Editing Fissile material (section)

== Nuclear fuel ==
{{Mainarticle|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.,&nbsp;above [[radium]])
* Have a high probability of fission on [[neutron capture]]
* Release more than one neutron on average per neutron capture. (Enough of them on each fission, to compensate for non-fissions and absorptions in non-fuel material)
* Have a reasonably long [[half-life]]
* Be available in suitable quantities.

{| class="wikitable" align="right" id="Capture-fission-ratios"
|+Capture-fission ratios of fissile nuclides
!colspan=3|Thermal neutrons<ref>{{cite web |url=http://www.nndc.bnl.gov/chart/reColor.jsp?newColor=sigf |title=Interactive Chart of Nuclides |publisher=Brookhaven National Laboratory |access-date=2013-08-12 |archive-date=2017-01-24 |archive-url=https://web.archive.org/web/20170124175936/http://www.nndc.bnl.gov/chart/reColor.jsp?newColor=sigf |url-status=dead }}</ref>!! !!colspan=3|Epithermal neutrons
|-
!σ<sub>F</sub> (b)!!σ<sub>γ</sub> (b)!!%!! !!σ<sub>F</sub> (b)!!σ<sub>γ</sub> (b)!!%
|-
|531||46||8.0%||<sup>233</sup>U||760||140||16%
|-
|585||99||14.5%||<sup>235</sup>U||275||140||34%
|-
|750||271||26.5%||<sup>239</sup>Pu||300||200||40%
|-
|1010||361||26.3%||<sup>241</sup>Pu||570||160||22%
|}

Fissile [[nuclide]]s in nuclear fuels include:

* [[Uranium-233]], bred from [[thorium-232]] by neutron capture with intermediate decays steps omitted.
* [[Uranium-235]], which occurs in [[natural uranium]] and [[enriched uranium]]
* [[Plutonium-239]], bred from uranium-238 by neutron capture with intermediate decays steps omitted.
* [[Plutonium-241]], bred from plutonium-240 directly 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 [[Neutron cross-section|cross section]]s for fission (σ<sub>F</sub>), the cross section for neutron capture with emission of a [[gamma ray]] (σ<sub>γ</sub>), and the percentage of non-fissions are in the table at right.

Fertile nuclides in nuclear fuels include:

* [[Thorium-232]], which breeds uranium-233 by neutron capture with intermediate decays steps omitted.
* [[Uranium-238]], which breeds plutonium-239 by neutron capture with intermediate decays steps omitted.
* [[Plutonium-240]], which breeds plutonium-241 directly by neutron capture.