fissionsreaktionen

Fissionsreaktionen, also known as nuclear fission, refer to the process in which the nucleus of an atom splits into two or more smaller nuclei, releasing a large amount of energy, neutrons, and gamma radiation. The reaction typically occurs when a heavy nucleus such as uranium‑235 or plutonium‑239 absorbs a thermal neutron, becoming unstable and fragmenting. The energy released stems from the binding energy per nucleon curve; lighter fragments are more tightly bound, resulting in a net release of kinetic energy, which is harnessed in reactors.

A critical aspect of a fission reaction is the chain reaction. The neutrons emitted can induce further fissions, sustaining a self‑propagating process. Control is achieved through neutron absorbers or control rods made of boron, cadmium, or hafnium that are inserted into the reactor core to moderate the neutron flux. Moderators like heavy water, light water, or graphite slow down neutrons, increasing the probability of inducing further fissions in typical thermal reactors.

Historically, the discovery of fission in 1938 by Hahn and Strassmann led to the first controlled chain reaction in 1942 at the University of Chicago, an event that contributed to nuclear research and weapons during World War II. Since then, nuclear power plants have been built worldwide, operating on the same principle to generate electricity. Small reactors for research and naval propulsion, such as those used in submarines and aircraft carriers, also rely on fission technology.

Despite its merits of high energy density and low greenhouse gas emissions, fission faces challenges. Radioactive waste must be carefully managed for long periods. Accidents, exemplified by Chernobyl and Fukushima, have underscored the importance of stringent safety protocols. Moreover, advanced reactor designs, including fast breeders and molten‑salt reactors, aim to improve fuel efficiency, reduce waste, and enhance safety features.