Safety-related operating and maintenance considerations in a modular steam generator: PHENIX operating experience and straight-tube modular steam generator proposal for future French LMFBRs

The Phenix steam generator has logged over 45000 operating hours to date; its modular design provides a high degree of flexibility with regard to operating and maintenance requirements. This paper discusses these advantages as illustrated by the solution to a recent problem concerning flaws discovered in certain reheater modules. Based on this experience, the authors present a straight-tube modular steam generator proposal that applies the major Phenix design options to future high-power LMFBR plants. Among the safety considerations related to steam generator design, protection, surveillance and maintenance are the following: modular arrangement; straight tubes with no weld seams in the evaporation zone; small-diameter tubes that limit the potential leakage flow rate in the event of a tube failure; expansion bends on each tube to accommodate the differential expansion among the tubes, or between the tubes and the steam generator shell; tube wall inspection provisions; continuous monitoring for water leakage into the sodium