Abstract Standard approaches to the aseismic design of piping systems and components for power plants — such as the floor spectrum method — are costly and neglect equipment-structure interaction. Such interaction has recently been shown to be severe when the natural frequency of a component is close or equal to one of the natural frequencies of the primary structure — a situation referred to as tuning and one almost certain to occur in a large structural system. A base isolation system is described that has been demonstrated to reduce dramatically the accelerations induced in structures under earthquake motion. A series of further experiments is described in the paper; this experimental work demonstrates that the response of equipment in structures so isolated is also greatly reduced. Thus, sensitive internal equipment can be protected directly from seismic attack; interaction need not to be considered and inelastic analyses need not be performed during the design process. Due to rigid body action of the primary system above the base isolation system, multiple support response spectra design methods are not needed. It is anticipated that the use of base isolation will reduce the cost of the design and construction of power plant components, piping systems, and structures.