反应堆安全壳密封结构的分形理论和泄漏机理研究

The containment integrity is significant for the nuclear safety. To keep its sealability during any working conditions, the leakage rate of these numerous containment penetrations has to be strictly controlled. However, few theoretical works have been done to give quantity guidance on the sealing construction design, mainly due to the extreme difficulty in describing the complex leakage mechanisms. Based on the experimental observation, it is found that microstructures of the leakage passages have the self-similar affine properties. Therefore, fractal theory for porous media is an appropriate method to represent their geometry characteristics. In this project, we innovatively introduce the transport theory of fractal porous media into the study of the leakage mechanism. The concrete research contents are as follows: 1. To find the fractal model for the micro-porous structures of leakage, and to build the leakage mechanism model based on the seepage mechanics; 2. To set up the mechanics model to analyze the change of the micro-porous structure with the stress, and to develop the predictive leakage model under the seal load; 3. To combine the dynamic characteristics of the rubber aging to study influences of heat and moisture on the leakage rate; 4. To investigate the leakage characteristics of the typical penetrations under various working conditions according to the above studies. Based on our research on the above contents, a set of theories and methods will be proposed to quantitatively predict the influence of various factors on the leakage, and to provide a good theoretical foundation of the optimum design and leakage rate control of the penetration seal constructions. Our research may also promote and enrich the theoretical development of the relevant disciplines.

安全壳的包容性对核安全有着重要意义。严格控制为数众多的安全壳贯穿件在任何条件下的泄漏量是确保其密封完整性的关键。密封结构的泄漏机理复杂、难以描述，是目前贯穿件密封设计缺乏定量依据的主要原因。实验观察表明，密封结构微观泄漏通道具有自仿射特性，可采用分形多孔介质表征。本项目引入分形多孔介质输运理论对贯穿件泄漏机理进行研究。具体研究内容：1、建立泄漏微孔结构的分形表征，探索基于渗流力学构建泄漏机理模型的方法；2、建立力学模型分析应力对泄漏微孔变形的影响，获取载荷条件下的泄漏预测模型；3、结合橡胶老化动力特性方程，研究热、湿等工况条件对泄漏的影响；4、在以上基础上，对典型贯穿件在各种工况下的泄漏特性进行研究。预计本项目的研究可以提出一套能够较为全面地描述各种因素对泄漏率定量影响的泄漏率预测理论和方法，为贯穿件密封结构的优化设计和泄漏控制提供理论依据，同时还可推动和丰富其它相关学科的理论发展。

安全壳的包容性对核安全有着重要意义。严格控制为数众多的安全壳贯穿件在任何条件下的泄漏量是确保其密封完整性的关键。密封结构的泄漏机理复杂、难以描述，是目前贯穿件密封设计缺乏定量依据的主要原因。实验观察表明，密封结构微观泄漏通道具有自仿射特性，可采用分形多孔介质表征。本项目引入分形多孔介质输运理论和方法，意在明确孔隙结构及其应力变形特性与气体输运特性之间的定量关系，从而构建高精度的泄漏机理模型。项目获得的重要成果包括：1、建立了精度较高且不依赖任何经验参数的界面泄漏和渗透泄漏的机理模型，可应用于金属垫片和非金属垫片密封结构的泄漏率计算和优化设计。2、构建了5种复杂贯穿件（耐压闸门、吊装孔、球阀、蝶阀、截止阀）的泄漏率预测模型。试验测量值显示预测结果具有很好的准确性，误差可控制在20%以内；3、对安全壳局部泄漏率分配指标的理论研究进行初步探索，为某舱室提供了合理的局部泄漏率分配比方案，并基于试验测量结果验证了方案准确性；4、完成了热、湿、载荷对泄漏率影响的定量分析，实现了密封结构泄漏特性研究从定性到定量的转换，可预测各种工况（包括LOCAL工况）下的泄漏率，对安全壳泄漏率检测试验设计有着重要理论指导意义。本项目已发表论文22篇，其中SCI论文10篇，参加国际会议5人次，共培养硕士研究生9名。项目研究为贯穿件密封结构的优化设计和泄漏控制提供理论依据，同时还推动和丰富相关学科的理论发展。