4.71. Localized stress distributions, including those at welding sites, and their effects on the mechanical performance of structures, including leak rates, should be evaluated.

4.72. For prestressed concrete containments, particular attention should be paid to identifying areas of low prestressing (such as areas surrounding large penetrations and transition zones between cylinder and basemat), so that measures can be taken to avoid fractures and leakage due to concrete creep and shrinkage. In these critical areas, if the containment has no internal liner, leaktightness should be ensured by means of a local coating, local injection of sealing products or other appropriate methods.

4.73. For containments provided with a metallic liner, the zones of anchorage of the liner to the concrete and the connections of the liner to other metallic structures such as penetrations are also critical areas. Local effects of stress in these zones should be analysed and taken into account.

4.74. The assessment of the susceptibility of structures to fatigue should be made on the basis of a complete evaluation of the stresses and cycling, including pressure cycling for testing, temperature cycling and pipe reactions.