Behavior of a Nuclear Steel Containment Equipment Hatch at Large Strain

During a severe accident, buckling of a steel containment hatch door, large deformation and ovaling of the hatch sleeve are potential causes of mismatch at the sealing surface which can result in a leakage path. A three-dimensional nonlinear finite element analysis of a typical steel containment/sleeve/hatch assembly that includes containment stiffeners, pretensioned swing bolts, and hatch door geometric imperfection is presented. The analysis was carried out to the nonlinear range up to large strains. The results indicated that the buckling load occurs at pressure, far above that which causes gross yielding of the shell plate. Although buckling of the hatch door increased the relative motions of the hatch sleeve and the hatch door, the motions remained sufficiently small to prevent leakage.