As a result of its extreme rarity in nature, most francium is synthesised in the nuclear reaction 197Au + 18O → 210Fr + 5 n, yielding francium-209, francium-210, and francium-211.
Akibat kelangkaannya di alam yang ekstrem, sebagian besar fransium disintesis dengan reaksi nuklir 197Au + 18O → 210Fr + 5 n menghasilkan fransium-209, fransium-210, dan fransium-211.