Exchanger shut down procedures

Another serious problem in heat exchangers is corrosion. Severe corrosion can and does occur in tubing and very often with common fluids such as water. Proper material selection based on a full analysis of the operating fluids, velocities and temperatures is mandatory. Very often, heavier gauge tubing is specified to offset the effects of corrosion, but this is only a partial solution. This should be followed by proper start-up, operating and shut-down procedures. 

In the normal operation manual, the reactor decay heat after the reactor shut down is to be removed through the steam generator and the residual heat removal system like the land based PWRs. When this normal procedure is not available due to an accident, the decay heat is removed passively by helps of the EDRS and the CWCS as shown in Fig. 5. The decay heat is transferred from the primary coolant to the water of the containment through the heat exchanger of EDRS, and... 

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