Behavior of Np, Pu, Am, Tc Upon Glass Corrosion in a Concentrated Mg(Ca)Cl2Solution

1994 ◽  
Vol 353 ◽  
Author(s):  
Bernd Grambow ◽  
Andreas Loida ◽  
Lothar Kahl ◽  
Werner Lutze
Keyword(s):  
Salt Solution ◽  
Near Field ◽  
Fluid Phase ◽  
Glass Waste ◽  
Glass Dissolution ◽  
Glass Corrosion ◽  
Corrosion Studies ◽  
High Level ◽  
Drill Holes ◽  
Kinetics Of

AbstractThe objective of this investigation is to describe the extent to which Np, Pu, Am and Tc are mobilized from vitrified high-level radioactive waste into the near field of an HLW repository in a salt formation, when a hot and concentrated salt solution comes into contact with the glass. Waste form corrosion studies are conducted with a salt solution representing the composition of a fluid phase encountered in drill holes in the Gorleben salt dome. Test temperatures are determined by the designed maximum surface temperature of 200°C for the vitrified waste in the Gorleben salt. The following results were obtained: 1. pH changes of the radio-active leachate are the same as in inactive leachates. 2. The time and temperature dependence of the reaction for the radioactive glass are in excellent agreement with that of the inactive glass. 3. Np, Pu, Am, and Tc have not been reimmobilized in secondary minerals. Hence, mobilization of these radionuclides is governed by the kinetics of glass dissolution. Pu oxidation states were analyzed and related to Pu concentrations.

scholarly journals The initial dissolution rates of simulated UK Magnox–ThORP blend nuclear waste glass as a function of pH, temperature and waste loading

2015 ◽  
Vol 79 (6) ◽  
pp. 1529-1542 ◽  
Author(s):  
N. Cassingham ◽  
C.L. Corkhill ◽  
D.J. Backhouse ◽  
R.J. Hand ◽  
J.V. Ryan ◽  
...  
Keyword(s):  
Dissolution Kinetics ◽  
Intrinsic Rate ◽  
Waste Glass ◽  
High Level Waste ◽  
Dissolution Mechanism ◽  
Dissolution Rates ◽  
Forward Rates ◽  
Glass Dissolution ◽  
High Level ◽  
Kinetics Of

AbstractThe first comprehensive assessment of the dissolution kinetics of simulant Magnox–ThORP blended UK high-level waste glass, obtained by performing a range of single-pass flow-through experiments, is reported here. Inherent forward rates of glass dissolution were determined over a temperature range of 23 to 70°C and an alkaline pH range of 8.0 to 12.0. Linear regression techniques were applied to the TST kinetic rate law to obtain fundamental parameters necessary to model the dissolution kinetics of UK high-level waste glass (the activation energy (Ea), pH power law coefficient (η) and the intrinsic rate constant (k0)), which is of importance to the post-closure safety case for the geological disposal of vitreous products. The activation energies based on B release ranged from 55 ± 3 to 83 ± 9 kJ mol–1, indicating that Magnox–THORP blend glass dissolution has a surface-controlled mechanism, similar to that of other high-level waste simulant glass compositions such as the French SON68 and LAW in the US. Forward dissolution rates, based on Si, B and Na release, suggested that the dissolution mechanism under dilute conditions, and pH and temperature ranges of this study, was not sensitive to composition as defined by HLW-incorporation rate.

Modelling Radionuclide Speciation and Solubility Limits in The Near-Field of a Deep Repository

1985 ◽  
Vol 50 ◽  
Author(s):  
Hans Wanner
Keyword(s):  
Near Field ◽  
Cast Steel ◽  
Significant Rise ◽  
High Level Waste ◽  
Glass Waste ◽  
Carbonate Concentration ◽  
Realistic Description ◽  
Carbonate Complexation ◽  
Main Components ◽  
High Level

AbstractIn the safety analysis recently reported for a potential Swiss high-level waste repository, radionuclide speciation and solubility limits are calculated for expected granitic groundwater conditions. With the objective of deriving a more realistic description of radionuclide release from the near-field, an investigation has been initiated to quantitatively specify the chemistry of the near-field. In the Swiss case, the main components of the near-field are the glass waste-matrix, a thick cast steel canister horizontally stored in a drift, and a backfill of highly compacted bentonite.Based on available experimental data, an ion-exchange model for sodium, potassium, magnesium, and calcium has been developed, in order to simulate the reaction of sodium bentonite backfill with groundwater. The model assumes equilibrium with calcite as long as sufficient carbonates remain in the bentonite, as well as quartz saturation. The application of this model to the reference groundwater used in ‘Project Gewaehr 85’ results in a significant rise in pH (by up to 3 units) as well as a marked increase in the carbonate concentration.Neptunium and plutonium speciation and solubility limits are calculated for the reference groundwater chemistry gradually altered to that of saturated bentonite water and back again by a water exchange cycle model. The solubility limits estimated in this way generally turn out to be higher for the bentonite water than for the reference groundwater, mainly due to carbonate complexation of the actinide components AnO2+ and AnO22+. Uncertainties are particularly large for neptunium solubility due to its strong Eh dependence in bentonite water.

Laboratory and Modelling Studies of Sodium Benionite Grounmater Interaction

1986 ◽  
Vol 84 ◽  
Author(s):  
M. Sneujman ◽  
H. Uotiia ◽  
J. Rantanen
Keyword(s):  
Near Field ◽  
Chemical Species ◽  
Fluid Phase ◽  
High Level Waste ◽  
Sodium Bentonite ◽  
Model Calculations ◽  
Buffer Material ◽  
Modelling Studies ◽  
Calcite Saturation ◽  
High Level

AbstractAccording to the present Finnish concept sodium bentonite will be used as a buffer material in the repository for high-level waste. Experimental and theoretical studies treating the effect of bentonite upon the chemical conditions in a repository have been initiated with the object of specifying the chemistry of the near field.Sodium bentonite was let react with water under anaerobic conditions at 25°C for 540 days, during which time six fluid samples were extracted for the chemical analysis of 15 chemical species. The generated fluid phase was alkaline (PH = 9…10) and contained a high amount of bicarbonate. Also a low redox-potential was measured. The fluid phase chemistry was investigated using the geochemical code PHREEM. Calcite saturation was observed in all fluid samples.A modelling of sodium bentonite interaction with water based on the main mineral components of bentonite was also performed with PHREEQE. A fairly good agreement between experimental results and model calculations was observed.

Glass Degradation in Performance Assessment Models1

2015 ◽  
Vol 1744 ◽  
pp. 163-172 ◽  
Author(s):  
William L. Ebert
Keyword(s):  
Performance Assessment ◽  
Reactive Transport ◽  
Intrinsic Property ◽  
Secondary Phase ◽  
Simple Expression ◽  
Glass Waste ◽  
Residual Rate ◽  
Glass Dissolution ◽  
Kinetics Of

ABSTRACTThe interface with reactive transport models used in performance assessment calculations is described to identify aspects of the glass waste form degradation model important to long-term predictions. These are primarily the conditions that trigger the change from the residual rate to the Stage 3 rate and the values of those rates. Although the processes triggering the change and controlling the Stage 3 rate are not yet understood mechanistically, neither appears related to an intrinsic property of the glass. The sudden and usually significant increase in the glass dissolution rate suggests the processes that trigger the increase are different than the processes controlling glass dissolution prior to that change. Application of a simple expression that was derived for mineral transformation to represent the kinetics of coupled glass dissolution and secondary phase precipitation reactions is shown to be consistent with experimental observations of Stage 3 and useful for modeling long-term glass dissolution in a complex disposal environment.

Chemical durability of high-level waste glass in repository environment: main conclusions and remaining uncertainties from the GLASTAB and GLAMOR projects

2006 ◽  
Vol 932 ◽  
Author(s):  
P. Van Iseghem ◽  
K. Lemmens ◽  
M. Aertsens ◽  
S. Gin ◽  
I. Ribet ◽  
...  
Keyword(s):  
Near Field ◽  
Chemical Durability ◽  
High Level Waste ◽  
Model Parameters ◽  
Residual Rate ◽  
Geological Disposal ◽  
Glass Dissolution ◽  
Geologic Disposal ◽  
High Level

ABSTRACTThis paper reviews the main conclusions of two European Commission funded projects, GLASTAB and GLAMOR, on the durability of HLW glass in geological disposal, and the remaining uncertainties. The progress in GLASTAB relates to the characterization of the alteration layer, the modeling of glass dissolution, the interaction of glass with near field materials, the behaviour of radionuclides, and the calculation of HLW glass dissolution as part of geological disposal. The GLAMOR programme was focused on the decrease of the glass dissolution rate upon achieving silica saturation in solution. Two conclusions from this programme are the importance of the residual rate measured beyond silica saturation and the need to reduce the uncertainties in model parameters. The overall conclusion from the two projects is that strong progress has been achieved on basic dissolution mechanisms and interaction with disposal environments - HLW glass will act as a good barrier to the release of radionuclides in geologic disposal.

The Calorimetric-respirometric Ratio: Its Potential as a Cytotoxicity Test

1994 ◽  
Vol 22 (5) ◽  
pp. 364-376
Author(s):  
Richard B. Kemp ◽  
Catherine Stephansen ◽  
Sajid Mohamed ◽  
R.W. John Meredith
Keyword(s):  
Heat Flux ◽  
Salt Solution ◽  
Krebs Cycle ◽  
Cytotoxicity Test ◽  
Antimycin A ◽  
Rich Medium ◽  
Animal Cells ◽  
Normal Input ◽  
High Level ◽  
L929 Mouse

The ratio between heat flux and oxygen flux, the calorimetric ratio, is an enthalpy budget device used to identify anaerobic pathways in the presence of respiration. Ratios that are more exothermic (i.e. more negative) than the average for catabolic substrates (-450kJ mol O2 ± 5%; Thornton's rule), are usual for cells established in culture, including suspension-adapted LS-L929 mouse fibroblasts. A common reason for this is a high level of glycolysis, to produce lactate, simultaneously with aerobic pathways. To test the idea that the calorimetric-respirometric (CR) ratio is a revealing cytotoxic endpoint, LS cells grown in serum-rich medium were insulted with known metabolic poisons. Malonate, 2,4-dinitrophenol (2,4-DNP) and a mixture of antimycin A and rotenone increased the CR ratio to degrees largely explained by greater lactate flux, the CR700 values being 22μM malonate, 56μM 2,4-DNP and, for the mixture, 2μM antimycin A and 5μM rotenone. Higher concentrations of 2,4-DNP gave an “exothermic gap” for which there was no explained pathway. Iodoacetate decreased the CR ratio while inhibiting glycolysis, a result which can be explained by the hypothesis that substrates available in the serum were degraded by mitochondrial pathways and thereby substituted for the normal input from the Krebs cycle, which had been arrested by pyruvate starvation. In a balanced salt solution containing only 5.5mM glucose, the metabolic rate slowed and the CR ratio was more exothermic (CR700 = 6μM), giving a “gap” for which there was no explanation. Ten MEIC chemicals gave CR700 endpoints which closely corresponded to the order of toxicity for a battery of tests using animal cells. The CR method thus provides a good basis for investigating the mechanisms by which chemicals have toxic effects on cells.

scholarly journals The fate of Si and Fe while nuclear glass alters with steel and clay

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
C. Carriere ◽  
P. Dillmann ◽  
S. Gin ◽  
D. Neff ◽  
L. Gentaz ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Protective Layer ◽  
Glass Dissolution ◽  
A Value ◽  
Waste Forms ◽  
Controlling Mechanism ◽  
Geological Repository ◽  
The Mean ◽  
High Level ◽  
Initial Dissolution Rate

AbstractThe French concept developed to dispose high-level radioactive waste in geological repository relies on glassy waste forms, isolated from the claystone host rock by steel containers. Understanding interactions between glass and surrounding materials is key for assessing the performance of a such system. Here, isotopically tagged SON68 glass, steel and claystone were studied through an integrated mockup conducted at 50 °C for 2.5 years. Post-mortem analyses were performed from nanometric to millimetric scales using TEM, STXM, ToF-SIMS and SEM techniques. The glass alteration layer consisted of a crystallized Fe-rich smectite mineral, close to nontronite, supporting a dissolution/reprecipitation controlling mechanism for glass alteration. The mean glass dissolution rate ranged between 1.6 × 10−2 g m−2 d−1 to 3.0 × 10−2 g m−2 d−1, a value only 3–5 times lower than the initial dissolution rate. Thermodynamic calculations highlighted a competition between nontronite and protective gel, explaining why in the present conditions the formation of a protective layer is prevented.

Toward high-level theoretical studies on the reaction kinetics of PAHs growth based on HACA pathway: An ONIOM[G3(MP2,CC)//B3LYP:DFT] method developed

Fuel ◽  
2021 ◽  
Vol 301 ◽  
pp. 121052
Author(s):  
Chengcheng Ao ◽  
Shanshan Ruan ◽  
Wei He ◽  
Yi Liu ◽  
Chenliang He ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Theoretical Studies ◽  
High Level ◽  
Kinetics Of

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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