Study On Irradiation,lead-bismuth Corrosion And Its Cooperative Behavior Of Structural Material 12Cr2W2Mn F/M Steel In Lead-cooled Fast Reactor

The lead cooled fast reactor（LFR）is considered as one of the new generation fast nuclear systems in the Generation IV International Forum documents.The ferrite/martensite（F/M）steels are considered as one of the candidate for in-core and out-of core materials in LFR due to its good thermal conductivity,good irradiation resistance,excellent corrosion resistance.The LFR structural material would subject long-term neutron irradiation and liquid lead-bismuth alloy（LBE）corrosion in the actual situation,which can strongly affect the service time of F/M steels.Therefore,studying the effect of irradiation and LBE corrosion on F/M steel is very necessary.In this study,a 12Cr2W2Mn ferrite/martensite steel was developed for the lead cooled fast reactor,in order to investigate the irradiation and LBE corrosion behavior of F/M steel.A series experiments and characterization were carried out,the results are showing below:（1）Four kinds of F/M steels（original,hot rolling,cold rolling,hot rolling and cold rolling）were irradiated with Au ions at 400℃and 54 dpa.It was found that a large number of voids appeared in the samples after hot rolling.There were a lot of dislocations in the cold rolling samples before and after irradiation,and the radiation damage effect is not obvious.This is owing to the internal defects of F/M steel decreased after hot rolling,while the internal defects of F/M steel increased after cold rolling.The defects of the material itself will offset part of the irradiation damage,which leads to the irradiation damage of the sample aggravate after hot rolling,and the irradiation damage of the sample decreases after cold rolling.（2）The hot rolling F/M steel was irradiated with Au ions at different temperatures（RT,400℃）and different doses（25 dpa,54 dpa）.The results show that all the samples have dislocation wall,dislocation entanglement,voids and irradiated hardening phenomena after Au irradiation.The voids density increases with the increasing irradiation dose.The void size increases with the increasing irradiation temperature.The M₂₃C₆ phase amorphous phenomenon appears in F/M steel after irradiation.（3）The static LBE corrosion tests of four different（original,hot rolling,cold rolling,hot rolling and cold rolling）F/M steels were carried out at 400℃for 500 h.All of the samples were generated Fe/Cr-rich oxide products after corrosion tests.Comparing with the original sample,the corrosion layer thickness of the hot rolling sample became thinner,and the corrosion layer of the cold rolling sample became thicker.It is owing to the hot rolling sample has fewer defects and the cold rolling sample has more defects,and the defects will provide a channel for the diffusion of Fe,Cr and O atoms.Eventually,the LBE corrosion behavior of the hot rolling sample slows down,and the corrosion behavior of the cold rolling sample become strengthening.（4）The original samples were subjected to LBE corrosion experiments at different temperatures（400°C,500°C,600°C）for 500 h,and 600°C LBE corrosion experiments at different times（500 h,1000 h,2000 h）.The results show that as the corrosion temperature increasing,the thickness of the corrosion layer becomes thinner,and the LBE penetration phenomenon increases.As the corrosion time increasing,the surface oxide layer gradually falls off,and the sample has obvious grain boundary dissolution after 2000 h corrosion.（5）Taking the original sample as the research object,the proton irradiation experiment was carried out at 400℃and 0.27 dpa.Then the LBE corrosion experiment was carried out at 400℃and 500 h to study the LBE corrosion behavior of F/M steel under the low radiation dose.The results show that the Fe and Cr riched oxides were formed on the sample surface before and after proton irradiation.The corrosion product density and thickness of the corrosion layer of the sample after proton irradiation were smaller than that of unirradiated sample.It is owing to proton irradiation inducing a large amount of M₂₃C₆ phase on the surface of F/M steel,which hinders the diffusion of Fe,Cr,and O atoms,thereby slowing down the corrosion behavior of LBE.（6）Taking the original sample as the research object,the proton irradiation experiment was carried out at 400℃,54 dpa.Then the LBE corrosion experiment at 400℃for 100 h was carried out to study the LBE corrosion behavior of F/M steel under the high irradiation dose.The surface of the unirradiated sample has formed loose Fe₃O₄ particles of different sizes.After Au-ion irradiation,uniform and dense（Fe,Cr）₃O₄ particles are formed on the surface of the sample.It is owing to the defects introduced by the Au-ion irradiation providing a channel for O diffusion.The penetration of Au ion provides a channel,which makes it easier to generate oxides on the sample surface after Au ion irradiation.Resulting in an increasing LBE corrosion behavior of F/M steel after Au ion irradiation.The main innovations of the paper are as follows:（1）The irradiation and LBE corrosion properties of different rolling F/M steels（original,hot rolling,cold rolling,hot rolling and cold rolling）were studied to investigate the influence of irradiation and LBE corrosion on F/M.There are few reports on the effects of rolling process on F/M steel irradiation and LBE corrosion performance of the past similar works.This part of the research content can provide reference for future related research.（2）The self-built experimental equipment was used to conduct LBE corrosion experiments,in order to investigate the LBE corrosion performance and internal mechanism of F/M steel at different corrosion temperature and time.This provides an idea for future research on LBE corrosion.（3）The LBE corrosion behavior of F/M steel after proton and Au ion irradiation is studied,and the performance of F/M under the coupling condition of irradiation and LBE is studied.It is necessary to carry out the coupling experiments,but there are few researches about this aspect at present.This study has conducted a preliminary exploration on the coupling effect of irradiation and LBE corrosion,which provides a reference for subsequent related research.Based on the above results,we have a more comprehensive understanding of the radiation and LBE corrosion performance of the 12Cr2W2Mn F/M steel independently developed,and have a more in-depth study on the radiation and LBE corrosion mechanism,which is the structural material performance of the lead-cooled fast reactor.