Dosimetric quantities

Draft document: Dosimetric quantities
Submitted by Peter Ambrosi, Physikalisch-Technische Bundesanstalt, Germany
Commenting as an individual

1. New Terms „tissue reactions“ and „ radiation-weighted dose in an organ or tissue“ The introduction of the new terms „tissue reactions“ and “radiation-weighted dose in an organ or tissue” for the old terms “deterministic effects” and “equivalent dose”, which have been used for may years, maybe justified from the scientific point of view, but as there is no change in meaning behind it, I don’t think that this improves the trust in radiation protection. Proposal: Keep the old terms 2. Effective dose The effective dose definition, taken from ICRP 74, uses gender-specific organ and tissue equivalent dose values. The application of this definition is limited (at the end of section 3.3) by saying: The use of reference values and the averaging over both sexes indicates that the quantity effective dose is not aimed at providing an individual dose value for a specific individual human body but for a reference person or group. I conclude from this that e.g. for external exposure of the whole body effective dose values, E, are calculated using gender-specific phantoms and that the E values are used to compare them with the operational quantities to demonstrate there conservatism. Similar, for internal exposure, gender specific biokinetic models are used to calculate the radiation-weighted dose in an organ or tissue and from them the effective dose to specify e.g. limits of intake. The application to specific individuals is forbidden. Such forbidden applications are for me: a) Calculation of the effective dose of an individual from values of radiation-weighted dose in an organ or tissue b) Calculation of an organ dose of an individual from measured Hp(10) or H*(10) values c) Assessment of effective dose from individual monitoring data (see 5.2.1) d) The brochure no. 43 of the German Radiation Protection Organisation (SSK Band 43) If that would be true, the complicated gender-specific formula for E might be justified, as the mean value for a reference person or group has a lower uncertainty than values for individual persons. But for individuals, where the uncertainty might be larger than a factor of two, such a complicated formula is not justified. For that purpose, the old formula of ICRP 60 is more than sufficient. Proposal: Use the new gender-specific formula for reference persons or groups, where the uncertainties of the wT values and to my mind also of the wR values are lower and the effects of individual sensitivity cancels. But use the old and simpler formula for the applications of the effective dose to individuals, see e.g. above nos. a) to d). See also next point on uncertainties. 3. Uncertainties The values (magnitude) of the uncertainties should be mentioned, e.g. for the factors wR and wT, for the biokinetic models, for dose rate dependence, for the individual sensitivity, and so on. It is a valuable information if the uncertainty is of the order of 1 %, 10 % or of a factor of 2 or even larger. The values of these uncertainties depend strongly on the application. If e.g. the uncertainty of the radiation weighting factor is much larger than the differences between the male and female radiation-weighted organ dose, then the complicated gender-specific formula for E might be questionable. Proposal: At least two extreme uncertainty values should be given, the (smaller) uncertainty values for a reference person or for groups and the (larger) uncertainty values for individuals.