ASTEC V1.3rev2 Code Application

During a hypothetical severe accident in a nuclear reactor most of the radioactivity would be released from the damaged core and the broken primary circuit in form of aerosols and chemical vapours and gases. However the radio-toxicity of released materials depends both on the released mass and on the chemical form as well. The fission products release and transport in the circuit has been analysed for a Medium Break cold leg Loss Of Coolant Accident (MBLOCA) for a reference PWR 1000 reactor using the severe accident integral code ASTECV1.2 rev2. A detailed description of the reactor model is given. Sensitivity analyses were performed in terms of break location and accumulator availability. The break location has an impact on the carrier gas temperature and in turn on the chemical speciation of the fission products. Also retention is influenced by the different flow pathways establishing in the circuit. The accumulator availability extends the duration of the core degradation process affecting the total production of hydrogen and the cumulated released mass of low, semi and highly volatile fission products.