Recent content by marklimmage

From what I can see for thermal neutrons the cross-sections for fission for the two nuclei are: U235 - 346 barns Pu239 - 695 barns And for fast neutrons the the cross-sections are U235 - 1.8 barns Pu239 - 1.7 barns So could I conclude from these that both nuclei are much more...

Is fast neutron fission possible or just as likely as thermal neutron fission in the even-odd nuclei like U235 and Pu239?

Why do different nuclei need different neutron speed to achieve fission?? My understanding is that U-235 requires a thermal neutron in order to be likely to cause a fission reaction, however Pu-239 requires the additional energy of a fast neutron in order to cause the nucleus to undergo fission...