19.16: Breeder Reactors

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Because \(\ce{_{92}^{235}U}\) is only 0.7 percent of naturally occurring uranium, its supply is fairly limited and could well only last for about 50 years of full-scale use. The other 99 percent of the uranium can also be utilized if it is first converted into plutonium by neutron bombardment:

\[\ce{_{92}^{238}U + _{0}^{1}n -> _{94}^{239}Pu + 2 _{-1}^{0} e} \nonumber \]

\(\ce{_{94}^{239}Pu}\) is also fissionable, and so it could be used in a nuclear reactor as well as \(\ce{_{92}^{235}U}\).

The production of plutonium can be carried out in a breeder reactor which not only produces energy like other reactors but is designed to allow some of the fast neutrons to bombard the \(\ce{_{92}^{235}U}\), producing plutonium at the same time. More fuel is then produced than is consumed.

Breeder reactors present additional safety hazards to those already outlined. They operate at higher temperatures and use very reactive liquid metals such as sodium in their cooling systems, and so the possibility of a serious accident is higher. In addition the large quantities of plutonium which would be produced in a breeder economy would have to be carefully safeguarded. Plutonium is an α emitter and is very dangerous if taken internally. Its half-life is 24,000 years, and so it will remain in the environment for a long time if dispersed. Moreover, \(\ce{_{94}^{239} Pu}\) can be separated chemically (not by the much more expensive gaseous diffusion used to concentrate \(\ce{_{92}^{ 235}U}\) from fission products and used to make bombs. Such a material will obviously be attractive to terrorist groups, as well as to countries which are not currently capable of producing their own atomic weapons.