Effect Of Irradiation Damage On LBE Corrosion Of Martensitic Steel And Its Mechanism

The lead cooled fast reactor(LFR)using liquid Pb or lead bismuth eutectic(LBE)as coolant adopts a closed fuel cycle approach,which has good nuclear waste transmutation and fuel proliferation capabilities,as well as high safety and economic performance,and has broad application potential in the future.Although lead cooled fast reactors have a series of technological advantages and potential application prospects,material issues remain the main bottleneck problem that restricts the development of lead cooled fast reactors.How radiation damage affects liquid metal corrosion is one of the key scientific issues that urgently need to be addressed in the development of lead cooled fast reactors,and it is also a hot topic in the current research of lead cooled fast reactor structural materials.This article first uses He ion beams(350℃,2MeV,350℃,2.8MeV,500℃,1.4MeV)to conduct irradiation tests on SIMP/T91 steel.Then,static corrosion tests are conducted in liquid saturated oxygen concentration LBE(350℃,500℃)and low oxygen concentration LBE(500℃).Multiple characterization testing methods such as SEM,EDS,XRD are used to characterize the cross-sectional morphology of the sample and the structure of the oxidized layer after corrosion.The main research work includes the following aspects:(1)The effect of research time on corrosion:With the increase of corrosion time,the thickness of the corrosion oxidation layer of SIMP/T91 steel significantly increased,and a double-layer oxide film with an outer layer mainly composed of Fe3O4 and an inner layer mainly composed of(Fe,Cr)3O4 spinel was formed.However,as time went on,it was found that cracks appeared in the inner oxide layer,intensifying the diffusion of O element into the matrix and promoting corrosion.In addition,the growth kinetics law of the oxide layer in SIMP steel changed from h=0.054t0.4to h=0.067×exp(t/2185)+1.138,and the growth rate gradually decreased to increase.(2)Research on the Effect of Temperature on Corrosion:As the corrosion temperature increases,the thickness of the corrosion oxidation layer of SIMP/T91 steel significantly increases.The corrosion oxidation layer thickness of SIMP/T91 steel in a 500℃ LBE environment is greater than 5μm.The thickness of the corrosion oxide layer in a LBE environment at 350℃ is less than 2μm.The effect of temperature on corrosion is extremely significant.(3)Research on the effect of irradiation dose on corrosion:In an experimental environment of 350℃,the oxide layer thickness of samples with high irradiation dose has a certain increase compared to non irradiated samples;In an experimental environment at 500℃,the thickness of the corrosion oxide layer first increased and then decreased with the continuous increase of irradiation dose.At the same time,Cr2O3 was found in SIMP steel and T91 steel,and at irradiation dose of the formation of SiO2 was found in SIMP steel of 1×1017ions/cm2,indicating that high irradiation doses promote the precipitation of Cr and Si elements,forming a dense internal oxide layer to suppress corrosion.(4)When the oxygen concentration in LBE drops to 2×10-7wt%,F/M steel mainly exhibits dissolution corrosion,with no visible formation of oxide layer.At the same time,as the irradiation dose continues to increase,SIMP steel exhibits inhibition of dissolution corrosion.Enrichment of Si and Cr elements was found at the cross-section of the material,suggesting that the enrichment of Si and Cr elements hinders dissolution corrosion behavior.