A method for detecting radioactive waste classification

Abstract

The application discloses a radioactive waste classification detection method, comprising the following steps: S10: obtaining weight information and density information of radioactive waste; S20: obtaining a nuclear signal of total activity of the radioactive waste to be detected, integrating the weight information, the density information and the nuclear signal of the total activity to obtain total activity concentration of the radioactive waste; S30: judging whether the total activity concentration exceeds an upper limit value range requirement of a very low radioactive level, and performing classification; S40: obtaining a nuclear signal of at least one nuclide activity of the radioactive waste to be detected, integrating the weight information, the density information and the nuclear signal of the nuclide activity to obtain nuclide activity concentration of at least one nuclide of the radioactive waste; and S50: judging whether the nuclide activity concentration exceeds the upper limit value range requirement of the very low radioactive level, and performing classification. The application can quickly and in batches classify radioactive waste through total amount detection and judgment for primary classification and nuclide detection and judgment for secondary classification, and is convenient for subsequent waste treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radioactive waste classification processing, and particularly relates to a radioactive waste classification detection method. BACKGROUND

[0002] In January 2018, the Classification of Radioactive Waste was released, which clearly defined the standards for radioactive waste, including low-level radioactive waste, very low-level radioactive waste, etc., which means that all radioactive waste producing units can timely classify and process potential radioactive waste according to the method, provide a basis for the national radioactive waste management strategy, and provide a basis for the safety management of the whole process of radioactive waste production, treatment, storage, disposal, etc., to ensure that the radioactive waste producing units manage the waste in a safe and economical manner.

[0003] At present, the related art for detecting and classifying very low-level radioactive waste is to measure radioactive waste by a high-purity germanium spectrometer and classify it, as described in detail in the patent application with the publication number CN114019555A. Although the high-purity germanium detector has the characteristics of high resolution, the detection efficiency is very low. If it is desired to measure very low-level radioactive waste and low-level radioactive waste, the measurement time needs to be greatly prolonged, which is not conducive to rapid large-scale measurement. Moreover, the pretreatment of the sample is also relatively complex, and a transmission device is required, which is high in cost. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a radioactive waste classification detection method.

[0005] The technical solution adopted by the present application to solve the technical problem is: a radioactive waste classification detection method, comprising the following steps:

[0006] S10: obtaining weight information and density information of the radioactive waste;

[0007] S20: obtaining a total activity nuclear signal of the radioactive waste, and integrating the weight information, the density information and the total activity nuclear signal to obtain a total activity concentration of the radioactive waste;

[0008] S30: determining whether the total activity concentration exceeds a very low-level radioactive upper limit value range requirement;

[0009] If the total activity concentration exceeds the very low-level radioactive upper limit value range requirement, step S40 is performed; if the total activity concentration is lower than or equal to the very low-level radioactive upper limit value range requirement, it is determined that the radioactive waste is very low-level radioactive waste and the process ends;

[0010] S40: obtaining a nuclear signal of at least one nuclide activity of the radioactive waste, integrating the weight information, the density information and the nuclear signal to obtain a nuclide activity concentration of at least one nuclide of the radioactive waste;

[0011] S50: judging whether the nuclide activity concentration exceeds an upper limit value range requirement of a very low radioactive level;

[0012] If the nuclide activity concentration exceeds the upper limit value range requirement of the very low radioactive level, it is determined that the radioactive waste is a low radioactive level waste; if the nuclide activity concentration is lower than or equal to the upper limit value range requirement of the very low radioactive level, it is determined that the radioactive waste is a very low radioactive level waste.

[0013] Preferably, in the radioactive waste classification detection method, in step S20, the total activity nuclear signal of the radioactive waste is measured by a scintillator detector.

[0014] Preferably, in the radioactive waste classification detection method, the scintillator detector comprises a plurality of NaI crystal units.

[0015] Preferably, in the radioactive waste classification detection method, the volume of the plurality of NaI crystal units is greater than or equal to 16L.

[0016] Preferably, in the radioactive waste classification detection method, in step S40, the nuclide activity nuclear signal of the radioactive waste is measured by a semiconductor detector.

[0017] Preferably, in the radioactive waste classification detection method, the semiconductor detector is a high-purity germanium detector or a cadmium zinc telluride detector.

[0018] Preferably, in the radioactive waste classification detection method, in step S10, the radioactive waste is loaded into a shaping container to be shaped into a regular shape to obtain volume information and weighed to obtain the weight information, and the density information is calculated using the volume information and the weight information.

[0019] Preferably, in the radioactive waste classification detection method, according to the density information, a corresponding efficiency calibration factor is called from a passive efficiency calibration factor database, and the total activity nuclear signal and the nuclide activity nuclear signal are combined to obtain the total activity concentration and the nuclide activity concentration.

[0020] Preferably, in the radioactive waste classification detection method, the total activity nuclear signal is converted into a total activity concentration and the nuclide activity nuclear signal is converted into a nuclide activity concentration by gamma spectrum analysis.

[0021] Preferably, in the radioactive waste classification detection method of the present application, the nuclides include 60 Co, 137 Cs, 54 Mn, 58 Co, 95 Nb, 51 Cr, 95 Zr.

[0022] By implementing the present application, the following beneficial effects are achieved:

[0023] The radioactive waste classification detection method of the present application uses the weight information and density information of the radioactive waste, combined with the total activity nuclear signal of the radioactive waste, to perform primary classification, to preliminarily and quickly determine whether it is very low level waste, and if it is not clear whether it is very low level waste, combined with the nuclide activity nuclear signal of the radioactive waste, to perform secondary classification, to determine whether the radioactive waste that is not clear in the primary classification is very low level waste, so that the radioactive waste can be quickly and batch classified, which is convenient for subsequent waste treatment. BRIEF DESCRIPTION OF DRAWINGS

[0024] The present application will be further described below in conjunction with the drawings and examples, in which:

[0025] Figure 1 is a flowchart of the radioactive waste classification detection method of an embodiment of the present application.

[0026] Figure 2 is a schematic diagram of a passive efficiency calibration method of the detector of the present application. DETAILED DESCRIPTION

[0027] In order to have a clearer understanding of the technical features, objectives and effects of the present application, the specific embodiments of the present application will be described in detail below with reference to the drawings.

[0028] It should be noted that the flowchart shown in the drawings is only illustrative, and does not necessarily include all the contents and operations / steps, nor does it necessarily execute in the order described. For example, some operations / steps can be further divided, and some operations / steps can be combined or partially combined, so the actual execution order may be changed according to the actual situation.

[0029] The block diagram shown in the drawings is only a functional entity, which does not necessarily correspond to a physically independent entity. That is, these functional entities can be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0030] The upper limit value range of the extremely low radioactivity level of the present application refers to the upper limit value range of the extremely low radioactivity level specified in the “Classification of Radioactive Waste” issued in 2018, and specific provisions are provided therein. It can be understood that the upper limit value range of the extremely low radioactivity level is only a basis for determining whether the radioactive waste is extremely low radioactivity level waste. If the upper limit value range of the extremely low radioactivity level is updated later, the present application will use the updated upper limit value range of the extremely low radioactivity level for determination.

[0031] One embodiment of the present application discloses a radioactive waste classification detection method, which can quickly and in large quantities distinguish the classification method of low-level radioactive waste and extremely low-level radioactive waste. It can be understood that the radioactive waste of the present application can be the radioactive waste of a nuclear power plant, especially solid radioactive waste. There are very few medium and high level radioactive waste in nuclear power plants, and a dose measurement preliminary screening is performed on the radioactive waste of the nuclear power plant in the early stage to determine whether it belongs to medium and high level radioactive waste. Therefore, the radioactive waste measured and classified by the present application generally does not belong to medium and high level radioactive waste, and the classification and treatment of medium and high level radioactive waste is generally not considered.

[0032] Referring to Figure 1 The radioactive waste classification detection method of the present application includes the following steps in some embodiments:

[0033] S10: Obtain the weight information and density information of the radioactive waste. The weight information includes the weight of the radioactive waste, which is one of the elements for calculating the total activity concentration and nuclide activity concentration. The density information includes the density of the radioactive waste, which can be used to assist in calculating the total activity concentration and nuclide activity concentration. Preferably, in some embodiments, the radioactive waste can be loaded into a shaping container to form a regular shape, and the volume information can be measured and the weight information can be obtained by weighing. The volume information can include the length, width and height of the radioactive waste, and the volume can be calculated. The density is calculated using the weight and volume of the radioactive waste. The shaping container refers to a container loaded with radioactive waste and having an open side. The container can be made of stainless steel. The radioactive waste is placed in the shaping container and compacted into a regular shape using other tools to facilitate volume calculation. For example, the size of the shaping container is 60cmx60cmx10cm, the box thickness is 2mm, and the radioactive waste can be easily calculated when loaded. It can be understood that the method of obtaining volume information and obtaining weight information by weighing to calculate density information described in the present application is only an example. In other embodiments, weight information and volume information can also be obtained to calculate density information using other methods, which are all within the scope of the present application.

[0034] Compared with the related art, the present application does not need to perform complex pretreatment on radioactive waste, can simply pack and shape, can batch process radioactive waste, reduces equipment investment, and reduces cost.

[0035] S20: Obtain the total activity nuclear signal of the radioactive waste, integrate the weight information, the density information, and the total activity nuclear signal to obtain the total activity concentration of the radioactive waste. Preferably, the total activity nuclear signal of the radioactive waste can be measured by a scintillator detector, or can be measured by using other detectors. The scintillator detector can be a large-volume scintillator detector with high detection efficiency. Preferably, the scintillator detector includes a plurality of NaI crystal units, and other crystal units that can meet the high detection efficiency, such as LaBr3, CsI, and ZnS.

[0036] Further, in order to meet the high detection efficiency, when using NaI crystal units, the volume of the plurality of NaI crystal units is greater than or equal to 16L, and the number of NaI crystal units can be 4, 8, or 12, as long as the total volume is greater than or equal to 16L. For example, at least 4 NaI crystal units each with a size of 40cm×20cm×5cm and a volume of 4L are required, or at least 8 NaI crystal units each with a size of 40cm×10cm×5cm and a volume of 2L are required. It can be understood that in other embodiments, LaBr3, CsI, or ZnS crystals can be used instead of NaI crystals. For example, when using LaBr3 crystal units, in order to meet the high detection efficiency, the plurality of LaBr3 crystal units also meet the condition that the volume is greater than or equal to 16L. It should be noted that the present application does not limit the size of the NaI crystal units, as long as the volume is greater than or equal to 16L.

[0037] Preferably, in order to assist in achieving the detection function of the scintillator detector, the scintillator detector in some embodiments further includes a matching electronic system, such as a photomultiplier tube, a preamplifier, a main amplifier, an analog-to-digital converter, and an FPGA (Field Programmable Gate Array). The matching electronic system is very mature in the related art, and can be selected as needed, and will not be described here.

[0038] The total activity nuclear signal in some embodiments can be converted into the total radioactivity of the radioactive waste by gamma spectrum analysis, and the total activity concentration of the radioactive waste is equal to the ratio of the total radioactivity to the weight of the radioactive waste. Preferably, for the calculation of the total activity concentration of the radioactive waste, the total activity nuclear signal obtained in step S20 and the weight information and the density information obtained in step S10 can be input into a computer software to automatically collect, record, and calculate the total activity concentration of the radioactive waste, wherein the computer software at least includes a gamma spectrum analysis module.

[0039] S30: determining whether the total activity concentration exceeds the upper limit value range of the very low level of radioactivity, and quickly making a first-level determination. Preferably, the currently applicable upper limit value range of the total activity concentration of radioactive waste of the very low level of radioactivity is the upper limit value range of the very low level of radioactivity specified in the “Classification of Radioactive Waste” issued in 2018. If the total activity concentration exceeds the upper limit value range of the very low level of radioactivity, it cannot be directly determined as very low level of radioactivity waste, but also cannot be directly determined as non-very low level of radioactivity waste, and needs to be subjected to steps S40 and S50 for secondary detection determination.

[0040] If the total activity concentration is lower than or equal to the upper limit value range of the very low level of radioactivity, it is determined that the radioactive waste is very low level of radioactivity waste and the process ends, and subsequent classification processing can be performed.

[0041] S40: obtaining a nuclear signal of at least one nuclide activity of the radioactive waste, integrating the weight information, the density information and the nuclear signal of the nuclide activity to obtain the nuclide activity concentration of at least one nuclide of the radioactive waste. In some embodiments, the nuclear signal of the nuclide activity can be converted into the radioactivity nuclide activity of the radioactive waste by gamma spectrum analysis, and the nuclide activity concentration of the radioactive waste is equal to the ratio of the radioactivity nuclide activity to the weight of the radioactive waste. The principle of gamma spectrum analysis is the same as described above, and will not be repeated here.

[0042] Preferably, the nuclear signal of the nuclide activity of the radioactive waste can be detected by a semiconductor detector, wherein the nuclides can include but are not limited to 60 Co, 137 Cs, 54 Mn, 58 Co, 95 Nb, 51 Cr, 95 Zr and other nuclides that can exist in radioactive waste. The semiconductor detector can be a high-resolution high-purity germanium detector, or a cadmium zinc telluride detector, or other detectors with high-resolution characteristics.

[0043] Preferably, in order to assist in achieving the detection function of the semiconductor detector, the semiconductor detector in some embodiments further includes a matching electronic system, such as a preamplifier, an analog-to-digital converter and an FPGA. Since the matching electronic system is very mature in related technologies, it can be selected as needed, and will not be repeated here.

[0044] S50: judging whether the nuclide activity concentration exceeds the upper limit value range of the extremely low level of radioactivity, comparing each nuclide activity concentration with the upper limit value range of the extremely low level of radioactivity of the nuclide, if the nuclide activity concentration exceeds the upper limit value range of the extremely low level of radioactivity, determining that the radioactive waste is low level waste, and the subsequent treatment can be carried out, if the nuclide activity concentration is lower than or equal to the upper limit value range of the extremely low level of radioactivity, determining that the radioactive waste is extremely low level waste, and the subsequent treatment can be carried out.

[0045] The radioactive waste classification detection method of the present application sets two levels of measurement according to the characteristics of extremely low level waste, and classifies the waste to be measured efficiently. In the first level of measurement, a large-volume scintillator detector with high detection efficiency is set to realize short-time measurement of large-flow waste; in the second level of measurement, a high-resolution semiconductor detector is set to perform more detailed energy spectrum measurement on the radioactive waste whose total activity concentration measured by the scintillator detector exceeds the upper limit value range of the extremely low level of radioactivity, and the nuclide activity concentration of the nuclide level of the waste to be measured can be measured, thereby greatly improving the classification and detection efficiency in the case that the activity of most radioactive waste is low. The radioactive waste classification detection method of the present application is scientific and efficient, can realize simple, rapid and large-scale automatic classification of extremely low level waste, and has a strong application prospect.

[0046] Further, the computer software can further include a passive efficiency calibration module, which can call corresponding efficiency calibration factors from a passive efficiency calibration factor database according to the density information and combine the nuclear signals of the total activity concentration and the at least one nuclide activity concentration to obtain the total activity concentration and the nuclide activity concentration.

[0047] The passive efficiency calibration factor database is a self-defined database, which is specifically as follows:

[0048] As shown in Figure 2 The passive efficiency calibration method of the detector of the present application is shown in FIG. 1, which is applicable to the scintillator detector, the semiconductor detector and other detectors mentioned above. V is defined as an arbitrary volume source, dv is a microelement of the source V, S1 is the area of the end face of the detector relative to dv, and S2 is the area of the side face of the detector relative to dv. It is assumed that the emission rate of the particles with energy E of the source dv is τ×dv, and τ is the emission rate of the particles with energy E in a unit volume of V in the direction of 4π.

[0049] Let cos(ω)×φ be the solid angle of the end face of the detector relative to dv, and sin(ω)dω×dφ be the small amount of cos(ω)×φ. It is assumed that the particles emitted from dv within the solid angle of sin(ω)dω×dφ do not undergo energy loss to reach the upper surface of the detector, and the full-energy peak detection efficiency in the detector is f.eff (E, ω, φ) is the fraction of particles emitted from dv in the solid angle sin(ω)dω x dφ that penetrate the shield, including self-absorption in the source, without energy loss att (E, ω, φ). Then the detection efficiency of a particle of energy E emitted from source V at the front face of the detector is

[0050]

[0051] Similarly, let cos(ω') x φ' be the solid angle subtended by the side of the detector to dv, and sin(ω')dω' x dφ' be an infinitesimal of cos(ω') x φ'. Then the detection efficiency of a particle of energy E emitted from source V at the side of the detector is

[0052]

[0053] The detection efficiency of a particle of energy E emitted from source V by the detector is

[0054]

[0055] From equations (1), (2) and (3), it can be seen that in order to obtain the detection efficiency ε eff (E) of a photon of energy E emitted from an arbitrary volume source V, the following work needs to be done: 1) determine the geometric model and material model of the detector and the volume source; 2) calculate the straight-through transmission fraction f att (E, ω, φ) of a particle of energy E emitted in any direction from an arbitrary point dv in volume V to the detector, i.e. calculate the length of material passed through by each ray on its path to the detector; 3) calculate the detection efficiency f eff (E, ω, φ) of a particle of energy E emitted in any direction from an arbitrary point dv in volume V at the detector, i.e. characterize the detector; 4) calculate the integrals shown in equations (1) and (2).

[0056] In order to realize the sourceless efficiency calibration of an arbitrary volume source, the following work needs to be done: establish the geometric model and material model of the detector; characterize the detector, i.e. establish the angular distribution of the detection efficiency of a ray emitted from an arbitrary point in space; realize the computerized rapid three-dimensional modeling of the volume source; and realize the rapid integration of equations (1) and (2).

[0057] The present application has the following advantages over the experimental calibration using passive efficiency calibration: no radioactive source is needed for efficiency calibration, no radioactive source needs to be managed and disposed, and no radioactive source license is needed. The laboratory is avoided from being contaminated, and the cost is saved; the precision is high, time is saved, and reliable results can be obtained in a short time. The powerful geometry modeling capability is suitable for any geometry. In addition to being suitable for conventional samples, it is also suitable for calibrating unconventional or difficult-to-handle samples such as cement, steel, gas, soil, air, filters, resins, etc. It is suitable for samples of any material, any density, and any size and shape. It is suitable for any base material and shielding material, any collimator and shielding, and sample preparation time is saved. The software accurately models and calibrates according to the sample conditions, and a large amount of time is not spent on sample preparation. Large-scale sample measurement can be performed to avoid the problem that sampling may cause the sample to be not representative. Fast measurement can save time and cost of sampling, packaging, transportation, sample preparation, and laboratory measurement.

[0058] In the radioactive waste classification detection method of the present application, the passive efficiency calibration module can call the corresponding efficiency calibration factor from the passive efficiency calibration factor database according to the density information, and combine the total activity nuclear signal and the nuclear signal of the nuclide activity to obtain the total activity concentration and the nuclide activity concentration, greatly facilitating the batch processing of the radioactive waste of the present application, saving a large amount of pre-processing time, and having high measurement accuracy, time saving, and reliable results can be obtained in a short time.

[0059] By implementing the present application, the following beneficial effects are achieved:

[0060] The radioactive waste classification detection method of the present application uses the weight information and the density information of the radioactive waste, combines the total activity nuclear signal of the radioactive waste for primary classification, and preliminarily and quickly judges whether it is extremely low level radioactive waste. If it is not clear whether it is extremely low level radioactive waste, it is combined with the nuclear signal of at least one nuclide activity concentration of the radioactive waste for secondary classification to determine whether the radioactive waste that is not clear in the primary classification is extremely low level radioactive waste. The radioactive waste can be quickly and batch classified, which is convenient for subsequent waste treatment.

[0061] It can be understood that the above embodiments only express the preferred embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application; it should be pointed out that for ordinary skilled persons in the art, the above embodiments or technical features can be freely combined without departing from the concept of the present application, and a number of modifications and improvements can be made, which all belong to the protection scope of the present application, i.e. the embodiments described in "in some embodiments" can be freely combined with any of the above and below embodiments; therefore, any equivalent transformation and modification within the scope of the claims of the present application shall belong to the scope of the claims of the present application.

Claims

1. A method for classifying and detecting radioactive waste, characterized in that, Includes the following steps: S10: Obtain the weight and density information of the radioactive waste; S20: Obtain the total activity nuclear signal of the radioactive waste through a scintillator detector, and integrate the weight information, the density information, and the total activity nuclear signal to obtain the total activity concentration of the radioactive waste; wherein, the scintillator detector includes several NaI crystal units with a total volume greater than or equal to 16L; S30: Determine whether the total activity concentration exceeds the upper limit of the extremely low radioactivity level; If the total activity concentration exceeds the upper limit of the extremely low radioactivity level, proceed to step S40; if the total activity concentration is lower than or equal to the upper limit of the extremely low radioactivity level, determine that the radioactive waste is extremely low radioactivity level waste and end the process. S40: Obtain the nuclear signal of the activity of at least one nuclide of the radioactive waste through a semiconductor detector, and integrate the weight information, the density information and the nuclear signal to obtain the nuclide activity concentration of at least one nuclide of the radioactive waste; wherein, the semiconductor detector is a high-purity germanium detector or a zinc cadmium telluride detector. S50: Determine whether the activity concentration of the nuclide exceeds the upper limit of the extremely low radioactivity level. If the activity concentration of the nuclide exceeds the upper limit of the extremely low radioactivity level, the radioactive waste is determined to be low-level radioactive waste; if the activity concentration of the nuclide is lower than or equal to the upper limit of the extremely low radioactivity level, the radioactive waste is determined to be extremely low-level radioactive waste. Specifically, based on the density information, the corresponding efficiency scale factor is retrieved from the passive efficiency scale factor database and combined with the total activity nuclear signal and the nuclide activity nuclear signal to obtain the total activity concentration and the nuclide activity concentration; the total activity nuclear signal is converted into total radioactive activity concentration and the nuclide activity nuclear signal is converted into nuclide activity concentration through gamma spectroscopy analysis.

2. The method for classifying and detecting radioactive waste according to claim 1, characterized in that, In step S10: the radioactive waste is placed into a shaping container and shaped into a regular shape. The volume information is measured and the weight information is obtained by weighing. The density information is calculated using the volume information and the weight information.

3. The method for classifying and detecting radioactive waste according to claim 1 or 2, characterized in that, The nuclides include 60 Co、 137 Cs、 54 Mn, 58 Co、 95 Nb, 51 Cr 95 Zr.

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