Determination of initiating events and sequences of reactor accidents by a barrier analysis

From a barrier analysis (fuel cladding, primary circuit, containment), a systematic search for the potential initiating events and the accident sequences is conducted. The method is divided into three parts: (1) The barrier analysis: For each barrier, an event tree is constructed having for top event the barrier loss. (2) The search for initiating events of accidents (an accident has occurred when all the barriers are broken or failed). (3) Accidents events trees: From an initiating event, the accident sequence is derived. To illustrate the method, the failure of all the electrical power supplies in a 900 MW PWR is considered. Possible extensions of the method to other risks are suggested