Development of spectroscopic methods based on laser-induced plasma for selective detection of isotopic signatures in nuclear fuel cycle

Abstract

In the nuclear fuel cycle, isotope detection has a crucial role to establish nuclear security and nonproliferation system, and to improve the safety of nuclear power plants. However, conventional methods including mass spectrometry and radiation measurement are not suitable for real-time and in-situ detection. In this framework, the advanced detection system based on laser-induced plasma has been developed in the present study. The constructed system has been optimized and verified according to target isotopes and specific applications. Firstly, boron and iron isotopes associated with the safety of nuclear reactors have been investigated by using the molecular emission from laser-induced plasma. Boron isotopes in an aqueous solution could be analyzed with ppm level of detection limit and error below 1 %. In addition, the iron isotopes on structural material could be detected by a superior spatial resolution and sensitivity. The result indicates that constructed system could be utilized for the real-time monitoring of reactor coolant and decontamination of radioactive hot-spot. Secondly, the strontium and neodymium isotopes, the representative signature of nuclear forensics, have been analyzed by the constructed system. Using selective excitation by tunable wavelength laser, the resonant fluorescence and absorption spectra could be obtained. The isotopic abundance was be estimated with an error below 1 % by comparing the area of each peak without the calibration process. These results demonstrated that the present optical configuration could provide in-situ detection capability for nuclear forensic signatures. Consequently, the present study not only identified the unknown spectral features of isotopes but also demonstrated the detection capability of the constructed optical system in terms of resolution, sensitivity, and accuracy.