PIUS: Status and perspectives

Nuclear energy represents an important option for future energy supply, but the nuclear option could be jeopardized if severe reactor accidents, such as the ones at Three Mile Island or Chernobyl, were to continue to occur anywhere in the world. The PIUS (Process Inherent Ultimate Safety) reactor development effort is based on the conviction that future developments of nuclear energy for civilian applications should incorporate technologies where safety against severe accidents becomes an inherent feature of the reactor configuration that cannot be compromised by malfunctioning equipment of human intervention. This requirement is being recognized in several industrialized countries where an evaluation of the PIUS concept is underway or planned and should be particularly important in countries contemplating the introduction of nuclear power. The PIUS principle, simply stated, aims for the preservation of core integrity under all reasonably conceivable upset conditions by utilizing reactor configurations in which only processes based entirely on irrefutable natural laws (such as gravity and thermo-hydraulics) are necessary for reactor shutdown and cooling. Maintaining core integrity guarantees the absence of significant releases of radioactivity to the environment and hence results in an insignificant safety risk.