3 Operational Quantities for External Exposure

Abstract

To address the need for an extension of both the range of radiation types and energies over which operational quantities are defined while preserving a good approximation to the protection quantities over this extended range, a change of paradigm in the definition of operational quantities is needed. This Report recommends a redefinition of the operational quantities as the products of radiometric or dosimetric quantities at a point in space or on the surface of the body and conversion coefficients related to values of protection quantities (Bartlett and Dietze, 2010; Endo, 2016). Consideration of this approach has been given previously (see, for example, Burlin, 1981; Burlin and Wheatley, 1971; Burlin et al., 1979; Commission of the European Communities, 1983; ICRP Publication 15, 1969; ICRP Publication 21, 1973; Jahr et al., 1981; NCRP Report 38, 1971; Sidwell et al., 1969; Siebert and Bartlett, 19951). The practical application of such a quantity can be made if conversion coefficients to an internationally agreed phantom exist. ICRP and ICRU have now defined ICRP/ICRU adult reference phantoms in ICRP Publication 110 (2009). These phantoms are used to define reference values of conversion coefficients to the protection quantities and can be used to define the operational quantities. The recommended operational quantities simplify the systems of protection and operational quantities and assist in the comprehension of radiological protection quantities by users. A generic scheme is defined here with variations for the different operational quantities introduced in the following subsections. The recommended operational quantities are defined as the product of particle fluence or air kerma and a conversion coefficient. Symbolically, for monoenergetic particles of fluence, Φ, of type R, with energy Ep, this is written as: