摘要
Based on the service characteristics of fuel elements for molten salt reactors,they need to have a high power density,resistance to coolant infiltration,and excellent thermodynamic properties.To solve the problem of the graphite used in the fuel element for these reactors being susceptible to molten salt infiltration,carbon black(CB)was added to increase the density of the graphite,and a fuel element(TRISO(tri-structural isotropic)fuel particles were randomly distributed in the modified graphite matrix)was prepared by cold isostatic pressing process.An out-of-pile performance study shows that the densification and pore structure of the modified graphite matrix were improved,as was the resistance to molten salt infiltration.The median pore size of the modified graphite was reduced from 673 to 433 nm and the threshold pressure for molten salt(FLiBe,66%(molar fraction)LiF and 34%BeF_(2))infiltration was increased from 0.88 to 1.37 MPa.The isotropic CB made the graphite matrix less anisotropic,while its thermal conductivity and compressive strength were reduced due to the difficult graphitization of CB.Fuel elements containing 20%(volume fraction)TRISO particles were prepared.Numerical simulations show that the power and temperature distribution of the fuel were in line with the design requirements.The modified graphite matrix had a higher density,smaller pores,a lower anisotropy and a greater resistance to FLiBe infiltration.
以熔盐堆燃料元件服役特点为依据,设计制备功率密度高、致密化抗冷却剂浸渗、热力学性能优异的燃料元件是熔盐堆固态燃料元件研究的焦点。为解决熔盐堆用燃料元件基体石墨易受熔盐浸渗的问题,本文通过添加炭黑对基体石墨进行致密化改性,采用冷等静压工艺制备出了一种燃料元件(TRISO燃料颗粒弥散分布于改性石墨基体中)。堆外性能研究显示,改性后石墨的致密化和孔结构均得到优化,抗熔盐浸渗能力提高。致密化改性后石墨的中值孔径由673 nm降低至433 nm;熔盐(FLiBe,66%(摩尔分数)的氟化锂与34%(摩尔分数)的氟化铍)浸渗阈值压强由0.88提升至1.37 MPa。各向同性的炭黑改善了石墨基体的各向异性,同时由于炭黑的难石墨化导致其热导率和抗压强度有所下降。用改性石墨制备包覆颗粒体积分数为20%的燃料元件,数值模拟表明,燃料的功率与温度分布符合设计要求。综上,改性后的石墨基体具有更高的致密性、更小的孔隙、更低的各向异性以及更强的抗熔盐渗透性能.
出处
《新型炭材料(中英文)》
北大核心
2025年第6期1362-1376,I0059,共16页
New Carbon Materials
基金
国家自然科学基金面上项目(52572058,12575191)
上海市自然科学基金面上项目(24ZR1478600)
中国科学院上海应用物理研究所钍基核裂变能全国重点实验室自部署项目(sys-zbs-202404).
