EGIR Review of Draft ICRP Recommendation:
Radiological Protection in Geological Disposal of Long-Lived Solid Radioactive Waste
Introduction
The Expert Group on the Implications of Recommendations (EGIR) held its first meeting in September 2002. The Group was created by the CRPPH to perform assessments of draft ICRP general recommendations and to provide policy and implementational feedback to the document drafters with the aim of ensuring that the final recommendations addressed the views and concerns from CRPPH. Four separate EGIR meetings were held to assess various ICRP draft general recommendations documents, and the results of Committee’s activities with the ICRP regarding the new general recommendations (ICRP Publication 103) are documented in a CRPPH report titled: “The NEA Contribution to the Evolution of the International System of Radiological Protection” (NEA 2009).
This draft document assessment process is seen by the CRPPH as having been very successful in two key aspects. First, it has allowed the CRPPH to make its views and concerns clear to the ICRP on particular documents and subjects of interest. Second, it has helped the ICRP to clearly collect and address relevant views on its draft recommendations, such that final texts may be more broadly understood, accepted and used.
In 2008 the CRPPH agreed that the EGIR assessment process should also be applied to Rev. 1.0 of the new International Basic Safety Standards. This was the first “non-ICRP” document assessed using this approach, but again the results were very much appreciated by the CRPPH and by the IAEA who is principally responsible for the drafting of this internationally co-sponsored document[1].
Because of this positive experience, the CRPPH agreed at its 2009 meeting that the EGIR process is a powerful and useful assessment tool that could, in principle, be used to assess draft documents from many different organizations, providing, of course, that the CRPPH was interested in a particular document in development, and the drafting organisation was willing to provide draft material for assessment. As such, the CRPPH agreed that the EGIR should be thought of as a process “in standby”, to be implemented on an ad-hoc basis to assess specific draft documents identified by the CRPPH. Each such assessment will involve a new call for nominations to assure the participation of appropriate subject-matter experts.
The ICRP recommendation, Radiological Protection in Geological Disposal of Long-Lived Solid Radioactive Waste, was identified by the CRPPH as being a document of great interest. In addition, the NEA’s Radioactive Waste Management Committee (RWMC) expressed great interest in participating in the review of this document. As such, the call for nominations resulted in experts from both the CRPPH and the RWMC being named to the Expert Group for this EGIR review process. Annex 1 contains a list of the EGIR membership for the review of this document. Annex 2 contains a list of terms that the EGIR feels should be clearly defined as they are used in this ICRP recommendation. Annexes 3 and 4 contain a few comments sent by the United States and by France, respectively, to the EGIR after the meeting. While these comments have not been reviewed by the EGIR and as such does not represent EGIR consensus, they are included here because they represent the spirit of EGIR discussions.
As with other EGIR reviews, the process involved a word-by-word, line-by-line, page-by-page review of the document, noting questions, identifying areas needing clarification, and providing suggestions for changes to the text. Each question, clarification request and suggested change is accompanied by a clear rationale as to why the Expert Group feels the comment is necessary. As a result, the meeting produced a list of general comments, as well as an annotated version of the document including all comments and suggestions. The Expert Group’s final report will be sent directly to the ICRP, as well as to the full membership o the CRPPH and the RWMC for their information.
General Comments
As a result of its detailed review of the draft document, the Expert Group agreed on a series of general comments, in addition to the specific suggested changes. General comments are presented here, and specific comments are presented directly in an annotated version of the draft document shown in “track-change mode”.
Balance
The Expert Group felt that the document should correctly be focused on the most difficult aspect of this situation, that is, the application of radiological protection concepts for the far future. As such, while the EGIR appreciated the broad nature of the document, covering the waste disposal facility during planning, operation, closure and post-closure, it was recommended that the focus should be much more on the far future post-closure. For example, the EGIR felt that discussion of worker protection, which will be needed during facility operation and for surveillance afterwards, should be more clearly presented as not being of an issue for the far future.
Exposure Situations
References in the document to ICRP’s exposure situations for the far future should be clarified. The document should strongly reiterate that strict compliance with a dose or risk constraint is not recommended, particularly given the indicative nature of radiological assessments in the far future..
References to Time Periods
Associated with the above-reference to the document’s treatment of workers is a general comment that the document is somewhat inconsistent with its use of time periods. The text refers to time periods that are as long as possible, 10s of thousands of years, 100s of thousands of years, etc. The clear association of these reference periods with such things as concerns over workers, and with the protection aspects that are relevant would improve the document.
Justification
The EGIR was concerned by the document’s proposal for separate justification for different waste management options. This is inconsistent with ICRP’s current position that waste management and disposal are integral to a practice and are not free-standing practices that require their own justification. The EGIR also felt that if the practice which had generated the waste had ceased, then consideration of the protection strategy should be for the purpose of optimisation, not justification.
Design Basis
The recommendation presents the ICRP’s system of protection in terms of the type of oversight that is expected (e.g. direct during operation, indirect long after closure, and none in the far future), and in terms of disruptive events for the facility (e.g. design basis assessments, non-design basis evolution, and inadvertent human intrusion). Table 1 presents this information as a matrix, and assigns the ICRP’s exposure situations (e.g. planned, emergency, existing) to each of these matrix boxes. The EGIR felt that the design basis would account for low-probability events, and as such that non-design basis evolution events would be very low probability. As such, the EGIR did not feel that non-design basis evolution events could be considered to result in emergency exposure situations.
Scope
As mentioned above, the EGIR felt that the document should more clearly focused. As another example of this, the Expert Group suggested that the information in paragraphs 9 and 10 provides essential descriptions of what the document is intended to cover, and should be moved to the first paragraphs of the introduction.
At the same time, the focus of the document should be sharpened. For example, in paragraph 9 the document states that it covers “…all issues related to radiological protection of humans and the environment…”, but the following paragraph states that the report “…concerns exposures that may or may not occur in the far future.” The first statement seems to broadly include such things as worker dose during operation, while the second statement suggests that this is not the case. There are several examples of this type of confusion in the document, and although in this context the document is not fundamentally flawed, it could be much more clear.
Glossary
The Expert Group noted on several occasions that terminology used in the document is either somewhat inconsistent, or is unnecessarily different from international understanding (e.g. in IAEA and NEA document usage). To correct this, the EGIR recommends that a document glossary should be used. Annex 2 provides a list of terms whose definition in the context of this recommendation should be provided.
Stakeholders
The EGIR felt that the involvement of stakeholders in the development of waste disposal facilities is essential, and as such recommended that Chapter 3 should be thoroughly reviewed to assure that it states that stakeholders should be involved in all the phases until closure.
Title
The Expert Group felt that the title of the document should include the concept that the waste being disposed of is high level. It was suggested that the term “high-level” includes the concept of “long-lived”. As such, it was recommended to change the title to: Radiological Protection in Geological Disposal of High-Level Solid Radioactive Waste
Application
In referring to the various time periods of the disposal facility, and to the various time scales involved, the Expert Group suggested that the document should reference practical examples that could be consulted to add more context to the application aspects of high-level waste disposal. References to IAEA and/or NEA documents on this subject were thus recommended
Annex 1
EGIR Membership for the Review of
Radiological Protection in Geological Disposal of Long-Lived Solid Radioactive Waste
EGIR Members
Dr. László KOBLINGER (Chair)
Hungarian Atomic Energy Authority, Hungary
Mr. Arto ISOLANKILA
STUK, Finland
Dr. François BESNUS
IRSN, France
M. Jean-François LECOMTE
IRSN, France
Dr. Wolfgang WEISS
BfS, Germany
Chair of ICRP Task Group Drafting this Report
Marie Claire CANTONE
Universita' Degli Studi Di Milano, Italy
Mr. Hirokazu TACHIKAWA
Nuclear Safety Research Association, Japan
Dr. Pawel KRAJEWSKI
Central Laboratory for Radiological Protection, Poland
Mr. Synnöve BERGMAN
Vattenfall Research and Development AB, Sweden
Dr. Clive WILLIAMS
Environment Agency, United Kindgom
Mr. Timothy MCCARTIN
Nuclear Regulatory Commission, United States
NEA Secretariat
Dr. Ted LAZO (Secretariat)
Ms. Gloria KWONG
Mr. Keiichiro WAKASUGI
Ms. Ayano YOSHIDA
Annex 2
Suggested Terms to be defined in a Glossary:
Accident
Activity
Barrier
Best Available Technique
Biosphere
Closure
Committed effective dose
Committed equivalent dose
Confinement2
Containment2
Contamination
Countermeasures
Decommissioning
Design-basis evolution
Developer7
Detriment
Direct oversight
Disposal
Disposal facility8
Disposal system8
Disruptive event
Dose
Dose constraint
Dose limit
Effective dose
Emergency exposure situation
Environment
Equivalent dose
Existing exposure situation
Geological disposal
Geological disposal facility
Hazard5
Health effects
High level waste
Implementation of a disposal facility
Implementer7
Indirect oversight
Intake
Intervention
Isolation
Justification
License
Limit
Linear-non-threshold dose-effect relationship
Monitoring4
Multi-barrier, multi-function system
Natural disruptive event
Nominal risk coefficient
Non-design-basis evolution
Nuclear facility
Optimization
Oversight6
Planned exposure situations
Potential exposure
Protective actions
Public exposure
Radioactive waste
Reference Animals and Plants
Reference level
Reference Person
Regulatory authority
Remote monitoring4
Repository1
Representative Person
Resilience
Robustness
Retrievibility
Reversibility
Risk5
Risk assessment
Risk constraint
Safety analysis
Safety assessment
Safety case
Safety function
Surveillance
Stakeholder(s)
Storage
Waste characteristics
Waste management
Worker
Remarks to the glossary requests:
1: The term ‘repository’ is used exclusively in Fig. 1. (twice: in ‘repository closure’ and in ‘…human activity related to the repository’). Perhaps, it should be better to replace it with ‘disposal facility’ in the figure; and delete the term from the Glossary.
2: In the draft submitted by ICRP there is no ‘confinement’ mentioned, however, EGIR suggested to use it at several instances, instead of ‘containment’. If both are used, a clear distinction should be given.
3: Definitions of terms ‘safety analysis’, ‘safety assessment’ and ‘safety case’ should clearly indicate the differences.
4: Definitions of ‘monitoring’ and ‘remote monitoring’ should clearly show the difference.
5: Definitions of ‘hazard’ and ‘risk’ should clearly show the difference.
6: In definition of ‘oversight’ reference to ‘institutional control’ should be given.
7: Definitions of ‘developer’ and ‘implementer’ should clearly show the difference.
8: Definitions of ‘disposal facility’ and ‘disposal system’ should clearly show the difference.
Annex 3
Comments from the United States
Sent by Mr. Timothy McCartin, US NRC
In general your comments capture the results of the EGIR meeting. I have discussed the comments with the other U.S. agencies and we have two suggestions to add to the comments which I believe are consistent with the discussions at the meeting.
(1) Additional comment to be provided to ICRP:
As has been pointed out, terminology may not be consistently used in the document and the addition of a glossary should help out this problem. However, the document is not always consistent in explaining the some important concepts (e.g., design basis and oversight). The discussion of these elements, and the associated dose and risk constraints, appear in numerous places. To fully reconcile the discussion of these elements throughout the document requires, a priori, clear agreement on which version represents the correct interpretation. We strongly suggest that Table 1 is the appropriate place to consolidate this understanding; it claims to summarize all situations, is reiterated in the executive summary, and would serve as a natural anchor for the document. Once Table 1 and the accompanying explanatory text in Section 4.3.5 are agreed to accurately capture the key concepts for the document, it will be considerably simpler to review the remaining portions for consistency.
(2) Below are suggested revisions to Table 1 and Section 4.3.5 that I believe consolidate and clarify the meeting conclusions. We hope this will provide a useful platform for discussion. We have not developed more detailed comments on other portions of the document so far; as mentioned, we believe that reaching agreement on the concepts – and capturing them accurately in writing in a single place, to start-- is a prerequisite to reach a clear and consistent final document. I defer to your judgement if it is too ambitious to reach agreement in the EGIR prior to the immediate deadline, but regardless, I believe that the comment would be of value to submit to ICRP. We intend to submit the same comments as part of the US comments to ICRP.
4.3.5 Summary of relevant exposure situation according oversight
(60) The application of the three exposure situations and of dose limits, dose constraints and reference levels as defined in ICRP Publication 103 during these timeframes is indicated in Table 1. The table identifies the criteria that the ICRP recommends to be used for comparison during the pre-operational and operational phases. Interventions may be implemented during these periods, if necessary. Although the numerical criteria for existing and/or emergency situations may also be used during the periods of indirect and no oversight, this does not imply that intervention would be undertaken during the period of no oversight. The goal of geologic disposal is to avoid the need for human intervention.[tl1]
The design basis considers a range of incidents, accidents and disturbing events, and attempts to assure that these events are prevented if possible and/or consequences are mitigated.
(60) Table 1 provides the dose or risk criteria applicable during different time periods for a disposal facility corresponding to different levels of safety oversight. The period of direct oversight refers to the period of time when the facility is actively being monitored and personnel would be present to respond to accidents and emergencies – this is typically considered the operational period when waste is being received at the disposal facility and emplaced in disposal drifts, including some storage of waste as part of the disposal operations. Direct oversight would also be present during the pre-operational period if some radioactive waste was present for testing purposes and during decommissioning of waste handling facilities. Following permanent closure of the disposal facility it is anticipated that there would be some monitoring of the environment surrounding the disposal facility (period of indirect oversight) that would occur for a period of time. However, it cannot be assumed that such oversight would continue indefinitely and at some point in the future oversight would cease (period of no oversight). Thus, a high-level radioactive waste disposal facility is sited and designed to not rely on the presence of man to ensure safety.
Performance or safety analyses can be used to evaluate facility performance under specific conditions. The first column in Table 1 provides three specific categories of analyses (i.e., design basis evolution, non-design basis evolution, and inadvertent human intrusion) that are generally considered in geological disposal. “Design basis” analyses consider a range of credible or reasonably likely processes, accidents and disturbing events and attempts to assure that these events are prevented if possible and/or the consequences are mitigated. “Non-design basis” evolution involves very unlikely or implausible processes, accidents and disturbing events, potentially including extreme natural disruptive events. For such events, the probability of occurrence is so low that it may be neither relevant nor feasible to assess their impact on the disposal system. Therefore, it is not appropriate for the regulatory authority to apply dose or risk constraints to non-design basis evolution as a condition of licensing, and the regulatory authority may develop a strategy to limit their consideration or eliminate them from the analysis altogether. Non-design basis evolution may be evaluated in a general way as a “what if” situation, i.e., as a means to understand better the robustness of the site and design. Lastly, inadvertent human intrusion represents a “disturbing” event that typically is represented by a “stylized” or simplified analysis given the uncertainties associated with human behaviour in the distant future (note: inadvertent human intrusion is only considered relevant when oversight is no longer present at the site to prevent the intrusion).
The criteria presented in Table 1 cover both the operational period of a nuclear facility (direct oversight) and a period of time in the distant future (relative to a human lifetime) for the period of indirect and no oversight. For those exposures that occur during the period of direct oversight and are a result of credible incidents (design basis evolution) the exposure situation is to be considered a planned exposure situation that may result in normal exposures (primarily to workers) or potential exposures. Exposures should be compared to a dose constraint depending on the likelihood of the events considered; a risk constraint should be considered when less likely events are considered in the design basis analyses. Design basis analyses beyond the period of oversight (i.e., projected performance during periods of indirect and no oversight), should be considered to result in only potential exposures where a risk constraint of 1 × 10-5 per year is considered appropriate. Exposures outside the design basis -- i.e., non-design basis and inadvertent human intrusion -- represent extreme and very unlikely conditions where it is appropriate, at all timeframes, to use reference levels defined for emergency or existing exposure situations as comparative criteria. Application of numerical criteria to these situations should be viewed more as a qualitative exercise rather than a judgment of acceptability. However, all analyses must be mindful that the scientific basis for dose and risk assessments that project exposures situations into the distant future become more questionable the further out in time the analyses project and the strict application of any numerical criteria may be inappropriate.
[1] It should be noted that revisions 2.0, 3.0, 4.0 and 5.0 of the BSS were also reviewed by the EGIR in this fashion, resulting in many of the CRPPH concerns being addressed in the 2011 version of the BSS that was approved by the IAEA Board of Governors in September 2011.
[tl1]Be consistent with old line 333