Except that "Fukushima Dai-ichi No.1 Reactor does not have a concrete containment dome. This reactor was built before the now familiar reinforced concrete dome

Except that "Fukushima Dai-ichi No.1 Reactor does not have a concrete containment dome. This reactor was built before the now familiar reinforced concrete dome became mandatory for most reactors. Instead, the reactor has a much smaller steel containment vessel around the reactor vessel." This was from a Slashdot comment, so I trust it about equally to a newly minted blog with only a single post: http://slashdot.org/comments.pl?sid=2033910&cid=35463272 http://slashdot.org/comments.pl?sid=2033910&cid=35463272 Someone with more knowledge of nuclear power history could surely cross reference the dates here for us and confirm/deny the existence of the 3rd containment layer: Fukushima Daiichi Unit 1 - 439 MWe BWR, 1971 - Automatically shut down - Water level decreasing - Pressure release implemented - Explosion observed - Containment believed intact - Seawater injection has started - Radiation levels did not rise after explosion Unit 2 - 760 MWe BWR, 1974 - Automatically shut down - Water level lower but steady - Preparations for pressure release Unit 3 - 760 MWe BWR, 1976 - Automatically shut down - Preparations for pressure release Unit 4 - 760 MWe BWR, 1978 - Shut for periodic inspection Unit 5 - 760 MWe BWR, 1978 - Shut for periodic inspection Unit 6 - 1067 MWe BWR, 1979 - Shut for periodic inspection