Domed heads pressure vessels

The containment vessel provides a low leakage, pressure retaining boundary which completely surrounds the primary system boundary. The containment includes a containment vessel (lower part) (to contain leaks from the reactor vessel) and a containment dome (upper part), which is to mitigate the releases due to postulated severe accidents. The upper and lower parts of the containment are connected to each other by a containment ring located at the same elevation as the top of the reactor head. 

The other type of safety device commonly used on the inner vessel is a safety head or rupture disk. In case the relief valve malfunctions, these disks are set to burst at approximately 1.2 times the working pressure. Typical bursting disks are of the simple dome type, which burst due to tensile stresses. Recently, reverse buckling disks, which have the dome oriented toward the pressure, have proven themselves to be a highly cost-effective alternative. An advantage of the reverse buckling disks, in contrast to conventional disks, is that they are ruptured as a result of compressive load and thus are not subject to creep failure. 

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