Nuclear Technology / Volume 183 / Number 3 / September 2013 / Pages 409-426
Technical Paper / Enrichment / dx.doi.org/10.13182/NT13-A19429
As a rule, materials of small atomic weight (light and heavy water, graphite, and so on) are used as neutron moderators and reflectors. A new very heavy atomic weight moderator is proposed - radiogenic lead consisting mainly of isotope 208Pb. It is characterized by extremely small neutron radiative capture cross section ([approximately]0.23 mb for thermal neutrons, i.e., less than that for graphite and deuterium) and highest albedo of thermal neutrons.
The use of radiogenic lead to make it possible to slow down the chain fission reaction on prompt neutrons in a fast reactor is evaluated. This can improve the safety of a fast reactor.
It is noteworthy that radiogenic lead with high 208Pb content may be recovered from thorium (as well as thorium-uranium) ores without isotope separation. This has been confirmed experimentally by the investigations performed at the University of São Paulo in Brazil.