Splitting the atom

[rogerinnh]

What is it about Uranium and similar heavy elements that makes them "splittable", and therefor useful for generating nuclear energy, unlike lighter elements?

 

[drwayne]

That is an excellent question.

Here is the short version. All nuclei are not equally bound. In fact, if we look
at the binding energy per nucleon curve we see that binding energy peaks at
about iron:

http://en.wikipedia.org/wiki/Binding_en ... ergy_curve

What does that mean? In the case of fission, we take an element that is
on the right hand side of the curve, and we break it into two more tightly
bound nuclei. The difference in binding energy (the distance uphill on the
curve) goes off as energy.

For fusion, elements on the left hand side of the curve cobine to form a
more tightly bound nucleus, with the change in binding energy going
off as a product of the reaction.

If you can understand the BE/A curve (and it may take a while, it did
for me), you can understand an awful lot about fiission and fusion.

Wayne

 

[origin]

What is it about Uranium and similar heavy elements that makes them "splittable", and therefor useful for generating nuclear energy, unlike lighter elements?

Larger atoms also tend to be unstable, this is a rough generalzation I know. Isotopes of atoms also tend to make the atoms unstable, such as carbon 14 and cobalt 60. Uranium 235 and plutonium239 are unstable atoms and decay through a rather complicated decay chain ending in lead. Uranium and plutonium emit radiation in the form of alpha particles as they decay, which is esentially a helium nucleus which is ejected from the U and PU nucleus at a sizable percentage of the speed of light. The unique thing about U235 and PU239 is the addition of 1 neutron to the neucleus makes the atom so unstable that it splits instantly upon absorbing the neutron.

This is to just give a general feel of what is going on, there are lots of good sites that talk about nuclear fission.

 

[kg]

Uranium and plutonium emit radiation in the form of alpha particles as they decay, which is esentially a helium nucleus which is ejected from the U and PU nucleus at a sizable percentage of the speed of light. The unique thing about U235 and PU239 is the addition of 1 neutron to the neucleus makes the atom so unstable that it splits instantly upon absorbing the neutron.

Where do the alpha particles get all that energy from? Is it simply pushed away from the neucleus by the electromagnetic force or is there another force at play here? How about neutrons? Which force hurls them away from the neucleus seeing that a neutron doesn't have a charge?

 

[drwayne]

The change in binding energy shows up as kinetic energy in the decay products.

Wayne