Nuclear Waste Glass Corrosion JD VIENNA Pacific Northwest National Laboratory, Richland, WA ICTP-IAEA International School on Nuclear Waste Actinide Immobilization, September 10-14, Trieste, Italy PNNL-SA-138258
Outline Vitrification as a technology to immobilize radioactive wastes General glass corrosion Reaction rates Residual rates Acceleration or Stage III behavior Glass as a barrier Current models for prediction of glass corrosion Radiation impacts References 2
Nuclear Waste Glasses 3
Nuclear Waste Glasses Worldwide Vitrification is the reference technology to immobilize highly radioactive nuclear wastes worldwide Examples of sites producing alkali-borosilicate glasses for waste immobilization are listed Site Operated Melter Tech Produced Disposal Planned Glass Mass, t Glass Mass, t Disposal Pamela, Belgium 1985-1989 JHCM 650 650 Clay JHCM- Joule-heated AVM, France 1978-2012 HWIM 1,220 1,220 Clay ceramic melter LaHague, France 1989-Present HWIM,CCIM 7,032* NR Clay HWIM- Hot-walled induction melter Karlsruhe, Germany 2010-2012 JHCM 208 6,450* Salt or Clay CCIM- Cold-crucible Tokai, Japan 1995-Present JHCM 700 NR TBD induction melter Rokkasho, Japan TBD JHCM 0 NR* TBD Sellafield, UK 1990-Present HWIM 2,500* 2,700 TBD WVDP, US 1996-2002 JHCM 574 574 TBD DWPF, US 1996-Present JHCM 7,200 13,867 TBD WTP HLW, US TBD JHCM 0 32,000 TBD Based on Gin et al. 2013 WTP LAW, US TBD JHCM 0 527,838 Sand 4
Silicate Glass Structure Glass: an amorphous, metastable, solid Structure dependent on composition and temperature history Example Glass Example Crystal 5
Silicate Glass Structure, cont. [SiO 4 ] 4- tetrahedra form the primary “network” Additives and waste components chemically bound within solid Network formers (e.g., Si 4+ , B 3+ , P 5+ ) linking or “polymerizing” the anion complexes (e.g., SiO 4 4- ) leads to a 3D network coordination number of 3 or 4 (generally) Network modifiers (e.g., Na + , Ca 2+ ) breakup or “depolymerize” the network coordination number 6 to 8 (generally) Intermediates (e.g., Al 3+ , Fe 3+ ) can either reinforce the network (coordination number Modeled structure of ISG of 4) or depolymerize the network (typically for Du and Rimsza 2017 coordination number of 6 to 8) 6
Glass Structure, cont. Rings and Cages 5- and AlO 4 5- form three-dimensional network SiO 4 4- , BO 4 4 structure with ring size centered at around 6. 5 3 3 Si-B-Al 2.5 Si-B Si-Al Si Ring per base Si 2 1.5 1 0.5 0 0 5 10 15 20 Ring Size Xiang. et al. 2013 7
Composition Effects on Properties Important to U.S. Waste Glasses Oxide Al 2 O 3 B 2 O 3 CaO Cr 2 O 3 Fe 2 O 3 K 2 O Li 2 O MgO Na 2 O SiO 2 ZnO ZrO 2 Other Viscosity EC NiO, MnO T L , C T (spinel) PCT VHT Nepheline SO 3 , Cl , V 2 O 5 Salt MnO TCLP NiO Corrosion - Increase property - Decrease property - Small effect on property multiple arrows are for non-linear effects, first is for lower concentrations 8
Glass Composition Design A range of glass compositions are generated Glasses are designed to meet specific physical, Regulatory Chemical chemical, and regulatory compliance constraints Compliance Durability Glasses are designed specifically for waste Phase Conductivity compositions to be immobilized, examples: Stability Viscosity US tank waste primarily composed of cold chemicals with high composition variability and low radioactivity Loading and Cost French UOx HLW is primarily fission products and high radioactivity Radiation Performance related properties used in glass Stability Melter formulation are typically responses to one or Corrosion more standardized durability test, examples: 100 ° C Soxhlet 7-day, 90 ° C, Product Consistency Test (PCT) 28-day, 90 ° C, Materials Char. Center test 1 (MCC1) 200 ° C Vapor Hydration Test (VHT) Vienna 2014 & The Simpsons 9
Glass Compositions, wt% Oxide France Japan UK Belgium DWPF WTP HLW WTP LAW R7/T7 AVM P0798 Magnox AGR Blend Pamela WVDP Min Max Min Max Min Max Al 2 O 3 4.9 9.7 5.0 5.1 <0.1 1.9 20.2 6.0 4.3 9.8 2.0 18.9 6.1 6.1 B 2 O 3 14.0 17.0 14.2 16.8 18.0 18.3 25.6 12.9 4.3 8.3 4.0 20.0 10.0 10.0 BaO 0.6 0.3 0.5 0.5 0.6 1.2 - 0.2 - - - - 0 0 CaO 4.0 0.2 3.0 - - - 5.0 0.5 0.5 1.4 0 3.1 2.0 7.0 Cs 2 O 1.4 0.7 0.8 1.1 1.1 1.6 0 - - - - - 0 0 Fe 2 O 3 2.9 1.9 2.0 1.7 0.7 1.9 0.5 12.0 8.2 12.6 1.9 17.4 5.5 5.5 K 2 O - - - - - - - 5.0 - - 0 2.6 0.01 3.4 Li 2 O 2.0 0.4 3.0 4.0 4 4.8 3.5 3.7 3.5 5.6 0 6.0 0 4.3 MgO - 3.6 0 5.6 <0.1 1.3 - 0.9 0.3 2.2 - - 1.5 2.8 MoO 3 1.7 0.8 1.5 1.6 1.9 2.0 0 - - - - - - - Na 2 O 9.9 17.7 10.0 8.3 8.9 8.1 8.8 8 11.3 13.6 4.1 21.4 5.4 21.0 P 2 O 5 - 1.2 - 0.2 0.1 - - 1.2 0.2 0.6 0 2.5 0.0 1.4 SiO 2 45.5 41.4 46.6 46.0 49.2 46.3 35.3 41.0 44.8 54.6 31.0 53.0 43.3 50.1 TiO 2 - - - - - - - 0.8 0.0 0.7 0 0.1 1.4 1.4 ZnO 2.5 - 3.0 - - - 0 - - - 0 4.0 3.5 3.5 ZrO 2 2.7 1.0 1.5 1.6 1.8 2.4 0.1 1.3 0.1 0.2 0 13.5 3.0 3.0 [Ln,An] 2 O 3 4.9 3.1 6.1 4.2 10.1 8.4 0 4.6 1.0 3.5 0 8.5 - - 10 Minors 3.0 1.1 2.9 3.3 3.6 1.7 1.6 1.9 1.7 10.0 3 11.6 0 0.2
General Aspects of Silicate Glass Corrosion 11
General Observations 12 Vienna et al. 2013
General Observations, cont. Reactive Behaviors Transport Behaviors Solution + Dissolved • Selective dissolution of Species • Reactive transport of glass network 2 nd phase water and dissolved • Restructuring of glass to Transport Reactions Passivating Film species through tortuous form gel (dissolution Altered Glass passivating film reprecipitation under • Ion exchange in altered some conditions) material Base Glass • Evolution of gel structure • Dissolution of gel • Precipitation of 2 nd phases
General Observations, Cont. Gin et al. 2017 Vienna et al. 2001 Porous Pristine Gel Glass Solution Layer Secondary Often multi- Interdiffusion Zone Alteration layered (Ion Exchange Layer) 14 Products
Research Challenges Amorphous solid Very slow process converting to (compared to amorphous solid laboratory time frames) Unknown radiolysis Interface at small and radiation damage length-scale, often effects on alteration showing roughness Processes layer properties occurring at a buried interface Transport through Transition porous network that between water evolves over time as solvent to water as solute Multicomponent glasses (most of the periodic table) 15
Focus on Reaction Rates 16
Example Chemical Reactions Ion Exchange Hydrolysis Rieke et al. 2014 Condensation 17
Example Reaction Rate Model (without transport) Forward dissolution rate, r f = the rate at which glass dissolves into solution at specific values of the T and pH in the absence of back reactions Dissolution rate most likely to be directly impacted by structure and composition of glass 1 r f − potential E Q = − a r v k a exp 1 +other terms + i i 0 H RT K g r i = normalized glass dissolution rate E a = apparent activation energy, J mol -1 (based on element i ), g m -2 d -1 R = gas constant, J mol -1 K -1 r f = forward glass dissolution rate, g m -2 d -1 T = absolute temperature, K v i = stoichiometric coefficient for element i in glass Q = ion-activity product of rate controlling species k 0 = intrinsic rate constant, g m -2 d -1 K g = pseudo-equilibrium constant for glass a H+ = hydrogen ion activity σ = reaction order ( Temkin coefficient) η = pH power law coefficient (dependent on pH regime) 18
Isolation of Individual Effects Single-pass flow-through test (SPFT, ASTM C1662) can be used to measure effects of individual parameters Measure impacts of pH, T, [H 4 SiO 4 ] and [Al(OH) 4 - ] Avoid feed-back effects by high flow rate/surface area (q/s) Abraitis et al. 2000 Neeway et al. 2017 19
pH Impacts Hydrolysis rate depends on: Bond length and bond angle (stretched O-Si-O bonds favors hydrolysis) Site protonation (high or low pH) Knauss et al. 1990 20
Temperature Impacts Inagaki et al. 2012 Jollivet et al. 2012 21
H 4 SiO 4 Concentration Impacts Ferrand et al. 2006 22
Aluminate Effects Abraitis et al. 2000ab 23
What is New? 24
Glass Composition Effects on Forward Rate 19 glasses all measured by SPFT with systematic variation in pH (7 to 13) and T (23 ° to 90 ° C) Include broad range of compositions (US HLW glasses, US LAW glasses, International glasses) 25
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