池式钠冷快堆盒间流传热机理及其对余热排出能力影响研究

Heat transfer characteristics of the inter-wrapper flow have significant influence on the reactor core heat transfer and the capacity of the residual decay heat removal in the residual decay heat removal stage of pool type sodium-cooled fast reactors. The span of the geometric size of pool type sodium-cooled fast reactors is large, and the inter-wrapper flow belongs to narrow gap heat transfer because the inter-wrapper size is just several millimetres. And heat transfer characteristics of sodium and water exist in significantly difference due to the small Prandtl number of sodium. All these factors cause that heat transfer mechanism of the inter-wrapper flow is very special. At present, research on heat transfer mechanism of the inter-wrapper flow and enhancement of residual decay heat removal capacity of pool type sodium-cooled fast reactors is still in the exploration stage at home and abroad. In this project, numerical study on heat transfer mechanism of the inter-wrapper flow and characteristics of residual decay heat removal will be carried out under the condition of the residual decay heat removal of pool type sodium-cooled fast reactors. The multi-scale fine coupling numerical models will be built and numerical analysis code of pool type sodium-cooled fast reactors will be developed. Then heat transfer characteristics of the reactor core and the inter-wrapper flow will be investigated to reveal the flow path in the inter-wrapper and the coupling heat transfer mechanism. And the influence of the inter-wrapper flow on the safety heat transfer of the reactor core and the natural circulation capacity will be investigated to reveal the effect law of the inter-wrapper flow on residual decay heat removal capacity. This project can possess significant engineering reference value for research on safety characteristics and optimization design of residual decay heat removal system of pool type sodium-cooled fast reactors.

池式钠冷快堆事故余热排出阶段盒间流传热特性对堆芯安全传热及事故余热排出能力有重要影响。鉴于池式钠冷快堆大尺寸跨度的复杂结构，堆芯盒间尺寸仅为几个毫米，盒间流属窄缝传热，且钠的低Prandtl数使其与水的传热特性存在很大差异，使得盒间流传热机制非常特殊，目前国内外针对池式钠冷快堆盒间流传热机理及其对余热排出特性影响的研究仍处于探索阶段。本项目着力开展池式钠冷快堆事故余热排出工况下盒间流动与传热及余热排出特性的数值计算研究，建立池式钠冷快堆多尺度精细耦合数值模型，开发池式钠冷快堆数值分析程序，研究事故余热排出阶段池式钠冷快堆堆芯及盒间流动与传热特性，揭示盒间流动路径及耦合传热机理，分析盒间流对堆芯安全传热及自然循环能力的影响特性，并揭示盒间流对余热排出特性的影响规律。本项目对池式钠冷快堆事故安全特性研究及余热排出系统优化设计具有重要的工程参考价值。

池式钠冷快堆事故余热排出阶段盒间流传热特性对堆芯安全传热及事故余热排出能力有重要影响。目前国际上针对池式钠冷快堆盒间流传热机理及其对余热排出特性影响的研究仍处于探索阶段。本项目针对池式钠冷快堆盒间流传热机理及其对余热排出能力的影响进行了研究。首先开发了钠冷快堆盒内、盒间的子通道及三维精细模型并利用国际基准题对模型和方法进行了验证，实现了堆芯及盒间流动传热的精确模拟，揭示了堆芯盒间流传热机理及其对堆芯传热的影响特性；之后建立了钠冷快堆系统分析模型并实现了与子通道精细堆芯模型的耦合，并开发了一维系统分析程序与三维精细数值模型的耦合算法及分析程序，研发了具有自主知识产权的大型池式钠冷快堆耦合计算平台，实现了池式钠冷快堆系统及堆芯耦合传热特性的精确分析，获得了事故余热排出自然循环工况下池式钠冷快堆堆芯与热钠池之间的耦合流动换热特性；最后基于耦合计算平台开展了独立热交换器在钠池布置位置、布置方式及独立热交换器进出开口位置等敏感性分析，研究了事故余热排出自然循环工况下池式钠冷快堆堆芯与热钠池之间的耦合流动换热特性，揭示了余热排出工况下池式钠冷快堆盒间流传热机理及其对堆芯关键安全参数和余热排出特性的影响规律。本项目建立的堆芯及盒间子通道模型、三维精细数值模型、耦合分析模型及开发的耦合算法及计算平台等原创性成果可以为我国池式钠冷快堆事故安全特性研究及余热排出系统优化设计提供重要的理论支撑。