Uranium & Fusion: Why Does the Process End with Iron?

[warrior_1]

Is the reason why the energy liberating fustion process ends with
uranium(more precisely Iron) is that uranium's bindind energy per nucleon begins to decrease and hence will absorb energy rather than emit it, and thus is not self sustaining?

Thanks in Advance

 

[Andrew Mason]

Is the reason why the energy liberating fustion process ends with
uranium(more precisely Iron) is that uranium's binding energy per nucleon begins to decrease and hence will absorb energy rather than emit it, and thus is not self sustaining?

Thanks in Advance

For He to Fe, the binding energy per nucleon is greater than the energy needed to push the nucleons together. You can also look at it the other way around: the energy required to pull the nucleus apart until the coulomb repulsion between protons exceeds the nuclear binding force between them is greater than the energy released by that coulomb repulsion. For anything higher than Fe, the binding energy per nucleon is less than the energy needed to push the nucleons together.

So in the case of Hydrogen fusion, the energy required to bring a proton (attached to a neutron) close enough to another proton (attached to two neutrons) so that the nuclear force grabs hold is less than the energy released when that nuclear force grabs hold.

In the case of uranium, the energy required to overcome the nuclear forces between two chunks of the uranium nucleus is much less than the coulomb repulsion energy that sends those two chunks away from each other when the nuclear forces are overcome.

AM