Overview
ISO/ASTM 51275:2013 sets forth the standardized practice for the use of radiochromic film dosimetry systems. These systems are employed to measure absorbed radiation doses in materials exposed to photons or electrons, expressed in terms of absorbed dose to water. Classified as Type II dosimeters due to their complex response to influence quantities, radiochromic films serve as reliable tools for routine dosimetry in radiation processing. This standard forms part of a comprehensive framework designed to ensure proper implementation of dosimetry practices and to facilitate compliance with ASTM E2628 requirements. It is closely linked with ASTM E2628 and other standards addressing radiation measurement and uncertainty estimation.
Key Topics
-
Dosimetry System Description: Radiochromic film dosimeters are specially prepared films that visibly change color upon irradiation due to chemical reactions. Their absorbance change correlates to the absorbed dose and can be quantitatively analyzed by spectrophotometers, densitometers, or scanning devices.
-
Measurement Range and Radiation Types: The practice applies to doses from 1 Gy up to 150 kGy, covering photon energies between 0.1 and 50 MeV and electron energies from 70 keV to 50 MeV.
-
Influence Quantities: Various factors can affect dosimeter response:
- Pre-irradiation: Conditioning, packaging, shelf life, temperature, humidity, and exposure to light.
- During irradiation: Temperature, dose rate, dose fractionation, relative humidity, light exposure, and radiation energy.
- Post-irradiation: Time before readout, storage temperature, and potential heat treatment to stabilize response.
-
Calibration and Verification: To ensure accuracy, the dosimetry system must be calibrated under conditions replicating actual use (in-plant calibration). Calibration involves establishing a reliable calibration curve linking dose to measurable absorbance.
-
Measurement Tools:
- Spectrophotometers with traceable calibration for precise optical density readings.
- Densitometers or film scanners, also require calibration standards.
- Dosimeter holders for consistent positioning.
- Optional thickness gauges for film uniformity measurement.
-
Uncertainty Management: The standard emphasizes incorporation of measurement uncertainty analysis, guided by ISO/ASTM 51261 and JCGM documents, to ensure traceability and quality assurance in dose measurements.
Applications
ISO/ASTM 51275:2013 is instrumental in industrial radiation processing environments, such as:
-
Medical Device Sterilization: Ensuring that polymer materials and devices receive correct and uniform radiation doses for effective sterilization without compromising material properties.
-
Food Irradiation: Validating absorbed doses to assure food safety and compliance with regulatory standards.
-
Radiation Processing Quality Control: Routine monitoring of radiation delivery in manufacturing processes utilizing photons or electrons, enhancing process reliability and product quality.
-
Research and Development: Supporting calibration and characterization of new radiation dosimetry systems or materials sensitive to radiation doses.
Related Standards
-
ASTM E2628: Practice for dosimetry in radiation processing, providing foundational concepts relevant to radiochromic film dosimetry.
-
ISO/ASTM 51261: Practice for calibration of routine dosimetry systems specific to radiation processing applications.
-
ASTM E170: Terminology relating to radiation measurements and dosimetry, defining terms used in this standard.
-
ICRU Reports 80 and 85a: Offer in-depth guidance on dosimetry systems and fundamental radiation measurement quantities.
-
JCGM Guides (GUM 1995 and VIM 2008): Provide internationally accepted principles for evaluating measurement uncertainty and terminology in metrology.
Keywords: ISO/ASTM 51275, radiochromic film dosimetry, radiation processing dosimetry, absorbed dose measurement, radiation sterilization, dosimetry calibration, measurement uncertainty, photon dosimetry, electron dosimetry, routine dosimetry system, radiation quality control.