The word "fissil" refers to something that is capable of being split or divided into layers. Its spelling is influenced by the Latin word "fissilis". According to IPA phonetic transcription, "fissil" is pronounced as /ˈfɪsɪl/. The first syllable is pronounced as "fis" with the "i" sound pronounced as "ih", the second syllable is pronounced as "sil" with the "i" sound pronounced as "ih". Due to the rarity of the word, the correct spelling might not immediately come to mind for some people.
Fissile refers to the ability of a material to undergo nuclear fission, a process in which the atomic nucleus of an atom splits into two smaller nuclei, releasing a significant amount of energy. Fission is the basis of nuclear power and atomic bombs.
In the context of nuclear science, fissile materials are those that can sustain a chain reaction by accepting a slow-moving neutron and splitting into two or more fragments, along with the release of additional neutrons. These additional neutrons can induce fission in other nearby nuclei, leading to a self-sustaining chain reaction.
Fissile materials typically have a high atomic number and mass, making them susceptible to fission. Uranium-235 and plutonium-239 are the most commonly used fissile materials. Fission occurs when a neutron strikes the nucleus of a fissile atom, causing it to become unstable and split apart into two smaller nuclei and two or three additional neutrons. This release of neutrons can trigger further fission reactions, resulting in a release of energy and an exponential increase in neutron production.
The ability of a substance to be fissile depends on various factors, including its atomic structure, isotopic composition, and neutron absorption cross-section. Materials that are not fissile can still be fissionable, meaning they can sustain fission but need additional neutrons for a chain reaction to occur. Fissile materials play a crucial role in both peaceful nuclear energy production and the development of nuclear weapons.
The word "fissil" comes from the Late Latin term "fissilis", which is derived from the Latin verb "findere", meaning "to split" or "to cleave". In turn, "findere" can be traced back to the Proto-Indo-European root "*bʰeyd-", which carries a similar meaning of "to split" or "to separate". Therefore, the etymology of "fissil" reflects its associations with things that are easily split or prone to fragmentation.