Emerging areas of actinide science
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Actinide science is, in the broadest sense, the study of the properties and behavior of actinide elements in any physical form. The field, centered on the row of elements highlighted in Figure 1, has greatly advanced over the last decade.1–6 Nonetheless, actinide science remains underdeveloped, especially the study of elements beyond uranium in the periodic table. The reasons for this are clear: The theoretical tools used to explain and predict a material’s behavior are pushed to their limits, and experiments are expensive, with associated risk due to the radioactivity and toxicity of the materials. Actinide materials handling infrastructures are typically justified for the development and maintenance of nuclear weapons. However, if nuclear weapons arsenals were to be reduced in the future,7 does that imply a reduction, and finally the disappearance, of actinide research? Most definitely not. With the need for power to raise living standards across the globe, there is a growing demand for low-carbon energy sources with output robust enough to power large electrical grids. Nuclear energy offers a current technology that can supply a significant amount of energy and is, apart from construction of the plant, CO2-free. However, the presently used open fuel cycle involving UO2 is both inefficient and creates significant waste, driving an urgent need to bring the nuclear industry into the 21st century. Generation IV reactors, which are projected for use in mid-century, require entirely new fuels and closed cycles.
Consequently, a considerable amount of research and development will be required before they can be made operational. Some materials questions were addressed in the MRS Bulletin on Advanced Nuclear Energy Systems in January 20098 and Harnessing Materials for Energy in April 2008. 9 However, not since September 2001 has basic actinide research been discussed in the MRS Bulletin.10 Since that time, a number of important advances have been made, furthering our understanding of these materials. The present issue highlights some of these new initiatives, illustrating also how actinide research transforms into an understanding of general materials properties and energy. If nuclear power is to be a serious contender as a power source in the 21st century, then the problem of the characterization, treatment, and disposal of nuclear waste must be solved. In the longer term of hundreds of years, the predominant waste from the open fuel cycle will be alpha-emitting actinides, such as Pu, Am, and Cm. Immobilization of these species for geological disposal is usually achieved with mineral-based ceramics because of their reduced risk of accidental criticality and exceptional aqueous durability. However, recent nuclear magnetic resonance results for a Pu-239 zircon show that the material would be completely amorphous after 1400 years,11 where this loss of crystalline structure would degrade storage quality. Hence, other avenues of waste handling should be investigated, such as outlined in the article by Neu et al.
Kevin T. Moore, L
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