Greater Australium

Greater Australium (Ayerite) is an isotope of Australium. Like it, it is fully stable and emits no radiation, despite being quite fissile.

Production
Ayerite makes up ~16.6% of Australium and can only be extracted from it using the SILEX.

Uses
Ayerite is used to make the strong fuel Highly Enriched Australium Fuel for the RBMK.

Trivia

 * Given its only fission products are stable Gold and Gold-198 (which is also quite unusual), we can estimate its atomic mass to be ~∓395.
 * This is a mass difference of ~∓21 compared to Lesser Australium. Given this and the wildly different melting points of the two, it is possible they're actually different elements entirely.