Steam generator designs, instrumentation and protection

A valuable comprehensive survey of the design of steam generators for LMRs (and other types of reactor) is given by Mitenkov et al [6.1]. They include summaries of the steam generator dengn parameters for many of the worid s fast reactors and information on performance. 

Steam cycle for recirculating boiler with reheat (Feed heating system not shown) 

Stresses due to differential expansion between different tubes have to be kept within acceptable limits. If the tubes have bends this presents little difficulty, but if they are straight it implies close limits on the tube temperatures, both during steady operation and in startup, shutdown, and operational tran ents. For ferritic tubes the length-averaged temperature differences between tubes have to be kept below about 10 K, corresponding to axial stresses of about 20 MPa. This means that the tube bundle has to be designed very carefully to ensure uniform flow patterns and heat transfer conditions, on both the shell and tube sides. 

The principal feature of this approach is to monitor the interface between the two walls of the tube continuously for the presence of either steam or sodium. This would possibly be done by providing a system of small flow passages in the interface, into which any leaking steam or sodium would pass. The network of passages would then be connected to a sensitive monitoring system. It would be necessary to show that the passages would always be open, and to provide a fml-safe monitoring system. 

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