Research On Solid-phase Oxygen Control Of Lead-bismuth Eutectic

Accelerator Driven Sub-critical System(ADS)is considered to be one of the effective ways for transmutation of spent fuel of nuclear power plant.Liquid lead-bismuth eutectic(LBE)is the key material of spallation target in ADS and coolant of sub-critical reactor.Its compatibility to structural material,however,limits the application of LBE.Recent studies have demonstrated that with a certain amount of dissolved oxygen the LBE corrosion of structural material can be inhibited,provided that the oxygen concentration in liquid LBE can be precisely controlled.Therefore,the oxygen control technology in liquid LBE becomes one of the hot research topic.In this dissertation,we focus on the solid-phase oxygen control which is performed by the dissolution and precipitation of lead oxide(PbO)ceramic spheres in liquid LBE.The keys to the solid-phase oxygen control are the accuracy of oxygen concentration measurement,the preparation of PbO ceramic spheres and the design of mass exchangers.In this work,the associated theoretical and experimental investigations have been carried out with respect to these three key issues.Bi/Bi2O3 and Cu/Cu2O oxygen sensors were designed and developed.Associated performance tests and calibrations have been carried out.Bi/Bi2O3 and Cu/Cu2O oxygen sensors show good response speed and repeatability.The former one was chosen to be tested in LBE solid-phase oxygen control technology.Microwave-sintered PbO ceramic sphere technology was developed.Associated mechanical properties such as density,hardness and strength were evaluated.The results show that the mechanical properties of the PbO ceramic ball prepared by the microwave-sintered method are better than the mechanical properties of the traditional method,thus high quality oxygen source could be provided in the study.PbO ceramic balls prepared by this technique were used in the solid-phase oxygen control experiment in LBE,and they were also used in the verification experiment for erosion simulation.The results show that the structural integrity could be maintained under the dissolution and erosion of LBE.It is proposed that the consumption of PbO in solid oxygen control in LBE is not only caused by the dissolution,but also by the erosion effect in LBE.The pebble bed model was established,and the dissolution and erosion effects of PbO ceramic ball in LBE were studied by numerical simulation.An independent verification test was designed and completed,where the erosion effect was separated from the PbO dissolution in LBE.The numerical simulation results are consistent with the experiments in terms of dissolution and erosion respectively,but not for the case when dissolution-erosion are considered together.It is proposed that the combination of dissolution and erosion could not be treated as simple superposition.A mass exchanger was designed for solid-phase oxygen control experiments in liquid LBE system.Solid-phase oxygen control experiments and gas-phase oxygen control experiments were carried out and compared on the same platform.The results show the advantage of solid oxygen control technology in terns of oxygen control efficiency and cleaning.