ANS publishes standard to enhance nuclear facility safety
Probabilistic risk assessment evaluates the risk of severe consequences relative to the likelihood of various occurrences. This method assesses the probability of failure, the severity of adverse consequences, and how likely an event is to occur. PRA provides significant benefits as a sophisticated technique for evaluating the performance of complex technical systems to achieve safe plant operation. Quantitative risk assessment for nuclear plants began in the early 1980s.
"In a post-9/11 environment, a PRA regarding external events takes on new visibility. But we recognized in 1999, when we formed the Risk Informed Standards Committee (RISC), the value of such a standard not only to improve safety, but also to gain a better understanding of the differences in nuclear plant designs. This understanding can help us develop better regulation, increase productivity, and apply valuable resources to improve safe plant operation," stated Jim Mallay, Chair, ANS Standards Board.
Since the emergence of PRA as the premier analytical tool to quantify risk, the ANS has excelled in the application of the methodology. Because of this experience, the ANS Standards Committee was able to provide the foundation of expertise needed to develop the systematic evaluation of risk now embodied in ANSI/ANS-58.21-2003. Written by a volunteer working group of professionals, the standard was subjected to a series of expert reviews, culminating in the consensus ballot conducted by RISC in early 2003. This ballot constituted the final approval of the document as an American National Standard.
Precursor documents developed by the ANS, the U.S. Nuclear Regulatory Commission, the U.S. Department of Energy, and the Electric Power Research Institute offered a basis for the development of the "External Events PRA Methodology." Following the American Society of Mechanical Engineers' standard that set forth PRA techniques to analyze internal events, ANSI/ANS-58.21 provides seamless procedures for evaluating internal and external events.
Copies of ANS-58.21-2003 can be purchased from ANS in either print or electronic format.
