Transient Hydraulic Response of a PWR Steam Generator to a Feed Water Line Break

摘要

The transient hydraulic response of a PWR SG to the blowdown-decompression caused by a feed water pipe break has been simulated numerically using a commercial CFD code. The present numerical approach has been validated by comparing the CFD analysis results to the simplified calculations using lumped model in terms of the area-averaged discharging velocity of the flashing flow and the pressure wave velocity. Based on the present CFD analysis results, it is seen that a FWLB may result in excessive disastrous transient hydraulic loading on the SG internal structures and tubes near the feed water inlet nozzle due to the significant pressure changes (pressure wave with very high amplitude) and abruptly increased tube-to-tube gap velocity of water near the feed water nozzle. These situations may challenge the structural integrity of the SG internal structures including tubes. Thus, it is emphasized that SG should be designed and manufactured by taking into account the FWLB-induced transient hydraulic load and flow situation in the SG obtained from a conservative analysis.