The qualification of electrical components and instrumentations relevant to safety

Systems and components relevant to safety of nuclear power plants must maintain their functional integrity in order to assure accident prevention and mitigation. Redundancy is utilized against random failures, nevertheless care must be taken to avoid common failures in redundant components. Main sources of degradation and common cause failures consist in the aging effects and in the changes of environmental conditions which occur during the plant life and the postulated accidents. These causes of degradation are expected to be especially significant for instrumentation and electrical equipment, which can have a primary role in safety systems. The qualification is the methodology by which component safety requirements can be met against the above mentioned causes of degradation. In this report the connection between the possible, plant conditions and the resulting degradation effects on components is preliminarily addressed. A general characterization of the qualification is then presented. Basis, methods and peculiar aspects are discussed and the qualification by testing is taken into special account. Technical and organizational aspects related to a plant qualification program are also focused. The report ends with a look to the most significant research and development activities.