Radiological Protection in Geological Disposal of Long-lived Solid Radioactive Waste

Draft document: Radiological Protection in Geological Disposal of Long-lived Solid Radioactive Waste
Submitted by Roger Yearsley, Environment Agency of England and Wales
Commenting on behalf of the organisation

Comments from the Environment Agency of England and Wales





The Environment Agency is responsible in England and Wales for regulating disposals of radioactive waste from nuclear licensed sites and other premises using radioactive substances.  Disposals of radioactive waste include discharges into the atmosphere, surface waters and groundwater, disposals by transfer to another site and disposal to land.  The Environment Agency together with the UK’s Office for Nuclear Regulation, which regulates nuclear safety, will be the joint regulators of any geological disposal facility developed in England and Wales. 


Our comments below focus on areas of the ICRP document which we consider as unsatisfactory and need to be reconsidered. These include:

-  Application of ICRP’s exposure situations;

-  Risk Constraint and Risk Limit;

-  ‘Design Basis’ Concept;

-  Justification;

-  Optimisation; and

-  Role of the Regulator.

We also note some points of clarification.






Application of ICRP’s exposure situations


Line 279 and tables on page 8 and page 27: A geological repository will be receiving wastes for many decades, before being under institutional controls for a prolonged period, perhaps hundreds of years.  The radiological “exposure situations” defined in ICRP’s radiological protection system, which is designed for current radiation exposures, are being forced to fit periods in the long term future for which they were not intended and for which they are unsuitable.  Decisions that are made in respect of siting, construction, waste acceptance, operational management and closure of a waste repository govern the long term radiation risks.  ICRP should make it clear that the “exposure situations” are those which are considered when these decisions are being made and do not apply to the long term future, after a decision has been taken to release a site from institutional control. Conventional radiation protection measures would not then apply.  Thus, the tables on pages 8 and 27 should be deleted or should refer only to the period of direct control, when the ICRP’s exposure situations are relevant.   


The assumption that a ‘design-basis evolution’ will result in a planned exposure situation during the period of no oversight could be taken to mean that there may some form of continuing control beyond that provided by the engineered barriers and the host rock.  It might also be taken to imply that there is sufficient understanding of a largely natural system to predict a specific outcome in the far future – which would be unrealistic.  The suggestion that ‘non-design basis evolution” is to be considered an ‘emergency situation’ might suggest to some stakeholders that a geological disposal facility might result in major, uncontrolled contamination in the long-term future.      


Risk Constraint and Risk Limit


Lines 196-198 and subsequent lines; lines 1720-1725; tables on page 8 and page 27: For geological disposal, we consider it is inappropriate to refer to “dose constraints” and “risk constraints” during the periods of indirect oversight and no oversight.  Risk, in particular, cannot be measured and can only be estimated by an indirect process that involves an extrapolation from the past into the future.  Following from ICRP’s own view that estimations of dose or risk can only provide an indication or illustration of the robustness of a system (see lines 1089-1093), a constraint or a limit on their estimated values cannot have any force or meaning in terms of regulatory compliance. ICRP should make clear that the risk constraint and the risk limit identified for the post-closure period are only for comparative purposes, as an aid to judging long-term safety, and are not intended for regulatory compliance.  The UK environment agencies therefore specify a “risk guidance level” in our regulatory guidance on solid radioactive waste disposal.


‘Design Basis’ Concept


Lines 189-192, 242-250 and 257-259; tables on page 8 and page 27: While we recognise the value of the ‘design basis’ concept for a nuclear facility, such as a nuclear power station, which is under operator control and regulatory supervision, it is inappropriate to apply this to a geological disposal system for the period in the longer term after closure.  The performance of the system at that stage will depend substantially on its natural parts, e.g. the surrounding geology, which are not ‘designed’, and human control over the system is very limited.  The suggestion that the ‘design basis’ concept can be extended to become a ‘design basis evolution’ also seems to imply either a very high level of understanding of the future evolution of the system, or that full control over the system can be maintained in the long term.


We agree with the statement at lines 1089-1093 that: ‘assessment of post-closure radiological impacts through the estimation of effective dose or risk to a reference person, given the increasing uncertainties with time and the cautious assumptions to be made, can only provide an indication or illustration of the robustness of the system, rather than predictions of future radiological consequences.’   It follows that references to a ‘design basis’ concept should be applied only to the period of operator control and regulatory supervision up to, and including, closure. 



We do not agree with the proposal for separate justification for different waste management options.  It 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.  We consider the draft should be amended in the following respects:


Lines 412-416:  The text ‘decisions involving’ should be deleted.  It is justification of the practice that is required, not justification of decisions. 


Lines 748-756, and similarly in Lines 1372-1378:  The fourth sentence (“This assessment should include considerations of different options for waste management and disposal including the justification of these options”) should be deleted.  It is additional text to para 34, ICRP 77 and suggests that separate justification is required for different waste management options.  This is inconsistent with the position set out in the first sentence that waste management and disposal are integral to a practice and also with the second sentence which makes clear that waste management and disposal are not free-standing practices that require their own justification.


Lines 758-759, and similarly in Lines 1380-1381:  We would question whether this final sentence is a correct interpretation of ICRP77 in the ICRP103 framework, and specifically whether the term “protection strategy” is an appropriate replacement for “intervention”.  ICRP77 states that, if national waste disposal policy has changed and the practice (that produced the waste) has ceased, intervention has to be considered for justification.  In this case there are unlikely to be any benefits to be weighed (since they would have been associated with the practice that produced the waste) and so the test of whether the waste management practice should be changed is whether such a change would do more good than harm.




Lines 208-209 and Lines 1082-1084: ICRP’s draft text suggests that oversight of a geological radioactive waste facility needs to be maintained indefinitely to achieve optimisation of protection.  This is inconsistent with the basis of geological disposal where, eventually, and provided there is sufficient confidence in the disposal system, it is planned that institutional controls will be relaxed. 


Lines 638-639:  The text suggests that optimisation requires retention of a capability to update the safety case for an extensive period following closure.  We consider this to be impracticable, as it is not possible to guarantee that such a capability would be available after an operator and site is released from regulatory control.


Lines 916-920:  ‘Optimizing site selection’ suggests a need to identify the best site, which is impractical.  We suggest redrafting to read, ‘… selecting a site with characteristics that minimize …’.   


Lines 1061-1063: Optimisation will be a continuous process that must reflect the circumstances prevailing at a particular time and defining milestones might be misleading on what might be achieved by a certain time. Also, regulators’ and stakeholders’ views might inform the approach to optimisation but responsibility for optimisation must lie with the developer/implementer.     


Lines 1112-1119:  This seems to be suggesting the application of Best Available Techniques (BAT) to the site selection process.  We do not consider that it wise to try to apply the concept of BAT, in a regulatory sense, to the site selection process for a geological repository – since site selection may need to take account of the concerns of local and national stakeholders, and these will be beyond a BAT assessment.  BAT is more likely to be applicable to the methods and techniques used for data gathering and interpretation within a site characterisation programme.  In this case, it might be possible to identify BAT from experience and use of such methods and techniques in other radioactive waste disposal programmes, or in other industries such as hydrocarbon exploration. 


Role of the Regulator


The ICRP document suggests roles for the regulator that are inconsistent with our roles defined under our UK national legislation.  For example, the document suggests that the regulator will have responsibility for a geological disposal facility after an operator has been released from regulatory control.   The ongoing role of a regulatory body will be a matter for a future government and it would not be appropriate to specify what that role (if any) should be.  ICRP should reconsider the following aspects:


Lines 188-192:  The meaning of the first sentence is unclear and the paragraph suggests a role for regulation/the regulator that may not be appropriate in all national situations - regulatory approaches vary between countries and the text is rather prescriptive.   Also see previous comments about ‘design basis’.


Lines 675-678:  The operator is responsible for active management of the protection of workers, the public and the environment.  The regulator’s role is, in general, to ensure that the operator meets the required standards of protection. 


Lines 690-692:  This statement seems to assume that the regulators will have responsibility for a facility after an operator has been released from regulatory supervision.  This is inconsistent with current regulatory practice and it would be a major change in regulatory role if a regulator had to assume responsibilities for a facility after an operator was released from a permit or licence.  After the end of regulatory supervision, maintaining memory of the facility should become a societal responsibility, possibly discharged through national or local government.


Lines 910-920: The role suggested for the regulator may not be appropriate in all national situations: regulatory approaches vary between countries and the text is rather prescriptive.  The developer/implementer is responsible for developing the safety case for a geological disposal facility and should take responsibility for developing a strategy to assess very low probability events.  When developing such a strategy, the developer/implementer should involve the regulators and other stakeholders.


Lines 1046-1051:  This is potentially confusing. Optimisation should primarily be the responsibility of the developer/implementer.  In particular, the regulators are not responsible for optimisation.  The developer/implementer should engage in dialogue with regulators and stakeholders on its approach to optimisation.  Stakeholders’ views may effectively constrain what the developer can do by way of optimisation, but the involvement of stakeholders does not lessen the developer’s responsibility.


Lines 1412-1418:  Again, optimisation is the responsibility of the developer/implementer, not a matter for regulators.  Regulators will review the developer/implementer’s approach as part of the overall process of assessing the safety case for a facility.  Regulatory views on the approach to optimisation might inform a developer/implementer’s thinking.  Instead of ‘operating management’ the text should refer to the developer/implementer, because optimisation should start from the outset of the programme to develop a facility.



Points of clarification



Figure 1, page 15: The red line representing the amount of human activity should end at start of the period of no oversight.  Use of a dotted line might be taken to imply some continuing form of oversight.


Line 205:  Should refer to ‘Best Available Techniques’.


Lines 211-214:  Safety case does not need to be in inverted commas. It is also not clear what ‘compatible with regulation’ means in this context – should this say ‘are within radiological protection criteria specified as part of the regulatory requirements.’


Lines 250-255:  It is unclear what ‘there is a need to evaluate the consequences within the scope of an existing exposure situation’ means in this context and who should undertake such an evaluation.  Is this ‘need’ placing an implied requirement on the developer/implementer to explore the consequences of such events in the safety case, or on some unidentified person or organisation in the far future to evaluate the consequences of an actual event?


Lines 266-268:  Nothing happens ‘automatically’ in establishing the safety case:  the developer/implementer has to make it happen.  Also, what is meant by ‘high certainty’?  Something is either certain or it is not.  Should this text say ‘by including events of low probability, includes consideration of’?


Lines 330-331:  ‘(5) The safety strategy implemented for geological disposal is that to concentrate and retain the waste.’  Delete the word ‘that’.


Lines 563-569:  The draft text states: ‘The “concentrate and contain” strategy makes it possible, in principle, for the waste to be re-accessed either voluntarily or involuntarily at some time in the future. Therefore, disposal systems ought to be designed to reduce the possibility of inadvertent or malevolent events. There are to some extent conflicting requirements involved and a balance has to be found in each case, taking into consideration the timescales, the nature of the waste, the nature of the host geological formation, and the evolving desires of society.’   The second sentence includes reference to ‘malevolent’ intrusion, which would suggest knowledge of the disposal facility and its contents, and would therefore be a form of intentional intrusion. The sentence should refer only to inadvertent human intrusion.  The disposal system cannot be designed to avoid intentional intrusion.


Lines 602-603:  This text should be changed to, ‘the long-term safety case should be regularly updated by the developer/implementer and reviewed by the regulator.’.


Lines 616-626:   What does ‘some remote monitoring’ mean?  Does it imply remote monitoring systems installed underground and if so, how will these provide reliable information without maintenance or at worst, compromising the long-term performance of the disposal system?   Also, it is not clear how safeguards controls will continue to apply in the period of indirect oversight – there will be no possibility of inspection and verification in a closed facility and remote methods might present similar problems to remote monitoring.


Lines 627-630:  ‘Although termination of indirect oversight is not foreseen’ suggests that indirect oversight will continue indefinitely. The intended meaning seems to be that it is not possible to foresee the point at which indirect oversight might terminate.


Lines 700-711:  This paragraph is difficult to understand.  It might be reworded as: 

 ‘One type of passive control that might continue after direct oversight has ceased is the preservation of memory or records of the presence of a geological disposal facility. Other measures, such as restrictions on land use, decided by the authorities in interaction with the different stakeholders might also apply; these might, however, be for a much shorter period.  Measures to preserve the memory of a facility might help reduce the probability of inadvertent human intrusion and may assist the justification and planning of any deliberate intrusion should this be required in the future. At some point in the distant future, the memory of the presence of the disposal facility may be lost.  Long term defence against inadvertent human intrusion will rely largely on locating the facility deep underground, isolated from the environment that people normally inhabit and in a geological environment with no exploitable resources. The location of the geological disposal facility and its technical design will constitute the remaining built-in “control” against inadvertent intrusion.’ 


Lines 717-719:  The meaning of this text is unclear - is it suggesting that indirect control might start after an operator has been released from regulatory control?  Suggest deleting.


Lines 864-865:  Delete “traditional”, insert “established”.


Lines 951-952:  ‘In general, waste is disposed in a geological disposal facility if it needs to be isolated from possible human intrusion (IAEA, 2009).’   Although an IAEA reference is given, this statement is questionable.  Waste is disposed of in a geological disposal facility for the purposes of isolation (one aspect of which is avoidance of human intrusion) and containment.  This is said in lines 1086-1088:  ‘(71) Geological disposal facilities are sited, designed and implemented to provide for robust long-time isolation and containment, resulting in potential impacts on humans and the environment only in the very far future.’


Lines 1033-1037:  This reads as though safety has to be ensured during the operational period by a passively functioning disposal system.  Suggest rewording to ‘… including during the period of no oversight. In the long term and particularly, in the latter period, safety has to be ...’.


Lines 1053-1059:  The last sentence expresses a useful warning - but without defining what might be seen as questionable, it is open to wide interpretation.  The important point is made in the preceding sentence regarding an understanding of safety implications.  


Lines 1097-1104:  This text could be interpreted as having too narrow a focus on the design of engineered components and ignoring important components of the system such as the layout of a facility and the timing of various activities during the operational period.  It would be helpful to explain what is meant by ‘components of the facility’ (natural and engineered components); ‘quality of system components’ (engineered components only?); ‘elements of BAT’ (which elements and applied to what?); and ‘These elements complement’ (elements of BAT or the wider group of factors in the preceding sentence?). 


Lines 1158-1161:  The text refers to “The assessment of the robustness of the disposal facility”, and there are other references to “robustness” and “robust” elsewhere in the document (e.g. lines 1086-1088).  These terms should be defined.   We also think that the text should refer to ‘disposal system’ rather than ‘disposal facility’, since optimisation of protection is concerned with the disposal system as whole.


Lines 1635-1639:  The text should be amended to read ‘… important component of optimisation of protection in waste disposal projects.’.




Environment Agency

October 2011