[en] This report describes tests of elastomeric seals that are used in the mechanical penetrations of nuclear power plant containments. These tests assessed the effects of thermal aging, radiation and thermal aging, sealing surface separation, and squeeze on the performance of several gasket designs: O-ring, gum drop, double dog ear, and tongue and groove. Both ethylene propylene rubber and silicone rubber gaskets were tested. The environment for testing enveloped a hypothetical severe seals is quantified in terms of the leakage onset point on the time-temperature curve