Protecting Safety-Related SSCs at Nuclear Power Plants from Tornado Debris Impact

In responding to the United States (U.S.) Nuclear Regulatory Commission’s Order EA-12-049 Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond- Design-Basis External Events, many of the operating nuclear power plants have identified a need to evaluate the robustness of certain on-site, liquid-contained storage tanks. Evaluations must address the effects of wind-driven missile impact on storage tank structural integrity and inventory security.

In his technical paper Computational Evaluation and Mitigation of Wind-Driven Missile Impact against Condensate Storage Tanks and Associated Piping Connections, Protection Engineering Consultants (PEC) Project Engineer, Dr. Eric Sammarco describes one such evaluation for two condensate storage tanks (CSTs) and associated piping connections at an East Coast U.S. nuclear power plant (Plant). The evaluation was led by Nexus Engineering—a multi-disciplinary A/E firm specializing in engineering solutions for severe accident management. PEC served as a specialty consultant, providing high-fidelity computational modeling and structural engineering support.

The impact of a wind-driven missile against a thin-walled, liquid-contained structure gives rise to a complex and transient engineering problem involving highly localized stresses, nonlinear constitutive behavior, material damage/failure, and fluid-structure interaction. The multi-physics finite element code LS-DYNA was used to carry out a rigorous computational assessment involving a spectrum of design-basis tornado missile threats. Based on results from the assessment, it was concluded that a barrier mitigation strategy would need to be employed on site. Eric’s paper describes the computational modeling approach utilized during the missile impact assessment and discusses results from the nonlinear dynamic finite element simulations. In addition, the concept and design of a novel perforated barrier system comprising high-strength steel ring-net panels is presented.

Eric presented this paper at the SMiRT 23 conference in Manchester, United Kingdom, August 10-14, 2015. The full paper is available here.