CN106815453B - Nuclear power plant's ray radiation source strength backstepping method and ray radiation source strength backstepping system - Google Patents
Nuclear power plant's ray radiation source strength backstepping method and ray radiation source strength backstepping system Download PDFInfo
- Publication number
- CN106815453B CN106815453B CN201510848833.8A CN201510848833A CN106815453B CN 106815453 B CN106815453 B CN 106815453B CN 201510848833 A CN201510848833 A CN 201510848833A CN 106815453 B CN106815453 B CN 106815453B
- Authority
- CN
- China
- Prior art keywords
- radiation source
- detector
- power plant
- nuclear power
- radiation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 230000005855 radiation Effects 0.000 title claims abstract description 183
- 238000000034 method Methods 0.000 title claims abstract description 69
- 230000003287 optical effect Effects 0.000 claims abstract description 13
- 239000000463 material Substances 0.000 claims abstract description 8
- 239000011159 matrix material Substances 0.000 claims description 52
- 238000004364 calculation method Methods 0.000 claims description 25
- 230000005251 gamma ray Effects 0.000 claims description 24
- 238000001514 detection method Methods 0.000 claims description 11
- 238000012544 monitoring process Methods 0.000 claims description 8
- 238000009825 accumulation Methods 0.000 claims description 7
- 238000000354 decomposition reaction Methods 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 6
- 231100000673 dose–response relationship Toxicity 0.000 claims description 4
- 239000006185 dispersion Substances 0.000 claims description 3
- 230000004907 flux Effects 0.000 claims description 3
- 238000012545 processing Methods 0.000 claims description 3
- 238000004458 analytical method Methods 0.000 abstract description 4
- 238000012417 linear regression Methods 0.000 abstract description 2
- 238000010606 normalization Methods 0.000 abstract 1
- 239000000941 radioactive substance Substances 0.000 description 3
- 239000002351 wastewater Substances 0.000 description 3
- 239000002826 coolant Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000008034 disappearance Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000002285 radioactive effect Effects 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 229910052768 actinide Inorganic materials 0.000 description 1
- 150000001255 actinides Chemical class 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000004992 fission Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000002354 radioactive wastewater Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
- G16Z—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS, NOT OTHERWISE PROVIDED FOR
- G16Z99/00—Subject matter not provided for in other main groups of this subclass
Landscapes
- Measurement Of Radiation (AREA)
Abstract
The invention discloses a kind of nuclear power plant's ray radiation source strength backstepping method and ray radiation source strength backstepping systems, in this method, the dosage rate of multiple positions is obtained by detector, normalization radiation source intensity is spatially carried out discrete, optical distance is calculated using ray tracing method, the information such as bond material, buildup factor carry out the calculating of equation group coefficient, and backstepping goes out source strength；Then dosage rate calculating is carried out to detector position, by the way that measured value and calculated value are carried out linear regression analysis, calculates the key parameters such as standard deviation, slope, intercept, and then calculate quality factor to measure the acceptable degree of each calculated result；It proposes the Weighted Iterative Methods simultaneously, reduces the error that the biggish detector of uncertainty introduces, above steps may be repeated multiple times in the way of iteration until quality factor reach pre-set value, obtains desired radiation source intensity information.
Description
Technical Field
The invention relates to a method and a system for calculating the intensity of a radiation source in a nuclear power plant, in particular to a method and a system for strongly pushing back a radiation source of a nuclear power plant.
Background
The radioactivity of a nuclear power plant comes from the active area of the fuel assemblies in the pressure vessel and the radiation source consists mainly of fission products, actinides and corrosion activation products. In the system operation, the radiation sources flow along with the coolant through a main loop system (including a pressure vessel, a main pump, a pressure stabilizer, a main pipeline and the like), a chemical vessel control system and the like, and the radiation sources are distributed on the surfaces of the coolant and related equipment. The radioactive source is strong in radioactivity, the dosage of daily activities of workers in normal operation of a nuclear power plant accounts for about 20% of the total annual dosage, the dosage of the workers accounts for 80% of the total annual dosage during overhaul of the nuclear power plant, and the exposure dosage is reduced mainly by shortening the stay time of the workers in a radiation area during overhaul of the nuclear power plant.
The radiation sources in the nuclear power plant are widely distributed, and particularly after long-time use and overhaul, the radiation intensity of the radiation sources at each position is more and more difficult to deduce according to engineering experience, so that when a lot of data are calculated, particularly in the calculation according to the radiation source intensity, because accurate basic information is difficult to obtain, the accuracy and the practicability are greatly influenced, and meanwhile, under the condition that the domestic current protection facilities and means are not complete, the irradiation risk of workers is greatly increased.
In the prior art, when the intensity of a radiation source needs to be calculated, a source item analysis method is generally adopted, firstly, generation items (such as inflow items, decay generation items and the like) and disappearance items (such as filtering items, leakage items and the like) of the radioactive substance are determined according to the generation and disappearance ways of the radioactive substance, physical models of the items are determined, then a nuclear concentration balance equation (set) is established for the radioactive substance according to the items, and finally the equation (set) is solved in a simultaneous manner The accuracy and the like are all problematic, and a new radiation source intensity acquisition way needs to be improved or proposed.
For the reasons, the inventor of the present invention has made an intensive study on the existing method for calculating the source intensity information, and according to experience, generally, a pipeline or an assembly having uniform radioactivity in a nuclear power plant can be simplified into a line source or a group of line sources, so as to design a method and a system for strongly pushing back a line source radiation source of a nuclear power plant, which can solve the above problems.
Disclosure of Invention
In order to overcome the problems, the inventor of the invention carries out intensive research and designs a strong reverse pushing method and a strong reverse pushing system for a radiation source of a nuclear power plant, and the method and the system can obtain strong data of the radiation source of the nuclear power plant under a complex geometric space structure under the condition of fully ensuring the radiation safety of a human body; in the method, a detector is placed at a preset position in a nuclear power plant, and a detector with a shield is also placed at the position, so that the average energy of gamma rays emitted by a radiation source is obtained; in addition, a plurality of detectors for monitoring radiation values of the nuclear power plant are arranged in the nuclear power plant to obtain the dose rates of partial acquisition points, the radiation source intensity is dispersed in space simultaneously in a mode of combining point nuclear integration and a weighted least square method, the passing distance of gamma rays emitted by each discrete source in space is judged by using a ray tracing method, the optical distance is calculated, the calculation of the coefficients of an equation set is carried out by combining information such as materials and accumulation factors, and the source intensity is deduced reversely; then, a calculated value of the dose rate at the position of the detector is obtained, the measured value and the calculated value are subjected to linear regression analysis processing to obtain key parameters such as standard deviation, slope, intercept and the like, and further a quality factor capable of representing the physical meaning is obtained, and the quality factor can measure the acceptability of each calculation result; meanwhile, a weighted iteration method is provided, the error introduced by a detector with larger uncertainty is reduced, the steps are repeated for multiple times in an iteration mode until the quality factor meets the preset condition, and further the expected radiation source intensity and the uncertainty of the radiation field result are obtained, so that the method is completed.
Specifically, the present invention aims to provide the following:
(1) a strong reverse thrust method for a radiation source of a nuclear power plant line source is characterized by comprising the following steps:
step one, detecting dose rate D in a nuclear power plant by using a detector1,D2,D3…Di，
Step two, establishing an overdetermined equation set containing the radiation source intensity as shown in the following formula (one) according to the detected dose rate information,
(A)
Wherein the coefficient matrix a of the over-determined equation seti,jObtained by the following formulae (II) and (III),
(II)
(III)
Step three, calculating the overdetermined equation set in the step two by a least square method to obtain the intensity information of the radiation source, wherein the intensity of the radiation source is represented by the following formula (IV)
Sj,0＝(aj,i·ai,j)-1·aj,i·Di(IV)
Wherein D isiIndicating the dose rate detected by the ith detector; j represents the number of radiation sources; m represents the maximum value which can be reached by the number of radiation sources; sjRepresents the intensity of the jth radiation source; sj,0Representing the intensity of the jth radiation source for which the initial calculation was not iterated; a isi,jRepresenting a coefficient matrix which is the dose response coefficient of the jth radiation source to the ith detector;representing a line source dispersion coefficient; l isjRepresents a discrete number of jth radiation sources;representing normalized discrete source intensity; BD (E, L (. mu. (E), r)0→rp) Indicating an accumulation factor, E and L (. mu. (E), r)0→rp) A function of (a); l (. mu.E, r)0→rp) Denotes an optical distance, is μ (E) and r0→rpA function of (a); μ (E) represents a cross-sectional/linear attenuation coefficient; r is0→rpRepresenting the distance of the radiation source to the detection point; c (E) represents a flux-dose conversion factor, which is a function of E; e represents the energy, which is the average energy of gamma rays emitted by a radiation source in a nuclear power plant.
(2) The method for strongly backward pushing the radiation source of the nuclear power plant line source according to the above (1), which is characterized in that after the third step, the method further comprises the following steps,
step four, calculating the dose rate D at the position of the detector according to the intensity information of the radiation source obtained in the step three1′,D2′,D3′…Di′；
And step five, performing linear fitting on the dose rate information detected by the detector and the dose rate information at the position of the detector obtained by calculation to obtain a linear equation of the relationship between the dose rate information and the dose rate information after fitting, and further obtain fitting parameters, wherein the fitting parameters comprise: average uncertainty, goodness-of-fit and corresponding weight matrix;
step six, iterating the new weight matrix obtained in the step five to the overdetermined equation set in the step two to obtain a weighted overdetermined equation, and further repeating the step two, the step three and the step four until the expected radiation source intensity information is obtained;
wherein D isi' denotes the calculated dose rate at the ith detector position.
(3) The method for strongly backward estimating the radiation source of the nuclear power plant line source according to the above (1), wherein the method for calculating the average energy E of the gamma rays emitted by the radiation source in the nuclear power plant comprises the following substeps:
substep 1, selecting a preset position in a nuclear power plant, wherein the preset position is at a distance t from a radiation source, placing a detector at the preset position, and collecting the dose rate I detected by the detector0，
Substep 2, retrieving the detector, covering a shielding layer on the outside of the detector, placing the detector at the preset position, and collecting the dose rate I detected by the detector;
or, the detector is taken back, a shielding body is placed at a preset position, then the detector is placed in the shielding body, and the dosage rate I detected by the detector is collected;
substep 3, I and I obtained according to substeps 1 and 20The mass attenuation coefficient μ of the clad or shield is calculated by the following formula (five),
I/I0＝BDe-μt(V)
And a substep 4 of obtaining the average energy E of the gamma rays emitted by the radiation source according to the calculation result of the substep 3.
(4) The method for strongly backward pushing a radiation source of a nuclear power plant line source according to the above (1), wherein the method for calculating the optical distance L comprises the substeps of,
a sub-step a of tracking the progression of gamma rays from discrete radiation sources to detection points, recording the sequence of gamma rays traversing the irradiation zone,
and a substep b, respectively calculating the distance of each radiation area, and finally calculating the total optical distance L by combining the linear attenuation coefficient of the material of each radiation area.
(5) The method for strongly backward pushing the radiation source of the nuclear power plant line source is characterized in that the overdetermined equation set in the step two is processed by using a least square method, and the process of obtaining the intensity information of the radiation source comprises the following substeps:
substep 3-1. solving the overdetermined system of equationsExpressed in matrix form as AX ═ b;
substep 3-2, solving the normal equation A of the matrixTAX＝ATb, i.e. X ═ ATA)-1ATb；
Substep 3-3, solving equation by trigonometric decomposition of symmetric matrix, and recording G ═ ATA, wherein G is a symmetric matrix;
substeps 3-4, solving for G ═ LDL by trigonometric decompositionTWherein L is a small triangular matrix and D is a diagonal matrix;
substeps 3-5, solving the lower triangular matrix equation system LY1＝ATb；
Substeps 3-6, solving the diagonal matrix equation set: DY (DY)2＝Y1；
And substeps 3-7, solving an upper triangular matrix equation set: l isTX＝Y2。
(6) The method for strongly backward pushing a radiation source of a nuclear power plant line source according to the above (2), wherein in the fifth step, linear fitting is performed by the following formula (six),
(VI)
Wherein, the estimated dose rate is represented; which is indicative of the slope of the estimate,the estimated intercept is represented as a function of,
n represents the maximum number of detectors i can reach,representing the calculated average value of the dose rate at the detector position,representing the average value of the dose rate detected by the detector.
(7) The method for strongly backward pushing the radiation source of the nuclear power plant line source according to the above (6), is characterized in that in the fifth step, a weight function is obtained according to the uncertainty, and then a weight matrix W is obtained through the weight function, wherein the weight matrix W is obtained through the following formula (seven),
(seven)
Where f represents the uncertainty of the fit, the mean fit uncertainty is represented as a function of,fia fit uncertainty representing an ith detector position; (ii) aRepresenting a weight function.
(8) The method for strongly backward pushing the radiation source of the nuclear power plant line source according to the above (6),
in step six, when SiIf the quality factor M is greater than 0, stopping the weighting iteration when the quality factor M reaches the maximum value, and outputting the intensity information of the radiation source, wherein the output intensity information of the radiation source is the expected intensity information of the radiation source;
wherein, each time step six is executed, a quality factor M is obtained correspondingly, the quality factor M is obtained by the following formula (eight),
(eight)
Wherein R is2The goodness of fit is expressed,
(9) a system for strongly pushing back a line source radiation source of a nuclear power plant is characterized by being used for executing the method for strongly pushing back the line source radiation source of the nuclear power plant as claimed in claims 1-8.
(10) The system for strongly backward pushing the radiation source of the nuclear power plant line source according to the above (9), which is characterized by comprising a detector, a gamma ray average energy calculation module and a radiation source intensity calculation module;
the detector is provided with a plurality of detectors, including a preset position detector and a nuclear power plant radiation value monitoring detector,
the preset position detector is arranged at a preset position with a determined distance from a radiation source in a radiation area of a nuclear power plant, and a detachable shielding layer is optionally coated outside the preset position detector;
the preset position detector is used for transmitting the detected radiation rate information to the gamma ray average energy calculating module,
the nuclear power plant radiation value monitoring detectors are distributed in a radiation area of the nuclear power plant and used for transmitting respectively detected dose rate information in the nuclear power plant to the radiation source intensity calculating module,
the gamma ray average energy calculating module is used for calculating the average energy E of gamma rays,
the radiation source intensity calculating module is used for calculating the intensity of the radiation source in the nuclear power plant.
The invention has the advantages that:
(1) according to the method for strongly pushing back the radiation source of the nuclear power plant line source, the line source strong data under the complex geometric space structure in the nuclear power plant can be obtained under the condition that the radiation safety of a human body is fully guaranteed;
(2) according to the method for reversely pushing the radiation source intensity of the nuclear power plant line source, provided by the invention, through repeated iterative computation, the finally obtained line source intensity information is ensured to be closer to a true value, and the method has a very high engineering application value.
Drawings
Fig. 1 shows an overall workflow diagram according to a preferred embodiment of the present invention.
Detailed Description
The invention is explained in more detail below with reference to the figures and examples. The features and advantages of the present invention will become more apparent from the description.
The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
The invention provides a strong backstepping method of a radiation source of a nuclear power plant, which comprises the following steps:
step one, receiving dose rate information D detected by a detector in a power plant1,D2,D3…DiIn the present invention, a plurality of detectors may be placed in a power plant, or a detector already existing in the nuclear power plant may be directly utilized, the detector already existing in the nuclear power plant is a nuclear power plant radiation value monitoring detector, or the two methods may be used in combination, where the position of the detector is required to be: there is no shield between the radiation source and the location, and the dose rate in the present invention is the irradiation dose rate. In the invention, the number of detectors is greater than the number of radiation sources in the nuclear power plant.
Step two, establishing an overdetermined equation set containing the intensity of the radiation source according to the detected dose rate information, wherein the overdetermined equation set is a formula (one) as follows,
(A)
Step three, calculating the overdetermined equation set in the step two by a least square method to obtain the intensity information of the radiation source, wherein the intensity of the radiation source is represented by the following formula (IV)
Sj,0＝(aj,i·ai,j)-1·aj,i·Di(IV)
Coefficient matrix a of the overdetermined system of equationsi,jObtained by the following formulae (II) and (III),
(II)
(III) the first step of the method,
after the third step, the intensity information of the radiation source can be obtained, but the intensity information may not be accurate enough, so the calculation is continued through the following steps to obtain the intensity information of the radiation source closer to the true value;
step four, calculating the dose rate D at the position of the detector according to the intensity information of the radiation source obtained in the step three1′,D2′,D3′…Di′；
And step five, performing linear fitting on the dose rate information detected by the detector and the dose rate information at the position of the detector obtained by calculation to obtain a linear equation of the relationship between the dose rate information and the dose rate information after fitting, and further obtain fitting parameters, wherein the fitting parameters comprise: average uncertainty, goodness-of-fit and corresponding weight matrix; the weight matrix is divided into an inner weight matrix or an outer weight matrix, the calculation methods are consistent, and the difference is that the uncertainty of the outer weight matrix is not calculated by a system, but is the error range of the detector input by means of an operator.
Step six, iterating the weight matrix obtained in the step five to the overdetermined equation set in the step two to obtain a weighted overdetermined equation, and further repeating the step two, the step three and the step four until expected radiation source intensity information is obtained;
in the invention, D represents the dosage rate detected by a detector; diIndicating the dose rate detected by the ith detector; i represents the number of detectors; j represents the number of radiation sources; m represents the maximum value which can be reached by the number of radiation sources; s represents the intensity of the radiation source; sjRepresents the intensity of the jth radiation source; sj,0Representing the intensity of the jth radiation source for which the initial calculation was not iterated; a isi,jRepresenting a coefficient matrix which is the dose response coefficient of the jth radiation source to the ith detector;representing a line source dispersion coefficient; l isjRepresents a discrete number of jth radiation sources;representing normalized discrete source intensity; BD (E, L (. mu. (E), r)0→rp) Indicating an accumulation factor, E and L (. mu. (E), r)0→rp) A function of (a); l (. mu.E, r)0→rp) Denotes an optical distance, is μ (E) and r0→rpI.e. the optical distance is a function of the energy and the actual distance; μ (E) represents a linear attenuation coefficient; r is0→rpRepresenting the distance of the radiation source to the detection point; c (E) represents a flux-dose conversion factor, which is a function of E; e represents energy, which is the average energy of gamma rays emitted by a radiation source in a nuclear power plant; di' denotes the calculated dose rate at the ith detector position. Wherein the detection points represent the position of the detector, more precisely the position on the detector at which the radiation information is received.
The accumulation factor described in the present invention is a term commonly used in the art, and can be explained and calculated with reference to the ordinary meaning in the art, and the general formula of the calculation is given as follows:
wherein KxThe fitting formula of (a) is as follows:
K(E,x)＝cxa+d[tanh(x/Xk-2)-tanh(-2)]/[1-tanh(-2)]；
where E is photon energy, MeV; x is the distance from the source point to the calculated point, mfp; b is the accumulation factor at one mean free path; a, c, d, XkFor the empirical parameters, when the accumulation factor coefficient is selected, a logarithmic difference mode can be selected, that is:
a(Ea)＝{a(E1)·[log(E2)-log(Ea)]+a(E2)·[log(Ea)-log(E1)]}/[log(E2)-log(E1)]
in a preferred embodiment, the method for calculating the mean energy E of gamma rays emitted by a radiation source in a nuclear power plant comprises the following sub-steps:
substep 1, selecting a preset position in a nuclear power plant, wherein the preset position is at a distance t from a radiation source, placing a detector at the preset position, and collecting the dose rate I detected by the detector0，
Substep 2, retrieving the detector, covering a shielding layer on the outside of the detector, placing the detector at the preset position, and collecting the dose rate I detected by the detector;
or, the detector is taken back, a shielding body is placed at a preset position, then the detector is placed in the shielding body, and the dosage rate I detected by the detector is collected;
substep 3, I and I obtained according to substeps 1 and 20The mass attenuation coefficient of the clad or shield is calculated by the following formula (V)μ，
I/I0＝BDe-μt(V)
And a substep 4, obtaining the average energy E of the gamma rays emitted by the radiation source by looking up a table according to the calculation result of the substep 3. The table of the lookup table may be a material section table, which is presented at pages 16-67 of ANSI/ANS 6.4.3, "Gamma-ray attenuation Coefficients and Buildup Factor for Engineering Materials", American Nuclear Society, 1991. In the invention, all the used radiation energy is calculated by using the average energy, and if the energy difference of different areas in the nuclear power plant is large, the area can be considered to be independently measured, namely the average energy is independently measured, and the radiation source intensity is independently measured.
In a preferred embodiment, the method for calculating the optical distance L comprises the sub-steps of a tracking the course of the gamma rays passing from the radiation source to the detection point, and recording the sequence of the gamma rays passing through the radiation zone, i.e. calculating the distance r from the radiation source to the detection point by ray tracing0→rpWherein r is0Indicating the position of the radiation source, indicating the position r of the detection spotp. And a substep b, respectively calculating the distance of each radiation area, and finally calculating the total optical distance L by combining the linear attenuation coefficient of the material of each radiation area.
Specifically, when the traveling distance of the gamma ray is calculated, the space is described by a combined geometric method, and the spaces of different media are divided into different regions. And respectively calculating the distance Di between the intersection point of the gamma ray and each basic body and the inlet and the distance Do between the intersection point of the gamma ray and each basic body and the outlet. All the basic body numbers plus and minus are found in each area, with "+" and "-", which may include the following six steps,
(1) starting point r of each line0Determination of the region number Istart:
if there is no "-" element in a region, then all "+" elements in that region must satisfy the starting point r0Is located atIn some "+" basis, the starting area of the ray can be considered as the area; if there are "-" elements in the region, then all "+" elements in the region must satisfy the starting point r0In all "+" basis bodies, and all "-" basis bodies must satisfy the starting point r not containing the ray0Then the starting region of the ray is considered to be that region.
(2) End point r of each linepDetermination of the region number Ipend:
similarly, if there is no "-" element in a region, then all "+" elements in that region must meet the end point rpIn all "+" elementary volumes, then the ending area of the ray can be considered to be that area; if there are "-" elements in the zone, then all "+" elements in the zone must meet the end point rpIn all "+" basic bodies and all "-" basic bodies must satisfy the end point r not containing the raypThen the termination region of the ray is considered to be that region.
(3) Starting point r of each line0Determining the area outlet distance Zo corresponding to the area number:
if there is no "-" basic body in the gamma-ray starting region number, the smallest of the distances Do of taking out the basic bodies of all "+" in the starting region is the outlet distance of the gamma-ray starting region. If there are "-" basic bodies in the gamma-ray starting region, the minimum distance Do is taken out of all "+" basic bodies in the starting region, and then the minimum distance Di is taken out of all "-" basic bodies in the starting region, and the maximum value of the distances is taken as the outlet distance of the gamma-ray starting region.
(4) Determination of the number IP of each region through which the ray passes:
under the condition that the end point is not in the outermost zone, if no basic body exists in the zone number, firstly, judging adjacent sub-zones, and for all the plus basic bodies, when the inlet distance of the basic body is less than or equal to the inlet distance of the zone and less than the outlet distance of the basic body (Di < ═ Zin < Do), the zone is an adjacent zone of the previous zone, and solving a corresponding zone number IP; if the gamma ray area number has "-" basic bodies, the inlet distance of the basic bodies is less than or equal to the inlet distance of the area and less than the outlet distance (Di < ═ Zin < Do) of the basic bodies for all "+" basic bodies, and when the inlet distance of the basic bodies is greater than the inlet distance of the area or the outlet distance of the basic bodies is less than or equal to the inlet distance (Di > Zin or Do < ═ Zin) of the area for all "-" basic bodies, the area is the adjacent area of the previous area, and the corresponding area number IP is calculated.
(5) Determination of the entrance distance Zi and exit distance Zo of each zone traversed by the ray:
if there is no "-" basic body in the adjacent area, the outlet distance of the area is the minimum of the outlet distances Do of all "+" basic bodies, and the inlet distance of the area is the outlet distance of the previous area; if there is "-" basic body in the adjacent area, the smallest distance Do between the take-out ports of all "+" basic bodies is first determined, the smallest distance Di between the take-in ports of all "-" basic bodies is then determined, the largest value of the two distances is taken as the outlet distance of the area, and the inlet distance of the area is the outlet distance of the previous area.
(6) In the case that the end point is in the area of the outermost layer, firstly, finding all base body numbers aa of the outermost layer, and when the "+" base body in the area contains the base body aa and the "-" base body does not contain the area of the base body aa, finding whether the "-" base body exists, wherein the inlet distance of the "-" base body in the area is larger than the inlet distance (Di (k, minus (i, m)) > Zi (k, n)) of the area, if the "-" base body exists, taking the outlet distance of the area as the minimum of the inlet distances Di of all the "-" base bodies, and if the "-" base body does not contain the base body aa, taking the outlet distance of the area as.
Track to rpThe area IPend where the point is located and the ray exit distance is equal to the ray length. Thereby obtaining the traveling path of the gamma ray.
And then calculating the times of the ray passing through the area and the distance of each passing:
if the number of the passing area of the ray is not 0, the passing distance of the gamma ray in the area is equal to the distance of the inlet of the area minus the distance of the outlet of the area, and the passing times of the gamma ray is added with 1; if the passing area number of the gamma ray is 0, stopping tracking.
Gamma section mu is obtained by utilizing gamma mass attenuation coefficient and material of regional mediumn；
Through the above-mentioned process of recording the passing process of gamma ray passing through the area, the optical distance of each area is respectively calculated and then summed, namely:where N denotes the number of radiation areas, which is mainly determined by the environment inside the building.
In a preferred embodiment, the process of processing the over-determined equation set in step two by using the least square method and obtaining the radiation source intensity information comprises the following sub-steps:
substep 3-1. solving the overdetermined system of equationsExpressed in matrix form as AX ═ b;
substep 3-2, solving the normal equation A of the matrixTAX＝ATb, i.e. X ═ ATA)-1ATb；
Substep 3-3, solving equation by trigonometric decomposition of symmetric matrix, and recording G ═ ATA, wherein G is a symmetric matrix;
substeps 3-4, solving for G ═ LDL by trigonometric decompositionTWherein L is a small triangular matrix and D is a diagonal matrix;
substeps 3-5, solving the lower triangular matrix equation system LY1＝ATb；
Substeps of3-6, solving a diagonal matrix equation set: DY (DY)2＝Y1；
And substeps 3-7, solving an upper triangular matrix equation set: l isTX＝Y2。
Wherein X is (A)TA)-1ATb and Sj,0＝(ai,j T·ai,j)-1·ai,j T·DiCorrespondingly, the calculated value of the intensity of the radiation source is obtained through the substep 3-1 to the substep 3-7, and the least square method is a general overdetermined equation solving method in the field.
In a preferred embodiment, in step five, a linear fit is performed by the following equation (six),
(VI)
Wherein, the estimated dose rate is represented; which is indicative of the slope of the estimate,the estimated intercept is represented as a function of,
n represents the maximum number of detectors i can reach,representing the calculated average value of the dose rate at the detector position,representing the average value of the dose rate detected by the detector.
In a preferred embodiment, after the linear fitting, the average uncertainty, the goodness of fit, the quality factor, the weighting function and the corresponding weight matrix of the linear fitting are obtained, respectively, and the quality factor represents the reliability of the current iteration calculation. In the fifth step, a weight function is obtained according to the uncertainty, and a weight matrix W is obtained through the weight function, wherein the weight matrix W is obtained through the following formula (seven),
(seven)
Where f denotes the fit uncertainty, fiUncertainty of fit representing ith detector positionDegree; the mean fit uncertainty is represented as a function of,representing a weight function.
In a preferred embodiment, in step six, the judgment condition for obtaining the expected radiation source intensity information is when Si> 0, and the quality factor M reaches a maximum value, i.e. when SiAnd when the quality factor M reaches the maximum value, stopping the weighting iteration and outputting the radiation source intensity information, wherein the radiation source intensity information is the expected radiation source intensity finally obtained and is the radiation source intensity closest to the true value.
The invention aims to obtain the intensity of the radiation source closest to the true value, the reliability of the intensity of the radiation source obtained in the step three is low, and the error between the intensity of the radiation source and the true value is large, so in order to improve the accuracy of the value, namely to obtain the intensity of the radiation source closest to the true value, the invention provides the weighted iteration process from the step four to the step six, and finally sets the condition of iteration termination, so as to reduce the workload as much as possible under the condition of ensuring the accurate result, shorten the operation time and improve the efficiency of data acquisition. According to the weighted iteration method and the judgment standard of iteration termination. In addition, the intensity of the radiation source obtained by the method is more accurate than that obtained by a source item analysis method, is closer to a real value, and can ensure that the obtained value and the real value are within an order of magnitude. In a preferred embodiment, each time step six is executed, a quality factor M is obtained accordingly, which is obtained by the following formula (eight),
(eight)
Wherein R is2The goodness of fit is expressed,
in a preferred embodiment, the system of over-determined equationsIn the form of a matrix, see the following formula (nine)
(nine)
Where ε represents the error introduced by each detector; considering the physical implications, the error caused at each detection point can be considered to be caused by the radiation source, and the above equation is simplified to the following equation (ten),
(ten) the steps of (a) and (b),
wherein S*Representing the intensity of the radiation source with the error taken into account and it can be found that the coefficient matrix ai,jEquivalent to the dose response coefficient of the jth radiation source to the ith detector, for a line source,by discretizing the source in spatial coordinates (A, B, C), the response of the discrete source to the detector is then
The above equation system becomes after being dispersed
For theWith a radiation source S* 1For example, the radiation source is scattered in one-dimensional space coordinates, thenCan be obtained by the following formula (eleven),
(eleven)
Wherein,
namely, it is
Wherein, XLRepresenting the discretized coordinates;representing a cosine constant, wherein the value can be input manually and is 0 as a default value; l represents a discrete number, i.e., the number of parts into which the line source is divided when discrete calculation is performed.
According to the invention, a strong reverse thrust system of a nuclear power plant line source radiation source is provided, which is used for executing the strong reverse thrust method of the nuclear power plant line source radiation source.
Preferably, the system comprises a detector, a gamma ray average energy calculation module and a radiation source intensity calculation module;
the detector is provided with a plurality of detectors, including a preset position detector and a nuclear power plant radiation value monitoring detector,
the preset position detector is arranged at a preset position with a determined distance from a radiation source in a radiation area of a nuclear power plant, and a detachable shielding layer is optionally coated outside the preset position detector; the distance of the predetermined position from the radiation source may appear as a known quantity in a subsequent calculation;
the preset position detector is used for transmitting the detected radiation dose rate information to the gamma ray average energy calculating module for calculating the average gamma ray energy;
the nuclear power plant radiation value monitoring detectors are distributed in the radiation area of the nuclear power plant, are respectively positioned at the key positions in the invention, and are used for transmitting the respectively detected dose rate information in the nuclear power plant to the radiation source intensity calculation module,
the gamma ray average energy calculating module is used for calculating the average energy E of gamma rays,
the radiation source intensity calculating module is used for calculating the intensity of the radiation source in the nuclear power plant.
Experimental example:
NB281 room in nuclear island of unit No. 1 of nuclear power station in Bay of great AsiaAs an experimental object, the room is a place for placing a radioactive wastewater collection barrel in a nuclear island control area, and the radioactive liquid source in the wastewater collection barrel has the intensity of 0.7586E +10MeV/cm3S (or 4.2898E + 14/s). Simplifying the wastewater collection barrel into 4 vertical line sources, arranging a detector at the middle part of the wastewater collection barrel every 50cm for five detectors, wherein the detection values obtained by each detector are respectively 2.032mSv/hr, 0.685mSv/h, 0.255mSv/h, 0.1446mSv/h and 0.0929mSv/h, namely D in the invention1,D2,D3,D4,D5The average energy obtained by the method and the system for obtaining the average energy provided by the invention is 1.3MeV, and the four point source intensities respectively obtained by adopting the method and the system for reversely pushing the source intensity provided by the invention are respectively
1.4836E +12MeV/(cm.s) (or 1.1869E +14MeV/s),
1.0739E +12MeV/(cm.s) (or 0.8591E +14MeV/s),
1.2566E +12MeV/(cm.s) (or 1.0053E +14MeV/s),
1.2635E +12MeV/(cm.s) (or 1.0108E +14 MeV/s).
From the final result, the sum of the obtained radiation intensities of the four line sources is basically consistent with the true value of the radiation intensity of the radiation source, so that the method and the system provided by the invention can obtain the radiation source intensity information close to the true value.
The present invention has been described above in connection with preferred embodiments, but these embodiments are merely exemplary and merely illustrative. On the basis of the above, the invention can be subjected to various substitutions and modifications, and the substitutions and the modifications are all within the protection scope of the invention.
Claims (9)
1. A strong reverse thrust method for a radiation source of a nuclear power plant line source is characterized by comprising the following steps:
step one, detecting dose rate D in a nuclear power plant by using a detector1,D2,D3…Di；
Step two, establishing an overdetermined equation set containing the radiation source intensity as shown in the following formula (one) according to the detected dose rate information,
wherein the coefficient matrix a of the over-determined equation seti,jObtained by the following formulae (II) and (III),
step three, processing the overdetermined equation set in the step two by a least square method to obtain the intensity information of the radiation source shown in the following formula (four),
Sj,0＝(aj,i·ai,j)-1·aj,i·Di(IV);
wherein D isiIndicating the dose rate detected by the ith detector; j represents the number of radiation sources; m represents the maximum value which can be reached by the number of radiation sources; sjRepresents the intensity of the jth radiation source; sj,0Representing the intensity of the jth radiation source for which the initial calculation was not iterated; a isi,jRepresenting a coefficient matrix which is the dose response coefficient of the jth radiation source to the ith detector;representing a line source dispersion coefficient; l isjRepresents a discrete number of jth radiation sources;representing normalized discrete source intensity; BD (E, L (. mu. (E), r)0→rp) Indicating an accumulation factor, E and L (. mu. (E), r)0→rp) A function of (a); l (. mu.E, r)0→rp) Denotes an optical distance, is μ (E) and r0→rpA function of (a); μ (E) represents a cross-sectional/linear attenuation coefficient; r is0→rpRepresenting the distance of the radiation source to the detection point; c (E) represents a flux-dose conversion factor, isE is a function of; e represents energy, which is the average energy of gamma rays emitted by a radiation source in a nuclear power plant;
after step three, the method further comprises the step of,
step four, calculating the dose rate D 'at the position of the detector according to the radiation source intensity information obtained in the step three'1,D′2,D′3…D′i；
And step five, performing linear fitting on the dose rate information detected by the detector and the dose rate information at the position of the detector obtained by calculation to obtain a linear equation of the relationship between the dose rate information and the dose rate information after fitting, and further obtain fitting parameters, wherein the fitting parameters comprise: average uncertainty, goodness-of-fit and corresponding weight matrix;
step six, iterating the weight matrix obtained in the step five to the overdetermined equation set in the step two to obtain a weighted overdetermined equation, and further repeating the step two, the step three and the step four until expected radiation source intensity information is obtained;
wherein, D'iRepresenting the calculated dose rate at the i-th detector position.
2. The method for strongly backward estimating a radiation source of a nuclear power plant line source according to claim 1, wherein the method for estimating the average energy E of gamma rays emitted by a radiation source in the nuclear power plant comprises the following sub-steps:
substep 1, selecting a preset position in a nuclear power plant, wherein the preset position is at a distance t from a radiation source, placing a detector at the preset position, and collecting the dose rate I detected by the detector0，
Substep 2, retrieving the detector, covering a shielding layer on the outside of the detector, placing the detector at the preset position, and collecting the dose rate I detected by the detector;
or, the detector is taken back, a shielding body is placed at a preset position, then the detector is placed in the shielding body, and the dosage rate I detected by the detector is collected;
substep 3, I and I obtained according to substeps 1 and 20The mass attenuation coefficient μ of the clad or shield is calculated by the following formula (five),
I/I0＝BDe-μt(V)
And a substep 4 of obtaining the average energy E of the gamma rays emitted by the radiation source according to the calculation result of the substep 3.
3. The method of claim 1, wherein the method of calculating the optical distance L comprises the substeps of,
a sub-step a of tracking the progression of gamma rays from discrete radiation sources to detection points, recording the sequence of gamma rays traversing the irradiation zone,
and a substep b, respectively calculating the distance of each radiation area, and finally calculating the total optical distance L by combining the linear attenuation coefficient of the material of each radiation area.
4. The method for strongly backward pushing the radiation source of the line source of the nuclear power plant as claimed in claim 1, wherein the overdetermined equation set in the second step is processed by using a least square method, and the process of obtaining the intensity information of the radiation source comprises the following sub-steps:
substep 3-1. solving the overdetermined system of equationsExpressed in matrix form as AX ═ b;
substep 3-2, solving the normal equation A of the matrixTAX＝ATb, i.e. X ═ ATA)-1ATb；
Substep 3-3, solving equation by trigonometric decomposition of symmetric matrix, and recording G ═ ATA, wherein G is a symmetric matrix;
substeps 3-4, solving for G ═ LDL by trigonometric decompositionTWherein L is a small triangular matrix and D is a diagonal matrix;
substeps 3-5, solving the lower triangular matrix equation system LY1＝ATb；
Substeps 3-6, solution pairThe system of angular matrix equations: DY (DY)2＝Y1；
And substeps 3-7, solving an upper triangular matrix equation set: l isTX＝Y2。
5. The method for strongly backward pushing a radiation source of a nuclear power plant line source according to claim 1, characterized in that in step five, a linear fitting is performed by the following formula (six),
wherein,represents the estimated dose rate;which is indicative of the slope of the estimate, the estimated intercept is represented as a function of,
n represents the maximum number of detectors i can reach,representing the calculated average value of the dose rate at the detector position,indicating the dose rate detected by the detectorAverage value of (a).
6. The method for strongly backward pushing a radiation source of a nuclear power plant line source according to claim 5, wherein in step five, a weight function is obtained according to the uncertainty, and then a weight matrix W is obtained through the weight function, wherein the weight matrix W is obtained through the following formula (seven),
where f represents the uncertainty of the fit, the mean fit uncertainty is represented as a function of,fia fit uncertainty representing an ith detector position;representing a weight function.
7. The method of claim 5, wherein the radiation source of the nuclear power plant is a radiation source with strong backward thrust,
in step six, when SiIf the quality factor M is greater than 0, stopping the weighting iteration when the quality factor M reaches the maximum value, and outputting the intensity information of the radiation source, wherein the output intensity information of the radiation source is the expected intensity information of the radiation source;
wherein, each time step six is executed, a quality factor M is obtained correspondingly, the quality factor M is obtained by the following formula (eight),
wherein R is2The goodness of fit is expressed,
8. a system for strongly pushing back a line source radiation source of a nuclear power plant is characterized by being used for executing the method for strongly pushing back the line source radiation source of the nuclear power plant as claimed in claims 1-7.
9. The system of claim 8, comprising a detector, a gamma ray mean energy calculation module, and a radiation source intensity calculation module;
the detector is provided with a plurality of detectors, including a preset position detector and a nuclear power plant radiation value monitoring detector,
the preset position detector is arranged at a preset position with a determined distance from a radiation source in a radiation area of a nuclear power plant, and a detachable shielding layer is optionally coated outside the preset position detector;
the preset position detector is used for transmitting the detected radiation rate information to the gamma ray average energy calculating module,
the nuclear power plant radiation value monitoring detectors are distributed in a radiation area of the nuclear power plant and used for transmitting respectively detected dose rate information in the nuclear power plant to the radiation source intensity calculating module,
the gamma ray average energy calculating module is used for calculating the average energy E of gamma rays,
the radiation source intensity calculating module is used for calculating the intensity of the radiation source in the nuclear power plant.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510848833.8A CN106815453B (en) | 2015-11-27 | 2015-11-27 | Nuclear power plant's ray radiation source strength backstepping method and ray radiation source strength backstepping system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510848833.8A CN106815453B (en) | 2015-11-27 | 2015-11-27 | Nuclear power plant's ray radiation source strength backstepping method and ray radiation source strength backstepping system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN106815453A CN106815453A (en) | 2017-06-09 |
| CN106815453B true CN106815453B (en) | 2019-05-14 |
Family
ID=59103083
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201510848833.8A Expired - Fee Related CN106815453B (en) | 2015-11-27 | 2015-11-27 | Nuclear power plant's ray radiation source strength backstepping method and ray radiation source strength backstepping system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN106815453B (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104376361A (en) * | 2014-10-15 | 2015-02-25 | 南京航空航天大学 | Nuclear accident source item inversion method based on BP neural network algorithm |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20040128081A1 (en) * | 2002-12-18 | 2004-07-01 | Herschel Rabitz | Quantum dynamic discriminator for molecular agents |
| US9489752B2 (en) * | 2012-11-21 | 2016-11-08 | General Electric Company | Ordered subsets with momentum for X-ray CT image reconstruction |
-
2015
- 2015-11-27 CN CN201510848833.8A patent/CN106815453B/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104376361A (en) * | 2014-10-15 | 2015-02-25 | 南京航空航天大学 | Nuclear accident source item inversion method based on BP neural network algorithm |
Also Published As
| Publication number | Publication date |
|---|---|
| CN106815453A (en) | 2017-06-09 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN106814384B (en) | Nuclear power plant's point source radiation source strength backstepping method and point source radiation source strength backstepping system | |
| West et al. | Use of Gaussian process regression for radiation mapping of a nuclear reactor with a mobile robot | |
| Nishiyama et al. | Experimental study of source of background noise in muon radiography using emulsion film detectors | |
| CN114660096B (en) | Method for testing thermal neutron shielding performance of material | |
| CN106991621B (en) | The recombination radiation source strength backstepping method and system of nuclear power plant's point source face source combination | |
| CN107290769B (en) | Strong backward pushing method and system for point source combination composite radiation source of nuclear power plant | |
| CN106991511B (en) | Strong backward thrust method and system for point source, line source and surface source combined composite radiation source of nuclear power plant | |
| Mendes et al. | Radioactive hot-spot localisation and identification using deep learning | |
| Khan et al. | A detector system for searching lost γ-ray source | |
| CN106991620B (en) | The recombination radiation source strength backstepping method and system of nuclear power plant's line source face source combination | |
| CN107292474B (en) | Nuclear power plant source radiation source strong backward pushing method and source radiation source strong backward pushing system | |
| CN106991265B (en) | Strong backward-pushing method and strong backward-pushing system for non-point source radiation source of nuclear power plant | |
| CN107292762B (en) | Strong backward pushing method and system for composite radiation source of point source and line source combination of nuclear power plant | |
| CN107290770B (en) | Nuclear power plant point-line-surface-body combined composite radiation source strong backward-pushing method and system | |
| CN106815453B (en) | Nuclear power plant's ray radiation source strength backstepping method and ray radiation source strength backstepping system | |
| CN111323806B (en) | Gas activation measurement method and system | |
| CN106815769B (en) | Strong backward pushing method and system for composite radiation source of point source and line source combination of nuclear power plant | |
| JP2015121510A (en) | Radiation measuring device and fuel debris presence/absence estimation method using the same | |
| CN113447974B (en) | Estimation method for three-dimensional distribution of intensity of radioactive source | |
| JP3129420B1 (en) | Separation and measurement method of radioactivity in the fluid in the pipe and the inner wall of the pipe | |
| Dubeau et al. | Multiple methods for assessing the dose to skin exposed to radioactive contamination | |
| Xu et al. | A sequential least-squares algorithm for neutron spectrum unfolding from pulse-height distributions measured with liquid scintillators | |
| Khan et al. | Design of Geiger Muller detector system for searching lost γ-ray source | |
| Cochran et al. | Considering Uncertainty and Risk in Public Protection Decisions. | |
| Khan et al. | A detector system for searching lost g-ray source |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20190514 |
|
| CF01 | Termination of patent right due to non-payment of annual fee |