| Liquid Lead-Bismuth Eutectic(LBE)has good physical and chemical properties,and is the preferred coolant material for lead-cooled fast reactor(LFR).However,LBE has a severe corrosive effect on structural material,which hinders the development of LFR.Research has found that maintaining the dissolved oxygen concentration in LBE within the range of 10’6 to 5×10-8 wt.%can effectively mitigate the corrosion of structural material by LBE.Oxygen concentration measurement and control are critical technologies that need to be realized urgently.Currently,the Pt/air and Bi/Bi2O3 oxygen sensors used for LBE oxygen concentration measurement have poor low-temperature testing performance and cannot meet the oxygen concentration measurement requirements below 300℃ in the cold leg of LFR.Therefore,there is still a need to develop wide-temperature-range LBE oxygen sensors suitable for low-temperature operation.In addition,electrochemical oxygen pump,as an effective means of precise oxygen control in small local areas of LBE,still need to improve their structural design and optimize material selection to improve their oxygen control efficiency.The lower temperature limit of oxygen sensor depends on the performance of the reference electrode.In this paper,step-cooling experiments were conducted on four types of reference electrodes,Cu/Cu2O,In/In2O3,LSCF/air,and LSM/air,to evaluate the low-temperature performance of the corresponding sensors.The electrochemical catalytic efficiency of the cathode powder has a significant impact on the operational characteristics and oxygen control efficiency of the oxygen pump.In this paper,a testing platform for LBE electrochemical oxygen pump was designed and built,and long-term precise control of LBE oxygen concentration was achieved using a PID control system.The operational characteristics and oxygen control efficiency of the oxygen pump with different cathode powders were investigated.The main research findings are as follows:(1)The accuracy,responsiveness,and stability of four different reference electrode oxygen sensors were evaluated in the temperature range of 450～200℃.The results showed that Cu/Cu2O,LSCF/air,and LSM/air oxygen sensors exhibited good overall performance at temperatures above 250℃,200℃,and 350℃,respectively,in the testing environment.However,the measurement value of the In/In2O3 reference electrode showed significant deviation from theory and further development is needed.(2)Feasibility verification experiment were conducted on a single LSCF oxygen pump.The results showed that the oxygen pump could achieve oxygen concentration control in the range of 1.72×10-6～1.25×10-4 wt.%in 800mL LBE at 450℃.(3)Five LSCF oxygen pumps were used to work together,and PID automatic control of oxygen concentration in 800mL LBE at 450℃ was achieved.After increasing the number of oxygen pumps and cathode powder loading,the contact area between cathode powder and solid electrolyte increased by 10 times,and the oxygen control rate of oxygen pumps increased by 8.5 times accordingly.The oxygen concentration could be stably controlled around 6.23×10-6 wt.%for at least 117 hours with a control error of less than 1%.(4)Oxygen control efficiency tests were conducted on oxygen pumps using LSCF,LSM,LSCF-GDC,and Cu/Cu2O as cathode powders in the oxygen concentration range of 2.25 X 10-5-1.63×10-5 wt.%at 450℃.The results showed that LSCF oxygen pump exhibited higher electrochemical catalytic efficiency than LSM oxygen pump.The contact area of LSCF with oxygen played a dominant role in the cathode electrochemical catalytic efficiency,leading to lower oxygen control efficiency after GDC doping in LSCF.Cu/Cu2O was not suitable for application in oxygen pumps as a cathode powder,as it could not replenish consumed oxygen ions. |
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