Updated Liquid Secondary Waste Grout Formulation and Preliminary Waste Form Qualification

Saslow, Sarah A.; Um, Wooyong; Russell, Renee L.; Wang, Guohui; Asmussen, R. Matthew; Sahajpal, Rahul

doi:10.2172/1373004

Cited by 8 publications

(7 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In light of these challenges and through recent CWF development efforts that embrace the evolving chemical and mineralogical composition of an aging CWF, 10 interface between the cementitious material and its surrounding environment, the forefront of oxidation and chemical change. This phenomenon leads to the formation of cementitious mineral phases, such as ettringite, theoretically capable of incorporating TcO 4 − into their structure.…”

Section: ■ Introductionmentioning

confidence: 99%

“…In light of these challenges and through recent CWF development efforts that embrace the evolving chemical and mineralogical composition of an aging CWF, the work described herein presents the first experimental evidence for the capture of TcO 4 – in ettringite [Ca 6 Al 2 (SO 4 ) 3 (OH) 12 ·26(H 2 O)], a mineral naturally formed in CWFs. As suggested by a study of ancient cementitious materials, secondary mineral phases continuously dissolve and precipitate at the interface between the cementitious material and its surrounding environment, the forefront of oxidation and chemical change.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Immobilizing Pertechnetate in Ettringite via Sulfate Substitution

Saslow

Kerisit

Varga

et al. 2020

Environ. Sci. Technol.

Self Cite

View full text Add to dashboard Cite

Technetium-99 immobilization in low-temperature nuclear waste forms often relies on additives that reduce environmentally mobile pertechnetate (TcO 4 − ) to insoluble Tc(IV) species. However, this is a short-lived solution unless reducing conditions are maintained over the hazardous life cycle of radioactive wastes (some ∼10,000 years). Considering recent experimental observations, this work explores how rapid formation of ettringite [Ca 6 Al 2 (SO 4 ) 3 (OH) 12 •26(H 2 O)], a common mineral formed in cementitious waste forms, may be used to directly immobilize TcO 4 − . Results from ab initio molecular dynamics (AIMD) simulations and solid-phase characterization techniques, including synchrotron X-ray absorption, fluorescence, and diffraction methods, support successful incorporation of TcO 4 − into the ettringite crystal structure via sulfate substitution when synthesized by aqueous precipitation methods. One sulfate and one water are replaced with one TcO 4 − and one OH − during substitution, where Ca 2+ -coordinated water near the substitution site is deprotonated to form OH − for charge compensation upon TcO 4 − substitution. Furthermore, AIMD calculations support favorable TcO 4 − substitution at the SO 4 2− site in ettringite rather than gypsum (CaSO 4 •2H 2 O, formed as a secondary mineral phase) by at least 0.76 eV at 298 K. These results are the first of their kind to suggest that ettringite may contribute to TcO 4 − immobilization and the overall lifetime performance of cementitious waste forms.

show abstract

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Immobilizing Pertechnetate in Ettringite via Sulfate Substitution

Saslow

Kerisit

Varga

et al. 2020

Environ. Sci. Technol.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Fly ash (FA), which qualifies as class C and F, was provided by the Centralia, Washington power plant 35 . Grade 100 blast furnace slag (BFS) and Type I/II ordinary portland cement (OPC) were both supplied by Lafarge North America Inc (Seattle, Washington).…”

Section: Methodsmentioning

confidence: 99%

“…The HGM‐5 formulation has a low reducing capacity, consisting of a dry ingredient mix containing 75 wt% FA and 25 wt% OPC and mixed at a water‐to‐dry‐mix (wdm) ratio of 0.29. The second formulation, Cast Stone (CS), is a more reducing formulation that has been the focus of Hanford waste form development efforts over the past decade 35,38–40 . CS consists of 45 wt% FA, 8 wt% OPC and 47 wt% BFS mixed at a wdm ratio of 0.45.…”

Section: Methodsmentioning

confidence: 99%

An exploration of benchtop X‐ray emission spectroscopy for precise characterization of the sulfur redox state in cementitious materials

et al. 2021

Self Cite

View full text Add to dashboard Cite

The evolution of sulfur chemistry in cements is best known in the bailiwick of failure mechanisms via sulfate attack, but is equally important for its contributions to the reduction capacity of cementitious materials often used for immobilizing nuclear waste streams destined for long‐term storage, for example, cementitious waste forms (CWF). The total reduction capacity of CWFs, encompassing contributions from both S and Fe reductants, and its implications toward radionuclide immobilization is most often studied by destructive wet chemistry methods requiring acid digestion in the presence of Ce(IV) and subsequent titration and colorimetric interpretation. Here, we investigate a similarly analytical but nondestructive alternative, benchtop high resolution wavelength‐dispersive X‐ray fluorescence spectroscopy, most commonly known as X‐ray emission spectroscopy (XES), for probing the bulk sulfur oxidation state distribution. We present here an initial investigation of S XES, including an improved experimental protocol for lab XES of inhomogeneous samples, both as a complement to the Ce(IV) test and for new scientific opportunities that it enables for observing changes in sulfur chemistry. We discuss future improvements and opportunities, including: (1) the practical challenges associated with coordinating XES and Ce(IV) liquid extraction for a more comprehensive perspective on reduction capacity and for a high‐precision evaluation of uncertainties in the Ce(IV) test; and (2) new opportunities, due to the nondestructive nature of XES, for controlled evolution studies aimed at elucidating specific chemical responses of CWFs exposed to invasive gas or liquid species or to accelerated aging by radiative dose or thermal treatment.

show abstract

“…The dry blend mix was then added slowly to an appropriate aliquot of the melter off-gas condensate evaporate waste sample just prior to making the grout specimens, and the waste-dry blend slurry then stirred until the paste appeared homogeneous (i.e., approximately 15 minutes in a lab-scale mixer). For consistency with previous work, mixing was done using the same equipment and laboratory procedures previously used to prepare secondary liquid waste Cast Stone samples (Saslow et al 2017a(Saslow et al , 2017b. The thoroughly mixed paste was transferred to plastic molds (right circular cylinders approximately 2 in.…”

Section: Cast Stone Monolith Preparationmentioning

confidence: 99%