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Date, Hidefumi*; Futakawa, Masatoshi; Ishikura, Shuichi*
Jikken Rikigaku, 2(2), p.103 - 108, 2002/06
In order to examine the impact behavior of mercury, which is one of important key-issues in a facility for high intensity neutron sources, the falling and colliding profiles of mercury droplets were recorded by high-speed video recorder. The impact force was also measured using the strain gage glued on an elastic bar. The falling mercury droplet oscillated between a prolate spheroid and an oblate one, repeatedly. The regathering and jumping of mercury at the collision point on the impact face of the target were observed after impact because of the strong surface tension of mercury. The impact force of mercury droplet was in proportion to the impact velocities and the square root of the potential energy. Scince the non-dimensional duration time K that obtained experimentally is independent of the impact velocity and the size of the droplet, the mean applied stress due to the mercury droplet against the target is easily predictable by the equatiion using K value and the impact velocity is known.
Iwasaki, Akihisa*; Sawa, Naoki*; Matsubara, Shinichiro*; Kitamura, Seiji; Okamura, Shigeki*
no journal, ,
A fast reactor core consists of several hundred core elements, which are hexagonal flexible beams embedded at the lower support plate in a hexagonal arrangement, separated by small gaps, and immersed in a fluid. Core elements have no support for vertical fixing in order to avoid the influence of thermal expansion and swelling. These days, in Japan, larger earthquake vibrations are postulated in seismic evaluations. So, it is necessary to consider vertical displacements (rising) and horizontal displacements of the core elements simultaneously because vertical seismic vibrations are larger than the acceleration of gravity. The 3D vibration behavior is affected by the fluid force of the ambient coolant and contact with the surrounding core elements. In this study, single-model vibration tests using a full-scale test model were conducted, and the basic characteristics of 3D vibration behavior of the core element were examined. In addition, structures restricting vertical displacements (dashpot structure) were devised, and their effectiveness was verified. As a result of the tests, the effects of the ambient condition (in air, in static water, and in flowing water), gap between the pads, vibration directions, vibration waves, and dashpot structures on the vibration behavior of the core element were examined. As regards the ambient condition, the vertical displacements were larger in flowing water that simulates the coolant flow than in air and in static water, because of upward fluid force in flowing water. As regards the gap between the pads, the larger the gaps was, the stronger the interferences due to horizontal displacements, and the smaller the vertical displacements were. The dashpot structure was verified to be suitable for reducing vertical displacements.
