Abstract
A numerical study is conducted for performance analysis and secondary side screw-type tube inlet orifice design of a once–through steam generator (OTSG). Various tube plugging conditions and power levels are considered, and the secondary coolant flow rate is adjusted to maintain a constant thermal power. Comprehensive numerical solutions are acquired to evaluate the OTSG thermal–hydraulic performance and minimum orifice length under various operating conditions. The OTSG performance is analyzed according to the tube plugging condition in terms of the OTSG thermal power, steam outletsuperheat degree, and secondary coolant pressure drop. The results obtained show that a constant thermal power canbe maintained by properly adjusting the secondary coolant flow rate with a variation ofthe steam outlet superheat degree and secondary coolant pressure drop when the OTSG operates at high power level. The required minimum orifice length to suppress the flow oscillation below the allowablelevelis evaluated. The lowest power level results in the highest minimum orifice length, and non-plugging condition provides a limiting case for the orifice length criterion.
Highlights
An integral-type pressurized water reactor employs once-through steam generators (OTSGs) owing to its advantages in compactness and simplicity of flow path arrangement [1]
When the OTSG begins its first operation without tube plugging, the operating point is located on the red line of SG condition-1
The effect of tube plugging on the thermal-hydraulic performance of an OTSG and on screw-type tube inlet orifice design has been investigated
Summary
An integral-type pressurized water reactor employs once-through steam generators (OTSGs) owing to its advantages in compactness and simplicity of flow path arrangement [1]. Increasing the system pressure, and increasing the inlet hydraulic resistance in particular, are stabilizing, whereas increasing the outlet hydraulic resistance and increasing the pressure loss in the twophase region are destabilizing [2] Because such density-wave oscillations are suppressed by the strong stabilizing effect of the added single-phase resistance, it is necessary to install an orifice inside the tube at the entrance region for flow stabilization [3]. For this reason, a screw-type tube inlet orifice was introduced and detailed orifice design was implemented for the MRX OTSG The secondary coolant flow rate is adjusted for constant thermal power operation and the corresponding orifice length is evaluated
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