Euradwaste '08 - EU Bookshop - Europa

10-11 June 2008. The workshop was attended by 16 participants drawn from regulators and other
organisations with close interests in the management of uncertainties in the safety case for geological
disposal of radioactive waste. The workshop was facilitated by Roger Wilmot of GSL, and a
workshop report is available [5].
The workshop was grouped into three main sessions with contributed presentations, which provided
a stimulus for wider discussion of the issues:
1. Uncertainties in the safety case. This session addressed some of the key issues relating to the
treatment of uncertainty that are faced by regulators, and included summaries of previous work.
2. Regulatory guidance on the treatment of uncertainties. An important means for regulators to
influence the treatment of uncertainties is through guidance. This session described recent experience
in developing regulatory guidance.
3. Regulatory review of uncertainty treatment. Reviews and assessments of safety cases and license
applications allow regulators to determine whether their requirements and expectations
concerning the treatment of uncertainty have been met. This session described some recent review
experience.
A final discussion session that considered points that had been raised throughout the workshop is
summarised in Section 4.2. Key messages from the workshop are summarised in Section 4.3.
4.2 Discussion
Discussion of the regulatory review process highlighted some general points. First, the regulator
does not need to replicate the full safety assessment produced by a developer (a situation that pertained
earlier in the UK). Instead, the regulator is concerned with reviewing the research, development
and demonstration (RD&D) programme or safety case submitted by a developer, and in doing
so it will use its own capabilities to assess and evaluate key processes and uncertainties. Following
a review, a regulator is in a position to require the developer to carry out what it considers to be
necessary further research, site characterisation or assessment.
There is the question of when should the regulator request a developer to do a piece of research
rather than doing it itself. Research pursued by a regulator or regulatory support organisation is
likely to be focused on obtaining improvements in scientific and technical knowledge as a basis for
effective reviews and for maintaining and developing regulatory competence. In addition, a regulator
may carry out some ‘seed’ research in order to demonstrate to the developer that a research area
should be investigated in more detail. The Swiss regulator places importance on its experts staying
at the forefront of science and performing quality ‘independent’ research.
Although a developer has the primary responsibility to verify its codes, the question of how much
involvement a regulator should have in code verification was posed for discussion. During the
compliance certification (authorisation process) of the Waste Isolation Pilot Plant (WIPP) in the
US, the regulator requested the developer to re-run the assessment using regulator-provided parameter
values. Although this was not a code verification exercise, it circumvented the problem that
the regulator had no code to carry out its own independent assessment calculations. On the other
hand, the French, German, Swedish and Swiss regulators develop and maintain their own codes and
an independent capability for modelling radionuclide transport and PA. This is considered important
for verifying the developer’s results, for consideration of the assumptions buried in the codes,
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