RELEVANT DEFINITIONS AND THEIR IMPLICATIONS 1. Disposal

According to the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management (the Joint Convention):

— ‘Disposal means the emplacement of spent fuel or radioactive waste in an appropriate facility without the intention of retrieval.’

The Joint Convention definition is appealing in that it is wide and covers sites whose safety is guaranteed both through the exercise of active controls — such as mill tailings and some surface facilities — and through passive provisions. Another advantage is that the word ‘disposal’ is used in a way that reflects common usage among the English speaking public. The disadvantage is that a ‘dump’ or low grade facility could also qualify as a disposal facility, for the Convention does not mention what is an ‘appropriate facility’. Presumably,

‘appropriate’ means ‘appropriate to achieve safety’. An alternative definition adapted from [2] and connecting disposal to safety is as follows:

— ‘Disposal is the radioactive waste management end-point meant to provide security and safety in a manner that does not require monitoring, maintenance and institutional control.’

This is a narrower definition than that of the Joint Convention. It was conceived in the context of geological disposal of long lived waste and would not apply to sites whose safety rests on active controls. However, it makes it

SESSION IIc

clear why that kind of disposal was proposed by society, namely, to protect future generations through means not requiring the direct presence of humans.

The difference in the two definitions raises the question about whether disposal is not too generic a term, and whether its use should not be qualified by, at least, the use of proper attributes, such as ‘monitored disposal’, ‘long term, monitored disposal’, ‘final, engineered disposal’, etc. in the way it is done in some non-English speaking countries. Indeed, surface repositories, mill tailings stabilization, or geological repositories for spent fuel entail very different disposal technologies and issues. Clear definitions — even different terms — would enhance communications among specialists and also help avoid misun-derstandings when communicating with the general public, who must be assured that ‘disposal’ is not synonymous, in any circumstances, with

‘dumping’.

2.2. Safety

Surprisingly, while safety¹ is the topic that unites a large number of efforts in the field of disposal, there is, to this author’s knowledge, no definition of safety applicable to the waste disposal field. For instance, the Joint Convention glossary does not define this term. In the absence of an agreed definition, the following one, taken from ongoing discussions within the OECD/NEA, is proposed:

— ‘Safety is an intrinsic property of a system. It represents its tendency not to cause (physical) harm. The “system”, in turn, is the ensemble of technical and administrative arrangements conceived to make it work over a given period of time.’

Ancillary observations related to safety are as follows:

— Over any defined time period, a system will or will not be safe regardless of our modelling capabilities. Namely, safety is not the result of modelling but of a series of provisions and technical arrangements that will also include modelling.

1 In this paper ‘safety’ in the technical sense is discussed. The paper by F. King — see these proceedings — examines ‘safety’ from the point of view of the local, host communities and societal decision making.

PESCATORE

— The way safety will be argued and documented (safety case) will raise (or not) our level of confidence (conviction) that safety is attainable under the conditions that have been described.

2.3. Confidence

According to Ref. [3]: ‘Confidence is to have reached a positive judgement that a given set of conclusions are well supported.’ Confidence building is then about the ways to enable a positive judgement to be reached that a given set of conclusions are well supported.

Because there is no one depository of the truth, there must be shared confidence among the main actors that are involved in decision making that the safety case for the decision at hand is a quality one. The best way to proceed is thus for all actors to develop factual and transparent ways to build confidence, namely, to evaluate and communicate their own confidence, in order to favour dialogue and quality in the decisions to be taken. Confidence is thus not a ‘trust me’ affair, but a ‘see what I did and judge for yourself’ affair and a ‘I am ready to have you test it’ affair.

Confidence must be shared in order for it to have any impact. A parallel to science can be made: a finding becomes a scientific fact and a part of science when many — and not just a single thinker — share the same positive view on the validity of the finding at hand.

It can be observed that in the case of (final) disposal, it will not be possible to validate one’s own confidence and provisions must be made to take account of the fact that, in the long term, society may lose the ability to verify that our judgement was right. An additional, important concept in this context is trust.

2.4. Trust

‘Trust is about accepting the transfer of control’.The granting of a licence for definitive closure of a repository containing long lived radioactive waste involves accepting that control has to be given up. It actually involves an act of trust in the technology and the legal and regulatory arrangements implemented by the current generation on behalf of future generations. The connection between trust and confidence is that trust is the result of a long chain of confidence building actions. Trust is gained slowly but can be lost rapidly.

SESSION IIc

2.5. Conclusions

‘Confidence’, ‘confidence building’, ‘trust’, and ‘control’ are fundamental concepts when preparing or judging a long term safety case for which safety does not rest on active controls. Confidence has to be shared for it to have an impact. Confidence building is what enables confidence to be gained and shared. In time, it will lead to trust.