Thorium Reactor

thorium reactor [′thȯr·ē·əm rē‚ak·tər]

(nucleonics)

A nuclear reactor in which thorium surrounds the central enriched uranium core to give breeder operation.

---

Thorium Reactor 

nuclear reactor in which the fissionable material is uranium (²³³U), formed in the same reactor from thorium (²³²Th). Natural ²³²Th itself is not suitable for carrying out a nuclear chain reaction and so serves as a raw material in thorium reactors.

The isotope ²³³U, which undergoes fission upon interaction with both fast and slow neutrons, is first placed in the reactor after being obtained from a different reactor. As a result of the capture of a neutron formed in the fission of ²³³U, the thorium (²³²Th) nucleus, after twice undergoing beta decay, is converted into a ²³³U nucleus; that is, a secondary nuclear fuel is produced. The ability of thorium reactors to effect a large-scale regeneration of ²³³U (seeBREEDER REACTOR) increases the importance of the large natural reserves of thorium for the nuclear power industry. However, as of the mid-1970’s, the period for doubling the nuclear fuel in thorium reactors is too long (10–12 years); the reactors are used only for research.