CN104714245B - The half tomographic gamma scan method that middle cool waste bucket measures - Google Patents
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Abstract
A kind of half tomographic gamma scan method that middle cool waste bucket measures, including：Turntable, detector platform, detector with collimator, transmit source platform, transmission source and its shield member and analysis module, pail for used dressings is divided into several sections of layers along short transverse, by the way that pail for used dressings is rotated, radioactive point source is become into line distribution of the ring source on radial direction in the EDS maps of each section of layer, using detector, different eccentric positions measure in different sections of layer heights and each section of layer, establish the equation group of reaction detector count rate and each cyclic annular grid kernel element activity correlation, it solves equation group and obtains radionuclide specific activity in pail for used dressings along the distribution in bucket diameter direction and short transverse, summation obtains the total activity of radionuclide in pail for used dressings.This method high certainty of measurement, time of measuring is short, has very high practical value and application prospect.
Description
Technical field
The present invention relates to a kind of gals carrying out nucleic and activity measurement for low-activity barreled waste in nuclear power plant
Horse scan method and activity reconstruction technique, and the related device based on the technology specifically utilize radiation detector to measure even
Then the gamma rays sent out in speed rotation pail for used dressings reconstructs radionuclide and its activity along pail for used dressings radial direction and axial point
The scanning technique of cloth.
Background technology
As country greatly develops nuclear power, a large amount of middle cool wastes generated in nuclear power operation are urgently disposed.According to
The regulations such as standard GB/T 11928-1989, GB9132-1988, before carrying out intermediate temporary, transport, final disposal to these wastes
It must carry out nuclide identification and activity measurement in surface contamination and dosage rate detection, bucket.Since measurement object is to contain radioactivity
Large volume barreled waste, therefore nucleic in bucket and activity are carried out accurate to measure that there are certain difficulties.Currently, more satisfactory
Be non-destructive testing technology, γ scanning technology is one of most popular nuclear power plant's barreled waste detection method, including segmentation
Gamma scanning technique (Segmented Gamma Sacnning, SGS) and tomographic gamma scanning technique (Tomographic
Gamma Sacnning, TGS).Its principle is amplitude and the counting of gamma rays to be measured by radiation detector, then by more
The power spectrum for the gamma rays that the analysis of trace analysis instrument measures, so that it is determined that nucleic type and corresponding nucleic send out feature gamma rays meter
Digit rate.Since nucleic has distribution in bucket, and the ray sent out is also by the attenuation by absorption of substance in bucket, it is therefore desirable to build
The relationship of vertical meter digit rate and each nucleic activity in bucket.The SGS that nineteen seventies grow up is by pail for used dressings edge
If short transverse is divided into dried layer, it is assumed that substance and nucleic are uniformly distributed in tomography, and meter digit rate and activity are set up with this
Relationship, and define the scan mode of the detection method, i.e. pail for used dressings at the uniform velocity rotate that (the purpose is to reduce radionuclides in bucket to justify
The unevenness of circumferential direction distribution) and the stepping lifting measurement successively of each tomography of radiation detector face, it can be obtained by this method
Obtain distribution of the radioactive activity along pail for used dressings axial direction.SGS is uniformly distributed due to thinking radionuclide in pail for used dressings, after reconstruction
Activity compared with actual value error it is very big.The TGS that nineteen nineties propose is on the basis of SGS technologies, to each
The measurement of section layer introduces computed tomography scanning technology, can be calculated by rebuilding, obtain bucket inner stuffing matter and radionuclide specific activity
Distributed in three dimensions, substantially increase measurement accuracy.This method needs to carry out computed tomography scanning, i.e., detector from each different directions and
Position measures pail for used dressings, if pail for used dressings stepping rotates, detector eccentric center translation in the horizontal plane and along short transverse
Lifting, although therefore TGS high certainty of measurement, it is complicated to measurement process, the time is SGS tens times, limit it extensively
Using.
The short, low precision for SGS time of measuring, TGS high certainty of measurement, the feature of time length, it is opposite to seek time of measuring
Short, the relatively high Detection Techniques of measurement accuracy will be with important value and application prospect.For this purpose, a kind of based on double detector
Modified SGS technologies (Improved Segmented Gamma Sacnning, ISGS) are suggested, and principle is the base in SGS
On plinth, the radionuclide in each section of layer is equivalent to Single Point Source by its distribution, since pail for used dressings at the uniform velocity rotates when measuring, the point
Source is linear loop source, and the radius in ring source is determined by two probe positions, enables detection efficient accurate the positioning in source
It calculates, therefore detection accuracy is greatly improved compared with SGS.This method to point source there are the case where have very high detection accuracy, but more
Precision can reduce in the case of point source.
Invention content
The present invention in view of the above-mentioned deficiencies in the prior art, proposes a kind of half storey that middle cool waste bucket measures
Analyse (Semi-Tomography Gamma Scanning, STGS) gamma scan scan method, it is proposed by the present invention between SGS with
Half tomographic gamma scanning between TGS, radionuclide (ring-type exists) is in section layer half when can obtain pail for used dressings wheel measuring
Distribution on diameter and pail for used dressings short transverse, measurement accuracy are higher than SGS, and enormously simplify measurement process compared with TGS, shorten
Time of measuring.
In order to achieve the above objectives, the technical solution adopted in the present invention is as follows：
A kind of half tomographic gamma scan method that middle cool waste bucket measures, scanning means packet used by this method
Include turntable, detector platform, the detector with collimator, transmission source platform, transmission source and its shield member, analysis mould
Block, the radwaste bucket are at the uniform velocity rotated in scanning survey, radionuclide opposite bucket external detector after rotation in bucket
Annular line source is equivalent to by point source, pail for used dressings is divided to several sections of layers in an axial direction, each section of layer inner stuffing matter is uniformly distributed, then will
Several cyclic annular grids are divided in each section of layer, are measured by several eccentric positions of the detector in each section of layer, reconstructed meter
Radionuclide specific activity in each cyclic annular grid of acquisition is calculated to realize fast to the radioactivity of pail for used dressings along the radial and axial distribution of pail for used dressings
Speed accurately measures.
Specifically include following steps：
The specific location of the first step, adjustment detector and its collimator, transmission source and its shield member, makes detector axis
Alignment pail for used dressings center simultaneously passes through transmission source collimating aperture；
Second step, the scanning for carrying out current layer
Pail for used dressings is at the uniform velocity rotated with certain rotating speed, acquires gamma-spectrometric data；Make pail for used dressings center to the distance of detector axis
It is followed successively by scheduled distance, acquires several gamma-spectrometric datas of this section of layer in total；
Third step, by detector platform and transmission source platform since the pail for used dressings bottom, vertical direction simultaneously move
Source platform and detector platform are transmitted, is successively scanned, every layer of scanning all repeats second step；
4th step, data processing
The transmission measurement for carrying out each section of layer first obtains mean attenuation coefficient of this section of layer substance to ray, secondly will be each
Section layer divides the cyclic annular grid of homalographic along radial direction, calculates each grid and is imitated to the detection through substance correction for attenuation of detector
Rate, detector count rate correlation when establishing each cyclic annular grid radionuclide specific activity of reflection in each detecting location
Equation group solves equation group and obtains radionuclide specific activity in pail for used dressings along the distribution in bucket diameter direction and short transverse, summation
Obtain the total activity of radionuclide in pail for used dressings.
In the second step, pail for used dressings is at the uniform velocity rotated with certain rotating speed, and station acquisition its gamma-spectrometric data is measured to one
Depending on specific time of measuring is with radioactive level.
The data processing of 4th step includes that transmission reconstruction and transmitting are rebuild, and wherein transmission reconstruction is to obtain waste
The calculating analysis that each section of layer filler of bucket carries out attenuation coefficient or the density of ray, it is to obtain waste that transmitting, which is rebuild,
The calculating that radionuclide specific activity is distributed and carries out in bucket is analyzed.
The specific method of the transmission reconstruction is：
Think that substance is uniformly distributed in each layer, if PiEqual to detector when i-th section of layer position eccentric position is zero
The transmissivity measured：Pi=Ci/Cmax, wherein：I=1,2 ..., I, CiDetector is in i-th section of layer in the presence of indicating pail for used dressings
The gamma photons full energy peak counting rate that position measures；CmaxIndicate detector when the gamma-rays that transmission source is sent out is not decayed by sample
The relationship of the γ photon full energy peak counting rates measured, transmissivity and attenuation coefficient is：μiD=-ln (Pi), wherein μiIt is i-th section
For substance to the attenuation coefficient of ray, D is pail for used dressings diameter in layer.
It is described transmitting rebuild specific method be：
It will decline with matter interaction generation in bucket before reaching detector due to radionuclide is sent out in bucket ray
Subtract, it is therefore necessary to correction for attenuation is carried out, when detector face i-th section of layer, j-th of eccentric position, m n-th of ring network of layer
Radionuclide sends out ray and is by the counting rate that detector measures in lattice：Cmn,ij=α εmn,ij·χmn,ij·Amn, wherein α is
The branching ratio of the ray energy considered, εmn,ijBe in the cyclic annular grid of n-th of m layers radionuclide to being in i-th section of layer
The detection efficient of detector when j-th of eccentric position；AmnFor radionuclide specific activity in n-th of cyclic annular grid of m layers；Decaying school
Positive coefficient χmn,ij=exp (- Σ ul), μ and l are each layer attenuation coefficient and put down that n-th of cyclic annular grid of m layers is undergone to detector
Equal track lenth considers that detector can measure the ray that all grids are sent out in entire pail for used dressings, is in i-th section of layer jth
The counting rate that detector when a eccentric position measures is：In conjunction with the spy of all positions
It surveys, composition unknown number number is I × N, and equation number is the system of linear equations of I × J：
Pail for used dressings segments I is 9, and eccentric position number J value ranges are 2 to 8, and the cyclic annular grid number N of each section of layer is not more than
J。
The cyclic annular grid number N of each section of layer is identical as eccentric position number J.
Positional number, that is, equation number of the measurement, no less than unknown number number are the grid number divided, i.e. P >=Q.
The method for solving the system of linear equations is the alternative manner based on probability statistics.
Compared with traditional γ scanning technology, the present invention has the following advantages：
(1) compared with SGS, STGS can obtain distribution of the nucleic in section layer, therefore measurement accuracy greatly improves, and measure
Time only increases several times (specifically related with number of grid).In actually measuring, STGS and SGS is required to pail for used dressings and at the uniform velocity revolves
Turn and detector lifts (such as 9 times) along pail for used dressings short transverse stepping, but STGS also needs to carry out in each section of layer plane
Computed tomography scanning is realized in eccentric center translation (such as 4 times or 8 times) several times.
(2) compared with TGS, STGS is rotated by pail for used dressings, and section layer inner face (two dimension) distribution is reduced to radial direction (one
Dimension) distribution, scanning process is simplified, time of measuring can shorten an order of magnitude, and be all the application of chromatographic technique, measure essence
Degree is not substantially reduced.In actually measuring, TGS requires pail for used dressings progress stepping rotation (such as 24 times), detector stepping inclined
The heart is translatable (such as 4 times) and stepping lifting (such as 9 times), and STGS requires pail for used dressings at the uniform velocity to be rotated, therefore reduces to waste
Bucket carries out the process of circumference stepping measurement.
(3) compared with ISGS, STGS is rebuild according to ring source distribution feature, is not assumed to surveying using such as ISGS point sources
Hypothesis condition is arranged in amount technology, therefore measuring technique is more reasonable, and more applicable multiple sources or even nucleic are uniformly distributed the survey of situation
Amount.In actually measuring, STGS and ISGS are required to pail for used dressings and at the uniform velocity rotates and detector stepping lifting, but ISGS only needs
Primary in the movement of section layer plane bias, STGS needs eccentric movement repeatedly (such as 4 times or 8 times), and time of measuring is longer.
National standard, which requires nothing more than, at present measures the type and total activity of nucleic in pail for used dressings, does not require to obtain its tool
Body is distributed.Nucleic and activity measurement, the same radioactive level of precision, core are carried out to radwaste bucket using gamma scanning technique
Element and filler uniformity, detector etc. are related.For middle low-activity barreled waste, the higher nucleic of radioactive level
Exist in the form of hot spot, Radio-nuclide distribution lack of homogeneity；Meanwhile the compressed barrelling of filler, Density Distribution difference phase
To unobvious.Therefore, about radionuclide, the equally distributed hypothesis in each section of layer will cause prodigious detecting error to SGS,
TGS reconstructs the requirement that distributed in three dimensions of the nucleic in pail for used dressings exceeds relevant criterion again simultaneously, therefore STGS is balanced well
SGS and TGS is greatly enhanced about the advantage and disadvantage in measurement accuracy and time of measuring, the practicality.
Description of the drawings
Fig. 1 is the structural schematic diagram of one embodiment of measuring device used by the method for the present invention；
Fig. 2 is Fig. 1 embodiment device front views；
Fig. 3 is Fig. 1 embodiment turntable schematic diagrames；
Fig. 4 is Fig. 1 embodiment turntable moving assembly schematic top plan views；
Fig. 5 is the flow diagram of the method for the present invention；
Fig. 6 is in a certain section of layer inner annular mesh generation schematic diagram of pail for used dressings；
Fig. 7 is the horizontal cross-section schematic diagram of Fig. 6.
Specific implementation mode
It elaborates below to the embodiment of the present invention, the present embodiment is carried out lower based on the technical solution of the present invention
Implement, gives detailed embodiment and specific operating process, but protection scope of the present invention is not limited to following implementation
Example.
Embodiment
As shown in Figure 1, the present embodiment includes：Pail for used dressings turntable 1, turntable moving assembly 2, detector hoistable platform group
Part 3, transmission source hoistable platform component 4, pedestal 5, the high purity germanium detector 7 with collimator 6, the transmission source 8 with shielding slab
With data processing module 9, wherein：Turntable moving assembly 2, detector hoistable platform component 3 and transmission source hoistable platform component 4
It is set to jointly on pedestal 5, pail for used dressings turntable 1, high purity germanium detector 7 and transmission source 8 are respectively arranged at turntable movement group
On part 2, detector hoistable platform component 3 and transmission source hoistable platform component 4, and detector hoistable platform component 3 and transmission source
Hoistable platform component 4 is respectively placed in the both sides of pail for used dressings turntable 1, and high purity germanium detector 7 generates electric signal and and data processing
Module 9 is connected, this mechanical system can realize the precision lift of transmission source 8 and detector 7 and the rotation and translation of pail for used dressings.
As shown in figure 3, the pail for used dressings turntable 1 includes：First servo motor 11, rotation with the first retarder 10
Turntable support 12, turntable bottom plate 13, turntable axle sleeve 14, turntable main shaft 15, turntable swivel plate 16, turntable shaft coupling
17, thrust ball bearing 18, angle thrust ball bearing 19, wherein：Turntable bottom plate 13 is connected with turntable holder 12, the first servo
Motor 11 is connected with the first retarder 10, and the first retarder 10 is connect by turntable shaft coupling 17 with turntable main shaft 15, rotation
Turntable main shaft 15 is connect with turntable swivel plate 16, and thrust ball axis is respectively equipped between turntable main shaft 15 and turntable axle sleeve 14
18 and angle thrust ball bearing 19 are held, turntable swivel plate 16 is used to support and prevent from toppling；When with the first retarder 10
When one servo motor 11 rotates, turntable swivel plate 16 is driven to rotate by turntable shaft coupling 17 and turntable main shaft 15, and
Driving is placed in the rotation of the tested pail for used dressings on turntable swivel plate 16.
As shown in figure 4, the turntable moving assembly 2 includes：Second servo motor 20, the first ball-screw 21,
One guide rail 22, first base 23 and shaft coupling 24, wherein：First guide rail 22 is set in first base 23, the second servo electricity
The shaft of machine 20 is connected by shaft coupling 24 with the first ball-screw 21, the nut on the first ball-screw 21 and turntable bottom plate
13 are connected；When the second servo motor 20 rotates, drives the first ball-screw 21 to rotate and pail for used dressings is driven by feed screw nut
Turntable 1 realizes the movement in testee horizontal direction.
As shown in Fig. 2, the detector hoistable platform component 3 includes：Detector carriage 25, detector platform pedestal
26, the first tablet 27 with floor, the second tablet 28, the second ball-screw 29, the second guide rail 30, third ball-screw 31,
Third guide rail 32, hand circle wheel 33 and the third servo motor 35 with the second retarder 34, wherein：Detector carriage 25 is fixed
It is set on detector platform pedestal 26, the second guide rail 30 is set in detector carriage 25, and third servo motor 35 passes through
Two retarders 34 drive the second ball-screw 29 to rotate and the first tablet 27 are driven to lift, and third guide rail 32 is set to the first tablet
On 27, the second tablet 28 connect with third ball-screw 31 and is parallel to the first tablet 27, hand circle wheel 33 and third ball wire
Thick stick 31 is connected and the second tablet 28 is driven to translate, and high purity germanium detector 7 is placed on the second tablet 28.
As shown in Fig. 2, the transmission source hoistable platform component 4 includes：Transmission source holder 36, transmission source platform base
37, the third tablet 38 with floor, the 4th ball-screw 39, the 4th guide rail 40 and with the 4th servo of third retarder 41
Motor 42, wherein：Transmission source holder 36 is fixedly installed on transmission source platform base 37, and the 4th guide rail 40 is set to transmission source branch
On frame 36, the 4th servo motor 42 drives the 4th ball-screw 39 to rotate and drives 38 liters of third tablet by third retarder 41
Drop, transmission source 8 are placed on third tablet 38.
The flow chart of the method for the present invention shown in Fig. 5, it is specific as follows：
The method of the present invention realizes STGS scannings by step in detail below：
The first step, the elemental height position that the second tablet 28 and third tablet 38 is arranged, make the detection on the second tablet 28
Device 7 is directed at the bottom of pail for used dressings；Adjust high purity germanium detector 7 and its collimator 6 on the second tablet 28, transmission source 8 is the
Specific location on three tablets 38 makes 7 axis of detector be directed at 8 collimating aperture of transmission source.
Second step carries out the scanning for working as leading portion layer
Pail for used dressings at the uniform velocity rotates, and rotating speed is about 10 revs/min, and the specific time of measuring of a measurement position is with radioactive level
Depending on, generally 5-10 minutes, acquire the gamma-spectrometric data of a detecting location；Make pail for used dressings center to 7 axis of detector away from
From (such as 0,3.5,7.0,10.5,14.0,17.5,21.0,24.5cm) is followed successively by with a distance from specified 8, the section is acquired in total
8 gamma-spectrometric datas of layer.
Third step moves the second tablet 28 and third tablet 38 simultaneously in vertical direction, each to pail for used dressings from below to up
Layer is scanned, and mobile 9 times, each vertical range 10cm, every layer scanning all repeats second step.
4th step, data processing.
It is divided into two contents：Transmission reconstruction and transmitting are rebuild, and wherein transmission reconstruction is filled out to obtain each section of layer of pail for used dressings
The calculating analysis that substance carries out attenuation coefficient or the density of ray is filled, it is to obtain radioactivity in pail for used dressings that transmitting, which is rebuild,
The calculating that nucleic activity is distributed and carries out is analyzed.
(1) transmission reconstruction
This method is identical as SGS, it is believed that substance is uniformly distributed in each layer.If PiEqual to detector 7 i-th (i=1,
2 ..., I) transmissivity that measures when being zero of a section of layer position eccentric position：Pi=Ci/Cmax, wherein：CiIndicate pail for used dressings presence
When the gamma photons full energy peak counting rate that is measured i-th section of layer position of detector 7；CmaxIndicate the gamma-rays that transmission source 8 is sent out
The γ photon full energy peak counting rates that detector 7 measures when not decayed by sample.Transmissivity and the relationship of attenuation coefficient are：μiD=-
ln(Pi), wherein μiIt is substance in i-th section of layer to the attenuation coefficient of ray, D is pail for used dressings diameter.
(2) transmitting is rebuild
It will decline with matter interaction generation in bucket before reaching detector 7 due to radionuclide is sent out in bucket ray
Subtract, it is therefore necessary to carry out correction for attenuation.
It is each section of layer ring-type Meshing Method schematic diagram shown in Fig. 6, Fig. 7, it is assumed that nucleic is uniformly distributed in each grid.Net
Lattice are divided using equal area partition method, and n-th of ring radium computing method is：Wherein：N=1,2 ..., N, N are
The grid number of division, R are pail for used dressings radius.
When detector face i-th section of layer, j-th of eccentric position, radionuclide hair in n-th of cyclic annular grid of m layers
Emergent ray is by the counting rate that detector 7 measures：Wherein α is the ray energy that is considered
Branching ratio, εmn,ijIt is detected when for radionuclide in n-th of cyclic annular grid of m layers to being in i-th section of layer, j-th of eccentric position
The detection efficient of device 7, this detection efficient are mainly related with geometric position, 7 intrinsic conversion efficiency of detector；AmnFor n-th of ring-type of m layers
Radionuclide specific activity in grid；Attenuation correction coefficient χmn,ij=exp (- Σ ul), μ and l are that n-th of cyclic annular grid of m layers arrives
Each layer attenuation coefficient that detector 7 is undergone and average track lenth.Consider that detector can measure the ray that all grids are sent out,
The counting rate that detector 7 when in i-th section of layer, j-th of eccentric position measures is：
In conjunction with the detection of all positions, it is I × N that can form unknown number number, and equation number is the system of linear equations of I × J：
Wherein, P=I × J, Q=I × N, e=α ε χ, the positional number usually measured (i.e. equation number) are no less than unknown
Several numbers (grid number divided), P >=Q.The method for solving the system of linear equations is typically based on the iteration side of probability statistics
Method, such as maximum likelihood function iterative method (Maximum Likelihood-Expectation Maximization
Algorithm) etc..
By to equation group solve, can get radionuclide activity in pail for used dressings along bucket diameter direction and height side
To distribution.Summation obtains the total activity of entire pail for used dressings
Specific embodiments of the present invention are described above.It is to be appreciated that the invention is not limited in above-mentioned
Particular implementation, those skilled in the art can make various deformations or amendments within the scope of the claims, this not shadow
Ring the substantive content of the present invention.
Claims (9)
1. the half tomographic gamma scan method that a kind of middle cool waste bucket measures, scanning means includes used by this method
Turntable, detector platform, the detector with collimator, transmission source platform, transmission source and its shield member, analysis module,
It is characterized in that, the radwaste bucket is at the uniform velocity rotated in scanning survey, radionuclide opposite bucket after rotation in bucket
External detector is equivalent to annular line source by point source, and pail for used dressings is divided to several sections of layers in an axial direction, and each section of layer inner stuffing matter is uniform
Distribution, then several cyclic annular grids will be divided in each section of layer, it is measured by several eccentric positions of the detector in each section of layer,
Reconstructed calculating obtains radionuclide specific activity in each cyclic annular grid and is realized to pail for used dressings along the radial and axial distribution of pail for used dressings
Radioactivity fast and accurately measures；
Specifically include following steps：
The specific location of the first step, adjustment detector and its collimator, transmission source and its shield member makes detector axis be aligned
Pail for used dressings center simultaneously passes through transmission source collimating aperture；
Second step, the scanning for carrying out current layer
Pail for used dressings is at the uniform velocity rotated with certain rotating speed, acquires gamma-spectrometric data；Make pail for used dressings center to detector axis distance successively
For several scheduled distances, several gamma-spectrometric datas of this section of layer are acquired in total；
Third step, by detector platform and transmission source platform since the pail for used dressings bottom, in vertical direction mobile transmission simultaneously
Source platform and detector platform, are successively scanned, and every layer of scanning all repeats second step；
4th step, data processing
The transmission measurement for carrying out each section of layer first obtains mean attenuation coefficient of this section of layer substance to ray, secondly by each section of layer
The cyclic annular grid that homalographic is divided along radial direction, calculates detection efficient through substance correction for attenuation of each grid to detector,
The side of detector count rate correlation when establishing each cyclic annular grid radionuclide specific activity of reflection in each detecting location
Journey group solves equation group acquisition radionuclide specific activity and is obtained along the distribution in bucket diameter direction and short transverse, summation in pail for used dressings
Obtain the total activity of radionuclide in pail for used dressings.
2. the half tomographic gamma scan method that middle cool waste bucket according to claim 1 measures, which is characterized in that
In the second step, pail for used dressings is at the uniform velocity rotated with certain rotating speed, the specific measurement for measuring its gamma-spectrometric data of station acquisition to one
Depending on time is with radioactive level.
3. the half tomographic gamma scan method that middle cool waste bucket according to claim 1 measures, which is characterized in that
The data processing of 4th step includes that transmission reconstruction and transmitting are rebuild, and wherein transmission reconstruction is to obtain each section of layer of pail for used dressings
The calculating analysis that filler carries out attenuation coefficient or the density of ray, transmitting, which is rebuild, is radiated to obtain in pail for used dressings
Property nucleic activity distribution and carry out calculating analysis.
4. the half tomographic gamma scan method that middle cool waste bucket according to claim 3 measures, which is characterized in that
The specific method of the transmission reconstruction is：
Think that substance is uniformly distributed in each layer, if PiIt is measured equal to detector when i-th section of layer position eccentric position is zero
Transmissivity：Pi=Ci/Cmax, wherein：I=1,2 ..., I, CiDetector is surveyed i-th section of layer position in the presence of indicating pail for used dressings
The gamma photons full energy peak counting rate obtained；CmaxDetector measures when the gamma-rays that expression transmission source is sent out is not decayed by sample
The relationship of γ photon full energy peak counting rates, transmissivity and attenuation coefficient is：μiD=-ln (Pi), wherein μiFor object in i-th section of layer
The attenuation coefficient of confrontation ray, D are pail for used dressings diameter.
5. the half tomographic gamma scan method that middle cool waste bucket according to claim 3 measures, which is characterized in that
It is described transmitting rebuild specific method be：
Decaying will be generated with matter interaction in bucket before reaching detector due to radionuclide is sent out in bucket ray, because
This must carry out correction for attenuation, when detector face i-th section of layer, j-th of eccentric position, in n-th of cyclic annular grid of m layers
Radionuclide sends out ray：Cmn,ij=α εmn,ij·χmn,ij·Amn, wherein α is is examined
The branching ratio of the ray energy of worry, εmn,ijIt is radionuclide in the cyclic annular grid of n-th of m layers to being in i-th section of layer j-th
The detection efficient of detector when eccentric position；AmnFor radionuclide specific activity in n-th of cyclic annular grid of m layers；Correction for attenuation system
Number χmn,ij=exp (- ∑ ul), μ and l are each layer attenuation coefficient and average diameter that n-th of cyclic annular grid of m layers is undergone to detector
Mark length considers that detector can measure the ray that all grids are sent out in entire pail for used dressings, partially in j-th of i-th section of layer
The counting rate that detector when heart position measures is：In conjunction with the detection of all positions, group
It is I × N at unknown number number, equation number is the system of linear equations of I × J：
Wherein, P=I × J, Q=I × N, e=α ε χ, I, J are integer, and M indicates that the section number of plies of pail for used dressings division, N indicate every
Cyclic annular grid number, q in a section of layer indicate that the label of cyclic annular grid, Aq indicate the activity of radionuclide, J in q-th of grid
The eccentric position number for indicating detector, solves the system of linear equations, obtains the activity of radionuclide in pail for used dressings along bucket diameter
The distribution in direction and short transverse, summation obtain the total activity of entire pail for used dressings
6. the half tomographic gamma scan method that middle cool waste bucket according to claim 5 measures, which is characterized in that
Pail for used dressings segments I is 9, and eccentric position number J value ranges are 2 to 8, and the cyclic annular grid number N of each section of layer is not more than J.
7. the half tomographic gamma scan method that middle cool waste bucket according to claim 6 measures, which is characterized in that
The cyclic annular grid number N of each section of layer is identical as eccentric position number J.
8. the half tomographic gamma scan method that middle cool waste bucket according to claim 5 measures, which is characterized in that
Positional number, that is, equation number of measurement, no less than unknown number number are the grid number divided, i.e. P >=Q.
9. the half tomographic gamma scan method that middle cool waste bucket according to claim 5 measures, which is characterized in that
The method for solving the system of linear equations is the alternative manner based on probability statistics.
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