I wonder how far it will go though... Chernobyl actually really "exploded" and thus in contrast to what the officials say there is only very little radioactive material within the chernobyl sarcophagus (they say there is 97% left inside, but you can walk inside with little protection, check youtube - there are many videos of the inner sanctum of the sarcophagus ... there is only little left. the rest is spread around the ukraine, russia and europe mostly). Most of the material was pushed into the air when it exploded.
As there are no real (trustable) sources in terms of the Japanese nuclear catastrophe it wouldn't suprise me if there is a complete melt down of No. 3 and no public information available on the real scale of the disaster (e.g. plutonium 235, its byproducts and other radioactive material and spreading across continents and oceans).