|ICRP-2006 has much improved since the previous discussion in 2004/2005. However, it is still not such coherent and logic as its predecessors were. The writer has some comments of both general and specific nature.
The Principles. Formally the principles of radiation protection did not change much; all the three of them remained on place with almost the same names. However, as can be judged from the further text, it is suggested that in reality the Optimisation principle and especially its implementation change substantially.
The optimization becomes now a way of thinking and migrates far away from well defined quantitative optimization methodologies developed in ICRP-37 and ICRP-55 to less defined qualitative ones. There is now more attention paid to public perception and stakeholder involvement issues and less attention to cost-benefit analysis and averted dose. On the one hand this gives more space for multifaceted approach for highly educated regulators and practitioners but, on the other hand, immediately complicates practical implementation of the optimization principle by most of practitioners. The latter would definitely prefer more concrete recommendation and quantitative criteria. The existing FD on optimisation does not compensate this shortage.
In the new Constrained optimization, the concept of constraint becomes the central one. Unfortunately definition of constraint and especially scientific basis for selection of constraint values for different exposure situations/categories is still far from being clear, see specific comments below. The document may benefit a lot from current consultation namely in the area of specification of the constraint quantity.
2.2. (30) The principle of optimisation should be shortened; otherwise it reads as explanation of the principle, not principle itself. The suggested option:
“The principle of constrained optimisation: The level of protection should be the best under the prevailing circumstances, i.e., maximising the margin of good over harm. Optimisation involves keeping exposures as low as reasonably achievable taking into account economic and societal factors, as well as any inequity in the distribution of doses and benefits amongst those exposed.”
Dose and risk constraints as instrument of constrained optimization can be defined later in the text.
(159) This seems to be the first time that constraint quantity appears in the main text. It’s a good place to define it, see, e.g. (184).
5.2. Types of exposure situations. Aiming at terminology simplification, I’d suggest to shorten this title and call this section simply “5.2. Exposure situations”. Accordingly, to avoid the word ‘Type’ in this context, e.g.:
(162) The Commission intends its recommendations to be applied to all sources in the following three exposure situations which address in total all conceivable circumstances:
Same (162): extend definition of existing exposure situations as follows:
· existing exposure situations are exposure situations that already exist when a decision on control has to be taken, including natural background radiation and residues from past practices that were operated outside the Commission’s recommendations and from past emergencies.
(173) and (215): Give rationale why “Relevant constraints should be higher than those for individuals in the general population”.
(202) Logic of constraint selection might be strengthened as follows: “In providing guidance on values for dose constraints, the Commission has assumed a linear relationship between radiation dose and risk of cancer or hereditary effects in exposed organs or tissues. The Commission considers that, for the purposes of radiological protection, the assumption of linearity applies up to acute or annual doses of about 100 mSv. At higher doses, there is an increased likelihood of tissue injuries and a significant risk of stochastic effects. For these reasons, the Commission considers that the maximum value for a constraint is 100 mSv incurred either acutely or in a year. There is no net individual or societal benefit that can compensate for higher levels of exposures, except in extreme situations such as the saving of life or the prevention of a serious catastrophe.”
(204) Last sentence “The corresponding doses would represent a marginal increase above the natural background and are at least two orders of magnitude lower than the maximum value for a constraint, thus providing a rigorous level of protection.” Needs clarification for a lay reader.
(205) and Table 4. First sentence claims that the 2nd band “applies in circumstances where individuals receive direct benefits from an exposure situation but not necessarily from the exposure or the source of the exposure, itself.” In the last sentence it says that “In the event of an accident, countermeasures such as sheltering and iodine prophylaxis would fall within this band.” Then clarification is needed what are the benefits from an accident.
Actually, I would suggest to replace the first sentence with the following: “The second band, from 1 mSv to 20 mSv, applies in circumstances where individuals receive direct benefits from an exposure situation (in case of practice) or by avoidance of disturbing intervention in case of emergency (e.g., evacuation) or in existing situation (e.g., resettlement). ”
(213) Suggested modification for the first bullet:
· “For rescue operations involving the prevention of serious injury or the development of catastrophic conditions, every effort should be made to avoid serious tissue injuries by keeping doses below about 1000 mSv and, ideally, to avoid other tissue injuries by keeping doses below 100 mSv, the Commission's maximum value for a constraint.”
(221) In this important para on optimization, costs of protection are not mentioned at all. Even if it suggested that optimization becomes a multifaceted process, cost-benefit issues should not be totally ignored.
(230) This para is totally irrelevant to the subject of 5.8.7 Application of optimisation and constraints. Suggest to delete it or to move to 4.5.7 Collective Doses.
(231) From the context one can guess that it is about collective dose. It would be useful to specify that. Otherwise, the statement “The Commission is of the opinion that in the decision-making process, more weight could be given to moderate and high doses…” becomes trivial and unnecessary. However, if it is about collective dose, then this idea is in strong contradiction with LNT confirmed in Section 3 for radiation protection purposes. As LNT is accepted, there is no reason to neglect contribution of low doses to the collective dose.
Same para (231) “The Commission does not intend to give detailed guidance on such weighting, but rather stresses the importance of demonstrating in a transparent manner how any weighting has been carried out.” Who will do respective recommendations if not the Commission? I’d rather consider development of the relevant guidance in a separate ICRP document.
5.9. Dose limits. It would be important to mention in this section that the concept of dose limits is based on the concept of acceptable risk. This important link is missing here.
(240) “Dose limits do not apply in situations where the exposed individual is engaged in life saving actions or is attempting to prevent a catastrophic situation.” Not only, they are not applicable in emergencies and existing situations either.
(280) “In many cases it will be obvious that action to reduce exposures is not warranted. This conclusion will often be intuitive.“ Suggest to replace the word “intuitive” with the expression “based on common sense”.
(286) See the suggested specification: “The overall contribution of 40K is substantial but is fairly constant and is limited by the body’s content of potassium and not by the amount of potassium in the diet.” All the consumed potassium is first absorbed in GIT and then the extra amount excreted quickly. It’s not an uptake issue.
By the way, the next sentence in (286) seems not completed.
(339) “The intervention levels given in those publications (ICRP Publications 60 and 63) are now regarded as constraints.” This note substantially, although implicitly, changes application of the indicated quantities. According to ICRP Publications 60 and 63, the protection actions should be undertaken when the intervention or action levels are exceeded. In contrast, the suggested approach requires application of optimised actions below the constraints. If this is the new ICRP position, it should be explicitly clarified.
The same is relevant to the existing situations, (340) to (342).
That is all for now. As for specific comments and some editorial suggestions in the Dosimetry section, these will be discussed first at C2 meeting in October.