Seismic Fragility Tests of Motor Operated Valve Assemblies With Safety-Related Function

Abstract

Active valve assemblies in important systems to safety are required to maintain the operability during or following earthquakes. Motor operated valve assemblies have been designed to a validated response capacity 60m/s2 at the actuator in accordance with “JEAG4601-supplement 1991” in Japan. The Regulatory Guide for Reviewing Seismic Design of Nuclear Power Reactor Facilities issued in September 2006 defines Design Basis Earthquake Ground Motion and requires that residual risk for large earthquakes should be considered. It is needed to acquire seismic capacity data for a variety of active valve assemblies. JNES has performed fragility tests for motor operated valves: globe valve, gate valve and butterfly valve. An experimental test program is developed to ensure operating requirements for valve assemblies whose safety-related function is to open, close, or regulate fluid flow, and structural requirements for pressure boundary integrity. A series of vibration tests has been performed using shaking tables at varied acceleration levels up to target acceleration levels by sinusoidal waves. As a result of the vibration tests, the operability of valve assemblies for each type of motor operated valve has been verified at the target acceleration levels. The yoke of a motor operated gate valve connecting the actuator and the valve body was identified to be vulnerable for low cycle fatigue depending on the postulated load conditions in terms of intensity and frequency. The resulting seismic capacity data of actual valves will be applied for a fragility analysis of Seismic PSA.