Abstract: The International Commission on Radiological Protection (ICRP) introduced so-called protection quantities. The most used protection quantity, the effective dose E, serves to set exposure limits and is used in operational radiation protection to implement the optimization principle.Effective dose, however, is not a measurable quantity. That is the reason why the International Commission on Radiation Units and Measurements (ICRU) introduced measurable (operational) quantities for dosimetry of external radiation to provide acceptable estimates of effective dose.Presently used operational quantities were defined in the 1980s, when nuclear industry was the predominant concern of occupational radiation protection. In other radiation fields, in particular for high-energy radiations, shortcomings of today’s operational quantities became evident: the effective dose can be either over- or underestimated.Based on a comprehensive study, ICRU and ICRP have now introduced new operational quantities for the dosimetry of external radiation to overcome these shortcomings. The new definition of operational quantities is more closely related to the definition of protection quantities including the effective dose, in particular by using the same anthropomorphic phantom. The proposed operational quantities simplify the system of radiation protection quantities—by reducing the difference in the definitions of protection and operational quantities—and provide in general an improved estimate of effective dose. The consequences of introducing new operational quantities on practical dosimetry are discussed in the paper.

Key words: dosimetry, operational quantities, protection quantities, effective dose