CN116953762A - Multifunctional multi-mode measuring method for large-volume radioactive waste barrel - Google Patents
Multifunctional multi-mode measuring method for large-volume radioactive waste barrel Download PDFInfo
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- 239000002901 radioactive waste Substances 0.000 title claims abstract description 66
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- 238000000691 measurement method Methods 0.000 claims abstract description 5
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- 238000001514 detection method Methods 0.000 claims description 39
- 239000011159 matrix material Substances 0.000 claims description 24
- 238000004364 calculation method Methods 0.000 claims description 21
- 230000005251 gamma ray Effects 0.000 claims description 11
- 230000002285 radioactive effect Effects 0.000 claims description 8
- 239000000126 substance Substances 0.000 claims description 8
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- 238000004088 simulation Methods 0.000 claims description 7
- 238000000342 Monte Carlo simulation Methods 0.000 claims description 6
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- 239000011358 absorbing material Substances 0.000 claims description 4
- 238000013461 design Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
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- 239000010410 layer Substances 0.000 description 22
- 239000000523 sample Substances 0.000 description 11
- 238000005303 weighing Methods 0.000 description 11
- 238000003466 welding Methods 0.000 description 10
- 230000000670 limiting effect Effects 0.000 description 9
- 230000005571 horizontal transmission Effects 0.000 description 8
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- 239000011229 interlayer Substances 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 3
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- 238000012937 correction Methods 0.000 description 3
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- FVAUCKIRQBBSSJ-UHFFFAOYSA-M sodium iodide Chemical compound [Na+].[I-] FVAUCKIRQBBSSJ-UHFFFAOYSA-M 0.000 description 3
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- 229910052793 cadmium Inorganic materials 0.000 description 1
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- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 238000009957 hemming Methods 0.000 description 1
- 230000003116 impacting effect Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- XKUYOJZZLGFZTC-UHFFFAOYSA-K lanthanum(iii) bromide Chemical compound Br[La](Br)Br XKUYOJZZLGFZTC-UHFFFAOYSA-K 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/02—Dosimeters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/36—Measuring spectral distribution of X-rays or of nuclear radiation spectrometry
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
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Abstract
The invention belongs to the technical field of radioactive waste measurement in nuclear facilities, and particularly relates to a multifunctional multi-mode measurement method for a large-volume radioactive waste barrel. Comprises the following steps: step 1: placing a 200L or 400L waste bin at a designated position of a loading platform; step 2: selecting a scanning mode of the waste bin with a corresponding size in measurement and control software according to the identification result of the size of the waste bin; step 3: clicking "start measurement" in measurement and control software, and performing gamma energy spectrum measurement on the waste bin after "configuration parameter confirmation", wherein the dose rate meter is used for completing the dose rate measurement on the surface of the waste bin and at the position of 1 m; step 4: analyzing data; step 5: the scanning flow has the beneficial effects that: by the multifunctional multi-mode measuring method, the problems that when the radioactive waste bin is currently used for measuring, only a single-size waste bin can be scanned and measured, and the analysis result of activity or activity concentration is overlarge under the condition that the distribution of nuclides of the waste bin is uneven can be effectively solved.
Description
Technical Field
The invention belongs to the technical field of radioactive waste measurement in nuclear facilities, and particularly relates to a multifunctional multi-mode measurement method for a large-volume radioactive waste barrel.
Background
The solid radioactive waste produced by nuclear facilities mainly comprises technical waste, waste resin, concentrated solution and the like, and is stored in a large volume of 200L or 400L steel drum or cement drum, and the total activity is obtained by measuring gamma energy spectrum from outside the waste drum in a layered scanning mode and divided by the net weight of the waste drum (subtracting empty drum mass) to obtain the activity concentration (also called specific activity) in the drum, namely the activity A is calculated according to the following formula:
wherein N represents the net peak area count of the gamma-ray full energy peak with the energy of E; p represents the gamma-ray branching ratio of a radionuclide energy E; t represents the measured live time of the gamma energy spectrum; epsilon represents the detection efficiency of the detector for gamma rays with energy E. At present, the existing measuring device can only scan and measure a waste bin with one size, and is limited by a scanning mode and measuring precision, on one hand, the existing method gives a waste bin activity analysis result under the premise that the radioactivity distribution in the bin is uniform, and when the radioactivity distribution in the bin is not uniform, the activity measurement result has deviation, especially the waste bin with radioactive hot spots; on the other hand, if the hot spot activity is larger and is close to the barrel wall, the energy spectrum type detector may be blocked, so that the dead time is too long, a reasonable gamma energy spectrum cannot be given, and the deviation of the activity analysis result is further increased.
Disclosure of Invention
The invention aims to provide a multifunctional multi-mode measuring method for a large-volume radioactive waste barrel, which can realize various measuring functions such as top surface dosage rate, side surface dosage rate, bottom surface dosage rate, dosage rate measurement at the position of 1m on the side surface, radioactivity measurement in the barrel, hot spot positioning in the barrel and the like of the waste barrel, and particularly improve the analysis result of activity or activity concentration of the waste barrel with radioactive hot spots.
The technical scheme of the invention is as follows: a multi-functional multi-mode measurement method for a large-volume radioactive waste bin, comprising the steps of:
step 1: placing a 200L or 400L waste bin at a designated position of a loading platform;
step 2: selecting a scanning mode of the waste bin with a corresponding size in measurement and control software according to the identification result of the size of the waste bin;
step 3: clicking "start measurement" in measurement and control software, and performing gamma energy spectrum measurement on the waste bin after "configuration parameter confirmation", wherein the dose rate meter is used for completing the dose rate measurement on the surface of the waste bin and at the position of 1 m;
step 4: analyzing data;
step 5: the scanning process is completed.
Step 1 is to place a 200L or 400L waste barrel on a loading platform through a clamping vehicle, and place the 200L or 400L waste barrel on a specified position by utilizing the design of different groove widths and depths of a sample placing base.
The step 2 comprises a point scanning mode, when the measuring device is operated, the rotary supporting module does not operate, the radioactive waste barrel does not rotate, the lifting unit does not operate, the detector does not move, and the measuring is performed in a static state, and the mode is mainly applied to fine scanning measurement with special hot spots in the barrel and quality control measurement.
Step 2 include vertical scanning mode, when measuring device operates, rotatory supporting module does not operate, and the radioactive waste bucket does not rotate, and the elevating unit operation, the detector is measured in the vertical lift of a plurality of high positions, and this mode is mainly applied to the radioactive waste bucket measurement that the radioactivity level distributes comparatively evenly in the bucket.
Step 2 includes layering scanning mode, and when measuring device was operated, rotatory supporting module was operated, and radioactive waste bucket was rotatory at uniform velocity in succession, and lifting unit was operated, and the detector was measured in the vertical lift of a plurality of high positions, and this mode is mainly applied to the radioactive waste bucket measurement of the uneven radioactivity level distribution in the bucket.
Step 2 includes spiral scanning mode, and when measuring device was operated, rotatory supporting module was operated, and radioactive waste bucket was rotatory evenly in succession, and the elevating unit was operated, and the detector was measured in the continuous lift in vertical direction, and this mode is mainly applied to the radioactive waste bucket measurement that requires full coverage scanning.
The step 4 comprises the steps of:
(1) Whole barrel numerical calculation method
In a layered scanning mode or a helical scanning mode, the field of view function F (x) 0 ) And the measured dimensions of the waste bin active area, waste bin cement-fixing or absorbing substance and waste bin wall thickness, the in-bin activity a is obtained from the formula:
wherein N represents the net peak area count of the gamma-ray full energy peak with the energy of E; p represents the gamma-ray branching ratio of a radionuclide energy E; t represents the measured time of activity of the gamma energy spectrum；ε(x 0 ) The detection efficiency of the detector on gamma rays with energy E at an efficiency scale point is shown; r, d P and dW Represents the waste bin radius, the thickness of the cement fixing or absorbing substance and the waste bin wall thickness; mu (mu) M 、μ P 、μ W A linear attenuation coefficient for gamma rays of energy E representing the waste bin active area, the waste bin cement fixed or absorbing material and the waste bin wall; v is the waste bin volume.
(2) Whole barrel Meng Ka simulation calculation method
In the layering scanning mode or the spiral scanning mode, all parameters except N, P and t in the formula, namelyAre determined by Monte Carlo simulation calculations as the detection efficiency ε.
(3) Efficiency matrix method
In the layered scanning mode, gamma energy spectrum type detectors are adopted to measure layer by layer or simultaneously measure multiple layers, the counting rate of gamma rays of each layer is obtained, a matrix relation is established by combining the detection efficiency of the detectors, the radioactivity of each layer is calculated by solving the matrix, and a barrel inner activity measuring result is obtained according to the following steps:
wherein, subscripts 1 to n represent hierarchical numbers; epsilon ij The detection efficiency of the radioactivity of the j th layer is the detection efficiency of the detector when scanning to the i th layer.
(4) Single detector hot spot analysis
In the layered scanning mode, according to the fluctuation condition of the dose rate or the counting rate as a prompt, judging whether a hot spot exists or not, and further estimating and positioning the position of the hot spot, firstly, easily determining the angle of the hot spot, namely the peak and the trough of the fluctuation of the dose rate or the counting rate, wherein the angle corresponding to the peak is the angle of the hot spot, when the difference of the dose rate or the counting rate of the peak and the trough exceeds a certain threshold value, the hot spot is considered to exist at the moment, the hot spot positioning analysis is required, the distance between the hot spot and the central axis of the barrel, namely the radius of the hot spot is positioned, and the distance between the hot spot and the surface of the detector can be expressed as
wherein ,dx ＝d 0 -p i cos(β i +θ)，d y ＝p i cos(β i +θ)，d z =h denotes the height of the hot spot in the vertical direction relative to the detector center.
This distance consists of the following parts, the length l through the active area a Length through cement-fixing or absorbing substance l s Length l through the wall of the tub w And shielding length of collimation hole l c ：
wherein ,
theoretically, the detector measures the count:
wherein the exponential term product represents the attenuation of each portion, K (d n ) Is a collimator response function comprising a portion U (d n ) And a portion C (d) passing through the collimator without scattering n ) The sum of the two parts shows that the materials such as lead of the collimation hole, etc. are strong in shielding gamma rays, the attenuation of the gamma rays is very strong, C (d) n ) The contribution of U (d) is small n ) For K (d) n ) Is greater, which can be expressed as
wherein ,
S det the opening area of the detector in the collimation hole is defined;
let the effective radius of the collimator beThen
Thus, C (d) n ) Can be expressed as
To this end, the method is composed of C (d n) and U(dn ) Can obtainK(d n ) And then the theoretical count N (theta) and the theoretical count rate Z (theta) =N (theta)/t measured by the detector can be obtained, and then the count rate N (theta) is obtained according to the actually measured gamma energy spectrum, and after the theoretical count N (theta) and the theoretical count rate Z (theta) =N (theta)/t are normalized according to the maximum value, the theoretical count N (theta) and the theoretical count rate Z (theta) =N (theta)/t are compared with each other according to the radius length of the hot spot to minimize χ 2 I.e. solving the following minimum by iterative method
Obtaining relevant parameters, and positioning the hot spot to obtain the radius p where the hot spot is located i Finally by
The activity and activity concentration of the radioactive waste can be obtained when the hot spot is considered in the radioactive waste can;
(5) Double detector hot spot analysis method
In the layered scanning mode, at least two groups of gamma energy spectrum type detectors are used for simultaneously estimating and positioning hot spots in the barrel, when the waste barrel rotates, the hot spots also rotate along with the waste barrel, the hot spots can be regarded as annular sources, the radius of the annular sources is the radius of the hot spots, and the counting rate of the two detectors A, B on the same waste barrel can be expressed as
Z A ＝A·P·ε A (p i )
Z B ＝A·P·ε B (p i )
Wherein italic A indicates hot spot activity, p i Representing the radius at which the hot spot is located, the relative detection efficiency function may be defined as
I.e. Z B /Z A The value of (2) should be the relative detection efficiency function F (p i ) One point on the curve is marked with a respective scale on the detector A, B to obtain a relative detection efficiency function F (p i ) The curve is formed by a curve of the curve,if F (p) i ) Is a monotonic function, and passes through the counting rate ratio Z of the detector B and the detector A B /Z A The radius p of the annular line source can be uniquely determined i Thereby accurately obtaining the full-energy peak detection efficiency epsilon under the radius A (p i ) Or epsilon B (p i ) Further, the activity A was calculated.
The invention has the beneficial effects that: by the multifunctional multi-mode measuring method, the problems that only a single-size waste bin can be scanned and measured when the current radioactive waste bin is measured and the deviation of the analysis result of activity or activity concentration is overlarge under the condition of uneven distribution of nuclides of the waste bin can be effectively solved, the measuring efficiency and measuring precision of the radioactive waste bin in nuclear facilities can be effectively improved, and the method has a large market application prospect.
Drawings
FIG. 1 is a schematic view of a loading platform to which the present invention is applied;
FIG. 2 shows that the bottoms of waste drums of different sizes, such as 200L and 400L, are provided with curled edges, namely h1 of the waste drums of different sizes are different;
FIG. 3 is a schematic view of the contact surface of the waste loading base, wherein arrows indicate 200L and 400L waste bottom hemming locating slots;
FIG. 4 is a schematic view of a horizontal drive unit with a horizontal movement function and a guiding and limiting module;
FIG. 5 is a schematic diagram of a gamma-ray spectral detector lifting unit and a dose rate meter positioning unit with vertical movement;
FIG. 6 is a schematic diagram of a top dose rate meter positioning unit;
FIG. 7 is a schematic diagram of a side three-set dose rate meter positioning unit;
FIG. 8 is a schematic view of a set of dose rate meter positioning units at side 1 m;
FIG. 9 is a simplified schematic diagram of a detection efficiency matrix;
FIG. 10 is a schematic diagram of a single detector hot spot analysis method.
In the figure: the device comprises a proximity switch 1, a bottom dose rate meter positioning unit 2, a servo motor 3, a sample holding base 4, a proximity switch 5, a rotary support 6, a weighing balance 7, a mechanical hard limit 8, a guide rail slider 9, a guide screw 10, a servo motor 11, a welding base 12, an electrical soft limit 13, a fixed foot seat 14, a clamp car guide device 15, a clamp car limit device 16, a drag chain 17, a welding body 18, a guide screw 19, a lifting platform 20, a fixed foot seat 21, a limit device 22, a servo motor 23, a dose rate meter positioning unit 24, a 25 gamma energy spectrum detection system 26, a bottom bracket 27, a servo motor 28, a support structure 29, a drag chain 30, a top dose rate meter 31, an anti-collision wheel 32, a limit device 33, a secondary servo motor 34, a primary servo motor 35, a primary support structure 36, a side dose rate meter 37, a servo cylinder 38, a servo cylinder 39, an anti-collision wheel 40, a secondary support structure 41, a limit device 42, a drag chain 43, a dose rate meter 44, a servo cylinder 45, a servo cylinder 46, a limit device 47 and a support structure 48.
Detailed Description
The invention will be described in further detail with reference to the accompanying drawings and specific examples.
The invention provides a multifunctional multi-mode measuring method for a large-volume radioactive waste barrel, which mainly comprises the following functions:
(1) Developing loading platforms suitable for waste barrels of different sizes, weighing the waste barrels, rotating the waste barrels during measurement, recording gamma energy spectrums and gamma dose rates of different layers, different angles and different positions by using at least two groups of gamma energy spectrum type detectors and at least four groups of gamma dose rate meters under the condition that the waste barrels rotate, and matching with a plurality of scanning modes such as point scanning, vertical scanning, layering scanning, spiral scanning and the like.
(2) The method adopts a whole barrel numerical value calculation method, a whole barrel Meng Ka simulation calculation method, an efficiency matrix method, a single-detector hot spot analysis method, a double-detector hot spot analysis method and the like to realize the measuring functions of measuring the top surface dosage rate, the side surface dosage rate, the bottom surface dosage rate, the dosage rate at the side 1m, the radioactivity in the barrel, the hot spot positioning in the barrel and the like of the waste barrel, and effectively improves the accuracy of the activity or activity concentration analysis result when the distribution of the kernel in the waste barrel is uneven.
The measuring device disclosed by the invention needs a plurality of modules to be matched with each other, so that the improvement of an analysis result and the improvement of performance are realized together.
A multifunctional multi-mode measuring device for a large-volume radioactive waste barrel mainly comprises a loading platform, a horizontal transmission unit, a gamma energy spectrum type detector lifting unit, a dose rate meter positioning unit, a top dose rate meter positioning unit, three lateral groups of dose rate meter positioning units and a group of dose rate meter positioning units at the position of 1m on the lateral side.
As shown in fig. 1, the loading platform mainly comprises a proximity switch 1, a bottom dose rate meter positioning unit 2, a servo motor 3, a sample placing base 4, a proximity switch 5, a rotary support 6 and a weighing balance 7. The proximity switch 1 and the proximity switch 5 are respectively arranged at the upper part of a loading platform shell at the side part of the sample placing base 4 and at the hollow position inside the rotary support 6, and are used for monitoring the loading and unloading state of the waste drum and identifying the size of the waste drum, the weighing balance 7 is arranged at the bottommost part of the loading platform, and is used for measuring the weight of the waste drum, the servo motor 3 and the rotary support 6 are arranged at the top platform of the weighing balance 7, the sample placing base 4 and the rotary support 6 are fixed by using screws, the servo drive 3 drives the rotary support 6 and the sample placing base 4 to bear the waste drum to rotate at a constant speed, and the bottom dose rate instrument positioning unit 2 is arranged at the hollow bottom position of the rotary support 6 and is used for fixing a bottom dose rate instrument.
As shown in fig. 4, the horizontal transmission unit mainly comprises a mechanical hard limit 8, a guide rail slide block 9, a screw rod 10, a servo motor 11, a welding base 12, an electric soft limit 13, a fixed base 14, a clamping vehicle guide device 15, a clamping vehicle limit device 16 and a drag chain 17. Wherein, loading platform installs in horizontal unit guide rail slider 9, drive lead screw 10 through servo motor 11 and drive loading platform horizontal migration, electric soft spacing 13 and mechanical hard spacing 8 are installed in horizontal drive unit both sides, guarantee the security of equipment, fixed foot rest 14 is installed in welding base 12 bottom, be used for horizontal unit whole leveling, drag chain 17 one side is located loading platform wire hole department, the opposite side is located driving motor wire hole department, armful clamp car guider 15 and armful clamp car stop device 16 are installed in horizontal drive unit and are close to servo motor 11 one side, be used for armful clamp car loading and unloading waste drum direction, and avoid armful clamp car to collide with horizontal unit.
As shown in fig. 5, the gamma energy spectrum detector lifting unit mainly comprises a welding main body 18, a screw rod 19, a lifting platform 20, a fixed foot seat 21, a limiting device 22, a servo motor 23, a dose rate meter positioning unit 24, a gamma energy spectrum detection system 25 and a bottom bracket 26. The gamma energy spectrum detection system 25 is placed on the lifting platform 20, a double-output speed reducer and a right-angle reverser are driven by the servo motor 23 to transfer torque to the double-screw rod, the lifting platform 20 is driven to move in a lifting manner, the fixed foot seat 21 is installed on the bottom support 26 for integrally leveling the lifting unit, the dose rate meter positioning unit 24 and the stand column of the welding main body 18 are fixed through screws, and the limiting device 22 is installed on the top and the bottom two sides of the stand column of the welding main body 18, so that the safety of equipment is ensured.
As shown in fig. 6, the top dose rate meter positioning unit mainly comprises a servo cylinder 27, a servo motor 28, a support structure 29, a drag chain 30, a top dose rate meter 31, a bump wheel 32 and a limiting device 33. Wherein, the supporting structure 29 and the stand column of the welding main body 18 are fixed by screws, the servo motor 28 drives the dose rate meter to rotate, the servo motor cylinder 27 drives the dose rate meter to move up and down so as to be suitable for measuring the dose rate of the top surface of the waste bin with different sizes, and the anti-collision wheel 32 protects the dose rate meter from being in direct contact or collision with the waste bin.
As shown in fig. 7, the side three-group dose rate meter positioning unit mainly comprises a second-stage servo motor 34, a first-stage servo motor 35, a first-stage supporting structure 36, a side dose rate meter 37, a servo cylinder 38, a drag chain 39, an anti-collision wheel 40, a second-stage supporting structure 41 and a limiting device 42. The primary support structure 36 and the upright post of the welding main body 18 are fixed by screws, the primary servo motor 35 drives the secondary support structure 41 to perform primary rotation, the secondary servo motor 34 drives the side surface dose rate meter 37 to perform secondary rotation, and the servo motor cylinder 38 pushes the side surface three groups of dose rate meters to perform lifting movement so as to be suitable for measuring the side surface dose rate of waste barrels with different sizes, and the anti-collision wheel 40 protects the dose rate meters from being in direct contact or collision with the waste barrels.
As shown in fig. 8, the set of dose meter positioning units at the side 1m mainly comprises a drag chain 43, a dose meter 44 at the side 1m, a servo cylinder 45, a servo cylinder 46, a stop device 47 and a support structure 48. The supporting structure 48 and the upright post of the welding main body 18 are fixed by screws, the servo electric cylinder 46 drives the dose rate meter to horizontally move, and the servo electric cylinder 45 drives the dose rate meter to lift and move so as to adapt to dose rate measurement at 1m of the side surfaces of waste barrels with different sizes.
The loading platforms of the large-volume radioactive waste barrels with different sizes such as 200L and 400L can be assembled and disassembled, and the accurate positioning, distinguishing, rotating and weighing of the waste barrels with different sizes are realized.
(1) According to the requirements of national standards EJ 1042-2014 'low and horizontal radioactive solid waste container steel barrels' and EJ 1042-1996 'low and horizontal radioactive solid waste packaging container steel barrels' (although the old waste barrels are abandoned and the sizes of the old waste barrels meet the standard), the bottoms of the waste barrels with different sizes such as 200L and 400L are provided with supporting curled edges, and the distances between the radioactive waste in the barrels and the plane of the bearing curled edges are different (namely h) 1 Different). The loading platform has large-volume radioactive waste drum loading bases of different sizes according to the waste drum diameter and h 1 The bottom gamma dose rate meter is consistent with the bottom distance of radioactive waste in the waste barrels with different sizes, and the measurement results of the bottom gamma dose rate meter are comparable to the waste barrels with different sizes and the waste barrels with the same size. The sinking of loading base has not only guaranteed that the barrel head of different size waste barrels is in same horizontal plane, still realizes spacing to the loading of different size waste barrels, reduces the eccentric degree when its is rotatory, has important effect to barrel internal activity measurement and hot spot location. The sinking depth of the loading base can be replaced according to the size of the waste bin.
(2) The loading platform is provided with automatic distinguishing sensors for waste barrels of different sizes, a proximity switch is respectively arranged on a rotary supporting table in the middle of a loading base and a protective cover shell on the side face, the sizes of the waste barrels are confirmed by judging whether the waste barrels exist or not, and a double signal is 400L and a single signal is 200L. The automatic discriminating function may be realized by a sensor having a distance measuring function instead.
(3) The lower part of the loading base of the loading platform is provided with a rotary supporting module, and the rotation of the waste barrel is realized through a motor, gears and the like. During measurement, the rotation of the waste bin plays an important role in the measurement of the activity in the bin and the positioning of hot spots.
(4) The loading base and the rotary supporting module of the loading platform are arranged below the weighing module which is used for weighing and has a flexible connection mode, and when the waste barrel is loaded and unloaded, the flexible connection mode generates certain shaking, so that the influence of the loading and unloading impact force on the weighing sensor is reduced, the damage is prevented, and the loading and unloading operation can not influence the positioning of the loading platform. The weighing module gives the waste bin weight, which is an integral parameter in calculating the activity concentration of the radioactive waste bin.
2. The horizontal transmission unit is provided with a horizontal movement function and a guiding and limiting module, so that the waste bin is close to or far from the gamma energy spectrum type detector.
The loading platform is arranged on the horizontal transmission unit, the motor is used for providing driving force, the screw rod is rotated, horizontal movement is realized along the guide rail, the distance between the waste bin and the gamma energy spectrum type detector is adjusted, and the effective stroke is large enough, so that the measuring device is suitable for the waste bin measuring requirement of a wider dosage rate range.
The garbage can loading and unloading end of the horizontal transmission unit is provided with the clamping vehicle guiding and limiting module, when the clamping vehicle loads and unloads the garbage can, the clamping vehicle is convenient to align with the loading platform, and the clamping vehicle is prevented from impacting the horizontal transmission unit, so that the mechanical damage is caused. The guiding and limiting module is of great importance to loading and unloading of the waste barrels, so that the horizontal transmission unit and the loading platform are prevented from moving or being damaged due to loading and unloading of the waste barrels, and the measuring accuracy of the measuring device is further guaranteed.
3. And the gamma energy spectrum type detector lifting unit with the vertical movement function realizes the lifting movement of the energy spectrum type detector in the vertical direction.
At least two groups of gamma energy spectrum type detectors are required to be placed on a gamma energy spectrum type detector lifting unit, the gamma energy spectrum type detectors can be high-purity germanium detectors, tellurium zinc cadmium detectors, sodium iodide detectors or lanthanum bromide detectors and the like, the gamma energy spectrum type detectors are provided with shielding chambers mainly made of lead materials and collimators, the shielding chambers can reduce the influence of environmental background on detection limits, the collimators can reduce the influence of high-activity radioactive waste barrels on the detector performance, particularly the dead time, the modules all have requirements on the bearing capacity of the lifting unit, the lifting unit adopts a motor to provide driving force, torque is transmitted to a double-screw rod through a double-output speed reducer, and the double-screw rod drives nuts to lift or lower a lifting platform. The double lead screw and the double guide rail are used as the structural form of the execution system, the transmission is stable and accurate, the efficiency is high, the service life is long, the maintenance is simple, and the moving precision of the gamma energy spectrum type detector in the vertical direction is ensured.
4. The dose rate meter positioning unit with the rotating and translating functions realizes that at least two groups of dose rate meters approach to the surfaces of the large-volume radioactive waste barrels with different sizes and one group of dose rate meters reach a designated position which is far from the surface of the waste barrel by 1m, and realizes the measurement of the top surface dose rate, the side surface dose rate, the bottom surface dose rate and the dose rate at the side surface 1 m.
(1) At least one group of dose rate meters are arranged at the top of the radioactive waste barrel, the partial positioning unit adopts a cantilever rotation fit Z-axis lifting mode, and the dose rate meters are pushed to the top of the radioactive waste barrel according to the distinguishing results of the radioactive waste barrels with different sizes and large volumes to measure the top surface dose rate. The part of the positioning unit also adopts an anti-collision module, so that the dose rate meter is prevented from being damaged by colliding with the top of the waste bin.
(2) At least three groups of dose rate meters are arranged on the side surface of the radioactive waste barrel, the partial positioning unit adopts a mode of primary cantilever rotation, secondary cantilever rotation and Z-axis lifting, and the dose rate meters are pushed to the side surface of the radioactive waste barrel according to the distinguishing results of the radioactive waste barrels with different sizes and large volumes, so that the dose rate of the side surface is measured. The part of the positioning unit also adopts an anti-collision module, so that the dose rate meter is prevented from being damaged due to collision with the side surface of the waste bin.
(3) At least one group of dose rate meters is arranged on the bottom of the radioactive waste bin, i.e. the rotary support table in the middle of the loading base of the loading platform, which dose rate meters do not need to be moved to ensure that they are consistent with the bottom distances of different sized waste bins, saving space, reducing mechanical complexity and saving costs, but not without increasing the bottom dose rate meter movement module.
(4) At least one group of dose rate meters are arranged on one side of the lifting unit far away from the radioactive waste barrel, the dose rate meters are pushed to a position far away from the surface of the waste barrel by translation, and the movement of the height center position of the radioactive waste barrel with different sizes and large volumes is realized by matching with the Z-axis lifting mode, so that the dose rate at the position of 1m on the side surface is measured.
The positioning unit of the dose rate meter can be used for measuring the surface dose rate and the 1m dose rate of a large-volume radioactive waste barrel with the same size as 200L and 400L, and meets the requirements of national standard GB 11806-2019 on dose rate measurement.
5. Based on the dose rate measurements, an optimal measurement distance of the waste bin is selected or determined by the horizontal movement unit. The dose rate measurement may also be used to evaluate the radioactivity measurement in the bucket, especially when the radioactivity distribution in the waste bucket is relatively uniform, or when there is a single hot spot.
In the national standard GB 11806-2019, the radioactive waste bin is required to have a dosage rate of not more than 2mSv/h and in special cases not more than 10mSv/h at any point on the outer surface of the waste bin during transportation, so that nuclear facilities such as nuclear power plants, nuclear fuel element factories and post-treatment factories manage a large volume of radioactive waste bin by taking the dosage rate as a limit value. However, when the surface dose rate of the waste bin is so high, the gamma energy spectrum type detector is subjected to radiation irradiation exceeding the processing capacity of the waste bin, the gamma energy spectrum type detector is possibly blocked, the dead time is too large to give a reasonable gamma energy spectrum, generally speaking, the maximum dose rate which can be borne by the gamma energy spectrum type detector is about 100 mu Sv/h because the gamma energy spectrum type detector is not excessively large and the gamma energy spectrum is not distorted, and therefore, the gamma energy spectrum type detector is provided with a shielding chamber mainly made of lead materials and a collimator, the collimator can reduce the influence of the high-activity radioactive waste bin on the detector performance, especially the dead time.
When the internal activity of the waste bin is obtained through various scanning modes and various activity calculation methods, the surface dose rate and 1m dose rate measurement can be calculated through Monte Carlo simulation calculation or analysis formulas according to the type and the characteristics of the waste bin to be measured, and particularly, the radioactivity distribution in the waste bin is uniform, or when a single hot spot exists, the waste bin can be compared and evaluated with the dose rate measurement result.
6. The rotary supporting module and the lifting unit of the loading platform jointly realize a plurality of scanning modes such as point scanning, vertical scanning, layering scanning, spiral scanning and the like.
The lifting unit can realize the vertical movement of the gamma energy spectrum type detector, the rotary supporting module of the loading platform can realize the selection of the radioactive waste barrel, and the invention jointly realizes a plurality of scanning modes such as point scanning, vertical scanning, layered scanning, spiral scanning and the like through the cooperation between the two.
The multiple scanning modes of the invention are the indispensable measuring modes for measuring the activity in the barrel and locating the hot spot.
7. The barrel internal activity measurement and the hot spot positioning are analyzed by adopting a barrel number calculation method, a barrel Meng Ka simulation calculation method, an efficiency matrix method, a single-detector hot spot analysis method, a double-detector hot spot analysis method and other methods.
According to the invention, through the multiple scanning modes, the multiple activity calculation methods such as the whole barrel numerical value calculation method, the whole barrel Meng Ka simulation calculation method, the efficiency matrix method, the single-detector hot spot analysis method, the double-detector hot spot analysis method and the like are integrated, the activity measurement and analysis can be realized, and the multiple methods are mutually compared, so that the radioactivity distribution uniformity degree can be primarily judged, and the radioactivity hot spots in the barrel can be estimated and positioned.
A multi-functional multi-mode measurement method for a large-volume radioactive waste bin, comprising the steps of:
step 1: the 200L or 400L waste bucket is placed on the loading platform through the holding and clamping vehicle, and the 200L or 400L waste bucket is placed at a specified position by utilizing the design of different groove widths and depths of the sample placing base 4.
Step 2: and the scanning mode of the waste bin with the corresponding size is selected in the measurement and control software by utilizing the recognition results of the proximity switch 1 and the proximity switch 5 on the size of the waste bin, and the scanning mode is specifically described as follows:
the measurement and control software of the waste bin measuring device mainly comprises modules of parameter setting, measurement control, data analysis, data management, report printing, alarm management and the like. In the measurement control module, the waste bin number, the content, the scanning mode and the like can be set, and the waste bin specification can be automatically judged by the measurement device.
(1) The point scanning mode means that when the measuring device is operated, the rotary supporting module does not operate, the radioactive waste barrel does not rotate, the lifting unit does not operate, the detector does not move, and the measuring is carried out in a static state. This mode is mainly applied to fine-scan measurement with special hot spots in the bucket, and quality control measurement.
(2) The vertical scanning mode means that when the measuring device is operated, the rotary supporting module does not operate, the radioactive waste barrel does not rotate, the lifting unit operates, and the detector vertically lifts at a plurality of height positions to measure. The mode is mainly applied to radioactive waste barrel measurement with uniform radioactive level distribution in the barrel.
(3) The layered scanning mode is that when the measuring device operates, the rotary supporting module operates, the radioactive waste barrel continuously rotates at a constant speed, the lifting unit operates, and the detector vertically lifts at a plurality of height positions for measurement. The mode is mainly applied to radioactive waste barrel measurement with uneven radioactive level distribution in the barrel;
(4) The spiral scanning mode means that when the measuring device operates, the rotary supporting module operates, the radioactive waste barrel continuously and uniformly rotates, the lifting unit operates, and the detector continuously lifts in the vertical direction to measure. This mode is mainly applied to radioactive waste bin measurements requiring full coverage scanning.
Step 3: clicking "start measurement" in measurement and control software, after "configuration parameter confirmation", moving the loading platform with the waste bin to a preset measurement position under the drive of the horizontal unit servo motor 16 and the screw rod 11, moving each dose rate meter to the preset dose rate measurement position under the action of the servo motors 28, 34 and 35 and the servo cylinders 27, 38, 45 and 46, starting the sample placing base 4 to rotate at a constant speed, driving the lifting platform 20 by the servo motor 23, driving the whole gamma energy spectrum detection system 25 to lift according to a preset flow to perform gamma energy spectrum measurement, and completing the dose rate measurement on the surface of the waste bin and the position of 1m by the dose rate meters.
Step 4: the data analysis, optional waste bin activity analysis method is specifically described as follows:
(1) Whole barrel numerical calculation method
In a layered scanning mode or a helical scanning mode, the field of view function F (x) 0 ) And the measured dimensions of the waste bin active area, waste bin cement-fixing or absorbing substance and waste bin wall thickness, the in-bin activity a is obtained from the formula:
wherein N represents the net peak area count of the gamma-ray full energy peak with the energy of E; p represents the gamma-ray branching ratio of a radionuclide energy E; t represents the measured live time of the gamma energy spectrum; epsilon (x) 0 ) The detection efficiency of the detector on gamma rays with energy E at an efficiency scale point is shown; r, d P and dW Represents the waste bin radius, the thickness of the cement fixing or absorbing substance and the waste bin wall thickness; mu (mu) M 、μ P 、μ W A linear attenuation coefficient for gamma rays of energy E representing the waste bin active area, the waste bin cement fixed or absorbing material and the waste bin wall; v is the waste bin volume.
(2) Whole barrel Meng Ka simulation calculation method
In the layering scanning mode or the spiral scanning mode, all parameters except N, P and t in the formula, namelyAre determined by Monte Carlo simulation calculations as the detection efficiency ε.
(3) The efficiency matrix method is that, in the layered scanning mode, it is assumed that the radioactivity level distributions in the barrels are layered uniformly, that is, the radioactivity level distributions may be different between layers of different thicknesses, but the radioactivity level distributions are still relatively uniform within each layer alone. The detection efficiency of the detector for each layer is determined by Monte Carlo simulation calculation before measurement. Virtual layering is carried out on the waste barrel along the central axis of the waste barrel, the waste barrel is rotated at a constant speed to reduce the influence caused by uneven matrix density and radioactivity distribution, gamma-energy spectrum type detectors are adopted to measure layer by layer or measure multiple layers simultaneously, the counting rate of gamma rays of each layer is obtained, a matrix relation is established by combining the detection efficiency of the detectors, the radioactivity of each layer is calculated by solving the matrix, and finally the activity measuring result in the barrel is obtained according to the following steps:
Wherein, subscripts 1 to n represent hierarchical numbers; epsilon ij The detection efficiency of the radioactivity of the j-th layer is improved when the detector scans to the i-th layer; a is that i And A is the activity of the radionuclide analyzed in each layer and the whole barrel, respectively; n (N) i Clean counts of the characteristic energy peaks measured when the detector scans to the ith layer; p is the branching ratio of the gamma rays characteristic of the radionuclide being analyzed; t is the time of liveness measured for each layer. The traditional method is to directly superpose and sum each layer of the waste barrel after independent analysis, and the efficiency matrix method is basically used without considering interlayer crosstalkIt is understood that, in theory, solving the efficiency matrix equation by using the iterative algorithm can effectively subtract the influence of the interlayer crosstalk, but the result is still affected by the crosstalk.
Before the efficiency calibration, the Monte Carlo method is adopted to simulate and calculate the detection efficiency under the conditions of different layering numbers, different energies and different matrix densities to form an efficiency matrix database, the current layer and crosstalk layer detection efficiency functions taking the matrix density and the gamma ray energy as independent variables under different layering conditions are obtained by utilizing multi-element nonlinear fitting, the detection efficiency coefficient matrix under the condition of any combination of the matrix density and the gamma ray energy is constructed, the influence of interlayer crosstalk is corrected and evaluated, and the activity or activity concentration of the radionuclide in the whole barrel is estimated.
(4) Single detector hot spot analysis
In the layered scanning mode, whether a hot spot exists is judged according to the fluctuation condition of the dose rate or the counting rate as a prompt, and then the position of the hot spot is estimated and positioned. Firstly, it is easy to determine that the angle of the hot spot, namely, the peak and the trough of the fluctuation of the dosage rate or the counting rate are generally 180 degrees apart, the angle corresponding to the peak is the angle of the hot spot, and when the dosage rate or the counting rate difference of the peak and the trough exceeds a certain threshold, the hot spot is considered to exist at the moment, and the hot spot positioning analysis is needed. For the distance between the hot spot and the central axis of the barrel, namely the radius of the hot spot, the positioning is relatively complex.
The distance of the hot spot from the detector surface can be expressed as
wherein ,dx ＝d 0 -p i cos(β i +θ)，d y ＝p i cos(β i +θ)，d z =h denotes the height of the hot spot in the vertical direction relative to the detector center.
In the formula, the center of the front surface of the detector is taken as an origin, the connecting line of the center of the detector and the center of the barrel is taken as an x axis, the radial direction of the barrel is taken as a y axis, the height direction of the barrel is taken as a z axis, and dx, dy and dz respectively represent the projection lengths of hot spots in the directions of the x axis, the y axis and the z axis; d0 represents the distance of the probe from the centre of the barrel; di represents the distance of the detector from the hot spot; pi and βi represent the hot spot radius and initial angle; θ represents a barrel rotation angle; h is the height of the hot spot relative to the detector.
This distance consists of the following parts, the length l through the active area a Length through cement-fixing or absorbing substance l s Length l through the wall of the tub w And shielding length of collimation hole l c ：
/>
wherein ,
in the formula, the front surface center of the detector is taken as an origin, the connecting line of the detector center and the barrel center is taken as an x axis, the radial direction of the barrel is taken as a y axis, the height direction of the barrel is taken as a z axis, and d 0 Representing the distance of the probe from the centre of the barrel; d, d i Representing the distance between the detector and the hot spot; r is R col 、L col Respectively representing the aperture radius and depth of the collimator; d, d col Indicating the same extension line as d of the collimator hole edge connecting line x The distance between the intersection point of the straight lines and the center of the front surface of the detector; θ represents a barrel rotation angle; alpha represents an included angle between the central connecting line of the hot spot and the front surface of the detector and the x axis; d, d s 、d w Respectively representing the shield thickness and the tub thickness;r represents the barrel outer radius.
Theoretically, the detector measures the count:
wherein the exponential term product represents the attenuation of each portion, K (d i ) Is a collimator response function comprising a portion U (d i ) And a portion C (d) passing through the collimator without scattering i ) And the sum of the two parts. Obviously, the materials such as lead of the collimation hole have strong shielding to gamma rays, the attenuation of the gamma rays is very strong, and C (d) i ) The contribution of U (d) is small i ) For K (d) i ) Is greater, which can be expressed as
wherein , S det is the opening area of the detector in the collimation hole.
Wherein b represents the distance between the center of the collimating aperture circle and the center of the projection circle of the hot spot on the plane of the detector through the collimator; r is R k Representing the radius of the projected circle; g represents the distance between two intersection points of the collimation hole circle and the projection circle; delta 1 Representing an included angle of an effective detection area by taking the center of the collimation hole circle as a round point; delta 2 Representing an included angle of an effective detection area by taking the center of a projection circle as a round point; s is S 1 In the effective detector area, the line segment g deviates to the area of one side of the projection circle; s is S 2 The effective detector area is shown with the line segment g being offset to the area on one side of the collimation hole circle.
Let the effective radius of the collimator beThen
in the formula ,indicating the same extension line as d of the collimator hole edge connecting line x The effective distance between the intersection point of the straight lines and the center of the front surface of the detector; />Indicating the effective shielding length of the collimation holes.
Thus, C (d) i ) Can be expressed as
To this end, the method is composed of C (d i) and U(di ) K (d) i ) And then the theoretical count N (theta) and the theoretical count rate Z (theta) =N (theta)/t measured by the detector can be obtained, and then the count rate N (theta) is obtained according to the actually measured gamma energy spectrum, and after the theoretical count N (theta) and the theoretical count rate Z (theta) =N (theta)/t are normalized according to the maximum value, the theoretical count N (theta) and the theoretical count rate Z (theta) =N (theta)/t are compared with each other according to the radius length of the hot spot to minimize χ 2 I.e. solving the following minimum by iterative method
Obtaining relevant parameters, and positioning the hot spot to obtain the radius p where the hot spot is located i Finally by
The activity and activity concentration in the radioactive waste vat when the hot spot is considered can be determined.
(5) The dual detector hot spot analysis method is characterized in that at least two groups of gamma energy spectrum type detectors are used for simultaneously estimating and positioning hot spots in a barrel in a layered scanning mode. When the waste bin rotates, the hot spot also follows the rotation, and the hot spot can be regarded as an annular source, and the radius of the annular source is the radius of the hot spot. The count rate of two detectors A, B for the same waste bin can be expressed as
Z A ＝A·P·ε A (p i )
Z B ＝A·P·ε B (p i )
Wherein italic A indicates hot spot activity, p i The radius where the hot spot is located is indicated, and P and ε are as before. Then, the relative detection efficiency function may be defined as
I.e. Z B /Z A The value of (2) should be the relative detection efficiency function F (p i ) One point on the curve is marked with a respective scale on the detector A, B to obtain a relative detection efficiency function F (p i ) Curve, if F (p i ) Is a monotonic function, and passes through the counting rate ratio Z of the detector B and the detector A B /Z A The radius p of the annular line source can be uniquely determined i Thereby accurately obtaining the full-energy peak detection efficiency epsilon under the radius A (p i ) Or epsilon B (p i ) Further, the activity A was calculated. However, in some cases, F (p i ) May not be monotonic and need to be determined according to the actual situation.
When layered scanning is performed, if interlayer crosstalk is considered, an efficiency matrix method can be combined to simulate to obtain an efficiency matrix of the detector A, B respectively, and further an iterative algorithm is used to reduce the influence of the crosstalk to obtain the correction of the activity of the detector A, B under the condition of considering hot spots respectively.
The analysis results of the two hot spot analysis methods can be further confirmed and evaluated by combining the spot scanning modes.
The method performs partial correction on the existing algorithm, more importantly, integrates the methods, gives an activity measurement result under the assumption that radioactivity is uniformly distributed, and then evaluates and positions the hot spot when the hot spot exists in the barrel by taking the measurement result of the dosage rate and the counting rate and the fluctuation condition as criteria, so as to give an activity measurement result containing the hot spot correction, thereby realizing the integration of various activity analysis methods.
Step 5: the scanning process is completed, the sample rest base 4, the dose rate meter positioning unit 24 and the lifting platform 20 are automatically reset, and the waste bin is unloaded by the holding and clamping vehicle.
Description of the embodiments
The measuring device disclosed by the invention needs a plurality of modules to be matched with each other, so that the improvement of an analysis result and the improvement of performance are realized together.
1) The loading platforms of the large-volume radioactive waste barrels with different sizes such as 200L and 400L can be assembled and disassembled, and the accurate positioning, distinguishing, rotating and weighing of the waste barrels with different sizes are realized.
2) The horizontal transmission unit is provided with a horizontal movement function and a guiding and limiting module, so that the waste bin is close to or far from the gamma energy spectrum type detector.
3) And the gamma energy spectrum type detector lifting unit with the vertical movement function realizes the lifting movement of the energy spectrum type detector in the vertical direction.
4) The dose rate meter positioning unit with the rotating and translating functions realizes that at least two groups of dose rate meters approach to the surfaces of the large-volume radioactive waste barrels with different sizes and one group of dose rate meters reach a designated position which is far from the surface of the waste barrel by 1m, and realizes the measurement of the top surface dose rate, the side surface dose rate, the bottom surface dose rate and the dose rate at the side surface 1 m.
5) Based on the dose rate measurements, an optimal measurement distance of the waste bin is selected or determined by the horizontal movement unit. The dose rate measurement may also be used to evaluate the radioactivity measurement in the bucket, especially when the radioactivity distribution in the waste bucket is relatively uniform, or when there is a single hot spot.
6) The rotary supporting module and the lifting unit of the loading platform jointly realize a plurality of scanning modes such as point scanning, vertical scanning, layering scanning, spiral scanning and the like.
7) The barrel internal activity measurement and the hot spot positioning are analyzed by adopting a barrel number calculation method, a barrel Meng Ka simulation calculation method, an efficiency matrix method, a single-detector hot spot analysis method, a double-detector hot spot analysis method and other methods.
Claims (10)
1. A multi-functional multi-mode measurement method for a large-volume radioactive waste bin, which is characterized by comprising the following steps:
step 1: placing a 200L or 400L waste bin at a designated position of a loading platform;
step 2: selecting a scanning mode of the waste bin with a corresponding size in measurement and control software according to the identification result of the size of the waste bin;
step 3: clicking "start measurement" in measurement and control software, and performing gamma energy spectrum measurement on the waste bin after "configuration parameter confirmation", wherein the dose rate meter is used for completing the dose rate measurement on the surface of the waste bin and at the position of 1 m;
step 4: analyzing data;
step 5: the scanning process is completed.
2. A method of multifunctional multi-mode measurement of a large volume radioactive waste vat according to claim 1, wherein: step 1 is to place a 200L or 400L waste barrel on a loading platform through a clamping vehicle, and place the 200L or 400L waste barrel on a specified position by utilizing the design of different groove widths and depths of a sample placing base.
3. The method of claim 1, wherein the step 2 includes a spot scanning mode, wherein the measuring device is operated in a non-operating mode, wherein the rotary support module is not operated, wherein the radioactive waste tank is not rotated, wherein the lifting unit is not operated, wherein the detector is not moved, wherein the measuring is performed in a stationary state, and wherein the mode is mainly applied to fine scanning measurement with a specific hot spot in the tank, and quality control measurement.
4. The method of claim 1, wherein the step 2 includes a vertical scanning mode, wherein the measuring device is operated in a vertical scanning mode, the rotary support module is not operated, the radioactive waste tank is not rotated, the lifting unit is operated, and the detector is vertically lifted at a plurality of height positions for measurement, and the mode is mainly applied to measurement of the radioactive waste tank with relatively uniform radioactive horizontal distribution in the tank.
5. The method of claim 1, wherein the step 2 includes a layered scanning mode, wherein the measuring device is operated, the rotary support module is operated, the radioactive waste barrel is continuously rotated at a constant speed, the lifting unit is operated, the detector is vertically lifted at a plurality of height positions to measure the radioactive waste barrel, and the mode is mainly applied to measuring the radioactive waste barrel with uneven distribution of the radioactive level in the barrel.
6. The method of claim 1, wherein the step 2 includes a spiral scanning mode, the rotary support module is operated when the measuring device is operated, the radioactive waste barrel is continuously and uniformly rotated, the lifting unit is operated, and the detector is continuously lifted in a vertical direction for measurement, and the mode is mainly applied to measurement of the radioactive waste barrel requiring full coverage scanning.
7. The method of claim 1, wherein said step 4 comprises analyzing the activity of the selectable waste bin by:
(1) Whole barrel numerical calculation method
In a layered scanning mode or a helical scanning mode, the field of view function F (x) 0 ) And the measured dimensions of the active area of the waste bin, the cement-fixing or absorbing material of the waste bin and the wall thickness of the waste bin, the radioactivity in the bin is obtained byA：
Wherein N represents the net peak area count of the gamma-ray full energy peak with the energy of E; p represents the gamma-ray branching ratio of a radionuclide energy E; t represents the measured live time of the gamma energy spectrum; epsilon (x) 0 ) The detection efficiency of the detector on gamma rays with energy E at an efficiency scale point is shown; r, d P and dW Represents the waste bin radius, the thickness of the cement fixing or absorbing substance and the waste bin wall thickness; mu (mu) M 、μ P 、μ W A linear attenuation coefficient for gamma rays of energy E representing the waste bin active area, the waste bin cement fixed or absorbing material and the waste bin wall; v is the waste bin volume.
8. The method of claim 7, wherein said step 4 comprises analyzing the activity of the selectable waste bin by:
(2) Whole barrel Meng Ka simulation calculation method
In the layering scanning mode or the spiral scanning mode, all parameters except N, P and t in the formula, namelyAre determined by Monte Carlo simulation calculations as the detection efficiency ε.
9. The method of claim 7, wherein said step 4 comprises analyzing the activity of the selectable waste bin by:
(3) Efficiency matrix method
In the layered scanning mode, gamma energy spectrum type detectors are adopted to measure layer by layer or simultaneously measure multiple layers, the counting rate of gamma rays of each layer is obtained, a matrix relation is established by combining the detection efficiency of the detectors, the radioactivity of each layer is calculated by solving the matrix, and a barrel inner activity measuring result is obtained according to the following steps:
Wherein, subscripts 1 to n represent hierarchical numbers; epsilon ij The detection efficiency of the radioactivity of the j th layer is the detection efficiency of the detector when scanning to the i th layer.
10. The method of claim 7, wherein said step 4 comprises analyzing the activity of the selectable waste bin by:
(4) Single detector hot spot analysis
In the layered scanning mode, according to the fluctuation condition of the dose rate or the counting rate as a prompt, judging whether a hot spot exists or not, and further estimating and positioning the position of the hot spot, firstly, easily determining the angle of the hot spot, namely the peak and the trough of the fluctuation of the dose rate or the counting rate, wherein the angle corresponding to the peak is the angle of the hot spot, when the difference of the dose rate or the counting rate of the peak and the trough exceeds a certain threshold value, the hot spot is considered to exist at the moment, the hot spot positioning analysis is required, the distance between the hot spot and the central axis of the barrel, namely the radius of the hot spot is positioned, and the distance between the hot spot and the surface of the detector can be expressed as
wherein ,dx ＝d 0 -p i cos(β i +θ)，d y ＝p i cos(β i +θ)，d z =h denotes the height of the hot spot in the vertical direction relative to the detector center;
this distance consists of the following parts, the length l through the active area a Length through cement-fixing or absorbing substance l s Length l through the wall of the tub w And shielding length of collimation hole l c ：
wherein ,
theoretically, the detector measures the count:
wherein the exponential term product represents the attenuation of each portion, K (d n ) Is a collimator response function comprising a portion U (d n ) And a portion C (d) passing through the collimator without scattering n ) The sum of the two parts shows that the materials such as lead of the collimation hole, etc. are strong in shielding gamma rays, the attenuation of the gamma rays is very strong, C (d) n ) The contribution of U (d) is small n ) For K (d) n ) Is greater, which can be expressed as
wherein , S det the opening area of the detector in the collimation hole is defined;
let the effective radius of the collimator beThen
Thus, C (d) n ) Can be expressed as
To this end, the method is composed of C (d n) and U(dn ) K (d) n ) And then the theoretical count N (theta) and the theoretical count rate Z (theta) =N (theta)/t measured by the detector can be obtained, and then the count rate N (theta) is obtained according to the actually measured gamma energy spectrum, and after the theoretical count N (theta) and the theoretical count rate Z (theta) =N (theta)/t are normalized according to the maximum value, the theoretical count N (theta) and the theoretical count rate Z (theta) =N (theta)/t are compared with each other according to the radius length of the hot spot to minimize χ 2 I.e. solving the following minimum by iterative method
Obtaining relevant parameters, and positioning the hot spot to obtain the radius p where the hot spot is located i Finally by
The activity and activity concentration of the radioactive waste can be obtained when the hot spot is considered in the radioactive waste can;
(5) Double detector hot spot analysis method
In the layered scanning mode, at least two groups of gamma energy spectrum type detectors are used for simultaneously estimating and positioning hot spots in the barrel, when the waste barrel rotates, the hot spots also rotate along with the waste barrel, the hot spots can be regarded as annular sources, the radius of the annular sources is the radius of the hot spots, and the counting rate of the two detectors A, B on the same waste barrel can be expressed as
Z A ＝A·P·ε A (p i )
Z B ＝A·P·ε B (p i )
Wherein italic A indicates hot spot activity, p i Representing the radius at which the hot spot is located, the relative detection efficiency function may be defined as
I.e. Z B /Z A The value of (2) should be the relative detection efficiency function F (p i ) One point on the curve is marked with a respective scale on the detector A, B to obtain a relative detection efficiency function F (p i ) Curve, if F (p i ) Is a monotonic function, and passes through the counting rate ratio Z of the detector B and the detector A B /Z A The radius p of the annular line source can be uniquely determined i Thereby accurately obtaining the full-energy peak detection efficiency epsilon under the radius A (p i ) Or epsilon B (p i ) Further, the activity A was calculated.
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