Kernreaktor

A Kernreaktor, or nuclear reactor, is a device that sustains a controlled nuclear chain reaction to release energy as heat. This heat is typically used to generate steam that drives turbines and produces electricity, though reactors are also employed for research and the production of medical and industrial isotopes.

Core components include fuel assemblies containing fissile material (such as uranium-235 or plutonium-239), a moderator to slow neutrons, a coolant to remove heat, and control rods to adjust or halt the reaction. The reactor core is surrounded by shielding and housed in a containment structure to protect workers and the environment from radiation and accidental releases.

Most civilian reactors are thermal reactors that rely on a moderator to slow neutrons and use light water or heavy water as coolant and moderator. Common designs include light-water reactors (PWRs and BWRs) and heavy-water reactors (such as CANDU). Fast reactors use fast neutrons and typically have little or no moderator, offering different fuel utilization but requiring different safety approaches.

Safety and regulation are central to reactor operation. Redundant cooling systems, negative reactivity feedback, emergency shutdown mechanisms, and robust containment are standard features. Nuclear safety is governed by national regulatory agencies and supported by international bodies such as the International Atomic Energy Agency (IAEA), with ongoing emphasis on licensing, inspection, and decommissioning.

History-wise, the first sustained, controlled chain reaction occurred in 1942 (Chicago Pile-1). Since then, reactor technology has evolved from military and research roots to widespread civilian power generation and specialized research facilities, with rigorous safety, environmental, and public-health considerations shaping design and operation.