The response of a typical steel‐lined reinforced concrete nuclear reactor containment to uniform internal pressure monotonically increasing to failure is analyzed by nonlinear Finite Elements. Emphasis is placed on modeling the in‐place random variation of the properties of reinforcing bars and of the strength of mechanical splices. This natural variability is taken into account in approximation, through the use of “effective” stress‐strain laws of ensembles of mechanically spliced bars, developed by simulation on the basis of certain mechanical assumptions. It is found that due to progressive ruptures of bars and splices, the containment ultimate capacity is much smaller than that predicted on the basis of the ductility of reinforcement with uniform, average properties and with splices that do not fail prior to the bars, and is close to thepressure causing generalized yielding of the reinforcement.