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,
MIT Nuclear Research Reactor boron-stainless steel blade-type control rods and one aluminum with cadmium control rod which can be placed on automatic control. Light water flows upwards through the core and a tank of heavy water surrounds the core. A wall of dense concrete that serves as shielding surrounds the tank of heavy water. The maximum coolant temperature is 55 degrees Celsius. The light water and heavy water are cooled using forced circulation through heat exchangers to a secondary coolant system. The heat from the reactor is ultimately dissipated to the atmosphere via the secondary cooling system using two modular Tower Tech cooling towers