The Australian National Radioactive Waste Repository: Environmental Impact Statement and Radiological Risk Assessment

The Environmental Impact Statement (EIS) for the proposed Australian National Repository for low and short-lived intermediate level radioactive waste was submitted to Environment Australia for approval in the summer of 2002 and has subsequently undergone a consultancy phase with comments sought from all relevant stakeholders. The consultancy period is now closed and responses to the comments have been prepared. This paper describes some of the issues relevant to determining the radiological risk associated with the repository to meet the requirements of the EIS. These include a brief description of the three proposed sites, a description of the proposed trench design, an analysis of the radioactive waste inventory, the proposed approach to developing waste acceptance criteria (WAC) and the approach taken to determine radiological risks during the post-institutional control phase. The three potential sites for the repository are located near the Australian Department of Defence site at Woomera, South Australia. One site is inside the Defense site and two are located nearby, but outside of the site perimeter. All have very similar, but not identical, topographical, geological and hydrogeological characteristics. A very simple trench design has been proposed 15 m deep and with 5 m of cover. One possible variant may be the construction of deeper borehole type vaults to dispose of the more active radioactive sources. A breakdown of the current and predicted future inventory will be presented. The current wastes are dominated in terms of volume by some contaminated soils, resulting from experiments to extract U and Th, and by the operational wastes from the HIFAR research reactor at ANSTO. A significant proportion of the radionuclide inventory is associated with small volumes of sources held by industry, medical, research and defence organisations. The proposed WAC will be described. These are based on the current Australian guidelines and best international practice. The preliminary radiological risk assessment considered the post-institutional control phase in detail with some 12 scenarios being assessed. These include the impact of potential climate change in the region. The results from the risk assessment will be presented and discussed. The assessment work is continuing and will support the license application for construction and operation of the site. Please note that this is not the final assessment for the licence application.