| At present,the proportion of nuclear energy in national energy structure is gradually increasing,and also plays an irreplaceable role in the field of national defense.Liquid lead-bismuth eutectic alloy(Lead-bismuth Eutectic,LBE)is considered as one of the preferred coolant materials for lead-based fast reactors and spallation targets in accelerator-driven subcritical systems(ADS)due to its excellent chemical and physical properties.In addition,lead-based fast reactors also have unique advantages in distributed generation,dynamical system for ships and aviation,and strategic weapons,and they are especially suitable for the miniaturization of strategic nuclear weapons and mobile nuclear power plants.However,LBE will lead to dissolution,oxidation and intergranular corrosion of iron-based structural materials,which seriously affects the performance of structural materials.Studies have shown that a certain of oxygen dissolved in LBE can promote the formation of protective oxides on the surface of the structural steel,which can prevent the further dissolution corrosion of the structural steel by LBE,thereby ensuring that the structural material can service in the reactors for a long time.However,the oxygen concentration in the LBE should not be too high,otherwise,a large amount of lead oxide scales will be formed and block the loop.Therefore,it is necessary to combine the electrochemical oxygen concentration measurement technology and the flow measurement technology to regulate oxygen concentration in lead-based reactor systems effectively.As the basis of studying the oxygen control performance of the technology of solid-phase oxygen control,firstly,the subject developed oxygen concentration measurement technology and flow rate measurement technology in the LBE fluid.Numerical method was used to pre-research the performance of the solid-phase oxygen control system with different schemes in regulating the oxygen concentration in the non-isothermal LBE loop,and also considering the influence from different boundary conditions.This pre-research work was used to guide the installation and operation of the solid-phase oxygen control system.Finally,a non-isothermal LBE loop with solid-phase oxygen control was built.Following the debugging of the facility was completed,the oxygen supply performance of the self-designed solid-phase oxygen control system was experimentally studied,and the influence of temperature and flow rate in MX on it was analyzed.At the same time,the performance of PbOs through different temperature ranges,heating rates and different flow rates during the experiment of oxygen control was analyzed.Different temperature limits,different heating and cooling rate,repeated tests and calibration experiments designed for research on the performance of oxygen sensor were researched,and displyed that the linear fitting degrees of measured temperature and the voltage measured by self-designed oxygen sensors with LSCF or LSM reference electrode materials are both more than 0.999.In the temperature range of 200 to 450℃,the maximum errors between calibrated voltage and theoretical value are less than 1 mV,and both the voltage difference of repeated measurements and the voltages fluctuation are acceptable.The oxygen sensors have good accuracy,stability and repeatability,and can withstand a heating rate of 1℃/3min(not the limitness).The permanent magnet electromagnetic flow meter(PMFs)is assembled and calibrated at the temperatures of 300 to 375℃.The linear fitting degree is good.The results indicated that the linear relationship between flow rate and output voltage is good,the zero offset can be ignored,and it meets the needs of measuring the low flow rate in high temperature liquid metals.The pre-study by numerical methods on the performance of the self-designed solid-phase oxygen control system at the non-isothermal LBE loop with solid-phase oxygen control technology displayed that the solid-phase oxygen control system should be installed in the hot zone(DELTA and MEXICO gantries taken this method)form the point of view of safety and rapid increase of oxygen concentration,and adjusting the temperature in the MX would be the effective way to quickly adjust the oxygen concentration in this system.Finally,the experimental study of solid-phase oxygen control was carried out.The experimental results indicated that the experimental loop and oxygen control system in this paper meets the requirements.Analysis of the loss rate of PbOs during about 200 hours experiments subjected to the heating rate of 1℃/3min,1℃/6min and erosion by LBE fluid at the speed of 0.43m/s or 0.84m/s indicated that the total average consumption rate of PbOs was similar to the average dissolution rate of PbOs that estimated from the experimentally measured oxygen concentration.It can be considered that the PbOs mainly loses its own mass in the way of dissolution,and the mass loss caused by the physical way is negligible.These researches provided reiable technical support for the measurement of oxygen concentration and flow rate in lead-based coolant cooling fast reactors,these have construction reference value for guiding oxygen concentration adjustment and system operation,and promoting the applicaton of lead-basied coolant cooling fast reactors. |
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