CN106896396A - A kind of method for calibrating inert gas outflow thing off-line monitoring instrument detection efficient - Google Patents

Abstract

The present invention relates to a kind of for calibrating the method that inert gas flows out thing off-line monitoring instrument detection efficient, comprise the following steps：Using Monte Carlo simulation, the detection efficient of in the case of airequivalent detector to position point source in the detection efficient and gas sample space of gaseous sample is calculated respectively, and obtains one and represent a point position coordinates；Prepare the standard point source with many γ nucleic, place it at representative point position, obtain detection efficient of the detector to the point source；Calculate the detection efficient of detector under actual conditions to gaseous sample using Monte Carlo simulation, in the case of the airequivalent that the efficiency and Monte Carlo simulation are calculated detector to the ratio of the detection efficient of gaseous sample, as the attenuation correction factor；By detector to the detection efficient of point source at representative point position and the product of the attenuation correction factor, as the detector detection efficient actual to gaseous sample.This method is the traceability and reliability that can guarantee that calibration result value, and the inconvenience problem faced during using gas source is avoided that again.

Description

A kind of method for calibrating inert gas outflow thing off-line monitoring instrument detection efficient

Technical field

The invention belongs to radiation detection field, and in particular to one kind for calibrate inert gas outflow thing from The method of line monitor detection efficient.

Background technology

It is the health of environmental protection, staff and the public, nuclear power station, spentnuclear fuel reprocessing plant need The radioactivity gaseous inert gas effluent of its discharge is monitored, monitoring method is divided into on-line monitoring and off-line monitoring Two kinds.The advantage of off-line monitoring is accurately to know various radioactivity inert gas cores in gaseous effluent The discharge capacity of element, way is periodically to gather a certain amount of effluent gas with stainless steel sampling jar, then will The sample of collection is placed in the relatively low laboratory of background, and radionuclide is measured with high purity germanium detector The gamma-rays of transmitting, so as to know the activity concentration of each radionuclide.This method measurement result is accurate It is really reliable on condition that accurately knowing the detection efficient curve of the set measuring system.

The primary method for knowing detection efficient curve is to make one and sample almost striking resemblances Calibrating gas source, that is, require shape, size and material, the gas of sampling jar used by calibrating gas source Density and radionuclide species it is identical with sample.Use the maximum excellent of calibrating gas source Gesture be its result accurately and reliably, but the preparation difficulty in calibrating gas source is big, high cost；Due to some Nucleic half-life period of concern is extremely short (such as half-life period of Ar-41 only has 1.83 hours), further increases Big its cost.Additionally, can also face the transport of radioactive source, sealing, keeping using calibrating gas source With post processing etc. thorny problem.

DSMC can be used for detection efficient calculating, and DSMC low cost, speed are fast, There is the special Monte Carlo software such as Geant4, MCNP and EGS in PARTICLE TRANSPORT FROM field.But when illiteracy Detector model is built upon when in the probe size parameter of detector manufacturer offer in special Caro method, There is some difference for the parameter and actual value, causes the resultant error of DSMC may be very big, In-site measurement requirement can not be met；Additionally due to standard source is not used, DSMC result Value can not be traceable to relevant national standard.

The content of the invention

For defect present in prior art, the present invention provides a kind of for calibrating inert gas outflow The method of thing off-line monitoring instrument detection efficient, both can guarantee that calibration result magnitude tracing and reliability, Short calibrating gas source service life, high cost, keeping can be avoided again and post-process complicated problem, economical, It is easy, quick.

To achieve the above objectives, the technical solution adopted by the present invention is：There is provided a kind of for calibrating inertia The method of gaseous effluent off-line monitoring instrument detection efficient, comprises the following steps：

1) the Monte Carlo Calculation model of probe is set up, using the Monte Carlo Calculation model, Detector is to the detection efficient of gaseous sample and to gas sample in the case of calculating airequivalent respectively The detection efficient of position point source in product space；And obtain a representative point position coordinates；

2) many γ nucleic standard point sources that a piece is examined and determine by standard set-up are placed on step 1) It is middle to represent at point position coordinates, obtain detection efficient of the detector to standard point source；

3) using detection of the detector to gaseous sample under monte-Carlo model simulating actual conditions Efficiency, by the detection efficient and step 1) in by the detector of Monte Carlo Calculation to air The detection efficient ratio of gaseous sample during equivalent situation, as the attenuation correction factor.

4) by step 2) in detector to represent point position at standard point source detection efficient with Step 3) the middle attenuation correction fac-tor for obtaining, product is as detector to gaseous sample reality The detection efficient on border.

Further, in step 1) in represent point position coordinates using following equation obtain：

Wherein：It is detector to positionGas when place's point source and detector are to airequivalent situation The discernment function of sample detection efficient；It is required representative point position coordinates；It is profit The detector calculated with Monte Carlo simulation is to the detection efficient of point source at each position point in sample space； ε_air,MC(E_i) be using the detector of Monte Carlo Calculation to airequivalent situation when gaseous sample spy Survey efficiency；E_iIt is i-th gamma-ray energy.

Further, in step 1) in, the dimensional parameters provided using detector manufacturer set up probe Monte Carlo Calculation model.

Further, in step 1) in, the point source position that represents should ensure that in gamma energy of concern Scope, when detector is pointed to that the detection efficient of point source and detector are to airequivalent situation at this point The detection efficient difference of gaseous sample is minimum.

Advantageous Effects of the invention are：

The present invention is obtained using Monte-Carlo code and represents point position by setting up Monte Carlo Calculation model Coordinate and decay factor are put, then by testing many nucleic γ point sources at measurement representative point position, so that Detection efficient curve can rapidly and accurately be obtained；The method need not prepare calibrating gas source, reduce into This while, eliminates the trouble of gas source transport, keeping and post processing, and Yin Mengteka is counteracted significantly Probe size and inconsistent the brought error of actual value in sieve model, it is ensured that the accuracy of detection efficient And traceability；Whole calibration procedure is quick, economical, easy.

Specific embodiment

Specific embodiment of the invention is described in further detail below.

Specific implementation process of the invention is divided into following seven step：

1. the dimensional parameters for directly being provided using detector manufacturer, set up the monte-Carlo model of probe.

2. calculated in the case where the gentle body composition of sampling tank skin is all for air using monte-Carlo model, Detector is designated as ε to the detection efficient of gaseous sample_air,MC(E_i).Here subscript air represents sampling Tank skin and gas componant are all air, hereinafter referred to as airequivalent situation, subscript MC represent the value by Monte Carlo simulation is calculated and obtained, E_iThe gamma-rays of different-energy is represented, similarly hereinafter.

3. one group of detector is calculated to point source at each position point in sample space using Monte Carlo simulation Detection efficient, is designated asHere subscript P represents point source,Represent the position of point source Coordinate.The distance of two adjacent position points is preferably arranged to 1mm in this step.

4. the position coordinates of calculation representative point.Represent point position coordinates seeks method such as formula (1)：

HereAs detector is to positionGas when place's point source and detector are to airequivalent situation The discernment function of body sample detection efficient；It is required representative point position.

5. many γ nucleic standard point sources are placed at representative point position, experiment measurement detector is to the point The detection efficient of each energy gamma-rays of source transmitting, is designated asHere subscript Exp tables Show that the data are obtained by experiment.

6. on the basis of the 2nd step, the material composition that will sample the gentle body of tank skin is set to its actual feelings Shape, i.e. tank skin material are stainless steel, and gas componant and density are consistent with gaseous sample in real case, Using Monte-Carlo code calculating detector to the detection efficient of sample, ε is designated as_true,MC(E_i), here Subscript true represents that the composition for sampling tank skin and sample gas is consistent with truth.Imitated according to the detection The detection efficient that rate and the 2nd step are obtained, calculates the attenuation correction factor：

7. detection efficient and 6th of the detector for the 5th pacing being measured to point source at representative point position The attenuation factor that step is calculated, obtains detection efficient of the detector to gaseous sample, as originally The result of the final gained of invention：

In sum, the method for the present invention calculates airequivalent respectively first with Monte-Carlo code Under situation detector to the detection efficient and detector of gaseous sample to position in gaseous sample space The detection efficient of point source, tries to achieve a so-called representative point position coordinates accordingly.The so-called point that represents has Such characteristic：In energy of γ ray scope of concern, detector is pointed to the point source at this point Detection efficient and detector to airequivalent situation when gaseous sample detection efficient difference it is minimum. Then many γ nucleic standard point sources that a piece is examined and determine by country-level metrological standard unit are placed on generation At table point, detection efficient curve of the measurement detector to standard point source.This many γ nucleic point sources are general Containing 8~10 kinds of nucleic, more than 10 gamma-rays of energy can be launched, energy of γ ray scope is 60keV~1836keV, covers the gamma-ray energy of radioactivity inert gas nucleic transmitting in effluent Amount scope.This many γ nucleic point sources can be bought from domestic and international radioactive source production firm.Finally, Using detector under Monte-Carlo code simulation practical situation to the detection efficient of gaseous sample, with reference to mould Detector can calculate decay to the detection efficient of gaseous sample under intending the airequivalent situation for calculating The factor, the decay factor calculated the measurement result of standard point source and simulation in Binding experiment, can be most Detection efficient curve of the detector to surveyed gaseous sample is obtained eventually, that is, realize efficiency calibration.

The present invention had both ensured that calibration result value can trace to the source to national measurement standard, and without the use of to mark Quasi- gas source, eliminates the problems that may be faced during the use of gas source, and present invention meter Calculate represent point position and decay factor when, be directed to Monte Carlo simulation value twice be divided by gained business, This way counteracts probe size result and inconsistent the brought error of actual value significantly, therefore, Final calibration result is accurate more than the result for directly calculating detection efficient using Monte Carlo simulation.

The inert gas off-line monitoring instrument that the present invention is successfully applied to domestic two nuclear power stations of calibration is (high-purity Germanium spectrometer) detection efficient, energy of γ ray be 60keV~1836keV scopes when, worst error Absolute value is less than 6%, meets nuclear facilities scene off-line monitoring instrument measurement radioactivity inert gas outflow thing The requirement worked to measurement error.

It is of the invention a kind of for calibrating the method that inert gas flows out thing off-line monitoring instrument detection efficient, Above-mentioned specific embodiment is not limited to, those skilled in the art's technology according to the present invention scheme draws Other implementation methods, also belong to technological innovation scope of the invention.

Claims (4)

1. a kind of for calibrating the method that inert gas flows out thing off-line monitoring instrument detection efficient, it is including as follows Step：

1) the Monte Carlo Calculation model of probe is set up, using the Monte Carlo Calculation model, point Detector is to the detection efficient of gaseous sample and empty to gaseous sample in the case of not calculating airequivalent The detection efficient of interior position point source；And obtain a representative point position coordinates；

2) many γ nucleic standard point sources that a piece is examined and determine by standard set-up are placed on step 1) It is middle to represent at point position coordinates, obtain detection efficient of the detector to standard point source；

3) detection of the detector to gaseous sample is imitated under calculating actual conditions using Monte Carlo simulation Rate, by the detection efficient and step 1) in the airequivalent situation that is obtained by Monte Carlo Calculation The ratio of detection efficient of the lower detector to gaseous sample, as the attenuation correction factor.

4) by step 2) in detector to represent point position at standard point source detection efficient with step Rapid 3) the middle attenuation correction fac-tor for obtaining, product is as detector to gaseous sample reality Detection efficient.

2. as claimed in claim 1 a kind of for calibrating inert gas outflow thing off-line monitoring instrument detection The method of efficiency, it is characterized in that：In step 1) in represent point position coordinates using following equation obtain：

$\left\{\begin{array}{c}t\left(\stackrel{\→}{r}\right)=\underset{E_{min}}{\overset{E_{max}}{\Σ}}{\[\frac{{\mathrm{\ϵ}}_{P,MC}(\stackrel{\→}{r},E_i)-{\mathrm{\ϵ}}_{air,MC}\left(E_i\right)}{{\mathrm{\ϵ}}_{air,MC}\left(E_i\right)}\]}^2\\ t\left({\stackrel{\→}{r}}_{rp}\right)=\underset{\stackrel{\→}{r}}{min}\left\{t\left(\stackrel{\→}{r}\right)\right\}\end{array}\right.$

Wherein：It is detector to positionGas sample when place's point source and detector are to airequivalent situation The discernment function of product detection efficient；It is required representative point position coordinates；It is using illiteracy Detection efficient of the detector that special Monte Carlo Simulation of Ions Inside is calculated to point source at each position point in sample space； ε_air,MC(E_i) be using the detector of Monte Carlo Calculation to airequivalent situation when gaseous sample detection Efficiency；E_iIt is i-th gamma-ray energy.

3. as claimed in claim 1 a kind of for calibrating inert gas outflow thing off-line monitoring instrument detection The method of efficiency, it is characterized in that：In step 1) in, the dimensional parameters provided using detector manufacturer, Set up the Monte Carlo Calculation model of probe.

4. as claimed in claim 1 a kind of for calibrating inert gas outflow thing off-line monitoring instrument detection The method of efficiency, it is characterized in that：In step 1) in, the point position that represents should ensure that of concern Gamma energy scope, detector is pointed to represent the detection efficient and detector of point source at point to airequivalent feelings The detection efficient difference of gaseous sample is minimum during shape.