Evidence for dawsonite in Hanford high-level nuclear waste tanks

摘要: Gibbsite [Al(OH)3] and boehmite (AlOOH) have long been assumed to be the most prevalent aluminum-bearing minerals in Hanford high-level nuclear waste sludge. The present study shows that dawsonite [NaAl(OH)2CO3] is also a common phase tanks containing high total inorganic carbon (TIC) concentrations (relatively) low dissolved free hydroxide concentrations. Tank samples were probed for by X-ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive Spectrometry (SEM-EDS) Polarized Light Optical Microscopy. Dawsonite was conclusively identified four of six studied. In fifth tank (AN-102), identification less conclusive because it only observed as Na–Al bearing SEM-EDS. Four five had solid Na2CO3·H2O. one without observable (Tank C-103) lowest TIC content any tanks. amount C-103 insufficient convert aluminum (Al:TIC mol ratio 20:1). rest much lower Al:TIC ratios (between 2:1 0.5:1) than C-103. One (AZ-102) initially dawsonite, but not taken 15 months after NaOH added surface. When laboratory sample from AZ-102, solution consistent dissolution dawsonite. presence these significance large OH− consumed dissolution, an effect confirmed AZ-102 samples.