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Title: Waste form evaluation for RECl 3 and REO x fission products separated from used electrochemical salt

Abstract

The work presented here is based off the concept that the rare earth chloride (RECl 3) fission products within the used electrorefiner (ER) salt can be selectively removed as RECl 3 (not yet demonstrated) or precipitated out as a mixture of REOCl and REO x through oxygen sparging (has been demonstrated). This paper presents data showing the feasibility of immobilizing a mixture of RECl 3s at 10 mass% into a 78%TeO 2-22%PbO glass while also showing that this same mixture of RECl 3s can be oxidized to REOCl at 300 °C and then to REO x by 1200 °C, evolving Cl 2(g). When the REO x mixture is heated at temperatures >1200 °C, the ratios of REO xs change. The mixture of REO x was then immobilized in a lanthanide borosilicate (LABS) glass at a high loading of 60 mass%. Both the 78%TeO 2-22%PbO glass and LABS glass systems show good chemical durability. In conclusion, the advantages and disadvantages of tellurite and LABS glasses are compared.

Authors:
ORCiD logo [1];  [2];  [1];  [1];  [1];  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Energy Northwest, Richland, WA (United States)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1395356
Report Number(s):
PNNL-SA-124232
Journal ID: ISSN 0149-1970; PII: S0149197017302226
Grant/Contract Number:
AC05-76RL01830
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Progress in Nuclear Energy
Additional Journal Information:
Journal Name: Progress in Nuclear Energy; Journal ID: ISSN 0149-1970
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; Electrorefiner; Tellurite glass; LABS glass

Citation Formats

Riley, Brian J., Pierce, David A., Crum, Jarrod V., Williams, Benjamin D., Snyder, Michelle M. V., and Peterson, Jacob A. Waste form evaluation for RECl3 and REOx fission products separated from used electrochemical salt. United States: N. p., 2017. Web. doi:10.1016/J.PNUCENE.2017.09.005.
Riley, Brian J., Pierce, David A., Crum, Jarrod V., Williams, Benjamin D., Snyder, Michelle M. V., & Peterson, Jacob A. Waste form evaluation for RECl3 and REOx fission products separated from used electrochemical salt. United States. doi:10.1016/J.PNUCENE.2017.09.005.
Riley, Brian J., Pierce, David A., Crum, Jarrod V., Williams, Benjamin D., Snyder, Michelle M. V., and Peterson, Jacob A. 2017. "Waste form evaluation for RECl3 and REOx fission products separated from used electrochemical salt". United States. doi:10.1016/J.PNUCENE.2017.09.005.
@article{osti_1395356,
title = {Waste form evaluation for RECl3 and REOx fission products separated from used electrochemical salt},
author = {Riley, Brian J. and Pierce, David A. and Crum, Jarrod V. and Williams, Benjamin D. and Snyder, Michelle M. V. and Peterson, Jacob A.},
abstractNote = {The work presented here is based off the concept that the rare earth chloride (RECl3) fission products within the used electrorefiner (ER) salt can be selectively removed as RECl3 (not yet demonstrated) or precipitated out as a mixture of REOCl and REOx through oxygen sparging (has been demonstrated). This paper presents data showing the feasibility of immobilizing a mixture of RECl3s at 10 mass% into a 78%TeO2-22%PbO glass while also showing that this same mixture of RECl3s can be oxidized to REOCl at 300 °C and then to REOx by 1200 °C, evolving Cl2(g). When the REOx mixture is heated at temperatures >1200 °C, the ratios of REOxs change. The mixture of REOx was then immobilized in a lanthanide borosilicate (LABS) glass at a high loading of 60 mass%. Both the 78%TeO2-22%PbO glass and LABS glass systems show good chemical durability. In conclusion, the advantages and disadvantages of tellurite and LABS glasses are compared.},
doi = {10.1016/J.PNUCENE.2017.09.005},
journal = {Progress in Nuclear Energy},
number = ,
volume = ,
place = {United States},
year = 2017,
month = 9
}

Journal Article:
Free Publicly Available Full Text
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  • The work presented here is based off the concept that the rare earth chloride (RECl3) fission products mixture within the used electrorefiner (ER) salt can be selectively removed as RECl3 (not yet demonstrated) or precipitated out as REOCl through oxygen sparging (has been demonstrated). This paper presents data showing the feasibility of immobilizing a mixture of RECl3’s at 10 mass% into a TeO2-PbO glass and it shows that this same mixture of RECl3’s can be oxidized to REOCl at 300°C and then to REOx by 1200°C. When the REOx mixture is heated at temperatures >1200°C, the ratios of REOx’s change.more » The mixture of REOx was then immobilized in a LABS glass at a high loading of 60 mass%. Both the TeO2-PbO glass and LABS glass systems show good chemical durability. The advantages and disadvantages of tellurite and LABS glasses are compared.« less
  • A model has been developed to represent the stresses developed when a molten, glass-bonded brittle cylinder (used to store nuclear material) is cooled from high temperature to working temperature. Large diameter solid cylinders are formed by heating glass or glass-bonded mixtures (mixed with nuclear waste) to high temperature (915°C). These cylinders must be cooled as the final step in preparing them for storage. Fast cooling time is desirable for production; however, if cooling is too fast, the cylinder can crack into many pieces. To demonstrate the capability of the model, cooling rate cracking data were obtained on small diameter (7.8more » cm diameter) glass-only cylinders. The model and experimental data were combined to determine the critical cooling rate which separates the non-cracking stable glass region from the cracked, non-stable glass regime. Although the data have been obtained so far only on small glass-only cylinders, the data and model were used to extrapolate the critical-cooling rates for large diameter ceramic waste form (CWF) cylinders. The extrapolation estimates long term cooling requirements. While a 52-cm diameter cylinder (EBR-II-waste size) can be cooled to 100°C in 70 hours without cracking, a 181.5-cm diameter cylinder (LWR waste size) requires 35 days to cool to 100°C. These cooling times are long enough that verification of these estimates are required so additional experiments are planned on both glass only and CWF material.« less
  • One of the main challenges faced by the nuclear industry is the long-term confinement of nuclear waste. Because it is inexpensive and easy to manufacture, cement is the material of choice to store large volumes of radioactive materials, in particular the low-level medium-lived fission products. It is therefore of utmost importance to assess the chemical and structural stability of cement containing radioactive species. Here, we use ab initio calculations based on density functional theory (DFT) to study the effects of 90Sr insertion and decay in C–S–H (calcium-silicate-hydrate) in order to test the ability of cement to trap and hold thismore » radioactive fission product and to investigate the consequences of its β-decay on the cement paste structure. We show that 90Sr is stable when it substitutes the Ca 2+ ions in C–S–H, and so is its daughter nucleus 90Y after β-decay. Interestingly, 90Zr, daughter of 90Y and final product in the decay sequence, is found to be unstable compared to the bulk phase of the element at zero K but stable when compared to the solvated ion in water. Furthermore, cement appears as a suitable waste form for 90Sr storage.« less
  • Molten salt electrochemical separation may be applied to accelerator-based conversion (ABC) and transmutation systems by dissolving the fluoride transport salt in LiCl-KCl eutectic solvent. The resulting fluoride-chloride mixture will contain small concentrations of fission product rare earths (La, Nd, Gd, Pr, Ce, Eu, Sm, and Y) and actinides (U, Np, Pu, Am, and Cm). The Gibbs free energies of formation of the metal chlorides are grouped advantageously such that the actinides can be deposited on a solid cathode with the majority of the rare earths remaining in the electrolyte. Thus, the actinides are recycled for further transmutation. Rockwell and itsmore » partners have measured the thermodynamic properties of the metal chlorides of interest (rare earths and actinides) and demonstrated separation of actinides from rare earths in laboratory studies. A model is being developed to predict the performance of a commercial electrochemical cell for separations starting with PUREX compositions. This model predicts excellent separation of plutonium and other actinides from the rare earths in metal-salt systems.« less