Fuel behavior under reactivity initiated accident (RIA) conditions in light water reactors are being investigated at the Nuclear Safety Research Reactor (NSRR) in Japan. The capsule containing a fuel rod should be designed so that it could endure the impulsive loads and could be as thin as possible, to avoid losing the neutron economy simultaneously. So the dynamic capsule experiments have been conducted for investigating pressure wave propagation, water hammer and deformation response using explosive as a source. And analytical approach was contrived to reproduce the fluid-structural dynamic response. High tensile tests were carried out for the capsule material and the expression way of dynamic constitution law so as to reproduce the flow stress change due to strain and strain rate. The dynamic plastic deformation behavior of the capsule could be reproduced by this method.