Nuclear Decommissioning Authority
Radioactive Waste Management Directorate
Response to ICRP consultation 'Radiological Protection in Geological Disposal of Long-Lived Solid Radioactive Waste'
The UK Government’s Managing Radioactive Waste Safely (MRWS) programme provides a framework for the management of higher activity radioactive waste in the long term through geological disposal, coupled with safe and secure interim storage and ongoing research and development to support its optimised implementation.
The Nuclear Decommissioning Authority (NDA) has responsibility for planning and implementing geological disposal in the UK as the implementing body, and has set up a Radioactive Waste Management Directorate (RWMD) which it intends to develop into an effective ‘delivery organisation’ to implement geological disposal. It is envisaged that RWMD will become a wholly owned subsidiary company of NDA. At the appropriate time, the delivery organisation will become the site licence company (SLC) responsible for the development of the geological disposal facility.
This document sets out NDA RWMD’s response to the International Commission on Radiological Protection (ICRP)’s consultation on ‘Radiological Protection in Geological Disposal of Long-Lived Solid Radioactive Waste’ .
Making a comparison with paragraph (34) of ICRP Publication 77 , the ‘Justification’ statement in the first bullet of paragraph (40) appears to have been changed to reflect changes introduced in ICRP 103 , i.e.:
Previous text – “If the practice has ceased, it is intervention rather than the practice that has to be considered for justification.”
Proposed text – “If the practice has ceased, the protection strategy, rather than the practice, has to be considered for justification.”
However, as the protection strategy forms part of optimisation, it would be optimisation that should be reconsidered rather than justification. It is therefore questionable whether this approach represents an appropriate and accurate reflection of the ICRP 103 changes.
The first bullet of paragraph (40) includes the statement “This assessment should include considerations of different options for waste management and disposal including the justification of these options”. This statement adds to the existing requirement for the assessment of the justification of a practice to include waste management and disposal operations but, significantly, replaces “operations” with “options” and closes with a new specific requirement for the assessment to include the justification of these options. It would be helpful to have clarity on what would be expected regarding justification of different options for waste management and disposal.
This new requirement for the consideration of waste management and disposal options in the assessment supporting the justification of a practice would not seem unreasonable in principle, but the potential implications need to be considered. The statement “including the justification of these options” requires clarification given the use of the word “justification” in this context. If this is meant to say ‘demonstrate that suitable options have been considered’ then that would seem appropriate, but any proposed requirement to carry out justification of geological disposal as a stand-alone practice would not fit well with the initial sentences of the first bullet of paragraph (40).
The proposed changes to the text on justification are a little unclear, introducing an element of uncertainty between the optimisation and justification processes. It is considered that the adoption of these changes could be problematic and may not be helpful.
2 Severe natural disruptive events
It appears that severe natural disruptive events are proposed not to be included in the design basis. Instead it appears they are to be considered against reference levels that are higher than the dose or risk constraints that would otherwise be used. It is unclear how these potential severe natural disruptive events are proposed to be taken into account at the design stage, prior to waste emplacement, e.g. what would be the appropriate course of action if the reference levels were assessed to be exceeded at the design stage?
From the example given of major landform change due to tectonic events, there appears to be some confusion between the probability of severity of disruption and the timescales on which such disruption might occur. In the case of the example given, the timescales for occurrence are of the order of millions of years into the future, but the occurrence is predictable in general terms. Therefore the recommendations may need to be rephrased to provide sufficient guidance to the implementer and regulator. The proposition at the end of paragraph (52) that authorities at the time of occurrence will be following the same system of radiological protection as currently invoked by ICRP is questionable.
The merits of the proposed change to the treatment of natural disruptive events are not obvious, and the need for change is questioned.
3 RELEVANT TIMESCALES FOR RADIOLOGICaL PROTECTION
The draft report introduces a framework for radiological protection in geological disposal based upon a set of timescales. The section introducing these timescales is difficult to follow and would benefit from further clarification; clarity is needed on what is expected during each of the defined timeframes. The proposed timescales appear to reflect a particular view on how a geological disposal programme should be implemented and regulated. This view does not align well with proposals in the UK or other countries to our knowledge, and therefore we question whether it is sufficiently general for the purposes of ICRP recommendations.
Further, the proposed timeframes are not defined or explained consistently through the report. It is not clear what the basis is for the proposed timeframes, particularly the ‘time of indirect oversight’ timeframe which remains a little unclear as a concept, and does not provide a suitable distinction for radiological protection purposes. In general there needs to be more clarity in the definition of the periods of oversight, how they overlap, and what is expected during each of the periods of oversight. It would be much preferable if the report used established timeframes concepts such as those laid out in the International Atomic Energy Agency Safety Standard on ‘Disposal of Radioactive Waste’ .
4 Other comments
It is questionable whether this document needs to be stand-alone (as stated in paragraph (9)), and whether the draft achieves this. If the document were not stand-alone, greater focus could be provided on what is specific to geological disposal, reducing the document’s length and avoiding duplication of material already included in Publication 103.
There does not appear to be much in the draft that is new and there is significant summarising of other ICRP documents which could be read as conflicting with statements made in the draft document concerning its approach to existing information. Following on from this it is interesting to note that starting on line 436 the document states that “Previous ICRP recommendations for the radiological protection of ...... in the case of near surface disposal facilities or other disposal options are still valid”. They may be still valid, but this raises the question as to why previous recommendations for geological disposal are apparently not valid. If geological disposal is being treated differently by ICRP, it would be helpful if a reason were given in the report.
In line 68 an alternative and we suggest a more likely possibility could be a considered decision that oversight is no longer needed or appropriate. It would be helpful if this point were recognised both here and in associated text through the report. Furthermore, this could be the position immediately after closure; we suggest it should not be linked to the proposed timeframes in this report.
‘Loss of control’ is not necessarily an appropriate phrase for a geological disposal facility based on passive safety (line 132).
There is inconsistency on which reports are being updated (lines 40 & 134).
The Abstract, Executive Summary and parts of the Introduction are not sufficiently clear or ‘stand-alone’, becoming understandable only in conjunction with the remainder of the document.
Line 177 implies that this is the explanation for "geological" in geological disposal which is not the case. "Geological timescales" would normally be considered to be hundreds of millions of years.
If ‘long term’ means post-closure, as implied, there is little potential for further optimisation, except by keeping people away from certain areas; the meaning of line 208 needs to be clarified. Again the IAEA concept of institutional control would be much more appropriate than the vague concept of indirect oversight.
In line 212 remove quotation marks.
In line 221 “looses” should be “loses”.
In lines 236 “indirect oversight” is equated with “direct regulatory oversight” which “might be supplemented or replaced by institutional oversight”. The meaning and significance of these statements is not clear.
In line 239 absence of oversight is equated to the post-closure period in the distant future; as noted above this would not necessarily be the case. It is further equated to the point when memory is lost; again this would not necessarily be the case. These points should be recognised. (These comments also apply to lines 670 and 671).
In line 240 it is not clear why keeping memory of the site is a primary objective.
In line 247 we suggest that the word “largely” requires explanation or, better, deletion.
In line 261 a reference is required for the reference level range.
In line 272 there is confusing use of timescales, and throughout the document, e.g. 'in the distant future' (line 211), 'time scales that are comparable with geological changes' (line 321).
In lines 302 and 303 we suggest deletion of the text “they need to be handled remotely, for hundreds or thousands of years”. For example, much of the waste emplaced in the WIPP facility for transuranic wastes (long-lived ILW) does not require remote handling.
In line 303 the draft could usefully recognise that lower specific activity and/or shorter half-life waste might also be put in a geological disposal facility.
In line 316, add “deep underground” after “shafts”.
In line 330, delete “that”.
In line 331, the syntax of the whole sentence requires correction, and amendment: “no exposure is ever intended” is too strong, or needs more context. Operators are expected to receive doses, and the release of radionuclides to the biosphere at very long times post-closure cannot be ruled out, which could lead to exposure.
In line 333, include the word “passive” after “whose”.
In line 339 and throughout, the draft’s discussion of human intrusion should focus on the low likelihood of this, and require planning for a low likelihood. The emphasis on the health consequences to the intruder obscures the objective of geological disposal.
Lines 376 to 378 are not consistent with the document being ‘stand-alone’.
Lines 436 to 438 need to explain why, when the system of protection has been updated with ICRP 103, a similar document for near-surface disposal is not deemed necessary by ICRP. Also, references are required here.
3.1 Protection of future generations
In line 448, replace “into” by “in”.
In lines 451 and 452, replace from “may” to the end with “will be hazardous for very long periods of time”.
In line 466 insert “radiation” after “ionising”.
The quotation in line 470 to 472 does not seem to appear in ICRP 77.
In line 508 the word “nominal” seems inappropriate and should be deleted.
In line 519 replace “group of population” by “population group”.
In line 532 it would be helpful to explain the fundamental assumption/assertion that concentrate and contain is always to be preferred over dilute and disperse.
In line 535, it is counter-intuitive why the ‘waste containment system’ should be included as posing a hazard; the text “and the waste containment system” should be deleted.
3.2.2 Life phases of a disposal facility
It is unclear what paragraph (24) contributes to consideration of radiological protection. The definitions given plus the implication that both reversibility and retrievability must be accommodated are highly contentious so it is recommended that this paragraph should be deleted.
In Fig. 1 “Decison to Begin Disposal” should be “Decision to Begin Disposal”.
In line 591 replace “will” with “may” in order to allow for strategies of delayed backfilling.
In line 606 it needs to be made clearer that the ‘observation period’ is optional.
In lines 621 to 624 (period of indirect oversight) it would be helpful if the draft included more guidance on what monitoring might be required to provide continued radiological protection after regulatory control is withdrawn. It should also be recognised that measures such as markers to identify the location of a disposal facility may have the opposite of the intended effect and will not, as stated, necessarily be used in all disposal programmes.
In line 626 “can be ruled out” is too strong.
In line 627, the implication that indirect oversight should ideally continue forever should be corrected as it runs counter to the principles of geological disposal explained elsewhere in the report.
In line 635, we suggest that if loss of oversight does not affect protection capability, then the proposed timeframe approach may not be appropriate.
In line 638 it is not clear why the draft requires updates of the safety case post closure in relation to evaluating protection capability since this evaluation would be required at the time of closure and would not be expected to change thereafter.
It would be helpful if line 639 explained how long the safety case would need to be updated for. As written this seems to imply that the safety case will continue to be updated after closure, and it is questionable whether this would be required, and for how long this would be practicable.
It is suggested that this document is not the place to describe what a safety case should include (line 642). In general the document needs to focus more on its core purpose.
3.2.3 Timeframes for radiological protection
Line 656 presents a different scope than that presented earlier which had been about interpreting ICRP 103 for geological disposal, rather than about how to use criteria in safety assessment for geological disposal. We suggest this is outside the scope of the document.
Line 666 does not recognise that ‘direct oversight’ could go beyond the operational phase.
In some places, e.g. Abstract and lines 671 and 692, the document seems to miss the planned intent for safety to be provided by purely passive measures at a suitable point in the future, e.g. because we know oversight cannot be guaranteed. It implies that we may just drift into this state, e.g. because memory is lost, implicitly leaving the regulatory regime, etc. Indeed, line 1084 could be implying a benefit in maintaining oversight for the purposes of ongoing optimisation but this cannot be substantiated.
In lines 675 and 676, it is the operator’s responsibility to protect workers, the public and the environment; the text needs rewriting to make this clear.
Line 682 may have the effect of raising unrealistic expectations.
The meaning of the sentence beginning on line 683 is unclear.
It is not clear why regulators and society would wish to maintain forms of oversight and memory as long as possible (lines 690 and 691).
In line 691 “there” should be replaced with “their”.
In line 692 it is arguable that the geological disposal facility will have already been outside the regulatory regime for some time at that point. The sentence reads as if it were acceptable to have a system where a facility ‘implicitly leaves the regulatory regime’ when everyone has forgotten about it. It would be preferable to have an explicit decision to demarcate when permissioning is no longer necessary.
In line 698 "potential" is not an appropriate word – it should be the capability to contain and isolate waste.
In line 700 it would be helpful to make clear if ‘passive control’ is intended to mean the same as ‘indirect oversight’ or not.
In line 710 there is no “control” against inadvertent intrusion, rather a low likelihood.
There is no justification for the assertion in lines 712 and 713 concerning the duration of direct oversight.
The meaning of the paragraph between lines 717 and 719 is unclear.
4 ICRP system of protection
In line 736, “Re-enforcing” should be “Reinforcing”.
4.2 Dose and risk concepts
In line 803, the probability of “detriment” should be considered alongside that of cancer, in line with ICRP 103.
4.3.2 Exposure situations for emplaced waste
In line 878 it needs to be made clear that the ‘appropriate environmental compartment’ refers to modelling, not real life as discussed here.
In line 891 a different risk to dose conversion factor is used than that used in paragraph 42. If different assumptions about the way workers are affected by radiation than public are being used, they should be explained.
In lines 899 to 901 the report envisages the persistence in the distant future of a radiological protection framework as currently invoked by ICRP. This is not credible and needs to be reconsidered.
In line 901 replace “are inherently unknowable” with “cannot be predicted in advance”.
4.3.4 Inadvertent human intrusion
In line 960 it is not clear whether ‘indirectly related’ and ‘incidental’ are intended to be different descriptors.
In line 963 and 964 the text “elevated exposures … inescapable consequence” depends on the measure. Dilute and disperse would also lead to elevated exposures in terms of collective dose. Focusing on the low likelihood of human intrusion, even when geological disposal has been forgotten, due to good siting and pure chance (frequency of drilling) is arguably a better way of dealing with this issue.
In line 964, replace “isolate” by “concentrate”.
Line 968 (“may include”) is not consistent with line 956 (“will have to include”).
In line 971 the explanation of direct oversight seems to be that given previously for indirect oversight.
The paragraph starting at line 976 is mainly about making a safety case for potential human intrusion, and so is outside the scope of this document and should be deleted.
4.3.5 Exposure situation summary
In line 997 the title is unclear.
Reference is made to reducing impacts radiological and others, and socioeconomic factors constraining the optimisation process to various extents. It would be helpful if there was more discussion on the treatment of conventional safety and environmental impacts in optimisation studies, in the context of radiological protection.
In lines 1036 and 1037 it is unclear if the phrase “safety has to be ensured by a passively functioning disposal system” is intended to apply to all time periods, and recognises the potential role of active controls during operational time periods.
In line 1042 it is proposed that optimisation has to cover the site and host formation. It must be recognised in this paragraph that this aspect is subject to important constraints from the application of processes that take account of the socio-political context, as then detailed in paragraph (66).
In line 1054 replace “constraint” with “constrain”.
In line 1084 it is questionable whether this is the best, or even an effective, approach, and whether maintenance of oversight of a passively safe facility into the very long term complies with the optimisation requirement to take economic and societal factors into account.
Paragraph (73) starting at line 1106 is outside the scope of this document.
In the paragraph beginning with line 1112, it should be recognised that the application of BAT allows a wider range of relevant criteria including voluntarism to be considered.
In line 1133 the meaning of “windows” is not clear.
In line 1143, add “protection of engineered barriers” after “long-term stability”.
In line 1145 replace “supra-local” with “regional”.
5 Endpoint considerations
It is not clear that section 5 is required in the document.
In line 1190 “discreet” should be “discrete”.
In line 1219 insert “calculation / modelling of” after “that”.
In line 1222 insert “and the half-life of the radionuclide concerned” after “body”.
5.2 Protection of the environment
In line 1232 replace “Illustration” with “A demonstration”.
In line 1235 remove “of ethical nature”.
In line 1260 replace “addressed” with “address”.
In line 1266 replace “glaciations” with “glaciation”.
It is unclear why there are different sets of references in sections 1.1 and 6.
In line 1346 it is arguable that this is the purpose of the whole document. It is not clear that the information should be presented in an annex – it should form the core of the main document. Since this Annex repeats much of the content of Section 4 of the draft report but sometimes in different terms, e.g. the explanation of effective dose given in lines 1463 and 1464 compared with lines 793 and 794, it should be integrated into Section 4.
In line 1347 “waste disposal” should be replaced with “geological disposal of long-lived solid radioactive waste”.
In line 1405 “residual dose” is not defined until line 1469.
In line 1416 insert “regulatory” before “authority”.
In line 1463 it would be helpful if the word “practical” were clarified in light of the bullets above, e.g. is it the prospective dose assessment?
In line 1482 remove “(B 174)”
In line 1492 it is recommended that Table 8 of ICRP 103 is reproduced as it is referenced multiple times, and the draft is intended to be a stand-alone document.
In line 1557 insert “radiation” after “ionising”.
In line 1587 replace “favouring” with “advancing”.
In line 1622 replace “introduce” with “introduces”.
It is not clear what the purpose of this annex is, as it does not appear to add much, containing solely lengthy quotations from other ICRP documents and a summary paragraph. The ICRP documents in this annex are not referenced.
In line 1651, it is questionable why there is a need to refer back to a conference held in 1955.
In lines 1803 and 1804 “desing” should be “design”.
In line 1804 “depository” should be “disposal”.
It would be helpful if the purpose of this annex were described.
In line 1818 it is unclear what is intended by “largely” so this word should be deleted.
In line 1824, we suggest deletion of “for as long as needed” since this implies that some cliff-edge increase in radiological impacts might be deemed acceptable. This emphasises the failure of the draft report to deal with the issue of potential releases at very long times in the future.
In lines 1870 and 1871 the abbreviation “a.o.” is unexplained.
9 November 2011