This arrangement means that in the event of an accident in one reactor that triggers the containment system, all the other operating reactors must shut down promptly and remain shut down until the accident unit can be isolated from the containment system and the pressure suppression
capability of the vacuum building can be restored.
The pressure suppression
containment vessel is located under the building and highly radioactive contaminated water generated by the reactor is believed to be accumulated there, TEPCO said, adding, the steam is probably coming from the water.
At approximately 6:00 am on March 15th, an abnormal noise began emanating from nearby Pressure Suppression
Chamber and the pressure within the chamber decreased.