GB/T 15053-1994 Standard method for measuring absorbed dose using radiochromic film and polymethyl methacrylate dose measurement system
Some standard content:
National Standard of the People's Republic of China
Standard method for using radiochromic film and polymethylmethacrylate dosimetry systems to measure absorbed dose1 Subject content and scope of application
GB/T15053-94
1.1 This standard specifies the operation and test procedures for measuring absorbed dose using radiochromic film and polymethylmethacrylate (PMMA) dosimetry systems. This standard is applicable to the measurement of absorbed dose in the irradiated material by using water absorbed dose under photon irradiation by these two dose measurement systems. Other film (sheet) dosimeters can be used for reference. Electron beam dose measurement can also be implemented by reference. 1.2 This standard specifies the applicable conditions of the two dose measurement systems as follows: 1.2.1 Radiochromic film
Absorbed dose: 0.2~1×102kGy;
Absorbed dose rate: 1×10-2~1×107Gy·s-1c
Photon energy: 0.1~5MeV;
Irradiation temperature: -20~+60℃.
1.2.2PMMA dosimeter
2 Terminology
Absorbed dose: 0.2~50kGy
Absorbed dose rate: 1×10-2~1×107Gy·s-1Photon energy: 0.1~5MeV;
Irradiation temperature: -20~+50℃.
2.1 Absorbed dose D
The quotient of de divided by dm, where de is the average energy imparted by ionizing radiation to a substance of mass dm. The unit of absorbed dose is gray, symbolized by Gy.
D=de/dm
1Gy=1J/kg
The same batch of dose meters with the same quality and composition produced by the same process. 2.3 Radiochromic film dose meter
It is a special film containing a certain hidden color dye (such as para-fuchsin cyanide, hexahydroxyethyl para-fuchsin, etc.). After being irradiated with ionizing radiation, this film changes from colorless to color. After being calibrated with a standard dose meter, the absorbed dose can be determined by measuring the change in absorbance at the selected wavelength.
2.4 Polymethyl methacrylate (PMMA) dosimeter Approved by the State Administration of Technical Supervision on May 4, 1994, and implemented on March 1, 1995
GB/T15053-94
A dosimeter made of specially made PMMA material sealed in a packaging bag. The absorbance change value caused by this dosimeter after irradiation with ionizing radiation is a function of the absorbed dose.
2.5 Dose measurement system
A system for measuring dose consisting of a dosimeter, related analytical instruments and a dose response calibration curve (or dose response function). 2.6 Absorbance change value △A
The change in the absorbance of the dosimeter caused by irradiation measured at a selected wavelength, that is, the difference in the absorbance of the dosimeter before and after irradiation. AA=|A-A.|, where Ao and A are the absorbance of the dosimeter before and after irradiation, respectively. 2.7 Absorbance change value k
Absorbance change value △A divided by the thickness of the dosimeter t (mm) = △A/t. The unit is mm-1. 2.8 Verification
All work performed to evaluate the metrological characteristics of the measuring instrument and determine whether it meets the requirements of the verification procedures. 2.9 Calibration
All operations to determine the relationship between the radiation response of the dosimeter and the absorbed dose under specified conditions. 2.10 Calibration curve
The curve (or mathematical relationship) that represents the corresponding relationship between the absorbance change value and the absorbed dose of the same batch of dosimeters of a given type, also known as the dose response curve (or dose response function). 2.11 Calibration device
A device used to calibrate the dosimeter, consisting of an ionizing radiation source, a standard dosimeter and related instruments and equipment. 2.12 Traceability
The characteristic that enables the measurement results to be linked to the national absorbed dose benchmark through a continuous comparison chain. 3 Significance and Use
3.1 Radiochromic Film and PMMA Dosimetry System provides a method for measuring the absorbed dose in materials expressed as water absorbed dose. Under the action of ionizing radiation, a radiochemical reaction occurs in the dosimeter, changing the original visible or ultraviolet absorption spectrum. The change in specific absorbance is measured at a selected wavelength in this radiation-induced absorption region, and the absorbed dose is determined based on a calibration curve or a corresponding functional relationship that can be traced back to the national standard. Some radiochromic films and PMMA dosimeters are listed in Appendix A (Supplement). 3.2 Radiochromic Film and PMMA Dosimetry System is widely used in radiation processing of various products, such as radiation chemicals, sterilization of medical supplies and food preservation.
Instruments and Equipment
4.1 Radiochromic Film Dosimeter.
4.2 PMMA Dosimeter.
4.3 Spectrophotometer (or special reader) The wavelength range, accuracy and reproducibility of wavelength and absorbance, spectral bandwidth and stray light of the spectrophotometer shall meet the use requirements.
4.4 Irradiation phantom
The calibration work must be carried out at the calibration point in the water phantom or solid phantom with wall materials of polystyrene or plexiglass. The water phantom should be equipped with a bracket and a water-proof sleeve to strictly position the dosimeter, and the solid phantom should be equipped with corresponding channels. The thickness of the material (or water) around the calibration point should be greater than the 6co-ray electron balance thickness (4mm). 4.5 Thickness gauge
The precision of measuring the thickness of the dose sheet is <2% (95% confidence probability). 4.6 Dosimeters, spectrophotometers (or special readers) and thickness gauges should be calibrated regularly in accordance with the law, and their performance should be checked frequently and recorded. 2
5 Calibration of dosimeters
GB/T15053—94
5.1 Radiochromic film and PMMA dosimeters are both relative measurement dosimeters. Each batch of dosimeters must be calibrated before use to establish the traceability of the value.
5.2 Use the standard dose measurement system (according to the national metrological verification procedure JJG775-92) to determine the absorbed dose rate of the calibration point and the radiation Repeatability from source to irradiation position.
5.3 Calibration must be performed at the calibration point in the irradiation phantom. The irradiation phantom should be placed in a uniform radiation field with a suitable dose rate at a distance of 0.3 to 0.6 m from the radiation source at the calibration point. It should be strictly positioned and no other items should be stacked nearby. The temperature of the irradiation phantom is controlled at 20 ± 5 °C, and the irradiation temperature is monitored before and after each irradiation.
5.4 Place the radiochromic film and PMMA dosimeter at the calibration point in the irradiation phantom for irradiation. Clamp the dosimeter with polystyrene or plexiglass strips before and after. The geometric center (measurement point) of the dosimeter should coincide with the calibration point. 5.5 Evenly select seven different irradiation doses within the measurement range of the dosimeter (or take four dose values for each magnitude). Repeat irradiation of 5 dosimeters for each irradiation dose. The dosimeters are grouped into five pieces. 5.6 Use a spectrophotometer (or a special reader) to measure the average absorbance of the irradiated and unirradiated dosimeters at the specified wavelength to obtain the change in average absorbance at different doses.
5.7 Use a thickness gauge to measure the thickness t (mm) of the dosimeter and calculate the change in relative absorbance (mm-1). If the thickness of the commercial radiochromic film and PMMA dosimeter is tested by the production unit and the written nominal thickness and its variation range are provided, the user can directly quote the nominal thickness after confirmation.
5.8 On double logarithmic coordinate paper (for radiochromic film) or ordinary coordinate paper (for PMMA), use the absorbed dose as the horizontal coordinate and the relative absorbance change as the vertical coordinate to draw a dose response calibration curve, or fit it to the most appropriate functional relationship. Formula (straight line, polynomial or exponential function). 5.9 The measurement repeatability of the dosimeter is calculated as follows and controlled within 3%: Sx/at =
E(—)2
/X100%
Where: n—the number of dosimeter groups irradiated with the same dose, n>5; the change in specific absorbance of the group dosimeter, mm—the average change in specific absorbance, mm—secretion (=1,2). R
6 Procedure for use
6.1 Inspection and storage
6.1.1 Check the dosimeter packaging for defects and store it under the conditions recommended in the manufacturer's instructions. 6.1.2 Light (ultraviolet light) may cause some radiochromic films and PMMA dosimeters to change color. Light should be avoided as much as possible during all stages of use. Unpackaged dosimeters should be placed in black paper bags. 6.1.3 Humidity has a significant impact on the radiation response of the dosimeter. The dosimeter should be packaged in a moisture-proof package. Avoid placing the dosimeter without moisture-proof package in an environment with a relative humidity greater than 70% during storage and use. 6.1.4 The surface of the film and PMMA sheet should be smooth and free of spots, marks and scratches. During inspection and use, use tweezers to clamp the corners of the film or hold the edge of the PMMA sheet by hand, and do not touch the surface. 6.1.5 Number the dosimeter before use for identification. 6.2 Irradiation
6.2.1 When performing daily dose monitoring, place the packaged dosimeter at the position to be measured. Under actual radiation processing conditions, it is not necessary to consider whether there is an electronic balance condition between the dosimeter and the surrounding medium. 6.2.2 To prevent the influence of environmental conditions, the dosimeter should be kept in the package before measurement. 6.3 Measurement
GB/T15053—94
6.3.1 Check the surface of the dosimeter and treat it if necessary. 6.3.2 Place the dosimeter in the colorimetric holder and place it in the measurement position. Note that the surface of the dosimeter is perpendicular to the light beam and the light beam is located in the center of the dosimeter.
6.3.3 Determine the average initial absorbance Ao of several dosimeters at the specified wavelength. For dosimeters with relatively dispersed initial absorbance, the initial absorbance of each piece should be measured before irradiation.
6.3.4 Measure the absorbance of the dosimeter after irradiation and calculate the absorbance change value. 6.3.5 Measure the thickness t (mm) of the dosimeter with a thickness gauge, or use the nominal thickness provided by the manufacturer. 6.3.6 Calculate the specific absorbance change value (mm-l). 6.3.7 Find the absorbed dose corresponding to this value from the calibration curve, or calculate the absorbed dose using the mathematical relationship obtained by calibration. 6.3.8 When calibrating and using the dosimeter, the possible influence of factors such as temperature, humidity, light, absorbed dose rate, radiation energy spectrum and the time interval from irradiation to measurement on the measurement results should be considered to make the calibration and use conditions as similar as possible. 6.3.9 The radiation response of some dosimeters does not reach a stable value immediately after irradiation, and special experiments are required, and an appropriate measurement time is selected.
7 Record
7.1 The supplier, type, batch number and production date of the dosimeter. 7.2 Calibration device, calibration date, standard dosimeter, radiation source, irradiation model, calibration location, measuring instrument, environmental conditions, data and processing, establishment of traceability.
7.3 Irradiation date, irradiation location, irradiation time, environmental conditions. 7.4 Measuring instrument, measurement date, measurement conditions, data and processing. 7.5 Absorbed dose value and its precision and uncertainty. 7.6 Tester signature.
8 Error analysis
8.1 The uncertainty of the measurement result is an important indicator of measurement quality. It represents an assessment of the measured value within a certain range of values. The uncertainty of the measurement result contains several components, which can be divided into two categories, A and B, according to their estimation methods: A-type components, standard deviations calculated by statistical methods for repeated measurements; B-type components, approximate "standard deviations" estimated by other methods. The "standard deviation" synthesized by the usual method of synthetic variance (i.e., the square root of the sum of squares of each component) is called synthetic uncertainty. In order to increase the confidence probability, it is necessary to multiply the combined uncertainty by the confidence factor K, taking K=2, and obtain the total uncertainty under 95% confidence probability. 8.2 The error of the dosimeter measurement value must take into account the following factors: 8.2.1 Radiation factors: radiation energy spectrum, dose rate, beam direction, dose range, dose administration method (continuous or fractionated). 8.2.2 Environmental conditions: temperature, humidity, light, atmosphere, surrounding scatterers during irradiation, temperature, humidity, and light of the dosimeter during storage time before irradiation and after irradiation to measurement. 8.2.3 Dose measurement system: composition, thickness, uniformity, production batch, storage time, stability, solidity of the dosimeter, quality control method, error and environmental conditions during calibration, standardization and analysis method of analytical instruments. 8.3 Precision indicates the degree of random error in the measurement result (belonging to Class A error), which usually includes at least two sources: the true response of the dosimeter and the reading of the response by the analytical instrument. The specific value can be determined by multiple measurements of a specific absorbed dose by several dosimeters. 8.4 Deviation includes all non-random factors (class B errors) that contribute to the total uncertainty of the measurement results, including the deviations related to the standard dosimeters and calibration devices used to establish traceability to national standards and the effects caused by the differences in various conditions of standard and on-site irradiation.
8.5 In accordance with this standard, the precision of the absorbed dose measured by the radiochromic film and PMMA dosimeter is 3% (n>5), and the total uncertainty is ≤8% (K=-2).
Radiochromic dye film dosimeter 1)
Purple irradiation display film dosimeter 2)
Radiochromic film dosimeter $)
Radiochromic dye nylon film dosimeter
Radiochromic film dosimeter 5)
Colorless PMMA dosimeter
Red PMMA dosimeter
Amber PMMA dosimeter
GB/T15053—94
Appendix A
Table of some radiochromic films and PMMA dosimeters (supplement)
Measuring method
Visible spectrophotometry, 550nm
Visible spectrophotometry, 570420nm
Visible spectrophotometry, 560nm
Visible spectrophotometry, 556, 600nm
Visible spectrophotometry, 510600nm
Ultraviolet spectrophotometry, 315nm
Visible spectrophotometry, 640nm
Visible spectrophotometry, 603651nm
Note: 1) The leuco dye is para-fuchsin cyanide, and the base film is polyvinyl butyral (PVB). 2) The developer containing a certain leuco form of triphenylmethane dye is coated on the base film, and the base film is polyester sheet. 3) Contains a certain leuco dye, and the base film is polyvinyl alcohol (PVA). 4) The leuco dye is para-fuchsin cyanide, and the base film is nylon. 5) FWT-60, a product of Far West Company of the United States. Additional notes: bzxz.net
This standard is under the jurisdiction of the China Institute of Metrology. This standard is drafted by the China Institute of Metrology. The main drafters of this standard are Li Chenghua, Wu Zhili, Zhang Yanli and Liu Zhimian. Measurement range, kGy1 The uncertainty of the measurement result is an important indicator of measurement quality. It represents an assessment of the measured value within a certain range of values. The uncertainty of the measurement result contains several components, which can be divided into two categories, A and B, according to different estimation methods: Category A components, standard deviations calculated by statistical methods for repeated measurements; Category B components, approximate "standard deviations" estimated by other methods. The "standard deviation" synthesized by the usual method of synthetic variance (i.e., the square root of the sum of squares of each component) is called synthetic uncertainty. In order to increase the confidence probability, it is necessary to multiply the synthetic uncertainty by the confidence factor K, taking K=2, and obtain the total uncertainty under 95% confidence probability. 8.2 The error of the dosimeter measurement value must take into account the following factors: 8.2.1 Radiation factors: radiation energy spectrum, dose rate, beam direction, dose range, dose administration method (continuous or divided). 8.2.2 Environmental conditions: temperature, humidity, light, atmosphere, surrounding scatterers during irradiation, temperature, humidity, and light of the dosimeter during storage time before irradiation and after irradiation to measurement. 8.2.3 Dose measurement system: composition, thickness, uniformity, production batch, storage time, stability, firmness of dosimeters, quality control methods, errors and environmental conditions during calibration, standardization and analysis methods of analytical instruments. 8.3 Precision indicates the degree of random error in the measurement results (class A error), which usually includes at least two sources: the true response of the dosimeter and the reading of the response by the analytical instrument. The specific value can be determined by multiple measurements of a specific absorbed dose by several dosimeters. 8.4 Bias includes all non-random factors that contribute to the total uncertainty of the measurement results (class B error), including the deviations related to the standard dosimeters and calibration devices used to establish traceability to national standards and the effects caused by the differences in various conditions of standard and on-site irradiation.
8.5 In accordance with this standard, the precision of the absorbed dose measured by radiochromic film and PMMA dosimeter is 3% (n>5), and the total uncertainty is ≤8% (K=-2).
Radiochromic dye film dosimeter 1)
Purple irradiation display film dosimeter 2)
Radiochromic film dosimeter $)
Radiochromic dye nylon film dosimeter
Radiochromic film dosimeter 5)
Colorless PMMA dosimeter
Red PMMA dosimeter
Amber PMMA dosimeter
GB/T15053—94
Appendix A
Table of some radiochromic films and PMMA dosimeters (supplement)
Measuring method
Visible spectrophotometry, 550nm
Visible spectrophotometry, 570420nm
Visible spectrophotometry, 560nm
Visible spectrophotometry, 556, 600nm
Visible spectrophotometry, 510600nm
Ultraviolet spectrophotometry, 315nm
Visible spectrophotometry, 640nm
Visible spectrophotometry, 603651nm
Note: 1) The leuco dye is para-fuchsin cyanide, and the base film is polyvinyl butyral (PVB). 2) The developer containing a certain leuco form of triphenylmethane dye is coated on the base film, and the base film is polyester sheet. 3) Contains a certain leuco dye, and the base film is polyvinyl alcohol (PVA). 4) The leuco dye is para-fuchsin cyanide, and the base film is nylon. 5) FWT-60, a product of Far West Company of the United States. Additional notes:
This standard is under the jurisdiction of the China Institute of Metrology. This standard is drafted by the China Institute of Metrology. The main drafters of this standard are Li Chenghua, Wu Zhili, Zhang Yanli and Liu Zhimian. Measurement range, kGy1 The uncertainty of the measurement result is an important indicator of measurement quality. It represents an assessment of the measured value within a certain range of values. The uncertainty of the measurement result contains several components, which can be divided into two categories, A and B, according to different estimation methods: Category A components, standard deviations calculated by statistical methods for repeated measurements; Category B components, approximate "standard deviations" estimated by other methods. The "standard deviation" synthesized by the usual method of synthetic variance (i.e., the square root of the sum of squares of each component) is called synthetic uncertainty. In order to increase the confidence probability, it is necessary to multiply the synthetic uncertainty by the confidence factor K, taking K=2, and obtain the total uncertainty under 95% confidence probability. 8.2 The error of the dosimeter measurement value must take into account the following factors: 8.2.1 Radiation factors: radiation energy spectrum, dose rate, beam direction, dose range, dose administration method (continuous or divided). 8.2.2 Environmental conditions: temperature, humidity, light, atmosphere, surrounding scatterers during irradiation, temperature, humidity, and light of the dosimeter during storage time before irradiation and after irradiation to measurement. 8.2.3 Dose measurement system: composition, thickness, uniformity, production batch, storage time, stability, firmness of dosimeters, quality control methods, errors and environmental conditions during calibration, standardization and analysis methods of analytical instruments. 8.3 Precision indicates the degree of random error in the measurement results (class A error), which usually includes at least two sources: the true response of the dosimeter and the reading of the response by the analytical instrument. The specific value can be determined by multiple measurements of a specific absorbed dose by several dosimeters. 8.4 Bias includes all non-random factors that contribute to the total uncertainty of the measurement results (class B error), including the deviations related to the standard dosimeters and calibration devices used to establish traceability to national standards and the effects caused by the differences in various conditions of standard and on-site irradiation.
8.5 In accordance with this standard, the precision of the absorbed dose measured by radiochromic film and PMMA dosimeter is 3% (n>5), and the total uncertainty is ≤8% (K=-2).
Radiochromic dye film dosimeter 1)
Purple irradiation display film dosimeter 2)
Radiochromic film dosimeter $)
Radiochromic dye nylon film dosimeter
Radiochromic film dosimeter 5)
Colorless PMMA dosimeter
Red PMMA dosimeter
Amber PMMA dosimeter
GB/T15053—94
Appendix A
Table of some radiochromic films and PMMA dosimeters (supplement)
Measuring method
Visible spectrophotometry, 550nm
Visible spectrophotometry, 570420nm
Visible spectrophotometry, 560nm
Visible spectrophotometry, 556, 600nm
Visible spectrophotometry, 510600nm
Ultraviolet spectrophotometry, 315nm
Visible spectrophotometry, 640nm
Visible spectrophotometry, 603651nm
Note: 1) The leuco dye is para-fuchsin cyanide, and the base film is polyvinyl butyral (PVB). 2) The developer containing a certain leuco form of triphenylmethane dye is coated on the base film, and the base film is polyester sheet. 3) Contains a certain leuco dye, and the base film is polyvinyl alcohol (PVA). 4) The leuco dye is para-fuchsin cyanide, and the base film is nylon. 5) FWT-60, a product of Far West Company of the United States. Additional notes:
This standard is under the jurisdiction of the China Institute of Metrology. This standard is drafted by the China Institute of Metrology. The main drafters of this standard are Li Chenghua, Wu Zhili, Zhang Yanli and Liu Zhimian. Measurement range, kGy
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