CN103901460A - Self-absorption correction method of self launching gamma ray under complex medium condition - Google Patents

Abstract

The invention relates to a self-absorption correction method of a self launching gamma ray under a complex medium condition. The method includes the following steps that detection efficiency and each energy parameter of gamma rays of different energies are measured; the measured counting rate of each energy parameter is converted to activity degree, and the activity degree serves as an initial activity degree value; a set of ratio Smi (Tm, Ei) under the test condition is obtained through comparing the initial activity degree obtained from each feature gamma ray with the initial activity degree corresponding the gamma ray of the largest branching ratio; a self-absorption factor of each feature gamma ray is obtained by the adoption of the above ratio; radioactive isotope activity degree fim corresponding to each feature gamma ray is obtained according to the self-absorption factor of each feature gamma ray; the fim is converted to quality of the radioactive isotope. According to the self launching gamma ray self-absorption correction method under the complex medium condition, self launching gamma ray self-absorption correction is conducted to an object to be tested when medium density, ingredients and thickness are variable parameters and the transmission measurement correction cannot be implemented by the adoption of an additional transmission source due to limitation of environmental conditions.

Description

The gamma-ray self-absorption bearing calibration of self-emission under a kind of complex dielectrics condition

Technical field

The present invention relates to a kind of antidote, relate in particular to the gamma-ray self-absorption bearing calibration of self-emission under a kind of complex dielectrics condition.

Background technology

Radiomaterial isotope can be launched a more than gamma-rays mostly, and these gamma-rays all can interact with material, and therefore the medium at radiomaterial place can absorb a part of gamma-rays, i.e. the self absorption effect of medium.The influence factor of Gamma ray self-absorption is mainly density, composition and the thickness etc. of medium, ray is relevant with medium kind with reaction type and ray energy that material occurs, so the gamma-rays of different-energy, in medium, independently self absorption effect can occur each other, this effect is difference with Media density, composition and variation in thickness.Under certain determines condition, three parameters are all known, can calculate the self-absorption factor by existing algorithm.

Radioactive material in material can carry out qualitative and quantitative analysis by the gamma-rays of measurement of species transmitting itself, the isotope ratio that obtains nuclear material also claims the information such as enrichment and isotopic quality interested, but generally all there is gamma-ray self-absorption Correction Problems, and the form that nuclear material exists in different material is not quite similar, density, thickness and the composition etc. of medium are also incomplete same, so the method that self-absorption is proofreaied and correct is also different.

Under normal circumstances, single, the sample of its medium composition of the nuclear material of enrichment analysis can reach that gamma-ray measurement infinite thickness requires, density and radioactivity be evenly distributed; There is medium complicated, density and radioactivity skewness or uniform situation roughly in the nuclear material of quality quantitative test.

The present invention is under uncertainty condition, when above-mentioned three factors are variable element, set up by experiment " the longitudinally change curve " of describing self absorption effect, simultaneously according to the intrinsic ratio between different-energy gamma-rays, derive its " horizontal change curve ", combine and set up two-dimensional curve analytic equation.By the parsing to two-dimensional curve, when obtaining Media density, composition and thickness etc. and being variable, wherein certain radioisotopic self-absorption correction factor.

In view of above-mentioned defect, creator of the present invention has obtained this creation finally through long research and practice.

Summary of the invention

The object of the present invention is to provide under a kind of complex dielectrics condition the gamma-ray self-absorption bearing calibration of self-emission in order to overcome above-mentioned technological deficiency.

For achieving the above object, the invention provides the gamma-ray self-absorption bearing calibration of self-emission under a kind of complex dielectrics condition, it is characterized in that, it comprises the following steps, wherein,

Step a1, under without self-absorption condition, measures the gamma-ray detection efficiency of different-energy and each energy parameter;

Step a2, is converted into activity by the counting rate that measures described each energy parameter, as initial activity value;

Step a3, the initial activity obtaining with every the feature gamma-rays initial activity corresponding with the gamma-rays of branching ratio maximum is compared, and obtains one group of ratio S under this condition to be measured _mi(T _m, E _i);

Step a4, utilizes described ratio S _mi(T _m, E _i), obtain the gamma-ray self-absorption factor of described every feature;

Step a5, draws according to the gamma-ray self-absorption factor of described every feature the radioactive isotope activity f that described every feature gamma-rays is corresponding _im;

Step a6, by described radioactive isotope activity f _imbe converted into radioisotopic quality.

Preferably, in described step a1, under without self-absorption condition, the gamma-ray detection efficiency computing formula of measurement different-energy is:

${\mathrm{\ϵ}}_i=\frac{C_i}{A\·B_i\·t\·w\·G_{\mathrm{ij}}\·\mathrm{\Ω}}$

In formula, ε _ifor measuring system is to the gamma-ray detection efficiency of particular energy; C _ifor measuring system measures certain gamma-ray tale; A is the specific activity of measurand, and Bqg gets in unit ^-1; B _ifor the gamma-ray branching ratio of particular energy, represent with number percent; T is Measuring Time, and s gets in unit; W is the quality of measurand, and g gets in unit; G _ijfor certain gamma-ray self-absorption factor in measurand, during without self-absorption, G _ij=1; Ω is measure geometry condition, containing solid angle; J=1 ..., n; Represent different quality thickness; I=1 ..., L, represents different-energy.

Preferably, in described step a4, obtain the gamma-ray self-absorption factor of described every feature and comprise and obtain the gamma-ray self-absorption factor of a non-principal character, the computation process of the gamma-ray self-absorption factor of described non-principal character is:

Work as S _mi(T _m, E _i) <S _ji(T _j, E _i) and S _mi(T _j, E _i) >S _{j+1, i}(T _j+1, E _i) time,

$G_{\mathrm{mi}}=G_j(T_j,E_i)\&times;\frac{S_i(T_m,E_i)-S_{j+1}(T_{j+1},E_i)}{S_j(T_j,E_i)-S_{j+1}(T_{j+1},E_i)}+G_{j+1}(T_{j+1},E_i)\&times;\frac{S_i(T_m,E_i)-S_j(T_j,E_i)}{S_{j+1}(T_{j+1},E_i)-S_j(T_j,E_i)}$

In formula, G _mifor each non-main gamma-ray self-absorption factor, E is different gamma-ray energy.

Preferably, in described step a4, obtain the gamma-ray self-absorption factor of described every feature and also comprise and obtain a main gamma-ray self-absorption factor,

Described main gamma-ray self-absorption factor computing formula is:

$G_{\mathrm{mL}}=G_{m,L-1}\&times;\frac{E_L-E_{L+1}}{E_{L-1}-E_{L+1}}{G}_{m,L+1}\&times;\frac{E_L-E_{L-1}}{E_{L+1}-E_{L-1}}$

In formula, G _mLfor the main gamma-ray self-absorption factor, E is different gamma-ray energy.

Preferably, radioactive isotope activity f _imcomputation process be: by the longitudinal change curve of value substitution of the self-absorption factor calculating in described step a4, obtain the radioactive isotope activity f that each feature gamma-rays is corresponding _im.

Preferably, described longitudinal change curve is:

$G_{\mathrm{ij}}=a_{\mathrm{ij}}{f}_{\mathrm{ij}}^2+b_{\mathrm{ij}}{f}_{\mathrm{ij}}+c_i$

Wherein G _if: the self-absorption factor;

F _ij: with the isotope activity of energy correlation;

I: represent different-energy; J: represent different quality thickness;

A _ij, b _ij, c _ij: be the matching factor.

Preferably, it also comprises the procurement process of a self absorption effect with the variation of energy of γ ray, i.e. the different-energy of the horizontal change curve of Gamma ray self-absorption, determines under mass thickness condition, and the gamma-ray self-absorption of different-energy is changed to relatively:

f _ji=a _jiE _i+b _ji

In formula: j=1 ..., n; Represent different quality thickness; I=1 ..., L, represents different-energy.

Beneficial effect of the present invention is compared with the prior art: the present invention lays particular emphasis on the quantitative test of nuclear material quality,, density limited for medium complicated, thickness of sample and radioactivity situation pockety, set up Gamma ray self-absorption bearing calibration under complex dielectrics condition, be applicable to can not take transmission method to carry out the analytic target of Gamma ray self-absorption correction because of the limitation of conditions.

Accompanying drawing explanation

Fig. 1 is the FB(flow block) of the gamma-ray self-absorption bearing calibration of self-emission under complex dielectrics condition of the present invention.

Embodiment

Below in conjunction with accompanying drawing, technical characterictic and the advantage with other above-mentioned to the present invention are described in more detail.

The gamma-ray self-absorption bearing calibration of self-emission under complex dielectrics condition in the present invention, itself can launch multiple kinds of energy gamma-rays from the contained radioactive isotope of material, utilize the rule of gamma-rays self-absorption generation respective change with Media density, composition and variation in thickness, the correlation parameter of analyte has been done respectively to normalization, as: self absorption effect is according to mass thickness (gcm ^-2) normalizing, each isotopic content is according to specific activity (Bqg ^-1) normalizing.After every gamma-ray measurement result normalizing, form self-absorption curve with mass thickness, i.e. " longitudinally change curve "; According to given mass thickness condition, convert each longitudinal change curve, form the relative curve of different-energy Gamma ray self-absorption effect, i.e. " horizontal change curve ", and set up thus two-dimensional curve analysis equation.The longitudinal change curve of simultaneous and horizontal change curve, set up Self absorption Correction model, resolve this two-dimensional curve function, draw under the conditions such as different medium density, composition and absorption thickness, the nuclear material Self absorption Correction factor that quantitatively (quality) analyzed in object.

For the Measurement and analysis of material to be analyzed, according to above-mentioned principle, take the method for reverse inverting first to obtain horizontal change curve, simultaneously by the longitudinal change curve of correction model simultaneous and the horizontal change curve verified, obtain the gamma-ray Self absorption Correction factor of different-energy, afterwards, utilize the data of gamma energy spectrum method for determining certain the isotopic quality in this object to be analyzed of deriving.

Below to contain ²³⁵the analysis of U is example, introduces the algorithm of the Self absorption Correction factor:

Refer to shown in Fig. 1, it is the process flow diagram of the gamma-ray self-absorption bearing calibration of self-emission under complex dielectrics condition of the present invention;

Step a1, measuring system is to the gamma-ray detection efficiency of different-energy under without self-absorption condition;

Can realize by following formula, the uranium-containing materials of known quantity, supposes that it distributes according to the geometric condition without self-absorption, and detection system records ²³⁵tetra-gamma-ray detection efficiencys of U are respectively ε _i:

${\mathrm{\&epsiv;}}_i=\frac{C_i}{A\&CenterDot;B_i\&CenterDot;t\&CenterDot;w\&CenterDot;G_{\mathrm{ij}}\&CenterDot;\mathrm{\&Omega;}}---\left(1\right)$

In formula, ε _ifor measuring system is to the gamma-ray detection efficiency of particular energy; C _ifor measuring system measures certain gamma-ray tale; A is in measurand ²³⁵the specific activity of U, Bqg gets in unit ^-1; B _ifor the gamma-ray branching ratio of particular energy, represent with number percent; T is Measuring Time, and s gets in unit; W is ²³⁵the quality of U, g gets in unit; G _ijfor certain gamma-ray self-absorption factor in measurand, during without self-absorption, G _ij=1; Ω is measure geometry condition, containing solid angle.

Step a2, is converted into activity by the counting rate that measures each energy, and this i.e. initial activity value in follow-up derivation;

Step a3, the initial activity obtaining with every the feature gamma-rays initial activity corresponding with the gamma-rays of branching ratio maximum is compared, obtain under this condition to be measured shape as one group of ratio Smi (Tm, Ei) of expression formula (2), now corresponding mass of medium thickness is Tm;

Step a4, utilizes above-mentioned ratio, obtains the gamma-ray self-absorption factor;

Process is: first, under different quality thickness condition, each curve ratio solution procedure with respect to prescribed energy reference point is as follows:

$S_{\mathrm{ji}}(T_j,E_i)=\frac{f_{\mathrm{ji}}}{f_{\mathrm{jL}}}---\left(2\right)$

In formula: j=1 ..., n; Represent different quality thickness; I=1 ..., L( ²³⁵the L=4 of U), represent different-energy.

S _ji(T _j, E _i) be that in different quality thickness horizontal curve, each energy point is organized self-absorption relative value with respect to the n of prescribed energy reference point

T _j: the mass thickness gcm of material ^-2

The self-absorption relative value slope curve of prescribed energy reference point is respectively organized in matching.

S _ji(T _j,E _i)=α _jE _i+β _j （3）

α _i, β _ifor undetermined coefficient.

Judge the matching degree between calibrated curve horizontal change curve under ratio curve and same mass thickness condition, derive one group of f _mifitting formula, the material self-absorption horizontal change curve that under this condition, quality is m, specifically can pass through following relational implementation:

Work as S _mi(T _j, E _i) <S _j, _i(T _j-1, E _i), and S _mi(T _j, E _i) >S _j+1, _i(T _j+1, E _i) time, get

$f_{\mathrm{mi}}=f_{j,i}\frac{S_{\mathrm{mi}}(T_m,E_i)}{S_{j,i}(T_j,E_i)}---\left(4\right)$

According to above-mentioned formula, utilize S _mi(T _m, E _i) and calibration curve, by the method for Lagrangian linear interpolation, calculate under this mass thickness condition the gamma-ray self-absorption factor of each non-principal character:

Work as S _mi(T _m, E _i) <S _ji(T _j, E _i) and S _mi(T _j, E _i) >S _{j+1, i}(T _j+1, E _i) time,

$G_{\mathrm{mi}}=G_j(T_j,E_i)\&times;\frac{S_i(T_m,E_i)-S_{j+1}(T_{j+1},E_i)}{S_j(T_j,E_i)-S_{j+1}(T_{j+1},E_i)}+G_{j+1}(T_{j+1},E_i)\&times;\frac{S_i(T_m,E_i)-S_j(T_j,E_i)}{S_{j+1}(T_{j+1},E_i)-S_j(T_j,E_i)}---\left(5\right)$

In formula, E refers to different gamma-ray energy, G _mifor each non-main gamma-ray self-absorption factor.

And the self-absorption factor of branching ratio maximum (main gamma-rays) solves by following formula:

$G_{\mathrm{mL}}=G_{m,L-1}\&times;\frac{E_L-E_{L+1}}{E_{L-1}-E_{L+1}}{G}_{m,L+1}\&times;\frac{E_L-E_{L-1}}{E_{L+1}-E_{L-1}}---\left(6\right)$

In formula, G _mLrefer to the main gamma-ray self-absorption factor, E refers to different gamma-ray energy.

Step 5, draws according to the gamma-ray self-absorption factor radioactive isotope activity f that each feature gamma-rays is corresponding _im;

Process is: for ease of statement and calculating, all materials to be measured are made to normalization, Qu Qi unit is mass thickness (gcm ^-2), utilize and measure and can extrapolate corresponding isotope activity by peak counting rate, carry out quadratic polynomial matching with the self-absorption factor, can obtain longitudinal change curve of each monoenergetic gamma rays self absorption effect, expression formula is as follows:

$G_{\mathrm{ij}}=a_{\mathrm{ij}}{f}_{\mathrm{ij}}^2+b_{\mathrm{ij}}{f}_{\mathrm{ij}}+c_i---\left(7\right)$

Wherein G _if: the self-absorption factor;

F _ij: with the isotope activity of energy correlation;

I: represent different-energy; J: represent different quality thickness;

A _ij, b _ij, c _ij: be the matching factor.

Then formula (7) is done to further normalized, will ²³⁵u activity is unified with specific activity (Bqg ^-1) describe, can obtain the horizontal change curve of different-energy Gamma ray self-absorption under this condition, horizontal change curve description is to determine that under mass thickness condition, the gamma-ray self-absorption of different-energy changes relatively;

f _ji=a _jiE _i+b _ji （8）

Longitudinally between change curve and horizontal change curve, have correlative factor, can set up according to this two-dimentional correction model of self absorption effect, the joining of two curves is the gamma-ray self-absorption factor of certain energy under certain mass thickness condition.The horizontal change curve of getting arbitrary energy under certain specified conditions be baseline ( ²³⁵186keV is got in U measurement), other horizontal change curve in contrast, the self-absorption feature when variation of ratio can intuitively be expressed this mass thickness.

G value substitution (7) formula that the 4th step is calculated (

) in, radioactive isotope activity f corresponding to each feature gamma-rays asking _im.Theoretically, many gamma-rays calculate the activity value obtaining and should equate.

Step a6, utilizes the fundamental formular of radioactivity decay, by f _imbe converted into radioisotopic quality.

The foregoing is only preferred embodiment of the present invention, is only illustrative for invention, and nonrestrictive.Those skilled in the art is understood, and in the spirit and scope that limit, can carry out many changes to it in invention claim, revise, and even equivalence, but all will fall within the scope of protection of the present invention.

Claims (7)

1. the gamma-ray self-absorption bearing calibration of self-emission under complex dielectrics condition, is characterized in that, it comprises the following steps:

Step a1, under without self-absorption condition, measures the gamma-ray detection efficiency of different-energy and each energy parameter;

Step a2, is converted into activity by the counting rate that measures described each energy parameter, as initial activity value;

Step a3, the initial activity obtaining with every the feature gamma-rays initial activity corresponding with the gamma-rays of branching ratio maximum is compared, and obtains one group of ratio S under this condition to be measured _mi(T _m, E _i);

Step a4, utilizes described ratio S _mi(T _m, E _i), obtain the gamma-ray self-absorption factor of described every feature;

Step a5, draws according to the gamma-ray self-absorption factor of described every feature the radioactive isotope activity f that described every feature gamma-rays is corresponding _im;

Step a6, by described radioactive isotope activity f _imbe converted into radioisotopic quality.

2. the gamma-ray self-absorption bearing calibration of self-emission under a kind of complex dielectrics condition according to claim 1, is characterized in that, in described step a1, under without self-absorption condition, the gamma-ray detection efficiency computing formula of measurement different-energy is:

${\mathrm{\&epsiv;}}_i=\frac{C_i}{A\&CenterDot;B_i\&CenterDot;t\&CenterDot;w\&CenterDot;G_{\mathrm{ij}}\&CenterDot;\mathrm{\&Omega;}}$

In formula, ε _ifor measuring system is to the gamma-ray detection efficiency of particular energy; C _ifor measuring system measures certain gamma-ray tale; A is the specific activity of measurand, and Bqg gets in unit ^-1; B _ifor the gamma-ray branching ratio of particular energy, represent with number percent; T is Measuring Time, and s gets in unit; W is the quality of measurand, and g gets in unit; G _ijfor certain gamma-ray self-absorption factor in measurand, during without self-absorption, G _ij=1; Ω is measure geometry condition, containing solid angle; J=1 ..., n; Represent different quality thickness; I=1 ..., L, represents different-energy.

3. the gamma-ray self-absorption bearing calibration of self-emission under a kind of complex dielectrics condition according to claim 1, it is characterized in that, in described step a4, obtain the gamma-ray self-absorption factor of described every feature and comprise and obtain the gamma-ray self-absorption factor of a non-principal character, the computation process of the gamma-ray self-absorption factor of described non-principal character is:

Work as S _mi(T _m, E _i) <S _ji(T _j, E _i) and S _mi(T _j, E _i) >S _{j+1, i}(T _j+1, E _i) time,

$G_{\mathrm{mi}}=G_j(T_j,E_i)\&times;\frac{S_i(T_m,E_i)-S_{j+1}(T_{j+1},E_i)}{S_j(T_j,E_i)-S_{j+1}(T_{j+1},E_i)}+G_{j+1}(T_{j+1},E_i)\&times;\frac{S_i(T_m,E_i)-S_j(T_j,E_i)}{S_{j+1}(T_{j+1},E_i)-S_j(T_j,E_i)}$

In formula, G _mifor each non-main gamma-ray self-absorption factor, E _ifor the gamma-ray energy of difference.

4. the gamma-ray self-absorption bearing calibration of self-emission under a kind of complex dielectrics condition according to claim 1, it is characterized in that, in described step a4, obtain the gamma-ray self-absorption factor of described every feature and also comprise and obtain a main gamma-ray self-absorption factor

Described main gamma-ray self-absorption factor computing formula is:

$G_{\mathrm{mL}}=G_{m,L-1}\&times;\frac{E_L-E_{L+1}}{E_{L-1}-E_{L+1}}{G}_{m,L+1}\&times;\frac{E_L-E_{L-1}}{E_{L+1}-E_{L-1}}$

In formula, G _mLfor the main gamma-ray self-absorption factor, E _lfor the gamma-ray energy of difference.

5. the gamma-ray self-absorption bearing calibration of self-emission under a kind of complex dielectrics condition according to claim 1, is characterized in that radioactive isotope activity f _imcomputation process be: by the longitudinal change curve of value substitution of the self-absorption factor calculating in described step a4, obtain the radioactive isotope activity f that each feature gamma-rays is corresponding _im.

6. the gamma-ray self-absorption bearing calibration of self-emission under a kind of complex dielectrics condition according to claim 5, is characterized in that,

Described longitudinal change curve is:

$G_{\mathrm{ij}}=a_{\mathrm{ij}}{f}_{\mathrm{ij}}^2+b_{\mathrm{ij}}{f}_{\mathrm{ij}}+c_i$

Wherein G _if: the self-absorption factor;

F _ij: with the isotope activity of energy correlation;

I: represent different-energy; J: represent different quality thickness;

A _ij, b _ij, c _ij: be the matching factor.

7. the gamma-ray self-absorption bearing calibration of self-emission under a kind of complex dielectrics condition according to claim 1, it is characterized in that, it also comprises the procurement process of a self absorption effect with the variation of energy of γ ray, it is the different-energy of the horizontal change curve of Gamma ray self-absorption, determine under mass thickness condition, the gamma-ray self-absorption of different-energy is changed to relatively:

f _ji=a _jiE _i+b _ji

In formula: j=1 ..., n; Represent different quality thickness; I=1 ..., L, represents different-energy.

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