Fission VS Fusion Energy

[ridethecliche]

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How do the the two generate energy? EK has me a little consumed.

Fusion: 2->1. Making bonds releases energy. Cool. Due to mass effect, right?

Fission:1->2. Breaking bonds releases energy. Wait, no it doesnt!

So the question is: Is energy 'gain' in fission due to the mass effect as well, where the resulting particles are 'heavier' than their originator so there's a gain in energy from

E= (delta M) (C^2)

Thanks.

 

[ilovemcat]

How do the the two generate energy? EK has me a little consumed.

Fusion: 2->1. Making bonds releases energy. Cool. Due to mass effect, right?

Fission:1->2. Breaking bonds releases energy. Wait, no it doesnt!

So the question is: Is energy 'gain' in fission due to the mass effect as well, where the resulting particles are 'heavier' than their originator so there's a gain in energy from

E= (delta M) (C^2)

Thanks.

This is what I recall - Fe (Iron) is the most stable element on the Periodic Table. Elements smaller than Iron undergo Nuclear Fusion (nuclei of two smaller atoms combine to one larger atom), while Elements Larger than Iron undergo Nuclear Decay.

A few factoids that I remember from passages:

The amount of energy produced by both Fission and Fusion are several times greater than any amount of energy for a given chemical reaction; The amount of energy produced by Fusion is several times greater than Fission.

The well-known "Atomic Bomb" is a Nuclear Fission reaction.
The sun and stars undergo Fusion reactions.

And finally, the energy requirement to produce a Fission reaction is very little compared to the immense amount of energy required to overcome the strong nuclear force in nuclear fusion. Fusions are nearly impossible to produce.




Regarding Einstein's Equation: E = deltaMC^2

M is the mass defect. Basically what this tells you is this: Let's imagine you crack open the Nucleus of an Element and pull apart all the Protons & Neutrons and place them on a scale. On the other side of the scale, you place the entire nucleus itself (where the protons & neutrons are held tightly together). What you'll find is that the masses aren't equal. We call this difference, "mass defect." But where did this mass go? This mass was converted to energy - this energy is commonly known as the "Strong Nuclear Force" which is the force responsible for holding the protons tightly together within the nucleus (even though naturally they'd want to repel). It's also the reason behind several periodic trends.

 

[jphwki82]

How do the the two generate energy? EK has me a little consumed.

Fusion: 2->1. Making bonds releases energy. Cool. Due to mass effect, right?

Fission:1->2. Breaking bonds releases energy. Wait, no it doesnt!

So the question is: Is energy 'gain' in fission due to the mass effect as well, where the resulting particles are 'heavier' than their originator so there's a gain in energy from

E= (delta M) (C^2)

Thanks.

Fusion occurs when small nuclei combine to form a larger nucleus. When you see fusion, think of how stars power themselves. They utilize fusion binding energy via fusing 4 H nuclei to form He. Fusion of nuclei lower than the mass of Fe will release energy. Whereas, fusion of nuclei greater than the mass of Fe will absorb energy.

Fission, on the other hand, involves the splitting of a larger nucleus into smaller nuclei. When you think of fission, think of the atom bomb. It utilized fission, that released neutrons, to initiate a chain reaction. U-235 can be put in an excited state via the addition of a neutron to form U-236. U236 will undergo fission to yield Xe-140 and Sr-94 and a neutron.

So in general, Fission is atom splitting and Fusion is combining atoms. Both of which can produce energy. It doesn't really involve bond formation. Fusion and Fission is more about the nuclei of atoms, whereas bonding involves electrons.

 

[ridethecliche]

Thanks!

I think that helps.

 

[SaintJude]

Going to add this old thread...b/c I just read a very good Kaplan explanation some may find useful and it helps for me to re-explain it.

A nucleus gains the energy to initiate a fission reaction from the bombardment of a particle on to the nucleus. The imparting particle transfers its kinetic energy to the nucleus--the nucleus will now have sufficient energy to initiate a fission reaction. In order for the particle to transfer its kinetic energy it must be in very close proximity to the nucleus.
B/c of the neutral charge of neutrons, when neutrons come close to the nuclei they do not experience electrostatic repulsion. Thus bombardment of neutrons onto nuclei to initiate fissions reactions work very well to due to the neutral charge of neutrons.