Intensely radioactive water from reactor Unit 2 is filling a nearby tunnel faster than workers can empty it, and radioactive levels of seawater near the plant increased sixfold following an aftershock on Saturday.
Tuesday's explosion at the No. 2 reactor in the Fukushima complex, 150 miles north of Tokyo, for the first time raised the possibility that the key containment structure of the unit, which protects the reactor vessel and keeps dangerous radioactive materials from leaking out, had been damaged.