EVALUATION OF ASEISMIC INTEGRITY IN HTTR CORE-BOTTOM STRUCTURE .2. VIBRATIONAL CHARACTERISTICS OF KEYED GRAPHITE COMPONENTS

The assembly system consisting of keyed graphite components, which is employed in the core bottom structure of a high temperature engineering test reactor (HTTR), has a nonlinear vibrational characteristic. The vibrational test was carried out to grasp the vibrational characteristics using the element model of the key-keyway structure. The analytical code was developed based on the experimental results. The main conclusions are summarized as follows: (i) the stress distribution around the keyway is independent of whether it is induced under a dynamic or a static state; (ii) the stiffness of the key-keyway structure has the nonlinear characteristics due to contact behavior. The stiffness can be evaluated by contact analysis, taking account of the relative slip and the deformation on the contact surface between key and keyway; (iii) the analytical code employing a nonlinear spring for the key-keyway structure is available to predict the vibrational characteristic of the keyed graphite components.