Method for estimating radioactive release amount in radioactive metal waste conditioning process

Abstract

This invention discloses a method for estimating radioactive release during the preparation of radioactive metal waste, comprising the following steps: (1) conducting gamma dose rate surveys and delineating the distribution of radioactive pollution in the radioactive source area; (2) setting up monitoring points in the radioactive metal waste areas with different pollution levels, and calculating the radioactive residue in the metal waste based on the monitoring data; (3) calculating the total release of each nuclide in the metal waste based on the above-mentioned radioactive residue in the metal waste and the obtained concentration data of radionuclides in the metal waste. By conducting gamma dose rate surveys and delineating the distribution of radioactive pollution in the radioactive source area; setting up monitoring points in the delineated areas to obtain the radioactive residue in the metal waste; and calculating the total release of each nuclide using formulas, the process is simple, easy to operate, and can obtain effective data on the total release of nuclides, providing data support for the preparation of radioactive contaminated metal waste and supporting the assessment of the dose caused by contaminated metal waste to the public.

Description

Technical Field

[0001] This invention belongs to the field of radiation protection technology, specifically relating to a method for estimating radioactive release during the preparation of radioactive metal waste. Background Technology

[0002] With the rapid development of my country's nuclear energy industry, while ensuring national security and promoting national economic growth, certain safety hazards have also arisen. In the rapid development of uranium mining and metallurgy, nuclear fuel cycle facilities, and nuclear power plants in recent decades, radioactive contamination of equipment, pipelines, valves, and other metallic waste has inevitably occurred. Due to insufficient attention paid to the treatment and disposal of radioactive solid waste in the early stages of my country's nuclear industry, and because radioactive waste contains or is contaminated with radionuclides, with concentrations or specific activities exceeding the cleanliness and decontamination levels stipulated by national regulatory authorities, and because various nuclear facilities generally exhibit irregularities in solid waste management—often classifying, packaging, and compacting radioactive solids for preparation—the release of radioactive source terms from radioactive metallic contaminated waste during these processes is unknown, posing a safety hazard of pollution spread to the environment and public health. Therefore, a scientifically sound and reasonable estimation of the radioactive source term release from radioactive metallic contaminated waste during the preparation process is extremely important. Summary of the Invention

[0003] In view of the above-mentioned technical problems existing in the prior art, the purpose of the present invention is to provide a method for effectively estimating the source term of radioactive metal contaminated waste during the preparation process.

[0004] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: a method for estimating radioactive release during the preparation of radioactive metal waste, comprising the following steps:

[0005] (1) Conduct gamma dose rate surveys and delineate the distribution of radioactive contamination in the radioactive contamination source area;

[0006] (2) Set up monitoring points in the radioactive metal waste areas with different pollution levels, and calculate the amount of radioactive metal waste remaining based on the monitoring data;

[0007] (3) The total amount of each nuclide released in the metal waste was calculated based on the above-mentioned amount of radioactive residue in the metal waste and the concentration data of radionuclides in the metal waste.

[0008] Furthermore, in step (1), the accumulated metal waste is subjected to gamma dose rate survey to identify the contaminated area, and the identified contaminated area is divided.

[0009] Further, in step (1), the region where the γ dose rate of the γ dose rate survey result is more than ten times the background level is the first level; the region where the γ dose rate of the γ dose rate survey result is 5 to 10 times the background level is the second level; and the region where the γ dose rate of the γ dose rate survey result is 1 to 5 times the background level is the third level.

[0010] Furthermore, in step (2), based on the distribution of radioactive contamination in step (1), grids are set up in different division areas to monitor the contamination on the inner and outer surfaces of the waste entering the house.

[0011] Furthermore, in step (2), an area of ​​100 cm² is established in the first type of horizontal region. 2 A grid; an area of ​​1m² is established in the second type of horizontal region. 2 The grid is constructed; points are randomly distributed in the third type of horizontal region; samples are taken from the grid in the region to monitor radioactive metal surface contamination and measure the thickness and area of ​​metal waste. The maximum monitoring result of surface contamination is combined with the metal density to calculate the activity.

[0012] Furthermore, in step (2), in the case of contamination on the inner surface of the metal waste, the radioactive source term is estimated by taking the contamination level of the inner and outer surfaces as being equivalent to half the volume of the same type of metal waste in the area.

[0013] Furthermore, based on the total release of each nuclide in the metal waste obtained in step (3), the metal waste is subjected to coating and solidification treatment respectively.

[0014] Furthermore, the metal waste is processed into granular waste and wrapped in shells of varying thicknesses; it is placed in a packaging barrel, fixed with cement mortar, and then the metal packaging barrel is covered and sealed.

[0015] Furthermore, the thickness of the shell layer is 0.5–9 mm.

[0016] The beneficial effects of the technical solution of this invention are that the method for estimating the amount of radioactive release during the preparation of radioactive metal waste involves conducting gamma dose rate surveys and delineating the distribution of radioactive pollution in the radioactive pollution source area; setting up monitoring points in the delineated area to obtain the amount of radioactive residue in the metal waste; and using formulas to calculate the total release of each nuclide. The process is simple, easy to operate, and can obtain effective data on the total release of nuclides, providing data support for the preparation of radioactive contaminated metal waste and supporting the dose assessment of contaminated metal waste to the public. Attached Figure Description

[0017] Figure 1 This is a flowchart of the method for estimating radioactive release during the preparation of radioactive metal waste according to an embodiment of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] See attached document Figure 1 The method for estimating radioactive release during the preparation of radioactive metal waste includes the following steps:

[0020] (1) Conduct gamma dose rate surveys and delineate the distribution of radioactive contamination in the radioactive contamination source area;

[0021] (2) Set up monitoring points in the radioactive metal waste areas with different pollution levels, and calculate the amount of radioactive metal waste remaining based on the monitoring data;

[0022] (3) The total amount of each nuclide released in the metal waste was calculated based on the above-mentioned amount of radioactive residue in the metal waste and the concentration data of radionuclides in the metal waste.

[0023] Preferably, in step (1), gamma dose rate monitoring is performed on the accumulated metal waste to identify contaminated areas, and the identified contaminated areas are divided. The higher the concentration of residual radioactive activity of radionuclides in the metal waste, the higher the monitored gamma dose rate. The area where the gamma dose rate is more than ten times the background level is classified as Class I; the area where the gamma dose rate is 5 to 10 times the background level is classified as Class II; and the area where the gamma dose rate is 1 to 5 times the background level is classified as Class III. Class I areas belong to the areas where radioactive metal waste accidents or time periods have occurred, and the radioactive concentration in these areas is high. The division of Class I, Class II, and Class III areas is determined based on the monitoring results of the gamma dose rate monitoring instrument. Before the gamma dose rate monitoring instrument identifies the areas, relevant information can be consulted to assist in the classification of the areas.

[0024] The baseline level was obtained by monitoring in uncontaminated areas.

[0025] Preferably, in step (2), according to the distribution of radioactive contamination in step (1), grids are set up in different division areas to monitor the contamination on the inner and outer surfaces of the metal waste.

[0026] Preferably, in step (2), an area of ​​100 cm² is set in the first type of horizontal region. 2 A grid; an area of ​​1m² is established in the second type of horizontal region. 2 The grid is constructed; random sampling points are placed in the third type of horizontal area; radioactive metal surface contamination is sampled and monitored in the grid of the area, and the thickness and area of ​​metal waste are measured. The maximum monitoring result of surface contamination is combined with the metal density to calculate the activity. The total annual radioactive release A0 is obtained based on the activity data and related volatile factors.

[0027] Different types of metal equipment waste are classified, and several or a dozen representative pieces of metal equipment are selected for each category. Their surface contamination data are measured. This data is the representative surface contamination data. The radioactivity of the surface contamination of the metal waste can be obtained by multiplying the surface contamination data per unit area by the outer surface area of ​​the metal part.

[0028] Preferably, in step (2), when the inner surface of the metal waste is contaminated, the radioactive source term is estimated by taking the contamination level of the inner and outer surfaces as being equal to half the volume of the same type of metal waste in the area.

[0029] Preferably, in step (3), the total amount of each nuclide released from the metal waste is calculated using formula (1).

[0030] A=A0×M×Y0×N / (D×Y) (1)

[0031] Wherein, A—the total annual release of a certain nuclide (Bq / a); A0—the total annual release of radioactivity (Bq / a); M—the mass percentage of a certain nuclide; Y0—the atomic weight of a certain nuclide; N—the specific activity of a certain nuclide (Bq / a); D—the specific activity of the pollution source (Bq / a); Y—the atomic weight of the pollution source.

[0032] Preferably, the metal waste is processed to obtain granular waste. According to the total release of different nuclides of the metal waste obtained in step (3), the granular waste is wrapped in shells of different thicknesses and placed in a shielding material packaging barrel. Cement mortar is used to pour and fix the inside of the barrel, and then the packaging barrel is covered and sealed.

[0033] Preferably, the thickness of the shell layer is set to 8.5–9.5 mm, 5.5–7.5 mm, and 0.8–2.5 mm for the first, second, and third horizontal regions, respectively. This ensures a low leaching rate of the encapsulated metal waste.

[0034] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention is also intended to include these modifications and variations.

Claims

1. A method for estimating radioactive release during the preparation of radioactive metal waste, characterized by: Includes the following steps: (1) Conduct gamma dose rate surveys and delineate the distribution of radioactive contamination in the radioactive contamination source area; (2) Set up monitoring points in the radioactive metal waste areas with different pollution levels, and calculate the amount of radioactive metal waste remaining based on the monitoring data; (3) The total amount of each nuclide released in the metal waste was calculated based on the above-mentioned amount of radioactive residue in the metal waste and the concentration data of radionuclides in the metal waste. In step (3), the total release amount of each nuclide in the metal waste is calculated using a formula. A = A0 × M × Y0 × N / (D × Y) Among them, A —Annual total release of a certain nuclide Bq / a; A0—Annual total release of radioactivity Bq / a; M—Mass percentage of a certain nuclide; Y0—Atomic weight of a certain nuclide; N—Specific activity of a certain nuclide Bq / a; D—Specific activity of the pollution source Bq / a; Y—Atomic weight of the pollution source.

2. The method for estimating radioactive release during the preparation of radioactive metal waste according to claim 1, characterized in that: In step (1), the accumulated metal waste is subjected to gamma dose rate survey to identify the contaminated area, and the identified contaminated area is divided.

3. The method for estimating radioactive release during the preparation of radioactive metal waste according to claim 1, characterized in that: In step (1), the region where the γ dose rate of the γ dose rate survey result is more than ten times the background level is the first level; the region where the γ dose rate of the γ dose rate survey result is 5 to 10 times the background level is the second level; and the region where the γ dose rate of the γ dose rate survey result is greater than 1 time and less than 5 times the background level is the third level.

4. The method for estimating radioactive release during the preparation of radioactive metal waste according to claim 1, characterized in that: In step (2), based on the distribution of radioactive contamination in step (1), grids are set up in different division areas to monitor the contamination on the inner and outer surfaces of metal waste.

5. The method for estimating radioactive release during the preparation of radioactive metal waste according to claim 3, characterized in that: In step (2), an area of ​​100cm² is established in the first type of horizontal region. 2 A grid; an area of ​​1m² is established in the second type of horizontal region. 2 The grid; points are randomly placed in the third type of horizontal region.

6. The method for estimating radioactive release during the preparation of radioactive metal waste according to claim 5, characterized in that: Within the grid, samples were taken to monitor radioactive metal surface contamination and to measure the thickness and area of ​​metal waste. The maximum monitoring result of surface contamination was combined with the metal density to calculate the activity.

7. The method for estimating radioactive release during the preparation of radioactive metal waste according to claim 1, characterized in that: In step (2), when the inner surface of the metal waste is contaminated, the radioactive source term is estimated by taking the contamination level of the inner and outer surfaces as half the volume of the same type of metal waste in the area.

8. The method for estimating radioactive release during the preparation of radioactive metal waste according to claim 1, characterized in that: The metal waste is processed to obtain granular waste. According to the total release of different nuclides of the metal waste obtained in step (3), the granular waste is wrapped in shells of different thicknesses and placed in a shielding material packaging barrel. Cement mortar is used to pour and fix the inside of the barrel, and then the packaging barrel is covered and sealed.

9. The method for estimating radioactive release during the preparation of radioactive metal waste according to claim 8, characterized in that: The thickness of the shell is set to 8.5~9.5mm, 5.5~7.5mm, and 0.8~2.5mm for the first type of horizontal region, the second type of horizontal region, and the third type of horizontal region, respectively.

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