I certainly agree that even if there is no further damage (which seems unlikely to me) it will be ten years or more before the radiation damage at the site and in the downwind area is mitigated. Some areas may need to be permanently classified as a "dead zone."

That depends not just on WHAT has been emitted but also on HOW MUCH of it there is. It doesn't look from what I've read that the emissions to date require measures anywhere near that drastic.