FINITE ELEMENT ANALYSIS OF NUCLEAR CONTAINMENT SUBJECTED TO MISSILE IMPACT

Abstract

The efficiency of the safety structures like military bunkers and nuclear containments should be checked against missile impact. In the past studies have been carried out to determine penetration depth of missile into targets. Studies are also available, wherein the effect of an explosion on a structure located at some distance has been studied. This study is an attempt to find the response - • of a structure for a penetration of a missile followed by explosion. A 3D finite element modelling of a typical outer containment has been made. Outer containment contains a cylindrical wall covered with a dome slab. In order to analyze a dynamic problem, it is required to have material model which includes the dynamic behaviour of the material. To include the dynamic behaviour in concrete damage plasticity model, strain rate effect has been incorporated in the model. The stress-strain curves at varying strain rates have been employed in damaged plasticity model and the response of structure at varying strain rates has been studied. It has been observed that there is nearly 40% decrement in the missile penetration depth with strain rate dependent model as compared to that of strain rate independent model. In order to calculate the blast load on the structure due to missile, firstly, penetration study has been conducted on the two critical positions of containment i.e., position 1 near the . junction of cylinder and dome and position 2 at the middle portion of the cylindrical wall. For the velocity of 200 m/s, containment has been penetrated completely by the missile. Containment is just safe for the penetration of missile of 200 m/s, therefore, it cannot sustain the effect of blast loading. For 100 m/s velocity however the missile penetration was found to be 0.3 m. Therefore, blast analysis has been carried out only for 100 m/s velocity. Fundamental protective design for conventional weapons (U.S. Army cops code) has been used in order to calculate the blast loading. In order to find out the Optimum TNT content that can been sustained by the containment, parametriC study has been carried out by finding the response of containment for 50, 30 and 10 kg TNT content has been studied. Finally, it has been concluded that the results are very sensitive to explosive content and the safe explosive content is 10 kg of TNT.