Steam generator heating tubes, leak detection

Another ongoing item on the steam generator safety is a leak detection system development for the double wall tube that is being developed for the steam generator installed in a primary heat transport system of a future FBR plant. Basic performance data was obtained for an outer tube leak detection system to detect helium leak into sodium. An inner tube leak detection system using infrared rays is also under developing to quickly detect humidity at gas plenums. 

The second method provides a double barrier within the steam generator itself. The double barrier has conventionally been in the form of concentric tubes and double tube sheets with the intermediate space filled with a static third fiuid to assist in the transfer of heat. The third-fluid system was equipped to detect any leaks which might occur in either of the single barriers. Under the doublewall philosophy as originally developed, if a leak occurred in either barrier, the heat exchanger was taken out of service for repair or replacement. 

The nuclear heat supply system generates heat in the reactor core and produces steam in the IHTS. The IHTS SG is composed of a helical coil counterflow heat exchanger, startup recirculation tank and pump, leak detection system, and isolation valves. Intermediate sodium flows on the shell side of the helical coil tubes, through which water flows to produce superheated steam. Two reactor SGs feed one turbine island to form a power block. 

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