Nuclear Fuel
To be a useful fuel for nuclear fission chain reactions, the material must:
- Be in the region of the binding energy curve where a fission chain reaction is possible (i.e. above radium)
- Have a high probability of fission on neutron capture
- Release two or more neutrons on average per neutron capture (which means a higher average number of them on each fission, to compensate for nonfissions, and absorptions in the moderator)
- Have a reasonably long half life
- Be available in suitable quantities
Thermal neutrons | Epithermal neutrons | |||||
---|---|---|---|---|---|---|
σF | σγ | % | σF | σγ | % | |
531 | 46 | 8.0% | 233U | 760 | 140 | 16% |
585 | 99 | 14.5% | 235U | 275 | 140 | 34% |
750 | 271 | 26.5% | 239Pu | 300 | 200 | 40% |
1010 | 361 | 26.3% | 241Pu | 570 | 160 | 22% |
Fissile nuclides in nuclear fuels include:
- Uranium-235 which occurs in natural uranium and enriched uranium
- Plutonium-239 bred from uranium-238 by neutron capture
- Plutonium-241 bred from plutonium-240 by neutron capture. The Pu-240 comes from Pu-239 by the same process.
- Uranium-233 bred from thorium-232 by neutron capture
Fissile nuclides do not have a 100% chance of undergoing fission on absorption of a neutron. The chance is dependent on the nuclide as well as neutron energy. For low and medium-energy neutrons, the neutron capture cross sections for fission (σF), the cross section for neutron capture with emission of a gamma ray (σγ), and the percentage of non-fissions are in the table at right.
Read more about this topic: Fissile
Famous quotes containing the words nuclear and/or fuel:
“The emotional security and political stability in this country entitle us to be a nuclear power.”
—Ronald, Sir Mason (b. 1930)
“I had an old axe which nobody claimed, with which by spells in winter days, on the sunny side of the house, I played about the stumps which I had got out of my bean-field. As my driver prophesied when I was plowing, they warmed me twice,once while I was splitting them, and again when they were on the fire, so that no fuel could give out more heat. As for the axe,... if it was dull, it was at least hung true.”
—Henry David Thoreau (18171862)