adj. Describes a device, particularly a nuclear power plant, that will shut down or fail safely even if its operators must evacuate the scene.
The next generation of plants must be built to work with nature—and human nature—rather than against them. They must be safe by design, so that even if every possible thing goes wrong, the outcome will stop short of disaster. In the language of the nuclear industry, they must be "walkaway safe," meaning that even if all power is lost and the coolant leaks and the operators flee the scene, there will be no meltdown of the core, no fire in the spent fuel rods, and no bursts of radioactive steam into the atmosphere.
New designs operate on the simple-is-better principle, with the idea of making them "walkaway safe." That means plants shut themselves down safely in an emergency even if their power is cut and their human operators are forced to evacuate.
The reactor power supply is a "walkaway safe" device. In any conceivable accident scenario the need for operator intervention Is eliminated and the inherent safety features of the reactor will preclude significant risks to the public or environment.