Norway and Sweden to Cooperate on Development of Lead Cooled Small Nuclear Reactors.

[John ONeill]

1. Lead

Interesting that the most common isotope of lead, Pb208 (doubly magic), has a thermal neutron cross section lower than helium, and on par with oxygen, combined with a high scattering cross section. This could maybe have long enough neutron lifetimes to act as coolant for a thermal reactor, reducing the percentage of fissile needed. Pb 208 is over 50% of lead ores generally, but in those derived from thorium with very little uranium admixture, it can make up ~90%. I read a Russian paper on the benefits of using 'radiogenic lead' (it's probably all radiogenic, back far enough); mostly over my head, though, I think.