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Some older reactors also have IC systems, including Fukushima Dai-ichi reactor 1, however their water pools may not be as large. Under normal conditions, the IC system is not activated, but the top of the IC condenser is connected to the reactor's steam lines through an open valve.
The Reactor Protection System (RPS) is a system, computerized in later BWR models, that is designed to automatically, rapidly, and completely shut down and make safe the Nuclear Steam Supply System (NSSS – the reactor pressure vessel, pumps, and water/steam piping within the containment) if some event occurs that could result in the reactor entering an unsafe operating condition.
To cool the reactor, operators resorted to the plant's Emergency core-cooling systems (ECCS), including the isolation condensers, and the High Pressure Coolant Injection systems (HPCI). According to NHK, the isolation condenser system had not been activated in the previous 40 years, and no one present had ever witnessed its operation. [19]
The Isolation cooling system is a defensive system against a condition known as station blackout. This system is not part of the ECCS and does not have a low coolant accident function. For pressurized water reactors, this system acts in the secondary cooling circuit and is called Turbine driven auxiliary feedwater system.
Fukushima report: Key points in nuclear disaster report - An outline of key quotes, findings and recommendations from the 88-page executive summary of the Nuclear Accident Independent Investigation Commission's report, as provided by the BBC, 5 July 2012; Webcam Fukushima nuclear power plant I, Unit 1 through Unit 4
Another example was the Isolation Condenser system, which relied on the principle of hot water/steam rising to bring hot coolant into large heat exchangers located above the reactor in very deep tanks of water, thus accomplishing residual heat removal. Yet another example was the omission of recirculation pumps within the core; these pumps were ...
The Fukushima nuclear accident was a major nuclear accident at the Fukushima Daiichi Nuclear Power Plant in Ōkuma, Fukushima, Japan, which began on 11 March 2011. The proximate cause of the accident was the 2011 Tōhoku earthquake and tsunami , which resulted in electrical grid failure and damaged nearly all of the power plant's backup energy ...
In events where the reactor coolant pressure boundary remains intact, the Isolation Condenser System (ICS) is used to remove decay heat from the reactor and transfer it outside containment. The ICS system is a closed loop system that connects the reactor pressure vessel to a heat exchanger located in the upper elevation of the reactor building.