Nuclear Fission help

Question

Describe the process of nuclear fission. Answer how does it work and when is it used. What is meant by the chain reaction. And how do you control it

Answer 1

Hello, North,

That is a broad question. I'll give you the Cliff Notes version, with suggested links for more details.

Nuclear fission is the splitting apart of a single atom into two or more atoms, with a release of energy. A good example is the fission of an uranium isotope, ²³⁵₉₂U. This isotope has 92 protons and (235 - 92) = 142 neutrons in it's nucleus. This isotope of uranium is relatively unstable. It's nucleus has too many neutrons (142) compared to the 92 protons. One might say it needs to lose some weight, if you want a poor analogy. The relatively instability of ²³⁵₉₂U causes it to under a fission reaction. It fissons into two smaller elements and releases energy in the process. It's half-life is 703.8 million years, so you'd better grab a seat.

²³⁵₉₂U fissions when it is hit by a free neutron that causes the atom to split. It breaks into two smaller atoms, ¹⁴⁴₅₆Ba and ⁸⁹₃₆Kr, and several loose neutrons fly away. The process results in a slight loss of mass. Not much, but with E = mc², it doesn't take much mass to result in a large energy release. (c is the speed of light). The amiunt of mass lost in a sigle U atom is The mass lost in one uranium atom is equal to about 3.20×10⁻¹¹ J of energy. One mole (6.02x10²³) of U atoms (238 grams) would provide 1.92x10¹³ Joules of energy. That is equal to 4.6x10⁶ toms of TNT, all from only 238 grams of ²³⁵₉₂U.

And that is just the start. The splitting of the uranium atoms realease more free neutrons, often having high energies and hitting other nearby uranium atoms. These additional neutrons then start a chain reaction. They cause multiple fissions among nearby U atoms. The heat and free neutrons build quickly. Uncontrolled, the result is a nuclear explosin. Nucler power plants can only operate if they can moderate the asdsitional neutrons freed from a fissioning atomc.There are various methods for doing this. Graphite rods are commonly employed as pure graphit can absord these high energy neutrons.

Do a search. https://energyeducation.ca/encyclopedia/Nuclear_fission