In reply to Eric Walker's message of Tue, 23 Apr 2013 20:25:05 -0700: Hi, [snip] >I got the impression >somewhere that proton capture is fundamentally more benign than neutron >capture, both in the immediate effects and in any unstable daughters, but >this could be a misunderstanding. > >Eric
You probably have me to thank for that impression. I have been saying it long enough. :) The reason is that when fission ensues, the ratio of neutrons:protons in stable daughter nuclei is less than that in the parent nucleus[1], hence fission results in excess neutrons. That means that either free neutrons are produced (during the fission of very heavy nuclei), or at least one of the daughter nuclei ends up with too many neutrons, and is consequently radioactive. This is exacerbated when the fission reaction is brought about by adding a neutron. However if you could bring about the fission reaction by adding one or more protons instead of a neutron, then you already have a "head start" on balancing the neutrons and protons in the daughter nuclei, and thus improving their stability, so that they need not be radioactive. (Nature actually prefers to produce stable nuclei when it gets a chance). 1) If you look at the n:p ratio for the elements, you will see that it increases as you go up in the periodic table (once you get past about S). At the low end it tends to be 1:1, while at the high end it's about 1.6:1. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
