Nuclear safety and security called a nuclear meltdown. After shutting down, for some time the reactor still needs external energy to power its cooling systems. Normally this energy is provided by the power grid to which that plant is connected, or by emergency diesel generators. Failure to provide power for the cooling systems, as happened in Fukushima I, can cause serious accidents. Nuclear safety rules in the United States "do not adequately weigh the risk of a single event that would knock out electricity from the grid and from emergency generators, as a quake and tsunami recently did in Japan", Nuclear Regulatory Commission officials
Nuclear reactor heat removal total heat produced in the nuclear reactor is: formula_5 where formula_6 is the mean neutronic flux and V is the fuel volume (normally measured in formula_7). Recovery of this amount of heat is achieved by using cooling fluids whose temperature at the entrance to the reactor channel formula_8 will increase with the distance traveled in the channel. The thermal balance of the channel is expressed by the relationship: formula_9 where formula_10 is the flow rate of the cooling agent, formula_11 is the specific heat at constant pressure, formula_12 is the increase in the temperature of the fluid after passing a