ISO 20785-1:2020

Overview

ISO 20785-1:2020 - "Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 1: Conceptual basis for measurements" specifies the conceptual foundation for determining ambient dose equivalent (H(10))* used to evaluate cosmic radiation exposure in civilian aircraft and to calibrate instruments for that purpose. The standard explains the nature of the atmospheric cosmic radiation field at flight altitudes, defines quantities and measurement terms, and sets out principles for calibration, traceability and validation of dose assessments.

Key topics and technical requirements

• Operational quantity: Focus on the ambient dose equivalent H*(10) as the measurable operational quantity used to validate calculated effective doses for crew and passengers.
• Radiation field description: Definitions and treatment of particle fluence, energy and angular distributions for atmospheric cosmic radiation (galactic, solar and secondary particles).
• Calibration principles: Conceptual calibration methods for dosimetric instruments, including traceability to national standards and handling differences between calibration fields and actual atmospheric fields.
• Conversion coefficients: Use and consideration of conversion coefficients to relate measured quantities (fluence, kerma, absorbed dose) to ambient dose equivalent.
• Dosimetric devices: Classification and characterization of measurement devices:
  • Active detectors (for total field components, low-LET/non-neutron, high-LET/neutron components)
  • Passive detectors (thermoluminescent (TLD), photoluminescent, etched track, fission foil, bubble detectors)
• Measurement considerations: Recommendations for simulating aircraft fields, accounting for angular/energy dependence of detector response, and uncertainty management.
• Terminology and traceability: Standardized terms, calibration definitions and requirements for laboratories performing primary and secondary calibrations.

Practical applications and users

• Who uses it:
  • Primary and secondary radiation calibration laboratories
  • Radiation protection professionals in aviation authorities and governmental agencies
  • Airline and aerospace industry safety/health teams
  • Industrial organizations responsible for crew dose assessment and instrument calibration
• Uses:
  • Validating calculated effective doses for aircrew via measurements of H*(10)
  • Calibrating and characterizing dosimeters and survey instruments intended for in-flight use
  • Ensuring consistent, traceable measurements to meet regulatory requirements (e.g., EU Basic Safety Standards, ICRP guidance)
  • Supporting flight scheduling, occupational dose monitoring and pregnant crew protection measures

Related standards and guidance

• Other parts of the ISO 20785 series (measurement and calibration methods for aircraft cosmic radiation)
• ICRP publications and guidance referenced for dose assessment and occupational limits
• EU and IAEA Basic Safety Standards and national regulations that treat cosmic radiation as occupational exposure

Keywords: ISO 20785-1:2020, dosimetry, cosmic radiation, ambient dose equivalent, civilian aircraft, calibration, dosimetric devices, flight crew exposure, calibration laboratories.