Beyond-Design-Basis Hazards Assessment and Mitigation at Nuclear Power Plants

Many of the nation’s operating nuclear power plants (NPPs) have identified a need to evaluate the robustness of certain structures, systems and components (SSC) deemed critical to plant safe shutdown. This need is driven by requirements from the U.S. Nuclear Regulatory Commission’s (NRC) Order EA-12-049 Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events. Protection Engineering Consultants supports NPP owners, operators and consultants with evaluations and analysis to identify vulnerabilities and mitigation strategies for extreme external hazards.  That support includes regulatory guidance, assessment, structural engineering, and high-fidelity computational modeling services.

Extreme loading associated with a severe tornado event has proved exceptionally challenging to address during some of these risk-based evaluations. Load effects from a severe tornado include demanding velocity pressures derived from 200-mph to 300-mph maximum wind speeds, differential pressure drops on the order of 1-psi to 3-psi, and windborne debris impact—often referred to as tornado missiles. Some examples of licensing basis tornado missiles include 4,000-lb automobiles traveling at 100-mph, 1,500-lb wooden utility poles traveling at 130-mph, 300-lb steel pipes traveling at 100-mph, and 500-lb sections of bolted wood decking traveling at 200-mph. Needless to say, quantifying the vulnerability of critical SSCs to tornado load effects and devising efficient and cost-effective mitigation measures when needed can be daunting and complex tasks.

Our team-oriented approach to problem solving is infused with quality work, responsiveness, and ingenuity. Our knowledge of impact dynamics and material damage mechanics runs deep, and we’re intimately familiar with both the effectiveness and limitations of the classical empirical methods of evaluating tornado missile penetrability. We have successfully employed state-of-the-art computational modeling techniques to evaluate unique tornado missiles/SSCs and novel barrier systems. Past experience has shown (more than once) that innovative thinking and a relatively small additional cost in advanced analysis methods can ultimately yield tremendous cost-savings to utilities and other stakeholders.  See Sammarco et al. SMiRT 23 proceedings in the Tech Notes section of our website.

For more information on our nuclear power services, please contact Dr. Eric Sammarco. We’d love an opportunity to deliver value, innovation and enhanced safety to your plant, project, or nuclear power research effort!