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.

---

Etymology

Origin of uranium 238

First recorded in 1940–45

Example Sentences

"The ratio of isotopes of uranium 238 to 225 on our planet is different than anywhere else in the universe because the two isotopes decay at different timescales," Brownless said.

From Salon • Sep. 1, 2023

This combination of elements indicated that the explosion was the "fission-fusion-fission" type, which gets much of its energy from the fission of normally inactive uranium 238.

From Time Magazine Archive

Penetrating into the ICBM's outer shell of uranium 238, they can produce slow fission, causing heat that may deform the warhead or set off its lens charges.

From Time Magazine Archive

These neutrons have to penetrate an outer shield of uranium 238, which reduces their velocity, increases the bomb's explosive punch and releases harmful radioactivity.

From Time Magazine Archive

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

From "Meltdown" by Deirdre Langeland