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Numerical models capable of generating robust estimates of isolation-system and fluid-structure responses for multidirectional, high-intensity shaking will be required for analysis, design, and risk assessment of seismically isolated advanced reactors. None of the few studies to date on base-isolated, fluid-filled vessels have generated datasets suitable for formal validation of numerical models. Earthquake-simulator experiments on a fluid-filled, cylindrical vessel, base isolated using four single concave friction pendulum bearings (SFP isolators) were performed. The dataset was used to validate a numerical model for high intensity, multidirectional seismic inputs. Fluid and isolation-system responses obtained from analysis of the numerical model were in excellent agreement with experimental results. The numerical models and outcomes from the experiments are broadly applicable to base-isolated, fluid-filled vessels, regardless of industry sector.

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The nuclear industry is currently at a severe economic disadvantage, mainly due to the extremely large capital costs involved constructing in new nuclear power plants. Recent nuclear constructions have seen large cost overruns and schedule delays, making the nuclear sector less attractive to investors. Advanced reactor concepts currently under development in the United States are striving to improve the economics of nuclear power primarily by using passive and 'walk-away' safe technologies. The recently published report, 'Future of Nuclear Energy in a Carbon-Constrained World' (Buongiorno et al., 2018) by the Massachusetts Institute of Technology Energy Institute (MIT EI) has shown that a significant contributor to the capital cost of NPPs is the 'civil works' i.e., the construction of the balance of plant (BoP: all SSCs except those involved in power generation, e.g., reactor vessel) such as the buildings, containment dome, foundation, etc., which amount to almost half of the overnight capital cost. It also suggests that using advanced construction technologies such as seismic isolation and high-performance concrete to significantly reduce the capital costs of advanced reactors. It is therefore imperative that innovations in advanced reactors are not only in the reactor technology, but also in the design, procurement, and construction of the balance of plant and in the civil works. This report demonstrates the application of two cost-cutting solutions on generic advanced reactor designs. These solutions include, (1) seismic base isolation, and (2) risk-and cost-based seismic design optimization including seismic isolation of individual components. Capital cost (USD millions) Seismic risk Initial, unoptimized, and not seismically isolated 99.20 5.16 x 10-5 Optimized, without including component seismic isolation 83.22 4.92 x 10-5 Optimized, including component seismic isolation 78.61 4.86 x 10-5

An innovative seismic isolation solution for designers of safety-class equipment in advanced nuclear power plants is introduced. The test specimen was a tall, slender, carbon steel vessel that could represent a reactor vessel, steam generator, or a heat exchanger in a nuclear power plant: 240 inches tall, outer diameter of 60 inches, and wall thickness of 1 inch. The vessel was supported by three radial mounts at its mid-height, near its center of gravity, on a steel frame. The vessel was subjected to three-component ground motions using a 6DOF earthquake simulator. The specimen was filled with water for testing to indirectly account for the fluid and internal equipment present inside a prototype vessel. Three configurations were tested: non-isolated, isolated using single Friction Pendulum (SFP) bearings, and isolated using triple Friction Pendulum (TFP) bearings. The test results demonstrate that mid-height seismic isolation is practical and enables a significant reduction in horizontal spectral accelerations. These outcomes are not specific to the spherical sliding bearings used in the experiments but are broadly applicable to mid-height, seismically isolated equipment. K E Y W O R D Searthquake-simulator experiments, equipment isolation, mid-height seismic isolation, nuclear power plants, safety-class equipment INTRODUCTIONSeismic isolation has been applied to more than 10,000 structures worldwide, including hospitals, data centers, buildings of cultural importance, bridges, emergency operations facilities, offshore oil and gas platforms, port facilities, container cranes, and electrical substations and power distribution systems. The benefits of seismically base isolating nuclear power plants (NPPs), in terms of reduced seismic demands and risk, are well established 1-8 but the technology is yet to be applied to an NPP (or a nuclear facility) in the United States. Parenthetically, seismic isolation is being considered as an integral design feature in some US advanced nuclear reactors, with the twin goals of steep reductions in capital cost and standardization of reactor designs. 9,10 Outside the U.S., two NPPs, in Cruas, France and Koeberg, South Africa, were base isolated in the early 1980s to enable the re-use of a certified plant design developed for a site of lower seismic hazard. Seismic isolation has also been implemented in the International Thermonuclear Experimental Reactor (ITER), the Jules Horowitz Reactor (JHR), the La Hague spent fuel storage pool, and the Georges Besse II uranium enrichment facility, all in France, with ITER and JHR under construction at the 998