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WS/T 675-2020: (Radon and its offspring individual dose monitoring method)
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(Radon and its offspring individual dose monitoring method)
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WS/T 675-2020
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Basic data | Standard ID | WS/T 675-2020 (WS/T675-2020) | | Description (Translated English) | (Radon and its offspring individual dose monitoring method) | | Sector / Industry | Health Industry Standard (Recommended) | | Classification of Chinese Standard | C57 | | Word Count Estimation | 12,116 | | Date of Issue | 2020-04-03 | | Date of Implementation | 2020-10-01 | | Regulation (derived from) | State-health communication (2020) No. 4 | | Issuing agency(ies) | National Health Commission | WS/T 675-2020: (Radon and its offspring individual dose monitoring method)---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Method for monitoring individual dose induced by radon and its progeny
ICS 13.280
C 57
WS
People's Republic of China Health Industry Standard
Personal dose monitoring method of radon and its progeny
2020-04-03 released
2020-10-01 implementation
Issued by the National Health Commission of the People's Republic of China
Table of contents
Foreword...II
1 Scope...1
2 Normative references...1
3 Terms and definitions...1
4 Monitoring principles...2
5 Measuring system...2
6 Radon exposure measurement...3
7 Dose estimation...3
8 Uncertainty Analysis...4
9 Quality Assurance...4
Appendix A (informative appendix) Schematic diagram of the structure of radon personal dosimeter...5
Appendix B (informative appendix) Detection limit of solid nuclear track measurement method...6
Appendix C (informative appendix) Conversion factor of effective radon dose per unit of radon exposure...7
Appendix D (Informative Appendix) Evaluation of the Uncertainty of Personal Dose Monitoring for Radon and Its Daughters...8
References...9
Foreword
This standard was drafted in accordance with the rules given in GB/T 1.1-2009.
Drafting organizations of this standard. Institute of Radiation Protection and Nuclear Safety Medicine, Chinese Center for Disease Control and Prevention, Beijing Chemical Occupational
Longjiang Provincial Center for Disease Control and Prevention, Institute of Radiation Medicine, Chinese Academy of Medical Sciences, Hubei Provincial Center for Disease Control and Prevention.
The main drafters of this standard. Deng Jun, Cao Lei, Zhao Yu, Zhang Liangan, Zhou Wenshan, Wang Tuo, Hao Shuxia, Sun Quanfu, Su Xu.
Personal dose monitoring method of radon and its progeny
1 Scope
This standard specifies methods for monitoring personal internal radiation doses caused by radon and its progeny using solid nuclear track detection technology.
This standard is applicable to the personal internal radiation dose monitoring caused by radon and its progeny by workers in workplaces such as uranium mines, non-uranium mines and underground culverts.
Measurement.
2 Normative references
The following documents are indispensable for the application of this standard. For dated reference documents, only the dated version applies to this document.
For undated references, the latest version (including all amendments) applies to this document.
GBZ 129 Specifications for personal monitoring of occupational internal exposure
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Radon
The main isotopes of chemical elements with atomic number 86 are 222Rn, 220Rn, and 219Rn.
Note. The radon in this standard only refers to 222Rn.
3.2
Radon exposure
In a certain period of time, the total amount of radon that enters the body through air exposure.
Note. The International System of Units (SI) unit is beque-hours per cubic meter.
3.3
Solid state nuclear track detection
Charged particle detection based on the phenomenon that when charged particles pass through an insulating medium, they will cause atomic-scale radiation damage along their tracks
method. If the damage density is high enough, it is processed by chemical etching and other methods, and it can be observed with an ordinary microscope.
3.4
CR-39
The scientific name of CR-39 is carbon propylene acetic acid, or allyl diethylene glycol carbonate.
Note. It was discovered by a chemist from Columbia Corporation of the United States. It is the No. 39 material in a series of polymers developed by the US Air Force, so it is commonly known as CR-39.
3.5
Chemical etching
The radiation damage of solid nuclear track detectors is etched by chemical reagents to form observable tracks.
3.6
Radon personal dosimeter
An appliance that can be worn on an individual to monitor the internal radiation dose caused by radon and its progeny.
Note. This standard specifically refers to a dosimeter composed of CR-39 components and a passive diffusion radon collection cup (box).
3.7
Balance factor; F
The ratio of the equilibrium equivalent concentration of radon to the actual concentration of radon.
Note. Equilibrium equivalent concentration refers to the concentration of radon activity when radon and its short-lived daughters are in equilibrium and have the same α potential concentration as the actual non-equilibrium mixture.
degree.
3.8
Follow up dosimeter
It is used to measure radon exposure in non-professional workplaces during the same period, including the dosimeter mailing process. It is necessary to monitor the personal dose of radon and its descendants
To deduct.
4 Monitoring principles
4.1 When the personal radon dose caused by occupational reasons may exceed 2 mSv/a, routine monitoring of the personal radon dose should be carried out. through
Under normal circumstances, it can be combined with on-site active measurement results and working conditions to determine whether it may exceed 2 mSv/a.
4.2 The personal dose monitoring cycle of radon and its progeny refers to the requirements of GBZ 129, and factors such as the sensitivity of the monitoring method should be considered. Monitoring records,
Reports and files should meet the requirements of GBZ 129.
5 Measuring system
5.1 Measurement system composition
5.1.1 The personal dose measurement system for radon and its progeny is mainly composed of a radon personal dosimeter, a chemical etching device and a track reading system.
5.1.2 The radon collection cup (box) of the radon personal dosimeter should be made of conductive plastic, and a radon collection chamber of appropriate size should be set aside.
Set a wearing pin (clip) for easy wearing and use. Refer to Appendix A for the schematic diagram of the radon personal dosimeter.
5.1.3 The chemical etching device consists of a constant temperature water bath, a temperature control system, an etching rack and an etching rack container.
5.1.4 The track readout system consists of an optical microscope and an adapted image analysis system.
5.2 Measurement system performance requirements
5.2.2 The personal radon dosimeter should have a waterproof function and be able to prevent air dust and radon progeny from entering the dosimeter.
5.2.3 During the chemical etching process, the temperature and concentration of the etching solution should be kept relatively constant, the temperature range is 60 ℃ ~ 80 ℃, the relative deviation is
±1 ℃. Etching conditions need to be optimized. Orthogonal experiments can usually be used to determine the concentration of etchant, etching time, and etching temperature.
number. For CR-39 components, the typical commonly used chemical etching conditions are sodium hydroxide (NaOH) aqueous solution, 10 h etching, etching
The engraving temperature is 70 ℃, or potassium hydroxide (KOH) aqueous solution, for 7 h etching, the etching temperature is 70 ℃.
5.2.4 Since the standard deviation of track density is related to the measured area and total track count, the actual measured area should not be less than 0.2 cm2, and
The readout system is required to perform accurate quantitative analysis on the total track number.
5.2.5 The measurement system should be verified or calibrated by a corresponding authorized metrology department.
5.2.6 Technical differences among laboratory personnel will introduce measurement differences. If manual reading is used, for the same set of samples, different people should
Repetitive inspections should be carried out to improve the accuracy of readings. The amount of repeated inspections should not be less than 5%, and the relative deviation introduced by control readings should be less than 20%.
5.2.7 The estimation of the detection limit using the solid nuclear track measurement method of this standard should be given. Refer to Appendix B for the method.
6 Radon exposure measurement
6.1 Measurement method
6.1.1 Preparation of radon personal dosimeter. Assemble the radon personal dosimeter in a low radon concentration environment, and pay attention to prevent the influence of static electricity.
When using sealed packaging.
6.1.2 Sending of radon personal dosimeter. Keep sealed during sending, and provide follow-up dosimeter.
6.1.3 Use of radon personal dosimeter. open the package before use and wear it on the chest of the person, and pay attention to dust and water. Remember
Record the information of the user, the place, and the release time of the dosimeter.
6.1.4 Recycling of radon personal dosimeter. sealed package of radon personal dosimeter, record the recovery time and other information, and send it back with the dosimeter
Measurement laboratory.
6.1.5 CR-39 etching. Take out the CR-39 element from the radon collection cup (box), and use an appropriate amount of cleaning solution (distilled water or deionized water, etc.)
After cleaning the surface, place it in the etching system for etching. The etched solid nuclear track detector is cleaned and dried, then placed in a cool, dry place
Save to be tested.
6.1.6 Track count. adopt the view field reading method. When counting manually, adjust the focal length of the optical microscope to fine-tune the handwheel until the track contour is clear.
Slowly move the stage, read and record the number of tracks one by one. When moving, be careful not to cross or repeat the same viewing area.
6.2 Calculation of personal radon exposure
Calculate the cumulative radon exposure in the monitoring period according to formula (1).
7 Dose estimation
According to formula (2), estimate the effective dose of radon and its daughters.
8 Uncertainty analysis
8.1 Uncertainty evaluation considering the individual dose levels of different radon and its daughters
The uncertainty assessment can be carried out according to the level of the effective dose to be accumulated.
a) When estimating the product effective dose ≤ 0.1 mSv, the uncertainty evaluation may not be considered;
b) When estimating the product effective dose > 0.1 mSv, the uncertainty of Type A and Type B, and the evaluation of the combined standard uncertainty should be considered.
Refer to Appendix D for the uncertainty evaluation of the monitoring methods of this standard.
8.2 Sources of uncertainty that should be considered in the personal dose monitoring of radon and its daughters
The sources of uncertainty that should be considered in the personal dose monitoring of radon and its daughters mainly include.
a) The rationality of the statistical fluctuations and their normal distribution in the track reading and counting of monitoring and following dosimeters;
b) The measurement system error caused by the difference in the physical performance of the detector is mainly the energy response and angle response;
c) The errors introduced by calibration or scale are mainly the uncertainty and nonlinearity of the scale coefficient;
d) Uncertainty component introduced by etching.
9 Quality Assurance
Quality assurance should always run through the whole process from monitoring plan formulation to result evaluation. Quality assurance includes but is not limited to the following requirements.
a) Choose dosimeters, equipment and instruments that meet the requirements and work normally;
b) Regular calibration and maintenance of the system;
c) Actively participate in the mutual comparison between laboratories, including measurement methods, technical specifications, etc.;
d) When selecting manual reading, technical training and authorization of personnel should be carried out, and technical training and authorization documents should be properly retained;
e) A follow-up dosimeter that can provide background information should be used;
f) The operating procedures for the issuance, wearing, transportation, recycling and storage of dosimeters should be formulated and strictly followed;
g) Perform dose evaluation in accordance with GBZ 129 requirements, record and properly save monitoring data;
h) For the removal of abnormal data, the method of re-examination shall be used on the spot, or appropriate statistical methods shall be used to remove the abnormal data. Culling
At the same time of abnormal data, the cause should be checked and analyzed, and recorded.
Appendix A
(Informative appendix)
Schematic diagram of radon personal dosimeter structure
The radon personal dosimeter in this standard specifically refers to a dosimeter composed of CR-39 components and a passive diffusion radon collection cup (box). Radon collection cup
(Box) The air inside and outside can be freely exchanged, and its shape is usually hemispherical or cylindrical; CR-39 elements are usually set in the radon collection cup (box)
The bottom center position (as shown in Figure A.1). Considering the energy of alpha particles emitted by radon and its daughters, and CR-39 can detect incident alpha
For reasons such as the critical angle of the particles and the convenience of wearing, it is recommended to use an approximate semicircular sphere with a diameter of about 4.0 cm and a height of about 2.0 cm.
The diffusion cavity of the personal dosimeter for radon.
Appendix C
(Informative appendix)
Conversion factor of unit radon exposure to effective radon dose
The conversion coefficient from the personal radon exposure to the accumulated effective dose of radon in the workplace is shown in Table C.1.
Appendix D
(Informative appendix)
Examples of Uncertainty Evaluation for Personal Dose Monitoring of Radon and Its Daughters
D.1 Evaluation of uncertainty in personal dose monitoring of radon and its progeny
D.1.1 The main sources of Type A uncertainty components are as follows.
a) The relative deviation of the background count, bu;
b) The relative deviation of the measurement count, Su.
D.2 Calculation of relative expanded uncertainty
D.3 Calculation example
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