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
Reactor protection system Reactor protection system A reactor protection system (RPS) is a set of nuclear safety components in a nuclear power plant designed to safely shut down the reactor and prevent the release of radioactive materials. The system can "trip" automatically (initiating a scram), or it can be tripped by the operators. Trips occurs when the parameters meet or exceed the limit setpoint. A trip of the RPS results in full insertion (by gravity in pressurized water reactors or high-speed injection in boiling water reactors) of all control rods and shutdown of the reactor. Some of the measured parameters for US pressurized