The Experts below are selected from a list of 6825 Experts worldwide ranked by ideXlab platform
Deokjung Lee - One of the best experts on this subject based on the ideXlab platform.
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multi physics steady state analysis of oecd nea modular high temperature Gas Cooled Reactor mhtgr 350
Journal of Nuclear Science and Technology, 2017Co-Authors: Matthieu Lemaire, Hyun Chul Lee, Namil Tak, Hyunsuk Lee, Deokjung LeeAbstract:This paper presents the application results of MCS/GAMMA+ to multi-physics analysis of OECD/NEA modular high temperature Gas-Cooled Reactor (MHTGR) benchmark Phase I Exercise 3. It is a part of int...
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multi physics steady state analysis of oecd nea modular high temperature Gas Cooled Reactor mhtgr 350
Journal of Nuclear Science and Technology, 2017Co-Authors: Matthieu Lemaire, Hyun Chul Lee, Namil Tak, Hyunsuk Lee, Deokjung LeeAbstract:ABSTRACTThis paper presents the application results of MCS/GAMMA+ to multi-physics analysis of OECD/NEA modular high temperature Gas-Cooled Reactor (MHTGR) benchmark Phase I Exercise 3. It is a part of international R&D efforts lead by the Next Generation Nuclear Plant (NGNP) US project to improve the neutron-physics and thermal-fluid simulation of (high temperature Gas-Cooled Reactors) HTGRs, one of the next generations of safer nuclear Reactors. Accurate and validated analysis tools are indeed a crucial requirement for safety analysis and licensing of nuclear Reactors. To guide this effort, a numerical benchmark on the MHTGR was created by the NGNP project and formally approved in 2012 for international participation by the OECD/NEA. The benchmark defines a common set of exercises and the comparison of solutions obtained with different analysis tools is expected to improve the understanding of simulation methods for HTGRs. The coupled neutronics/thermal-fluid solution presented in this paper was obtaine...
Zuoyi Zhang - One of the best experts on this subject based on the ideXlab platform.
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combining dual fluidized bed and high temperature Gas Cooled Reactor for co producing hydrogen and synthetic natural Gas by biomass Gasification
Energies, 2021Co-Authors: Yangping Zhou, Yujie Dong, Zuoyi ZhangAbstract:Biomass Gasification to produce burnable Gas now attracts an increasing interest for production flexibility in the renewable energy system. However, the biomass Gasification technology using dual fluidized bed which is most suitable for burnable Gas production still encounters problems of low production efficiency and high production cost. Here, we proposed a large-scale biomass Gasification system to combine dual fluidized bed and high-temperature Gas-Cooled Reactor (HTR) for co-production of hydrogen and synthetic natural Gas (SNG). The design of high-temperature Gas-Cooled Reactor biomass Gasification (HTR-BiGas) consists of one steam supply module to heat inlet steam of the Gasifier by HTR and ten biomass Gasification modules to co-produce 2000 MWth hydrogen and SNG by Gasifying the unpretreated biomass. Software for calculating the mass and energy balances of biomass Gasification was developed and validated by the experiment results on the Gothenburg biomass Gasification plant. The preliminary economic evaluation showed that HTR-BiGas and the other two designs, electric auxiliary heating and increasing recirculated product Gas, are economically comparative with present mainstream production techniques and the imported natural Gas in China. HTR-BiGas is the best, with production costs of hydrogen and SNG around 1.6 $/kg and 0.43 $/Nm3, respectively. These designs mainly benefit from proper production efficiencies with low fuel-related costs. Compared with HTR-BiGas, electric auxiliary heating is hurt by the higher electric charge and the shortcoming of increasing recirculated product Gas is its lower total production. Future works to improve the efficiency and economy of HTR-BiGas and to construct related facilities are introduced.
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dynamical modeling and simulation of the six modular high temperature Gas Cooled Reactor plant htr pm600
Energy, 2018Co-Authors: Zhe Dong, Zuoyi Zhang, Yujie Dong, Yifei Pan, Xiaojin HuangAbstract:Abstract The modular high temperature Gas-Cooled Reactor (MHTGR) is a typical small modular Reactor (SMR) with inherent nuclear safety, which has a low average power density about 3 MW/m3, uses TRISO particle based fuel elements, and adopts helium as coolant and graphite as both moderator and structure material. Based upon the multimodular scheme, i.e. multiple MHTGR-based nuclear steam supply system (NSSS) modules driving a single turbine/generator system, the MHTGR-based nuclear power plants (NPPs) with inherent safety as well as any desired power ratings can be realized. However, since multiple NSSS modules are coupled together by the common secondary-circuit, the operation and control of multimodular NPPs is quite different from those classical single modular NPPs. For the design and verification of operation and control strategies of a NPP, it is necessary to develop the dynamical model of this NPP, and to study its open-loop and closed-loop dynamics. In this paper, a lumped-parameter dynamical model of the six-modular MHTGR-based NPP HTR-PM600 is proposed based on the conservation laws of mass, energy and momentum, which is composed of the MHTGR-based NSSS modules and the common secondary-circuit. Then, both the open-loop responses to exterior disturbances and the closed-loop behavior in power-level maneuver are given by numerical simulation, which shows not only the feasibility of this model but also the coupling effect of the modules caused by the common secondary-circuit.
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air ingress analysis of chimney effect in the 200 mwe pebble bed modular high temperature Gas Cooled Reactor
Annals of Nuclear Energy, 2017Co-Authors: Zhipeng Chen, Lei Shi, Yanhua Zheng, Yujie Dong, Xiaoming Chen, Jun Sun, Fubing Chen, Zuoyi ZhangAbstract:Abstract In a high temperature Gas-Cooled Reactor (HTGR), one can postulate simultaneous ruptures of the pressure boundary at points near the top and bottom of the Reactor vessel. In this extremely low probability event, depressurization and heat-up of the core can lead to ingress of air into the vessel driven by the buoyancy of the hot helium relative to the colder, cavity air (‘chimney effect’). Although this is considered a ‘beyond design basis accidents’ (BDBA), it receives high attention because it may lead to graphite oxidation of reflectors and fuel elements so as to weaken the structural strength and lessen the ability of the coated particles to retain fission products. A study of the rate and severity of the air ingress and potential for oxidation in the 200 MWe Pebble-bed Modular High Temperature Gas-Cooled Reactor (HTR-PM) is described in this paper. The TINTE code was used to simulate the air ingress accident caused by the simultaneous rupture of the fuel charging tube and fuel discharging tube. A mitigation measure, the injection of nitrogen into the vessel, has also been proposed and evaluated with the TINTE model. The results indicate that, due to the high flow resistance of the pebble-bed core, the air ingress flow rate is limited. The oxygen content in the Reactor cavity is also limited due to the design of the Ventilated Low Pressure Containment (VLPC) that prevents the corrosion of the fuel elements and reflectors by limiting the amount of air that can enter the vessel. The results also indicate that the injection of the nitrogen in a suitable location and with a suitable mass flow rate can effectively prevent significant corrosion of the graphite.
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study on air ingress of the 200 mwe pebble bed modular high temperature Gas Cooled Reactor
Annals of Nuclear Energy, 2016Co-Authors: Peng Liu, Lei Shi, Yanhua Zheng, Zhipeng Chen, Yujie Dong, Jun Sun, Fubing Chen, Zuoyi ZhangAbstract:Abstract Air ingress, one of the beyond design basis accidents (BDBA) for high temperature Gas-Cooled Reactors (HTR), receives high attention during the design of the 200 MWe pebble-bed modular high temperature Gas-Cooled Reactor (HTR-PM), because it may result in severe consequence including the corrosion of the fuel elements and graphite reflector. A hypothetical air ingress accident, caused by the double-ended guillotine break (DEGB) of the horizontal coaxial hot-Gas duct, is studied in this paper. After the rupture of the hot-Gas duct, the following accident developing progress can be divided into three stages: (1) depressurization, (2) slow air ingress via diffusion and local convection, (3) onset of the overall, stable natural circulation and the consequent continuous air ingress. Based on the design of the HTR-PM, the time scale of diffusion and convection in the second stage is studied to evaluate the onset time of the stable natural circulation. Furthermore, the TINTE model of the HTR-PM is then established to simulate the hot-Gas duct DEGB accident, including the flow rate of natural circulation, the corrosion of the fuel elements and the graphite reflector, the feasibility of the mitigation measures. The results show that due to the high pebble bed core with large flow resistance, as well as the complicated flow structure of the HTR-PM, it would take long time to obtain stable natural circulation. The results also indicate that, the bottom reflector graphite could consume most of the oxygen before it reaches the core and the injection of the nitrogen can effectively mitigate the corrosion of the graphite.
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the shandong shidao bay 200 mw e high temperature Gas Cooled Reactor pebble bed module htr pm demonstration power plant an engineering and technological innovation
Engineering, 2016Co-Authors: Zuoyi Zhang, Hong Wang, Xiaojin Huang, Yujie Dong, Fu Li, Zhengming Zhang, Haitao Wang, Hong Li, Xinxin Wu, Xingzhong DiaoAbstract:ABSTRACT After the first concrete was poured on December 9, 2012 at the Shidao Bay site in Rongcheng, Shandong Province, China, the construction of the Reactor building for the world's first high-temperature Gas-Cooled Reactor pebble-bed module (HTR-PM) demonstration power plant was completed in June, 2015. Installation of the main equipment then began, and the power plant is currently progressing well toward connecting to the grid at the end of 2017. The thermal power of a single HTR-PM Reactor module is 250 MWth, the helium temperatures at the Reactor core inlet/outlet are 250/750 °C, and a steam of 13.25 MPa/567 °C is produced at the steam generator outlet. Two HTR-PM Reactor modules are connected to a steam turbine to form a 210 MWe nuclear power plant. Due to China's industrial capability, we were able to overcome great difficulties, manufacture first-of-a-kind equipment, and realize series major technological innovations. We have achieved successful results in many aspects, including planning and implementing RD these obtained experiences may also be referenced by the global nuclear community.
Matthieu Lemaire - One of the best experts on this subject based on the ideXlab platform.
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multi physics steady state analysis of oecd nea modular high temperature Gas Cooled Reactor mhtgr 350
Journal of Nuclear Science and Technology, 2017Co-Authors: Matthieu Lemaire, Hyun Chul Lee, Namil Tak, Hyunsuk Lee, Deokjung LeeAbstract:This paper presents the application results of MCS/GAMMA+ to multi-physics analysis of OECD/NEA modular high temperature Gas-Cooled Reactor (MHTGR) benchmark Phase I Exercise 3. It is a part of int...
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multi physics steady state analysis of oecd nea modular high temperature Gas Cooled Reactor mhtgr 350
Journal of Nuclear Science and Technology, 2017Co-Authors: Matthieu Lemaire, Hyun Chul Lee, Namil Tak, Hyunsuk Lee, Deokjung LeeAbstract:ABSTRACTThis paper presents the application results of MCS/GAMMA+ to multi-physics analysis of OECD/NEA modular high temperature Gas-Cooled Reactor (MHTGR) benchmark Phase I Exercise 3. It is a part of international R&D efforts lead by the Next Generation Nuclear Plant (NGNP) US project to improve the neutron-physics and thermal-fluid simulation of (high temperature Gas-Cooled Reactors) HTGRs, one of the next generations of safer nuclear Reactors. Accurate and validated analysis tools are indeed a crucial requirement for safety analysis and licensing of nuclear Reactors. To guide this effort, a numerical benchmark on the MHTGR was created by the NGNP project and formally approved in 2012 for international participation by the OECD/NEA. The benchmark defines a common set of exercises and the comparison of solutions obtained with different analysis tools is expected to improve the understanding of simulation methods for HTGRs. The coupled neutronics/thermal-fluid solution presented in this paper was obtaine...
Yanhua Zheng - One of the best experts on this subject based on the ideXlab platform.
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study on the dlofc and plofc accidents of the 200 mwe pebble bed modular high temperature Gas Cooled Reactor with tinte and spectra codes
Annals of Nuclear Energy, 2018Co-Authors: Yanhua Zheng, Marek M Stempniewicz, Zhipeng Chen, Lei ShiAbstract:Abstract Validation and verification (V&V) is important and receives significant attention during the design and analysis of the nuclear power plant. As the first commercial modular high temperature Gas-Cooled Reactor (HTR) demonstration plant, during the regulatory review of the preliminary safety analysis report (PSAR) and the final safety analysis report (FSAR) of the 200 MWe Pebble-bed Modular High Temperature Gas-Cooled Reactor (HTR-PM), the authorities also pay high attention to the code validation and verification. Within the cooperation between the Nuclear Research Group (NRG) of Netherland and Institute of Nuclear and new Energy Technology (INET), Tsinghua University of China, a code to code verification was carried out between the TINTE code, a thermal-hydraulic design and accident analysis tool for the Pebble-bed High Temperature Gas-Cooled Reactor (HTGR), and the SPECTRA code, a thermal-hydraulic analysis code developed at the NRG. Three typical accident s scenarios, two depressurized loss of forced cooling (DLOFC) accident s scenarios and one pressurized loss of forced cooling (PLOFC) accident scenario, have been analyzed both with the TINTE code and the SPECTRA code. The simulation results show good agreement between TINTE code and SPECTRA code. The results also indicate that, due to the inherent safety feature of the HTR-PM design, the maximal fuel temperature during above accidents would never exceed the limitation of 1620 °C, below which there is no additional damage for the TRISO particles, and the SiC layer of each particle can guarantee the fission-product-retention capacity. This work will be helpful to the further study of the HTGR, and more code to code verification is planned.
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numerical simulation on heat transfer process in the Reactor cavity of modular high temperature Gas Cooled Reactor
Applied Thermal Engineering, 2017Co-Authors: Hangbin Zhao, Yanhua Zheng, Yujie Dong, Xiaoming ChenAbstract:Abstract In order to enhance the safety of the Reactor, the passive residual heat removal system (PRHRS) is adopted by both the 10 MW High Temperature Gas-Cooled Test Reactor (HTR-10) and the High Temperature Gas-Cooled Reactor Pebble-bed Module (HTR-PM). The heat transfer process in the Reactor cavity is very important for the whole PRHRS to remove the heat from the Reactor, especially once an accident occurs. A three-dimensional numerical model used to simulate the heat transfer process in the Reactor cavity of HTR-10 was developed in this study, in which the flow of water in the water Cooled pipe was included. The effects of different symmetry boundary conditions on the heat transfer process were studied. Three experimental conditions of HTR-10 were simulated, and the local and global heat transfer processes were analyzed. The results show that the effects of symmetry boundary condition can be neglected when two or more water Cooled pipes are included in the model. The temperature of air varies greatly near the Reactor pressure vessel (RPV) and the water Cooled panel. The maximum temperature occurs at the top of the RPV. With the elevation increasing, the rising rate of water temperature gradually increases. Moreover, radiation become more dominant as the RPV temperature rises.
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air ingress analysis of chimney effect in the 200 mwe pebble bed modular high temperature Gas Cooled Reactor
Annals of Nuclear Energy, 2017Co-Authors: Zhipeng Chen, Lei Shi, Yanhua Zheng, Yujie Dong, Xiaoming Chen, Jun Sun, Fubing Chen, Zuoyi ZhangAbstract:Abstract In a high temperature Gas-Cooled Reactor (HTGR), one can postulate simultaneous ruptures of the pressure boundary at points near the top and bottom of the Reactor vessel. In this extremely low probability event, depressurization and heat-up of the core can lead to ingress of air into the vessel driven by the buoyancy of the hot helium relative to the colder, cavity air (‘chimney effect’). Although this is considered a ‘beyond design basis accidents’ (BDBA), it receives high attention because it may lead to graphite oxidation of reflectors and fuel elements so as to weaken the structural strength and lessen the ability of the coated particles to retain fission products. A study of the rate and severity of the air ingress and potential for oxidation in the 200 MWe Pebble-bed Modular High Temperature Gas-Cooled Reactor (HTR-PM) is described in this paper. The TINTE code was used to simulate the air ingress accident caused by the simultaneous rupture of the fuel charging tube and fuel discharging tube. A mitigation measure, the injection of nitrogen into the vessel, has also been proposed and evaluated with the TINTE model. The results indicate that, due to the high flow resistance of the pebble-bed core, the air ingress flow rate is limited. The oxygen content in the Reactor cavity is also limited due to the design of the Ventilated Low Pressure Containment (VLPC) that prevents the corrosion of the fuel elements and reflectors by limiting the amount of air that can enter the vessel. The results also indicate that the injection of the nitrogen in a suitable location and with a suitable mass flow rate can effectively prevent significant corrosion of the graphite.
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study on air ingress of the 200 mwe pebble bed modular high temperature Gas Cooled Reactor
Annals of Nuclear Energy, 2016Co-Authors: Peng Liu, Lei Shi, Yanhua Zheng, Zhipeng Chen, Yujie Dong, Jun Sun, Fubing Chen, Zuoyi ZhangAbstract:Abstract Air ingress, one of the beyond design basis accidents (BDBA) for high temperature Gas-Cooled Reactors (HTR), receives high attention during the design of the 200 MWe pebble-bed modular high temperature Gas-Cooled Reactor (HTR-PM), because it may result in severe consequence including the corrosion of the fuel elements and graphite reflector. A hypothetical air ingress accident, caused by the double-ended guillotine break (DEGB) of the horizontal coaxial hot-Gas duct, is studied in this paper. After the rupture of the hot-Gas duct, the following accident developing progress can be divided into three stages: (1) depressurization, (2) slow air ingress via diffusion and local convection, (3) onset of the overall, stable natural circulation and the consequent continuous air ingress. Based on the design of the HTR-PM, the time scale of diffusion and convection in the second stage is studied to evaluate the onset time of the stable natural circulation. Furthermore, the TINTE model of the HTR-PM is then established to simulate the hot-Gas duct DEGB accident, including the flow rate of natural circulation, the corrosion of the fuel elements and the graphite reflector, the feasibility of the mitigation measures. The results show that due to the high pebble bed core with large flow resistance, as well as the complicated flow structure of the HTR-PM, it would take long time to obtain stable natural circulation. The results also indicate that, the bottom reflector graphite could consume most of the oxygen before it reaches the core and the injection of the nitrogen can effectively mitigate the corrosion of the graphite.
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analysis on blow down transient in water ingress accident of high temperature Gas Cooled Reactor
Nuclear Engineering and Design, 2014Co-Authors: Yan Wang, Yanhua Zheng, Lei ShiAbstract:Abstract Water ingress into the primary circuit is generally recognized as one of the severe accidents with potential hazard to the modular high temperature Gas-Cooled Reactor, which will cause a positive reactivity introduction with the increase of steam density in Reactor core to enhance neutron slowing-down, also the chemical corrosion of graphite fuel elements and the damage of reflector structure material. The increase of the primary pressure may result in the opening of the safety valves, consequently leading the release of radioactive isotopes and flammable water Gas. The research on water ingress transient is significant for the verification of inherent safety characteristics of high temperature Gas-Cooled Reactor. The 200 MWe high temperature Gas-Cooled Reactor (HTR-PM), designed by the Institute of Nuclear and New Energy Technology of Tsinghua University, is exampled to be analyzed in this paper. The design basis accident (DBA) scenarios of double-ended guillotine break of single heat-exchange tube (steam generator heat-exchange tube rupture) are simulated by the thermal-hydraulic analysis code, and some key concerns which are relative to the amount of water into the Reactor core during the blow-down transient are analyzed in detail. The results show that both of water mass and steam ratio of the fluid spouting from the broken heat-exchange tube are affected by break location, which will increase obviously with the broken location closing to the outlet of the heat-exchange tube. The double-ended guillotine rupture at the outlet of the heat-exchange will result more steam penetrates into the Reactor core in the design basis accident of water ingress. The mass of water ingress will also be affected by the draining system. It is concluded that, with reasonable optimization on design to balance safety and economy, the total mass of water ingress into the primary circuit of Reactor could be limited effectively to meet the safety requirements, and the pollution of radioactive isotopes releasing to the secondary circuit during the blow-down transient will be prevented.
Yujie Dong - One of the best experts on this subject based on the ideXlab platform.
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combining dual fluidized bed and high temperature Gas Cooled Reactor for co producing hydrogen and synthetic natural Gas by biomass Gasification
Energies, 2021Co-Authors: Yangping Zhou, Yujie Dong, Zuoyi ZhangAbstract:Biomass Gasification to produce burnable Gas now attracts an increasing interest for production flexibility in the renewable energy system. However, the biomass Gasification technology using dual fluidized bed which is most suitable for burnable Gas production still encounters problems of low production efficiency and high production cost. Here, we proposed a large-scale biomass Gasification system to combine dual fluidized bed and high-temperature Gas-Cooled Reactor (HTR) for co-production of hydrogen and synthetic natural Gas (SNG). The design of high-temperature Gas-Cooled Reactor biomass Gasification (HTR-BiGas) consists of one steam supply module to heat inlet steam of the Gasifier by HTR and ten biomass Gasification modules to co-produce 2000 MWth hydrogen and SNG by Gasifying the unpretreated biomass. Software for calculating the mass and energy balances of biomass Gasification was developed and validated by the experiment results on the Gothenburg biomass Gasification plant. The preliminary economic evaluation showed that HTR-BiGas and the other two designs, electric auxiliary heating and increasing recirculated product Gas, are economically comparative with present mainstream production techniques and the imported natural Gas in China. HTR-BiGas is the best, with production costs of hydrogen and SNG around 1.6 $/kg and 0.43 $/Nm3, respectively. These designs mainly benefit from proper production efficiencies with low fuel-related costs. Compared with HTR-BiGas, electric auxiliary heating is hurt by the higher electric charge and the shortcoming of increasing recirculated product Gas is its lower total production. Future works to improve the efficiency and economy of HTR-BiGas and to construct related facilities are introduced.
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dynamical modeling and simulation of the six modular high temperature Gas Cooled Reactor plant htr pm600
Energy, 2018Co-Authors: Zhe Dong, Zuoyi Zhang, Yujie Dong, Yifei Pan, Xiaojin HuangAbstract:Abstract The modular high temperature Gas-Cooled Reactor (MHTGR) is a typical small modular Reactor (SMR) with inherent nuclear safety, which has a low average power density about 3 MW/m3, uses TRISO particle based fuel elements, and adopts helium as coolant and graphite as both moderator and structure material. Based upon the multimodular scheme, i.e. multiple MHTGR-based nuclear steam supply system (NSSS) modules driving a single turbine/generator system, the MHTGR-based nuclear power plants (NPPs) with inherent safety as well as any desired power ratings can be realized. However, since multiple NSSS modules are coupled together by the common secondary-circuit, the operation and control of multimodular NPPs is quite different from those classical single modular NPPs. For the design and verification of operation and control strategies of a NPP, it is necessary to develop the dynamical model of this NPP, and to study its open-loop and closed-loop dynamics. In this paper, a lumped-parameter dynamical model of the six-modular MHTGR-based NPP HTR-PM600 is proposed based on the conservation laws of mass, energy and momentum, which is composed of the MHTGR-based NSSS modules and the common secondary-circuit. Then, both the open-loop responses to exterior disturbances and the closed-loop behavior in power-level maneuver are given by numerical simulation, which shows not only the feasibility of this model but also the coupling effect of the modules caused by the common secondary-circuit.
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numerical simulation on heat transfer process in the Reactor cavity of modular high temperature Gas Cooled Reactor
Applied Thermal Engineering, 2017Co-Authors: Hangbin Zhao, Yanhua Zheng, Yujie Dong, Xiaoming ChenAbstract:Abstract In order to enhance the safety of the Reactor, the passive residual heat removal system (PRHRS) is adopted by both the 10 MW High Temperature Gas-Cooled Test Reactor (HTR-10) and the High Temperature Gas-Cooled Reactor Pebble-bed Module (HTR-PM). The heat transfer process in the Reactor cavity is very important for the whole PRHRS to remove the heat from the Reactor, especially once an accident occurs. A three-dimensional numerical model used to simulate the heat transfer process in the Reactor cavity of HTR-10 was developed in this study, in which the flow of water in the water Cooled pipe was included. The effects of different symmetry boundary conditions on the heat transfer process were studied. Three experimental conditions of HTR-10 were simulated, and the local and global heat transfer processes were analyzed. The results show that the effects of symmetry boundary condition can be neglected when two or more water Cooled pipes are included in the model. The temperature of air varies greatly near the Reactor pressure vessel (RPV) and the water Cooled panel. The maximum temperature occurs at the top of the RPV. With the elevation increasing, the rising rate of water temperature gradually increases. Moreover, radiation become more dominant as the RPV temperature rises.
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air ingress analysis of chimney effect in the 200 mwe pebble bed modular high temperature Gas Cooled Reactor
Annals of Nuclear Energy, 2017Co-Authors: Zhipeng Chen, Lei Shi, Yanhua Zheng, Yujie Dong, Xiaoming Chen, Jun Sun, Fubing Chen, Zuoyi ZhangAbstract:Abstract In a high temperature Gas-Cooled Reactor (HTGR), one can postulate simultaneous ruptures of the pressure boundary at points near the top and bottom of the Reactor vessel. In this extremely low probability event, depressurization and heat-up of the core can lead to ingress of air into the vessel driven by the buoyancy of the hot helium relative to the colder, cavity air (‘chimney effect’). Although this is considered a ‘beyond design basis accidents’ (BDBA), it receives high attention because it may lead to graphite oxidation of reflectors and fuel elements so as to weaken the structural strength and lessen the ability of the coated particles to retain fission products. A study of the rate and severity of the air ingress and potential for oxidation in the 200 MWe Pebble-bed Modular High Temperature Gas-Cooled Reactor (HTR-PM) is described in this paper. The TINTE code was used to simulate the air ingress accident caused by the simultaneous rupture of the fuel charging tube and fuel discharging tube. A mitigation measure, the injection of nitrogen into the vessel, has also been proposed and evaluated with the TINTE model. The results indicate that, due to the high flow resistance of the pebble-bed core, the air ingress flow rate is limited. The oxygen content in the Reactor cavity is also limited due to the design of the Ventilated Low Pressure Containment (VLPC) that prevents the corrosion of the fuel elements and reflectors by limiting the amount of air that can enter the vessel. The results also indicate that the injection of the nitrogen in a suitable location and with a suitable mass flow rate can effectively prevent significant corrosion of the graphite.
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study on air ingress of the 200 mwe pebble bed modular high temperature Gas Cooled Reactor
Annals of Nuclear Energy, 2016Co-Authors: Peng Liu, Lei Shi, Yanhua Zheng, Zhipeng Chen, Yujie Dong, Jun Sun, Fubing Chen, Zuoyi ZhangAbstract:Abstract Air ingress, one of the beyond design basis accidents (BDBA) for high temperature Gas-Cooled Reactors (HTR), receives high attention during the design of the 200 MWe pebble-bed modular high temperature Gas-Cooled Reactor (HTR-PM), because it may result in severe consequence including the corrosion of the fuel elements and graphite reflector. A hypothetical air ingress accident, caused by the double-ended guillotine break (DEGB) of the horizontal coaxial hot-Gas duct, is studied in this paper. After the rupture of the hot-Gas duct, the following accident developing progress can be divided into three stages: (1) depressurization, (2) slow air ingress via diffusion and local convection, (3) onset of the overall, stable natural circulation and the consequent continuous air ingress. Based on the design of the HTR-PM, the time scale of diffusion and convection in the second stage is studied to evaluate the onset time of the stable natural circulation. Furthermore, the TINTE model of the HTR-PM is then established to simulate the hot-Gas duct DEGB accident, including the flow rate of natural circulation, the corrosion of the fuel elements and the graphite reflector, the feasibility of the mitigation measures. The results show that due to the high pebble bed core with large flow resistance, as well as the complicated flow structure of the HTR-PM, it would take long time to obtain stable natural circulation. The results also indicate that, the bottom reflector graphite could consume most of the oxygen before it reaches the core and the injection of the nitrogen can effectively mitigate the corrosion of the graphite.
