In what follows, we will present some other particular features of construction which are particularly characteristic of building nuclear power plants.

3.2.4.1 Reactor building — containment

The pre-stressed concrete containment in the OL3 reactor building is made of K60 concrete to Finnish standard BY50 (comparable with C50/60) with a steel liner. The cylindrical section has walls 1.3 m thick. The inner steel liner, made of S355J2SN steel, is 6 mm thick. The pressure vessel has an internal radius of 23.40 m and an outer radius of 24.70 m.

To make the cylindrical section of the steel liner, 90° sections 6 m high were delivered to the site. These sections were then assembled to form rings 12 m high and were lifted into place (Figures 4.19-4.21).

Before being lifted into place, segments were coated with epoxy resin based triple-layer paintwork (basecoat, intermediate coat and topcoat).

Once each liner segment was lifted into place, it was welded to the segment below it. Once it was welded, the reinforcement and tendon sleeve tubes were installed. Tensioning blocks for the horizontal tendons of the containment were spaced 120° apart.

Vertical reinforcement joints were made using overlapping or Lenton screwed sockets. The horizontal reinforcement joints were made mostly with overlaps. The connecting reinforcement for the anchor plates integrated in the steel liner (such as polar crane consoles) was made with back closed stirrups, tying the anchor plates to the stirrups with position sockets.

The cylindrical section of the safety containment was shuttered using single-headed self-climbing formwork. The formwork was supported against the structure of the preceding outer containment (APC shell).

One particular structural engineering feature of pressurised water reactors made in Germany is installing the lower steel cap of the steel containment.

The lower section of the spherical steel containment was first made supported on trestles in the spherical concrete segment, so it could be welded on both sides. It was then lowered floating into its final position defined by spacers. Lastly, the cavity remaining was then carefully filled with injection mortar (Figure 4.22).