Don't see any way of succeeding at graphic representation of a silent, invisible, eventually deadly emanation. Too much left-brain in most tries. The modern 'biohazard' symbol is not scary... nor is the ISO radiation sign. 'Skull and bones' is moreso. Many old Hollywood films kept it simple with warning messages posted around territories ... heads on pikes, hanging skulls, that sort of thing. They say 'Enter here and…
I was just having the discussion with my students when discussing icon designs. As a kid I always thought the radiation sign was a fan; was mildly confused by suburbs/towns which had anti-nuclear signs up - what does this place have against fans?
Also, the biohazard symbol was designed to be memorable but meaningless so people could be educated.