A Study on Onset of Liquid Entrainment in Low Pressure Depressurization System of Advanced Passive PWR

[+] Author and Article Information
Jun Liao

Westinghouse Electric Company LLC, Cranberry Twp, PA 16066, USA

Katsuhiro Ohkawa

Westinghouse Electric Company LLC, Cranberry Twp, PA 16066, USA

William L. Brown

Westinghouse Electric Company LLC, Cranberry Twp, PA 16066, USA

Richard Wright

Westinghouse Electric Company LLC, Cranberry Twp, PA 16066, USA

1Corresponding author.

ASME doi:10.1115/1.4042796 History: Received September 18, 2018; Revised January 16, 2019


The low pressure depressurization system (LPDS) of advanced passive PWRs is designed to provide depressurization of the reactor coolant system during a small break loss-of-coolant accident (LOCA). The liquid entrainment to the LPDS is important to the safety case of the advanced passive PWRs due to the significant increase in the pressure drop and the depressurization rate vs. mass loss characteristics. The existing experimental researches on the liquid entrainment at LPDS have been reviewed and the intermittent entrainment mechanism and continuous entrainment mechanism are identified. The intermittent entrainment is closely related to the flow regime transition from the horizontal stratified flow to the intermittent flow in the hot leg where the LPDS port is located. The horizontal stratification model previously developed for the FULL SPECTRUM LOCA evaluation model has been assessed against the entrainment onset data in the available LPDS entrainment experiments, i.e., the ATLATS air-water experiment, the ADETEL air-water and steam-water entrainment experiments, and the full scale FATE air-water experiment. The prediction matches the measure data well especially in the full scale FATE experiments. The comparison results also confirmed the scalability of the horizontal stratification model with the applicability of the horizontal stratification criterion to the full scale PWR condition. The uncertainty factors that impact the de-pressurization system entrainment onset are discussed for the future improvements. This work provides the direction to accurately model the entrainment onset for LPDS and improve the simulation of LOCA in advanced passive PWRs.

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