4. Irradiation behavior of structural steels

4.1 Ferritic steel bowl

The vessel forms the second containment barrier and, by virtue of its size, structure and stresses, is a major safety component. Made of ferritic steel, it is a closed cylinder of typical PWR dimensions: diameter ~ 4 m, height ~ 12 m, thickness ~ 20 to 24 cm; total mass 350 to 450 t, with cover. In France, the vessel is made from 16 MnNiMo 05 steel (formerly 16 MND 5), equivalent to American A508 Cl.3 steel. Certain impurities are strictly controlled: P and S (< 80 ppm) for original...