One essential characteristic of reinforcing steel in nuclear installations is how ductile it is and hence how readily the internal forces and moments can be redistributed. This characteristic is an essential factor in deciding how robust structures are. These characteristics are particularly important when it comes to extreme extraordinary actions such as aircraft impact or earthquakes to dissipate the energy involved as desired. Bst 1100 (or aircraft steel) was widely used in the past, but its lack of ductility meant that it ceased to be able to meet these requirements; today, normal reinforcing steel B500B is used which meets the ductility requirements.

Outside structural sections to be used in areas to be designed to withstand aircraft impact (APC or airplane crash shells) generally use sleeve joints as it is assumed that the bond will be lost in the immediate vicinity of the impact.