4.203. Metallic materials used for containment systems, including welds, should be of high quality; qualified and certified materials that meet national safety standards should be used.

4.204. In the selection of metallic materials, the following considerations should be taken into account:

— Thermal and mechanical loads;

— Chemical interactions, including those with chemicals used in containment spray systems;

— Resistance to brittle fracture;

— Resistance to corrosion.

4.205. Metallic materials such as zinc and aluminium that have the potential to generate hydrogen on contact with water or steam should not be used inside the containment. If such materials are essential to the design, their use should be limited and the effects of hydrogen generation should be analysed.