Abstract: A nuclear reactor has a core and a pressure vessel with a wall and an interior. A pressure relief responding as a function of temperature is provided in the case of insufficient core cooling (due to a highly improbable failure of the cooling devices and emergency cooling devices). A safety device protecting against overpressure failure of the pressure vessel upon insufficient cooling of the core includes a pressure pipe passing pressure-tightly through the wall and extending into the interior of the pressure vessel. The pressure pipe has at least one pressure compensation opening formed therein in the interior of the pressure vessel and has a fusible sealing body sealing the pressure compensation opening. The fusible sealing body is formed of a melting solder melting at a limit temperature, such as 600.degree. to 700.degree. C., and unblocking the pressure compensation opening, but keeping the pressure compensation opening sealed during normal operation.

Abstract: A nuclear reactor has a pressure vessel with an interior, a coolant conducting surface, such as a wall of the pressure vessel or a line passing through the wall of the pressure vessel, a pressure relief line, and a core. A safety device which protects the pressure vessel against overpressure failure upon inadequate cooling of the core includes a pressure relief valve being pressure-tightly inserted into the coolant conducting surface and having a seat, a closure element normally disposed on the seat for blocking a flow from the interior of the pressure vessel to the pressure relief line, an abutment, and a valve closing spring holding the closure element and being supported against the abutment. A force transmission element holds the abutment and has an end facing away from the abutment. A detent is disposed in the pressure vessel and fixes the end of the force transmission element. The detent is releasable in dependence on a given threshold temperature, for example 700.degree. C.

Abstract: A safety device against overpressure failure of a nuclear reactor pressure vessel in case of inadequate core cooling, includes a pressure relief system responding as a function of temperature. A differential-pressure-loaded pressure relief valve set in a wall or an immediately adjacent pipeline of the pressure vessel which is exposed to primary pressure, has a closure piece that is preferably a differential-pressure piston being mounted so as to be longitudinally displaceable and being sealingly retained in a closure position thereof by a fusible stop. When an upper threshold temperature is reached in the interior of the reactor, which causes the fusible stop to melt due to a threshold temperature heat flow reaching the stop, the differential-pressure piston is moved into an opened position thereof.