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The helical-coil once-through steam generator (OTSG) is usually used in the nuclear power plant when the compactness of equipment was taken into consideration. The investigation of flow parameters in the primary side is valuable for the optimization of the OTSG. The purpose of this research is to obtain a further understanding of fluid behaviors in the primary side of the OTSG to achieve a more rational design. Using ANSYS ICEM and ANSYS FLUENT, a three-dimensional (3D) computational fluid dynamics (CFD) model was created and analyzed. Through a series of cases, the velocity profiles and pressure drop through the primary side of the helical-coil OTSG have been calculated, and the influences of different structure designs on the coolant flow parameters have also been tested. Ultimately some pertinent suggestions for improvements were proposed, and insight is obtained into the importance of various modeling considerations in such a model with a complicated structure and large-scale grids.

Helically coiled tube Once-Through Steam Generator (H-OTSG) is one of the key equipment types for small modular reactors. The flow instability of the secondary side of the H-OTSG is particularly serious, because the working condition is in the range of low and medium pressure. This paper presents research on density wave oscillations (DWO) in a typical countercurrent H-OTSG. Based on the steady-state calculation, the mathematical model of single-channel system was established, and the transfer function was derived. Using Nyquist stability criterion of the single variable, the stability cases were studied with an in-house computer program. According to the analyses, the impact law of the geometrical parameters to the system stability was obtained. RELAP5/MOD3.2 code was also used to simulate DWO in H-OTSG. The theoretical analyses of the in-house program were compared to the simulation results of RELAP5. A correction factor was introduced to reduce the error of RELAP5 when modeling helical geometry. The comparison results agreed well which showed that the correction is effective.

Now Nuclear Power Plants (NPPs) design is moving toward being highly dependent on digital computers in many complex systems, especially microprocessors. As a medium between operators and NPPs for exchange and interaction which ultimate operational decisions still rely on, the Human-System Interaction has been widely concerned and become one of the focuses in NPPs design. So in order to take full advantage of operating experience, human cognitive processing abilities, and progressive technologies, it is critical to plan, design, implement, operate, and maintain a reliable HSIs. The project, funded by the Nuclear Power Institute of China (NPIC), designs and develops a set of typical and comparatively complete technical solution of Human-System Interaction based on instrumentation and control system in actual NPP. To take advantage of the design process and modules as well as templates of this technical solution provided by this project, which take HFE into account, we can achieve the realistic simulation of Human-System Interaction for digital NPPs, making the use of iFIX software, and the Human-System Interaction system can be used to design interfaces for different kinds of NPPs. In this paper, the realization of human-system interaction will be introduced, and the current research status and main challenges of Human-System Interaction are included. And at this stage we have made the processes of the cross-platform data acquisition and monitoring, processing and display of small instrument control systems come true.