MAWP for tank shell on Nastran

Hello,


We have a shell component with a shell thickness of 5mm. We are trying to do a buckling analysis. We have constraints placed on the bottom. 50mbar is the input pressure and the self-weight of the roof is 1000kg. the result we got, out of the 8 nodes, we got the highest eigenvalue of -1.3. on further research, for eigenvalues less than -1, it is understood that buckling is not expected. so in conclusion, can we say 50 mbar is the MAWP? Any input would be highly appreciated.