A reactor accident such as Fukushima drives 90,000 people out of their houses and businesses and makes a substantial fraction of the land in Japan uninhabitable. If every reactor in Japan were to explode like that, a large fraction of the country would have to abandoned for centuries. Of
Japan just had the most luck ever. (Ancient wind good did help...) During 2 weeks constant winds from the west did drive all fallout over the pacific. Just for one hour there was small dip that contaminated the north west of Fukushima.
A few hours wind from North west and Japan today would we a lonesome country down to Osaka at least. The fallout that went to the pacific was about 20x full loads of a nuclear plant as all the cool down basins did cook over and started to burn ....
Fukushima was at least 10 x worse than Tschernobyl! I did closely follow all radioactivity maps (SAFECAST) over Japan for months. There was a helicopter Landing zone in Haneda (Tokyo) that got highly activated for months because politicians did like to commute by air...