This standard recommends the personal dose monitoring method of CR39 neutron dosimeter for neutron logging sites. This standard applies to the personal neutron dose monitoring of workers in 241Am-Be neutron source logging sites. GBZ/T 148-2002 Personal dose monitoring method of CR39 neutron dosimeter for neutron logging GBZ/T148-2002 Standard download decompression password: www.bzxz.net

ICS13.100
National Occupational Health Standard of the People's Republic of China GBZ/T 148-2002
Individual dose monitoring method with CR-39neutron dosimeter using in neutron logging2002-04-08 Issued
Ministry of Health of the People's Republic of China
Implementation on 2002-06-01
This standard is formulated in accordance with the Law of the People's Republic of China on the Prevention and Control of Occupational Diseases. Neutron well logging technology is a nuclear technology that has been widely used in the petroleum industry and has been used in my country for many years. In order to promote the smooth application and promotion of this technology in my country, the monitoring method of neutron dosimeter should be standardized and normalized to facilitate radiation protection and ensure the safety and health of radiation workers.
This standard formulates specific requirements for the personal dose monitoring method of CR39 neutron dosimeter used in neutron well logging sites in accordance with my country's national conditions.
This standard is proposed and managed by the Ministry of Health.
The drafting unit of this standard: Institute of Radiation Protection and Nuclear Safety Medicine, Chinese Center for Disease Control and Prevention. The main drafters of this standard: Feng Yushui, Lu Yangqiao, Li Junwen. The Ministry of Health is responsible for the interpretation of this standard. bzxZ.net
1 Scope
Personal dose monitoring method of CR39 neutron dosimeter for neutron measurement
GBZ/T148-2002
This standard recommends the personal dose monitoring method of CR39 neutron dosimeter for neutron measurement sites. This standard applies to personal neutron dose monitoring of workers in 4Am-Be neutron source logging sites. 2 Normative references
The clauses in the following documents become clauses of this standard through reference in this standard. For all dated referenced documents, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties to agreements based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, its latest version shall apply to this standard. GB12714 Radium-beryllium neutron source
3 Terms and definitions
The following terms and definitions apply to this standard. 3.1 Solid state nuclear track detector solid state nuclear track detector When nuclear particles pass through an insulator, they cause radiation damage of a certain density. After proper treatment, an observable track is formed. This solid is called a solid state nuclear track detector.
3.2 CR-39 track detector CR39 track detector A nuclear track detector made of allyl diglycol carbonate (product name CR39). According to the measurement procedure, the observable track formed by cumulative irradiation in the neutron field can be used to obtain the corresponding equivalent dose within a certain accuracy. It is a type of solid state nuclear track detector.
3.3 Chemical etching chemical etching
The radiation damage of a solid state nuclear track detector is etched by chemical reagents to form an observable track. 3.4 Neutron fluence sensitivity neutronfluencesensitivity The probability of generating nuclear tracks on the unit area of ​​the dosimeter for a unit neutron fluence at vertical incidence. 3.5 Neutron equivalent dose sensitivity neutronequivalentdosesensitivity The number of tracks corresponding to each unit equivalent dose on the unit area of ​​the neutron detector. 3.6 Neutron dose conversion coefficient neutrondoseconversoncoefficient The equivalent dose per unit neutron fluence converted using a humanoid phantom under various irradiation conditions. 4 Measuring element
CR39 personal neutron dosimeter consists of a CR39 track detector and a packaging box. 4.1CR39 track detector should have the characteristics of sensitivity to radiation damage, high transparency, uniform structure, isotropy, thermosetting stability and low background. CR39 is in sheet form, with a typical thickness of 1mm and an area of ​​10mmX20mm. 4.2 The packaging box is made of hard plastic, with a cylindrical or rectangular shape, and a wearing pin (clip) is installed on one side for easy use: its typical thickness is 5mm and the area is 55mm×35mm. 1
5 Measurement procedure
5.1 Chemical etching
5.1.1 The etching device consists of a constant temperature box and an etching cup. The etching device should keep the temperature and concentration of the etching solution constant and have a certain degree of sealing. The temperature change of the constant temperature box should be controlled within 60℃±1℃. The etching cup is made of corrosion-resistant stainless steel or glass. 5.1.2 The etchant is usually a mixture of an aqueous solution of sodium hydroxide (NaOH) and anhydrous ethanol. 5.1.3 The commonly used etching conditions are 6.8molNa0H aqueous solution, 12 hours etching, and an etching temperature of 60℃. The concentration of the etchant, etching time and etching temperature of different batches of materials are determined experimentally by orthogonal method. 5.1.4 After the track sheet has been soaked in steamed stuffing water for 2 hours, it must be cleaned with an appropriate amount of cleaning liquid (distilled water, etc.) after etching in the etching device, and after drying, it should be stored in a cool and dry place. 5.2 Track Observation
5.2.1 The track reading device usually uses an optical microscope and image analysis system with a magnification of more than 400 times. The CR39 personal neutron dosimeter uses an optical microscope for reading.
5.2.2 The track density usually adopts the field of view reading method, and the applicable track density is usually within the range of 10-10° bars/cm. When the track density is too high or too low, the track identification must be read according to a special statistical method. 5.2.3 The relative error of the reading is related to the reading area and the total number of tracks. Repeating the detector reading is a method to test the precision. The repeated inspection amount should account for 10%, and the error should be less than 20%. 5.3 Calibration method
5.3.1 The calibration neutron source should be consistent with the logging neutron radiation field conditions. Usually, a 2\Am-Be neutron source calibrated by the manganese bath method is used (uncertainty is less than 1%). The 2\Am-Be neutron source should meet the requirements of GB12714. 5.3.2 The CR39 personal neutron dosimeter should be subjected to background measurement, and the number of samples to be measured should be at least 10. The etched dosimeter should be exposed to air for more than 1 year, and its track should remain stable: when the Y absorbed dose is greater than 10Gy, its background should not be significantly affected. 5.3.3 When using a 2\Am-Be source, the neutron intensity should be greater than 10° neutrons/second, and its accuracy should be within 2%. The distance between the dosimeter and the source should be consistent with the logging site. The effect of neutron scattering on the scale should also be measured. Three parallel samples are placed on the scale. The detectable lower limit of the dosimeter is 0.1mSv.
5.3.4 The Am-Be neutron source is used as the calibration source, and its equivalent dose expression is: H=da·P/W
Wherein: H is the neutron equivalent dose received, Sv; dl is the neutron dose conversion factor of the 24Am-Be neutron source, 3.98×10-\Sv/n·cmP is the measured track density, Tracks/cm; W is the sensitivity of the dosimeter to the neutron injection of the Am-Be neutron source, Tracks/n. 6 Measurement requirements
6.1 Neutron logging site workers must wear a CR39 personal neutron dosimeter on the left chest when working on site. ()
6.2 During non-operating hours, the CR39 personal neutron dosimeter should be placed in a location that is not disturbed by artificial radiation sources, and a certain amount of dosimeters should be stored in the location as background dosimeters2
3 The monitoring cycle of the CR39 personal neutron dosimeter is three months, and it should be replaced four times a year. 6.3
The uncertainty of this monitoring method is less than 20%. 6.4
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