Direct Experimental Evidence for Differing Reactivity Alterations of Minerals following Irradiation: The Case of Calcite and Quartz

摘要

Concrete, a mixture formed by mixing cement, water, and fine and coarsemineral aggregates is used in the construction of nuclear power plants (NPPs),e.g., to construct the reactor cavity concrete that encases the reactorpressure vessel, etc. In such environments, concrete may be exposed toradiation (e.g., neutrons) emanating from the reactor core. Until recently,concrete has been assumed relatively immune to radiation exposure. Directevidence acquired on Ar$^+$-ion irradiated calcite and quartz indicates, on thecontrary, that, such minerals, which constitute aggregates in concrete, may besignificantly altered by irradiation. Specifically, while quartz undergoesdisordering of its atomic structure resulting in a near complete lack ofperiodicity, i.e., similar to glassy silica, calcite only experiences randomrotations, and distortions of its carbonate groups. As a result, irradiatedquartz shows a reduction in density of around 15%, and an increase in chemicalreactivity, described by its dissolution rate, similar to a glassy silica;i.e., an increase of around 3 orders of magnitude. Calcite however, showslittle change in dissolution rates - although its density noted to reduce byaround 9%. These differences are correlated with the nature of bonds in theseminerals, i.e., being dominantly ionic or covalent, and the rigidity of themineral's atomic network that is characterized by the number of topologicalconstraints (n$_c$) that are imposed on the atoms in the network. The outcomesare discussed within the context of the durability of concrete structuralelements formed with calcitic/quartzitic aggregates in nuclear power plants.