Another way to increase the amount of energy that can be extracted from nuclear fuel is to promote the creation of more fissionable material within the reactor itself. In ordinary nuclear power plants, some of the neutrons released during fission are absorbed by uranium-238, a material that does not undergo the process. When this happens, it triggers a series of reactions that produce other types of fissionable material that can generate heat in a nuclear reactor. Essentially, these reactions turn uranium-238 into fuel, allowing the plant to operate longer between refueling. Researchers have long known how to increase this fuel production within the reactor, even to the point that certain reactors can produce more fuel than they consume. But again, the danger is that creating too much new fuel could provide materials for nuclear weapons. So the researchers are investigating ways to increase fuel production, but not so much that it becomes a nuclear proliferation risk. The result would still be both more energy from a given amount of fuel and less waste.
Finally, Kazimi and Shatilla are designing the new plants to operate at higher temperatures than conventional reactors, thereby increasing the efficiency with which they convert heat energy into electricity. This would also make nuclear plants more useful as a source of heat for chemical reactions, such as hydrogen generation. Toward this end, the pair is investigating unconventional materials for coolants, such as molten salts, which are less corrosive at high temperatures than the water that is commonly used. The researchers are also studying the use of superheated steam, which involves boiling water to create steam, and then heating the steam to yet higher temperatures. The higher temperatures yielded will also require new materials in the core, such as a silicon carbide ceramic that Kazimi has been developing. This silicon carbide is made in the form of a mesh that can stretch without breaking as the reactor heats up and cools down.
Kazimi notes that the research project is still only one year old and that final designs could be several years away. Ultimately, Shatilla says, the goal is to produce designs in which “there is no possible pathway to divert nuclear material into a weapons track, and then at the same time produce nuclear power with the environment in mind.” If the project is successful, he says, the designs could be useful in many more places than just the Middle East.
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