Abstract
Concrete, used in the construction of nuclear power plants (NPPs), may be exposed to radiation
emanating from the reactor core. Until recently, concrete has been assumed immune to radiation
exposure. Direct evidence acquired on Ar+
-ion irradiated calcite and quartz indicates, on the contrary,
that, such minerals, which constitute aggregates in concrete, may be significantly altered by irradiation.
More specifically, while quartz undergoes disordering of its atomic structure resulting in a near
complete lack of periodicity, calcite only experiences random rotations, and distortions of its carbonate
groups. As a result, irradiated quartz shows a reduction in density of around 15%, and an increase in
chemical reactivity, described by its dissolution rate, similar to a glassy silica. Calcite however, shows
little change in dissolution rate - although its density noted to reduce by ≈9%. These differences are
correlated with the nature of bonds in these minerals, i.e., being dominantly ionic or covalent, and the
rigidity of the mineral's atomic network that is characterized by the number of topological constraints
(nc) that are imposed on the atoms in the network. The outcomes have major implications on the
durability of concrete structural elements formed with calcitic or quartzitic aggregates in nuclear power
plants.
