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Submitted by Nys Vincent, None
   Commenting as an individual
Document Radiological Protection in Geological Disposal of Long-lived Solid Radioactive Waste
 

Level 1 – Comment

 

Comment 1

The concept of “oversight” is a key concept around which the document is structured.

For long term safety, this draft proposal of ICRP recommendation is more or less structured around the effectiveness or not of an oversight. The effectiveness of the “Oversight” could be envisaged for time frames that are much higher that what can be found in current international standards. This concept also implies new objective as “keep memory of the site”.

 

Moreover these current standards don’t rely on the effectiveness of an oversight for periods that are higher than few centuries.

 

This oversight could be assumed with time by different actors, like regulatory body or others State organisms. Although each country could develop its own “oversight politic”, it would be useful to provide some more developments in this ICRP recommendation on the “oversight” concept and on the responsibility of the entity in charge of the “oversight”

Nevertheless this “oversight” concept if it clarifies a managed approach for the long term, instigates the following questions:

-         Does the period of the indirect oversight not be defined according the hazard of the disposal?

-         ICRP suppose that with time oversight will progressively disappear. This is one possibility but the management of “oversight” with time has to be discussed.

 

 

Lines 58 up to 69

The concept of “oversight” has to be clarified. Who is in charge of the oversight? Is it the State? Is the regulatory body? Does it mean that there is an oversight as long as the facility is licensed?

 

Line 173

Should the concept of “Direct oversight” not start at the construction decision?

 

Line 632

For geological disposal facilities, a war when the indirect oversight is over seems not to be a significant event. Surface disposal facilities are more concerned by a war event.

 

Line 635

The last sentence of this paragraph should be removed or modified. When the indirect oversight will be over, only main consequence will be an increase of the occurrence of human intrusion but the consequence for the intruder are independent of the effectiveness or not of the “Oversight” (see lines 700 up to 711). The end of the indirect oversight will modified the risk magnitude, not the consequence.

 

Suggestion: The loss of oversight does not result in a change of the intrinsic protective capability of the disposal facility (see line 699 up to 699).

 

Line 692

No implicit leave of the regulatory regime is conceivable. This sentence is in contradiction with the paragraph (717 – 719).

Either, during the indirect oversight the facility is still under a regulatory regime and in this case an implicit leave is not conceivable, either during the indirect oversight, a release of the regulatory control has been done. In this last case, either there is a transfer to other authority or there is a check that residual hazard is acceptable.

 

Line 240

Explicitly ICRP identify “to keep memory of site” as an objective of disposal facility. What’s the substantiation for defining such objective? The IAEA SSR-5 document does not mention such an objective. Moreover this objective could be seen as contradictory with a geological disposal facility.

 

 

 

Comment 2

Role of the long term radiological calculation

In this document, ICRP seems to limit the role and the use of long term radiological calculation to a tool for assessing comparison.

Why doesn’t ICRP also mention that dose could also be used as a reference value and could be used with other indicators for judging the acceptability of the radiological consequence of a given scenario?

Long term evaluation of the exposures are indeed not predictions but they serve to ensure that radiological impact are below a defined value or similar to this value depending of the considered time frame or scenarios.

Safety assessment could not just see as comparison of options

 

Lines 226 up to 227 & lines 860 up to 865

To which kind of comparisons refer the ICRP when they written that « Hence, the annual dose constraint of 0.3 mSv in a year is to be used for the sake of comparison of options rather than as means of assessing health detriment. ».

For the far future, even if there is a strict relation between health detriment and the dose, dose could be used for more than a comparison of option.

 

Lines 354 up to 355

Such statement should be complemented by saying that in most of the safety assessment a part of the demonstration is dedicated to demonstrate that the main safety structures, components and systems are protected and keep their functioning in case of disturbing events.

 

Lines 681 up to 689

Taking into account the fact that indirect oversight will mainly act on the intrusion occurrence, ICRP should recommend maintaining as long as possible the period of indirect oversight. Opening a discussion on criteria or on decision process dealing with a reduction of the level of oversight, seems not be recommended.

Stop of the indirect oversight should be due to war, social instability or lost of memory but not due to a decision except if as for surface disposal facility, the hazard is acceptable taking into account all reasonable events.

 

 

 

Comment 3

Emergency situation - Management of the beyond design event

Generally speaking, the approach develops in this new ICRP recommendation for managing non design basis evolution is without complementary explanation quite difficult to consider.

First, in the proposed development, there is no reference to the DIP principle as if this important safety principle is not a part of the safety strategy.

Second, the safety case should be such that it’s demonstrated that most of the low probability events if they occur could not generate in the far future an emergency situation.

By design and conception, in this proposal of ICRP recommendations, the scope of the design basis evolution is quite limited. Indeed, most of the events with a low probability of occurrence will be assessed in comparison with the reference level of emergency situation. Such approach could encourage the operator to limited the scope of the events that should be considered in the design basis because it will be much easier to treat degraded scenarios if they belong to emergency exposure.

 

Lines 245 up to 255.

This development is questionable. It has to be clearly mentioned that by design it has to demonstrate that low probability but plausible events should not lead to emergency situation in the far future if they occurs. During the design phase, these situations remain in the scope of “planned exposure”. The safety assessment has not to deal with exposure situations.

 

Lines 894 up to 902

Two situations have to be distinguished:

-         The first situation is the one developed in the ICRP. Future generation discover a contamination or create a contamination. They have to treat the situation according to their regulation. Based on our current standard, we would say that has to be considered as an existing situation.

-         The second is not developed in the ICRP proposal. By design, if such event occurs, it has to be demonstrated that except the case of human intrusion, that in no reasonable assumptions to believe that there will be a need for the future generation to decided that they are facing according to our current standard to a emergency situation.

 

Lines 921 up to 938

Why ICRP distinguishes only for natural events those who are included in the design basis evolution from those who are not?

The development made by ICRP in this paragraph does no take into account the “Defence-in-depth” principle. Applying this principle in the safety case, it should be demonstrated that not all out of design basis events should lead to significant change of the level of contamination determined in the design basis evolution.

It seems not appropriate to consider the reference level of an emergency situation for the severe natural disruptive events out of the design basis because site choice and design should be such that not emergency situation should be generated. Whatever what reasonably could happened should not lead the future generation to be face to an emergency situation.

Once again ICRP does not take the delay between the event and the observations of the contaminations into account. The memory of the event could completely forget when the first indications of an earlier contamination are observed.

What does ICRP understood by implementing some protective actions when dealing with a geological disposal facility (more few hundred meters)?

 

Comment 4

Substantiation of restricted scope of the recommendation to geological disposal

As this paragraph be aimed at justified that a specific guide as to be developed for geological disposal facilities and not for surface disposal facilities, it is strongly recommended to ICRP to improve this paragraph and to provide unquestionable arguments.

According to me, geological disposal facility has to be managed in a different due to the fact that when the confidence in the indirect oversight is over, by design the hazard of a surface disposal facility should be acceptable whatever could be the considered events. Such assumption could not be made for geological disposal. Indeed, due to the waste intended to be disposed of in a geological disposal facility, when the confidence in the indirect oversight is over, still the hazard could high.

This level 1 comment 4 is also high coupled with the level comment 1 “Oversight”

 

Lines 425 up to 438

Near surface facility like trench rely mainly not on engineered barriers but on confinement properties of the environment. In this case attenuation properties of the surrounding rocks are one of the main safety properties.

The major differences between near and geological disposal facilities concept are the lower level of isolation protection provided by the surface disposal concept and the scale of the time frame for the long-term safety.

It’s not clear what ICRP means by the “presence of man” as a factor of difference between geological and surface disposal facilities.

One which basis could ICRP asserts that surface disposal facilities obey to a different regulatory regime..

     

 

Other level 1 Comment 5

 

 

Lines 514 up to 524

The analysis should be pursued and not limited to the design stage. At least the decision to license a disposal facility should be address.

 

Lines 976 up to 987

In his development, ICRP has to distinguish the direct radiological impact to the intruder from the delayed radiological impact generated by the intrusion.

-         As said by ICRP “intrusion means that many of the barriers which were considered in the optimization of protection for the disposal facility have been by-passed », in case of direct radiological impact, elevated doses could be generated to the intruder.

-         However, for the delayed effects generated by a human intrusion, the behaviour of the disposal system and the radiological impact has to be assessed as a planned situation because by design we know that when the oversight is over, the occurrence of human intrusion increased quite significantly.

 

Line 914

Why ICRP think that it is the duty of the regulatory body to develop a strategy for addressing such events en why does recommend ICRP to develop it with the stakeholder? Regulatory body could develop its own guidance but first it should be argued through the site characterisation that the occurrences of such events are low or extremely low.

 

Line 1004

See above for the discussion about the need or not of considering an emergency situation

 

Line 1005

The design basis is the envelope of both expected and low probability (potential) events but plausible events that are used in planning the facility

 

Level 2 – Comments

 

 

Lines 189 up to 192

For assessing the robustness of the system, we should not limit the condition to non design basis conditions. Other conditions could be used like what-if scenario.

Line 202

The formulation is quite light. For a geological disposal facility, the choice of the site is one of the major step of the optimisation of protection

Line 217

What does ICRP mean by adding “…without any weighting of doses in the far future. » ?

Line 259

“Outside the design” should be added after severe disturbing event.

Lines 330 & 331

According to IAEA SSR-5, the safety strategy should aim at “confine and isolate” the waste and not “confine and retain”.

Lines 338 up to 340

The high radiological consequence for the intruder is indeed a consequence of the decision to concentrate waste in a disposal facility but is also related to the type of waste. As geological disposal is dedicated to hosted high level waste, this characteristic is preeminent comparing to the concentration strategy.

Line 563

Strategy of “Contain & isolate” instead of “concentrate & contain”

Lines 594 & 595

Would it be not more appropriate to replace « with other stakeholder » which is too hazy, by « with other regulatory authority » when dealing with who is in charge of the oversight?

Lines 649 up to 653

The last sentence of this paragraph has no relationship with the rest of the paragraph.

Lines 1191 & 1192

“Thus, the scenario leading to the highest dose may not be linked to the highest risk” this sentence is only true for less likely (potential) event when the probability of the events could be quantified with a certain confidence.

Lines 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 provide no useful information and could be easily deleted.

Lines 1204 up to 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.