Operational reviews by independent staff (for example, WANO reviews) are conducted to provide station management with an evaluation con­ducted by independent and experienced professionals. In addition, both national regulatory agencies and the IAEA are available to conduct reviews to ensure that correct operating procedures, training, and maintenance procedures are being followed.

Over the extended operating life of any given plant, new facts may come to light that were unknown at the time of first station operation. When these reviews reveal that some new knowledge has come to light that challenges the overall safety basis of the plant, it may be necessary to install corrective measures or equipment to establish adequate defences.