Quantifying Dense Multicomponent Slurries with In-Line ATR-FTIR and Raman Spectroscopies: A Hanford Case Study

The multiphase nature of slurries can make them difficult to process and monitor in real time. For example, the nuclear waste slurries present at the Hanford site in Washington State are multicomponent, multiphase, and inhomogeneous. Current analytical techniques for analyzing radioactive waste at Hanford rely on laboratory results from an on-site analytical laboratory, which can delay processing speed and create exposure risks for workers. However, in-line probes can provide an alternative route to collect the necessary composition information. In the present work, Raman spectroscopy and attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy are tested on simulants of nuclear waste slurries containing up to 23.2 wt % solids. We observe ATR-FTIR spectroscopy to be effective in measuring the solution phase of the studied slurry systems (3.52% mean percent error), while Raman spectroscopy provides information about the suspended solids in the slurry system (18.21% mean percent error). In-line measurement of multicomponent solids typical of nuclear waste processing has been previously unreported. The composition of both the solution and solid phases is vital in ensuring stable glass formulation and effective disposal of nuclear waste at Hanford. Raman and ATR-FTIR spectroscopies can provide a safer and faster alternative for acquiring compositional information on nuclear waste slurries

Feedback Control of Multicomponent Salt Crystallization

A closed-loop strategy is developed for controlling batch cooling multicomponent crystallization. The strategy represents the sequential application of two established feedback control techniques: direct nucleation control followed by supersaturation control. Experimental results show that such a control scheme produces larger crystals (compared to linear cooling crystallization with the same batch time). In using this scheme to control the crystallization of a double salt from a solution containing sodium nitrate and sodium sulfate, we demonstrate the application of supersaturation control to a multicomponent salt crystallizationwhich requires knowledge of the solubility as a function of temperature, the ability to monitor concentrations in a multicomponent solution, and an appropriate expression for the driving force for crystallization of a salt. In this paper, a methodology for rapidly identifying the solubility of a solute in a multicomponent solution is presented and a new expression for supersaturationtermed the molar supersaturationis advanced as a measure of the driving force for crystallization of salts