Sung-Jae Yi

Design of the VISTA-ITL Test Facility for an Integral Type Reactor of SMART and a Post-Test Simulation of a SBLOCA Test

To validate the performance and safety of an integral type reactor of SMART, a thermal-hydraulic integral effect test facility, VISTA-ITL, is introduced with a discussion of its scientific design characteristics. The VISTA-ITL was used extensively to assess the safety and performance of the SMART design, especially for its passive safety system such as a passive residual heat removal system, and to validate various thermal-hydraulic analysis codes. The VISTA-ITL program includes several tests on the SBLOCA, CLOF, and PRHRS performances to support a verification of the SMART design and contribute to the SMART design licensing by providing proper test data for validating the system analysis codes. A typical scenario of SBLOCA was analyzed using the MARS-KS code to assess the thermal-hydraulic similarity between the SMART design and the VISTA-ITL facility, and a posttest simulation on a SBLOCA test for the shutdown cooling system line break has been performed with the MARS-KS code to assess its simulation capability for the SBLOCA scenario of the SMART design. The SBLOCA scenario in the SMART design was well reproduced using the VISTA-ITL facility, and the measured thermal-hydraulic data were properly simulated with the MARS-KS code.

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)

Code validation on a passive safety system test with the SMART-ITL facility

ABSTRACT A thermal-hydraulic integral effect test facility, SMART-ITL, was constructed to examine the system performance of SMART, a 330 MWt integral type reactor, and to provide data for validation of related thermal-hydraulic models in the system analysis codes. SMART is equipped with various passive systems such as a passive residual heat removal system (PRHRS), a passive safety injection system (PSIS), and an automatic depressurization system (ADS). The PSIS of SMART is made up of four core makeup tanks (CMTs), four safety injection tanks (SITs), and related piping. Over 10 tests have been performed to investigate the behavior of a single train of a PSIS (a CMT and a SIT) in connection with PRHRSs and an ADS. Using a system analysis code, MARS-KS, we validated the experimental results for a representative test. All geometrical and thermal-hydraulic conditions of SMART-ITL were reflected in the code input construction. Through the validation process, several models, including a break flow model, heat transfer models, and pressure drop models, were examined. Overall, the major system parameters were well reproduced.

An integral effect test of a complete loss of reactor coolant system flow rate for the SMART design using the VISTA-ITL facility and its simulation with the MARS-KS code

ABSTRACT An integral effect test was successfully performed to provide data to assess the capability of the system analysis code to simulate a complete loss of reactor coolant system (RCS) flow rate (CLOF) scenario for the SMART (System-integrated Modular Advanced ReacTor) design. The steady-state conditions were achieved to satisfy initial test conditions presented in the test requirement, its boundary conditions were accurately simulated, and the CLOF scenario in the SMART design was reproduced properly using the VISTA-ITL facility. The natural circulation flow rate in the RCS was about 12.0% of the rated RCS flow rate and the flow rate in the passive residual heat removal system (PRHRS) loop was about 10.6% of its rated value in the early stage of the PRHRS operation. In this paper, the major experimental results of the CLOF test are discussed. The test results were analyzed using the best-estimate system analysis code, MARS-KS, to assess its capability to simulate a CLOF scenario for the SMART design.

Numerical Calculation of Two-Phase Flow Based on a Two-Fluid Model With Flow Regime Transitions

Numerical test and eigenvalue analysis for a two-phase channel flows for energy conversion systems like fuel cells or water electrolysers with flow regime transitions are performed by using the well-posed system of equation that takes into account the pressure jump at the phasic interface. The interfacial pressure jump terms derived from the definition of surface tension which is based on the surface physics make the conventional two-fluid model hyperbolic without any additive terms, i.e., virtual mass or artificial viscosity terms. The four-equation system has three sets of eigenvalues; each of them has an analytical form of real eigenvalues relevant to the sonic speeds with phasic velocities of three typical flow regimes such as dispersed, slug, and separated flows. Further, the eigenvalues for the flow transition regions can also be obtained numerically for smooth calculation of flow regime transitions. The sonic speeds agree well not only with the earlier experimental data but also with those of an analytical model. Owing to the hyperbolicity of this model, we can adopt an upwind method, which is one of the well-known Godunov type upwind methods. A typical example of two-phase flows shows that the present model can simulate the phase separation caused by density difference of two-phase fluids.© 2012 ASME

On the Implementation of Computational Methods for a Hyperbolic Two-Fluid Model

In this study, we focused on the implementation of numerical methods for a 2-fluid system including the surface tension effect in the momentum equations. This model consists of a complete set of 8 equations including 2-mass, 4-momentum, and 2-internal energy conservations having all real eigenvalues. Based on this equation system with upwind numerical method, we first make a pilot 2-dimensional computer code and then solve some benchmark problems in order to check whether this model and numerical method is able to properly analyze some fundamental two-phase flow systems or not.Copyright

Upwind Solutions for Two-Phase Flow Problems Using a Hyperbolic Two-Fluid Model

This study discusses on the implementation of an upwind method for a new 2-dimensional 2-fluid model including the surface tension effect in the momentum equations. This model consists of a complete set of 8 equations including 2-mass, 4-momentum, and 2-internal energy conservation equations having all real eigenvalues. Based on this equation system with upwind numerical method, the present authors first make a pilot 2-dimensional code and then solve some benchmark problems to verify whether this model and numerical method is able to properly solve some fundamental one-dimensional two-phase flow problems or not.Copyright

An Upwind Numerical Method for a Hyperbolic One-Dimensional Two-Fluid Model

This study discusses on the implementation of an upwind method for a one-dimensional two-fluid model including the surface tension effect in the momentum equations. This model consists of a complete set of six equations including two-mass, two-momentum, and two-internal energy conservation equations having all real eigenvalues. Based on this equation system with upwind numerical method, the present authors first make a pilot code and then solve some benchmark problems to verify whether this model and numerical method is able to properly solve some fundamental one-dimensional two-phase flow problems or not.Copyright

On the Analysis of Two-Phase Channel Flow With Flow Regime Transitions for Energy System

Numerical test and eigenvalue analysis for a two-phase channel flows for energy conversion systems like fuel cells or water electrolysers with flow regime transitions are performed by using the well-posed system of equation that takes into account the pressure jump at the phasic interface. The interfacial pressure jump terms derived from the definition of surface tension which is based on the surface physics make the conventional two-fluid model hyperbolic without any additive terms, i.e., virtual mass or artificial viscosity terms. The four-equation system has three sets of eigenvalues; each of them has an analytical form of real eigenvalues relevant to the sonic speeds with phasic velocities of three typical flow regimes such as dispersed, slug, and separated flows. Further, the eigenvalues for the flow transition regions can also be obtained numerically for smooth calculation of flow regime transitions. The sonic speeds agree well not only with the earlier experimental data but also with those of an analytical model. Owing to the hyperbolicity of this model, we can adopt an upwind method, which is one of the well-known Godunov type upwind methods. A typical example of two-phase flows shows that the present model can simulate the phase separation caused by density difference of two-phase fluids.Copyright

Experimental and Analytical Study on the Heat Transfer Characteristics in a Natural Circulation Loop for an Integral Type Reactor

The heat transfer characteristics in a natural circulation loop for an integral type reactor were experimentally investigated by using the VISTA facility and steady-state natural circulation flow rates were acquired for various core powers and feed water flow rates. The experimental data were compared with the predictions from existing correlations of Duffey et al. (1987) and Vijayan et al. (2002). It was shown that Duffey et al. (1987)’s correlation for a two-phase natural flow predicted the experimental data well. Also the experimental data on the natural circulation in the primary loop of the VISTA facility were analyzed by using a best-estimate system analysis code, MARS. The MARS code predicted the overall natural circulation flow characteristics reasonably.Copyright