The Fukushima accident hasn’t ended yet- in fact, it may have only just begun. The melt-through of the nuclear reactors is only a small part of the challenge. More importantly, there are used fuel storage pools at the power plant- and one of them is precariously close to collapsing.
In particular, the storage pool at reactor 4 is only an earthquake or typhoon away from collapse. Reactor 4 has 1097 tons of volatile fuel inside it. If the pool collapses, and the water escapes, this fuel will combust into a nuclear fire that will be impossible to put out. It will make the Springfield tire fire pale in comparison.
What does this all mean? Well, Japan will be toast, and people living on the West Coast of North America are at serious risk of having to evacuate. Millions of people will most probably die. The world will see a catastrophe at a scale that has never been previously imagined (outside of science fiction of course).
How likely is this to happen? Quite likely. In fact, there was a major typhoon in Japan only a few weeks ago- and, it looks like there has been significant damage to reactor 4. Here’s a picture of the before & after: