Sung Uk Ryu

Experimental study on the direct contact condensation of steam jet in the passive safety injection tank

ABSTRACT The direct contact condensation and subsequent thermal mixing by the injected steam jet onto a quiescent coolant inside a tank were examined experimentally to simulate the phenomena in passive safety injection systems. Specifically, the influence of the steam injection velocity was studied. Even though the total flow rate of injected steam was unchanged, the pressure inside the tank increased quickly at the larger nozzle diameter. Additionally, at a larger nozzle diameter, the thickness of the thermal mixing zone decreased because the amount of direct contact condensation decreased. For the in-depth study on the role of the nozzle size for the thermal mixing, the particle image velocimetry method was used to understand the flow field of water inside the tank. The visualization results demonstrated the formation of a flow field in the coolant due to the expansion and contraction of the steam–air mixture boundary. Furthermore, the thermal mixing zone was found to be closely related to the penetration depth. Finally, a variety of penetration models were examined and compared against the experimental observation. The correlations based on the steam condensation approach under-predicted the penetration depth, whereas the approach that considers the momentum of non-condensable gas gave the reasonable prediction capability.

Experimental Study of SBLOCA Simulation of Safety-Injection Line Break with Single Train Passive Safety System of SMART-ITL

An experimental study of the thermal-hydraulic characteristics of passive safety systems (PSSs) was conducted using a system-integrated modular advanced reactor-integral test loop (SMART-ITL). The present passive safety injection system for the SMART-ITL consists of one train with the core makeup tank (CMT), the safety injection tank, and the automatic depressurization system. The objective of this study is to investigate the injection effect of the PSS on the small-break loss-of-coolant accident (SBLOCA) scenario for a 0.4 inch line break in the safety-injection system (SIS). The steady-state condition was maintained for 746 seconds before the break. When the major parameters of the target value and test results were compared, most of the thermal-hydraulic parameters agreed closely with each other. The water level of the reactor pressure vessel (RPV) was maintained higher than that of the fuel assembly plate during the transient, for the present CMT and safety injection tank (SIT) flow rate conditions. It can be seen that the capability of an emergency core cooling system is sufficient during the transient with SMART passive SISs. §이 논문은 대한기계학회 2015 년도 에너지 및 동력 부문 춘계학술대회 발표논문임. † Corresponding Author, rsu@kaeri.re.kr C 2016 The Korean Society of Mechanical Engineers 류성욱 · 배황 · 유효봉 · 변선준 · 김우식 · 신용철 · 이성재 · 박현식 166 형 피동로) CLOF : Complete Loss of RCS Flowrate (원자로냉각재유량완전상실사고) CMT : Core Makeup Tank (노심보충탱크) JAEA : Japan Atomic Energy Agency (일본원자력 연구개발기구, JNC 와 JAERI 가 통합된 기관) LSTF : Large Scale Test Facility (일본 대형 비정상시험장치) NPIC : Nuclear Power Institute of China (중국원자력연구소 = 중국 핵동력연구 설계원) PRHRS : Passive Residual Heat Removal System (피동잔열제거시스템) PSS : Passive Safety System (피동안전계통) ROSA : Rig of Safety Assessment (일본 경수로 냉 각재상실사고 모의실험장치) SBLOCA : Small Break Loss-of-Coolant Accident (소형냉각재상실사고) SMART : System Integrated Modular Advanced ReacTor (중소형일체형 원자로) SIT : Safety Injection Tank (안전주입탱크)

Development of Lift-Off Diameter Model of Bubbles Generated on Horizontal Tube

In this study, the theoretical correlation for the lift-off diameter of bubbles generated on a horizontal tube is proposed. A force balance analysis in the direction normal to the heated surface at the moment of the bubble lift-off was performed to develop the model. According to the developed model, the bubble lift-off diameter depends strongly on the azimuthal position of the horizontal tube, the relative velocity between a bubble and surrounding liquid, the properties of the bubble, and the liquid. The developed model can be applicable to define the sub-model of wall heat flux partitioning for natural and forced convective boiling.Copyright