[The_Media_never_lie]

As I recall, you get a “bonus” of 1 MeV when you go from odd to even numbers of nucleons in the neutron capture event. The binding energy gets you about 5 MeV, the “bonus” of 1 MeV going from odd to even gets you one more, for a total of 6 MeV, just the amount you need to add to the nucleus to induce the fission reaction. U238 neutron capture goes from even to odd, so you don’t get the bonus. The 5 MeV you get from the binding energy isn’t enough to do it for thermal neutron-induced fission. You need an incoming “fast” neutron (1 MeV or more) to fission the U238 nucleus. So it is a threshold reaction rather than a thermal neutron capture. Do I have the numbers right (it’s been awhile)

Please, don't even think about a trip to Iran any time soon.

[chimera]

Well, as a matter of fact, one of my students was thinking about “going home” (Shiraz) after he graduated. I have been trying mightily to get him to change his mind. Trouble is, where is he going to go? Jobs here in the nuclear business are pretty much forbidden for people from countries that aren’t signatories to the NPT. I’m hoping we can keep him on as a postdoc until he gets his citizenship (he is not an illegal alien).