Steam generator tube rupture(SGTR) accident is an important scenario needed to be considered in the safety analysis of lead-based fast reactors. When the steam generator tube breaks close to the main pump, water vapor...Steam generator tube rupture(SGTR) accident is an important scenario needed to be considered in the safety analysis of lead-based fast reactors. When the steam generator tube breaks close to the main pump, water vapor will enter the reactor core, resulting in a two-phase flow of heavy liquid metal and water vapor in fuel assemblies. The thermal-hydraulic problems caused by the SGTR accident may seriously threaten reactor core's safety performance. In this paper, the open-source CFD calculation software OpenFOAM was used to encapsulate the improved Euler method into the self-developed solver LBEsteamEulerFoam. By changing different heating boundary conditions and inlet coolant types, the two-phase flow in the fuel assembly with different inlet gas content was simulated under various accident conditions. The calculation results show that the water vapor may accumulate in edge and corner channels. With the increase in inlet water vapor content, outlet coolant velocity increases gradually. When the inlet water vapor content is more than 15%, the outlet coolant temperature rises sharply with strong temperature fluctuation. When the inlet water vapor content is in the range of 5–20%, the upper part of the fuel assembly will gradually accumulate to form large bubbles. Compared with the VOF method, Euler method has higher computational efficiency. However, Euler method may cause an underestimation of the void fraction, so it still needs to be calibrated with future experimental data of the two-phase flow in fuel assembly.展开更多
Motivated to understand the pressure-buildup characteristics in a circumstance of a water droplet immerged inside a heavy liquid metal pool,which is a key phenomenon during a Steam Generator Tube Rupture accident of L...Motivated to understand the pressure-buildup characteristics in a circumstance of a water droplet immerged inside a heavy liquid metal pool,which is a key phenomenon during a Steam Generator Tube Rupture accident of Lead-cooled Fast Reactor,many experiments have been conducted by injecting water lumps into a molten lead pool at Sun Yat-sen University.In order to deepen the understanding of the influence of melt material,this lead experiment was compared with a Lead-Bismuth-Eutectic(LBE)experiment in the literature.For both experiments,a steam explosion occurred in a small part of the experi-mental runs,which generally leads to strengthened pressure buildup.Regarding the non-explosion experimental cases,the impact of all parameters employed in lead experiments(i.e.,water lump volume,water lump shape,molten pool depth,and temperature of water and melt)on the pressure buildup is non-negligible and similar to that in our previous experiments using LBE.Notably,limited pressure buildup with an increase in water lump volume was also observed.A slightly more violent pressure buildup tends to appear in the lead experiments than in the LBE experiments under the same experimental conditions,which may be due to the higher thermal conductivity of lead than of LBE.In a few experimental runs with a relatively low melt temperature close to the melting point of lead,local solidification of liquid lead was observed,restricting pressure buildup.For the lead and LBE experiments,the calculated melt kinetic energy conversion efficiencyηhas a relatively small value(not exceeding 1.6%),and theηvalues have an overall positive correlation with the impulse on the molten pool.展开更多
<span style="font-family:Verdana;">Accord</span><span style="font-family:Verdana;">ing</span><span style="font-family:Verdana;"> to </span><span sty...<span style="font-family:Verdana;">Accord</span><span style="font-family:Verdana;">ing</span><span style="font-family:Verdana;"> to </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">study of basic Rankin thermal cycle, the steam exh</span><span style="font-family:Verdana;">aust pressure of a typical steam turbine toward </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">condenser, plays a great rol</span><span style="font-family:Verdana;">e</span><span style="font-family:Verdana;"> in the efficiency and the net output power of </span><span style="font-family:Verdana;">the </span><span style="font-family:;" "=""><span style="font-family:Verdana;">steam turbine, so most surface conden</span><span style="font-family:Verdana;">sers </span></span><span style="font-family:Verdana;">that</span><span style="font-family:Verdana;"> are working in thermal power plants are kept at va</span><span style="font-family:;" "=""><span style="font-family:Verdana;">cuum condition so that the maximum power of thermal cycle can be achieved. The </span><span style="font-family:Verdana;">vacuu</span><span style="font-family:Verdana;">m pressure at condenser leads to </span></span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">entering of air </span><span style="font-family:Verdana;">and Non-</span><span style="font-family:Verdana;">condensable gases from turbine gland seals to condenser so that the special air ejection equipment is being used to take apart air from steam and vent it to out of condenser.</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">In this study</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> a special steam and air separator mechanism in </span><span style="font-family:Verdana;">an </span><span style="font-family:Verdana;">evacuating system called </span><span style="font-family:Verdana;">“</span><span style="font-family:Verdana;">Aircooler</span><span style="font-family:Verdana;">”</span><span style="font-family:Verdana;"> at a 16</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">MW steam turbine condenser is being studied and the Fluent CFD software is utilized to analyze the behavior of steam plus air in a typical aircooler system of 16</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">MW steam turbine condenser of Neka power plant to find a way to reduce the risk of cooling tube rupture in aircooler ducts. The critical condition which tube rupture happens is determined and it is demonstrated that in hot seasons of year, by increasing the seawater cooling temperature and increasing in turbine steam exhaust pressure and temperature, the risk of tube rupture due to more mixture velocity at the first row of aircooler cooling tubes increases and also</span><span style="font-family:Verdana;"> the effect of tube plugged condition on the performance of </span><span style="font-family:Verdana;">aircooler shows that the risk of other tubes rupture will increase and thus the efficiency of aircooler decreases due to more aircooler exhaust temperature. Finally</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> two modified plans at aircooler system design will be studied and simulated via Fluent CFD software which leads to reduce the risk of tube rupture. The results show that by modification of aircooler ducts and holes, the mixture air and steam flow velocity to first aircooler cooling tube row decreases significantly and causes the risk of tube rupture </span><span style="font-family:Verdana;">to </span><span style="font-family:Verdana;">decrease remarkably and also the exhaust temperature of aircooler decreases and causes the higher ejector performance.</span>展开更多
基金supported partly by the Ministry of Science and Technology of the People's Republic of China (No. 2020YFB1902100)the Shanghai Municipal Commission of Economy and Informatization (No. GYQJ-2018-2-02)。
文摘Steam generator tube rupture(SGTR) accident is an important scenario needed to be considered in the safety analysis of lead-based fast reactors. When the steam generator tube breaks close to the main pump, water vapor will enter the reactor core, resulting in a two-phase flow of heavy liquid metal and water vapor in fuel assemblies. The thermal-hydraulic problems caused by the SGTR accident may seriously threaten reactor core's safety performance. In this paper, the open-source CFD calculation software OpenFOAM was used to encapsulate the improved Euler method into the self-developed solver LBEsteamEulerFoam. By changing different heating boundary conditions and inlet coolant types, the two-phase flow in the fuel assembly with different inlet gas content was simulated under various accident conditions. The calculation results show that the water vapor may accumulate in edge and corner channels. With the increase in inlet water vapor content, outlet coolant velocity increases gradually. When the inlet water vapor content is more than 15%, the outlet coolant temperature rises sharply with strong temperature fluctuation. When the inlet water vapor content is in the range of 5–20%, the upper part of the fuel assembly will gradually accumulate to form large bubbles. Compared with the VOF method, Euler method has higher computational efficiency. However, Euler method may cause an underestimation of the void fraction, so it still needs to be calibrated with future experimental data of the two-phase flow in fuel assembly.
基金supported by the Basic and Applied Basic Research Foundation of Guangdong Province (Nos.2021A1515010343 and 2022A1515011582)the Science and Technology Program of Guangdong Province (Nos.2021A0505030026 and 2022A0505050029).
文摘Motivated to understand the pressure-buildup characteristics in a circumstance of a water droplet immerged inside a heavy liquid metal pool,which is a key phenomenon during a Steam Generator Tube Rupture accident of Lead-cooled Fast Reactor,many experiments have been conducted by injecting water lumps into a molten lead pool at Sun Yat-sen University.In order to deepen the understanding of the influence of melt material,this lead experiment was compared with a Lead-Bismuth-Eutectic(LBE)experiment in the literature.For both experiments,a steam explosion occurred in a small part of the experi-mental runs,which generally leads to strengthened pressure buildup.Regarding the non-explosion experimental cases,the impact of all parameters employed in lead experiments(i.e.,water lump volume,water lump shape,molten pool depth,and temperature of water and melt)on the pressure buildup is non-negligible and similar to that in our previous experiments using LBE.Notably,limited pressure buildup with an increase in water lump volume was also observed.A slightly more violent pressure buildup tends to appear in the lead experiments than in the LBE experiments under the same experimental conditions,which may be due to the higher thermal conductivity of lead than of LBE.In a few experimental runs with a relatively low melt temperature close to the melting point of lead,local solidification of liquid lead was observed,restricting pressure buildup.For the lead and LBE experiments,the calculated melt kinetic energy conversion efficiencyηhas a relatively small value(not exceeding 1.6%),and theηvalues have an overall positive correlation with the impulse on the molten pool.
文摘<span style="font-family:Verdana;">Accord</span><span style="font-family:Verdana;">ing</span><span style="font-family:Verdana;"> to </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">study of basic Rankin thermal cycle, the steam exh</span><span style="font-family:Verdana;">aust pressure of a typical steam turbine toward </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">condenser, plays a great rol</span><span style="font-family:Verdana;">e</span><span style="font-family:Verdana;"> in the efficiency and the net output power of </span><span style="font-family:Verdana;">the </span><span style="font-family:;" "=""><span style="font-family:Verdana;">steam turbine, so most surface conden</span><span style="font-family:Verdana;">sers </span></span><span style="font-family:Verdana;">that</span><span style="font-family:Verdana;"> are working in thermal power plants are kept at va</span><span style="font-family:;" "=""><span style="font-family:Verdana;">cuum condition so that the maximum power of thermal cycle can be achieved. The </span><span style="font-family:Verdana;">vacuu</span><span style="font-family:Verdana;">m pressure at condenser leads to </span></span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">entering of air </span><span style="font-family:Verdana;">and Non-</span><span style="font-family:Verdana;">condensable gases from turbine gland seals to condenser so that the special air ejection equipment is being used to take apart air from steam and vent it to out of condenser.</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">In this study</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> a special steam and air separator mechanism in </span><span style="font-family:Verdana;">an </span><span style="font-family:Verdana;">evacuating system called </span><span style="font-family:Verdana;">“</span><span style="font-family:Verdana;">Aircooler</span><span style="font-family:Verdana;">”</span><span style="font-family:Verdana;"> at a 16</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">MW steam turbine condenser is being studied and the Fluent CFD software is utilized to analyze the behavior of steam plus air in a typical aircooler system of 16</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">MW steam turbine condenser of Neka power plant to find a way to reduce the risk of cooling tube rupture in aircooler ducts. The critical condition which tube rupture happens is determined and it is demonstrated that in hot seasons of year, by increasing the seawater cooling temperature and increasing in turbine steam exhaust pressure and temperature, the risk of tube rupture due to more mixture velocity at the first row of aircooler cooling tubes increases and also</span><span style="font-family:Verdana;"> the effect of tube plugged condition on the performance of </span><span style="font-family:Verdana;">aircooler shows that the risk of other tubes rupture will increase and thus the efficiency of aircooler decreases due to more aircooler exhaust temperature. Finally</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> two modified plans at aircooler system design will be studied and simulated via Fluent CFD software which leads to reduce the risk of tube rupture. The results show that by modification of aircooler ducts and holes, the mixture air and steam flow velocity to first aircooler cooling tube row decreases significantly and causes the risk of tube rupture </span><span style="font-family:Verdana;">to </span><span style="font-family:Verdana;">decrease remarkably and also the exhaust temperature of aircooler decreases and causes the higher ejector performance.</span>
