Aircraft Impact Considerations for NuScale SMR Plant Design

All new nuclear power plants to be constructed and operated in the United States must meet regulatory requirements for aircraft impact from a large commercial aircraft under 10CFR50.150. Under the regulation, the applicant, using realistic analyses, must identify and incorporate into the design those design features and functional capabilities to show that, with reduced use of operator actions, 1) either the primary containment system remains intact or the reactor core remains cooled, and 2) either spent fuel cooling or spent fuel pool integrity is maintained. Small modular reactors have both advantages and disadvantages over conventional large plant designs in this regard. Small modular reactors generally have smaller footprints and can be configured where the reactor vessels and containment systems are entirely below grade. This minimizes the exposed structure that houses the reactors and spent fuel pool, which generally means that the structural configuration can be more efficiently hardened to resist the impact forces without excessive costs. However, the smaller footprint also means that transmission of shock through the structure can affect more safety equipment than in the larger conventional plant where the safety related equipment for the divisions are physically farther apart. Modular designs by nature tend to have all associated safety equipment together for each reactor module. Larger plants may be more tolerant for allowing internal damage and controlling ensuing fire due to perforation of aircraft wreckage at some strike locations, whereas the smaller footprints for small modular reactors could mean more systems are at risk if the reactor building is not hardened to prevent perforation. This paper presents design considerations employed for the NuScale 12 Module Power Plant in regards to aircraft impact requirements.