Plastic may be the issue.
Do you have a metal lid? if not then the plastic box is 'Insulating' your setup. you need to maximise your conductivity thereby increasing your steep temperature gradient. your environment probably isn't supersaturated enough, and I might add, try using methanol, or...
You should watch the documentary "pandoras promise" and the BBC doc horizon "Is nuclear power safe", the BBC one interviews a Russian scientist who compiled the doses v effects. i believe his research is publicly available.
One thing i will add, interestingly people still live in Chernobyl, and...