Can Depleted Uranium Be Used as Nuclear Fuel?

Depleted Uranium is often mistakenly considered useless, but with the right conditions, it can indeed be utilized as a source of nuclear fuel. This article explores the viability of depleted uranium as a nuclear fuel, its limitations, and the potential for its use in specific reactor designs.

The Chemistry of Depleted Uranium

Depleted uranium (DU) is primarily composed of U-238, which is left over after the U-235 content has been separated from natural uranium through the process of enrichment. Natural uranium is about 0.71% U-235 and 99.28% U-238. Through enrichment, the percentage of U-235 can be raised to between 3% and 5%, while the remaining material is known as depleted uranium.

The Role of Fissionable and Fertile Isotopes

Despite being rich in U-238, not all of these isotopes can fission readily. U-238 is considered fertile and can be converted into U-239 and further into Pu-239, a fissionable isotope. This transformation can occur in a reactor with a sufficient neutron flux.

Fissionable Isotopes and Reactor Design

Unlike U-235, which requires thermal or slow neutrons to fission, U-238 can fission when exposed to fast neutrons. However, U-238 will still require a small amount of U-235 to initiate the fission process, making it "fissionable" rather than "fissile."

Theoretical and Practical Aspects

While the theoretical conversion of U-238 to Pu-239 through neutron exposure is possible, it remains a challenge in practical terms. Current reactor designs and fuel cycles are not optimized for this conversion, and the process needs further development to become economically and technically viable.

Potential for Future Reactors

Some advanced reactor designs, such as fast flux reactors, could potentially utilize depleted uranium more effectively. Fast flux reactors operate with high-energy neutrons, making them suitable for using fissionable isotopes like U-238. In these reactors, the U-238 could be converted into Pu-239, which would then be used as fuel.

The Critical Question: Feasibility

While the conversion of depleted uranium to nuclear fuel is theoretically possible, it is not practical with current technology. The lack of a sustained fast neutron flux and the need for an external neutron source make it a challenge to implement in existing nuclear power plants.

Conclusion

The use of depleted uranium as nuclear fuel is a topic of ongoing research and development. While it remains a theoretical possibility, its practical application necessitates significant advancements in reactor design and fuel cycle technologies. Current limitations do not yet allow for the widespread use of depleted uranium as a nuclear fuel, but the potential for its utilization in more specialized reactor designs remains a subject of interest.