Risk-Informed Safety Margin Characterization
Background
Safety is central to the design, licensing, operation, and economics of nuclear power plants. Plant designers commonly over-design portions of nuclear power plants and provide robustness in the form of redundant and diverse engineered safety features to ensure that, even in the case of well-beyond design basis scenarios, public health and safety will be protected with a very high degree of assurance. This form of defense-in-depth is a reasoned response to uncertainties and is often referred to generically as ”safety margin.” Historically, specific safety margin provisions have been formulated, primarily based on ”engineering judgment.”
The ability to better characterize and quantify safety margin holds the key to improved decision making about light water reactor design, operation, and plant life extension. In a sense, contemplation of light water reactor operation beyond 60 years does represent a kind of "beyond design basis operation". A systematic approach to characterization of safety margins represents a vital input to the licensee and regulatory analysis and decision making that will be involved. In addition, as research and development in the LWRS Program and other collaborative efforts yield new data and improved scientific understanding of physical processes that govern the aging and degradation of plant systems, structures, and components (and concurrently support technological advances in nuclear reactor fuels and plant instrumentation, information, and control systems) needs and opportunities to better optimize plant safety and performance will become known.
Purpose
The purpose of the Risk-Informed Safety Margin Characterization Pathway is to develop and deploy approaches to support the management of uncertainty in safety margins quantification to improve decision making for nuclear power plants.
Vision
Management of uncertainty implies the ability to (a) understand and (b) control risks related to safety. Consequently, the Risk-Informed Safety Margin Characterization Pathway is dedicated to improving both aspects of safety management.
One outcome of a risk-informed approach advocated in the Risk-Informed Safety Margin Characterization Pathway is the use of performance-based controls. These controls will be informed by the risk assessment and will focus on desired, measurable outcomes, rather than prescriptive processes, techniques, or procedures, with the aim of identifying performance measures that ensure an adequate safety margin. In addition to the activities identified in this pathway, Risk-Informed Safety Margin Characterization will be working with the Materials Aging and Degradation, Advanced Light Water Reactor Nuclear Fuels, and the Advanced Instrumentation, Information, and Control Systems Technologies Pathways to introduce Risk-Informed Safety Margin Characterization-thinking into each pathway.
