at 12:33 jst on 13 march, the chief spokesman of the japanese government, yukio edano said hydrogen gas was building up inside the outer building of unit 3 just as had occurred in unit 1, threatening the same kind of explosion. at 11:15 jst on 14 march, the envisaged explosion of the building surrounding reactor 3 of fukushima 1 occurred, owing to the ignition of built-up hydrogen gas. the nuclear and industrial safety agency of japan (nisa) reported, as with unit 1, the top section of the reactor building was blown apart, but the inner containment vessel was not breached. the explosion was larger than that in unit 1 and felt 40 kilometers away. pressure readings within the reactor remained steady at around 380 kpa at 11:13 and 360 kpa at 11:55 compared to nominal levels of 400 kpa and a maximum recorded of 840 kpa. water injection continued. dose rates of 0.05 msv/h were recorded in the service hall and of 0.02 msv/h at the plant entrance.