scholarly journals Solution Chemistry for Actinide Borate Species to High Ionic Strengths: Equilibrium Constants for AmHB4O72+ And AmB9O13(OH)4(cr) and Their Importance to Nuclear Waste Management

MRS Advances ◽  
2017 ◽  
Vol 2 (13) ◽  
pp. 741-746 ◽  
Author(s):  
Yongliang Xiong
Keyword(s):  
Equilibrium Constant ◽  
Nuclear Waste ◽  
Equilibrium Constants ◽  
Pitzer Model ◽  
Solution Chemistry ◽  
Solubility Data ◽  
Glass Waste ◽  
Dissolution Reaction ◽  
Pitzer Parameters ◽  
High Level

ABSTRACTBorate is present in natural groundwaters and borate is also released into groundwaters when borosilicate glass, waste form for high level nuclear waste, is corroded. Borate can form an aqueous complex, AmHB4O72+, with actinides in +III oxidation state. In this work, we present our evaluation of the equilibrium constant for formation of AmHB4O72+ and the associated Pitzer interaction parameters at 25°C.Using Nd(III) as an analog to Am(III), solubility data of Nd(OH)3(s) in NaCl solutions in the presence of borate ion from the literature, is used to determine Am(III) interactions with borate. The log10K for the formation reaction is 37.34. This evaluation is in accordance with the Waste Isolation Pilot Plant (WIPP) thermodynamic model in which the borate species include B(OH)3(aq), B(OH)4–, B3O3(OH)4–, B4O5(OH)42–, and NaB(OH)4(aq). The WIPP thermodynamic database uses the Pitzer model to calculate activity coefficients of aqueous species.In addition, the equilibrium constant for dissolution of AmB9O13(OH)4(cr) at 25oC is evaluated from the solubility data on NdB9O13(OH)4(cr) in NaCl solutions, again using Nd(III) as an analog to Am(III). The log10K for the dissolution reaction is –79.30. In the evaluation for log10K for the dissolution reaction, AmHB4O72+ is also considered.The equilibrium constant and Pitzer parameters evaluated by this study will be important to describe the chemical behavior of Am(III) in the presence of borate in geological repositories.

The Effect of Temperature on the Redox Constraints for the Processing of High-Level Nuclear Waste into a Glass Waste Form

1989 ◽  
Vol 176 ◽  
Author(s):  
Henry D. Schreiber ◽  
Charlotte W. Schreiber ◽  
Margaret W. Riethmiller ◽  
J. Sloan Downey
Keyword(s):  
Oxygen Fugacity ◽  
Nuclear Waste ◽  
Metal Sulfide ◽  
Effect Of Temperature ◽  
Processing Temperature ◽  
Savannah River ◽  
Glass Waste ◽  
Oxidation Reduction ◽  
High Level Nuclear Waste ◽  
High Level

ABSTRACTThe oxidation-reduction equilibria of selected multivalent elements in an alkali borosilicate glass melt (Savannah River Laboratory frit #131) were measured as a function of the imposed oxygen fugacity over the temperature range from 950°C to 1350°C. Redox constraints on the processing of high-level nuclear waste into the glass melt require that the prevailing oxygen fugacity be about 10−5 to 10−12 Zatm at 950°C, about 10−2 to 10−9 atm at 1150°C, and about 100 to 10−7 atm at 1350°C. Such conditions circumvent foaming under oxidizing situations and metal/sulfide precipitation if the system becomes too reducing. The defined oxygen fugacity ranges correspond to the previously prescribed range of 0.1 to 0.5 for the [Fe2+]/[Fe3+] ratio in the resulting glass, independent of the processing temperature from 950°C to 1350°C.

The reaction of reference commercial nuclear waste glasses during gamma irradiation in a saturated tuff environment

1988 ◽  
Vol 3 (3) ◽  
pp. 576-597 ◽  
Author(s):  
John K. Bates ◽  
William L. Ebert ◽  
Donald F. Fischer ◽  
Thomas J. Gerding
Keyword(s):  
Gamma Irradiation ◽  
Radiation Exposure ◽  
Nuclear Waste ◽  
Current Data ◽  
Solution Chemistry ◽  
Nuclear Waste Repository ◽  
Exposure Rate ◽  
Reaction Products ◽  
High Level Nuclear Waste ◽  
High Level

The effects of gamma irradiation on groundwater and the reaction between groundwater and glass have been investigated at radiation exposure rates of 2 × 105 1 × 103 and 0 R/h. These experiments, which bound the conditions that may occur in a high-level nuclear waste repository located in tuff, have been performed using the actinide-containing glasses ATM-lc and ATM-8, and have been performed for time periods up to 278 days. The experimental results indicate that when only the repository groundwater is present, the pH of the system remains near-neutral, regardless of the radiation field, due to the buffering capacity of the solution. When glass is added to the system, the subsequent reaction is governed by the solution chemistry, which results from a complex interaction between radiolysis products, glass reaction products, and groundwater components. While no long-term reaction trends have been extracted from the current data, it is noted that there are no outstanding differences in the reaction of the glasses as measured by the release of the soluble components B, Mo, and Na, as a function of radiation exposure rate. However, there is a marked difference in the amount of U, Np, and Pu released from the glasses as a function of radiation exposure rate. This difference can be correlated with the pH values of the leachate, with more basic solutions resulting in lower actinide release.

scholarly journals Review of corrosion interactions between different materials relevant to disposal of high-level nuclear waste

2020 ◽  
Vol 4 (1) ◽  
Author(s):  
Xiaolei Guo ◽  
Stephane Gin ◽  
Gerald S. Frankel
Keyword(s):  
Nuclear Waste ◽  
Borosilicate Glass ◽  
Solution Chemistry ◽  
Metal Alloys ◽  
Waste Forms ◽  
Open Questions ◽  
Environmental Attributes ◽  
Temperature Solution ◽  
High Level Nuclear Waste ◽  
High Level

Abstract This review covers the corrosion interactions between different materials that are relevant to the disposal of high-level nuclear waste, in particular the waste forms and containers. The materials of interest are borosilicate glass, crystalline ceramics, metal alloys, and any corrosion products that might form. The available data show that these interactions depend on the structure, chemistry, thermodynamic history, and proximity of the materials in contact, as well as the environmental attributes, such as temperature, solution chemistry, and radiation. Several key mechanisms that govern these interactions are highlighted. Scientific gaps and open questions are summarized and discussed.

scholarly journals Corrosion of ternary borosilicate glass in acidic solution studied in operando by fluid-cell Raman spectroscopy

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Christoph Lenting ◽  
Thorsten Geisler
Keyword(s):  
Raman Spectroscopy ◽  
Nuclear Waste ◽  
Numerical Models ◽  
Adsorbed Water ◽  
Corrosion Mechanism ◽  
Borosilicate Glasses ◽  
Long Term Storage ◽  
In Operando ◽  
High Level ◽  
Fluid Cell

AbstractFluid-cell Raman spectroscopy is a space and time-resolving application allowing in operando studies of dynamic processes during solution–solid interactions. A currently heavily debated example is the corrosion mechanism of borosilicate glasses, which are the favoured material for the immobilization of high-level nuclear waste. With an upgraded fluid-cell lid design made entirely from the glass sample itself, we present the polymerization of the surface alteration layer over time in an initially acidic environment, including the differentiation between pore and surface-adsorbed water within it. Our results support an interface-coupled dissolution-precipitation model, which opposes traditional ion-exchange models for the corrosion mechanism. A sound description of the corrosion mechanism is essential for reliable numerical models to predict the corrosion rate of nuclear waste glasses during long-term storage in a geological repository.

scholarly journals Ab Initio Investigation of Helium Mobility in La2Zr2O7 Pyrochlore

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 667
Author(s):  
Yanxia Lu ◽  
Qing Peng ◽  
Chenguang Liu
Keyword(s):  
Nuclear Waste ◽  
Density Functional ◽  
Minimum Energy ◽  
Elastic Band ◽  
Waste Forms ◽  
Band Method ◽  
And Migration ◽  
High Level ◽  
Migration Pathways ◽  
Nuclear Waste Forms

The α-decay of incorporated actinides continuously produces helium, resulting in helium accumulation and causing security concerns for nuclear waste forms. The helium mobility is a key issue affecting the accumulation and kinetics of helium. The energy barriers and migration pathways of helium in a potential high-level nuclear waste forms, La2Zr2O7 pyrochlore, have been investigated in this work using the climbing image nudged elastic band method with density functional theory. The minimum energy pathway for helium to migrate in La2Zr2O7 is identified as via La–La interstitial sites with a barrier of 0.46 eV. This work may offer a theoretical foundation for further prospective studies of nuclear waste forms.

Transmutation of high-level nuclear waste by means of accelerator driven system

2013 ◽  
Vol 3 (1) ◽  
pp. 60-69 ◽  
Author(s):  
Hamid Aït Abderrahim ◽  
Didier De Bruyn ◽  
Gert Van den Eynde ◽  
Sidney Michiels
Keyword(s):  
Nuclear Waste ◽  
Driven System ◽  
High Level Nuclear Waste ◽  
Accelerator Driven System ◽  
High Level

scholarly journals High Level Waste (HLW) Vitrification Experience in the US: Application of Glass Product/Process Control to Other HLW and Hazardous Wastes

2008 ◽  
Vol 1107 ◽  
Author(s):  
Carol M. Jantzen ◽  
James C. Marra
Keyword(s):  
Process Control ◽  
High Level Waste ◽  
Glass Product ◽  
Mechanistic Models ◽  
Glass Waste ◽  
Statistical Process ◽  
Feed Composition ◽  
Feed Forward ◽  
Bonding Structure ◽  
High Level

AbstractVitrification is currently the most widely used technology for the treatment of high level radioactive wastes (HLW) throughout the world. At the Savannah River Site (SRS) actual HLW tank waste has successfully been processed to stringent product and process constraints without any rework into a stable borosilicate glass waste since 1996. A unique “feed forward” statistical process control (SPC) has been used rather than statistical quality control (SQC). In SPC, the feed composition to the melter is controlled prior to vitrification. In SQC, the glass product is sampled after it is vitrified. Individual glass property models form the basis for the “feed forward” SPC. The property models transform constraints on the melt and glass properties into constraints on the feed composition. The property models are mechanistic and depend on glass bonding/structure, thermodynamics, quasicrystalline melt species, and/or electron transfers. The mechanistic models have been validated over composition regions well outside of the regions for which they were developed because they are mechanistic. Mechanistic models allow accurate extension to radioactive and hazardous waste melts well outside the composition boundaries for which they were developed.

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