Emergency core cooling systems

The design and operation of the decay heat removal system, including the 

The main function of the emergency core cooling system is to inject water into the RCS to remove heat from the core in the event of design basis accidents. 

In some designs, the emergency core cooling system also fulfils other functions such as  

The emergency core coohng system may interface with the following 

The number and type of isolation devices should be determined on the basis of the following considerations  

Assessments should be made, on the basis of deterministic criteria supplemented by risk informed considerations, of the behaviour of passive components (e.g. check valves in discharge lines from accumulators or core make-up tanks) to ensure that their reliability is commensurate with their safety importance. 

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Safety. A large inventory of radioactive fission products is present in any reactor fuel where the reactor has been operated for times on the order of months. In steady state, radioactive decay heat amounts to about 5% of fission heat, and continues after a reactor is shut down. If cooling is not provided, decay heat can melt fuel rods, causing release of the contents. Protection against a loss-of-coolant accident (LOCA), eg, a primary coolant pipe break, is required. Power reactors have an emergency core cooling system (ECCS) that comes into play upon initiation of a LOCA. 

A fire in either of two critical areas would disable all front line and emergency core cooling systems, but not affect confinement isolation and effluent filtration. 

Systems covered include primary, secondary and emergency core cooling systems, control rod, refueling, scram, electrical power, and lube oil, airsupply, battery supplies. 

Heat Transfer in Emergency Core Cooling Systems 287... 

Severe emergency core cooling system criteria require that the builders of water reactors increase the linear feet of fuel in the reactor core for the same power in order to reduce LOCA (loss-of-cooling accident) fuel temperatures. In the unit described here, an assembly with a 16 x 16 fuel rod array of smaller diameter rods is used in the same assembly envelope that was occupied by a 14 x 14 assembly in earlier designs. This results in a maximum linear heat rate decrease in the assembly of about 25%. 

Emergency core cooling system consists of two trains. Each train meets the single failure principle. System includes high and low pressure sub-system. High-pressxue subsystem includes passive (hydro-accumulators) and active pumps and water storage tanks) features for water injection in reactor. Low-pressure sub-system ensures returning a condense accumulated in containment, into the reactor by recirculation pumps. 

There did not appear to be an emergency core cooling system... 

An emergency core cooling system together with a suppression system was provided... 

Emergency core cooling system (ECCS) disconnected. Apparently this is not necessary for the turbo-alternator power rundown test as planned... 

Apart from differences of approach between world regions, in this period of time and in all the countries with nuclear reactors, the systems installed in the plants according to the requirements of the safety bodies and having the sole purpose of accident mitigation, were frequently the subject of heated debates in particular, the emergency core cooling systems and the containment systems were often discussed. 

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