CN114360758A - Decontamination process for radioactive source tank - Google Patents
Decontamination process for radioactive source tank Download PDFInfo
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- CN114360758A CN114360758A CN202111663869.0A CN202111663869A CN114360758A CN 114360758 A CN114360758 A CN 114360758A CN 202111663869 A CN202111663869 A CN 202111663869A CN 114360758 A CN114360758 A CN 114360758A
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Abstract
The invention discloses a decontamination process for a radioactive source tank, which relates to the technical field of radioactive source tank treatment, and comprises the following steps: (1) the source tanks are divided into two types according to the pollution level of the outer surface of the source tank, wherein the pollution level of the outer surface is more than 40Bq/cm2The high-pollution source tank has the outer surface pollution level of less than or equal to 40Bq/cm2The low-pollution source tank; (2) cleaning and decontaminating by high-pressure water: the high-pollution source tank is washed and decontaminated by adopting closed high-pressure water, and the low-pollution source tank is washed and decontaminated by adopting open high-pressure water; (3) opening a hole on the part of the decontaminated source tank, wherein the hole is used for the lead in the interlayer to flow out after being melted; (4) mounting the source tank with the hole on a hot melting lead extraction device; (5) heating to 350-370 ℃ to melt lead, separating the lead from the source tank body through the opening in the step (3), introducing lead liquid into a container, and carrying out ingot casting on the lead liquid according to metallurgical specifications; (6) and (5) measuring the pollution level of the lead ingot.
Description
Technical Field
The invention relates to the technical field of radioactive source tank treatment, in particular to a radioactive source tank decontamination process.
Background
With the rapid development of the nuclear industry, radioactive sources are widely used in various fields such as nuclear energy, aerospace, medical treatment, scientific research and the like. However, the radioactive source has strong radioactivity, and a radioactive source tank (hereinafter referred to as a source tank) is required to be used as a shielding container in the storage and transportation processes of the radioactive source. The source tank is mainly composed of an outer container (generally made of iron-based materials), a sleeve, a lining material (generally made of lead) in the container and the like. The source tank is inevitably damaged and radioactive-contaminated during the use process, so that the source tank cannot be used continuously. Decontamination of spent radioactive source canisters reduces the amount of radioactive waste or waste grade and provides for recycling of its components (e.g., lead, outside containers).
A batch of source tanks are temporarily stored in the eight-two-one plant of the middle nuclear, and the geometric structure of the source tanks is complex. The outer layer of the source canister has been damaged and radioactively contaminated to varying degrees, the inner sleeve has a high level of radioactivity due to the contamination of the radioactive source and cannot be used further, but the lead (in the interlayer) as the shielding material has a low probability of being contaminated. The waste source tank belongs to radioactive pollution metal, and how to properly dispose is a considerable problem.
At present, the treatment method of the waste source tank at home and abroad mainly adopts the methods of landfill treatment, surface decontamination, smelting decontamination and the like to treat radioactive contamination metals.
If the landfill treatment method is adopted, the radioactive pollution metal is subjected to overpressure, and landfill is carried out after solidification. However, in order to reduce the potential risk to the environment of landfill disposal, long-term monitoring is required, so that disposal cost is high, and the radioactive waste minimization principle is not satisfied, which is a waste of resources.
If a surface decontamination method is adopted, the surface contamination of parts with simple geometric shapes is effective, and only the radioactive surface contamination of the outer surface of the source tank (with rust scale and paint) can be removed, for example, a lead source tank with a regular shape is decontaminated by dry ice spraying in a Chinese courtyard, but the method cannot decontaminate the source tank with a complicated geometric structure which is similar to the temporary storage in a plant with eight or two cores.
Finally, only a smelting decontamination method is left, namely, in the decontamination process, nuclides are redistributed to enter gas phase or molten slag, metal is cast into ingots and reused, for example, a treatment scheme of cutting, smelting and re-casting a source tank is provided in patent application with publication number CN103811091B and a high-level uranium-contaminated carbon steel or stainless steel smelting decontamination process, but smelting decontamination is adopted, in order to melt an outer cladding (generally made of an iron-based material) of the source tank, the temperature needs to be raised to about 1500-.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a decontamination process for a radioactive source tank, which aims to solve the technical problem that the conventional source tank treatment technology is difficult to treat the source tank with a complicated geometric structure when the radioactive source tank is treated.
The technical scheme adopted by the invention is as follows:
a decontamination process for a radioactive source tank comprises the following steps:
(1) the source tanks are divided into two types according to the pollution level of the outer surface of the source tank, wherein the pollution level of the outer surface is more than 40Bq/cm2The high-pollution source tank has the outer surface pollution level of less than or equal to 40Bq/cm2The low-pollution source tank;
(2) cleaning and decontaminating by high-pressure water: the high-pollution source tank is washed and decontaminated by adopting closed high-pressure water, and the low-pollution source tank is washed and decontaminated by adopting open high-pressure water;
(3) opening a hole on the part of the decontaminated source tank, wherein the hole is used for the lead in the interlayer to flow out after being melted;
(4) mounting the source tank with the hole on a hot melting lead extraction device;
(5) heating to 350-370 ℃ to melt lead, separating the lead from the source tank body through the opening in the step (3), introducing lead liquid into a container, and carrying out ingot casting on the lead liquid according to metallurgical specifications;
(6) and (5) measuring the pollution level of the lead ingot.
Preferably, the pressure of the high-pressure water washing in the step (2) is 110-120MPa, and the washing time is 6-12 min.
Preferably, the hole formed in the step (3) is positioned at a position where the hot-melt lead in the source tank is easy to completely flow out, and is positioned at the bottom when being heated, so that a closed cavity is not formed when the lead is hot-melted, and the lead in the source tank can completely flow out after being melted as much as possible; and (4) after the radioactive waste generated by the open pore is detected, performing decontamination treatment by adopting other processes.
Preferably, the heating source of the hot melting lead extraction device in the step (4) is a natural gas fierce furnace.
In summary, compared with the prior art, the invention has the following advantages and beneficial effects:
1. the invention utilizes the characteristic that the melting point difference between lead (the melting point is 327.5 ℃) and the outer cladding (generally an iron-based material, the melting point is about 1500-;
2. the invention combines the advantages of surface decontamination and smelting decontamination, abandons the defects of two treatment methods, provides a new idea for source tank treatment, and can ensure that the decontamination process of the source tank can ensure that the outer surface of the source tank is clean and controllable, and the internal lead can be recycled and reused in a certain range after hot melting separation;
3. the source tank decontamination process provided by the invention reduces the pressure of lead mineral resources to a certain extent, achieves the purpose of classification treatment of solid wastes, obviously reduces the decontamination treatment, preparation and disposal costs of the source tank, and meets the principle of minimizing radioactive wastes.
Drawings
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
fig. 1 is a process flow diagram of a decontamination process provided by the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
As shown in fig. 1, the present invention provides a process flow diagram of a source tank decontamination process, which comprises the following steps:
(1) performing source item investigation on the source tank to determine its outer surface contamination level and contamination status, and classifying the source tank into two types according to its outer surface contamination level, one type having an outer surface contamination level of more than 40Bq/cm2The high-pollution source tank has the outer surface pollution level of less than or equal to 40Bq/cm2The low-pollution source tank; (ii) a
(2) Cleaning and decontaminating by high-pressure water: the high-pollution source tank is washed and decontaminated by adopting closed high-pressure water, the low-pollution source tank is washed and decontaminated by adopting open high-pressure water, the high-pressure water washing pressure is 110-120MPa, and the washing time is 6-12min (depending on the volume of the source tank);
(3) utilize compressed air to weather the source jar, carry out the trompil to the source jar part: the method mainly comprises the steps of perforating from a position where hot molten lead in a source tank easily and completely flows out, and performing decontamination treatment by adopting other processes after detecting radioactive waste generated by perforating;
(4) mounting the source tank with the hole on a hot melting lead extraction device, and placing the hole at the bottom;
(5) heating to enable the temperature to reach 350-370 ℃, so that the lead is melted and separated from the source tank body, enters a container, and is cast into ingots according to metallurgical specifications;
(6) and (5) measuring the pollution level of the lead ingot.
Example 1
The source item of the source tank No. 1 is measured, the weight is 1244Kg, the alpha surface pollution level is not detected, and the beta surface pollution level is 31.6Bq/cm2And part of paint on the surface of the source tank falls off. Due to the surface pollution level of less than 40Bq/cm2Thus, therefore, it isAnd (3) washing and decontaminating by adopting open high-pressure water, wherein the high-pressure water washing pressure is 110Mpa, and the washing time is 7 min. The source tank is dried by compressed air, holes are formed in the bottom of the source tank, and radioactive wastes generated by the holes are placed into the steel drum to be treated after being detected. And (3) installing the source tank No. 1 with the hole in a hot melting lead extraction device using an industrial natural gas vigorous furnace as a heat source, controlling the temperature of the tank body to be 360-370 ℃, heating for 2h, pouring lead liquid into a container after the lead is completely melted and separated from the source tank body, and determining the pollution level of the lead ingot according to the metallurgical specification.
After the treatment by the process, the beta-polluted water on the surface of the source tank is reduced to 0.3Bq/cm on average2The decontamination effect is obvious. The weight of the lead ingot after hot melting is 895Kg, and the surface pollution level is 0.06Bq/cm2And the method can be completely used for reproducing and manufacturing the shielding layer.
Example 2
The weight of the source can item No. 2 is determined to be 2056Kg, the alpha surface pollution level is not detected, and the beta surface pollution level is 56.1Bq/cm2And the paint on the surface of the source tank falls off more. Due to the surface pollution level being more than 40Bq/cm2Therefore, closed high-pressure water is adopted for washing and decontaminating, the high-pressure water washing pressure is 120Mpa, and the washing time is 12 min. The source tank is dried by compressed air, holes are formed in the bottom of the source tank, and radioactive wastes generated by the holes are placed into the steel drum to be treated after being detected. And (3) installing the perforated source tank No. 2 in a hot melting lead extraction device using an industrial natural gas high-speed furnace as a heat source, controlling the temperature of the tank body to be 360-370 ℃, heating for 4.5 hours, and after lead is completely melted and separated from the source tank body to enter a container, carrying out ingot casting on lead liquid according to metallurgical specifications, and determining the pollution level of the lead ingot.
After the treatment by the process, the beta-polluted water on the surface of the source tank is reduced to 0.4Bq/cm on average2The decontamination effect is obvious. The lead after hot melting weighs 1432Kg and the surface pollution level is 0.04Bq/cm2And the method can be completely used for reproducing and manufacturing the shielding layer.
The above-mentioned embodiments only express the specific embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present application. It should be noted that, for those skilled in the art, without departing from the technical idea of the present application, several changes and modifications can be made, which are all within the protection scope of the present application.
Claims (4)
1. A decontamination process for a radioactive source tank is characterized by comprising the following steps:
(1) the source tanks are divided into two types according to the pollution level of the outer surface of the source tank, wherein the pollution level of the outer surface is more than 40Bq/cm2The high-pollution source tank has the outer surface pollution level of less than or equal to 40Bq/cm2The low-pollution source tank;
(2) cleaning and decontaminating by high-pressure water: the high-pollution source tank is washed and decontaminated by adopting closed high-pressure water, and the low-pollution source tank is washed and decontaminated by adopting open high-pressure water;
(3) opening a hole on the part of the decontaminated source tank, wherein the hole is used for the lead in the interlayer to flow out after being melted;
(4) mounting the source tank with the hole on a hot melting lead extraction device;
(5) heating to 350-370 ℃ to melt lead, separating the lead from the source tank body through the opening in the step (3), introducing lead liquid into a container, and carrying out ingot casting on the lead liquid according to metallurgical specifications;
(6) and (5) measuring the pollution level of the lead ingot.
2. The decontamination process of a radioactive source canister as claimed in claim 1, wherein the high pressure water washing pressure in step (2) is 110-120MPa, and the washing time is 6-12 min.
3. The radioactive source canister decontamination process of claim 1, wherein the opening of step (3) is located at the bottom of the source canister.
4. The radioactive source canister decontamination process of claim 1, wherein the heat source of the hot melting lead extraction device of step (4) is a natural gas flash furnace.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111663869.0A CN114360758A (en) | 2021-12-31 | 2021-12-31 | Decontamination process for radioactive source tank |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111663869.0A CN114360758A (en) | 2021-12-31 | 2021-12-31 | Decontamination process for radioactive source tank |
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| CN114360758A true CN114360758A (en) | 2022-04-15 |
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| CN202111663869.0A Pending CN114360758A (en) | 2021-12-31 | 2021-12-31 | Decontamination process for radioactive source tank |
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