4.78. Consideration should be given to the possibility of large releases of mass and energy, and the need for the internal structures to withstand the pressure differentials that could arise between different compartments so as to prevent any collapse. For each compartment, the most unfavourable location for a break should be considered. Openings between compartments should be considered by means of a conservative approach at the design stage and should be verified to be free of unintended obstructions after construction has been completed.

4.79. Consideration should be given to the need for the internal structures to withstand the loadings associated with design basis accidents, and so to withstand the hydrodynamic loads that are caused by water flowing from the discharge line of the safety valves and the relief valves into the suppression pool, the swelling of the pool water, the oscillation of condensate water, chugging and any other relevant hydraulic phenomena.