Nature.com has a post up on their newsblog comparing the Fukushina & Cherynobyl disasters to one another. Geiff Brumfiel writes:

The bottom line here is that Fukushima and Chernobyl are comparable, and a comparison really helps underscore the differences. Fukushima's heavy containment vessels limited the spread of some dangerous isotopes, but the coastal location makes marine contamination a much bigger issue than it ever was for Chernobyl. The latest maps suggest that there will be a permanent exclusion zone to the northwest of Fukushima, but it will likely be quite a bit smaller than the one at Chernobyl. The size comparison graphic that accompanies the article gives a nice visual perspective.