chamber 33, and then enters the buffer hopper 900 through the pipeline.

[0100] In this step, the amount of dry ice sprayed out by the spray gun 342 of the dry ice cleaning machine 34 is 30-200 kg / h, and the air flow rate of the spray gun 342 of the dry ice cleaning machine 34 is 1.8-3.5 m 3 / min.

[0101] S07, abrasive drying:

[0102] The feeding rate of the buffer hopper 900 is controlled so that the cleaned abrasive is continuously fed into the inner cavity of the discharge device 32 through the feed port B321. Then, driven by the spiral blades within the discharge device 32, it moves toward the discharge port B322 of the discharge device 32, following the inclination angle of the discharge device 32. During this movement, the abrasive is heated by the preheated discharge device 32, drying it. The water vapor generated by the evaporation of the abrasive is discharged to the outside through the water vapor outlet of the discharge device 32. The dried abrasive is then temporarily stored in the clean material bin B600.

Claims

1. Radioactive contaminated metal decontamination system, characterized by: It includes metal feeding device, metal decontamination device, abrasive purification device and positive and negative pressure air source; The metal feeding device includes a metal feeding hopper, a vibrating material spreading machine and a plate chain conveyor which are connected in sequence; The metal decontamination device includes an outer shell, a C-shaped conveyor belt assembly, a drum assembly, a nozzle, a clean material bin A and a dirty material bin A; an inner cavity is provided inside the outer shell, and a material inlet is provided on one side of the outer shell, and the material inlet of the outer shell is arranged adjacent to the plate chain conveyor; the C-shaped conveyor belt assembly includes an upper wheel, a lower wheel and a conveyor belt, the upper wheel is located obliquely above the lower wheel, the conveyor belt is wound between the upper wheel and the lower wheel and is arranged in a C shape as a whole, so that the outer arc area and the inner arc area are formed on both sides of the conveyor belt respectively, and an abrasive passage hole is provided on the conveyor belt, and the conveyor belt separates the inner cavity of the outer shell from top to bottom into a metal decontamination sub-chamber and an abrasive collecting sub-chamber, the metal decontamination sub-chamber and the abrasive collecting sub-chamber are connected through the abrasive passage hole, the metal decontamination sub-chamber is connected with the material inlet, the metal decontamination sub-chamber is located in the inner arc area of the conveyor belt, and the abrasive collecting sub-chamber is located in the outer arc area of the conveyor belt; the drum assembly includes a horizontally arranged drum and a motor for driving the drum to rotate, the drum is located in the inner arc area of the conveyor belt, and an arc-shaped gap is formed between the outer cylindrical surface of the drum and the upper surface of the conveyor belt; the nozzle is vertically arranged at the upper end of the metal decontamination sub-chamber of the shell, and its upper port is used to receive the pressurized airflow, and its lower port is used to spray out the abrasive and the pressurized airflow, and a confluence port for receiving the abrasive is provided in the middle thereof; a clean abrasive inlet A and a clean abrasive discharge port A are provided on the clean material bin A; the clean abrasive discharge port A of the clean material bin A is connected with the confluence port of the nozzle through a pipeline, and a valve A for controlling the discharge of the abrasive is provided on the clean abrasive discharge port A of the clean material bin A; a dirty abrasive inlet A and a dirty abrasive discharge port A are respectively provided at the top and lower end of the dirty material bin A, and a valve B for controlling the discharge of the abrasive is provided on the dirty abrasive discharge port A of the dirty material bin A, and the dirty material bin A is installed in the abrasive collecting sub-chamber of the shell, and the dirty abrasive inlet A thereon is located directly below the conveyor belt; The abrasive purification device includes a feeding device, a discharging device, a steel ball cleaning chamber, a dry ice cleaning machine and a dust collecting device; the feeding device is provided with a feeding port A at the upper end, a discharging port A at the lower end, and a dust outlet A at the lower part of the outer wall between the feeding port A and the discharging port A; the discharging device is provided with a feeding port B at the upper end, a discharging port B at the lower end, and a water vapor outlet hole at the upper part of the outer wall between the feeding port B and the discharging port B; the steel ball cleaning chamber is provided with an inner cavity, and the steel ball cleaning The outside of the chamber is provided with a dry ice inlet, an abrasive inlet, a dust outlet B and an abrasive outlet from top to bottom, the abrasive inlet is connected to the discharge port A of the feeding device, the abrasive outlet is connected to the feed port B of the discharging device, and a valve X is provided on the abrasive outlet; the dry ice cleaning machine includes a main body and a spray gun, the spray gun is connected to the dry ice inlet of the steel ball cleaning chamber; the dust collection device includes a debris collection chamber, a dust buffer chamber, a dust hood A, a dust hood B, a collection pipe A, a collection pipe B, a collection pipe C and a collection pipe D; a debris inlet is provided at the upper end of the debris collection chamber; the dust buffer chamber is provided with a dust inlet and a negative pressure docking port from top to bottom, and a valve Y is provided on the negative pressure docking port; the dust hood A is provided with a port A for dust entry, a port B for dust discharge and a port C for debris discharge from top to bottom, and the dust hood A accommodates the dust outlet A of the feeding device through port A; the dust hood B is provided with a port D for dust entry, a port E for dust discharge and a port C for debris discharge from top to bottom Port F, dust hood B contains the dust outlet B of the steel ball cleaning chamber through port D; the upper end of the collection pipe A is connected to port B of the dust hood A, and the lower end is connected to the dust inlet of the dust buffer chamber; the upper end of the collection pipe B is connected to port E of the dust hood B, and the lower end is connected to the dust inlet of the dust buffer chamber; the upper end of the collection pipe C is connected to port C of the dust hood A, and the lower end is connected to the debris inlet of the debris collection chamber; the upper end of the collection pipe D is connected to port F of the dust hood B, and the lower end is connected to the debris inlet of the debris collection chamber; The positive and negative pressure air sources include a positive pressure air supply device and a negative pressure vacuum cleaner; The positive pressure air supply device is connected to the upper port of the nozzle and the main body of the dry ice cleaning machine through pipelines; the negative pressure vacuum cleaner is connected to the negative pressure interface of the dust buffer chamber through pipelines.

2. The radioactive contaminated metal decontamination system according to claim 1, characterized in that: A dirty material bin B is installed on the feed port A of the feeding device, and a clean material bin B is installed on the discharge port B of the discharging device; a dirty abrasive inlet B and a dirty abrasive discharge port B are respectively provided at the top and bottom of the dirty material bin B, the dirty abrasive discharge port B of the dirty material bin B is communicated with the feed port A of the feeding device, and a valve C for controlling the discharge of abrasive is provided at the dirty abrasive discharge port B of the dirty material bin B; a clean abrasive inlet B and a clean abrasive discharge port B are provided on the clean material bin B, the clean abrasive inlet B of the clean material bin B is communicated with the discharge port B of the discharging device, and a valve D for controlling the discharge of abrasive is provided at the clean abrasive discharge port B of the clean material bin B.

3. The radioactive contaminated metal decontamination system according to claim 2, characterized in that: The dirty abrasive outlet A of the dirty material bin A is connected to the dirty abrasive inlet B of the dirty material bin B through a first screw conveyor; the clean abrasive inlet A of the clean material bin A is connected to the clean abrasive outlet B of the clean material bin B through a second screw conveyor.

4. The radioactive contaminated metal decontamination system according to claim 3, characterized in that: A buffer hopper is provided between the feed port B of the discharging device and the abrasive outlet of the steel ball cleaning chamber. The top and lower ends of the buffer hopper are respectively provided with an upper inlet and a lower outlet. A valve Z for controlling the discharge of the abrasive is provided on the lower outlet of the buffer hopper. The upper inlet of the buffer hopper is connected to the abrasive outlet of the steel ball cleaning chamber, and the lower outlet of the buffer hopper is connected to the feed port B of the discharging device.

5. The radioactive contaminated metal decontamination system according to claim 4, characterized in that: The positive pressure air supply device comprises an air compressor, an air storage tank and a freeze dryer which are connected in sequence, and the positive pressure air supply device outputs a pressurized air flow through the freeze dryer.

6. The radioactive contaminated metal decontamination system according to claim 5, characterized in that: The feeding device is a screw feeder arranged at an inclination of 5-12 degrees relative to the horizontal plane, one end of which is a high end and the other end is a low end. The outside of the feeder is provided with a cylindrical tubular outer wall. The feed port A is provided at the high end of the feeding device, and the discharge port A is provided at the low end of the feeding device. The dust outlet A is micropores provided at the lower part of the outer wall of the feeding device and arranged in a dispersed manner. The micropores are distributed in the section between the feed port A and the discharge port A on the outer wall of the feeding device. The micropores are used to screen out dust smaller than the abrasive.

7. The radioactive contaminated metal decontamination system according to claim 6, characterized in that: The discharging device is a screw feeder arranged at an inclination of 5-12° relative to the horizontal plane, one end of which is the high end and the other end is the low end. The outside of the feeder is provided with a cylindrical tubular outer wall. The feed port B is provided at the high end of the discharging device, and the discharge port B is provided at the low end of the discharging device. The water vapor outlet is a micropore provided on the upper part of the outer wall of the discharging device and is dispersedly arranged. The micropores are distributed in the section between the feed port B and the discharge port B on the outer wall of the discharging device. The size of the micropores is smaller than the abrasive and is used to discharge water vapor. A spiral heating wire is wound around the outside of the outer wall of the discharging device.

8. A method for decontaminating radioactive contaminated metals, based on the radioactive contaminated metal decontamination system according to claim 7, wherein the method is as follows: S01, pre-treatment and loading: A. Cutting the metal scraps into small scrap pieces using a metal cutting machine; the small scrap pieces include plate-shaped materials and three-dimensional materials. The plate-shaped materials have a length and width not exceeding 260 mm and a thickness not exceeding 50 mm. The three-dimensional materials have a length, width, and height not exceeding 200 mm and a thickness not exceeding 50 mm. B. Put the small pieces of waste into the heat treatment furnace for oxidation treatment. The oxidation temperature is 900-950℃ and the oxidation time is 2-4 hours. C. Put the oxidized small waste pieces into the metal hopper; the small waste pieces pass through the metal hopper, vibrating material spreader and plate chain conveyor in sequence and are put into the metal decontamination chamber of the shell; S02, Metal Decontamination: A. Drive the drum and conveyor belt to operate; confirm that there is sufficient abrasive stored in the net material bin A; B. On the one hand, the valve on the pipeline between the air compressor, the air storage tank, and the freeze dryer is opened, so that the pressurized air output by the freeze dryer enters the nozzle through the upper port of the nozzle, thereby forming a negative pressure suction effect in the pipeline between the nozzle and the clean material bin A; on the other hand, the valve A on the clean abrasive discharge port A of the clean material bin A is opened. Under the action of negative pressure, the abrasive in the clean material bin A is discharged through the clean abrasive discharge port A and then enters the nozzle through the pipeline and the confluence port; on the other hand, the small pieces of waste in the metal decontamination sub-chamber are continuously turned over by the rotating drum and the conveyor belt, so that all surfaces of the small pieces of waste have the opportunity to be exposed to the abrasive spray range; C. Based on the above three actions, the following effects are produced: the pressurized airflow entrains the abrasive and continuously ejects it from the lower port of the nozzle, impacting the various surfaces of the small waste pieces, thereby stripping away the stains, rust, and radioactive material layers on the surface of the small waste pieces, achieving the effect of radioactive decontamination; the stained abrasive falls through the abrasive passage holes on the conveyor belt into the dirty material bin A at the lower end of the abrasive collection sub-chamber; In sub-step C of this step, the duration of the decontamination process is 5-7 minutes, and the total weight of the small waste pieces does not exceed 50 kg.

9. The method for decontaminating radioactive contaminated metals according to claim 8, wherein: The method further includes an abrasive decontamination method following the radioactive contaminated metal decontamination method. The abrasive decontamination method follows step S02 and is used to perform radioactive decontamination on the abrasive. The method is as follows: S03, prepare dry ice: A. Prepare dry ice using a dry ice preparation device, which consists of a CO2 storage tank and a dry ice maker connected to each other via a gas pipeline. First, check the status of each valve on the dry ice maker's panel. The purge valve should be in the open position, and the gas phase valve, liquid phase valve, and vent valve should all be in the closed position. Then, open the CO2 storage tank's main vent valve and the dry ice maker's gas phase valve in sequence, and confirm that the pressure indicated on the gas phase valve pressure gauge is consistent with the pressure indicated on the CO2 storage tank's pressure gauge. B. Open the vent valve on the dry ice machine, exhaust all the air, and then close the vent valve on the dry ice machine; open the gas phase valve of the dry ice machine, and confirm that the pressure displayed by the pressure gauge on the gas phase valve and the pressure displayed by the pressure gauge on the liquid phase valve are both between 1.2 and 2.1 MPa; C. Start the dry ice making machine to produce dry ice pellets at a speed of 60 kg / h. After a certain period of time, transfer the prepared dry ice pellets to a dry ice storage box with insulation function for future use; In sub-step A of this step, the pressure displayed on the pressure gauge on the gas phase valve is called the gas phase pressure, and the gas phase pressure should be controlled between 0.9 and 2.1 MPa; In sub-step A of this step, if the gas phase pressure is within a ±8% floating range compared to the CO2 storage tank pressure, the two pressures are considered to be consistent; In sub-step B of this procedure, the pressure displayed on the pressure gauge on the liquid phase valve is called the liquid phase pressure; S04, device initialization: A. Close valve X on the abrasive outlet of the steel ball cleaning chamber, open valve Y on the negative pressure interface of the dust buffer chamber, and start the negative pressure vacuum cleaner. On the one hand, the negative pressure is transmitted to the dust hood A through the pipeline, dust buffer chamber, and collection pipe A in sequence. On the other hand, the negative pressure is transmitted to the dust hood B through the pipeline, dust buffer chamber, and collection pipe B in sequence. B, turn on the power supply of the heating wire to preheat the outer wall and inner cavity of the discharge device; put the abrasive to be purified into the dirty material bin B; put the prepared dry ice particles into the dry ice cleaning machine; S05, abrasive primary filtration: A, controls the feeding speed of the dirty material bin B, so that the abrasive to be purified is continuously fed into the inner cavity of the feeding device through the feed port A, and then moves to the discharge port A of the feeding device in accordance with the inclination angle of the feeding device and driven by the spiral blades inside the feeding device; during the movement of the abrasive, dust particles smaller than the abrasive are discharged through the dust outlet A of the feeding device, and then are received by the port A of the dust collecting hood A and enter the inner cavity of the dust collecting hood A; the debris with a relatively large specific gravity in the abrasive falls under the action of its own gravity, and is discharged from the port C at the lower end of the dust collecting hood A, and then enters the inner cavity of the debris collecting chamber through the collection pipe C and the debris inlet of the debris collecting chamber; the debris with a relatively small specific gravity in the abrasive is discharged from the port B in the middle of the dust collecting hood A under the action of negative pressure, and then passes through the collection pipe A, the dust buffer chamber and the pipeline in sequence and enters the negative pressure vacuum cleaner; At this point, the initial filtration of the abrasive is completed; B. The abrasive that has completed the preliminary filtration is discharged through the discharge port A of the feeding device, and then enters the inner cavity of the steel ball cleaning chamber through the abrasive inlet of the steel ball cleaning chamber; S06, abrasive cleaning: A. Open the valve on the pipeline between the air compressor, air tank, and freeze dryer, allowing the pressurized airflow output by the freeze dryer to continuously enter the dry ice cleaning machine, providing the power for the dry ice particles to flow. Then, start the dry ice cleaning machine, causing the pressurized airflow to spray dry ice particles from the spray gun, striking the abrasive in the inner cavity of the steel ball cleaning chamber. On the one hand, under the continuous impact of the airflow and dry ice, the abrasive collides with each other in the inner cavity of the steel ball cleaning chamber, and the collision process strips away the dirt containing radionuclides on the abrasive surface. On the other hand, there is a temperature difference between the dry ice and the abrasive. When the dry ice collides with the abrasive, the physical reaction based on the temperature difference causes the different substances to shrink at different rates, thereby stripping away the dirt containing radionuclides on the abrasive surface. During the cleaning process, the dirt containing radioactive nuclides peeled off from the surface of the abrasive is discharged through the dust outlet B, and then is contained by the port D of the dust hood B and enters the inner cavity of the dust hood B. The heavier part of the dirt falls under the action of its own gravity and is discharged from the port F at the bottom of the dust hood B, and then enters the inner cavity of the debris collection chamber through the collection pipe D and the debris inlet of the debris collection chamber. The lighter part of the dirt is discharged from the port E in the middle of the dust hood B under the action of negative pressure, and then enters and is trapped in the negative pressure vacuum cleaner through the collection pipe B, the dust inlet of the dust buffer chamber, the negative pressure interface and pipeline of the dust buffer chamber. C. After cleaning for a certain period of time, open valve X on the steel ball cleaning chamber and valve Z on the buffer hopper, so that the abrasive in the inner cavity of the steel ball cleaning chamber is discharged through the abrasive outlet at the lower end of the steel ball cleaning chamber and then enters the buffer hopper through the pipeline; In this step, the dry ice cleaning machine sprays dry ice at a rate of 30-200 kg / h and an air flow rate of 1.8-3.5 m 3 / min; S07, abrasive drying: The feeding speed of the buffer hopper is controlled so that the cleaned abrasive is continuously input into the inner cavity of the discharge device through the feed port B, and then moves toward the discharge port B of the discharge device in accordance with the inclination angle of the discharge device and driven by the spiral blades inside the discharge device. During the movement of the abrasive, the abrasive is heated by the preheated discharge device to achieve drying, and the water vapor generated by the evaporation of the abrasive is discharged to the outside through the water vapor outlet of the discharge device. The dried abrasive enters the clean material bin B for temporary storage.

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