THE nuclear fission it is the process of dividing the nucleus of a heavy chemical element into two lighter elements of approximate mass. This process has a low probability of occurring naturally, but an element can be forced to divide by receiving energy or being bombarded by a neutron.
The most used element in fission is the uranium (U). 6 g of this element can yield 5.2 x 1022 MeV, enough energy to maintain a small residence for a full day.
Brief history
In the first half of the 20th century, the English scientist James Chadwick discovered neutrons, which, a few years later, were deeply studied by Enrico Fermi. Fermi's research showed that, because he didn't have electric charge, neutrons could be used as projectiles in nuclear experiments, as they do not undergo electrical interactions.
the physics Lise Meitner and some collaborators developed, in the late 1930s, very important works on Nuclear physics, bringing up the term fission for the process of dividing a chemical element.
Uranium enrichment
The most used element in nuclear fissions is uranium-235 (235U), because its fission occurs from the bombardment of this material with neutrons of low kinetic energy, the thermal neutrons. Natural uranium contains less than 1% of 235U and most of 238U, element that cannot undergo fission by thermal neutrons. It's possible add artificially 235Uto make the compound more susceptible to fission. This process is called uranium enrichment.
Possibilities of using fission
Nuclear fission is already used for energy production, even if it is not a clean form of production, since after fission, radioactive elements are generated. An example of hazardous elements generated after fission is the barium.
Angra dos Reis nuclear power plant, in Rio de Janeiro
nuclear bombs they work through the fission process. A great example is the nuclear warheads dropped on the Japanese cities of Hiroshima and Nagasaki at the end of World War II.
Hiroshima City a month after the 1945 nuclear warhead explosion
fission example
A classic example of the occurrence of nuclear fission is that of 235U. The following equation shows that, after absorbing a neutron, the uranium nucleus is divided into a xenon nucleus (140Xe) and another of strontium (94Mr). Since these fragments are not stable, they emit an electron and a neutrino (a process called beta decay) until they become stable.
235U + n → 236U → 140Xe + 94Sr + 2n
As at each fission process, at least two neutrons are released, nuclear fission occurs through a chain reaction, in which each new neutron created collides with a uranium nucleus, generating a new fission.
By Joab Silas
Graduated in Physics
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/fisica/o-que-e-fissao-nuclear.htm
