On the Foundation of the System of Radiation Protection | Comments to the ICRP draft 2005 | Kazuaki KATOH, Yukio TATENO and JunIchiro TADA The system of radiation protection consists of two parts; one is the control of radiation field, and the other is the control of individualsf exposure. The Commission defines dose constraints as gthe most fundamental levels of protectionh, which provide the source-related restrictions to protect the most exposed individual from a single source in all situations (paragraph 133). On the other hand, the commission uses dose limits as the levels of protection set for an individual from all sources in normal situations, i.e., individual-related restrictions (paragraph 134). Consequently, it can be understood that Commission is to use dose constraints to control radiation fields and dose limits to control exposure of individuals. The classification, though it is definite, is not kept throughout the Draft, which makes readers into confusion. It should be noted that the source-related restrictions can be applied whether exposure of individuals are monitored or not, while individual-related restrictions can work effectively only when individual dose monitoring is practicable. As the dose monitoring of members of the public is not usually feasible, it is not adequate to apply dose limits to members of the public. Thus, the expression of upper right of Figure 2 in the Draft should be removed. Some people are opposing to the ICRPfs idea of discarding the concept of dose limit to members of the public with the reason that they may receive exposures from more than two sources. In order to avoid this kind of anxiety, we propose to define the concept of the single source as the whole controllable sources under one licence. In addition, we propose that the licence should be issued upon the premise that radiation field at boundaries of the area under control of the licensee, including possible contributions from all radiation facilities having been licensed already, does not exceed a specified level, e.g., 0.1 mSv/w, a worldwide median of natural background radiation level (referring to the UNSCEAR 2000 Report, natural background level, except for the contribution of radon, varies over the world approximately in the range 1 ~ 10 mSv/a). Thus any member of the public would not receive the dose exceeding the dose constraint to the single source. Our proposal also avoids the blame that the concept of the single source is obscure. Dose limits are set so as to suppress individual risk with the stochastic effects below the controlling criteria as well as to avoid the deterministic effects absolutely. Since rights of pursuing benefits and avoiding risks are to be guaranteed equally to people, it seems very difficult to give any rational explanation to the idea that occupational workers in normal situation should bear larger risk than members of the public. We shall respect the right of self-discretion of individual in the principle of democracy, as long as it does not trouble others. Therefore, we propose that the decision-making with practice or intervention, in ICRP terminology, be allowed upon self-discretion for those who have enough knowledge and skill or means of controlling their own individual risk of ionising radiation, hereafter we call them gthe expertsh, as far as exposure to others is proved to be negligible. Nevertheless, some restriction of the exposure, which we call a paternalistic dose limit, should be given even to the experts. It is desirable for good citizens to protect others from extremely miserable consequence, which shall not be overlooked in case it is foreseen. Source-related restrictions consist of the dose constraint in a workspace and that at the boundary of the area under control of the licensee of ga single sourceh. The former should be related to the dose limit so that exposure of the most exposed individual in the workspace is kept almost below the dose limit, while the latter is so determined that any individual accessing to the boundary does not receive exposure beyond the range of variation of natural background radiation level. It should be noted that the dose constraint ensures no one receive larger exposure than the gmost exposed individualh. Thus it is not necessary to recommend the dose constraint at the boundary of the radiation-controlled area (in accord with the policy introduced in 1990 Recommendations). TABLE 1. Our Proposals on the System of Radiation Protection SOURCE-RELATED----------------INDIVIDUAL-RELATED --RESTRICTIONS---------------------RESTRICTIONS----------------SITUATION TO WHICH IT APPLIES (measures of protection)-----------(measures of protection) -----------------------------------------Paternalistic dose limit----------For situations where there is direct benefit for -----------------------------------------(individual monitoring,----------the exposed individuals, who are informed, well- -----------------------------------------working condition)---------------trained, monitored and approved to take the -------------------------------------------------------------------------------practice upon self-discretion, without exposing -------------------------------------------------------------------------------others. Dose constraint to------------------Dose limit--------------------------For situations where there is direct or indirect --work space-------------------------(individual monitoring,----------benefit for exposed individuals, who receive infor- (designing/planning)----------------working condition)--------------mation and training, and monitoring or assess- -------------------------------------------------------------------------------ment. Dose constraint at the---------------------------------------------------For situations having societal benefit, but without the boundary of the area-----------------------------------------------individual direct benefit, and there is no informa- under control of a licensee---------------------------------------------tion, no training, and no individual assessment for (designing/planning)-----------------------------------------------------the exposed individuals in normal situations. The Commission is going to recommend values to the dose constraints and dose limits in the form of annual restriction. However, one year seems to be too long for practices. Hence, we propose to use weekly restriction instead to state dose constraints and dose limits on the condition that the supplemental paternalistic dose limit is provided in the form of dose per practice/mission. It should be emphasised that weekly dose constraints should be kept strictly, though weekly dose limit should be regarded as the controlling targets; i.e., exceeding weekly dose limit should not be considered to the reason of legal punishment unless the annual average of weekly dose exceeds the value. Our proposal of employing shorter period for dose restriction complies with the Commissionfs policy of radiation protection, since the Commission discarded the concept of accumulation of health effects by repealing the maximum permissible accumulated dose in 1966 (Publication 9). We propose the values to the maximum values of dose constraints and values of dose limits as shown in Table 2. TABLE 2. Our proposals of maximum dose constraints and dose limits Maximum value of dose constraint at the boundary of the area under control of a licensee-----0.1 mSv/w Maximum value of dose constraint of work space-----------------------------------------------------------1 mSv/w Dose limit (as annual average)---------------------------------------------------------------------------------1 mSv/w Paternalistic dose limit------------------------------------------------------------------------------------------10 mSv/w ----------------------------------------------------------------------------------------------------------i500mSv/practicej Here the maximum value is to be understood as the upper restriction to regulatory authorities in determining the national regulation values as the Commission explained in the Draft.