DISTINCT EFFECTS OF IRRADIATION ON THE STRUCTURE AND CHEMICAL REACTIVITY OF SILICATES AND CARBONATES

摘要

Concrete in nuclear power plants (NPP) is subject tosustained exposure to neutron irradiation. The interactionof neutrons with crystalline components of concrete, e.g..,the mineral aggregates, may result in its prematuredegradation by, for example, alkali-silica reactionleading to cracking. In this collection of studies, weinvestigated the effects of irradiation on the structure andreactivity of a wide variety of minerals typical of concreteaggregates. The silicates quartz (SiO_2), albite(NaAlSi_3O_8), and almandine (Fe_3Al_2(SiO_4)_3), and thecarbonates calcite (CaCO_3) and dolomite (CaMg(CO_3)_2)were irradiated using Ar~+ ions at 400 keV. Moleculardynamics simulations enabled the characterization ofnetwork rigidity of pristine and irradiated samples fromthe magnitudes of radial and angular bond excursions.Dissolution rates quantified using vertical scanninginterferometry showed that the minerals underwentvarious degrees of enhancement in reactivity uponirradiation, ranging from nearly unchanged (i.e., calciteand dolomite) to a factor of 1000 (i.e., quartz). Theobserved increase in dissolution rates for a variety ofaqueous environments depended on the nature andmagnitude of the relative decrease in network rigidityupon irradiation, as well on the specific dissolutionmechanism of the phase. The dominance of ionic bondingin carbonates rendered the phase resilient to irradiation,whereas the breakage of Si–O bonds in the percolatedsilicates albite and quartz resulted in structural disorder.In addition, the trends in reactivity alterations areconsistent with the corresponding changes in density.These findings can help guide assessments ofsusceptibility of concrete to irradiation-induced damageand inform selections of durable aggregates.