Empirical Formulas for the Design of Reinforced Concrete Nuclear Power Plants to Resist the Effects of Wind-Borne Missile Impact: A Critical Review

The U.S. Nuclear Regulatory Commission’s (NRC’s) NUREG-0800, “Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition—Design of Structures, Components, Equipment, and Systems,” and the U.S. Department of Energy’s (DOE’s) DOE-STD-1020-2016, “Natural Phenomena Hazards Analysis and Design Criteria for DOE Facilities,” provide guidance for the design of exterior reinforced concrete roof and wall panels against wind-borne missile impact. These documents point to Regulatory Guide (RG) 1.76, “Design-Basis Tornado and Tornado Missiles for Nuclear Power Plants”; RG 1.221, “Design-Basis Hurricane and Hurricane Missiles for Nuclear Power Plants”; and ANSI/ANS-2.3-2011(R2016), “Estimating Tornado, Hurricane, and Extreme Straight Line Wind Characteristics at Nuclear Facility Sites,” for the definition of missiles and impact velocities. Empirical formulas are used to calculate local responses of reinforced concrete walls and slabs impacted by missiles, where these formulas were calibrated using test data that are no longer available for reinterpretation. This critical review analyzes the accuracy of these empirical formulas using data collected from impact tests conducted by the Electric Power Research Institute and Calspan Corporation in the 1970s. Schedule 40 pipes are used as the impacting missile for this review because it is referenced in both NRC and DOE guidance. Outer and effective diameters of the pipe are used to compare empirical predictions and experimental results. None of the empirical relationships predict the local response of reinforced concrete walls and slabs impacted by tornado- and hurricane-borne missiles with the level of accuracy expected for analysis of a nuclear power plant. More accurate design equations are needed, which could be developed by impact analysis of reinforced concrete panels using numerical models that have been rigorously validated using test data. New experiments will be needed to enable validation of numerical models.