CN106814385A - Condense the 2 π solid angle measuring methods of radon need activity - Google Patents
Condense the 2 π solid angle measuring methods of radon need activity Download PDFInfo
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- CN106814385A CN106814385A CN201510855142.0A CN201510855142A CN106814385A CN 106814385 A CN106814385 A CN 106814385A CN 201510855142 A CN201510855142 A CN 201510855142A CN 106814385 A CN106814385 A CN 106814385A
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- radon
- particles
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- condensation
- energy
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/17—Circuit arrangements not adapted to a particular type of detector
- G01T1/178—Circuit arrangements not adapted to a particular type of detector for measuring specific activity in the presence of other radioactive substances, e.g. natural, in the air or in liquids such as rain water
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/185—Measuring radiation intensity with ionisation chamber arrangements
Abstract
The present invention relates to a kind of 2 π solid angle measuring methods for condensing radon need activity, methods described includes：Step 1, gaseous state radon is positioned in condensation cabin, and the gaseous state radon is condensed into solid-state radon；Step 2, to condensation cabin and cold finger, radon need and detector Holistic modeling, simulation calculates the behavior of α particles；Step 3, absorbs to the source of α particles and scattering effect is modified treatment；Step 4, the alpha energy spectrum of the alpha energy spectrum grid ionization chamber detector according to 2 π solid angles calculates the activity of solid radon need.Therefore, the present invention uses the π solid angle absolute method of measurement of grid ionization chamber 2, and solid angle is detected without accurate measurement, overcomes the scattering that collimating aperture causes, and can reach certainty of measurement higher.
Description
Technical field
The present invention relates to a kind of measuring method, especially a kind of 2 π solids angular measurement side for condensing radon need activity
Method.
Background technology
Radon -222 (abbreviation radon) is the unique gaseous species in uranium series decay chain, 3.823 days half-life period, is declined
α particles are discharged during change, daughter is polonium and lead and other elements.Radon can be dissolved in water, be in gaseous state under normal temperature, extensively
It is present in nature.Radon mainly enters human body by respiratory tract, due to the α particles and respiratory tract that decay
Etc. function of organization, the dosage caused to human body exceedes natural surroundings radiation mean dose (2.4mSv/)
50%, cause biological tissue to sustain damage, lung-cancer-risk is significantly greatly increased.
The certainty of measurement of existing measuring method is too poor.
The content of the invention
The purpose of the present invention is directed to the defect of prior art, there is provided a kind of 2 π of condensation radon need activity are three-dimensional
Angle measuring method, certainty of measurement is high.
To achieve the above object, the invention provides a kind of 2 π solids angular measurement side for condensing radon need activity
Method, methods described includes：
Step 1, gaseous state radon is positioned in condensation cabin, and the gaseous state radon is condensed into solid-state radon；
Step 2, to condensation cabin and cold finger, radon need and detector Holistic modeling, simulation calculates α particles
Behavior；
Step 3, absorbs to the source of α particles and scattering effect is modified treatment；
Step 4, the alpha energy spectrum of the alpha energy spectrum grid ionization chamber detector according to 2 π solid angles calculates solid radon
The activity in source.
Further, the step 2 is specifically included：Radon gas condensation model is built, emulation radon atom is cold
Behavior in the solidifying cabin confined space, sets up the pass of radon gas gas phase and solid phase under condensation temperature and air pressure conditions
System, with reference to the Temperature Distribution on cold finger, calculating makes the cold finger region that radon gas is condensed and the gas point for remaining
Son, calculating can realize the temperature range of total condensation.
Further, the step 3 is specifically included：Step 31, according to the radon atom number that is condensed,
The calculating of condenser zone and thickness, with reference to the measurement data of phosphorus screen method, sets up α particles inside radon need
Action model, calculate to the energy absorption coefficient of α particles and prevent coefficient, determine the self-priming of α particles
Receive correction factor；Step 32, carries out Holistic modeling, and simulation calculates α particles in detector and work gas
Body, cold finger, radon need, grid ionization chamber, the scattering of cabin wall and backscattering effect, energy loss mode,
Calculate the Scattering correction coefficient of α full energy peaks.
Further, the step 4 is specifically included：Step 41, the radon need of condensation contains what decay was produced
Radon daughter, the Energy distribution of α particles is launched with daughter with reference to the energy resolution and radon of grid ionization chamber
Scope, carries out energy spectrum analysis, sets up Spectra Unfolding Methods；Step 42, calculates grid ionization chamber alpha energy spectrum and differentiates
Ability, the measuring system set up under 2 π solid angles；Step 43, with reference to self-absorption, scattering and backscattering
Amendment, the algorithm of radon activity is calculated using full energy peak or full spectrum, calculate the composition of partial uncertainty with it is big
It is small, assess the uncertainty of activity absolute measurement.
Therefore, the present invention uses the π solid angle absolute method of measurement of grid ionization chamber 2, is visited without accurate measurement
Solid angle is surveyed, the scattering that collimating aperture causes is overcome, certainty of measurement higher can be reached.
Brief description of the drawings
Fig. 1 is the flow chart of the 2 π solid angle measuring methods of present invention condensation radon need activity.
Specific embodiment
Below by drawings and Examples, technical scheme is described in further detail.
Radon activity absolute method of measurement is used after radon is condensed into solid from gas carries out absolute measurement again
Method, precision small solid angle scheme higher needs accurate measurement solid angle, and measurement of correlation must be very
Carried out in small spatial dimension, difficulty is larger, the uncertainty of measurement thus brought is also larger；And it is accurate
The use of straight device so that scattering of the α particles at the empty edge of collimation cannot be avoided, cause power spectrum broadening and
The loss of α particles, also reduces the accuracy of activity measurement.The present invention is based on condensation radon absolute measurement side
Method, is measured using the alpha energy spectrum grid ionization chamber detector of 2 π solid angles, has both excluded three-dimensional angular measurement
The uncertainty of introducing, while overcoming liquid to dodge the influence in measurement larger dead time again.By side of the invention
Method sets up measuring method for high accuracy radon activity benchmark, for radon measurement provides tracing basis and high-caliber
Metrology Support.
The present invention realizes radon activity absolute measurement using the alpha energy spectrum grid ionization chamber detector of 2 π solid angles
Method.Including：Radon gas condensation model is built, by gaseous state radon total condensation into solid-state；To condensation cabin and
Cold finger, radon need and detector Holistic modeling, simulation calculate the behavior of α particles, study the suction of α particles
Receive and Scattering correction；Study the academic problems such as the Spectrum stripping techniques in analysis and radon activity algorithm of alpha energy spectrum.This project master
Measurement is tested with accurate by modeling, the behavior that research α particles are absorbed with scatter, target is to set up
Radon activity absolute method of measurement.
Fig. 1 is the flow chart of the 2 π solid angle measuring methods of present invention condensation radon need activity, as illustrated,
The present invention specifically includes following steps：
Step 101, gaseous state radon is positioned in condensation cabin, and the gaseous state radon is condensed into solid-state radon；
The absolute method of measurement based on radon need condensation is set up, two aspect problems need to be resolved.One is gaseous state
Radon whether can successfully be condensed into solid-state in order to carry out absolute measurement.Different condensations and measurement apparatus,
Due to the difference of structure, cold finger and the parameter of temperature control have that different (cold finger temperature typically exists in condensation process
The scope of 20K--100K).
Radon gas is condensed into solid-state by the present invention, and the absolute method of measurement of activity is carried out on this basis；Detection
Behavior law of the α particles that radon decay is produced in condensation cabin, the scattering to influenceing certainty of measurement is carried out
Amendment, the absorption to solid radon need to α particles is modeled and corrects；Source absorption is built with scattering model
It is vertical
The requirement of radon need, controls hydrone and other impurities gas molecule to enter condensation cabin in order to strict,
Using the radium source of ultrahigh vacuum seal.Radium-bearing resin is fixed between 600 mesh silk screens and stainless steel stent,
It is overall to be sealed in about 10cm in advance3Vacuum tank in, radon is diffused into container from radium, does not have moisture
Son and other impurities.
Cold-trap is set up, radon atom is caught, condenser system includes refrigeration machine and cold finger, and the temperature on cold finger becomes
Change to freeze by firm power and heated come dynamic control with variable power.The temperature on two grades of cold heads can be caused
Arbitrarily regulate and control within the temperature range of 15K--300K.Normal temperature is in cabin, is low temperature on cold head, by
This forms a cold-trap so that radon atom is continually condensed on cold finger.Adjusted by temperature control, changed
Become the thermograde on cold finger, by radon source container and condensing container bonding in vacuum, radon gas diffuses into cold-trap,
Radon is condensed in very limited region.
Step 102, to condensation cabin and cold finger, radon need and detector Holistic modeling, simulation calculates α
The behavior of son；
Specifically, radon gas condensation model is built, behavior of the emulation radon atom in the condensation cabin confined space,
The relation of radon gas gas phase and solid phase under condensation temperature and air pressure conditions is set up, with reference to the Temperature Distribution on cold finger,
Calculating makes the cold finger region that radon gas is condensed and the gas molecule for remaining, and calculating can realize total condensation
Temperature range.
By progressively heating up so that solid-state radon reverts to gaseous state, and is condensing cabin exterior reality after being measured
The method of existing total condensation.Development measurement and the laboratory facilities of HPGe gamma ray spectrometer relative measurements with reference to phosphorus screen,
Set up radon gas whether the evaluation method of total condensation.
According to Wagner formula, condensation assessment models are set up, the radon atom in cabin is condensed to being transferred into
Condensation effect is estimated.For what is be transferred into, activity is 105--106The radon of Bq, with reference to these radons
The distribution space geometric volume of atom, experiment determines parameters.
With reference to draught head estimation radon whether total condensation.Radon atom such as tens kBq, in work
Under gas temperature (293K), when being distributed in tens cubic centimetres of space, air pressure is 10-8HPa magnitudes, and
When temperature on cryosurface is 50K, the corresponding vapour pressure of radon is 10-14HPa magnitudes, thus can determine that not
The radon atom being condensed only accounts for the 10 of total amount-6, negligible degree is reached, total condensation can be realized.
Scheme one：Change cold finger temperature, such as be reduced to 40K from 110K, then temperature is risen into 100K,
The counting rate change of measurement condensation radon.In this change procedure, if the counting rate result of radon is in statistic fluctuation
In the range of it is consistent, then basic explainable condensation is complete, on the contrary then not by total condensation.Can be according to temperature
Whether the change of counting rate and spectral measurement result judgement radon gas are by total condensation in degree change procedure.
The repetition measurement experiment of re-evaporation is reclaimed in scheme two, absolute measurement with condensation.With reference to absolute measurement
Radon condensate recovery system afterwards, is evaporated after radon completes absolute measurement, and in the recovery of liquid nitrogen refrigerating
Collected in ampoule bottle or canister, then the condensation radon of this returnable evaporated, then carry out absolute measurement,
See whether can be coincide with initial absolute measurement result.This repeated experiment can play double effects, one
Whether by total condensation, can on the other hand can check reliably open radon when aspect is conducive to checking absolute measurement
Open up the transmission of quantity value of radon activity.
Step 103, absorbs to the source of α particles and scattering effect is modified treatment；
Specifically include：
Step 31, according to the radon atom number that is condensed, condenser zone and the calculating of thickness, with reference to phosphorus screen
The measurement data of method, sets up action model of the α particles inside radon need, calculates the energy to α particles
Absorption coefficient and prevention coefficient, determine the Self absorption Correction coefficient of α particles；
Step 32, carries out Holistic modeling, simulation calculate α particles in detector with working gas, cold finger,
Radon need, grid ionization chamber, the scattering of cabin wall and backscattering effect, energy loss mode calculate α complete
The Scattering correction coefficient at energy peak.
Atom number, condensation temperature and condensation model according to radon need, can calculate the thickness of radon need,
From the point of view of microcosmic, this radon need is exactly an individual shape source, the decay rule of distribution and α particles according to radon atom
Rule, sets up the assessment models of source absorption, calculates the energy loss situation sum of the α particles from internal hair
Amount damaed cordition, thus calculates absorption coefficient.
Certainly, the micro Distribution of radon may not be it is uniform, be according to the measurement result of phosphorus screen imaging system
Model is modified.
Phosphorus screen is positioned over the top of cold finger by support in advance, after radon need condensation, α of decay generation
Son is beaten on phosphorus screen, reflects that the DLU values of energy intensity are saved.After reading the image on phosphorus screen,
With reference to the resolution capability of phosphorus screen, the distribution of the diameter and transmitting alpha-particle energy of radon need is determined, as combination
Self-absorption model determines the experimental basis of correction factor.
Step 104, the alpha energy spectrum of the alpha energy spectrum grid ionization chamber detector according to 2 π solid angles calculates solid
The activity of radon need.
Specifically include：
Step 41, the radon need of condensation contains the radon daughter that decay is produced, with reference to the energy point of grid ionization chamber
Distinguish that ability and radon launch the range of energy distribution of α particles with daughter, carry out energy spectrum analysis, set up spectrum unscrambling side
Method；
Step 42, calculates grid ionization chamber alpha energy spectrum resolution capability, the measurement system set up under 2 π solid angles
System；
Step 43, with reference to self-absorption, scattering and backscattering amendment, calculates radon and lives using full energy peak or full spectrum
The algorithm of degree, calculates the composition and size of partial uncertainty, assesses the uncertainty of activity absolute measurement.
Using GEANT4 programs, three-dimensional programming is carried out to cold finger, radon need, cabin wall, grid ionization chamber and is retouched
State, be input into the material composition of all parts, using Monte Carlo simulation calculate the α particles of each energy with
The probability that these parts are scattered, and the accordingly distribution of energy, share of loss etc..
Am-241 sources and the reliability of Pu-239 sources inspection institute established model result of calculation with known emissivity,
For analysis deviation
The reason for be modified, untill it can analyze correct result.
Revised model is condensed into radon need with analysis, the scattering for obtaining radon need α particles is repaiied with backscattering
Positive coefficient.
The spectrum unscrambling algorithm of alpha energy spectrum：
Scheme one：According to grid ionization chamber output spectrum, grid ionization chamber energy resolution is being improved as far as possible
On the basis of ability, application weighting least square fitting, spline interpolation scheduling algorithm determine Rn-222's
The net peak area at 5.489MeV energy peak, deducts the influence at the 6.114MeV energy peak of Po-218, thus
Can individually with 5.489MeV can peak peak area by background, scattering, absorption and dead-time control after,
The population under 2 π solid angles is obtained, the population as radon need activity under 4 π is calculated.Carry out this
Uncertainty evaluation under part.
Scheme two：If the energy resolution of grid ionization chamber is not good enough, uncertainty evaluation result display solution
The error that spectrum causes is excessive, then consideration calculates activity with integral spectrum.
Therefore, the present invention uses the π solid angle absolute method of measurement of grid ionization chamber 2, is visited without accurate measurement
Solid angle is surveyed, the scattering that collimating aperture causes is overcome, certainty of measurement higher can be reached.
It should be noted last that, the above embodiments are merely illustrative of the technical solutions of the present invention and it is unrestricted,
Although being described in detail to the present invention with reference to preferred embodiment, one of ordinary skill in the art should
Understand, technical scheme can be modified or equivalent, without deviating from skill of the present invention
The spirit and scope of art scheme.
Claims (4)
1. it is a kind of condense radon need activity 2 π solid angle measuring method, it is characterised in that methods described bag
Include：
Step 1, gaseous state radon is positioned in condensation cabin, and the gaseous state radon is condensed into solid-state radon；
Step 2, to condensation cabin and cold finger, radon need and detector Holistic modeling, simulation calculates α particles
Behavior；
Step 3, absorbs to the source of α particles and scattering effect is modified treatment；
Step 4, the alpha energy spectrum of the alpha energy spectrum grid ionization chamber detector according to 2 π solid angles calculates solid radon
The activity in source.
2. method according to claim 1, it is characterised in that the step 2 is specifically included：
Radon gas condensation model is built, behavior of the emulation radon atom in the condensation cabin confined space sets up cold
Radon gas gas phase and the relation of solid phase, with reference to the Temperature Distribution on cold finger, calculate at solidifying temperature and air pressure conditions
Make the cold finger region that radon gas is condensed and the gas molecule for remaining, calculating can realize the temperature of total condensation
It is interval.
3. method according to claim 2, it is characterised in that the step 3 is specifically included：
Step 31, according to the radon atom number that is condensed, condenser zone and the calculating of thickness, with reference to phosphorus screen
The measurement data of method, sets up action model of the α particles inside radon need, calculates the energy to α particles
Absorption coefficient and prevention coefficient, determine the Self absorption Correction coefficient of α particles；
Step 32, carries out Holistic modeling, simulation calculate α particles in detector with working gas, cold finger,
Radon need, grid ionization chamber, the scattering of cabin wall and backscattering effect, energy loss mode calculate α complete
The Scattering correction coefficient at energy peak.
4. method according to claim 3, it is characterised in that the step 4 is specifically included：
Step 41, the radon need of condensation contains the radon daughter that decay is produced, with reference to the energy point of grid ionization chamber
Distinguish that ability and radon launch the range of energy distribution of α particles with daughter, carry out energy spectrum analysis, set up spectrum unscrambling side
Method；
Step 42, calculates grid ionization chamber alpha energy spectrum resolution capability, the measurement system set up under 2 π solid angles
System；
Step 43, with reference to self-absorption, scattering and backscattering amendment, calculates radon and lives using full energy peak or full spectrum
The algorithm of degree, calculates the composition and size of partial uncertainty, assesses the uncertainty of activity absolute measurement.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106814386A (en) * | 2015-12-01 | 2017-06-09 | 中国计量科学研究院 | Condense the 2 π solid angle measuring methods of radon need activity |
| CN108535763A (en) * | 2018-03-28 | 2018-09-14 | 中国原子能科学研究院 | A kind of radon activity absolute measurement device |
| CN110515115A (en) * | 2018-05-22 | 2019-11-29 | 中国辐射防护研究院 | A kind of appraisal procedure solved for gamma spectral peak area |
| CN111522058A (en) * | 2020-05-15 | 2020-08-11 | 中国计量科学研究院 | Method for generating coincidence addition correction factor |
-
2015
- 2015-12-01 CN CN201510855142.0A patent/CN106814385A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106814386A (en) * | 2015-12-01 | 2017-06-09 | 中国计量科学研究院 | Condense the 2 π solid angle measuring methods of radon need activity |
| CN106814386B (en) * | 2015-12-01 | 2019-09-06 | 中国计量科学研究院 | Condense 2 π solid angle measuring methods of radon need activity |
| CN108535763A (en) * | 2018-03-28 | 2018-09-14 | 中国原子能科学研究院 | A kind of radon activity absolute measurement device |
| CN110515115A (en) * | 2018-05-22 | 2019-11-29 | 中国辐射防护研究院 | A kind of appraisal procedure solved for gamma spectral peak area |
| CN110515115B (en) * | 2018-05-22 | 2022-11-25 | 中国辐射防护研究院 | Evaluation method for solving peak area of gamma spectrum |
| CN111522058A (en) * | 2020-05-15 | 2020-08-11 | 中国计量科学研究院 | Method for generating coincidence addition correction factor |
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Application publication date: 20170609 |