uranium 238

American  

noun

Chemistry.

1. the radioactive uranium isotope having a mass number 238, comprising 99.28 percent of natural uranium: used chiefly in nuclear reactors as a source of the fissionable isotope plutonium 239.

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Etymology

Origin of uranium 238

First recorded in 1940–45

Example Sentences

While uranium 235 fissions easily, nuclear fuel is not pure—it is made mostly of uranium 238, which does not fission.

From Literature

Depleted uranium, primarily uranium 238, is what’s left over after the lighter isotope uranium-235 has been removed from natural uranium.

From Washington Times

Seaborg’s approach had only produced plutonium 239, which decays very slowly back to uranium 238.

From Scientific American

Ordinary low-enriched uranium fuel contains primarily uranium 238, the most common natural isotope of the element, along with about 5 percent uranium 235, a rarer isotope that splits, or fissions, more readily.

From Scientific American

The uranium 238 then captures the neutron and is transformed into a new element, plutonium 239, which is also fuel.

From New York Times