Np238

Np-238 is an isotope of the actinide element neptunium (Np) with mass number 238. It is radioactive and synthetic, not found in meaningful quantities in nature. Np-238 is produced in nuclear reactors by neutron capture on Np-237, forming Np-238, which then undergoes beta decay to plutonium-238 (Pu-238).

The decay of Np-238 proceeds by beta minus emission, converting one neutron into a proton and yielding Pu-238 as the daughter nuclide. The half-life of Np-238 is short on a human timescale, on the order of days, so it exists transiently in production streams before decaying further. Pu-238, the decay product, is a long-lived alpha emitter used in various applications.

In the nuclear fuel cycle and related production workflows, Np-238 is primarily encountered as an intermediate in the production of Pu-238. Pu-238 is the isotope of major practical value for space missions and other radioisotope power systems, while Np-238 itself is generally not isolated for long-term use outside research or production settings.

Chemically, Np-238 behaves similarly to other actinides, forming oxides and salts and capable of existing in multiple oxidation states under different conditions. Its radiological hazard is the dominant concern for handling, requiring appropriate shielding, containment, and remote handling to minimize ingestion, inhalation, or prolonged exposure.

See also: neptunium, plutonium-238, actinides, nuclear reactor fuel cycle.