Summary and Conclusions
The AECL postclosure reference case study raises problems. In addition to the fact that it is site specific and has not been demonstrated to be applicable to various other potential fuel waste repository sites in the Canadian Shield, there are problems with unclear objectives, with methods of analysis, and with the validity of the results of the postclosure reference case study itself.
The assessment is based on predictions from numerical models. The SRG notes with concern that reliance on SYVAC has inhibited the introduction or use of more modern and flexible software and up-to-date data and has, to a degree, undermined the effectiveness of the assessments.
The SRG concludes that the results of the postclosure performance assessment are not reliable because:
- the reference case is too narrow a representative of the disposal concept;
- the conceptual framework for the reference case model is flawed;
- the choice of input parameteres, initial and boundary conditions, and source terms for the model are not satisfactory;
- the uncertainty analysis is not convincing; and
- the modelling of the exposure of humans and other living organisms to contaminants passing through the biosphere does not accomodate the likelihood of environmental or ecological changes over a 10,000 year period.
On the basis of these shortcomings, and its review of the detailed descriptions of the concept presented in the EIS and the supporting primary reference documents, the SRG disagrees with AECL's conclusion that:
"The methodology to evaluate the safety of a disposal system against established safety criteria, guidelines and standards has been developed and demonstrated to the extent reasonably achievable in a generic research program."
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