Abstract
After a short review of the phenomenon of static instability also called excursive instability - an overview of those specific features of the THTR steam generator follows. which must be observed when taking actions to prevent flow instabilities. These features are in detail: restricted number of tube penetrations, tube arrangement within the helical bundle, downhill flow, part load conditions, temperature limits for the ferritic/austenitic material transition joint. Then the required stabilizing pressure drops and the means provided to produce these pressure drops are discussed: orifice in the single tube, fixed orifice in the system tube, adjustable orifice in the system tube.
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