The factors that influence the subsurface mobility of actinides will be discussed.  The overall fate of actinides, in particular those that are multivalent, is strongly coupled with the in-situ redox conditions that define the predominant oxidation state.  In the long-term, this is in part controlled by the associated biogeochemistry of a repository concept or subsurface contaminated site that is comprised of host rock interactions, microbial activity and interactions, and the prevalence of colloidal transport and formation.   These complexities need to be fully considered to establish the fate and transport of actinides under the range of subsurface conditions that are associated with known nuclear contamination issues.<br/>A repository concept, much like a near surface contaminated site, must also address these complex issues to define the safety case that drives the licensing and regulatory process.  The Waste Isolation Pilot Plant (WIPP), as one of the few working nuclear repositories in the world has addressed these issues and successfully defended its safety case in a series of re-certifications that are required by the regulatory process.  This repository concept, owing to the predominantly dry conditions and the high ionic strength brines expected should brine inundation occur, has addressed these fate and transport issues by configuring the safety case around this special chemistry.   This successful application of fate and transport concepts to the WIPP will also be discussed as a real-system example of these concepts. <br/>

Principles that guide fate and transport of actinides in the environment: Example application to the WIPP safety case

254th National Meeting (2017)

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