I think that when people casually pronounce a bet like that, they generally mean even odds. If they meant something else they'd likely say so explicitly.
The way it usually goes with anti-nuclear activists when they make pronouncements like this is as follows:
1. It will take at least 15 years and cost 100 gazillion dollars
2. Are you sure?
3. Yes, this is 100% what will happen. It is 100% certain, because nuclear does not and cannot work.
4. OK, then let's put some money where our mouths are. Your 100% certainty means you should be willing to give me infinite odds, because any money I put up is automatically yours. Completely risk free income for you. But I am happy to reduce those odds to just 100:1, so I put up $100 and you put up $10.000.
6. <crickets>
If those reactors are so fantastic, surely you wouldn't hesitate at a chance to get some free money - no matter how little?
Something not being 100% certain does not imply the opposite being 100% certain.