The scope of radiological protection

Draft document: The scope of radiological protection
Submitted by Anatoly F Tsyb (via ICRP Sci.Secr), Russian Scientific Commission on Radiological Protection
Commenting on behalf of the organisation

Comments on the ICRP draft “The scope of radiological protection regulations” and corresponding comments on the ICRP draft “2005 Recommendations of the International Commission on Radiological protection” The Russian Scientific Commission on Radiological Protection (RSCRP) support the exemption concept as it is defined in the Chapter 5 of the document “The scope of radiological protection regulations”. The RSCRP considers the principal of low individual risk and the principal of optimization defined by the sections 5.2.1 and 5.2.2 as the most important ones. In connection with the exemption concept the RSCRP lays stress on the necessity of the Chapter 7 “The optimization of protection” in the previously discussed document “2005 Recommendations of the International Commission on Radiological protection”. The concrete definition of the optimization principal on the level of up-to-date radiation-epidemiological knowledge is crucial for the practical use of the exemption concept. This principal was well supported by the section 7.2 “Distribution of exposures in time and space” of the document “2005 Recommendations of the International Commission on Radiological protection”. It is very important to keep in the text of the “Recommendations” the modern concept that the individual risks can be modified by the time and space distributions of exposures and by the characteristics of the exposed individuals (gender, age, etc.). This concept (which could be introduced, for example, by the document IAEA-TECDOC-870 “Methods for estimating the probability of cancer from occupational radiation exposure”) should be used in the implementations of the principals of low individual risk and optimization. In particularly, the term “dose matrix” was introduced in the section 7.2 of the “2005 Recommendations”. We consider this ICRP innovation as the very important one for the practical implementation of the exemption concept. It is extremely advisable to preserve this term in the final version of the “Recommendations”. In addition, the RSCRP had the proposals to the section “Radiation weighting factors for neutrons” of the draft “2005 Recommendations…”: Proposal 1. Add to the paragraf 68 after the first sentence: “The following factors and processes are taken into consideration in transition from the biological effectiveness of neutrons to the radiation weighting factor for incident radiation: the quality factor for radiation, absorbed in the macroscopically small elementary volume at the point of interaction; the transformation of incident radiation in the large volume, such as is the human body.” Proposal 2. Replace the last sentence in the paragraf 68 by the following: “Step function with the values, represented in Table 1, or continuous function, recorded in the form (1) is recommended to use or to calculation radiation weighting factors for neutrons”. Table 1 En WR’ 2 ÌýÂ<En<20 ÌýÂ 8 0.5 ÌýÂ<En<2 ÌýÂ 12 0.05 ÌýÂ<En<0.5 ÌýÂ 7 En<0.05 ÌýÂ 2 WR = 2+11*exp{-[ln(2En)]2/6} +3*exp{-[ln(0.05En)]2/0.6} 0.025 ýÂ<En<20 ÌýÂ (1). Foundations of the proposals: The numerical values proposed are obtained as a result of the calculations of doses and effective quality factors in the anthropomorphous heterogeneous phantom. In detail the foundations are presented in the publication: Klass E.V., Rezontov V.A., Shakhovskiy V.V. Some questions of the definition of n effective dose of neutrons at n external irradiation. - Atomic Energy, Vol. 87, iss. 4, 1999, p. 297-302 (in Russian). As the results: 1) Problematic question is solved radically. It does not retain the postponed omissions; 2) Coordination between the radiation protection quantities and the operational quantities is reached in the entire range of neutron energy. The regret on the absence of this coordination speaks out in the division 4.4, ICRP Publication 92; 3) The hyperconservatism which was being formed as a result of the chain of conservative overstating in the procedure of the selection of the radiation weighting factor WR values is excluded. The conservatism of the estimations of effective dose and operating values remains. It is created by the conservative overstating, which remain in the quality factor Q(L) values. More detailed substantiations can be presented for inclusion into the Annex B if necessary.