kernekædereaktion

Kernekædereaktion is the Danish term for nuclear chain reaction. This is a self-sustaining sequence of nuclear fission events. In a nuclear fission process, an atomic nucleus, typically a heavy element like uranium or plutonium, absorbs a neutron. This absorption causes the nucleus to become unstable and split into two or more lighter nuclei, releasing a significant amount of energy and, crucially, two or three additional neutrons.

These newly released neutrons can then go on to strike other fissile nuclei, causing them to fission as well. If, on average, at least one neutron from each fission event causes another fission, the process becomes self-sustaining, leading to a chain reaction. The rate at which this chain reaction occurs can be controlled. In nuclear reactors, the reaction is kept at a steady rate, known as a critical state, where exactly one neutron from each fission causes another fission. This controlled release of energy is used to generate electricity.

If the number of neutrons causing further fission exceeds one, the reaction rate increases exponentially, leading to a supercritical state. This is the principle behind nuclear weapons, where an uncontrolled chain reaction releases a massive amount of energy in a very short time. Conversely, if fewer than one neutron causes further fission, the reaction is subcritical and will eventually die out. The concept of kernekædereaktion is fundamental to both nuclear power generation and nuclear weapons technology.