EQUIPMENT-LEVEL SEISMIC PROTECTIVE SYSTEMS FOR ADVANCED NUCLEAR REACTORS

The seismic load case is a key contributor to the overnight capital cost (OCC) and levelized cost of energy (LCOE) of conventionally constructed nuclear power plants (NPPs). Because design basis earthquake (DBE) shaking is location dependent, no two NPPs at different sites are identical, namely, each NPP is a First-of-a-Kind (FoaK). The seismic isolation of reactor buildings is one pathway to Nth-of-a-Kind (NoaK) construction and possible drastic reductions in both OCC and LCOE. Some proposed advanced reactor buildings are deeply embedded, which may make the cost of building isolation prohibitive. For such buildings, horizontal isolation of individual pieces of safety-class equipment may be a practical and cost-effective solution, and enable NoaK equipment. Surface-mounted advanced reactors could also employ equipment-level seismic protective systems. A MEITNER project, funded by the Advanced Research Projects Agency-Energy, is now underway to provide the technical basis for the implementation of equipment-based seismic protective systems, with the overarching goal of driving down the OCC and LCOE of advanced reactors. This paper presents a pathway to NoaK equipment using equipment-level seismic protective systems. A paradigm shift in design practice is proposed, wherein a piece of safety-class equipment is designed for operational loadings only, its resultant seismic capacity (design space) is established, and that capacity is used to drive the choice of a seismic protective (isolation) system. Such a process focuses on reducing or eliminating the impact of the seismic load case on the functionality and cost of the safety-class asset. The process is demonstrated using a generic high temperature gas reactor (HTGR) building equipped with three safety-class assets: a reactor vessel, a steam generator, and a control rod drive mechanism housing. Designs for the reactor building and the safety-class equipment were developed per ASCE/SEI Standards 4 and 43, ACI 349, and the ASME Boiler and Pressure Vessel code. Numerical models of the reactor building and the safety-class equipment were developed and analyzed for ground motions consistent with DBE shaking at the site of the Idaho National Laboratory (INL). The concept of equipment design space is proposed, which describes the seismic capacity of a piece of equipment or an assembly of equipment, measured in terms of a user-specified combination of stresses, accelerations, velocities, deformations, and displacements. Hypothetical design spaces are proposed for the equipment in the HTGR building. Four seismic protective systems, specific to the building and the INL site, are investigated to identify solutions that fall within the design spaces. One of the four isolation systems was optimal for the chosen building, site, and equipment. Because the impact of the seismic load case is eliminated with the use of the optimal isolation system, equipment designed for operational performance only could be used. Identical equipment could be used at a different site, with the only possible change being an alternate isolation system: the pathway to NoaK equipment.