Nuclear containment wall under aircraft crash

Abstract

The safety analysis of important structure such as nuclear power plant against commercial aircraft has been studied. In the present study, a stepwise sequential analysis has been performed to determine the stresses on the nuclear containment wall under aircraft crash and induced fire effects. ABAQUS/Implicit finite element code was followed to get the response of the nuclear containment. First, the impact load is applied on the containment using Riera force history curve of Boeing 707-320, after 0.16 sec nodal temperatures were increased following the proposed jet fuel curve to imitate fire as a result of fuel burning. Combined effect of impact and heat has been used to study thermal stress variation. As the fuel is stored in the wings of the plane, the effect of fire is assumed to trigger as soon as the wings hit the outer face of containment wall. From Riera force history curve, time delay between plane’s first contact and wing contact with the containment wall was assumed to be 0.16 second. The effect due to fire was considered to be most severe at 10 m height from the base of containment structure. This is due to the fact that post-impact most of the fuel will immediately flow down to the bottom of containment. In the impact region, moderate fire for 15 minutes has been considered. The fire duration has been considered for 2 hrs at severe zone. The deformed geometry of model in impact analysis is then assumed to be the initial state for the thermal stress analysis. The concrete damaged plasticity model for concrete and Johnson-Cook elastic-visco plastic material model for reinforcement have been taken to predict the behavior of concrete and steel. For heat transfer and thermal stress analysis, the material properties have been taken at elevated temperature form Eurocode 2. The containment has a circular cylindrical wall of inner diameter 42 m and thickness 0.85m excluding 6mm steel plate which was provided at the inner face of containment. The total height of the containment was assumed to be 60 m. The impact location of the aircraft was considered at the mid-height of the containment as more deformation was observed in this location.