Study On The Measurement Of Uranium Isotope Ratio By Laser Ablation Absorption Spectroscopy

The rapid,on-site and non-contact isotope analysis of solid materials is extremely important in many applications,such as nuclear proliferation monitoring and forensics,geochemistry,archaeology,and biochemistry.In order to realize the simple,rapid and accurate measurement of uranium isotope ratio in solid samples,and to lay the foundation for the subsequent development of portable isotope ratio measuring instruments,the dissertation uses laser ablation technology as the method of sample atomization treatment to induce plasma on the sample surface.Combining laser ablation technology and semiconductor absorption spectroscopy technology,using spectroscopy methods to analyze the atoms,in the laser-induced plasma,so as to obtain relevant information about the isotope in the sample.This method has the advantages of non-contact,real-time and fast speed,no special requirements for solid sample preparation,high sensitivity and high spectruml resolution.Based on the above requirements,a set of laser ablation absorption spectroscopy experimental measurement equipment was designed and developed in the laboratory,and the measurement of the uranium isotope ratio in solid samples was carried out using laser ablation absorption spectroscopy technology.The dissertation focuses on the rapid,non-destructive and accurate detection of uranium isotope ratio in solid materials,and uses laser ablation absorption spectroscopy to carry out theoretical and experimental analysis of uranium isotope ratio measurement.The main work and innovations of the dissertation are as follows:1.Based on the measurement scheme of laser ablation and tunable semiconductor laser absorption spectroscopy technology,a set of uranium isotope ratio high-precision experimental measurement and analysis device was designed and developed,which solved the real-time online analysis of trace components in solid materials(nuclear materials).2.By optimizing the selection of measurement core parameters,the high-resolution and high-sensitivity absorption spectrum of aluminum atoms in alloy steel standard samples with different aluminum content were measured,and the calibration relationship between aluminum element content and absorption intensity was established.The correlation between aluminum content and absorption intensity is better than 0.999,and it has a high detection sensitivity with a detection limit of 0.066%(3?).The experimental results fully verified the feasibility of the laser ablation absorption spectroscopy technology and the established experimental measurement device for the analysis of metal elements and isotopes in solid materials.3.The experiment has studied the laws of plasma temperature,particle number density distribution,expansion speed(including lateral and longitudinal expansion speed)and other state parameters in the evolution process of laser ablation plasma,which lays a foundation for further understanding of the evolution process of laser ablation plasma.It also provides a basis for the optimization and selection of subsequent experimental parameters.Under optimized experimental conditions,high-resolution absorption spectrum of 235U and 238U were measured.The measurement and statistical analysis of the absorption spectrum of samples with different contents show that the 235U absorption sigcal has good linearity,the fitting correlation coefficient is 0.989,the detection limit is 0.033%(3?),and the measurement accuracy of the uranium isotope ratio is 0.524%(the 235U content is 4.95%).Laser ablation combined with tunable semiconductor laser absorption spectroscopy technology is suitable for the measurement and analysis of uranium isotope ratio.In the future,real-time rapid and high-precision measurement of uranium isotope ratio can be gradually realized in the complex radioactive environment of the field.This technology can be applied to the isotope ratio measurement of other elements of interest,such as Pu,Li,Pb,etc.The laser ablation absorption spectroscopy technology has great application potential in the rapid isotope analysis of nuclear fuel.