The simulation study on natural circulation operating characteristics of FNPP in inclined condition

Ren Li,Genglei Xia,Minjun Peng,Lin Sun 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.7

Previous research has shown that the inclined condition has an impact on the natural circulation (natural circulation) mode operation of Floating Nuclear Power Plant (FNPP) mounted on the movable marine platform. Due to its compact structure, small volume, strong maneuverability, the Integral Pressurized Water Reactor (IPWR) is adopted as marine reactor in general. The OTSGs of IPWR are symmetrically arranged in the annular region between the reactor vessel and core support barrel in this paper. Therefore, many parallel natural circulation loops are built between the core and the OTSGs primary side when the main pump is stopped. and the inclined condition would lead to discrepancies of the natural circulation drive head among the OTSGs in different locations. In addition, the flow rate and temperature nonuniform distribution of the core caused by inclined condition are coupled with the thermal hydraulics parameters maldistribution caused by OTSG group operating mode on low power operation. By means of the RELAP5 codes were modified by adding module calculating the effect of inclined, heaving and rolling condition, the simulation model of IPWR in inclined condition was built. Using the models developed, the influences on natural circulation operation by inclined angle and OTSG position, the transitions between forced circulation (forced circulation) and natural circulation and the effect on natural circulation operation by different OTSG grouping situations in inclined condition were analyzed. It was observed that a larger inclined angle results the temperature of the core outlet is too high and the OTSG superheat steam is insufficient in natural circulation mode operation. In general, the inclined angle is smaller unless the hull is destroyed seriously or the platform overturn in the ocean. In consequence, the results indicated that the IPWR in the movable marine platform in natural circulation mode operation is safety. Selecting an appropriate average temperature setting value or operating the uplifted OTSG group individually is able to reduce the influence on natural circulation flow of IPWR by inclined condition.

Thermal-hydraulic and load following performance analysis of a heat pipe cooled reactor

Jiao Guanghui,Xia Genglei,Wang Jianjun,Peng Minjun 한국원자력학회 2024 Nuclear Engineering and Technology Vol.56 No.5

Heat pipe cooled reactors have gained attention as a potential solution for nuclear power generation in space and deep sea applications because of their simple design, scalability, safety and reliability. However, under complex operating conditions, a control strategy for variable load operation is necessary. This paper presents a twodimensional transient characteristics analysis program for a heat pipe cooled reactor and proposes a variable load control strategy using the recuperator bypass (CSURB). The program was verified against previous studies, and steady-state and step-load operating conditions were calculated. For normal operating condition, the predicted temperature distribution with constant heat pipe temperature boundary conditions agrees well with the literature, with a maximum temperature difference of 0.4 K. With the implementation of the control strategy using the recuperator bypass (CSURB) proposed in this paper, it becomes feasible to achieve variable load operation and return the system to a steady state solely through the self-regulation of the reactor, without the need to operate the control drum. The average temperature difference of the fuel does not exceed 1 % at the four power levels of 70 %,80 %, 90 % and 100 % Full power. The output power of the turbine can match the load change process, and the temperature difference between the inlet and outlet of the turbine increases as the power decreases.

Performance analysis of S-CO₂ recompression Brayton cycle based on turbomachinery detailed design

Zhang, Yuandong,Peng, Minjun,Xia, Genglei,Wang, Ge,Zhou, Cheng Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.9

The nuclear reactor coupled with supercritical carbon dioxide (S-CO₂) Brayton cycle has good prospects in generation IV reactors. Turbomachineries (turbine and compressor) are important work equipment in circulatory system, whose performances are critical to the efficiency of the energy conversion system. However, the sharp variations of S-CO₂ thermophysical properties make turbomachinery performances more complex than that of traditional working fluids. Meanwhile, almost no systematic analysis has considered the effects of turbomachinery efficiency under different conditions. In this paper, an in-house code was developed to realize the geometric design and performance prediction of S-CO₂ turbomachinery, and was coupled with systematic code for Brayton cycle characteristics analysis. The models and methodology adopted in calculation code were validated by experimental data. The effects of recompressed fraction, pressure and temperature on S-CO₂ recompression Brayton cycle were studied based on detailed design of turbomachinery. The results demonstrate that the recompressed fraction affects the turbomachinery characteristic by changing the mass flow and effects the system performance eventually. By contrast, the turbomachinery efficiency is insensitive to variation in pressure and temperature due to almost constant mass flow. In addition, the S-CO₂ thermophysical properties and the position of minimum temperature difference are significant influential factors of cyclic performance.

Numerical Study on Coolant Flow Distribution at the Core Inlet for an Integral Pressurized Water Reactor

Lin Sun,Minjun Peng,Genglei Xia,Xing Lv,Ren Li 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.1

When an integral pressurized water reactor is operated under low power conditions, oncethrough steam generator group operation strategy is applied. However, group operation strategy will cause nonuniform coolant flow distribution at the core inlet and lower plenum. To help coolant flow mix more uniformly, a flow mixing chamber (FMC) has been designed. In this paper, computational fluid dynamics methods have been used to investigate the coolant distribution by the effect of FMC. Velocity and temperature characteristics under different low power conditions and optimized FMC configuration have been analyzed. The results illustrate that the FMC can help improve the nonuniform coolant temperature distribution at the core inlet effectively; at the same time, the FMC will induce more resistance in the downcomer and lower plenum.

An intelligent hybrid methodology of on-line system-level fault diagnosis for nuclear power plant

Min-jun Peng,Hang Wang,Shan-shan Chen,Genglei Xia,Yong-kuo Liu,Xu Yang,Abiodun Ayodeji 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.3

To assist operators to properly assess the current situation of the plant, accurate fault diagnosis methodologyshould be available and used. A reliable fault diagnosis method is beneficial for the safety ofnuclear power plants. The major idea proposed in this work is integrating the merits of different faultdiagnosis methodologies to offset their obvious disadvantages and enhance the accuracy and credibilityof on-line fault diagnosis. This methodology uses the principle component analysis-based model andmulti-flow model to diagnose fault type. To ensure the accuracy of results from the multi-flow model, amechanical simulation model is implemented to do the quantitative calculation. More significantly,mechanism simulation is implemented to provide training data with fault signatures. Furthermore, oneof the distance formulas in similarity measurementdMahalanobis distancedis applied for on-line failuredegree evaluation. The performance of this methodology was evaluated by applying it to the reactorcoolant system of a pressurized water reactor. The results of simulation analysis show the effectivenessand accuracy of this methodology, leading to better confidence of it being integrated as a part of thecomputerized operator support system to assist operators in decision-making.