Fukushima Daiichi nuclear disaster (Unit 3 Reactor) 13 March an official of the Japan Nuclear and Industrial Safety Agency (NISA) told at a news conference that the emergency cooling system of Unit 3 had failed, spurring an urgent search for a means to supply cooling water to the reactor vessel to prevent a meltdown of its reactor core. At 05:38 there was no means of adding coolant to the reactor, owing to loss of power. Work to restore power and to vent excessive pressure continued. At one point, the top three meters of the uranium/mixed oxide (MOX) fuel rods were not covered by coolant. At 07:30 JST,
Nuclear reactor safety system below a threshold. This system is normally the first line of defense for a reactor since it can be used while the reactor vessel is still highly pressurized. The Automatic Depressurization System (ADS) consists of a series of valves which open to vent steam several feet under the surface of a large pool of liquid water (known as the wetwell or torus) in pressure suppression type containments (typically used in boiling water reactor designs), or directly into the primary containment structure in other types of containments, such as large-dry or ice-condenser containments (typically used in pressurized water reactor designs). The