|COMMENTS ON ICRP REPORT
DRAFT RECOMMENDATIONS OF THE INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION (Issued June 6, 2006)
S.Y. Chen, Ph.D.
Argonne National Laboratory
Overall, the revised draft Report represents a vast improvement over the previous draft of 2005. One major accomplishment was the removal (or substantial revision) of statements and information that could not be soundly substantiated. However, there are still areas where further improvements are warranted; for example, it is still unclear as to whether the proposed changes are substantial enough to warrant overhauling the existing recommendations. The most important remaining effort is how to convincingly and tightly link the newly recommended areas (such as exclusion and exemption and protection of the environment) to the radiation protection principles and the system of protection that have been so well established. In particular, the unavailability of the key supporting documents for the reference animals (Publication YY, ICRP, 200Y) and for exemption and exclusion (Publication WW, ICRP, 200W) further weakens the basis for supporting the proposed concept and the relevant statements made in the Report. Further refinement of the draft Report is very much needed for this important document to be published. The following paragraphs discuss the areas that need such refinement.
1. Issues Related to Exclusion and Exemption
These concepts lack a solid basis; the arguments offered in the Report are less than convincing. First, we need to ask: “Is the action of Exclusion or Exemption itself a Practice?” That is, shouldn’t one first consult the three principles of protection (i.e., Justification of Practice, Optimization of Protection, and Protection of Individuals) before granting such an action? This ambiguity prevents readers from obtaining a good understanding of the recommended guidance. .
Furthermore, the basis for Exclusion, that is, that some sources are not “amenable” to control, also appears to be quite arbitrary. For example, the action of protecting flight attendants from excessive cosmic ray exposures could be “amenable” but may not be feasible for whatever reasons. Should this be considered an Exclusion, or should it be considered an action to control such an exposure? Who is responsible for determining the action and on what basis? In essence, how do you know a priori that some forms of control may be excluded without a conscientious assessment? Yet again, one needs to know whether the potential exclusion action needs to be first scrutinized for possible consideration as a practice. Without this process, the determination on exclusion appears to be arbitrary (see also G.H. Kramer, “A Commentary on Some Inconsistencies in the ICRP 2005 Recommendations: Exclusion Levels,” Health Physics, pp. 119, Vol. 91, No. 1, 2006).
In the realm of Practice, the term Exemption may refer to actions that are taken a priori (meaning bypassing the control of a practice) and those taken a posteriori (meaning cessation of control from an existing practice; or clearance). The actions to exempt certain materials should still follow the three principles of radiation protection, except that at the exemption level, the effort on optimization may have reached a near optimal point (i.e., a diminishing return for further investment in the ALARA process). This is to restrict the dose constraints to around 10 µSv of the annual dose. Nonetheless, dose constraints higher than this should also be allowed, so long as the three principles are still followed (e.g., if the optimization process should determine it so).
The concepts of Exclusion and Exemption should probably best be explained by the three principles of radiation protection rather than by having to create a separate basis for them. For example, rather than using the word “amenable” for exclusion, one could simply refer to the second principle (Optimization of Protection) to explain that some sources simply have reached the point of diminishing return and that no currently available alternatives can be readily identified. On the other hand, exemption can be considered first for evaluation as a practice unless a “trivial dose (or risk)” has been prescribed as a constraint; in which case, the need for further control would not be warranted. However, exemption need not always be based on the trivial dose (or risk) concept, so long as the constraint remains low (e.g., a few tens of micro-Sieverts per year).
2. Issues Related to the Concept of Protection of the Environment
The entire discussion, specifically Section 10 and the related statement, appears to be premature for inclusion in the Report for the following reasons:
2.1 How is the proposed concept of environmental protection related to the Three
Principles of Protection?
Aside from the first principle of justification, would it be more appropriate to link it to the second principle of optimization or to the third principle of the protection of individuals? Please explain. On the basis of the stated approach in promoting the “Reference Animals and Plants,” it appears that “individuals” in the third principle may also mean animals or plants. If this is the case, what are the appropriate dose limits or constraints for such protection? This confusion alone will surely disqualify the inclusion of such a concept in the proposed Report. A suggested course of action would be to wait until a better and more justifiable basis can be provided (i.e., allow more time for this concept to mature). There is no point in advertising a future concept that cannot be substantiated either scientifically or in any regulatory sense in the guidance.
2.2 It is premature to prescribe the reference animals and plants for protection
purposes (Section 10.2).
The scope and framework of this recommended protection still lack a solid scientific basis. The Report itself acknowledges that “… the human habitat will therefore be afforded a fairly high degree of protection.” Although it is true that “…other exposure situations will arise where environmental consequences may need to be taken into account…,” the proposed approach requires an expanded body of scientific basis as well as a regulatory framework as stated previously.
The very large spectrum of animal and plants species requires a careful evaluation for potential classifications of protection. For example, the proposed “reference animals and plants” concept implies that the proposed protection is for “individual” members of the species, much like the approach for protection of humans. This could be a false premise for the following reasons.
First, the current knowledge on the adverse effects of radiation to biota has not been well established, as have the detriments versus stochastic effects for humans. Without a very good knowledge base, how can an endpoint (or endpoints) be developed by which appropriate protection can be afforded?
Second, it would make more sense to focus on the sustainability of the species rather than on the potential harm to individual members of the species. That is, why not treat biota as “collective beings” in general? Establishing a consistent endpoint of harm for radiation protection purposes is necessary for gauging and comparing the levels of protection afforded not only to all species but also to humans. As mentioned above, the proposed protection scheme must conform to the existing principles for radiation protection. In this vein, how does the proposed protection approach fit into the current framework? If it is meant to protect the individual species as inferred by the reference animals or plants, do we then create the fourth principal of protectionprotection of the individual biota? Currently, the Report does not do this, but rather begs for a substantial explanation.
3. It is unclear how the radiation sources and exposures from military or related activities are handled in the proposed protection system.
Examples from military or national defense activities, ranging from the atomic testing (i.e., radioactive fallout) conducted decades ago to recent warfare utilizing the likes of depleted uranium for missile projectiles or armor shields, should be provided. The Report is currently silent on these issues; it should state whether radiation sources from such activities are within the proposed system of protection or they are in fact excluded from consideration. If the latter, can the current concept of exclusion then apply to those sources (this is to say that such activities are not amenable to control)?
4. The Report should include emerging topics such as space exploration and related radiation protection issues.
With increased activities expected for manned space exploration, opportunities for exposures to elevated space radiation also will increase drastically (Section 5.7, regarding the introduction of new radiation sources). Such activities may also include space travel by civilians. These activities will pose significant challenges to radiation protection, as fundamental knowledge on radiation effects is still largely unknown, particularly for high-energy particles. The Report should explicitly address these issues and offer possible guidance to the extent possible.
1. There appear to be contradictory statements made in Section 2.4 regarding Exclusion and Exemption. Where Paragraph 41 states that “…detectability and detriment assumptions however are not sufficient reasons for excluding all exposures and all sources within the scope of regulatory control…,” Paragraph 42 then states that “…exemption from radiological protection regulatory requirements of situations unwarranted to be controlled because of the associated risk is negligible…” This latter statement confirms that there is a thing called “negligible risk,” a concept that has not been established in the Report. Yet again, in Paragraph 45, first bullet, it states, “the individual risk attributable…caused by an exempted practice…must be insignificant (… correspond to an annual dose of around 10 µSv ...).” The concept of “insignificant dose” and the level of 10 µSv for such a designation are far from being clear. Does it mean that the negligible dose and insignificant dose are the same and that they can be equated to 10 µSv per year? It is suggested that such an argument is best left to the three principles of radiation protection. Thus, rather than using a murky concept of “negligible risk” why not just say that at some point the ALARA process (i.e., by the second principle of optimization) would have reached an optimal level such that additional effort would not further enhance the benefits.
2. Prescribing an annual dose level of 10 µSv as the basis of exemption (pp. 1718, Paragraph 45) is largely unjustified. In the United States, for example, a number of currently exempted sources have in fact exhibited annual dose levels well exceeding 10 µSv (see NUREG-1717, Systematic Radiological Assessment of Exemptions for Source and Byproduct Materials, U.S. Nuclear Regulatory Commission, 2001). The suggested dose constraint may be more appropriate for clearance of materials but not for exempted materials in general. A more flexible approach, however, is proposed in Paragraph 46 where the statement appears to be more reasonable, “… National regulators should decide the criteria for exemption on a case-by-case basis and the dosimetric boundary of 10 µSv y-1 should be only one of the criteria used.” This latest statement makes the most sense and it should be emphasized first to avoid confusion.
3. One wonders how much of an improvement has been afforded by the new concept of “representative individual” over “critical group,” especially when the definition remains unclear (p. 47, Paragraph 176). Given the qualitative, abstract description, one suggestion is to opt for a more quantitative recommendation (such as a small fraction of the entire population), or at least provide some concrete examples to support the guidance.
4. Section 5.7, The Principle of Protection, raises a number of questions .
• Do the principles of protection apply to military activities? Regardless of the answer, the Report should at least cover this issue for completeness. Some of these activities, such as the fallouts from previous atomic tests, can become residual sources. In such a case wouldn’t the residual activities be considered as existing conditions and should be dealt with as such (discussed in Section 9.2)?
• How is the protection issues handled for space exploration? In this instance, the exposures are not “introduced” by the new man-made sources. Rather, they are made available by the new mechanisms (i.e., space flights) for accessing the space (including outer space) where intense natural radiation fields exist.
• P. 51, Paragraph 185, regarding the principle of limitation of maximum dose. What does the ICRP consider for this protection principle as it applies to the protection of the environment as described in Section 10? Does it mean that some maximum doses may be established for protecting individual biota, alongside of the limits for humans? That is, how can you reconcile the protection of the environment and that of humans in terms of the protection principles?
• P. 53, Section 5.8.1, regarding dose constraint. Increasingly, the regulatory trend is to build dose constraints into the regulations, and they have become de facto “dose limits” pertaining to compliance in the current regulations. It must be pointed out that the constraints are not intended to replace dose limits and, therefore, there are certain flexibilities involved in their prescribed levels, so long as the ALARA principle is followed.
5. In Section 5.8, (Optimization, it states that designation of dose constraints (Section 5.8.1) is part of the optimization process. It is unclear whether the selection of dose constraints would require further optimization.
6. The following comments pertain to Section 7, Exposure to Natural Sources.
• As mentioned above, the natural sources should not be limited to the earth-bound radioactive sources; exposure to cosmic radiations in space exploration should be included and fully addressed.
• It should be clarified whether the exposures to the natural sources constitute the exposure to the “existing situations” as mentioned in Section 9.2, and which the current protection does not address.
• P. 70, Paragraph 280, regarding exclusion and exemption for the natural radiation sources. Do the discussions in Section 5 for man-made sources also apply here? If not, what is the rationale?
• As mentioned above, how do you consider the protection issues regarding space exploration when exposures are to be related to natural sources?
• Paragraph No. 295, p. 73, last sentence. What is the basis for “…dose rate less than 1 µSv/h at a distance of 0.1 m (see Section 2.2).” However, Section 2.2 (The Structure of the System of Protection) contains no such information.
7. The following comments pertain to Section 8, Potential Exposures.
• The entire section on potential exposure is quite ambiguous regarding actual application. In the real world, one cannot gather all the possibilities about the potential exposures and capture the estimated risks. Perhaps it would be helpful to provide some guidance on what is “likely” versus what is “unlikely” (by means of probability) and deal with the issues on the level of dose (or risk) constraints.
• It is unclear whether the potential exposures include the affected population. It should be included, considering that the assessment is supposed to provide input to the optimization process (i.e., for the Second Protection Principle).
• In Paragraph No. 326, p. 79, it is unclear whether the postulated scenarios include both radiological dispersal devices (RDDs) and improvised nuclear devices (INDs), since the protective measures are not quite the same for the two different types of device.
• In Paragraph No. 328, p. 80, it should be made clear whether the workers involved in the emergency or related activities (raging from the responders to the long-term recovery) can all be categorized as radiation workers and be protected as such.
8. The following comments pertain to Section 10, Protection of the Environment. There are a number of issues, as discussed previously (see Overall Comments and General Comment No. 2). The following are specific comments pertaining to this section.
• Paragraph No. 352, p. 86. The biological diversity of the species requires a much more sophisticated approach to environmental protection than the one proposed in this section. There should be a better basis, one that parallels the discussions for humans presented in Sections 3 (Biological Aspects of Radiological Protection) to make sense of the entire protection framework.
• Paragraph No. 353, p. 86. The term “risk” to other species needs to be defined. Does it mean in the same realm as protection for humans? If not, what is it?
• Subsection 10.2 (Reference Animals and Plants). What is the objective for the reference animals and plants? It appears that the intent is to seek a dose quantity by which potential “risk” to species can be established. Does this mean there is a dose quantity that can be equated to the effective dose to humans? If so, please provide a technical basis.
9. The following are not found in the listed references (among several others) as cited by the Report:
• The scope of Radiological Protection Regulation (ICRP, 2006); cited on p. 18, Paragraph 47.
• Publication 101 (ICRP, 2006b); cited on p. 48, Paragraph 176.
10. The following typographical errors appear in the Report:
• Last line of p. 77, Paragraph 513, the word “s0ome” should be “some.”
• First paragraph, second line, p. 49. The comma behind the word “adult” should be a period.