COMMENTS FROM THE BELGIAN FEDERAL AGENCY FOR NUCLEAR CONTROL
The adopted subdivision in timeframes according to the types of oversight is questionable.
The term “oversight” is quite vague. Indeed, “oversight” can cover a large range of activities and/or measures that can be included or not in the regulatory regime. This could lead to many different interpretations of the timeframes to be considered for the purpose of radioprotection.
Table 1 from the document might, at first sight, give the impression that:
Such potential misinterpretation should be avoided in the communication with the various stakeholders, and hence table 1 needs to be reconsidered.
Moreover, this subdivision leads to confusion because the long-term safety of a geological disposal facility should not rely on the level of oversight as suggested in the text. Indeed, moving towards the post-closure phase means that safety is eventually ensured by only passive means.
Linking the period where oversight is lost to “emergency exposure situations” or “existing exposure situations” for beyond design basis events and human intrusion is inappropriate.
By definition, the beyond design basis events are considered as having a too low risk to be reasonably considered for design or optimisation purposes. Some beyond design basis consequences can be evaluated (for example through “what if” scenarios), but must not be compared to the constraints of “emergency exposure situations” or “existing exposure situations”.
If it is considered that less- likely events could happen, they should be treated in the SC. Indeed, if the repository design and its assessment are correctly performed, considering all reasonable possible events (likely and less-likely) that could affect the disposal system, than an “emergency situation” should not be likely to occur. For the demonstration of robustness of the system, “what-if” scenarios (extremely unlikely events) may be considered. “Emergency exposure situations” or “existing exposure situations” and their associated dose constraints should be applied only when the situation occurs despite all precautions taken during the design development and assessment. These situations would then be handled as appropriate to the protection guidelines at that time.
It should be explicitly and clearly mentioned in the document that only the criteria associated with the "design-basis" evolutions (i.e. planned exposure situations) are to be used when designing the disposal system. This is not the case in the current version of the document which may lead to misinterpretations.
How far are previous ICRP publications 46, 77, 81 still valid?
As the document “updates” previous ICRP publications (46, 77, 81), it should be clear, which parts of previous publications are no longer valid.
Inconsistencies with ICRP 103
Some inconsistencies with ICRP 103 were noted (see specific comments).
Optimisation and best available techniques
The subject of “Optimisation and best available techniques” is well developed in this document.
Some elements of the safety strategy such as the implementation of multiple safety functions (independent and complementary) could be more developed.
63-64 & 660-661 "The level of oversight affects the capability to reduce or avoid exposures". This is true for the operational period. However after closure, this is contradictory to the international recommendation that the disposal system should be passively safe.
181 The term “reduced” is preferred to “diluted”. Indeed, at long term “dilution” could be unavoidable but it should not be considered as a safety function.
188-192 ‘evolutions’ is preferred to ‘…. developments ...’.
201 “It has to cover … including the societal component” – It should be clear that the societal component has to be taken into account during the optimisation process but it does not constitute an element to be optimised.
205 ‘… (BAT) …’: In other documents, ICRP uses the term “BATNEEC” (cfr. ICRP 81 §35).
208-209 “In the long term optimisation of protection can only be achieved if oversight is maintained.” This is not correct. Indeed, after the closure of the disposal, optimisation is no longer possible. “In the long term optimisation of protection” is confusing with “optimisation of the long term protection”, which starts in the early phase of the repository development.
216 + 227 + 283 + 841 - 890 The text is not conform with the ICRP 103 recommendation where we can read “an annual dose constraint of no more than about 0.3 mSv in a year”.
236-237 This sentence has to be brought in line with the definition of “time of indirect oversight” (lines 666-669), or vice versa, which seems more appropriate in view of the sequential sealing of the disposal galleries.
245-249 This sentence is ambiguous. Low probability but plausible events remain in the scope of “planned exposure”. “Severe disturbing events” should be better described. They might be included in the design basis (likely or less-likely events; planned exposure situation and as subcategory potential exposure) or might be treated as “what if” scenarios (extreme disturbing events; extremely unlikely to happen). Emergency exposure situations should be seen as unlikely situations, which require urgent action to avoid or to reduce undesirable consequences. It should be clearly stated that this sentence addresses such unlikely events.
257-259 "design basis evolution" should be replaced by "design basis evolutionS" since several evolutions (i.e all evolutions covered by the E(xpected)E(volution)S(cenario’s) and the A(ltered)ES) have to be considered in the safety assessment and therefore in the design. Indeed, the system should be designed such that any degradation of a safety function or of a component that can be reasonnably envisaged, does not result in an unacceptable risk (the risk should always remain below the risk constraint). Moreover, it is not correct to distinguish between "safety" and "robustness" since a safe system has to be robust.
330-337 + 563 Safety strategies, objectives and safety functions are mixed up. It should be clear that the “Concentrate and retain” strategy relate to the overall waste strategy and the “isolate and contain” strategy relates to the geological disposal strategy.
425-438 The argumentation of why these recommendations do not address near-surface repositories is neither obvious nor convincing. It is wrong to state that geological barriers are of secondary importance as it depends on the safety concept. Second and third sentences of § 13 should therefore be suppressed or at least modified.
463-474 IAEA SF1 principle 7 should also be referred to.
571-636 According to the text, discrete licenses are granted at discrete steps in the life time of the disposal facility. Since each country has its own licensing process, considering discrete phases or periods, this text can only be considered as an example of when a license should be granted. It is therefore recommended in this section to avoid referring to licences that are granted at a certain moment.
619-626 There seems to be a contradiction between the statement saying that "safety is assured totally through the intrinsic, built-in provisions of the design" and the one saying that "Inadvertent human intrusion in the disposal facility can be ruled out" due to the presence of an indirect oversight.
635-638 The sentence "The loss of oversight does not result in a change of the protection capability of the disposal facility" could be interpreted as contradictory to the statement that, as a consequence of the loss of oversight, inadvertent intrusion cannot be ruled out anymore.
649-653 The last sentence of this paragraph has no relationship with the rest of the paragraph.
675-678 This sentence should be reformulated because it is not the role of the regulator and of the other stakeholders to "manage the protection" since only the operator is responsible for the safety of his facility.
690-692 The paragraph is not clear and should be reconsidered.
708-709 "… the waste is out of sight and stored at great distance from the part of the biosphere that people normally inhabit" should be replaced by "...… the waste is out of sight and disposed of at great distance from the biosphere". Indeed, in the long term it is not possible to determine what is the "part of the biosphere that people normally inhabit". Moreover, the waste has to be isolated not only from humans but also from the biosphere in general.
754-756 The assessment of the justification principle should "include considerations of different options for waste management and disposal including the justification of these options". This evaluation seems to be very similar to what is expected for the principle of optimisation of protection. Therefore, the distinction between these two principles should be better explained.
812-817 The paragraph is not exactly what is mentioned in ICRP 103. The words “everyday” should be suppressed.
857-869 Used terminology: significant release, possibility of an eventual release, these … potential releases, might be confusing in reading this § 45, especially in the context of releases “inherent in the concept”.
From the text, it is not clear which releases are meant to be considered as “normal exposure” or potential exposure”.
899-900 Might not only be an existing exposure situation but also an emergency exposure situation (intrusion scenario).
914-917 The regulatory body may develop guidance to address natural events but it is not his responsibility to develop a strategy (responsibility of the operator).
921-938 The document mentions that the planned exposure situation applies to expected and less likely events. Therefore all reasonably possible severe natural disruptive events have to be treated as planned exposure situations when designing the disposal system. This is not straightforward from § 52 (see also comment about lines 944-949).
Similarly to § 49, it should be mentioned that situations of this kind would be handled as appropriate to the protection guidelines at the time.
944-949 What is mentioned in ICRP 103 seems not to be in line with the following:
- at lines 925-926 it is said that the natural disruptive events in the design basis should be treated as “planned exposure situations”;
- at line 928:… that the ones outside the design basis should be considered as “emergency or existing exposure situations”;
- now at 944-949, it is said that all natural disruptive events (as well within as outside design basis?) giving rise to exposures (without mentioning the severity?) should be looked at as existing exposure situations (see also comment at lines 921-938).
973-975 It should be mentioned here that the reason for not considering human intrusion is that the site is known and under regulatory control which should guarantee the absence of human intrusion at this period. It is also preferable to rephrase it as “human intrusion is not considered to happen”, rather than to talk about “probability zero”, as this is certainly not the case.
988-996 The fact that dose constraints are not applicable to human intrusion for optimisation purposes is due to the fact that the “concentrate and contain” strategy implies that doses due to human intrusions might be lethal, even in the very long term, considering the radiological toxicity of the waste. If a dose constraint would be considered for direct effects of human intrusion, than no “concentrate and contain” strategy can be applied. This seems to be the primary reason for not considering such a constraint. The reason explained in the text, linked to a comparison to surface waste disposal, is questionable, as the explanation given is also valid for surface disposal where the optimised protection is also completely bypassed due to a human intrusion. Moreover, a difference could be made between direct and indirect effects of human intrusion, where for the indirect effects – e.g. degradation of barriers – dose constraint might be a parameter considered in the optimisation of the design provisions.
1084 This sentence might be misunderstood since oversight can not be considered as a protection in the long term. Safety should be based solely on passive means in the long term.
1190 “may” should be replaced by “might”.
1198 Replace "more highly exposed individuals" by “most highly exposed individuals …”.
1201-1202 “This is an assumption since the environment may have evolved such that humans are no longer inhabiting these areas in the far future.” Such sentence provides no useful information and could be omitted.
1204-1213 When comparing sites, it could be useful to use a stylized generic biosphere and representative person in order to compare in a first stage their intrinsic safety protection level. A more specific biosphere could be used in a later phase.