Defining Human Receptors for Assessing Post-closure Safety of Canada's DGR

Abstract

The Nuclear Waste Management Organization (NWMO) is responsible for the implementation of Adaptive Phased Management. Under this plan, used nuclear fuel will ultimately be placed within a deep geological repository in a suitable host rock formation. The NWMO is currently in the siting process, working towards site selection in 2024. Two areas remain in our site selection process: the Wabigoon Lake Ojibway Nation-Ignace area in north-western Ontario and the Saugeen Ojibway Nation-South Bruce area in southern Ontario. The NWMO has been developing preliminary post- closure safety analysis to support site selection.

A primary endpoint of post-closure safety analysis is an estimate of potential doses that someone living in the area — a receptor — could receive under imagined failure scenarios. To measure repository performance and demonstrate safety, hypothetical doses for the receptor are compared to set dose-benchmarks. The dose received under imagined failure scenarios is largely dependent on a person’s lifestyle; specifically, the relationships they have with their environment.

Our site-specific post-closure safety analyses consider two different types of lifestyles: a most-exposed group and illustrative local lifestyles. The most-exposed group is a receptor designed to maximise potential dose from the repository and demonstrate that present regulatory limits would be met, independent of the potential landscape and social evolutions. The illustrative local lifestyles demonstrate the safety of the repository as it relates to local communities’ current and past practices. Illustrative local lifestyles include various Indigenous, town resident, and rural lifestyles. This paper describes how the different receptors were selected, the characteristics of each lifestyle, and exposure pathways relevant to each lifestyle.