Atomic Collider, Germs tab (same amount of germs as the Radbolts inside the Atomic Collider "contents")
The Germs tab has Surrounded by: 100% dead/cycle, however, the tooltip (for Surrounded by) is saying "...causing germs to multiply". The germs are indeed dying off, not spawning.
The Dying on: 50%/cycle tooltip is correct:
Build Atomic Collider, shoot a radbolt inside it, wait for radiation germs, check Germs tab.