Risk-informed classification of systems, structures and components

Risk-informed classification is based on utilising information from a risk analysis in a consistent way to select most cost-effective methods to control risk associ-ated with systems, structures and components. An item’s risk significance can be broken in two parts: probability of the failure and the consequence of the failure. Higher value in either will possibly mean a higher risk category, depending on the limit values for each category. Risk is controlled by assigning safety enhancing measures to each risk category. Risk-informed classification can be more efficient in reducing risks than the deterministic safety classification used in nuclear power plants. Nowadays also risk-informed classification is in use. Probabilistic safety assessments have shown that the risk significances of components and systems do not follow the simple assumption that components closer to the reactor have greater safety significance, and that many of the components and systems that in the traditional analysis are assigned to a higher safety class have low risk importance.