Severe Accident Phenomena: A Comparison Among the NuScale SMR, Other Advanced LWR Designs, and Operating LWRs

During a severe accident in a nuclear reactor, there are a number of phenomenological events that can present a challenge to containment integrity. These include the generation and combustion of hydrogen, energetic fuel-coolant interactions, thermal attack of fission product barriers, core-concrete interactions, direct containment heating, and gradual overpressurization. The advanced design of the NuScale small modular reactor (SMR) has resulted in the reduced likelihood and severity of severe accident challenges to containment. This paper discusses the features of the NuScale design that reduce the likelihood of occurrence of these severe accident phenomena and also discusses the ability of containment to survive in the unlikely event that they do occur. The impact of severe accident phenomena for the NuScale design is compared and contrasted against other advanced light water reactors (ALWRs), such as the AP1000 reactor and the Economic Simplified Boiling Water Reactor (ESBWR), as well as the existing fleet, using information from publicly available documents.