| The electrochemical technology of molten salt has obvious advantages in the post-treatment separation of molten salt electrolytic refining and nuclear melt salt reactor,and has good application prospect and practical value in the separation and extraction of actinides in the post-treatment of spent fuel molten salt electrolysis.In the high temperature melting salt of spent fuel,the immediate detection and analysis of its metal ion concentration is very important to the separation of actinides,because it helps to predict or accurately judge the metal ions in advance.At present,both the elements in spent fuel and the diffusion behavior and concentration analysis of ions in molten salt electrolysis need to be sampled regularly,and then the method of off-line testing is used to analyze and judge the radioactive elements and their ion concentrations,but the method of sample making,sample measurement,The detection period is not conducive to the immediate analysis and process control of ion concentration in molten salt,so it is very urgent to develop on-line detection means in high temperature molten salt.The electrochemical technology of molten salt will be expected to realize the on-line detection and remote control of ion concentration in spent fuel post-treatment.Based on this,this paper uses electrochemical detection technology to simulate the substitution of radioactive elements with lanthanum element La3+,and makes a series of studies on the detection of La3+ion concentration in high temperature molten salt,the main work and results are as follows:Using electrochemical methods such as cyclic voltammetry?CV?,square wave voltammetry?SWV?and timing potential?CP?,the electrochemical reduction process of La3+on tungsten electrode was studied in LiCl-KCl-LaCl3 system with tungsten as working electrode and Ag/AgCl as reference electrode in 773K temperature.The results show that in three electrochemical methods,the reduction potential of La3+is around-2.10V,and the process of transferring three electrons in one step on tungsten electrode is La????La?0?,and the process is controlled by diffusion.It is calculated that the diffusion coefficient of La3+under the experimental conditions is 3.768×10-6cm2/s.Using SWV method to detect the concentration of La3+ions in LiCl-KCl-LaCl3 molten salt system at different LaCl3 levels at 773K temperature,the results show that the peak current of SWV curve increases with the increase of square wave amplitude,and in 5.03wt%LaCl3 and 6.26wt%LaCl3 concentration,The La3+ion concentration values(2.714×10-4mol/cm3,3.402×10-4 mol/cm3)detected by SWV are close to ICP test results(2.675×10-4mol/cm3,3.258×10-4 mol/cm3).At the higher concentration of 8.08 wt%LaCl3,the detected La3+concentration value is 5.671×10-5 mol/cm3,which is quite different from the ICP test result 5.046×10-4 mol/cm3,and after the error analysis,the corresponding diffusion coefficient value is simulated by numerical simulation of the equation,The obtained ion concentration value is 4.993×10-4 mol/cm3,which is basically consistent with the ICP test results.Therefore,the results obtained by SWV method at higher concentrations require an equation simulation correction of the diffusion coefficient value.Conventional pulsed voltammetry?NPV?Detection of molten salt system under different LaCl3 content was carried out to obtain the conventional pulse voltammetry curve of La3+on tungsten electrode at different pulse time.The results show that with the increase of scanning pulse time,the sedimentary current platform of metal La3+on tungsten electrode is shortened gradually,and the Faraday current platform tends to be flat.The data of conventional pulsed voltammetry curve are analyzed by electrochemical conventional voltammetry,and it is concluded that the range of ion concentration detected by NPV method is 1.124×10-4 mol/cm35.282×10-4 mol/cm3 in the 1.95wt%8.08wt%LaCl3 content range of molten salt.Compared with ICP test results,it is found that the ion concentration value of molten salt obtained by this method is close to that of ICP test,and the detection of NPV concentration is more accurate under a certain concentration range. |
PDF Full Text Request