Phase Diagram And Thermodynamic Researches Of The Fe-Zr Based Nuclear Materials

With the increasing energy crisis around the world,the application of nuclear power as a clean energy source is an inevitable trend.Therefore,the safety analysis during the application is particularly important.In case of a reactor severe accident,to maintain the integrity of the reactor vessel is the foundation for nuclear safety.However,the validity of the In-Vessel corium Retention measurement depends on the researches on the stratification structure and thermodynamic behaviour of the corium pool.Establishment of a thermodynamic database of the reactor corium is the basis of the above researches.In present work,several Fe-Zr based reactor materials systems have been selected as the objects of thermodynamic studies.The main achievements of the present work are as follows:1)To establish the thermodynamic database for U-Zr-Nb-Sn-Cu-Fe-Cr-Ni-O-Hf nuclear reactor system,thermodynamic assessments of some key Fe-Zr based subsystems have been selected to study at first:Fe-Zr-Hf,Fe-Zr-Cu,Fe-Zr-Cr-Ni and Fe-Zr-U-O systems.Based on the experimental data of phase diagram and thermodynamic properties in the literature,15 subbinary systems are reviewed.The Fe-Zr,Fe-O,U-O,Zr-O and Fe-U systems have been reoptimized to improve the accuracy of the related ternary systems.2)The istothermal sections of Fe-Zr-Hf system at 1173 K and 1373 K have been experimentally determined by alloy method.Coupled with the results of first-principles calculations,the thermodynamic database of Fe-Zr-Hf system has been established.In the experimental investigation of Fe-Zr-Hf system,it is confirmed that Fe₂₃Zr₆is not an oxygen-stabilized phase.Also,the formation mechanism of Fe₂₃Zr₆was discussed.3)Based on the thermodynamic properties and experimental data of the isothermal sections(853 K,973 K.1273 K,1373 K and 1473 K),the thermodynamic optimization of the Fe-Zr-Cu system has been performed by using the CALPHAD method coupled with the results of first-principles calculations.Based on the thermodynamic parameters,three thermodynamic methods have been employed to predict the glass forming range,the distribution of glass forming ability and the formation tendency of the separated amorphous.4)Thermodynamic description of the Fe-Zr-Cr,Fe-Zr-Ni,Zr-Cr-Ni and Fe-Cr-Ni systems were assessed and optimized by using the CALPHAD method.The thermodynamic database of Fe-Zr-Cr-Ni system was firstly constructed.It provides a thermodynamic basis for the study of the interaction between zirconium alloys and stainless steel under high temperature during service.5)Thermodynamic description of the Fe-U-O,Fe-Zr-O,Fe-Zr-U and O-U-Zr systems were assessed and optimized by using the CALPHAD method.The thermodynamic database of Fe-Zr-U-O system was firstly constructed.On the basis of the optimized Fe-Zr-U-O thermodynamic database,the liquid miscibility gap was calculated under a series of STFM-Fe experimental conditions in the MASCA project.The composition distributions of the two kinds of liquid were obtained respectively,compared with the experimental results.According to the calculation results of present work,it is confirmed that the two-layer corium pool configuration is stable in thermodynamic equilibrium state.