Method for evaluating residual radioactivity of decommissioned end-of-life buildings

Abstract

This invention provides a method for evaluating the residual radioactivity of decommissioned buildings in their final state. The method includes: obtaining the types and dose constraints of radionuclides within the target building; measuring the area of ​​each measurement surface within the target building; establishing a radiation dose calculation model; substituting the assumed activity concentration value and the area of ​​each measurement surface into the radiation dose calculation model to calculate a first assumed maximum effective dose value; calculating the sum of all first assumed maximum effective dose values ​​to obtain a total assumed maximum effective dose value; calculating the permissible residual activity concentration value of each type of radionuclide; and obtaining the evaluation result based on the actual residual activity concentration value and the permissible residual activity concentration value of each type of radionuclide. This residual radioactivity evaluation method enables the calculation of the permissible residual activity concentration value of a building, thereby determining whether the radiation level of a decommissioned target after construction meets the radiation safety requirements for the population.

Description

Technical Field

[0001] This invention relates to the field of residual radioactivity assessment technology, specifically to a method for evaluating the residual radioactivity of decommissioned buildings in their final state. Background Technology

[0002] As nuclear power plants and other nuclear facilities reach the end of their designed lifespan or complete their intended tasks, they enter the decommissioning phase, and the focus of work shifts from the operation of nuclear facilities to their decommissioning and environmental remediation.

[0003] During the long-term operation of a nuclear facility, radioactive nuclides can escape into the building structure and generate radioactivity.

[0004] The area where the nuclear facility is located will be reused, and the original building structures may be fully or partially preserved as decommissioned final-state buildings of the nuclear facility. The radioactivity produced by radionuclides in the original building structures of the decommissioned final-state buildings will affect personnel entering the decommissioned final-state buildings. Summary of the Invention

[0005] In view of this, embodiments of the present invention aim to provide an evaluation method capable of assessing the radioactivity of nuclides remaining in the soil at the end of the decommissioning of nuclear facilities.

[0006] To achieve the above objectives, the technical solution of this invention is implemented as follows:

[0007] This invention provides a method for evaluating the residual radioactivity of decommissioned buildings in their final state. The method includes:

[0008] Obtain the types and dose constraints of radionuclides inside the target building;

[0009] Measure the area of ​​each measuring surface within the target building;

[0010] Establish a calculation model for the radiation dose of various radionuclides corresponding to the area;

[0011] Substitute the assumed activity concentration values ​​of various radionuclides and the area of ​​each of the measurement surfaces into the irradiation dose calculation model to calculate the first assumed maximum effective dose value of each radionuclide on each of the measurement surfaces.

[0012] The sum of the first assumed maximum effective dose values ​​of each of the measurement surfaces is calculated to obtain the total assumed maximum effective dose value. The permissible residual activity concentration values ​​of various radionuclides are calculated based on the assumed activity concentration value, the total assumed maximum effective dose value and the dose constraint value.

[0013] After the completion of the decommissioning final state target construction, the actual residual activity concentration values ​​of various radionuclides inside the target are obtained, and the evaluation results are obtained based on the actual residual activity concentration values ​​and the allowable residual activity concentration values ​​of various radionuclides.

[0014] In some embodiments, obtaining the dose constraint value specifically includes:

[0015] The dose constraint value is determined based on the type of the decommissioned final state target to be constructed in the target area.

[0016] In some embodiments, the measurement of the area of ​​each measuring surface within the target building specifically includes:

[0017] The target building is a reactor building, and the internal space of the reactor building is a cube. The measuring surfaces are two opposite planes along a first direction, two opposite planes along a second direction, and two opposite planes along a third direction in the internal space of the reactor building. The first direction, the second direction, and the third direction are orthogonal to each other. The area of ​​each of the measuring surfaces is measured.

[0018] In some embodiments, before establishing the radiation dose calculation model corresponding to various radionuclides and area, the residual radioactivity evaluation method further includes:

[0019] Determine the type of irradiation pathway;

[0020] In the radiation dose calculation model, the total effective dose value is the sum of the effective dose values ​​generated by each of the irradiation pathways, and the effective dose value generated by each of the irradiation pathways is related to the activity concentration of the radionuclide on the measurement surface.

[0021] In some embodiments, the establishment of radiation dose calculation models corresponding to various radionuclides and areas specifically includes:

[0022] Establish a calculation model for the radiation dose of various radionuclides corresponding to their volume;

[0023] The step of substituting the assumed activity concentration values ​​of various radionuclides and the area of ​​each of the measurement surfaces into the radiation dose calculation model specifically includes:

[0024] Establish a reference volume source corresponding to each of the measurement surfaces. The projected area of ​​the reference volume source perpendicular to its thickness direction is the same as the area of ​​the corresponding measurement surface. The thickness of the reference volume source does not exceed a preset thickness.

[0025] The assumed activity concentration values ​​of various radionuclides and the volumes of each of the aforementioned reference volume sources are substituted into the radiation dose calculation model.

[0026] In some embodiments, the irradiation pathway is external irradiation, and the irradiation dose calculation model is a function of the effective dose value of the external irradiation with respect to the irradiation duration, the activity concentration value of the radionuclide, and the distance of the person relative to the measurement surface.

[0027] In some embodiments, the preset thickness does not exceed 0.01 mm.

[0028] In some embodiments, the assumed activity concentration value, the total assumed maximum effective dose value, the dose constraint value, and the permissible residual activity concentration value are related as follows:

[0029] C H / E T =C L / E L

[0030] Among them, C H E represents the assumed activity concentration value. T C is the total assumed maximum effective dose value. R E represents the permissible residual activity concentration value. L This refers to the dose constraint value.

[0031] In some embodiments, obtaining the evaluation results based on the actual residual activity concentration values ​​and the permissible residual activity concentration values ​​of various radionuclides specifically includes:

[0032] The actual residual activity concentration value and the allowable residual activity concentration value have the following relationship:

[0033]

[0034] Among them, C Ai C represents the actual residual activity concentration of radionuclide i in the soil. Ri The permissible residual activity concentration value of radionuclide i in the building, and n is the number of types of radionuclides in the soil.

[0035] In some embodiments, the types of radionuclides obtained from the interior of the target building specifically include:

[0036] Determine multiple initial sampling locations on the interior walls of the target building;

[0037] First samples are obtained by wiping and sampling at each of the first sampling locations;

[0038] Each of the first samples is tested to obtain the types of radionuclides.

[0039] The residual radioactivity evaluation method in this embodiment of the invention establishes an irradiation dose calculation model to calculate the allowable residual activity concentration value inside the decommissioned final-state building. Then, based on the obtained allowable residual activity concentration value, it can be determined whether the radiation level of the decommissioned final-state building after construction meets the radiation safety requirements for the population. This enables the evaluation of the remediation effect of radioactive contaminated sites and provides a reliable basis for the radiation protection of the population. Attached Figure Description

[0040] Figure 1 This is a schematic diagram illustrating the steps of the method for evaluating the residual radioactivity of decommissioned buildings of nuclear facilities in an embodiment of the present invention. Detailed Implementation

[0041] It should be noted that, in the absence of conflict, the embodiments and technical features in the embodiments of the present invention can be combined with each other. The detailed description in the specific embodiments should be understood as an explanation of the purpose of the embodiments of the present invention and should not be regarded as an improper limitation on the embodiments of the present invention.

[0042] This invention provides a method for evaluating the residual radioactivity of decommissioned buildings in their final state. (See attached document.) Figure 1 The method for evaluating residual radioactivity specifically includes:

[0043] S10: Obtain the types and dose constraints of radionuclides inside the target building.

[0044] The target building refers to the building structure that needs to be retained and converted to other uses after the nuclear facility is decommissioned.

[0045] Radioactive nuclides, also called unstable nuclides, are atomic nuclei that are unstable and can spontaneously emit rays such as alpha rays and beta rays, and decay into stable nuclides.

[0046] The specific source of the radionuclides in the target building can be either the radionuclides originally present in the nuclear facility or new types of radionuclides obtained after decay of the original radionuclides in the nuclear facility.

[0047] It is understandable that different types of radionuclides have different chemical properties and radiation levels. By identifying the types of radionuclides inside the target building, it is possible to adopt appropriate cleaning, decontamination and other purification measures in a targeted manner, and to facilitate the subsequent calculation of the permissible residual activity concentration values ​​of different types of radionuclides.

[0048] It is understandable that the type of radioactive nuclide inside the target building can be one or more.

[0049] A dose constraint is a predetermined limit on the individual dose that a radiation source may cause, used as a constraint for protection and safety optimization of the radiation source under consideration. For public exposure, a dose constraint is the upper limit on the annual dose received by members of the public from the planned operation of a controlled radiation source. The exposure referred to by a dose constraint is the sum of the annual doses received by any critical population through all exposure pathways.

[0050] S20: Measure the area of ​​each measuring surface within the target building.

[0051] It is understandable that during the operation of a nuclear facility, radioactive nuclides produced may drift onto the walls of the target building, thereby making the walls radioactive.

[0052] The measurement surface is the surface within the target building that encloses and forms various spaces.

[0053] It is understandable that the radiation dose produced by a radionuclide in a single measurement surface is related to the size of its area and the radiation dose per unit area.

[0054] S30: Establish a calculation model for the radiation dose of various radionuclides and their corresponding areas.

[0055] An irradiation calculation model refers to a series of calculation formulas related to the activity concentration value of a certain type of radionuclide on a measurement surface, in order to calculate the total effective dose value produced by that type of radionuclide from the activity concentration value of that type of radionuclide.

[0056] Understandably, in the irradiation calculation model, the activity concentration value of the corresponding type of radionuclide and the area of ​​the measurement surface are independent variables, while the total effective dose produced by this type of radionuclide is the dependent variable.

[0057] S40: Substitute the assumed activity concentration values ​​of various radionuclides and the area of ​​each measurement surface into the radiation dose calculation model to calculate the first assumed maximum effective dose value of various radionuclides on each measurement surface.

[0058] The assumed activity concentration value refers to a preset activity concentration value for ease of calculation, and it can be of any value. Given that other parameters in the radiation dose calculation model are fixed, the assumed activity concentration value can be input into the radiation dose calculation model to calculate the corresponding first assumed maximum effective dose value.

[0059] Activity concentration refers to the radioactivity per unit volume.

[0060] The first assumed maximum effective dose value refers to the radiation dose received by a population when the activity concentration of a certain type of radionuclide on a certain measurement surface of the target building is the assumed activity concentration value.

[0061] S50: Calculate the sum of the first assumed maximum effective dose values ​​of each measurement surface in the same space to obtain the total assumed maximum effective dose value. Calculate the permissible residual activity concentration values ​​of various radionuclides based on the assumed activity concentration value, the total assumed maximum effective dose value, and the dose constraint value.

[0062] Each measurement surface refers to the surface that encloses and forms the space inside the target building.

[0063] The permissible residual activity concentration value refers to the activity concentration value of a certain type of radionuclide when the radiation dose received by a population of a certain type of radionuclide is within the dose constraint value.

[0064] S60: Obtain the actual residual activity concentration values ​​of various radionuclides inside the target after the completion of the decommissioning final state construction, and obtain the evaluation results based on the actual residual activity concentration values ​​and allowable residual activity concentration values ​​of various radionuclides.

[0065] The final decommissioning target refers to the buildings in the target area where the nuclear facility is located that will be used for other purposes after the nuclear facility is decommissioned.

[0066] The actual residual activity concentration value refers to the actual activity concentration value of various radionuclides inside the decommissioned target after the completion of the decommissioning target construction.

[0067] The evaluation results obtained by comparing the actual residual activity concentration value and the allowable residual activity concentration value determine whether the radioactivity produced by various radionuclides inside the decommissioned target meets the radiation safety requirements for the population.

[0068] The residual radioactivity evaluation method in this embodiment of the invention establishes an irradiation dose calculation model to calculate the allowable residual activity concentration value inside the decommissioned final-state building. Then, based on the obtained allowable residual activity concentration value, it can be determined whether the radiation level of the decommissioned final-state building after construction meets the radiation safety requirements for the population. This enables the evaluation of the remediation effect of radioactive contaminated sites and provides a reliable basis for the radiation protection of the population.

[0069] It is understandable that, since the assumed activity concentration value is a pre-defined value, the assumed activity concentration values ​​of various radionuclides can be the same or different during the calculation process.

[0070] It is understandable that the final decommissioning targets for different types of nuclear facilities will have different radiation shielding effects due to the differences in their structural types, and their corresponding metrological constraint values ​​will also differ.

[0071] In some embodiments, obtaining the dose constraint value specifically includes:

[0072] The dose constraint value is determined based on the type of decommissioned final state target that needs to be constructed in the target area.

[0073] In other words, corresponding dose constraint values ​​are formulated according to the different types of final decommissioning targets, so as to obtain more accurate and reasonable allowable residual activity concentration values ​​for various radionuclides, which is conducive to providing a more reliable basis for radiation protection of the population.

[0074] The specific type of the final state goal for retirement is not limited, such as the unrestricted open type.

[0075] In the embodiment where the type of the final retirement target is the unrestricted open type, the dose constraint value is 0.01 mSv / a (millisievert per year).

[0076] Unrestricted access type refers to types where personnel can enter and exit without radiation protection restrictions, such as exhibition halls.

[0077] The measurement surface is a single surface, which can be a plane or a curved surface.

[0078] Understandably, the number and orientation of measurement surfaces corresponding to the interior space will vary depending on the specific type of the target building.

[0079] For example, measuring the area of ​​each measuring surface within the target building specifically includes:

[0080] The target building is a reactor building, and the internal space of the reactor building is a cube. The measurement surfaces are two opposite planes along the first direction, two opposite planes along the second direction, and two opposite planes along the third direction of the internal space of the reactor building. The first direction, the second direction, and the third direction are orthogonal to each other. The area of ​​each measurement surface is measured.

[0081] In other words, the reactor building has only one cubic space inside, and the specific number of measurement surfaces corresponding to this space is six, all of which are planar.

[0082] When a group of people are inside the reactor building, they will be exposed to radioactive nuclides from six surfaces within the reactor building. By calculating the areas of two measuring surfaces from the first, second, and third directions respectively, and combining this with the radiation dose formula, the radiation dose to the group from each of the six surfaces inside the reactor building can be obtained, making the final calculation results more accurate.

[0083] It is understandable that one of the first, second, and third directions is the direction of gravity.

[0084] It is understandable that for different types of decommissioned end-state targets, the specific ways in which the radioactive nuclides contained inside the buildings irradiate the human body are different, and there are differences in the effective dose values ​​produced by different methods on the human body.

[0085] In some embodiments, before establishing a radiation dose calculation model corresponding to various radionuclides and area, the residual radioactivity evaluation method further includes:

[0086] Determine the type of irradiation pathway.

[0087] The path of exposure refers to the way in which radioactive materials can reach or irradiate the human body.

[0088] The specific type of irradiation route is not limited, such as inhalation of dust or other suspended matter contaminated with radioactive nuclides, or external irradiation directly caused by radioactive nuclides adhering to the measuring surface.

[0089] In the radiation dose calculation model, the total effective dose is the sum of the effective dose values ​​produced by various irradiation pathways, and the effective dose value produced by each irradiation pathway is related to the activity concentration of the radionuclide on the measurement surface.

[0090] In other words, on a certain measurement surface, the effective dose value of a certain type of radionuclide is obtained by using the assumed activity concentration value of that type of radionuclide in each irradiation path. By adding the effective dose values ​​obtained from each irradiation path, the total effective dose value of that type of radionuclide on the measurement surface can be obtained, which is the second assumed maximum effective dose value corresponding to the assumed activity concentration value.

[0091] This allows the radiation dose model to more comprehensively consider the effects of radionuclides on the human body through different mechanisms, thereby enabling the final permissible residual activity concentration value to more accurately meet the public's radiation safety requirements.

[0092] It is understandable that the area of ​​the measurement surface is a two-dimensional plane measurement indicator, while the active concentration of a radionuclide refers to the radiation dose produced per unit mass, which is a three-dimensional space measurement indicator. Therefore, it is necessary to convert the area of ​​the measurement surface into parameters that can be substituted into the radiation dose calculation model.

[0093] In some embodiments, a radiation dose calculation model corresponding to various radionuclides and area is established, specifically including:

[0094] Establish a calculation model for the radiation dose of various radionuclides corresponding to their volume;

[0095] The assumed activity concentration values ​​of various radionuclides and the areas of each measurement surface are substituted into the radiation dose calculation model, specifically including:

[0096] Establish a reference volume source corresponding to each measurement surface. The projected area of ​​the reference volume source perpendicular to its thickness direction is the same as the area of ​​the corresponding measurement surface. The thickness of the reference volume source does not exceed the preset thickness.

[0097] The assumed activity concentration values ​​of various radionuclides and the volumes of each reference volume source are substituted into the radiation dose calculation model.

[0098] The preset thickness of the reference volume source is a preset thickness value, the purpose of which is to form a three-dimensional reference volume source, rather than a specific value.

[0099] Thus, the area of ​​the measuring surface is converted into the volume of the reference volume source, which is the product of the area of ​​the measuring surface and the preset thickness. By substituting the volume of the reference volume source and the activity concentration value of the radionuclide into the irradiation dose calculation model, the first assumed maximum effective dose value can be obtained.

[0100] In some embodiments, the irradiation route is external irradiation, and the irradiation dose calculation model is a function of the effective dose value of external irradiation with respect to the irradiation duration, the activity concentration value of the radionuclide, and the distance of the person relative to the measurement surface.

[0101] In other words, the effective dose is the dependent variable, while the irradiation duration, the activity concentration of the radionuclide, and the distance between the person and the measurement surface are all independent variables.

[0102] It is understandable that radioactive nuclides adhere to the surface of the measurement surface, meaning that radioactive nuclides are only present in a very shallow area within the interior space of the target building. Therefore, if the preset thickness of the reference volume source is a large value, the radiation dose of its radioactive nuclides will be significantly greater than the actual situation, resulting in a large error in the results obtained from the radiation dose calculation model.

[0103] In some embodiments, the preset thickness is no more than 0.01 mm (millimeters).

[0104] Thus, within the orientation of this thickness value, it can better reflect the actual situation that radionuclides only adhere to the surface of the measurement surface, which is conducive to improving the accuracy of the results obtained by the radiation dose calculation model.

[0105] The specific value of the preset thickness is not limited, such as 0.006mm, 0.007mm, 0.008mm, 0.009mm, 0.01mm, etc.

[0106] The specific method for calculating the permissible residual activity concentration value is not limited.

[0107] For example, assume the following relationship exists between the activity concentration value, the first assumed maximum effective dose value, the dose constraint value, and the permissible residual activity concentration value:

[0108] C H / E T =C L / E L

[0109] Among them, C H This is a hypothetical activity concentration value, in units of Bq / g (Becquerel per gram); E T The first assumed maximum effective dose value is expressed in mSv / a; C L This is the permissible residual activity concentration value, in Bq / g; E L This is the dose constraint value, in mSv / a.

[0110] In other words, the ratio of the activity concentration value to the first assumed maximum effective dose value is assumed to be equal to the ratio of the allowable residual activity concentration value to the dose constraint value.

[0111] Thus, after obtaining the first assumed maximum effective dose by substituting the assumed activity concentration value into the irradiation dose calculation model and determining the dose constraint value, the specific value of the allowable residual activity concentration can be determined through the above equation.

[0112] It is understandable that in embodiments with a reference volume source, since the preset thickness is very small, the activity concentration value C is assumed to be... H and permissible residual activity concentration value C L The unit can also be Bq / m 2 (Becquerel per squaremetre) is used to directly calculate the radiation dose to the measurement surface.

[0113] It is understandable that when multiple radionuclides are present in a target building, the radiation received by the human body comes from the combined effect of these multiple radionuclides. In other words, it is not only necessary for the radiation dose of a single type of radionuclide remaining on the interior surface of the target building to meet safety requirements, but also for the combined radiation dose from all types of radionuclides to meet safety requirements.

[0114] In some embodiments, the evaluation results are obtained based on the actual residual activity concentration values ​​and permissible residual activity concentration values ​​of various radionuclides, specifically including:

[0115] The actual residual activity concentration and the allowable residual activity concentration have the following relationship:

[0116]

[0117] Among them, C Ai This represents the actual residual activity concentration of radionuclide i in the soil, in Bq / m³. 2 C Li Let be the allowable residual activity concentration of radionuclide i in the soil, and n be the number of radionuclide species in the soil, i.e., n≥1.

[0118] In other words, the sum of the ratios of the actual residual activity concentration of each radionuclide to the permissible residual activity concentration should not exceed 1. Under these conditions, the combined radiation dose from all radionuclides meets safety requirements.

[0119] Thus, by normalizing the activity concentration values ​​of various radionuclides, the effects of the radioactivity of various radionuclides can be comprehensively considered in a dimensionless manner to determine whether they meet the dose constraint value. Finally, it is determined whether the radiation dose inside the decommissioned target meets the dose constraint value requirement, that is, whether the safety requirements for personnel in the decommissioned target are met.

[0120] In some embodiments, the types of radionuclides obtained inside the target building specifically include:

[0121] Determine multiple initial sampling locations on the interior walls of the target building;

[0122] The first sample is obtained by wiping and sampling at each of the first sampling locations;

[0123] Each first sample is tested to determine the types of radionuclides.

[0124] In other words, a sampling survey of the radiation sources on the interior surfaces of the target building is conducted to obtain the types of radionuclides while reducing the workload.

[0125] The specific method for obtaining the first sample by wiping is not limited; for example, the surface of the first sampling location can be wiped with a non-woven fabric.

[0126] It should be noted that the specific methods and related equipment for detecting the type of radionuclide in the first sample have been disclosed in relevant technologies and will not be elaborated here.

[0127] It is understandable that, while testing the first sample, the activity concentration values ​​of various radionuclides in the target building before construction can be obtained.

[0128] The average value of the activity concentration of radionuclides obtained from the detection of each first sample before construction is taken to more intuitively reflect the approximate radiation level of the target building before construction. This facilitates the assessment of the distribution and degree of residual radioactive contamination in the target building before construction, so as to formulate an appropriate purification plan in combination with the allowable residual activity concentration value. This is conducive to ensuring that the actual residual activity concentration values ​​of various radionuclides in the internal space after the construction of the final decommissioning target meet the requirements of the allowable residual activity concentration value.

[0129] In some embodiments, obtaining the actual residual activity concentration values ​​of various radionuclides inside the target after the completion of decommissioning and finalization construction specifically includes:

[0130] Determine multiple second sampling locations for the final state target of decommissioning;

[0131] Second samples were collected by wiping at each of the second sampling locations;

[0132] The second sample was tested to obtain the actual residual activity concentration values ​​of various radionuclides.

[0133] The average value of the activity concentration of radionuclides obtained from the detection of each second sample is taken to obtain the actual residual activity concentration of each type of radionuclide.

[0134] The second sampling location is on the surface of the interior space of the decommissioned target after construction is completed. For example, the first sampling location is a portion of the wall of the reactor building before construction, and after construction, tiles are laid on the wall of the reactor building, and the second sampling location is a portion of the tile surface.

[0135] The second sampling position can be completely different from the first sampling position; it can be partially different; or it can be exactly the same.

[0136] A specific embodiment of the present invention is as follows:

[0137] An investigation was conducted on the target building housing the decommissioned nuclear facility to identify multiple primary sampling locations within the building. First samples were collected from each primary sampling location. Each primary sample was analyzed to obtain the types of radionuclides and their pre-construction activity concentrations.

[0138] The soil in the target area was found to contain three radionuclides: 60 Co、 137 Cs、 125 Eu.

[0139] The final decommissioning goal for the nuclear facility was determined to be the transformation of the reactor building into an exhibition hall. The exhibition hall will be open to the public without restrictions, with a dose constraint of 0.01 mSv / a.

[0140] Based on the final goal of the decommissioning process being the exhibition hall, the irradiation method was determined to be external irradiation.

[0141] The reactor building has a cubic interior space with a length, width, and height of 49 m, 24 m, and 18 m respectively, and the area of ​​its six measuring faces is 1176 m². 2 (square metre, square meters), 1176m 2 882m 2 882m 2 432m 2 and 432m 2

[0142] The radiation dose models for various radionuclides are as follows:

[0143] 1) Total dose

[0144] For estimating the radiation dose to contaminated soil, the total effective dose equals the sum of the doses produced through all pathways. Specifically:

[0145] E tot =E ext

[0146] In the above formula, E tot Total effective dose, expressed in Sv / a (sievert per year); E ext The effective dose produced by external radiation to the Earth's surface is expressed in Sv / a.

[0147] Establish a reference volume source corresponding to each measurement surface. The projected area of ​​the reference volume source perpendicular to its thickness direction is the same as the area of ​​the corresponding measurement surface. The thickness of the reference volume source is 0.01 mm.

[0148] The effective dose produced by external irradiation of each type of radionuclide on each measurement surface is related to the irradiation duration, the activity concentration of the radionuclide, and the distance of personnel relative to the measurement surface, satisfying the following relationship:

[0149]

[0150] In the above formula, F in The indoor dwelling factor is dimensionless. The external dose coefficient of an infinite volume source is expressed in units of (mrem / yr) / (pCi / g), where mrem (millirem) and mSv are interconvertible, and pCi (picocuries) and Bq are interconvertible. Let n be the geometric factor of the radioactive nuclide n in the source at time t, which is dimensionless and has a specific correlation with the distance measurement surface of the crowd. t represents the activity concentration of the radionuclide in the volume source at time t, in Bq / g; ED represents the exposure duration of the population, in days.

[0151] Among them, F in , The relevant specifications and standards can be obtained by consulting the relevant standard documents, and will not be elaborated here.

[0152] The assumed activity concentration of all radionuclides is set to 1 Bq / m³. 2 Substitute these values ​​into each irradiation dose model to calculate the first assumed maximum effective dose value for each measurement surface.

[0153] Calculations yielded radionuclides 60 The first assumed maximum effective dose values ​​for Co generated on six measurement surfaces representing an individual are: 1.18E-06 mSv / a, 2.71E-07 mSv / a, 8.52E-06 mSv / a, 1.18E-06 mSv / a, 2.71E-07 mSv / a, and 1.13E-06 mSv / a. Among these, 8.52E-06 mSv / a and 1.13E-06 mSv / a correspond to the measurement surfaces of the floor and ceiling, respectively.

[0154] Calculations yielded radionuclides 137 The first hypothetical maximum effective dose values ​​of Cs for individuals on the six polluted surfaces are: 2.95E-07 mSv / a, 6.83E-08 mSv / a, 2.11E-06 mSv / a, 2.95E-07 mSv / a, 6.83E-08 mSv / a, and 2.83E-07 mSv / a. Among these, 2.11E-06 mSv / a and 2.83E-07 mSv / a correspond to the measurement surfaces of the floor and ceiling, respectively.

[0155] Calculations yielded radionuclides 152 The first hypothetical maximum effective dose values ​​(E) for individuals on six contaminated surfaces were: 5.84E-07 mSv / a, 1.36E-07 mSv / a, 4.15E-06 mSv / a, 5.84E-07 mSv / a, 1.36E-07 mSv / a, and 5.61E-07 mSv / a. Among these, 4.15E-06 mSv / a and 5.61E-07 mSv / a correspond to the measurement surfaces of the floor and ceiling, respectively.

[0156] Summing them separately, the contaminating nuclides can be calculated. 60 Co、 137 Cs、 152 The total hypothetical maximum effective dose values ​​of Eu for individuals are 1.26E-05 mSv / a, 3.12E-06 mSv / a, and 6.15E-06 mSv / a, respectively.

[0157] The permissible residual activity concentration values ​​for various radionuclides are calculated using the following formula:

[0158] C H / E T =C L / E L

[0159] Determine the permissible residual activity concentration values ​​for the three nuclides: 60 The permissible residual activity concentration of Co is 7.9E+02Bq / m³. 2 , 137 The permissible residual activity concentration of Cs is 3.2E+03 Bq / m³. 2 , 90 The permissible residual activity concentration of Sr is 1.6E+03 Bq / m³. 2 .

[0160] After the construction of the exhibition hall was completed, multiple second sampling locations were determined for the soil inside the exhibition hall. Second samples were obtained by wiping and sampling at each second sampling location. The second samples were then tested to obtain the actual residual activity concentration values ​​of various radionuclides.

[0161] Substitute the permissible residual activity concentration values ​​calculated from the above three types of radionuclides and the actual residual activity concentration values ​​obtained from the tests into the following relationship:

[0162]

[0163] If the sum of the above is greater than 1, it indicates that the radiation level in the exhibition hall does not meet the expected radiation safety standards for each population group; if the sum of the above is less than or equal to 1, it indicates that the radiation level in the exhibition hall meets the expected radiation safety standards for each population group.

[0164] The various embodiments / implementations provided by this invention can be combined with each other without creating contradictions.

[0165] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. For those skilled in the art, various modifications and variations can be made to the embodiments of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of the present invention should be included within the protection scope of the embodiments of the present invention.

Claims

1. A method for evaluating the residual radioactivity of a decommissioned building in its final state, characterized in that, The method for evaluating residual radioactivity includes: Obtain the types and dose constraints of radionuclides inside the target building; Measure the area of ​​each measuring surface within the target building; Establish a calculation model for the radiation dose of various radionuclides corresponding to the area; Substitute the assumed activity concentration values ​​of various radionuclides and the area of ​​each of the measurement surfaces into the irradiation dose calculation model to calculate the first assumed maximum effective dose value of each radionuclide on each of the measurement surfaces. The sum of the first assumed maximum effective dose values ​​of each of the measurement surfaces is calculated to obtain the total assumed maximum effective dose value. The permissible residual activity concentration values ​​of various radionuclides are calculated based on the assumed activity concentration value, the total assumed maximum effective dose value and the dose constraint value. After the completion of the decommissioning final state target construction, the actual residual activity concentration values ​​of various radionuclides inside the target are obtained, and the evaluation results are obtained based on the actual residual activity concentration values ​​and the allowable residual activity concentration values ​​of various radionuclides.

2. The method for evaluating residual radioactivity according to claim 1, characterized in that, The acquisition of the dose constraint value specifically includes: The dose constraint value is determined based on the type of the decommissioned final state target to be constructed in the target area.

3. The method for evaluating residual radioactivity according to claim 1, characterized in that, The area of ​​each measuring surface within the target building is specifically included in the measurement: The target building is a reactor building, and the internal space of the reactor building is a cube. The measuring surfaces are two opposite planes along a first direction, two opposite planes along a second direction, and two opposite planes along a third direction in the internal space of the reactor building. The first direction, the second direction, and the third direction are orthogonal to each other. The area of ​​each of the measuring surfaces is measured.

4. The method for evaluating residual radioactivity according to claim 1, characterized in that, Before establishing the radiation dose calculation model corresponding to various radionuclides and area, the residual radioactivity evaluation method further includes: Determine the type of irradiation pathway; In the radiation dose calculation model, the total effective dose value is the sum of the effective dose values ​​generated by each of the irradiation pathways, and the effective dose value generated by each of the irradiation pathways is related to the activity concentration of the radionuclide on the measurement surface.

5. The method for evaluating residual radioactivity according to claim 4, characterized in that, The establishment of radiation dose calculation models corresponding to various radionuclides and areas specifically includes: Establish a calculation model for the radiation dose of various radionuclides corresponding to their volume; The step of substituting the assumed activity concentration values ​​of various radionuclides and the area of ​​each of the measurement surfaces into the radiation dose calculation model specifically includes: Establish a reference volume source corresponding to each of the measurement surfaces. The projected area of ​​the reference volume source perpendicular to its thickness direction is the same as the area of ​​the corresponding measurement surface. The thickness of the reference volume source does not exceed a preset thickness. The assumed activity concentration values ​​of various radionuclides and the volumes of each of the aforementioned reference volume sources are substituted into the radiation dose calculation model.

6. The method for evaluating residual radioactivity according to claim 5, characterized in that, The irradiation method is external irradiation, and the irradiation dose calculation model is a function of the effective dose value of the external irradiation with respect to the irradiation duration, the activity concentration value of the radionuclide, and the distance of the person relative to the measurement surface.

7. The method for evaluating residual radioactivity according to claim 5, characterized in that, The preset thickness does not exceed 0.01 mm.

8. The method for evaluating residual radioactivity according to claim 1, characterized in that, The following relationship exists between the assumed activity concentration value, the total assumed maximum effective dose value, the dose constraint value, and the permissible residual activity concentration value: C H / AND T =C L / AND L Among them, C H E is the assumed activity concentration value. T C is the total assumed maximum effective dose value. R E represents the permissible residual activity concentration value. L This refers to the dose constraint value.

9. The method for evaluating residual radioactivity according to claim 1, characterized in that, The evaluation results, obtained based on the actual residual activity concentration values ​​and the permissible residual activity concentration values ​​of various radionuclides, specifically include: The actual residual activity concentration value and the allowable residual activity concentration value have the following relationship: Among them, C Ai C represents the actual residual activity concentration of radionuclide i in the soil. Ri The permissible residual activity concentration value of radionuclide i in the building, and n is the number of types of radionuclides in the soil.

10. The method for evaluating residual radioactivity according to claim 1, characterized in that, The types of radionuclides obtained from inside the target building specifically include: Determine multiple initial sampling locations on the interior walls of the target building; First samples are obtained by wiping and sampling at each of the first sampling locations; Each of the first samples is tested to obtain the types of radionuclides.

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