2005 ICRP Recommendation

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

PART B OCCUPATIONAL PROTECTION Occupational exposure ICRP proposal Exposures incurred at work as a result of situations that can reasonably be regarded as being the responsibility of the operating management. Impact on Safety Standards The term ‘occupational exposure’ is defined in the BSS and the definition refers to both exclusion and exemption. Conceptually, there is no change. Types of worker ICRP proposal Workers in ‘controlled areas’ of workplaces are not strictly volunteers, but they are well informed and are specially trained, thereby forming a separate group of informed individuals. Other workers, such as administrative and support staff, might be included in the group of general individuals, and treated as members of the public. Impact on Safety Standards The Safety Standards indicate that workers exposed to radiation from sources other than natural sources that are not directly related to their work or not required by their work receive the same level of protection as if they were members of the public. There is however no such distinction between those workers in controlled and those in supervised areas. The change could be accommodated without too much difficulty, although the need for the change is unclear. Comments This change however reintroduces the concept of ‘radiation worker’, without any definition (see paragraph 175). The implication is that these are workers working routinely in controlled areas. The IAEA professionals feel that ICRP should not introduce this term. It should only use the term occupational exposure and make recommendations regarding when controlled or supervised areas need to be established and the standards of protection that should apply outside of designated areas. Dose constraints and limits ICRP proposal The maximum dose constraint for workers is 20 mSv in a year (Tables S1 and 7). Exceeding a dose constraint may be a statutory offence, reflecting that the proposal has changed their role - see above. The dose limits themselves are unchanged from ICRP 60, with averaging over 5 years being retained. Impact on Safety Standards A substantial change will be required to the BSS and to supporting Safety Guides, which indicate that dose constraints are to be used prospectively for the purposes of optimization of protection, not as limits for regulatory purposes. The change is therefore related to the use of the term ‘dose constraint’; the concept of other reference levels, such as investigation levels, for operational control is not new. Comments The maximum value of the dose constraint of 20 mSv in a year, if used as a regulatory limit is not consistent with the 50mSv maximum in a single year. The ICRP might consider whether an effective dose limit of 20 mSv in a year might be adopted. The flexibility in averaging over 5 years may no longer be needed. If 50 mSv in a single year is maintained as a dose limit, compliance with it should not necessarily preclude a worker from receiving more than 20 mSv from a single source. Optimization of protection ICRP proposal This proposal indicates that the “procedure continues to include the requirement that all doses from a source are as low as reasonably achievable, social and economic factors being taken into account, but is broader than just considering the doses so as to assure safety culture”. Impact on Safety Standards Stakeholder involvement in the optimization process may have significant implications for the Safety Standards. The Safety Guide on occupational exposure, RS-G-1.1, however already recognizes that optimization involves planning and a systematic approach rather than any particular quantitative technique. So in this respect, there is no change. Comments Further explanation of ICRP’s intentions would appear to be necessary in order to avoid confusion. The principle in ICRP 60 gives ‘as low as reasonably achievable …’ essentially as the definition of optimization of protection. ICRP had previously clarified that optimization of protection and ‘ALARA’ were the same (ICRP 42). The 2005 recommendations however appear to indicate that the terms are no longer the same. Furthermore, the involvement of stakeholders needs clarification - see comment on stakeholder involvement in relation to optimization under protection of the public. Radon ICRP proposal Radon is explicitly recognized as a controllable source. The intention appears to be to continue the policy given in ICRP 65. However, 10 mSv in a year (1500 Bq m-3) is given as the maximum dose constraint. Thus the maximum value of the action level in ICRP 65 is changed to a maximum constraint. In addition, countries are recommended to develop their own constraints and then, through application of optimization of protection, ‘to arrive at the most applicable level at which to act in their country’. Impact on Safety Standards The BSS and other Safety Standards use 1000 Bq m-3 as the action level, which is the level above which remedial or protective action should be carried out. In addition, above the action level, occupational exposure to radon is required to be subject to the requirements for practices. If the intention of the proposal is to set a ceiling on the radon concentration, then this would necessitate a significant change to the Safety Standards. It may also imply a standard with which it would be difficult to comply in some circumstances. Comments In Table 8 the existing, widely accepted, upper values of the range of radon action levels given in ICRP 65 (representing the lower bound of the scope of regulatory control) are now proposed as maximum dose constraints (representing the maximum upper bound of acceptable exposure). If this is ICRP’s intention, then it represents a significant conceptual change. In addition, the proposal that countries establish their own constraints and then to apply optimization of protection to arrive at the most applicable level to act could well lead to loss of the harmonization already achieved. This illustrates the problem associated with using the term ‘dose constraint’ for different types of dose. Furthermore, the connection with controllable source has not been clearly made, although it has been with the level for the public – see below. The IAEA professionals recommend that ICRP continue to use the approach given in ICRP 65; indeed, experience with the action level of 1000 Bq m-3 in the BSS leads them to recommend that this be adopted by ICRP. In addition, ICRP might also consider clarifying why radon gas concentration, rather than say the equilibrium equivalent radon gas concentration, is sufficient for the purpose of controlling exposure. PROTECTION OF THE PUBLIC AND ENVIRONMENT Dose constraints ICRP proposal While the dose limit for the public for the sum of exposures from all practices is retained, the proposals place an emphasis on source-related dose constraints. The maximum dose constraint is equal to the average annual effective dose limit, i.e. 1 mSv in a year. Impact on Safety Standards The change to the BSS would not be as substantial as is the case with occupational exposure. Dose constraints for public exposure are defined as the upper bound on the annual dose that members of the public should receive from a controllable source, and are intended to ensure that the sum of doses to the critical group remains within the dose limit. Comments A distinction might be made between the concept of the dose constraint for occupational exposure and that for members of the public, the latter being more akin to a subsidiary limit, on which authorized limits might be based. However, the IAEA professionals note that the value of 0.3 mSv in a year as a maximum dose constraint for discharges is now no longer used in Tables S1 and 7. Yet, this figure has gained some international acceptance as a consequence of earlier ICRP publications. (The 0.3 mSv may be too high for discharges of long-lived radionuclides, due to their build-up in the environment. For these situations, a dose constraint of 0.1 mSv in a year has in the past been recommended by ICRP in Publication 82.) For radionuclides of natural origin, a dose constraint greater than 0.3 mSv and up to 1 mSv in a year may be appropriate. A lot of thought therefore needs to be given to dose constraints for public, as a single level may not be appropriate for all situations. Optimization of protection ICRP proposal See above under occupational exposure. There is a recommendation for disaggregation of doses. Impact on Safety Standards There will be some impact on the Safety Standards. Comments It is noted that the proposal indicates that ‘the exposures that result from the continuous optimization process are levels with which, at a point in time, all parties involved are in agreement as a way to move forward’. It also defines stakeholders as ‘those parties who have interests in and concern about a situation’ and indicates that their involvement is an important input to optimization. The concept that optimization of protection is reached, when there is consensus, is new and needs explanation. In addition, the IAEA professionals feel that as the term ‘stakeholder’ is now being used quite widely but without a clear definition, it would be useful if ICRP were to provide further clarity on who are stakeholders and what their role and authority are. Radon in dwellings ICRP proposal A maximum constraint of 600 Bq.m-3 is proposed. National authorities are to establish constraints below this level, and are expected to apply optimization of protection to find “the most applicable level” at which to act in their country. Impact on Safety Standards This is not consistent with the BSS. In the BSS, the action level is a level above which action is considered; in the proposal, it appears to be more akin to a limit. The value of 600 Bq.m-3 is the maximum of the range given in the BSS. Comments See comment above on radon under occupational protection. For the public, it may not be desirable to establish a pseudo limit (dose constraint) for radon in dwellings. Furthermore, the need for both a dose constraint and a “most applicable level” at which to act is unclear. The IAEA professionals recommend that the approach given in ICRP 65 should continue to be followed and that another term than ‘dose constraint’ be used for the level above which action should be considered. Critical group ICRP proposal For the purpose of assessing compliance with the specified constraint, the use of age-averaged effective dose coefficients and age-averaged habit data is being considered. Impact on Safety Standards The BSS provides dose coefficients for different age groups. The proposed approach will also have implications for the Safety Standards. It should slightly simplify the dose calculations and may allow higher discharges than would be permitted under existing arrangements which focus on the annual dose to the most sensitive age group. Whether or not this new approach is adopted, the dose coefficients in the BSS will need to be changed to take account of the changes in tissue weighting factors. Comments The suggested approach, although pragmatic, is in fact contrary to the present system, which is based mainly on the acceptable risk to the critical group from one year of a practice. If this new approach is to be pursued, it would need the explicit introduction of a dose limitation system based on acceptable risk from lifetime exposure. This is a serious matter and, if adopted, will necessitate careful explanation in the 2005 recommendations. It is also noted that the reference to 10 mSv in a year to a critical group in the case of human intrusion into a waste disposal facility (c.f. ICRP 81) is not discussed, although it is recognized that this could be just an example of an additional level to be set by national authorities. As noted in paragraph 166, (additional) ‘constraints may be recommended by the Commission’s publications dealing with these situations, or may be chosen by operating managements or regulatory agencies’. However, ICRP may wish to consider whether reference to this level should be included in its new recommendations. MEDICAL EXPOSURE Definition of medical exposure ICRP proposal Exposure of individuals undergoing diagnosis, screening, or therapy. ‘But there are also exposures of staff, and near-by members of public, and individuals other than staff, helping in support and comfort of a patient’ (para. 146). Impact on Safety Standards It is not entirely clear whether this is a definition of medical exposure. If it is, then para. 146 of the proposed recommendations implies a change to the definition of medical exposure in the BSS, for which there does not appear to be any clear benefit. Comments BSS defines medical exposure as exposure incurred by patients; by persons others than occupationally exposed helping in support and comfort of patients; and volunteers in biomedical research involving their exposure. The IAEA professionals recommend that ICRP clarify that there is no fundamental change to the definition of medical exposure given in ICRP 60. Justification ICRP proposal The draft recognizes two levels of justification of a procedure – a specified procedure with a specified objective; and, the application of the procedure to an individual patient. Impact on Safety Standards No real change to Safety Standards would be necessary. Comments Para 19 states ‘medical exposure of patients calls for a different and more detailed approach to the process of justification’. The meaning of this is not entirely clear and therefore, the IAEA professionals recommend that further explanation be given. Para 207 refers to generic justification being a matter for the national professional bodies, ‘sometimes in consultation with national regulatory agencies’. The IAEA professionals recommend the deletion of ‘sometimes’, and the addition of ‘health agencies’. ICRP may also wish to consider providing statements about mass screening, particularly for high-dose procedures (e.g. CT) and self-referral. Diagnostic reference levels ICRP proposal These are seen in the draft as a tool in the optimization of patient protection. Impact on Safety Standards No real change to Safety Standards would be necessary. Comments ICRP may wish to mention that diagnostic reference levels should be kept up to date with changes in technology. Dose constraints ICRP proposal Para 225 refers to the guidance in ICRP 73 relating to the protection of helpers and carers, whereas Table 7 recommends a dose constraint of 20 mSv in a year. Impact on Safety Standards The current BSS uses 5 mSv for the dose constraint for comforters. Comments Regarding the maximum dose constraint of 20 mSv in a year for comforters and carers, although the recommendations point to lower constraints, the IAEA professionals suggest that a note might be added that this maximum would not be appropriate for pregnant comforters and for children. Account should be taken on the guidance in the ICRP draft on Release of Patients after Therapy with Unsealed Radionuclides. EMERGENCY PREPAREDNESS AND RESPONSE Framework and key principles as they apply to emergency response ICRP proposal The draft introduces constraints for emergency response. Impact on Safety Standards This would necessitate a change to existing Safety Standards. Comments This is a major philosophical change, the impact of which cannot be assessed at present. Much more explanation is needed to clarify the guidance given in Tables S1 and 7: although the numerical values of the quantities are simplified, the actual meanings of the quantities are different. The concept of avertable dose is lost. While the IAEA professionals recognize the problems involved in applying it, they still see it as a necessary concept to avoid unjustified intervention, for example, evacuating 200,000 people 2 years after Chernobyl for no reduction in dose. There is also no dose constraint for life-saving action. Dose constraints for public ICRP proposal The draft introduces 100 mSv in a year dose constraint for the public for evacuation and relocation and 20 mSv in a year for sheltering and iodine prophylaxis. Impact on Safety Standards This would necessitate a change to existing Safety Standards. Comments The IAEA professionals support the use of 100 mSv for evacuation. However, overall, they feel that the role and use of the dose constraints, which is new in the context of emergencies, needs very careful explanation. Furthermore, they feel that ICRP should clarify that specific countermeasure guidance should be related to the effectiveness of those countermeasures and not to a dose constraint. Threshold estimates for morbidity and mortality ICRP proposal Table 5 provides a summary of judgements on dose-thresholds for radiation induced tissue reactions and mortalities. Impact on Safety Standards The levels in Table 5 are not consistent with draft Safety Standards currently being developed, although if considered appropriate, changes to the draft could still be made. Comments The purpose of the table is not clear: the IAEA professional consider that it should not be given as a basis for criteria for protection, as the values are not the most recent. In addition, the values for mild consequences are mixed with those for severe consequences. It is recommended that Table 5 be deleted, as it is not relevant to the main purpose of the publication. POTENTIAL EXPOSURES Potential exposures ICRP proposal The draft provides some guidance on risk constraints distinguishing between those situations where the forecast effective dose is less than or more than a few hundred mSv. Impact on Safety Standards There would appear to be no impact on the current radiation Safety Standards, but there may be interactions with guidance for facilities. Comments The IAEA professionals feel that the approach needs clarification. In particular, they note that there are no risk constraints; these would appear to be necessary. Contamination with hot particles ICRP proposal Para 239 refers to ‘hot particles’ and recommends that that the derivation of protection criteria be based on the principles described, namely the unconditional probability that members of the public would develop fatal stochastic health effects attributable to the exposure situation. Impact on Safety Standards There would appear to be no impact on the current radiation Safety Standards. Comments The IAEA professionals feel that further guidance is desirable on how to deal with potential exposure from hot particles, such as that covered in para. 150 of the draft of the draft ICRP publication on “Protecting people against radiation exposure in the aftermath of a radiological attack”.