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Submitted by Christina Dodkin, Canadian Nuclear Safety Commission
   Commenting on behalf of the organisation
Document Radiological Protection in Geological Disposal of Long-lived Solid Radioactive Waste
 

Canadian Nuclear Safety Commission (CNSC) Review of Draft ICRP Report, Radiological Protection in Geological Disposal of Long-Lived Solid Radioactive Waste


4 November 2011


 


 


 



  • Paragraphs 129 – 132:   The preface states that the report covers both the protection of humans (workers and the public) and the environment; however, in Annex I, paragraphs 1574 – 1582, the Commission states that it does not propose to set any form of dose limits with respect to environmental protection, since the Commission continues to develop this framework.  It is expected that once the framework is developed, more comprehensive advice on environmental protection and dose limits would be provided in the future.  This should be stated in the preface.


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  • Paragraphs 181, 182:  Suggest including “a combination of engineered barriers” as part of this thought (e.g., “…any release would be slowed down by and diluted further by a combination of engineered barriers and properly chosen geological formation.”).


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  • Paragraph 219:  Typographical error:  “1 10-5” requires proper notation (i.e. 1 x 10-5).


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  • Paragraph 221:  Grammatical error.  “Loses” as opposed to “looses”.


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  • Paragraphs 295, 296:  Suggest replacing “permanent” with “long term”, and adding “without the intention of retrieval” (e.g., Waste disposal is the long term isolation and containment of waste in an appropriate facility without the intention of retrieval.).


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  • Paragraphs 319, 321:  Suggest replacing “that are comparable with” with “within which”, and adding “might occur” at the end of the sentence (e.g., The goal of a geological disposal facility is to achieve the isolation and containment of the waste and to protect humans and the environment for time scales within which geological changes might occur.).


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  • Paragraphs 321, 322:  Suggest adding “the effects of” and replacing “are particularly slow” with “could be dampened” (e.g., “At great distance from the surface, the effects of such changes could be dampened…).


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  • Paragraphs 331 – 333:  Suggest replacing “in-built” with “built-in”, and “the presence of man” with “human intervention” (e.g., “The disposal facility is thus to be seen as a functional facility whose controls are built-in and whose safety, after facility closure, does not rely on human intervention.”).


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  • Paragraphs 333, 334:  Suggest replacing “independent of man” with “without human intervention” (e.g., “The safety function to be fulfilled by a geological disposal facility without human intervention…”).


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  • Paragraphs 408 – 438, “Scope of this Report”:  General Comment:  This discussion seems a little bit outside of the scope and the expertise of the ICRP.  For instance, what about uranium mine tailings?  Reference to IAEA Safety Standards (e.g. Safety Requirements No. WS-R4, Geological Disposal of Radioactive Waste; Draft Specific Safety Requirements No. SSR-5/DS354, Disposal of Radioactive Waste; Draft Safety Guide No. DS355, The Safety Case and Assessment for Radioactive Waste Disposal) where methods of disposal and methods for developing their safety cases are discussed in detail would be appropriate.


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  • Paragraph 428:  Replace “presence of man” with “presence of humans”.


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  • Paragraph 456:  Suggest removing “the” before “society” from this sentence (e.g., “…it is not possible to envisage how society will be organized in the far future while…).


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  • Paragraph 573:  Replace “presence of man” with “presence of humans”.


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  • Paragraph 584:  Replace “man-made” with “human-made”.


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  • Paragraph 635:  Suggest replacing “does” with “should not” (e.g., “The loss of oversight should not result...”).


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  • Paragraph 675:  The Operator is responsible for managing the protection of workers, the public and the environment; not the regulator.  Suggest removing the word "both" before “the operator” in this sentence.


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  • Paragraph 690:  Suggest adding “some” before “forms” (e.g., (34) It is to be expected that regulators and society will maintain some forms…).


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  • Paragraph 691:  Grammatical error; “their” instead of “there”.


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  • Paragraphs 875 – 885: General Comment:  The role of the safety assessment within the safety case is discussed in more detail in several IAEA and NEA publications.  These should be referenced to. Safety assessment results are not predictions. Safety assessment is one component of the multiple lines of evidence that constitute the safety case.


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  • Paragraphs 921 – 924:  General Comment:  The CNSC, following the IAEA’s requirements and guidance (e.g. Safety Requirements No. WS-R4, Geological Disposal of Radioactive Waste; Draft Specific Safety Requirements No. SSR-5/DS354, Disposal of Radioactive Waste; Draft Safety Guide No. DS355, The Safety Case and Assessment for Radioactive Waste Disposal) also recommends the consideration of natural disruptive events in the normal evolution scenario (equivalent to the design-basis scenario in the ICRP draft report) in CNSC Regulatory Guide G-320, Assessing the Long Term Safety of Radioactive Waste Management. What events are to be included depends on their annual probability of occurrence, and the time frame for the assessment, and are judged on a case-by-case basis by discussion between CNSC staff and the proponents. It might be useful that the ICRP recommends here a quantitative value of cutoff probabilities for events that should be included in the design basis scenario.


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  • Paragraphs 976 – 987:  General Comment:  In this clause, the ICRP does not recommend using risk for inadvertent intrusion scenarios, because calculation of the probability of intrusion for very long times is deemed uncertain and unreliable. However, the same argument could be provided for performing safety assessments overall. The IAEA (i.e. Draft Safety Guide No. DS355, The Safety Case and Assessment for Radioactive Waste Disposal) seems to also adopt the ICRP recommendation. However, CNSC staff believes that calculating risk associated with inadvertent human intrusion could be useful (e.g. CNSC Regulatory Guide G-320, Assessing the Long Term Safety of Radioactive Waste Management, section 7.5.2). For example, intrusion into deep geological repositories is often associated with drilling activities. The probability of drilling activities could be estimated with some confidence, based on past drilling activity records combined with the knowledge on potential natural resources at the site and in the surrounding region.


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  • Paragraph 1032:  Replace “man” with “human”.


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  • Paragraphs 1165 – 1166:  It is stated in this report that the assessment of robustness can contribute to system optimisation. However, the following statement is not clear: “The indicative nature of calculated effective dose and risk in the very far future reduces their usefulness for the optimisation process.” Robustness of the disposal system is usually evaluated through comparison of the results of analyses of the design-basis scenario with those associated with specific perturbations. The most generally considered perturbations are those where one component or one of its characteristics is assumed to fail (‘what-if’ scenarios). The comparison between the design basis scenario and the what-if scenarios requires quantitative comparison indicators.  If dose and risk are deemed to be of limited usefulness, the document should provide suggestions for alternative indicators.


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  • Paragraph 1190:  Grammatical error; “discrete” instead of “discreet”.


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  • Paragraph 1871:  Replace “man-made” with “human-made”.

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