Understanding the subsurface migration of actinides is vital for the development of robust and reliable performance assessment models of actinide bearing waste disposal facilities. Interaction with soil/rock surfaces is a primary mechanism controlling the mobility of actinides in the subsurface environment. In this work, fundamental studies of plutonium/actinide interactions with pure minerals and natural soils are presented in terms of the primary interfacial reactions including: sorption, redox reactions, and surface mediated precipitation. The primary focus of this review is the characterization of energetic driving forces responsible for the frequently observed strong sorption of actinides to mineral surfaces and surface mediated reduction of Pu(V) to Pu(IV). Comparisons of multiple experimental systems indicates that the strength of actinide sorption are proportional to hydration energy and effective charge of the given actinide ion. Observed reactions include formation of monomeric surface complexes, surface mediated redox reactions, aging or hysteretic sorption, and surface induced precipitation. The variability in these observed surface reactions of actinides requires a more detailed level of characterization of the surface speciation in order to accurately quantify actinide mobility in the environment. Examples of each type of reaction will be presented and discussed.

Characterization of reaction energies and speciation changes underlying strong actinide sorption to mineral surfaces

251st National Meeting (2016)

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