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Sun D.C.,Xian University of Science and Technology | Zhang J.,Xian University of Science and Technology | Xiang Y.,Xian University of Science and Technology | Tian W.X.,Xian University of Science and Technology | And 3 more authors.
Annals of Nuclear Energy | Year: 2015

Tee branches are widely used in nuclear power plants for varying purposes. The tee branch is adopted by the fourth stage Automatic Depressurization System (ADS-4) in Westinghouse AP600/AP1000 to depressurize the primary loop during the small break loss of coolant accident (SBLOCA). However, large amount of coolant will be entrained simultaneously through the ADS-4 branch which poses the threat of core uncovering and melting. Visualization experiments with double-end gas inlets were conducted to investigate the ADS-4 tee branch entrainment phenomena in AP1000. Entrainment process were recorded by high speed camera and analyzed in detail. The onset of liquid entrainment and entrainment rate data were obtained and compared with existing data and correlations, and discrepancies were found in the comparison due to the difference of test section geometric configuration. The gas flow rate has little effect on the branch quality at the same dimensionless gas chamber height in entrainment rate tests. The entrainment frequency was also studied. The test data reveal that the entrainment period decreases rapidly with the increase of entrainment rate in low range of the entrainment rate, and gradually stabilizes in high range of the entrainment rate. © 2014 Elsevier Ltd. Source


Xiang Y.,Xian University of Science and Technology | Wu Y.W.,Xian University of Science and Technology | Sun D.C.,Xian University of Science and Technology | Sun D.C.,Nuclear Power Institute of China | And 4 more authors.
Progress in Nuclear Energy | Year: 2016

The fourth stage Automatic Depressurization System is an important passive safety feature in Westinghouse AP1000 which enables controlled depressurization of reactor coolant system in small break LOCA. However, large amount of coolant can be carried to the containment via the ADS-4 branch entrainment and the upper plenum entrainment during the depressurization process, which poses great threats to core uncovering and melting. The automatic Depressurization and Entrainment TEst Loop (ADETEL) modeled after AP1000 with a scaling ratio of 1:5.6 was constructed to investigate the entrainment and depressurization behavior after the actuation of ADS-4 valves. The entrainment and depressurization features were investigated under different initial pressure, mixture liquid level in the pressure vessel and heating power. The entrainment deposition effect of the reactor internals was also investigated. The test data reveals that large amount of water are entrained through the ADS-4 branch line within a short period of time. The liquid entrainment rate and the reduced rate of the mixture liquid level in the pressure vessel increase with the initial system pressure. It is notable that the core uncovery was experienced when the initial pressure was set to 0.5 MPa in current experimental conditions. The reactor internals have little effect on the entrained mass and the mixture liquid levels in the pressure vessel. © 2016 Elsevier Ltd. All rights reserved. Source


Sun L.,State Nuclear Power Technology Randnter | Han W.,CAS Institute of Engineering Thermophysics | Jin H.,CAS Institute of Engineering Thermophysics
Applied Thermal Engineering | Year: 2015

This study proposes a hybrid refrigeration system activated by mid/low-temperature sensible heat source with ammonia-water (NH3-H2O) binary mixture as working fluid. The heat source is utilized in cascade in the hybrid system. This heat source is used to generate a superheated NH3-H2O mixture vapor, which is used successively in the power generation and compression subsystem and in the absorption and rectification subsystem to produce refrigerant vapor. Energy and exergy analysis results show that the Coefficient Of Performance, System Coefficient Of Performance, and exergy efficiency of the proposed system in the base case are 0.722, 0.485, and 23.1%, respectively. Effects of turbine inlet pressure, turbine outlet pressure, and solution concentration in the power generation subsystem on system performance are examined. This study provides a new refrigeration method to effectively utilize mid/low-temperature sensible heat. © 2015 Elsevier Ltd. All rights reserved. Source


Sun D.C.,Xian University of Science and Technology | Tian W.X.,Xian University of Science and Technology | Qiu S.Z.,Xian University of Science and Technology | Su G.H.,Xian University of Science and Technology | And 3 more authors.
Progress in Nuclear Energy | Year: 2014

ADS-4 is an important passive safety feature in AP1000 design which provides a controlled depressurization. In this paper, reduced diameter and height scaling analysis with identical fluid properties was conducted on AP1000 ADS-4 blowdown and depressurization process. The scaling analysis consisted of ADS-4 branch line entrainment scaling, system depressurization scaling and upper plenum entrainment scaling. Reasonable dimensionless criteria of related thermal hydraulic phenomena were chosen and developed by analyzing conservation equations. Experimental geometric dimensions and operating conditions for the scaled test facility were obtained. © 2014 Elsevier Ltd. All rights reserved. Source


Sun D.C.,Xian University of Science and Technology | Xiang Y.,Xian University of Science and Technology | Tian W.X.,Xian University of Science and Technology | Liu J.C.,Xian University of Science and Technology | And 3 more authors.
Progress in Nuclear Energy | Year: 2015

Upper plenum liquid entrainment can reduce the coolant inventory in the reactor pressure vessel and poses great threats to core uncovering and melting in the accident conditions. To make up for the de ficiency of upper plenum entrainment database, the Automatic Depressurization and Entrainment TEst Loop (ADETEL) was constructed and upper plenum entrainment experiments were conducted. The test matrix was designed with various variables to investigate the upper plenum entrainment comprehensively. Entrainment phenomena and test data were obtained and analyzed. The entrainment deposition effect of reactor internals was also investigated. The test results indicate that the steam flow rate has little on the entrainment rate under stable experimental conditions. The entrainment rate decreases dramatically with the mixture liquid level in the pressure vessel when the liquid level drops below the hot leg elevation. The entrainment rate is promoted after the installation of reactor internals due to the increase of steam velocity in the upper plenum. Huge discrepancy exists between the test data and Kataoka and Ishii's (1984) pool entrainment model in the near surface region suggesting that the upper plenum entrainment is mainly dominated by side branch entrainment mechanism which is different from the pool entrainment mechanism. © 2014 Elsevier Ltd. All rights reserved. Source

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