Natural immobilization processes aid the understanding of long-term evolution of deep geological radioactive waste repositories

Abstract

The majority of readers of Geochemistry: Exploration, Environment, Analysis (GEEA) are doubtless well aware of the numerous geochemical studies of ore bodies around the world (e.g. GEEA 2005), and the natural interest that the nuclear power industry has in uranium ore bodies in particular as the ultimate source of fuel for nuclear power plants (NPPs). Perhaps fewer are aware, however, of the interest that the power industry also has in uranium ore bodies as indicators of long-term isolation of radioactive wastes (‘radwastes’) produced by the very same NPPs. Admittedly, this is a relatively young field of study, going back less than three decades to the pioneering work on the Oklo natural reactor site in The Gabon in West Africa and the Morro do Ferro Th–rare-earth element (REE) body in Brazil (see Table 1 for details). The main thesis behind such studies is the very fact that many of these ore bodies have survived intact for aeons, despite significant changes in climate and geological conditions. They must have messages to impart which can be of use in the design and construction of radwaste repositories. This use of natural systems to help understand anthropogenic systems is generally termed ‘natural analogues’ (Chapman et al . 1984) in the radwaste industry. According to Miller et al . (2000), the term was first coined in the late 1970s and has since evolved. Come & Chapman (1986) stated that a natural analogue was ‘an occurrence of materials or processes which resemble those expected in a proposed geological waste repository’. McKinley (1989), however, stated that ‘the essence of a natural analogue is …