Neptunium is a chemical element with symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. Its position in the periodic table just after uranium, named after the planet Uranus, led to it being named after Neptune, the next planet beyond Uranus.
Three reasons Neptunium stands out
- 1
Synthetic radioactive element, used in nuclear research and fuel.
- 2
It was the very first transuranium element ever synthesised, created at a California laboratory in 1940.
- 3
Its isotope is used as a starting material to produce a radioactive fuel that powers deep-space spacecraft.
The first step beyond uranium
Neptunium became the first transuranium element created by humans, extending the table beyond what was then considered its natural end. Reactors produce it from uranium. Neptunium-237 lasts long enough to matter in nuclear waste and can serve as feedstock for producing plutonium-238.