Nuclear fusion occurs when two atoms fuse together, or combine, into a larger atom. This fusion process releases a great amount of energy. Nuclear fission occurs when one atom is ripped apart into smaller atoms. Fission and fusion both release a great deal of energy, but fusion releases about four times more.
If you look up into the sky during the day, you can see a huge nuclear reactor that’s powered by nuclear fusion: the sun.
Because the sun is enormous (over 1.3 million Earths can fit inside), it has a lot of gravity. That high level of gravity creates enough pressure to force atoms to slam into each other, forming larger atoms. One example of this is two hydrogen atoms fusing together to form helium.
On Earth, scientists are attempting to recreate nuclear fusion to generate electricity. This would be an advancement in power production technology because all existing nuclear plants are powered by fission. In the last couple years, scientists have made large steps forward in achieving this goal. In December 2022, U.S. Department of Energy scientists were able to produce more energy than they put into a nuclear fusion reactor for just a few seconds. They were successful again in August 2023.
In nuclear power plants around the globe, nuclear fission is induced by throwing neutrons at uranium atoms at high speeds. The impact is so strong it causes the uranium atoms to split, which releases a lot of energy. When the uranium atom splits, more neutrons are released and they continue to collide with other uranium atoms. It’s a chain reaction that repeats itself over and over again.
Within the two types of nuclear reactors, there are several more subcategories.
Some of the notable fission reactor designs include:
In PWRs, water acts as both the coolant and moderator. The water is kept under high pressure to prevent boiling, and it transfers heat from the reactor core to a steam generator to produce electricity.
BWRs also use water as both the coolant and moderator. In this design, the water is allowed to boil directly in the reactor core, producing steam that drives the turbine to generate electricity.
HWRs use heavy water, which contains a higher concentration of deuterium, as both the coolant and moderator. Heavy water reactors can utilize natural uranium as fuel and are known for their efficient use of resources.
AGRs use carbon dioxide gas as the coolant and graphite as the moderator. This design is primarily employed in the United Kingdom and is known for its high thermal efficiency.
Two main approaches to achieving fusion reactions are:
MCF uses strong magnetic fields to confine and control a hot plasma of hydrogen isotopes, such as deuterium and tritium. The goal is to achieve conditions where fusion reactions can occur and sustain a self-sustaining plasma state.
ICF involves rapidly compressing and heating fuel pellets using powerful lasers or particle beams. The intense pressure and temperature cause the fuel to undergo fusion reactions. ICF is primarily being explored for its potential use in thermonuclear weapons and as a stepping stone toward achieving practical fusion power.
