Capabilities for Studying Temperature Dependence in Optical Spectra of Actinides in Support of the Plutonium-238 Supply Program

Optical spectroscopy is a powerful tool for the identification and quantification of actinide elements. However, spectral features are heavily influenced by temperature, which causes nonnegligible changes in peak position and intensity. To address this issue, work conducted at Oak Ridge National Laboratory (ORNL) is focused on developing capabilities for documenting and quantifying temperature-dependent changes in ultraviolet-visible-near infrared (UV-Vis-NIR) spectra of actinides of interest to the Plutonium-238 Supply Program, especially Np and Pu. ORNL's facilities, which include laboratory space and instrumentation dedicated to handling and accepting samples containing Np and Pu, are uniquely equipped to measure the spectra of these radioisotopes. This work discusses an experimental setup that enables heating solution-state samples and collecting in situ spectral data. Results from initial tests of this setup with the cold, inactive surrogate Nd are discussed. Spectra of Nd over a temperature range from 15°C to 45°C are presented; changes in the spectral features observed in the UV-Vis region are also presented.