The Nuclear Safety Directive of the European Union, as amended in 2014, demands that new nuclear installations be designed with the objective of preventing accidents and, should an accident occur, mitigating its consequences and avoiding early radioactive releases and large radioactive releases. Principle 1 in the Vienna Declaration on Nuclear Safety formulates the same objective for new nuclear power plants.
This report provides a common understanding of the approach to demonstrate the avoidance of early releases and large releases by using the notion of practical elimination. This notion is widely used in this context, inter alia by WENRA and IAEA. The report applies to new nuclear power plants. It deals exclusively with nuclear safety aspects. Existing plants and other nuclear installations, as well as security aspects, are outside its scope.
There are various kinds of scenarios to which the notion of practical elimination can be applied. In order to get an overview over all relevant cases, it is useful to classify the scenarios into three types:
Type I -- scenarios with an initiating event that leads directly to severe fuel damage and early failure of the confinement function.
Type II -- severe accident scenarios with phenomena that induce early failure of the confinement function.
Type III -- severe accident scenarios that result in late failure of the confinement function.
All WENRA countries apply the notion of practical elimination to types I and II; some countries also apply it to type III.