|The following comments are not my own in particular but rather are the documented results of a meeting held in Ottawa Canada on August 10, 2006, with representation from Canadian nuclear industry, regulators, subject matter experts and other interested parties. They represent the consolidated views of 5 groups reviewing specific sections of the draft recommendations. A copy of this material has been separately provided to Dr. Jack Valentin.
Scope, Exclusion, and Exemption (Sections 2.3 and 2.4)
Exclusion and Exemption
• The flexibility with regards to the 10 µSv criterion (as a guide for exemption) should be better reflected in the recommendations, (see section 41 of the foundation document)
• In paragraph 47 (exemption criteria), the word criteria appears to imply levels. Clarification is required.
• The concept of clearance should be added to section 2 of the recommendations
• Section 2.4 should serve as a basis for the harmonization of the concepts of exclusion, exemption and clearance in international standards (e.g., consistency between RSG 1.7 and TSR 1)
• Clearance should be defined in the glossary
• The word response should be added after emergency in paragraphs 37 and 162 (see section 9.1) to differentiate between safety analysis and emergency response situations
• The absence of recommendations regarding protection of the environment should be highlighted in the scope
• The foundation document should acknowledge the need for clearance criteria for small quantities of contaminated liquids (other than authorized discharges)
The Principles of Justification (Section 5.7)
• Overall, section 5.7 is readable and understandable
• Issue of justification is more societal than science
• A scientific aspect does exist; yet, fundamental justification relies heavily on societal values
• Are there established criteria or systems to ensure that societal differences do not vary significantly?
– Societal values are often swayed by political venues
– Citizens of each country should be provided with a level of comfort that their safety is equitable to other nations
– We understand that these considerations are not ICRP driven, yet, who and how are these issues addressed ?
• Paragraph 168; opens the door to questionable practices; a clearer definition for the use of the word “screening” is required
– Mammography is a recognized screening procedure, while full body CT scans for screening purposes, are questionable practices; not medically prescribed or clinically justifiable
• Paragraph 169; last sentence in the paragraph needs to be re-worded for clarity
• Paragraph 186; Clarity is required with regards to dose limits not applying to existing situations
– ? What is meant be this statement
• Paragraph 187; Clarity is required with regards to the purpose of this paragraph
– ? Why is it there
• Paragraph 189; a forward reference to Section 9 Emergency Situations and Existing Situations is required
• Paragraph 191; Well stated, while in application at the national level, authorities need to ensure that justification is undertaken by qualified individuals
– Cumulative medical exposures require acknowledgement
– Paragraph 250 summarizes well these items
• A forward reference to Section 6 Medical Exposure of Patients, is required following paragraph 191
• In Section 6, paragraph 246 requires clarity and depth
– Knowledge of the ”principles of radiological protection” is not enough; appropriate practice and impacts must be understood and considered in the evaluation
– Historical exposures must be taken into account
• Paragraph 247 and 248, clarification is needed on who performs the justification and reviews. These must be performed by qualified persons, such as the individuals identified in paragraph 250.
• Paragraph 250 appropriately defines and clearly identifies the qualified persons (i.e. radiological practitioner and the referring physician)
• First sentence found in paragraph 262 should be moved up to be the first sentence in paragraph 260
- “It is important to ascertain whether a female patient is pregnant prior to any radiological procedure”
• Paragraph 269 (similar to paragraph 168) opens the door to questionable practices
• Section 6.5, difficult to understand and requires more clarity on the whole
• Paragraph 274; Is it possible for the Commission to provide explicit guidance on this interpretation?
• To understand this document, one needs to read from the beginning to the end
• This does not merge with current realities of word searches and executive summaries
Optimization of Protection (Section 5.8)
1. Lack of understandable definition of ‘constraint’ (is it a tool or a limit?). Examples may be helpful in the understanding. We see it as tool.
2. Introduction of constraints before the optimization process. We want to see a clear process for how the constraint is derived and how does it fit into the optimization process. Our view is that constraints are part of the optimization process but not the starting point.
Points for improvement
• The optimization process will differ greatly between that for occupational optimization and that for public/emergency situations. Recommendations currently do not specifically address this issue and they should for clarity.
• Our opinion is that optimization for emergency situations depends upon a robust emergency response program.
– We feel that the focus for optimization during an emergency situation, especially during the initial response, should not utilize dose constraints. (paragraph 192)
– Our concern is that optimization is too narrowly focused (i.e. intervention levels) in the recommendations currently (reference paragraph 348).
• Paragraph 348 implies that dose constraint is a dose limit which may lead to confusion. Recommendation that this paragraph be revised.
• Public perception is a determining factor in the optimization process. Societal factors greatly determine and influence optimization in emergency situations and planned situations (esp. with respect to public dose). Guidance on how to take account of public perception in the optimization process is required.
• Should be a clear definition of the difference between Canadian action levels and constraints.
• Clarification if the constraint has a role in the operational activities (if considered a prospective tool) paragraph 197.
• Collective dose integration into optimization process for the public domain? Is this a reasonable approach? We feel that there is a difficulty in use of collective dose as a primary factor for the optimization process/decision making when dealing with public domain. The use of BATNEEC will be more important.
• Agreement that in the operational domain collective dose can be used as a tool in the optimization process.
Constraints (Section 5.8.1 +)
• Rationale and Clarity
• Dose Constraints vs. Risk Constraints
• Definition of a Single Source
• Prospective vs. Retrospective
• Upper Bound for Optimization vs. Limiting Inequity
• Establishing Dose Constraints
• Exposure to one or multiple sources
Rationale and Clarity
• We recommend beginning the section on constraints with a clear definition and, in particular, adding a well-described rationale.
• We recommend moving most discussion of constraints to a single section, and minimizing substantial discussion in other sections.
Dose Constraints and Risk Constraints
We recommend that the descriptions of dose constraints and risk constraints in section 5.8 be separated.
Definition of a single source
• We recommend:
“Any physical entity or procedure that results in a potentially quantifiable radiation dose to a person or group of persons. It can be a physical source (e.g., a quantity of radioactive material or an x-ray machine), a facility (e.g., a hospital or nuclear power plant) or a class of operations or physical sources having similar characteristics (e.g., nuclear medicine procedures, background radiation).
Prospective vs retrospective
• We recommend that (197) and elsewhere be revised to more consistently state or clarify the retrospective use of dose constraints (eg. in some circumstances as action levels (reference (279)).
Upper Bound for Optimization vs. Limiting Inequity
• We recommend that links in (199) and elsewhere between constraints and equity be removed.
Establishing Dose Constraints
• We would recommend that this be revised to allow greater input from the operator. Dose constraints could be established by the regulator or the operator.
Exposure to one or multiple sources
• In (209), pertaining to a discussion of single source exposure and multiple source exposures:
– What is meant by additional restrictions are needed in the situation where one individual is exposed to several sources?
– By “restrictions”, does the ICRP mean “constraints”?
Exposure to Natural Sources (Section 7)
(279) These action levels are effectively constraints i.e., levels of aspiration often set by national authorities and not a mandatory level which must be achieved. In circumstances where doses exceed the value of constraints, optimised protective actions should be taken to reduce doses.
1. In Canadian terminology, this is a guideline. At some point this may become a regulation.
2. Constraints need to be acknowledged as generic and may differ by source and setting.
3. Definitions for ‘action level’ and ‘dose constraint’ and the relationship between them are needed.
(280) …Principles for exclusion and exemption of natural sources are that the individual risk from the source or practice is insignificant…
1. A natural source may be excluded because it is not amenable to control, but may still result in a significant dose. An exemption is an action or practice that is intentionally removed from control. Exclusion and exemption are not the same thing.
2. How is “insignificant” defined in the context of natural sources? It has to be treated differently than for man-related sources. For natural sources, insignificant might be within natural variation on a local or regional scale.
(282)…Industries producing NORMs include: extractive industries for energy production; use of phosphate rock; and mining and milling of mineral sands.
“Mineral sands” should be replaced with “rare earths and heavy minerals”.
(291)…Exposure to natural sources is the largest contributor to human exposure…
Exposures to natural sources are also unavoidable.
(294)…Examples of sources which should be excluded are cosmic rays at ground level, 40K in the human body and unmodified concentrations of naturally occurring radionuclides in most materials, except food stuffs, drinking water and animal feed, below 1000Bq/kg for the heads of uranium and thorium series and 10,000 Bq/kg for 40K…
This is confusing and needs to be clarified.
(296)…In the absence of other causes of death, absolute lung cancer risks by age 75 at usual radon concentrations of 0, 100, and 400 Bq/m3 would be about 0.4%, 0.5% and 0.7% respectively for lifelong non-smokers, and about 25 times greater (10%, 12% and 16%) for cigarette smokers…
These risk estimates are different than those developed by BEIR VI and for non-smokers, less conservative.
(297)…Given the wealth of data on domestic exposure to radon, the Commission now recommends that the estimation of risk from domestic radon exposure be based on the results of pooled residential case control radon studies…
Notwithstanding the recently available pooled studies, there is still great value in the miner epidemiology studies for investigating dose response relationships and confounding effects of smoking and exposure to other agents.
(301) Table 6: Constraints for Radon-222
According to para. 300, the title of this table should be ‘Action Levels for Radon-222’.
(303)…In such exposure situations, the Commission recommends that the constraint for radon exposure in the workplace should be set in terms of dose at a value that ensures compliance with the Commission’s occupational dose limits…
There is not universal agreement on the conversion of radon exposure to dose; however, the detriment from exposure to radon is well known from epidemiology. Therefore, it would be appropriate to use a summation formula with risk (detriment) equivalent denominators.
(304)…The problems posed by radon-220 (thoron) are much less widespread, and generally more tractable, than those posed by radon-222…
This is debatable. Based on recent discussions at UNSCEAR and published literature, possible issues with radon-220 (thoron) are more widespread than previously thought. This paragraph should be reworded.