Severe Nuclear Reactor Accidents Likely Every 10 to 20 Years, European Study Suggests

Because they say so. Such predictions are worth less than the paper that they are printed on.

No,

I say if only we would be that lucky.

There were 3 accidents of level 7 per 40 years and 400 reactors (not accounting for RBMKs)- Fukushima Dai Ichi 1-3.

With a 10 fold increase in safety in the post-TMI designs (see Fukushima Dai-Ni), that's one per 50,000 reactor year.

So if there are 5000 reactors worldwide, one can expect one accident per 10 years.

Of course 5000 nuclear reactors would pretty much solve ALL coal + hydrocarbon pollution. So it would be a very, extremely good tradeoff.