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 t...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.展开更多
文摘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.
