Why does fission create energy

The vast majority of the waste from nuclear power plants is not very radioactive and for many decades has been responsibly managed and disposed of. The used fuel which comes out of the reactor can be managed in different ways, including recycling for energy production or direct disposal. As a matter of fact, many countries have been using recycled fuel for decades to partially fuel their reactors. How does a nuclear reactor work?

A reactor being refuelled Image: Vattenfall What fuels a reactor? Nuclear fuel pellets are not much larger than a sugar cube Image: Kazatomprom How about the waste? Used nuclear fuel awaiting recycling Image: Rosatom Share. In Situ Leach Mining of Uranium. United Arab Emirates. Externalities of Electricity Generation.

I think it's worth specifically addressing the word 'both' in the question. If you say 'both release energy', you're implying some contradiction, but there actually isn't any such issue. You're comparing apples and oranges. For a substance which has an endothermic fusion reaction, the fission of that substance will probably be a net exothermic process.

This is applicable for elements heavier than Iron. For elements with exothermic fusion reactions, the opposite is true.

So eventually, for a given element, only one of the two processes fission and fusion will be a net exothermic process. You could also look at this Physics SE post: Are all nuclear fusion reactions exothermic and fission reactions endothermic? Because attraction of the strong nuclear force has a short range , while electrostatic repulsion has a long range. As a consequence, electrostatic repulsion will grow faster with number of nucleons than nuclear attraction protons throughout the nucleus will repel each other, while only neighboring nucleons will attract.

This causes less binding energy per nucleon as their number increases and at some point this reaches maximum and starts to decrease. Iron just happens to be at the maximum of the binding energy per nucleon. Therefore, for heavier elements than iron, fission releases energy, while for lighter elements than iron, fusion releases energy. This can't be completely circumvented by adding more neutrons, mainly because weak nuclear force makes them unstable, but it works to some degree, which is why heavier nuclei usually have higher neutron to proton ratio.

But at some point it is no longer possible to add more nucleons without making the whole thing unstable, which is why very heavy elements are radioactive. The net energy is positive only for fusion of elements lighter than iron, i. For elements heavier than iron, fusion consumes energy, i. We can use fission today to release energy due to the fact, that some process in the past e. There's energy involved in keeping atoms apart, but also energy involved in holding an atom together.

When you smash an atom, this bonding energy is released. In fact, one of the four fundamental forces is responsible for binding atoms together - the strong nuclear force.

Fusion works by banging together the same two elements and sticking them together to form a new heavier element. When you add the masses of the two original elements it is greater than the new element. It is this mass difference that becomes energy. Here m is 2 x Mass of original element - Mass of new element and c is the speed of light. When the mass of the two original elements becomes heavier the difference between their masses and the new element gets smaller.

Fission works by splitting one element into two new lighter elements. When you add the masses of the two new elements it is less than the original element. Here m is Mass of original element - Mass of new elements and c is the speed of light. I wanted to mention that is technically much more complicated than what I say here.

The short answer is still the same: Mass is converted into Energy. Wanted to provide a quick answer, but apparently now is frowned upon to give quick answers in comments, so here it is:.

Roughly speaking, nuclear fission is endothermic for nuclei where nuclear fusion would be exothermic, and viceversa. For nuclei smaller than Iron, fission is typically endothermic, while fusion is exothermic. For nuclei heavier than Iron, the situation reverses. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

Create a free Team What is Teams? Learn more. Why do fusion and fission both release energy? Ask Question. Asked 2 years, 9 months ago. Active 2 years, 9 months ago. Viewed 21k times. Moving to heavier atoms, less energy is released in each fusion event; until, at iron 26 protons and 30 neutrons , no more energy is released by fusion. Any bigger, it takes energy to make fusion happen.

Atoms with really huge nuclei, such as uranium and plutonium do the opposite of fusion: they release energy when they break apart. The Fusion in Europe newsletter delivers news and views on the progress of fusion research directly to your inbox.