Natural uranium (NU) refers to refined uranium with the same isotopic ratio as found in nature. It contains 0.7% uranium-235, 99.3% uranium-238, and a trace of uranium-234 by weight. In terms of the amount of radioactivity, approximately 2.2% comes from uranium-235, 48.6% uranium-238, and 49.2% uranium-234.
Natural uranium can be used to fuel both low- and high-power reactors. Historically, graphite moderated reactors and heavy water moderated reactors have been fueled with natural uranium in the pure metal (U) or uranium dioxide (UO2) ceramic forms, however experimental fuelings with uranium trioxide (UO3) and triuranium octaoxide, (U3O8) have shown promise.
The 0.72% U-235 is not sufficient to produce a self-sustaining critical chain reaction in light water reactors or nuclear weapons; these applications must use enriched uranium. In rare occasions, earlier in geologic history when U-235 was more abundant, uranium ore was found to have naturally engaged in fission, forming natural nuclear fission reactors.
During the Manhattan Project, the name Tuballoy was used to refer to natural uranium in the refined condition; this term is still in occasional use at present.
Famous quotes containing the word natural:
“It is impossible to dissociate language from science or science from language, because every natural science always involves three things: the sequence of phenomena on which the science is based; the abstract concepts which call these phenomena to mind; and the words in which the concepts are expressed. To call forth a concept, a word is needed; to portray a phenomenon, a concept is needed. All three mirror one and the same reality.”
—Antoine Lavoisier (1743–1794)