DIN 25459 applies to reinforced and prestressed concrete containment for nuclear power plants. This containment is the structural part of the confinement from the nuclear power plant. The safety function to be fulled by the confinement consists in ensuring that in the load cases specified the leak tightness remains at a level at wich, particulary under incedent conditions, the specified leakage rates are not exceeded. The supplement deals with questions to several clauses of DIN 25459 and gives explanations.