ALIBABA: a French expert system for PWR containment analysis in case of severe accidents.
F. Martin, Severe accident managment - OECD workshop on operator training and instrumentation capabilities, 12-14/03/2001, Lyon (France).
In the event of an accident occurring in a French pressurized water reactor (PWR), the
authorities should be in position to implement the measures required to protect the surrounding population and the environment from radiological consequences of potential releases. The Institute for Nuclear Safety and Protection is part of the national emergency organization established for this purpose. It provides technical support to the French nuclear safety authority.
2. irsn’s methodology
As a technical adviser, irsn has defined a methodology intended to help assess the
plant status and monitor its development as soon as the accident is detected. On the basis of this assessment, the method forecasts the potential behavior of the installation and estimates the related consequences.
The state of the installation is evaluated throughout the accident with special reference
to the three barriers stretched out between the radioisotopes and the environment (fuel cladding, reactor coolant system and the containment building). It considers successively their physical state, the state of the safety functions guaranteeing their integrity and finally the state of the systems available to monitor these functions.
In order to properly diagnose and predict the state of the barriers, evaluations are
necessary to quantify parameters such as the break size on the reactor coolant system, the time to core uncovering and the core degradation. As a result, fission products behavior inside the installation and releases outside the plant are assessed. Several flexible, rapid and user-friendly software tools, which are part of the French SESAME 1 system, have been developed to help the experts with their assessment.
The expert system ALIBABA 2 is separate from these tools. It provides complementary
qualitative information about the third barrier. Indeed, the ongoing or potential releases of fission