Seismic Isolation Design for JSFR

Abstract

This paper describes the seismic design of Japan Sodium-Cooled Fast Reactor (JSFR), which includes the seismic condition, the seismic isolation system, and the seismic evaluation of the primary components. Since the design seismic loading is set out severely than ever since The Niigata-ken Chuetsu-oki Earthquake in 2007, an advanced seismic isolation system is aimed to reduce the seismic force loaded on the primary components of JSFR to be less than that of the previous seismic isolation system. The advanced seismic isolation system is developed by optimizing the performance based on the previous seismic isolation system considering the natural frequency of the primary components. The laminated rubber bearings thicker than the previous ones and oil dampers are adopted for the advanced seismic isolation system of SFR. The seismic evaluation of nuclear reactor components applying the advanced seismic isolation system is performed and its feasibility is confirmed.

Recent Advances in Multi-Dimensional Vibration Mitigation Materials and Devices

“…Ou and Jia (2010) validated the effectiveness of a threedimensional isolation bearing consisting of a laminated rubber bearing and a combined coned disc spring with a vertical energy dissipation device, which shows that the 3D seismic isolation bearing is expected to be applied to the medium-to-short span bridges. Okamura et al (2011) evaluated the effectiveness of an advanced seismic isolation system adopting thicker laminated rubber bearings and oil dampers, which confirms the possibility of isolating three-dimensional earthquake motion to protect nuclear power plants by increasing the thickness of the rubber layer of conventional rubber bearings. Yang and Niu (2012) studied the beneficial effect of a new three-dimensional isolation combining SMA strands and the disc spring with laminated rubber bearings, which indicates that the application of SMA causes clear seismic energy dissipation and reduces upper structure deformation in all directions.…”

Design Study and R&D Progress on Japan Sodium-Cooled Fast Reactor

“…This system functions horizontally and consists of a combination of laminated rubbers and oil dampers. 14) While the RV of SFR can be designed as a thin wall configuration thanks to the circumstance of a low-pressure system, a thicker wall is desired for enhancing the toughness of the RV against earthquakes. However, the wall thickness should be limited to a level not to cause a significant impact of thermal stress on the structural integrity of the RV.…”

“…3, i.e., improvement of stiffness by increasing the RV wall thickness and mitigation of the input seismic motion by optimizing natural periods of the seismic isolation system in comparison with those of the reactor system component. 14) As a result, a perspective on the integrity of the reactor system was obtained when the RV wall thickness was 60 mm or more and the seismic isolation system had longer natural periods, i.e., 0.29 Hz of natural frequency in the horizontal direction and 8.0 Hz in the vertical direction. On the other hand, attention should be paid to the influence of thermal stress during thermal transient by the increase in the RV wall thickness.…”

Mechanical behaviour of rubber bearings with low shape factor

“…Yabana et al [15] carried out tests to evaluate the mechanical characteristics and the performance of rubber bearings with a shape factor of 4.2, highlighting the effect of decrease of the rubber thickness, caused by the vertical pressure, on the bearing horizontal stiffness, and the high displacement capacity (shear strains > 500%), which is similar to that of more conventional bearings. Zhou et al [16] and Okamura et al [17] both considered the application of LSF bearings to 3D isolation of modern nuclear facilities. Cilento et al analysed results from an extensive experimental campaign to investigate the effectiveness of isolating a structure with LSF bearings [18].…”