Emergency Core Cooling System (ECCS)
An emergency core cooling system comprises a series of systems that are designed to safely shut down a nuclear reactor during accident conditions. Under normal conditions, heat is removed from a nuclear reactor by condensing steam after it passes through the turbine and by conversion to mechanical work. In a boiling water reactor, condensed steam (water) is fed back into the reactor. In a pressurized water reactor, it is fed back through the heat exchanger. In both cases, this keeps the reactor core at a constant temperature. During an accident, the condenser is not used, so alternate methods of cooling are required to prevent damage to the nuclear fuel.
These systems allow the plant to respond to a variety of accident conditions, and additionally introduce redundancy so that the plant can be shut down even with one or more subsystem failures.
In most plants, ECCS is composed of the following systems:
Read more about this topic: Nuclear Reactor Safety Systems
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