The Canadian Nuclear Safety Commission (CNSC) welcomes the ICRP’s intent to clarify its 1990 recommendations and to consolidate recommendations made since Publication 60. The CNSC’s comments focus mainly on the dose constraint and optimization concept and on safety culture. Other points consist mainly of requests for clarifications or more information.
In regards to the dose constraint and optimization concepts, there is apparent confusion between the applicability of dose constraints and dose limits. Although the Commission has clarified the applicability of the dose constraint concept in the past, such as in Publication 77, we would suggest that the Draft Recommendations present the concept in a concise, stand-alone manner so readers do not have to refer to past publications for clarification. The Draft Recommendations presents this concept in a manner that causes some confusion with the dose limitation system. In particular, discussions intermingle aspects of dose limits, optimization, dose constraints (sometimes presented as prospective design optimization targets) and ALARA. Given that the underlying principle and application of dose constraints is unclear as presented, it is recommended that the Draft Recommendations be revised where necessary to make a clear distinction between dose limits, optimization, dose constraints and the ALARA concept.
Furthermore, the recommendation that dose constraints should be established for all regulated activities is seen as an added regulatory and administrative burden on the regulator and licensees. In the end it is not clear what the value added to a properly operated and managed dose control and ALARA program would be. The concept would make regulatory control and applied radiation protection far more complicated.
Regarding safety culture, the role of operational management should be to foster a healthy safety culture – as opposed to simply a safety culture – within their respective organizations or to help move the existing safety culture in a positive direction. Moreover, while the draft presents safety culture as an important aspect of the optimization of protection, the concept should be presented such that the optimization of protection is an important component, and a consequence of a healthy safety culture.
Below are detailed comments expanding on the foregoing considerations as well as recommendations to clarify concepts and resolve apparent inconsistencies within the draft.
(S6): "This is because there is presumed to be some probability of DETRIMENTAL health effects even at small increments of exposure to radiation above the natural background." (Addition in ALL CAPS).
(S14) and (51): "The Commission is considering a new special name for radiation weighted dose so as to avoid the use of the name ‘sievert’ for both radiation weighted dose and effective dose." We strongly endorse this idea, and suggest the Commission adopt a new name in these recommendations rather than just state that a new name is being considered.
(S18): (editorial) 5th line: delete “the protection of”.
(21): To clearly understand the difference between “normal” and “emergency”, the situations/scenarios that require “urgent action” should be discussed in detail, and what constitutes an emergency should be clarified.
(50): "low-range" should be replaced by "weakly penetrating".
(71): Above equation 5, “secondary charged particles” should be replaced by “secondary heavy charged particles”. This change is suggested because the charged particles in question are high-LET, thus eliminating electrons. The above change would clarify the fact that electrons are excluded.
(75): The recommendation to consider mainly protons with energies above 10 MeV when choosing a value of wR requires further explanation, since skin dose is calculated at a depth of 0.007 cm.
(91): The phrase “ … corresponding to the annual dose limit for occupational exposure of 20 mSv” should be changed to “ … corresponding to 20 mSv”. In general there are references throughout the text to an annual dose limit of 20 mSv. The text should be revised to ensure consistency with the occupational effective dose limit, as stated in Publication 60 (50 mSv per year and 100 mSv in five years).
(94): The discussion in the paragraph suggests that “gray-equivalent” (Gy-Eq) is to be used only when deterministic effects are caused by irradiation. The paragraph should indicate, explicitly, under what circumstances the unit Gy-Eq applies and whether it applies only to tissue reactions.
(99): Table 5: The time intervals during which the doses are received, for each of the effects and thresholds in Table 5, should be discussed: information regarding the dose rate should be provided, if only as an indication of acute or chronic exposure.
(105): The document should define (quantitatively if possible) “acute dose”.
(113): (editorial) Table 6: For the whole population, the lethality adjusted cancer risk is given as 6.2 (1E-02 per Sv) and lethality adjusted hereditary effects as 0.2 . The total, however, is given as 6.5.
(118): The meaning of the last sentence is unclear. The paragraph should discuss what is meant by “a specific protection case in common prolonged exposure situations”.
(139): Figure 2, “The Public is Protected”, shows a picture demonstrating the dose limits, one of the pictures is entitled “radiology”. To avoid potential confusion, suggest the insertion of text in the title explaining that members of the public exclude patients under medical care/supervision.
(145): 5.3.2: Because one does not know the total dose to individuals, dose constraints would apply instead of the public dose limit in the case of public exposures. It is not clear then why the public dose limit in ICRP-60 should still be recommended. This would benefit from some clarification.
(153): The definition of Safety Culture referred to in this paragraph comes from Safety Series 75 of INSAG-4 (the International Nuclear Safety Advisory Group) and is dated 1991. It does not come from “Basic Safety Standards, FAO, 1996”. The correct root citing needs to be provided here. A more up-to-date definition of Safety Culture needs to be inserted as well.
(159): Although it implies a dose limit for emergency, non-life threatening, of 100 mSv/yr, the text only indicates a dose limit of 100 mSv. This is reiterated or clarified in the next paragraph, 164, point 1 that states ".. the constraint of 100 mSv dose, either acute or in a year". The text in Paragraph 159 should be clarified to be consistent with other parts of the document that directly state "in a year" or "mSv/yr".
(160): “Exposures that are within the natural background range are legitimate matters for concern, sometimes calling for significant action”. Exposures that are within natural background range are not always legitimate matters for concern, they “may be legitimate matters for concern”. Revise text accordingly.
(162): It is not evident that the Commission’s recommended constraints are consistent with current dose limits. Comparing constraints with the dose limits seems to indicate that “the part is greater than the sum of parts”. This confusion is understandable in view of the earlier comment on paragraph (134).
(162): (editorial) It should be noted there are not four, but three maximum dose constraint values recommended for workers and the public: 100, 20 and 1 mSv/a. The minimum recommended constraint is 0.01 mSv/a.
(164): 1st bullet: What constitutes an emergency other than a situation that puts a life in jeopardy, or causes serious injury or catastrophic circumstances?
(165): Table 7 (1mSv/y): “no information” is inconsistent with “general information”, and “no individual assessment for the exposed individuals” is inconsistent with “or monitoring” in (164), 3rd bullet.
(166): “to avoid unnecessary imbalance between the exposed individuals and the controllability of the source” requires explanation.
(178): (editorial) Paragraph (146) discusses medical exposures not radon-222.
(188): The last sentence describes in part…“This procedure…..broader than just considering the doses so as to assure safety culture…”. This is an improper use of the phrase. Culture drives the other behaviors in the organization. One performance criterion of a healthy safety culture demonstrates that doses are as low as reasonably achievable. This example meets the characteristic that safety culture is integrated into all activities of the organization.
(204): Given that one radionuclide in RS-G-1.7 is associated with an exclusion level of 0.01 Bq/g, i.e., I-129, while some exclusion levels in the same document exceed the values listed in Table 10 by a few orders of magnitude, e.g., P-32 and P-33: 1,000 Bq/g; Tc-99m and I-125: 100 Bq/g, the recommended exclusion levels shown in Table 10 would be more appropriate to be used as screening values, or as default values when no other value was available.
(215): Last sentence: References for the “recent cases of radiation injury to patients” should be cited.
(A11): Last sentence: To what does “SEER” refer?
(A36): The 2nd sentence requires clarification. Examples of the evidence for excess risk (numerical) in the aggregate and the uncertainties (numerical) in the degree of risk for single tissues should be provided.
(A37): Table A1 – “Relative cancer free life lost” should be defined. Footnote *: The relationship between “q” and “qT” in (A30) should be explained.