熔盐堆用冷冻阀的热-结构特性研究

Research on thermal and mechanical behaviour of a Freeze-Valve for molten salt reactor

反应堆安全是任何核能系统开发与设计的重要组成。冷冻阀是熔盐堆的核心技术之一,其热力学特性直接关系到熔盐堆核能系统的固有安全。本文旨在通过研究冷冻阀的热-结构特性并进行优化,探索可靠的安全设计,提高第四代核能系统的固有安全性,利用ANSYS软件建立了冷冻阀的三维有限元模型,对其关闭状态和开启过程进行了分析研究。结果表明:1)冷冻阀的扁平部位由于内部空间熔盐少,熔盐熔融和冻结容易控制,是实现开关功能和熔盐堆过热安全泄放的核心部位;2)获得了不同因素(如换热系数、加热功率、保温尺寸等)对冷冻阀在关闭状态与开启过程中的温度场及应力大小的影响规律,为冷冻阀的优化设计及安全运行管理提供了依据;3)由于初始模型中部分设计不合理(如保温尺寸和加热功率等),导致冷冻阀热应力过高,容易引起疲劳损伤,经分析优化和改进后,最大热应力明显减小,综合性能得到很大提高。

Background： Reactor safety is an important component of developing and designing any nuclear energy systems. The Freeze-Valve is one of the core technologies of the molten salt reactor, which thermal-structural property is directly related to the inherent safety of the molten salt reactor nuclear system. Purpose： The purpose of this paper is to improve the inherent safety of the fourth-generation nuclear energy systems, by researching and optimizing the thermodynamic properties of Freeze-Valve, and exploring reliable safety design. Methods： A 3D Finite Element model to simulate the thermal-structural coupling behaviors was established by the ANSYS software to analyze the performances and the properties of a Freeze-Valve. Results： The analysis result shows that the fiat part of the Freeze-Valve plays a very important role in engineering applications. The effects of different factors （heat transfer coefficient, heating power, and insulation size and so on） on the temperature and the stress field of the Freeze-Valve during operation are obtained, which provide some basis for optimization of design and safe operation. The thermal stress of the initial model of the Freeze-Valve is so large that it is easy to cause fatigue failure, owing to the unreasonable initial design （insulation size and heating power, for example）. Conclusions： After the relative analysis and structural optimization, the maximum stress of the Freeze-Valve is significantly reduced, and the performance has been greatly improved.