Safety goals in 'risk-informed, performance-based' regulation

The recent overall improvement in key operational safety indices in the United States, combined with 'risk-informed, performance-based' regulation by the US Nuclear Regulatory Commission (NRC), has indicated that 'safety goals' are indispensable; thereby both licensee and regulator can share common objectives and common indicators of safety performance. Recognizing these, the author proposes a new concept of safety goals to facilitate engineering application, while removing some of the uncertainties often encountered in implementing the safety goals, by extending a framework of the International Nuclear Event Scales (INES) being widely used in the world. In this article, safety goals are characterized from a point of view of nuclear regulation by oversight, as established by the US NRC. This is a new tendency of nuclear regulation to motivate initiatives of licensees to improve safety and operational performance and to minimize potential nuclear risks, without the regulatory side specifying how the specific safety requirements should be met. Whereas in the 'compliance-based regulation,' which is a more widely used approach of nuclear regulation in many countries, detailed prescriptive safety requirements are specified to enforce the licensees to strictly follow them. The author observes, through the past experience of the US NRC, the latter approach has a basic limitation in improving total safety of nuclear facilities, and supports the new direction to be taken more widely in the nuclear community