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[en] The steam condensation on the inside wall of containment and film evaporation on the outside wall of containment are very important phenomena during passive containment cooling system (PCS) heat removal process. The GOTHIC8.0 code was used to simulate condensation and evaporation heat removal processes in this paper. The code prediction results were compared and evaluated based on experimental data of condensation and evaporation tests. The results show that the condensation model in GOTHIC can simulate steam condensation heat transfer process quite well. The film evaporation rate from GOTHIC model is lower than that from evaporation test. Although GOTHIC model is conservative to analyze containment response during design benchmark accident, it is suggested that further work should focus on making code development to better simulate film evaporation phenomenon. (authors)
[en] A transient analysis code TAPIRS was developed to analyze the behavior of the heat pipe cooled space reactor power system based on the SAIRS models. Three typical accidents are analyzed using TAPIRS. The results show that the fuel temperature is below a safe limit under the control drum failure, the AMTEC failure and partial loss of the heat transfer area of radiator. This demonstrates that the reactor system is with the characteristics of self-stabilization ability under accident conditions. (authors)
[en] To increase heat transfer performance of dry cooling system, direct contact heat exchangers were considered. There is no thermal resistance by wall structure and it is easy to get large surface area. On the other hand the conventional system uses fin structure and heat transfer performance is reduced due to thermal conduction in the fins. In most cases, increasing heat transfer performance is able to be obtained by increasing Reynolds number. In this study, many types of direct contact heat exchangers were analyzed and the optimum heat exchanger type having high heat transfer performance and low pressure loss of the system was selected. In summary, the best type for direct contact heat exchanger is falling oil film along vertical strings. It is important to consider not only heat transfer performance of the heat exchanger but also frictional pressure loss. The range of Reynolds number in the direct contact heat exchangers are generally 100 to 10,000. Within this range, whole correlations used for this study are proven, thus the results are reliable. This study shows that straight flow of air on the flat surface is the best option for direct contact heat exchanger. The heat transfer performance on the wavy surface is high due to turbulence, but the frictional pressure loss is much large.
[en] To establish a lunar base, the problem of energy supply needs to be solved first. The nuclear reactor power system has the advantages of high power, long service life and environmental resistance ability. It is an ideal energy solution option for lunar base and other deep space exploration missions. The brief analysis of the current status of energy that can be used for the lunar base was carried out. The design idea of 40 kWe nuclear reactor power system for lunar base was proposed. After the preliminary optimization design, process and overall design parameters of the system were given. Finally, the system scheme was analyzed and demonstrated from the aspects of reactor physics, shielding, thermodynamics and structure. The results show that the system scheme is reasonable and feasible. It can meet the requirements of safety and lifetime. (authors)
[en] PCCS (Passive Containment Cooling System) comprised of heat exchanger tubes were devised for iPOWER (innovative Power Reactor) concept design. To guarantee the cooling performance of the PCCS, the condensation heat transfer needs to be accurately calculated. The relation between diameter of PCCS heat exchanger and condensation heat transfer coefficient has been investigated in the present study and the heat exchanger design was selected based on the JNU (Jeju National University) experiment. A curvature effect correction factor was derived by Popiel and Dehbi used the parameter when proposing his generalized condensation heat transfer coefficient correlations. In this study, the condensation phenomena simulations were performed to derive the curvature effect correction factor applicable to the condensation phenomena. Based on the CFD analysis results, Bird correction factor was selected as a parameter for condensation phenomena. The fitting equation was introduced which shows good agreement with CFD results. The modified correlation can be expected to be applicable as a curvature effect correction factor when deriving generalized condensation heat transfer coefficient correlations. For the further works, as validation of modified curvature effect correction factor, quantitative comparison between the modified curvature effect correction factor and the experimental results of curvature effect on condensation will be conducted.
[en] An open-pool type research reactor (RR) usually adopts a downward forced core flow by a primary cooling system (PCS). During reactor normal operation, the pressure inside the highest pool penetration pipe of the primary cooling system can be lower than the atmospheric pressure, and the outside air will be come into the pipe in case of a pipe rupture accident. If the air enters into the cooling system, air-water mixture flows in the system, and many troubles such as the cooling pump stop or malfunction and the pump flywheel coastdown time decrease can be caused. In this study, conceptual design of an experimental facility for the measurement and analysis of the airwater mixture flow phenomena in the primary cooling system is proposed. Air-inflow test section to simulate a pipe rupture accident is designed to measure the airwater mixture behavior in terms of the pipe rupture sizes, shapes, and directions. At the negative (gauge) pressure condition of the downward forced flow cooling system in a RR, the outside air can enter into the pipe in case of a pipe rupture accident. It is necessary to accurately predict the air ingress phenomena for the safety-to-design against a highest pipe rupture accident in the primary cooling system. In this study, the experimental facility for the measurement and analysis of the air-water mixture phenomena by the air ingress is proposed.
[en] This paper analyze the computational performance of the massive parallel computation. In this paper, the massive parallel computation is introduced to whole core transport calculation, the performance is examined for C5G7 2-D and 3-D problems and for the realistic 3-D core problem. The goal of the massive parallelization in this paper is assign one 3-D node per CPU. The examination shows that the parallel efficiencies are 0.89 and 0.77 for 2-D and 3-D C5G7 problems, and 0.80 for the realistic 3-D core problem. These efficiencies are very good considering the number of CPUs attending the computations. Therefore, it can be concluded that the massive parallel computation works good for the whole core transport calculation. In the parallel efficiency, the CMFD and axial Pn calculation showed poor efficiency, and deteriorates the total efficiency. Therefore, more efficient parallel scheme needs to be developed in the future.
[en] The pressurizer (PZR) heaters are installed in the PZR; the PZR heaters are operating automatically (or manually) to compensate the heat losses due to spray flow, Control Rod Drive Mechanisms (CRDMs), and other insulation thermal transferences. In this study, the PZR spray flow rates are calculated with varying valve opening area, and the amount of heat losses are obtained in each case. Pressure drop calculation for main spray line is conducted for each section. PZR spray control valve is controlled at fully (1), ¾, ⅔, ½, ⅔, and ¼ opening to find the effect on the heat loss as well as Boron concentration difference between PZR and reactor coolant loop. The maximum allowable main spray flow rate will be 100% of allowable flow for fully open spray control valve. The optimum range for main spray flow rate that will satisfy minimum heat loss with Boron concentration equilibrium is recommended from 10% to 45% of allowable flow rate for normal operation.
[en] Highlights: • Historical overview of the development of advanced reactors. • Focus on the Generation IV International Forum and role of international collaboration. • Identification of challenges to be addressed to enable deployment of advanced reactors. - Abstract: This paper provides a historical overview of the development of advanced reactors, with a focus on Generation IV reactors and the unique international cooperative R&D framework that was put in place within the Generation IV International Forum. Drawing on the expertise developed at the Nuclear Energy Agency, the paper analyses the challenges for deploying advanced reactors in future energy markets, including evolving market requirements and economic considerations, regulatory challenges, research infrastructure needs and human resource issues. The paper concludes on the role of nuclear research and innovation to ensure the conditions for successful deployment of advanced reactors and competition with alternative technologies.
[en] Highlights: • An analytical overview on thermal hydraulic characteristics of single-phase for liquid sodium is presented. • Heat transfer characteristics of single-phase liquid sodium should be considered some special issues. • Flow characteristics of single-phase liquid sodium in circular tube are similar to the characteristics of conventional fluid. - Abstract: Single-phase liquid sodium as a kind of ideal coolant is widely applied in the fields of nuclear reactor engineering, aerospace, solar energy and industrial waste heat utilization, due to the good heat transfer and flow characteristics. Therefore, numerous studies have been carried out experimentally and theoretically to investigate the heat and mass transfer performance by using liquid sodium in past decades, and most of them are concentrated on the experimental results, mechanisms and models of heat transfer and flow of liquid sodium. However, no comprehensive review article concerns on the thermal hydraulic characteristics of single-phase for liquid sodium. Thus, in this study, an analytical overview on thermal hydraulic characteristics of single-phase for liquid sodium is presented, using widely scattered available information from existing literature. It can be taken into account as a quick reference guide to have an overview of the thermal hydraulic characteristics of single-phase for liquid sodium in different channel geometries (circular tube, annular tube and rod bundles etc.) under different conditions.