Monitoring the Caustic Dissolution of Aluminum Alloy in a Radiochemical Hot Cell Using Raman Spectroscopy

Abstract

<jats:p> Chemical processing of highly radioactive materials commonly takes place in heavily shielded hot cells. The remote, real-time monitoring of chemical processing streams via optical spectroscopic techniques in hot cells may be particularly useful. Here, we describe the implementation of Raman spectroscopy and chemometric analysis to monitor the dissolution of aluminum-clad targets containing irradiated aluminum–neptunium oxide cermet pellets in caustic solutions in a hot cell environment. Partial least squares regression analysis was used to generate calibration models to quantify the concentration of dissolved aluminum, nitrate, and hydroxide in solutions within the radiochemical hot cell. This work explored a systematic approach to optimize a matrix of calibration standards using a D-optimal experimental design. The Design of Experiments-based regression model, in comparison to more traditional analytical approaches, was found to be the more practical method for building calibration models, with fewer samples, to obtain informative analytical data from Raman spectra. </jats:p>

Measuring Hydroxylammonium, Nitrate, and Nitrite Concentration with Raman Spectroscopy for ²³⁸Pu Supply Program

“…Because of the multicomponent nature of Raman spectra, many reports have demonstrated the use of multivariate regression analysis for species quantification. 17,18 Future work will include multivariate data analysis and compare prediction performance of partial least squares regression models to the detection limits achieved in this report. Another aspect to investigate further is the optimization of the method for determining preprocessing methods using optimal experimental design.…”

“…19,20 This increases the intensity of Raman scattering by 10 8 in some cases compared to normal Raman measurements. 18 Detection limits of <14 µM could be achieved with an excitation energy of 204 and 229 nm for nitrite and nitrate. 20 A third harmonic of a Coherent Inc. Infinity Nd:YAG laser in H 2 and a Coherent Inc. CW intracavity frequencydoubled argon ion laser could be used to obtain a 204 and 229 nm excitation source respectively.…”

Measuring Neptunium Concentration using Optical Spectrometry for the Pu-238 Supply Program

“…The water O-H stretching region (2,800-3,800 cm -1 ) comprises multiple overlapping H 2 O vibration and O--H stretching modes. 18 Changes in acid/base concentration, ionic strength, temperature, and electrolyte concentration distort the tetrahedral structure of water, which results in a spectral response that can be correlated to the concentration of analytes or external perturbation(s). A Raman system was tested in the hot cells for monitoring the caustic dissolution of aluminum alloy during Campaign 4.…”

Chemometrics and Experimental Design for the Quantification of Nitrate Salts in Nitric Acid: Near-Infrared Spectroscopy Absorption Analysis

“…30,31 Experimental designs have been used to extract training sets from a given factor space for chemometric analysis. 32,33 Thus, they are applicable to spectroscopic measurements taking place in harsh, restrictive, and expensive environments (e.g., a hot cell environment).…”

“…Developing methodology to determine the minimum number of samples, without sacrificing predictive capability, could be useful for quantitative measurements in hot cell environments. 33 Other methods, such as calibration transfer functions, have been tested to move calibration models from one location/instrument to another without requiring the expensive, time-consuming, and laborious task of running the entire training and validation sets under the new conditions. 34,35 This is especially challenging when the instrument used for the data acquisition is not the same as the one used for the calibration model and analytical conditions (e.g., temperature and humidity) are not comparable.…”