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| AP600 Reactor Coolant Pumps The
AP600 reactor coolant system (RCS) employs high inertia, high reliability, low maintenance
canned motor pumps for circulating primary reactor coolant through the reactor core,
piping, and steam generators. Two pumps are mounted directly in the channelhead of each
steam generator. This allows the pumps and steam generator to use the same structural
support, greatly simplifying the support system and providing more space for pump and
steam generator maintenance. The combined steam generator/pump vertical support is a
single column extending from the floor to the bottom of the channelhead. |
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| Large Operating Experience Base Inverted
canned motors have been in operation for over 25 years in fossil boiler circulation
systems with better operating reliability than upright units because the motor cavity is
self-venting into the pump casing, avoiding the potential for gas pockets in the bearing
and water regions. Approximately 1300 units have been built and placed into service. The
pumps are integrated into the steam generator channelhead in the inverted position.
The advantages of this pump design are significant. The auxiliary fluid systems
needed to support a canned motor pump are much less complex than those needed for a shaft
seal type pump. The canned motor pump is more tolerant of off-design conditions than shaft
seal pumps, and inherently reduces the potential for small loss-of-coolant accidents
(LOCAs) by eliminating the shaft seal. The integration of the pump suction into the bottom
of the steam generator channelhead eliminates the crossover leg of coolant loop piping;
reduces the loop pressure drop; simplifies the foundation and support system for the steam
generator, pumps, and piping; and eliminates a potential of core uncovery during a small
LOCA. |
      
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