Study On Radiolytic Behavior Of Aqueous Solution Containing Copper Ion And Its Applications

In the field of nuclear materials,copper and copper alloys can be used as copper corrosion barrier for spent fuel deep geologic repositories,and as heat sink materials for water-cooled divertor in fusion reactors.However,during the service life of these materials,the radioactive liquid waste in the repository and the coolant in the watercooled circuit of divertor will undergo radiolysis under ionizing radiation,generating a series of radiolytic products.H2O2 and O2 in the radiolytic products can induce corrosion of the copper corrosion barrier and heat sink material,resulting in the release of a certain amount of copper ions into the system.The copper ions can then participate in radiolytic reactions as reactants,changing the reaction process,altering the concentration of radiolytic products,and affecting the chemical environment of the system,ultimately influencing the electrochemical corrosion environment of the materials.Therefore,the study of the radiolytic behavior of aqueous solution containing copper ion has far-reaching significance for the corrosion control of copper and copper alloys under radiolysis in aqueous solution systems.This paper mainly focuses on the study of the radiolytic behavior of aqueous solution containing copper ion,the radiolytic kinetic study of the coolant of watercooled divertor under operating conditions of China Fusion Engineering Test Reactor(CFETR),and the calculation study of the electrochemical corrosion potential(ECP)of CuCrZr heat sink material in the CFETR water-cooled divertor.Research has been conducted on the radiolytic behavior and its applications of aqueous solution containing copper ion,and the main research results are as follows:1.A combined approach of simulation and experimentation was used to study the radiolytic behavior of aqueous solution containing copper ion.y-radiolysis experiments were conducted on aqueous solution containing copper ion to investigate the effects of absorbed dose,dose rate,and Cu2+concentration on the generation of H2O2,O2,and H2.The results showed that with an increasing absorbed dose,the concentrations of H2O2 and H2(g)increased first and then stabilized,while the concentration of O2(g)remained largely unchanged.The presence of Cu2+promoted the generation of H2 and H2O2,increasing their equilibrium concentrations by one and two orders of magnitude,respectively,but had little effect on the generation of O2.The equilibrium concentrations of H2O2 and H2 increased with an increasing dose rate,but the equilibrium concentration of O2 was largely unaffected.Additionally,a calculation model for the radiolysis of aqueous solution containing copper ion was constructed based on the kinetics of water radiolysis and the twofilm theory of gas-liquid mass transfer.The simulation results were compared with experimental data,and the absolute value of normalized mean bias was mainly between 1%-7%,demonstrating the effectiveness,correctness,and expandability of the model.This work revealed the influence mechanism of copper ions on the radiolysis of system,and the constructed calculation model can accurately simulate the radiolytic behavior of aqueous solution containing copper ion under different radiation fields,which laid the foundation for future research on electrochemical corrosion control strategies for copper and copper alloys.2.A simulation of the radiolytic behavior of the coolant of the water-cooled divertor under CFETR operating conditions was performed using the calculation model for the radiolysis of aqueous solution containing copper ion.Based on the CFETR water-cooled divertor operational parameters,the effects of temperature,dissolved oxygen,H2O2 initial concentration,Cu2+ concentration,absorbed dose rate,and hydrogen injection on the coolant radiolysis under 14 MeV fusion neutron irradiation were calculated.The results showed that as the temperature increased,the equilibrium concentrations of H2O2,O2,and H2 generated by radiolysis decreased continuously,and the decrease became more gradual with higher temperatures.The equilibrium concentrations of H2O2,O2,and H2 generated by radiolysis increased with increasing dissolved oxygen,H2O2 initial concentration,Cu2+ concentration,and absorbed dose rate.Hydrogen injection can inhibit the generation of oxidative radiolytic products during the coolant radiolysis of the CFETR water-cooled divertor,but this inhibition effect had a marginal diminishing effect with an optimal hydrogen injection amount of 8 cc(STP)/kg H2O.This work thoroughly investigated the specific impacts of various operational parameters on the generation of the main coolant radiolytic products,providing insights for providing the optimal operational parameters for the CFETR water-cooled divertor.3.An experiment was conducted to determine the anodic polarization curve of CuCrZr,and the Tafel constant was found to be approximately 0.127.Then,based on the mixed potential model,an algorithm was designed and a calculation model for CuCrZr alloy ECP was established.Using the CFETR water-cooled divertor operational parameters as a reference,this model was used to calculate the effects of temperature,dissolved oxygen,H2O2 initial concentration,Cu2+concentration,absorbed dose rate,hydrogen injection and flow rate on the CuCrZr alloy ECP of the CFETR water-cooled divertor.A control strategy to inhibit the electrochemical corrosion of CuCrZr was proposed based on the calculation results:within a reasonable range,increase the coolant temperature and lower the flow rate,minimize the initial H2O2 concentration in the coolant,and inject hydrogen at a rate of 8 cc(STP)/kg H2O.This work demonstrates the specific application of the study on the radiolytic behavior of aqueous solution containing copper ion in the field of material corrosion control,providing valuable references for setting the water chemistry parameters of the CFETR water-cooled divertor heat sink material.This paper provided a series of basic data on the γ-radiolysis of aqueous solution containing copper ion,and deeply explored the influence mechanism of radiolysis.At the same time,calculation models for the radiolysis of aqueous solution containing copper ion and CuCrZr alloy ECP have been constructed.The above models can effectively simulate the radiolytic behavior of aqueous solution containing copper ion and the electrochemical corrosion environment of CuCrZr alloy under different environments,and have good scalability,which is helpful to study the generation of radiolytic products of aqueous solution containing copper ion under various conditions and evaluate the corrosion tendency of CuCrZr alloy under different application scenarios in order to explore corrosion control strategies.