一体化快堆悬臂式换料机防组件跌落设计研究

Design and Research on Anti-assembly Drop of Integrated Fast Reactor Cantilever Transfer Mechanism

  • 摘要: 一体化快堆是世界核能系统的主流发展方向,具有最高的核燃料循环效率。一体化快堆首次采用直拉式换料系统,即悬臂式换料机、直拉式提升机和平移式转运机的组合方式。对换料机而言,组件跌落是危害性最大的一种事故。对该事故的发生原因进行分析得出,有2种情形会导致组件跌落:抓手套发生严重塑性变形或断裂以及操作流程错误。可通过提高抓手套的机械强度来提高可靠度;通过全自动控制换料并设置必要的连锁来避免操作流程错误。对于人因导致的操作流程错误无法彻底避免,通过合理地设计导向管运动行程可将组件跌落高度降至最低,从而减小跌落产生的危害性。因此,换料机发生组件跌落的概率极低,即使发生跌落,也不会影响反应堆的安全。

     

    Abstract: Nuclear energy is a high-tech strategic industry and a crucial support for fulfilling emission reduction commitments. The integrated fast reactor represents the world’s mainstream development direction and offers the highest nuclear fuel cycle efficiency. The reactor is the core component of the integrated fast reactor and the largest facility within the integrated closed fuel nuclear energy cycle system. In the integrated fast reactor, the reactor equipment adopts a compact and integrated design, further enhancing its economic efficiency. Unlike previous fast reactor refuelling systems, the straight-pull refuelling system was adopted in the Chinese integrated fast reactor for the first time, which combined the cantilever transfer mechanism, straight-pull elevator, and translation transporter. This design makes the reactor more compact and improves its economic efficiency. The cantilever transfer mechanism is a specialized device for in-pile transfer of fuel assemblies. It was fixed on the small rotary plug and can cover an area exceeding the diameter of the rotary plug. This design offers a significant advantage when the top arrangement space is limited and the size of the rotary plug is constrained. By using the cantilever transfer mechanism, the number of rotary plugs can be reduced from 3 to 2. Fuel assembly drop is one of the most harmful and serious accidents. Analysis of the gripper components reveals two scenarios that may cause the fuel assembly to fall: severe plastic deformation or fracture of the gripping glove (including strength failure and fatigue failure) and operational flow errors. Reliability can be improved by increasing the mechanical strength of the gripping gloves. Based on strength and fatigue calculations, the probability of gripping glove failure is very low. Process errors can be avoided by fully controlling the refuelling system and implementing necessary interlocks. Human intervention is minimized during fully automatic operation. While errors caused by human factors cannot be entirely eliminated, the drop height of the fuel assembly can be minimized by rationally designing the movement stroke of the guide tube, thereby reducing potential harm. According to drop test results of the CFR600 fuel assembly, free fall from this height does not cause damage to the fuel assembly. Therefore, the probability of fuel assembly drops in the transfer mechanism is extremely low, and even if a drop occurs, it will not affect the safety of the reactor.

     

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