Why is uranium used to produce electricity?
Uranium is one of the heaviest elements in nature. In its nucleus, there are 92 protons and a variable number of neutrons, ranging from 140 to 146. However, only a few combinations occur spontaneously in nature, and the most common are uranium-238 (92 protons and 146 neutrons) and uranium-235 (92 protons and 146 neutrons).
In nature, uranium can only form in certain extreme events, known as r-processes, which occur in violent cosmic explosions such as supernovas or neutron star collisions. Although natural uranium is rare, the presence of decaying uranium is one of the reasons why our planet has internal heat.
Over time, it emits radiation in the form of helium atoms, turning into thorium. Almost all uranium isotopes (versions with different numbers of neutrons) have very long half-lives (the time it takes for a sample to halve its uranium content). Uranium-238 has a half-life of up to 4.5 billion years.
Uranium has been used since Roman times as a yellow glaze in ceramics and glass. In 1789, German chemist Martin Heinrich Klaproth mixed nitric acid with a solid, then neutralized the solution with sodium hydroxide. This reaction produces a yellow substance that sinks to the bottom.
When heated with coal, it turns into a black powder that Kalproth mistakenly believes is pure uranium, when in reality it is just an oxide of the element. He named this new element after the planet Uranus, discovered just eight years ago by Willaim Herschel. It was not until 1841 that the first pure Uranium sample was successfully isolated by the chemist Eugène-Melchior Péligot.
Today, uranium is no longer used to color glasses and enamels, instead its main application lies in radioactivity, discovered in 1896 by Henri Becquerel.
Four decades later, in 1934, a team of Italian physicists led by Enrico Fermi performed the decay of uranium with neutrons and discovered that it gave off electrons and positrons (the antiparticles of electrons). Subsequent work by Otto Hahn, Fritz Strassmann, Lise Meitner and Otto Robert Frisch showed that uranium could decay into a lighter element and named the process nuclear fission.
One kilogram of uranium-235, if led through complete fission, could release chemical energy equivalent to burning 1.5 million kilograms of coal. That enormous capacity to store and release energy has allowed the element to be used in electricity generation and in nuclear weapons such as the atomic bomb.
In nuclear power plants, the radiation from the uranium fuel rods heats a coolant, the heat generated then heats the water in another container and turns it into steam. The steam pushes the turbines of the generator to generate electricity, and importantly, the process does not produce greenhouse gas emissions.
In practice, however, natural uranium is not an ideal feedstock in many reactors. More than 99.2% of uranium mined on Earth is uranium-238, while uranium-235 makes up only 0.711%. Uranium-235 makes a very good nuclear chain reaction, helping to maintain a stable reaction.
To be able to do this, we need to have enough isotope uranium-235 in the reactor’s fuel rod. That’s when uranium needs to be enriched, through isotope separation to increase the percentage of uranium-235.
The remainder of the enrichment will produce depleted uranium (with less uranium-235). It is used in containers for transporting radioactive materials, industrial radiography equipment, as well as military purposes such as armor plating and armor-piercing projectiles.
at Blogtuan.info – Source: genk.vn – Read the original article here