The initial as well as a continuing objective of ICRU is radiation protection of radiologists and patients, originally only against X- and gamma rays. Since the 1950’s, the field of radiation protection has widened to occupational exposures of radiation workers and the environmental exposure of the general public and to exposures to other types of ionizing radiation. ICRU has upheld a continuous awareness of conceptual and metrological issues in the field of radiation protection.

ICRU work on conceptual aspects of radiation protection included the introduction of the quantity dose equivalent in 1962 permitting to account for radiation quality. After the introduction of effective dose equivalent by ICRP as the central, but not measurable, radiation protection quantity, ICRU developed and introduced the (measurable) operational quantities to enable the assessment of the protection quantity for exposures to external radiation. The ICRU operational quantities were introduced in ICRU Report 39 (1985) and ICRU Report 43 (1988). Guidance for the measurement of these operational quantities Report 47 (for photons) (1992) and in Report 66 (for neutrons) (2001).  A revision and update of the concept and practical implementation of operational quantities can be found in Report 95 (2020) on Operational Radiation Protection Quantities for External Radiation (published jointly with ICRP).

Concerning conceptual aspects, more recently ICRU published Report 86 (2011) on Quantification and Reporting of Low-Dose and Other Heterogeneous Exposures.

As part of its remit, ICRU has published basic data to be used in operational and practical radiation protection. In 1998 ICRU published Report No. 57, Conversion Coefficients for Use in Radiological Protection Against External Radiation (also published as ICRP Publication 74). An update, Dose Conversion Coefficients for Radiological Protection Quantities for External Radiation Exposure, was prepared jointly with ICRP, and published as ICRP Publication 116 (2010). Reference Data for the Validation of Doses from Cosmic-Radiation Exposure of Aircraft Crew was published jointly with ICRU in Report 84 (2010).

In the field of radiation protection measurements, ICRU has given guidance and recommendations on specific techniques/procedures: in Report 53 (1994) on Gamma-Ray Spectrometry in the Environment, in Report 56 (1997) on Dosimetry of External Beta Rays for Radiation Protection, in Report 69 (2003) on Direct Determination of the Body Content of Radionuclides, in Report 88(2012) on Measurement and Reporting of Radon Exposures. Report 68 (2002) on Retrospective Assessment of Exposures to Ionizing Radiation has been updated and complemented by Report 94 (2019) on Methods for Initial-Phase Assessment of Individual Doses Following Acute Exposure to Ionizing Radiation.

In the field of environmental exposures, ICRU published Report 65 (2001) on Quantities, Units, and Terms in Radioecology, and Report 75 (2006) on Sampling for Radionuclides in the Environment, and Report 53(1994) on Gamma-Ray Spectrometry in the Environment. Based on experience and lessons learned after the nuclear accidents of Chernobyl and Fukushima, ICRU published Report 92 (2015) on Radiation Monitoring for Protection of the Public After Major Releases of Radionuclides to the Environment.