Suspended nuclear reactor containments with reduced thermal stress

A containment for a nuclear reactor has a primary vessel for containing the reactor core and liquid coolant. The primary vessel is suspended by its rim from the roof of the containment structure. To reduce thermal stress at the suspension joint, cooling means is provided for the upper peripheral regions of the primary vessel. The cooling means comprises an annular tank containing liquid metal and heat-exchange coils, thermal insulation of varying thickness and a cooling jacket for the thermal insulation.