核动力工程

Experimental and CFD Simulation of the RPV Head Plenum

Chen Yongchao, Wei Xingfang, Liu Yanwu, Fang Jian, Ran Xiaobing

, Available online , doi: 10.13832/j.jnpe.2024.070004

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Abstract:
This paper aims to investigate the flow characteristics of the RPV Head Plenum region in the HPR1000 Pressurized Water Reactor (PWR) to provide support for addressing the erosion of the Thermal Sleeve in operational CPR1000 PWR plants and optimizing the RPV Head Plenum region structures in HPR1000 PWR plants. This paper uses Computational Fluid Dynamics (CFD) methods to conduct numerical simulations of the RPV Head Plenum region and also carries out hydraulic model experiments of the RPV Head Plenum to obtain the flow distribution and hydraulic characteristics of key areas within the RPV Head Plenum region. The theoretical analysis and experimental results show that: The CFD results of the key areas in the RPV Head Plenum and the measured lateral velocity deviations from the experiments are within 10%. Under normal operating conditions, the overall flow velocity within the RPV Head Plenum is relatively low, but higher velocities are observed near the RPV Head nozzles and nearby surface. The coolant water in RPV Head Plenum flows downward through the holes at the top of CRGT and then flows into the Upper Plenum, which is consistent with the expectation of the HPR1000 “Cold RPV head”. Additionally, a vortex with higher flow velocity is present near the Thermal Sleeve Bell Mouth in the central region than in the peripheral area of the RPV Head Plenum, resulting in more severe fluid impact and wear on the thermal sleeves.

Large-eddy Simulation of Temperature Fluctuation Characteristics of Lead Bismuth Eutectic Alloy in Triple Jet

Guo Chao, Xu Jiangming, Liu Songtao, Miao Yiran

, Available online , doi: 10.13832/j.jnpe.2024.060038

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Abstract:
In order to study influence of velocity on LBE temperature fluctuations, temperature fluctuation characteristics of lead bismuth eutectic alloy in triple jet was simulated. Firstly, three turbulent models were used to analyze temperature fluctuations characteristics of sodium in triple jet. The temperature and velocity fields at different times were evaluated and temperature fluctuation characteristics were predicted successfully by large eddy simulation (LES) and LES is suitable for analyzing temperature fluctuations characteristics of liquid metal. Secondly, LES was employed to simulate temperature fluctuation characteristics of lead bismuth eutectic alloy(LBE) in triple jet at different velocities and velocity ratios. Finally, by analyzing the influence of different velocity ratios and different velocities, it is found that the amplitude and frequency of temperature fluctuation increases as the velocity increases due to that increase of velocity enhanced turbulence. The temperature fluctuation characteristics of LBE alloy in triple jet were analyzed and it could be anticipated to support the subsequent investigation of temperature fluctuations of LBE cooled fast reactor.

Analysis of Heat Transfer Characteristics of Steam Generator with Axial Economizer Based on RELAP5

Huang Zhongyuan, Wang Xiaoding, Li Zhenzhong, Liu Haidong, Chen Deqi

, Available online , doi: 10.13832/j.jnpe.2024.050032

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Abstract:
The vertical natural-circulation steam generator, as a crucial equipment in pressurized water reactor nuclear power plants, enhancing its heat transfer performance is vital to the economy of the entire power plant. This study selects the steam generator of AP1000 as the research object and employs the RELAP5 system analysis program to calculate and analyze both the conventional steam generator and the steam generator with axial economizer. The heat transfer mechanism of the steam generator with axial economizer is studied, and focus on the effects of different heights of the divider plate and the recirculated water distribution ratio on the heat transfer characteristics. The results show that the steam generator with axial economizer can significantly increase the heat transfer temperature difference between the primary and secondary sides, thereby effectively enhancing the overall heat transfer efficiency. In addition, the study finds that increasing the height of the divider plate can improve the heat transfer capacity to a certain extent, and there is an optimal height at which the heat transfer power reaches its peak. Moreover, reducing the recirculated water distribution ratio helps to increase the heat transfer temperature difference, further improving the heat transfer performance. This research provides reference for the engineering analysis and design of the steam generator with axial economizer.

Numerical Simulation Research on Natural Circulation Flow of the Reactor Coolant System

Zhang Mingqian, Lin Run, Li Zhenguang

, Available online , doi: 10.13832/j.jnpe.2024.050038

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Abstract:
Computational Fluid Dynamics(CFD) program is employed to enable the high-fidelity modeling of the reactor coolant system (RCS) for a typical three-loop pressurized water reactor, and the completed model of the RCS is build including reactor vessel and internals, core, steam generator, primary pump and linking pipe. The three-dimensional, global and localized flow features have been investigated under natural circulation flow condition with lower core thermal power, and the temperature at different locations are compared with the measured values from the operating nuclear power plant in order to verify the accurate description of the developed CFD model. The results show that the natural circulation flow rate is about 4.5% of the full power flow rate while the temperature of the core outlet is stable, and the residual core heat could be effectively removed. The phenomenon of the thermal stratification in the reactor pressure vessel head dome shows that the measured temperature value of the detector position in nuclear power plant could not provide the highest value. The coolant from different loops could be more fully mixed due to the local convection flow. There is a swirling flow at the outlet of primary pump, and the tangential velocity near the pipe wall is large while the local convection occurs at the central area. This analysis practice provides an effective evaluation for the system-level three-dimensional thermal hydraulics phenomena of the reactor coolant system.

Experimental Study of Geyser Boiling in High-temperature Sodium Heat Pipe at Inclined Angle Condition

Yang Siyuan, Ma Yugao, Wen Qinglong, Wen Shuang, Ding Shuhua, He Linfeng, Yuan Bo

, Available online , doi: 10.13832/j.jnpe.2024.060020

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Abstract:
To study the geyser boiling phenomenon in the start-up process of high-temperature alkali metal heat pipe and provide reference operating conditions for the safe operation of the heat pipe reactor, sodium metal was used as the working medium to investigate the influence factors and mechanism of geyser boiling during the start-up process of the heat pipe. The results show that the heating power and inclination angle of the heat pipe have important effects on geyser boiling. Under the condition of 90° inclination angle, the heating power increases from 600 W to 750 W, the geyser boiling period varies from 736 s to 29 s, and the temperature amplitude ranges from 35℃ to 18℃. Geyser boiling is easy to occur under medium heating power conditions but will not happen when the inclination of the heat pipe is 0°. With the increase of inclination angle, the heating power of the start and stop of the geyser boiling decreases. When the inclination angle is 45°, 60°, 90° respectively, the geyser boiling starts at 250, 200, 150 W and stops at 600, 450, 350 W. The geyser boiling period varies at the same heating power from different inclination angles, but the temperature amplitude changes little. The geyser boiling intensity decreases and the power range of geyser boiling advances with the shortening of the condensing section. The results of this study laid a foundation for further research on the geyser boiling mechanism of alkali metal heat pipes, and provide important data and theoretical support for the design optimization of alkali metal heat pipes and the safe operation of heat pipe reactors.

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