2005 ICRP Recommendation

Draft document: 2005 ICRP Recommendation
Submitted by Staff of NSRW Division, IAEA
Commenting on behalf of the organisation

DRAFT 2005 RECOMMENDATIONS OF THE INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION COMMENTS OF THE RADIOLOGICAL PROTECTION PROFESSIONALS OF THE IAEA SECRETARIAT PART A INTRODUCTION The IAEA has a statutory responsibility for establishing safety standards, which it has carried out since the 1950s. The Board of Governors stated as long ago as 1960 that: “The Agency’s basic safety standards … will be based, to the extent possible, on the recommendations of the International Commission on Radiological Protection (ICRP)”. Since that statement was made, successive revisions of the Basic Safety Standards have indeed been based on the ICRP recommendations, with the consequence that there has been and still is substantial harmonization of national approaches to radiological protection throughout the world. There is considerable value in preserving this degree of harmonization and therefore the IAEA Secretariat will need to give careful consideration to any proposed new ICRP recommendations. The draft 2005 ICRP recommendations were issued for comment in June 2004. The comments that are given below have been prepared by the radiological protection professionals of the IAEA Secretariat with the aim of assisting ICRP in the development of recommendations that can be used as the basis for improvement in the Agency’s safety standards and thereby preserve the harmonization of approaches throughout the world. As such, they are focussed on the possible impact of the draft on the IAEA Safety Standards, including the Safety Fundamentals, Safety Requirements, such as the International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources, and supporting Safety Guides. Consideration has been given to whether any particular recommendation that may require a change to the IAEA Safety Standards will produce a positive net benefit. In this context, it is noted that the IAEA Safety Standards form the basis for regulations in many of its Member States, and therefore any change to the Safety Standards may well be associated with significant costs to Member States. In the process of collating these comments, some additional comments have however been included where these have been seen as being helpful to ICRP. GENERAL COMMENTS 1. The IAEA professionals welcome the openness of the approach adopted by ICRP with respect to its proposed 2005 recommendations. 2. The IAEA professionals welcome the intention of ICRP to clarify its guidance on practices and intervention, recognizing that there has been some debate over the use of these terms since the publication of the 1990 recommendations. However, they feel that further explanatory text is needed in the document in order to assist the reader in understanding how the approach has changed between the 1990 to the 2005 recommendations. 3. The IAEA professionals welcome the intention to simplify the protection systems and to reduce, where appropriate, the number of criteria for protection, particularly where this leads to improvement in protection, which should be the dominant goal of any new recommendations. In providing this simplification, again they feel that further clarification of the changes between the 1990 and the 2005 recommendations would be useful, particularly with regard to the stronger focus on source-related restrictions on dose. 4. The IAEA professionals believe that the principle of justification is an important one and, while recognizing the difficulties in and responsibilities for its application, it feels that it should be explicitly retained because of its universal acceptance. Again, more explanatory text dealing with the issues involved in its application would be useful; such text might, for example, clarify and further develop the points given in the two paragraphs on justification in the 1990 recommendations and explain how the principle might be applied in different circumstances, although it is recognized that ICRP should not pronounce on the justification for any particular practice involving radiation exposure. 5. The IAEA professionals note that the meaning of dose constraints has been broadened and feels that such a major change should be supported by more explanation with clear links being made with the way the term has been used following the 1990 recommendations. In particular, they note that the term in the IAEA safety standards has different meanings according the circumstances and is specifically related to the principle of optimization of protection. The broader meaning of the term has led to it being applied to different dose quantities – e.g. incremental or total dose – and the IAEA professionals feel that the explanation should specifically address this matter to avoid subsequent confusion in the use of the 2005 recommendations. ICRP might, for example, wish to give consideration to defining a separate term for source-related dose limits rather than change the concept of ‘dose constraint’, and, in so doing, clearly distinguish between the various dose quantities to which it is applied. Further, one of the valuable features of ICRP recommendations until now has been the promotion of a high level of international harmonization in radiation protection. The adoption of just 3 ‘maximum’ dose constraints might usefully be accompanied by an indication of how constraints for particular situations could be established in order to retain international harmonization. SPECIFIC COMMENTS Controllable source ICRP proposal Controllable source is the all-encompassing term. Practice is retained as a component but intervention is no longer used. Impact on Safety Standards. The BSS and other Safety Standards have made use of the two concepts of practice and intervention. A revision of these standards to accommodate the ICRP proposal would involve some effort, although it could be considered during the normal process of review and revision. Comments Controllability has been inherent in previous ICRP recommendations; indeed, the terms ‘practice’ and ‘intervention’ are reflections of this. The proposed new recommendations are therefore consistent with these concepts. However, the IAEA professionals would not wish to see weakened the distinction between what is planned (and optimizing the protection to be applied to the increase in exposure) and what is a response to an existing situation (and optimizing the protection to be applied to the reduction in exposure). For this reason, again, they feel that more explanatory material would help the reader understand the intentions of ICRP. This is seen as necessary to limit any confusion that might result from the broader use of the term dose constraint, which in the 2005 recommendations applies to all types of exposure situations that can be controlled - “normal situations”, “emergency situations”, and “controllable existing situations”. Furthermore, while IAEA professionals welcome the concept of controllability, they feel that the recommendations might clarify the judgements that will still be required in determining what is in fact controllable. In this context, a link might be made between controllable source and exclusion. In addition, they feel that it would be useful if the recommendations provided guidance on how intervention situations should be handled in view of the fact that the concept of intervention is no longer used. In summary, the IAEA professionals feel that a clear explanatory bridge needs to be provided that takes the reader from the 1990 to the 2005 recommendations. Dose constraint (general) ICRP proposal This term is no longer used to define a prospective restriction on dose as a part of the optimization of protection within practices. It has a much broader significance, including retrospective and regulatory use, and covers intervention situations as well. Impact on Safety Standards The term has a specific definition within the BSS. Significant effort would be required to modify the BSS and associated Safety Standards. While there is likely to be benefit from the establishment of source-related restrictions on exposure, the proposal to change the meaning of an existing term is questioned. Comments By broadening the concept of “dose constraint”, ICRP is proposing a fundamental shift in the approach to radiation protection. Indeed, this is arguably the only real change in the radiological protection policy contained in the proposed new recommendations. Changing the meanings of terms and of the concepts to which they apply is likely to cause confusion and for that reason, clear explanation of the change will be needed. Although ICRP has already explored the use of other terms in this context, the IAEA professionals feel that the search should be continued. In particular, it recommends that the use the 1990 definition of dose constraint should be continued and perhaps further explained and (a) new term(s) defined to cover source-related dose limits. The IAEA professionals consider that the proposal that regulators should set their own dose constraints, which may become mandatory, could lead to different approaches between countries, and, could well militate against the efforts of the IAEA in promoting harmonized radiation protection standards across its Member States. The maximum dose constraints proposed in Tables S1 and 7 (paragraph 65), because they relate to substantially different situations, namely normal, emergency and existing controllable exposure, need substantially more explanation to avoid confusion. The IAEA professionals are concerned that the justification for the figures in Tables S1 and 7 on the basis of background levels may not be sufficient. This approach implicitly suggests replacement of the well-developed and defensible risk evaluation approach. Furthermore, they note that the use of typical background levels does not in fact avoid an implicit consideration of the risk presented by these levels. They nevertheless accept that exposure to natural sources of radiation does provide some perspective to the dose criteria that ICRP has adopted. Dose Constraint (general) ICRP proposal A proposed minimum dose constraint of 0.01 mSv in a year, with the impression of optimization below this level. Impact on Safety Standards The BSS indicates that this is a dose below which a justified practice may be exempted without further consideration. The actual implication for the BSS may not be significant, but would need to be explored. Comment The value of 0.01 mSv in a year has gained international acceptance as being a ‘trivial’ level of dose and is used as a basis for the exemption of justified practices. The idea that optimization of protection could be carried out even at lower levels of dose needs more explanation to avoid undermining the agreement that has already been reached. In particular, the IAEA professionals note that it would be inappropriate for the regulator to devote significant resources to dealing with ‘trivial’ doses. The discussion on the use of the value of 0.01 mSv in a year as a dose constraint therefore needs to explain how it would be used. In particular, its inclusion in Tables S1 and 7 and the discussion in paragraph 161 need development. Justification ICRP proposal Justification is no longer given as a fundamental principle of protection. ICRP has aimed to apply its system of protection to practices that have been declared justified. Since the concept of intervention is not fundamental to the proposed recommendations, the principle of justification in this context is not explicit. Impact on Safety Standards The justification principle is fundamental to the BSS, in relation to practices. Its removal as a basic requirement in any revision of these standards might be reasonable because experience has shown that there are difficulties associated with making this a regulatory requirement (although the principle remains valid). Justification of intervention, where radiation protection considerations dominate, is not explicitly dealt with, so it is not clear whether there are implications for the Safety Standards. Comments The IAEA professionals would recommend that the matter of justification be dealt with very carefully. It is an established and accepted fundamental principle and any change to this must be fully explained to avoid unnecessary confusion. It is true that responsibility for judging the justification of a practice usually falls on governments or their agencies, and radiological protection considerations are only one input to the decision, but that does not reduce its value as a fundamental principle. The real problem with it has been its incorporation into international standards and national regulatory documents. Indeed, it could be argued that it is not strictly a regulatory matter, although that depends on the nature of the practice being considered. The reasons given for its ‘removal’ as a basic principle are therefore really reasons why additional guidance is necessary. Additional guidance, such as for screening of people for security reasons, could be developed by other bodies, but since ICRP has given it such weight over the years, it would be desirable that the ICRP contribute to that guidance, although it should not pronounce on any particular practice. Furthermore, protective or remedial actions to avert dose in intervention situations must be justified. In such situations, radiation protection considerations feature strongly and it would be helpful if this were discussed. Exclusion ICRP proposal The proposal is essentially that low doses, or amenability to control (the former is in fact a pragmatic example of what is unamenable to control) should be used as the basis for exclusion, and that this approach can be applied to both natural and artificial sources. Numerical values in terms of activity concentrations for exclusion are proposed. Impact on Safety Standards The proposed approach is consistent with RS-G-1.7 (DS161). However, the numerical values in Tables S2 and 10 are different for artificial radionuclides from the levels developed by the IAEA and given in DS161. Comments While the IAEA professionals welcome, in principle, the proposed simplification, they feel that it has to be recognized that there might be some reluctance to accepting the ICRP values for artificial radionuclides given the difficulties in reaching consensus with DS161. They also feel that the approach in the 2005 recommendations should facilitate a better understanding of exclusion and its distinction from exemption. To clarify things further, they suggest that a stronger link should be made with the related concept of controllable source, because, presumably what is not excluded is potentially controllable. The exclusion value for 238U and 232Th should be stated as 1 Bq/g, not 1.0 Bq/g, as it is meant to be an order of magnitude value. Exemption ICRP proposal This is recognized as a form of authorization and a regulatory matter. It proposes a need for activity concentration levels for practical application and states that international agreement would facilitate a consistent regulatory approach worldwide. The principles for exemption set out in ICRP 60 are no longer presented. Impact on Safety Standards With the development of DS161, consideration will need to be given to a thorough review of the exemption requirements and recommendations in the BSS. The concept that it is a regulatory matter is consistent with the BSS approach and the clarification is welcomed. Comments The IAEA professionals suggest that the proposal for the development of exemption levels in terms of activity concentration (beyond those used for the purposes of exclusion) should be omitted from the 2005 recommendations. The levels in DS161, which have implications for exclusion from, and the scope of, regulatory requirements, should be sufficient and additional activity concentration levels would cause confusion. In ICRP 60, the criteria for exemption were (1) the source gives rise to small individual and collective doses in both normal and accident situations and (2) no reasonable control procedures could achieve significant reductions in individual and collective dose. The IAEA professionals feel that these criteria should be retained in the 2005 recommendations. QUANTITIES AND UNITS Quantities and units ICRP proposal Introduce radiation weighted dose and RBE-weighted absorbed dose (Gy-eq.) Impact on Safety Standards Change of terms can readily be implemented during the revision of the Safety Standards. Comments The RBE weighted absorbed dose (Gy-eq.) is useful in planning for avoiding deterministic effects and in management of medical response to emergencies. Quantities and units ICRP proposal Change in radiation and tissue weighting factors. Impact on Safety Standards Change in tissue weighting factors will have implications for the dose coefficients given in the Safety Standards. Revised dose coefficients can only be taken into account when they are available from ICRP. Comments This change has no major implications for safety. The IAEA professionals, in principle, support the use of the latest knowledge, although they recognize that a substantial amount of work could be involved in making changes to the dose coefficients based on the new tissue weighting factors. They also note that the precision of the weighting factors for neutrons and for all other types of radiation is not consistent, and feel that ICRP may wish to consider this further. They also note that any change in the definition of the protection quantities may have implications for epidemiological studies, although these are unlikely to be significant. Change in terminology for health effects ICRP proposal The terms “deterministic effect” and “stochastic effects” are now proposed to be replaced by “tissue reaction” and “cancer development and inheritable disease”. Impact on Safety Standards Revision of the Safety Standards to incorporate new terms can readily be made during their revision. Comments The reason for the change is that the non-expert did not readily understand the term “deterministic effect”. While this may be the case, it is questionable whether the new term will be any more clearly understood — after all, some individuals might equally regard an induction of cancer as a tissue reaction. The IAEA professionals therefore recommend that the decision to change the term be reconsidered and, if still pursued, that the search be continued for an appropriate word to describe those effects that only occur above certain thresholds of dose.