Fission

The second type of nuclear energy is fission. Nuclear fission is a reaction in which a large nucleus breaks apart into two smaller nuclei, releasing large amounts of energy. Nuclei can fission on their own spontaneously, but only certain nuclei, like uranium-235 and plutonium-239, can sustain a fission chain reaction. This is because these nuclei release neutrons when they break apart, and these neutrons then can hit other nuclei, causing them to also break apart and release more neutrons. This is referred to as a chain reaction. Uranium-235 is the fuel of choice in all commercial reactors (and even one natural reactor ).The uranium fuel is packed into the core and usually surrounded by a moderator, which is a substance that slows down the neutrons so they have a better chance of inducing fission. Once the chain reaction gets going, the heat from the core is typically used to boil water and drive a steam turbine. The chain reaction can be slowed down and even turned off by introducing control rods, which contain materials that absorb neutrons.

235/92U + 1/0N→21/0N + 92/36Kr + 142/56Ba + energy • Weapons-grade fissionable material (uranium233) is harder to retrieve safely and clandestinely from the thorium reactor than plutonium is from the uranium breeder reactor.
 * Thorium Energy for tomorrow?**

• Thorium produces 10 to 10,000 times less long-lived radioactive waste than uranium or plutonium reactors.

• Thorium comes out of the ground as a 100% pure, usable isotope, which does not require enrichment, whereas natural uranium contains only 0.7% fissionable U235.

• Because thorium does not sustain chain reaction, fission stops by default if we stop priming it, and a runaway chain reaction accident is improbable. Besides, the priming process is extremely efficient: the nuclear process puts out 60 times the energy required to keep it primed. Because of this, the device is also called, (quite inappropriately) an "Energy Amplifier."