The benefits of seismically isolating nuclear power plant buildings, in terms of reducing seismic risk, are well established but the possible impacts on overnight capital cost are unknown. Projects funded by EPRI and ARPA-E are now underway to characterize possible reductions in overnight capital cost of new build plants, with a focus on the financial impact of the seismic load case. The EPRI-funded study is addressing the base isolation of reactor buildings and the ARPA-E MEITNER project is assessing the use of equipment-based seismic protective systems in advanced reactors.

Two generic reactor buildings were designed to provide data on equipment weights and lateral accelerations as a function of incremented levels of earthquake shaking. One building houses a molten chloride fast reactor and the other a high-temperature gas reactor. Each building was populated with three pieces of equipment: a reactor vessel, a steam generator and a housing for a control rod drive mechanism. Response-history analysis was performed using earthquake ground motions consistent with the seismic hazard at the Idaho National Laboratory site, in Idaho Falls, ID. The minimum required wall thicknesses for the reactor vessels and steam generators in these buildings, for operational and incremented earthquake loads, are reported. Lateral accelerations, which are used for the seismic design of the internals in these vessels and for the control rod drive mechanisms, are presented for incremented peak ground shaking of the buildings. The benefits of base isolating the two buildings, in terms of reduced thickness of vessel walls and horizontal accelerations of vessel internals and control rod drive mechanisms are identified. A questionnaire, which seeks to characterize the increase in total cost (i.e., analysis, design, qualification, and fabrication) of equipment for incremented levels of earthquake shaking, is summarized. The questionnaire will be transmitted to consultants, equipment fabricators and suppliers, nuclear steam system suppliers, and operators of commercial nuclear reactors. The responses to the questionnaire and follow-on studies will be presented at SMiRT26.

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