3.2.1.1 General notes

Building structures in recent nuclear power plants are now expected to last for 60 years in operation, and even more than 80 years if we include commissioning and shutdown, so ensuring the materials characteristics required over such long periods makes choosing the right materials particularly important.

3.2.1.2 Concrete Normal weight concrete

The concrete strength grades normally used in nuclear installations in Germany are C30/37, and in exceptional cases C35/45, as in site concrete in particular cases. Concrete is normally mixed on site.

It was initially thought to make financial sense to use concrete in strength classes C55/67, because of its high strength, but this has proved to be less robust than expected, for various reasons. High-strength concrete is less ductile: any cracks which occur develop straight through the aggregates, creating relatively smooth crack surfaces. This affects integrity and ‘self-healing’ considerably.