Editing Nuclear technology (section)

=== Nuclear fission ===
{{main|Nuclear fission}}
In natural nuclear radiation, the byproducts are very small compared to the nuclei from which they originate. Nuclear fission is the process of splitting a nucleus into roughly equal parts, and releasing energy and neutrons in the process. If these neutrons are captured by another unstable nucleus, they can fission as well, leading to a [[chain reaction]]. The average number of neutrons released per nucleus that go on to fission another nucleus is referred to as ''k''. Values of ''k'' larger than 1 mean that the fission reaction is releasing more neutrons than it absorbs, and therefore is referred to as a self-sustaining chain reaction. A mass of fissile material large enough (and in a suitable configuration) to induce a self-sustaining chain reaction is called a [[Critical mass (nuclear)|critical mass]].

When a neutron is captured by a suitable nucleus, fission may occur immediately, or the nucleus may persist in an unstable state for a short time. If there are enough immediate decays to carry on the chain reaction, the mass is said to be [[Prompt criticality|prompt critical]], and the energy release will grow rapidly and uncontrollably, usually leading to an explosion.

When discovered on the eve of [[World War II]], this insight led multiple countries to begin programs investigating the possibility of constructing an [[atomic bomb]] — a weapon which utilized fission reactions to generate far more energy than could be created with chemical explosives. The [[Manhattan Project]], run by the [[United States]] with the help of the [[United Kingdom]] and [[Canada]], developed multiple fission weapons which were used against [[Japan]] in 1945 at [[Hiroshima]] and [[Nagasaki]]. During the project, the first [[nuclear reactor|fission reactors]] were developed as well, though they were primarily for weapons manufacture and did not generate electricity.

In 1951, the first nuclear fission power plant was the first to produce electricity at the Experimental Breeder Reactor No. 1 (EBR-1), in Arco, Idaho, ushering in the "Atomic Age" of more intensive human energy use.<ref>{{cite web|url=https://futurism.com/images/a-brief-history-of-technology/|title=A Brief History of Technology|website=futurism.com|access-date=9 May 2018|url-status=live|archive-url=https://web.archive.org/web/20180423093858/https://futurism.com/images/a-brief-history-of-technology/|archive-date=23 April 2018}}</ref>

However, if the mass is critical only when the delayed neutrons are included, then the reaction can be controlled, for example by the introduction or removal of [[neutron absorber]]s. This is what allows [[nuclear reactor]]s to be built. Fast neutrons are not easily captured by nuclei; they must be slowed (slow neutrons), generally by collision with the nuclei of a [[neutron moderator]], before they can be easily captured. Today, this type of fission is commonly used to generate electricity.