|2006 Canadian Workshop on the Draft ICRP Recommendations
Results of the Workshop
On 2006 August 10, a national workshop was held to develop a Canadian position on the most recent draft ICRP Recommendations. Participants represented federal and provincial regulators, and a wide spectrum of the nuclear industry. It is fair to say that the results of this workshop, presented here, represent the viewpoint of a significant cross-section of Canadian RP professionals in both government and industry. A listing of all participants, and their affiliations, is presented at the end of this document.
The workshop was organized to respond to the five areas for which the ICRP specifically sought further guidance: Scope, Exclusion and Exemption; Justification; Optimization; Constraints; and Natural Sources. Plenary sessions were held at the beginning and end of the workshop, but most of the time was spent in breakout groups, each focusing on one of these five topical areas. As a result, the comments below are organized in this fashion, drawn from the presentations of each of these individual groups prepared as presentations in plenary. In addition, supplementary text on constraints is provided near the end of this document, which the breakout group on this subject prepared in addition to their summary comments.
List of Summary Comments by Breakout Group
Session #1. Scope, Exclusion, and Exemption (Sections 2.3 and 2.4)
Kevin Bundy (chair), Irvin Benovich, Steve Coupland, Dale Huffman, Martin Pierre, Jim Walker, David Whillans, Judy Ryan, Melanie Rickard (Technical Secretary)
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)
Session #2 The Principles of Justification (Section 5.7)
Bob Bradley (Chair), Lois Sowden-Plunkett, Doug Miller, Haidy Tadros (Technical Secretary)
• 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
Session # 3 Optimization of Protection (Section 5.8)
Stéphane Jean-Francoise (chair) Brian Bjorndal, Keith Dewar, Ray Lambert, Curt Nason, Richard Osborne, Eric Rabin, Len Rasmussen, John Takala, Caroline Purvis (Technical Secretary)
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.
Session #4 Constraints (Section 5.8.1 +)
Mike Grey (chair), Salah Djeffal, David Knight, Kevin LeNestour, Robin Manley, Robert Pollock, Jeff Sandeman, Jean-Pierre Gauvin, Amy Moore (Technical Secretary)
• 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”?
Session #5: Exposure to Natural Sources (Section 7)
Wayne Tiefenbach (Chair), Bliss Tracey, Douglas Chambers, Christina Dodkin (Technical Secretary)
(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.
Additional Commentary on Constraints
The treatment of dose and risk constraints in the current draft of the recommendations is an improvement over the previous version. However, several inconsistencies remain, and further clarity and refinement is required.
Rationale and Clarity
The need to raise the profile of constraints to “the most fundamental level of protection” (198) has not been well justified. Is there some gap in protection that this is trying to fill? Without a common understanding of the rationale it is difficult to follow the reasoning behind many recommendations related to constraints.
To improve clarity, the discussion of constraints should start with a clear definition of the term and an explanation of the reason for promoting its importance. We recommend beginning the section on constraints with a clear definition and, in particular, adding a well-described rationale.
Include a diagram within the recommendations that depicts “acceptable”, “tolerable” and “unacceptable”. Suggesting wording for such a definition follows: “A dose constraint is a level of dose above which it is unlikely that protection has been or is being optimized for a given source of exposure, and for which, therefore, action must almost always be taken. It defines a level above which doses may still be tolerable, but are unlikely to be acceptable. The action necessary if a dose constraint is exceeded would normally begin by determining whether protection has been optimized, and if it has not, should include taking steps to reduce doses to acceptable levels.” Some of this text hinges on other comments here relating to the retrospective use of constraints, and maintaining the fundamental link to optimization. Additional text would also be necessary to fully describe the rationale.
Although the “primary” sections on constraints are from (197) to (233), discussion of constraints appears throughout the document from paragraph (7) to (348), making it very difficult to comprehensively review and understand the concepts. We recommend moving most discussion of constraints to a single section, and minimizing substantial discussion in other sections.
Dose Constraints vs. Risk Constraints
The concepts of dose and risk are not interchangeable. We recommend that the descriptions of dose constraints and risk constraints in section 5.8 be separated.
Definition of a Single Source (Section 5.1, (160 and 161) with related paragraphs elsewhere (34, 200)
The definition of a source is not consistent within the document. We recommend that the definition be more specific such as “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
Used solely as a prospective tool (197), dose constraints have little value over and above the requirement to keep doses ALARA (i.e. to optimize protection). Indeed, the optimization process should result in doses below any reasonable dose constraints, and therefore if the optimization process is followed, dose constraints are redundant.
Conversely, as a retrospective tool, constraints can be operationally useful as “a level above which action to reduce doses must almost always be taken” (224). That is, exceeding a constraint during operations is a trigger to re-verify whether protection remains optimized and, if it is not, to take action to reduce doses. Canada has used a system like this successfully for several years, setting levels which, if exceeded, require a licensee to investigate, report, and take action to reduce dose if appropriate.
The internal conflict in last two sentences of (197) appears to hint at the idea that constraints do have a retrospective role to play: “[constraints] are not intended as a form of retrospective dose limitation, even if they are considered in the feedback process.”
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
Constraints are appropriately discussed within the section of the document on optimization (5.8) as they are “an upper bound … in optimization of protection” (glossary).
However, ICRP-60 and the current draft (199) also link dose constraints to the limitation of inequity in dose distribution (more fundamentally to inequity in risk distribution). However, limitation of maximum individual dose is the fundamental principle by which the system of protection seeks to ensure an adequate degree of equity in dose/risk distribution to members of the society, regardless of overall benefit to society. It is our view that individual dose limits are adequate to ensure reasonable dose equity, and therefore constraints are redundant for this purpose. Attempting to set values below individual dose limits for the purposes of risk equity is tenuous at best, given the large uncertainties in the dose-response relationship at these doses, and the substantial variations from individual to individual related to age, gender, and genetic dispositions.
In addition, trying to link constraints simultaneously to both optimization of protection and limitation of maximum individual dose adds unnecessary confusion.
We recommend that links in (199) and elsewhere between constraints and equity be removed.
Establishing Dose Constraints
In reference to (201) “It will usually be appropriate for dose constraints to be fixed at the national or local level taking account of the Commission’s guidance.”, and other similar paragraphs such as (210). 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”?
Christopher Clement, Canadian Nuclear Safety Commission (Workshop Chairperson)
Kevin Bundy, Canadian Nuclear Safety Commission (Breakout Group #1 Chairperson)
Robert Bradley, Health Canada (Breakout Group #2 Chairperson)
Stéphane Jean-François, Merck Frosst Canada (Breakout Group #3 Chairperson)
Mike Grey, Candesco (Breakout Group #4 Chairperson)
Wayne Tiefenbach, Saskatchewan Labour (Breakout Group #5 Chairperson)
Jack Valentin, International Commission on Radiological Protection (Observer)
Irvin Benovich, Ontario Power Generation
Brian Bjorndal, Radiation Safety Institute of Canada
Douglas Chambers, SENES Consultants Limited
Steve Coupland, Canadian Nuclear Association
Keith Dewar, Department of National Defence
Christina Dodkin, Canadian Nuclear Safety Commission
Salah Djeffal, Canadian Nuclear Safety Commission
Jean-Pierre Gauvin, Contex Environnement Inc.
Dale Huffman, Areva Resources Canada Inc.
Ramzi Jammal, Canadian Nuclear Safety Commission
David Knight, Department National Defence
Kevin LeNestour, Bruce Power
Robin Manley, Ontario Power Generation
Amy Moore, Canadian Nuclear Safety Commission
Doug Miller, Canadian Nuclear Safety Commission
Dr. Martin Pierre, Department National Defence
Curt Nason, New Brunswick Power Nuclear
Dr Richard V. Osborne, Ranasara Consultants Inc.
Robert Pollock, Areva Resources Canada Inc.
Caroline Purvis, Canadian Nuclear Safety Commission
Lois Sowden-Plunkett, University of Ottawa
Eric Rabin, Canadian Nuclear Safety Commission
Len Rasmussen, Atomic Energy of Canada Limited
Melanie Rickard, Canadian Nuclear Safety Commission
Judy Ryan, CANDU Owners Group Inc.
Jeff Sandeman, Canadian Nuclear Safety Commission
Haidy Tadros, Canadian Nuclear Safety Commission
John Takala, Cameco Corporation
Bliss Tracy, Health Canada
Jim Walker, Atomic Energy of Canada Limited
David Whillans, Ontario Power Generation