3. Thorium cycle

3.1 Features

Thorium is an actinide 3 to 4 times more abundant in the earth's crust than uranium. Unlike uranium and plutonium, it has no fissile isotope. However, the 232 isotope, which is practically the only one present in natural thorium, is, like uranium 238, fertile. After capturing a neutron and undergoing two successive beta decays, it gives rise to a fissile uranium-233 nucleus whose neutron properties compare favorably with those of fissile uranium and plutonium nuclei [50] (figure 1 ).