气冷快堆燃料组件设计及中子学特性分析

Design and neutronics characteristics analysis of the fuel assembly in gas-cooled fast reactor

气冷快堆兼具高温气冷堆的经济性和快堆的可持续性等优点,在四代堆型中具有独特的技术优势。为了适应气冷快堆高温、高中子通量的堆芯环境,本文基于耐事故燃料模型,提出了一种块状气冷快堆燃料组件设计方案,并对该组件中铀钚混合燃料中的钚含量、冷却孔道的直径及数量、栅距比、包壳及组件盒厚度等物理参数对中子学特性的影响规律开展了敏感性分析研究。分析结果表明:在研究的6个参数中,钚含量和栅距比对组件的中子学特性影响最大,冷却孔道数量主要影响组件内的功率分布,其余参数对组件中子学特性几乎无影响。最后针对块状燃料组件低冷却剂份额的特点,利用单通道模型进行组件内的温度分布计算,给出了热工限值对组件参数的要求。

[Background]The gas-cooled fast reactor(GFR)has great advantages of finance and sustainability which combines the features of high temperature gas-cooled reactor and fast reactor.However,safety issue has become the main challenge in the development of GFR due to the high temperature and high neutron flux in the GFR core.Coated particle fuel(CPF)has been widely used in high temperature reactor(HTR)due to the excellent high temperature tolerance.[Purpose]In order to strengthen the safety property in GFR,this paper puts forward a blocktype fuel assembly(FA)model based on CPF.Based on the FA model,neutronics analysis and thermal hydraulics validation is carried out to verify the rationality of the design.[Methods]Monte Carlo method is used in the calculation.Physical parameters including plutonium fraction in the U-Pu mixture fuel,diameter of fuel pins/coolant channels,the number of coolant channels,pitch-to-diameter ratio,thickness of cladding and thickness of assembly wrapper were selected and sensitivity analysis were conducted on the FA property to these parameters.[Results]Analysis results show that among the above six parameters,plutonium fraction and pitch-to-diameter ration have the most obvious effect on the neutronic property and the number of the coolant channels mainly influences the power distribution of the GFR FA.Finally,temperature distribution of the FA is calculated using single channel model under a low coolant fraction and requirements in terms of thermal-hydraulic property are put forward for the FA parameters.[Conclusions]The block-type FA model put forward in this paper meets the design requirements well.The research conclusion of this paper provides reference for the future study on GFR nuclear design.