The break, at the No. 3 reactor unit, worsened the already perilous conditions at the plant, a day after officials said the containment vessel in the No. 2 reactor had also cracked…

The vessel that possibly ruptured on Wednesday had been seen as the last fully intact line of defense against large-scale releases of radioactive material from the stricken reactor, but it was not clear how serious the possible breach might be. The implications of overheating in the fuel rod pool, which is also at the at the s No. 3 reactor, seemed equally dire…

Such is the growing international alarm about the nuclear crisis that France announced it was urging its citizens living in Tokyo to head to safer areas or to leave the country — apparently the most urgent instruction offered by foreign countries that so far had largely limited their advisories to simply avoid non-essential travel.