Carolinium

Element 148, a synthetic transuranic element sitting below plutonium on the periodic table.

Properties

Carolinium has a half-life of under a year. It is most useful for its very low critical mass, lower than plutonium. This enables the construction of miniaturized nuclear warheads and nuclear reactors. The warheads are often used against small hardened targets like power armored soldiers, and carolinium fission reactors excel as miniature power sources of ultra-high energy density.
Similar to plutonium, carolinium is flammable in oxygen. It is extremely dangerous when ingested since its radioactive decay causes it to emit alpha particles which can irradiate and kill soft tissues like organs if directly exposed to them.

Production

With its relatively short half-life, carolinium is not found in nature and must be synthesized through elemental transmutation. This is done in specialized facilities similar to particle accelerators and requires feedstocks of other elements with high atomic numbers, as well as antimatter to produce gamma rays. Because it becomes useless after a few months in storage and has to be reprocessed it is advantageous to manufacture it as close as possible to the intended site of use.
For transport and storage pure carolinium is shaped into thin subcritical rods which are inserted into neutron-moderating boron blocks for tight packing in shipping boxes. Without this precaution, piling too much carolinium in one place together could cause a fission reaction if a critical mass builds up.

Use

Its low critical mass (~1 kilogram) enables the construction of miniature nuclear reactors and fission warheads, small enough to fit in man-portable devices.
Due to the sheer expense, carolinium weapons are the exclusive purview of state-level actors or their equivalents.

¹⁴⁸Crl

331

Type

Elemental / Molecular

Value

Very expensive

Rarity

Rare