Panel Report

The Panel suggests that the following issues receive full consideration during a public review of AECB regulatory documents, as recommended in section 6.1.3 of this report.

1. With regard to Regulatory Document R-104, the reviewers should determine whether the public accepts the use of a numerical risk factor-such as an annual risk no greater than one in a million fatal cancers and serious genetic effects-coupled with a fixed risk conversion factor that describes the relationship between dose and health risk. They may even decide to discontinue the use of such numerical risk factors. Safety evaluations for a waste repository calculate average annual (probable) effective doses to members of the critical group. Currently, R-104 specifies what is regarded as an acceptable level of risk and then converts this risk to an equivalent dose using a specified dose-risk conversion factor. However, new scientific data are likely to lead to ongoing, although small changes in this factor. Thus, consideration should be given to a regulatory safety standard based on a specified dose to the exposed individual, rather than on the associated risk. The scientific and public debate on the complex relationships between dose and risk is ongoing. This process should not be obscured, nor should it be allowed to call constantly into question a proposed facility's compliance with the regulations. A dose-based regulation might help to make the dose-risk discussion more explicit and visible, while giving the public a clear understanding of a proposed facility's compliance with the regulatory standards.
2. In any revision of Regulatory Document R-104, reviewers should consider how the calculated distribution of postclosure dose estimates for a proposed facility should be compared with the regulatory standards. Simply comparing the mean dose value derived from a population of results does not give the public any clear understanding of the way the results are distributed-that is, whether the results are tightly clustered or widely distributed around the mean value. Yet this is an important consideration in public perceptions of safety and uncertainty.
3. The Panel recognizes the AECB's concern, expressed in Regulatory Document R-104, about the uncertainties inherent in evaluating quantitative doses for periods greater than 10,000 years. This uncertainty leads to doubts about the usefulness of such calculations. However, with a well-engineered repository, the maximum dose to members of the critical group may not arise until long after this time period has elapsed. Consideration should be given to a regulatory requirement that states that, despite uncertainties, numerical dose estimates must be given for the postclosure period extending at least to the point at which they reach their maximum.
4. The Panel has received a number of submissions recommending that postclosure collective population doses be evaluated for any proposed repository design. The Panel notes that this is a requirement of applying the ALARA (as low as reasonably achievable) principle to operating nuclear facilities. [Atomic Energy Control Board, The Requirement to Keep All Exposures as Low as Reasonably Achievable, A Proposed Regulatory Policy Statement (Ottawa: Atomic Energy Control Board, Consultative Document C-129, issued for comments July 29, 1994), pp. 2-3.] This matter should be considered. However, the relationship between collective dose and collective detriment is highly controversial. In addition, current knowledge about population distribution and density in the distant future will likely be insufficient for making meaningful calculations.
5. The AECB should also review the directions in Regulatory Document R-104 that state that the lifestyle of the critical group should be based on present human behaviour using conservative yet reasonable assumptions, and that the group's diet and metabolic characteristics should be based on present knowledge.
6. At issue during the review was the Nuclear Liability Act, its applicability to a repository for nuclear fuel wastes, and the adequacy of its $75-million limit on the liability insurance that nuclear facility operators must maintain. This amount and the Act in general are currently under review. The Panel suggests that this review include a public consultation component.