Minerals for encapsulation of high-level nuclear waste: simulating damage and durability

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Radioactive waste disposal is the Achilles heel of nuclear power generation. The Eurobarometer poll of November 2001 revealed a majority of EU citizens would accept nuclear power if an assuredly safe and secure method of waste disposal was available. Yet concerns over the long-term aqueous durability of borosilicate glasses as hosts for high-level waste (HLW) have been noted since the 1970's. Learning from Nature, we have been using the fundamental insights provided by natural minerals to steer the search for synthetic materials that could far outperform the current glass technologies, especially in terms of how well they retain uranium and plutonium within their atomic scale structure when they are immersed in the potential groundwaters of a geological waste store. Our preliminary work has combined experimental work on the principles of crystalline architecture with computer simulations. These highlight the characteristics of damage to the surrounding crystal that occurs during radioactive decay, and show that the damaged regions form high-density shells around themselves. We propose to capitalise on our recent advances in understanding radiation damage accumulation in the mineral zircon, using accurate computer simulations, to test the hypothesis that zirconium and titanium oxides (with the pyrochlore structure) may be as impervious and robust in retaining radionuclides over geological time frames.