Gold-198

Gold-198 is a ridiculously radioactive and rare radioisotope. It is naturally pyrophoric due to its obscene radioactivity.

Production
The SILEX can extract it from Fallout with only a 1% chance to be in each pile. For the most part however, it is be extracted from spent Highly Enriched Australium Fuel or directly bred/irradiated from normal Gold in an RBMK irradiation column.

Uses
Liquidator Medal, an armor mod that removes 10 RAD/s.

As a billet, it can be used to make Flashgold or a strong Self-Charging Battery, which provides 2.5kHE/tick.

It has an RTG form, which provides an incredibly strong 100 power per tick. If RTG decay is enabled, it will be increased to 300 power/tick, but each will have a lifespan of 194,400 ticks, computing to 2.7 IRL hours, with a stated in-game lifespan of 4 days and half an hour. They decay to Mercury pellets. This also means it will make 58,320,000 power in total over that time.

Trivia

 * Gold-198 decays into stable Mercury due to β- decay.