A buckling analysis was performed on an elevated temperature stainless steel vessel subjected to a vacuum loading. Both instantaneous (linear and nonlinear) buckling and creep buckling were investigated. The analysis was performed using ANSYS finite element software, using linear shell elements (Shell 181) with creep capability. The analysis showed that the vessel maintained a significant safety margin against buckling under a vacuum load, at 1200 degrees F for short periods of time, with up to 1 percent out-of-roundness (measured after post weld heat treatment). The analysis also showed that the nozzle loads on the vessels had negligible effect on the governing buckling modes.