To assure that nuclear power plants are built and operated safely, we use a “defense-in-depth” concept consisting of three basic lines of de­fense. The first and most important line is the achievement of superior quality in design, construction, and operation of basic reactor systems so as to ensure a very low probability of malfunctions. The second consists of the accident prevention safety features such as emergency reactor shut­down systems, which are designed into the plant. They are intended to prevent any unlikely malfunctions of the reactor systems from escalating into more serious problems. The third consists of consequence-limiting safety features, such as containment shells, to confine or minimize the es­cape of fission products if they should be released from the fuel and the reactor systems.

In addition to the safety reviews on the industry side, applications for a nuclear power plant license undergo four separate aec reviews: by the separated regulatory staff, by the independent aec Advisory Commit­tee on Reactor Safeguards (acrs), by an Atomic Safety and Licensing Board, and by a Licensing Appeals Board or the Commission itself. Meet­ing the requirements of these successive reviews requires evidence of the most thorough engineering of the reactor and its systems, supported by extensive engineering reviews and analyses.

The aec’s efforts to assure nuclear plant safety go beyond judging the acceptability of individual applications. We conduct extensive safety research and development programs and foster and encourage industry efforts along these lines, aec is currently spending about $35 million a year on such programs. We also contribute in such ways as emphasizing the need for management know-how, fostering the development of indus­try standards, and encouraging the development of trained personnel. These types of actions constitute a positive approach, characterized by thorough planning and advanced preparation, which have contributed significantly to the safe introduction of nuclear power to date.