Fast breeder reactor building, severe accident loading and ultimate capacity

Abstract

The accident loading of the SNR-300 containment is different from that of an LWR due to the different containment concept, • - sodium as coolant, which can cause energetic reactions • - additional design measures against loads resulting from an HCDA Accidental release of sodium, radioactive materials and/or decay heat result in pressure and temperature rise in the containment. Due to the temperature rise of the concrete structures stress and deformation analysis is often necessary. Heated concrete releases water or steam which has to be separated from the Na-leakage by a steel lining and by a relief system to avoid chemical reactions with additional energy and gas release. The additional assumption of safety system failures as the core catcher, the steel lining, the reventing system, the energy supply, the barriers between inner and outer containment alone or still in combination for risk analysis can lead to physical and chemical phenomena as sodium fires, water release from heated concrete, sodium—water reactions, sodium boiling, core concrete interactions or sodium—concrete interactions. An acceptable best estimate evaluation of the resulting loads and consequences can only be realized by application of computer codes as CONTAIN or CACECO, which mostly respect the coupling of all involved phenomena.