scholarly journals Localized Dryout: an Approach for Managing the Thermal-Hydrological Effects of Decay Heat at Yucca Mountain

1995 ◽  
Vol 412 ◽  
Author(s):  
Thomas A. Buscheck ◽  
John J. Nitao ◽  
Lawrence D. Ramspot
Keyword(s):  
Relative Humidity ◽  
Thermal Load ◽  
Large Scale ◽  
Thermal Loading ◽  
Yucca Mountain ◽  
Large Temperature ◽  
Nuclear Waste Repository ◽  
Waste Package ◽  
Decay Heat ◽  
Hydrological Effects

AbstractFor a nuclear waste repository in the unsaturated zone at Yucca Mountain, there are two thermal loading approaches to using decay heat constructively-that is, to substantially reduce relative humidity and liquid flow near waste packages for a considerable time, and thereby limit waste package degradation and radionuclide dissolution and release. “Extended dryout” achieves these effects with a thermal load high enough to generate large-scale (coalesced) rock dryout. “Localized dryout”(which uses wide drift spacing and a thermal load too low for coalesced dryout) achieves them by maintaining a large temperature difference between the waste package and drift wail; this is done with close waste package spacing (generating a high line-heat load) and/or low-thermal-conductivity backfill in the drift. Backfill can greatly reduce relative humidity on the waste package in both the localized and extended dryout approaches. Besides using decay heat constructively, localized dryout reduces the possibility that far-field temperature rise and condensate buildup above the drifts might adversely affect waste isolation.

scholarly journals The Importance of Thermal Loading Conditions to Waste Package Performance at Yucca Mountain

1994 ◽  
Vol 353 ◽  
Author(s):  
Thomas A. Buscheck ◽  
John J. Nitao
Keyword(s):  
Relative Humidity ◽  
Thermal Load ◽  
Thermal Loading ◽  
Yucca Mountain ◽  
Thermal Loads ◽  
Ambient Conditions ◽  
Factors Affecting ◽  
Waste Package ◽  
Load Distributions ◽  
Wide Range

AbstractTemperature and relative humidity are primary environmental factors affecting waste package corrosion rates for the potential repository in the unsaturated zone at Yucca Mountain, Nevada. Under ambient conditions, the repository environment is quite humid. If relative humidity is low enough (<70%), corrosion will be minimal. Under humid conditions, corrosion is reduced if the temperature is low (<60°C). Using the V-TOUGH code, we model thermo-hydrological flow to investigate the effect of repository heat on temperature and relative humidity in the repository for a wide range of thermal loads. These calculations indicate that repository heat may substantially reduce relative humidity on the waste package, over hundreds of years for low thermal loads and over tens of thousands of years for high thermal loads. Temperatures associated with a given relative humidity decrease with increasing thermal load. Thermal load distributions can be optimized to yield a more uniform reduction in relative humidity during the boiling period.

Estimated Effects of Temperature-Relative Humidity Variations on the Composition of In-Drift Water in the Potential Nuclear Waste Repository at Yucca Mountain, Nevada

2004 ◽  
Vol 824 ◽  
Author(s):  
Lauren Browning ◽  
Randall Fedors ◽  
Lietai Yang ◽  
Osvaldo Pensado ◽  
Roberto Pabalan ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Nuclear Waste ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Aqueous Corrosion ◽  
Waste Package ◽  
Waste Repository ◽  
Effects Of Temperature ◽  
Drift Conditions ◽  
Simulated Time

AbstractWe define four distinct thermohydrochemical environments for drip shield and waste package corrosion in the potential nuclear waste repository, referred to here as the Dry, Seepage + Evaporation, Seepage + Condensation + Evaporation, and the Seepage + Condensation environments. These environments are bounded by temperature and relative humidity conditions at drift wall and drip shield/waste package surfaces judged most likely to initiate fundamental changes in the quantity and/or chemistry of in-drift waters. The duration in which different environments might exist is evaluated by comparing simulated, time-dependent temperature and relative humidity curves for three different locations within repository drift 25. In-drift conditions and processes postulated to cause drip shield/waste package corrosion are evaluated within the context of the thermohydrochemical environments by various means, including analytical calculations and geochemical simulations. Of the four environments considered here, the Seepage + Evaporation environment presents the most significant potential for aqueous corrosion of drip shield and waste package materials, and may persist for approximately 500 years in center drift locations. The likelihood for corrosion in other thermohydrochemical environments is significantly lower, but may increase with the acquisition of new data or the demonstration of extenuating circumstances.

Impact of Thermal Loading on Waste Package Material Performance

1994 ◽  
Vol 353 ◽  
Author(s):  
D. Stahl ◽  
J. K. McCoy ◽  
R. D. McCright
Keyword(s):  
Thermal Load ◽  
Thermal Loading ◽  
Steel Corrosion ◽  
Yucca Mountain ◽  
Microbiologically Influenced Corrosion ◽  
Corrosion Performance ◽  
Kinetic Relation ◽  
Reference Case ◽  
Time Exponent ◽  
High Thermal Load

AbstractThis report focuses on the prediction of materials performance for the carbon steel corrosion-allowance container as a function of thermal loading for the potential repository at Yucca Mountain. Low, intermediate and high thermal loads were evaluated as to their performance given assumptions regarding the temperature and humidity changes with time and the resultant depth of corrosion penetration. The reference case involved a kinetic relation for corrosion that was utilized in a sensitivity analysis to examine the impacts of time exponent, pitting, and microbiologically-influenced corrosion. As a result of this study, the high thermal load appears to offer the best corrosion performance. However, other factors must be considered in making the final thermal loading decision.

scholarly journals Studies of Altered Vitrophyre for the Prediction of Nuclear waste Repository-Induced Thermal Alteration at Yucca Mountain, Nevada

1983 ◽  
Vol 26 ◽  
Author(s):  
Schon S. Levy
Keyword(s):  
Nuclear Waste ◽  
Thermal Loading ◽  
Adsorbed Water ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Thermal Alteration ◽  
Secondary Porosity ◽  
Hydrous Minerals ◽  
Waste Repository ◽  
A Minor

ABSTRACTNuclear waste emplacement in devitrified volcanic tuff at Yucca Mountain will raise the temperature of surrounding rock for a geologically significant period of time. This study evaluates the susceptibility of an underlying 50 ft-thick vitrophyre to thermal alteration by examining alteration that occurred in the rock as it cooled after deposition. A 10°C temperature rise should have no mineralogical effects on the vitrophyre, but an increase of 60° or more is likely to result in alteration. Expected mineralogic changes in the vitrophyre caused by this amount of thermal loading include crystallization of zeolites and smectite. Alteration will be concentrated in a thin interval near the top of the vitrophyre and along fractures. Adsorbed water and water in preexisting hydrous minerals and in glass may contribute to hydrothermal alteration of underlying vitrophyre. Bulk porosity change would be slight and local porosity increase would probably be restricted to the upper part of the vitrophyre. Although some fracture filling could occur, such a minor sealing effect would be balanced by development of secondary porosity. Zeolites and smectite, newly-crystallized along fluid flow paths below the waste repository, could provide an enhanced sorptive barrier to radionuclide migration.

scholarly journals Waste Package Corrosion Studies Using Small Mockup Experiments

2008 ◽  
Vol 1107 ◽  
Author(s):  
B.E. Anderson ◽  
K.B. Helean ◽  
C.R. Bryan ◽  
P.V. Brady ◽  
R.C. Ewing
Keyword(s):  
Spent Nuclear Fuel ◽  
Sodium Metasilicate ◽  
Yucca Mountain ◽  
Corrosion Products ◽  
Nuclear Waste Repository ◽  
Low Oxygen ◽  
Waste Package ◽  
Reducing Conditions ◽  
Key Issues ◽  
Term Performance

AbstractUnderstanding the corrosion of spent nuclear fuel (SNF) and the subsequent mobilization of released radionuclides, particularly under oxidizing conditions, is one of the key issues in evaluating the long-term performance of a nuclear waste repository. However, the large amounts of iron in the metal waste package may create locally reducing conditions that would lower corrosion rates for the SNF, as well as reduce the solubility of some key radionuclides, e.g., Tc and Np. In order to investigate the interactions among SNF-waste package-fluids, four smallscale (∼1:40 by length) waste package mockups were constructed using metals similar to those proposed for use in waste packages at the proposed repository at Yucca Mountain. Each mockup experiment differed with respect to water input, exposure to the atmosphere, and temperature. Simulated Yucca Mountain process water (YMPW) was injected into three of the mockups at a rate of 200 μL per day for five days a week using a calibrated needle syringe. The YMPW was prepared by equilibrating 50 mg/L silica as sodium metasilicate with air, and adding enough HCl to lower the pH to 7.6 in contact with an excess of powdered calcite.X-ray powder diffraction and scanning electron microscopy confirm that, where corrosion occurred, the dominant corrosion product in all cases was magnetite. In the high temperature (60°C) experiment, hematite and a fibrous, Fe-O-Cl phase were also identified. The Fe(II)/Fe(III) ratios measured in the corrosion products using a wet chemistry technique indicate extremely low oxygen fugacities (10-36 bar). Experiments are in progress in which 0.1g powdered UO2 was included in the mock-up in order to investigate the relative kinetics of Fe and U oxidation and to identify the U corrosion products formed under these conditions.

scholarly journals A Quantitative Assessment of Microbiological Contributions to Corrosion of Candidate Nuclear Waste Package Materials

1999 ◽  
Vol 556 ◽  
Author(s):  
T. Lian ◽  
S. Martin ◽  
J. Horn ◽  
D. Jones
Keyword(s):  
Corrosion Rate ◽  
Nuclear Waste ◽  
Fold Increase ◽  
Yucca Mountain ◽  
Department Of Energy ◽  
Microbiologically Influenced Corrosion ◽  
304 Stainless Steel ◽  
Detection Methods ◽  
Nuclear Waste Repository ◽  
Waste Package

AbstractThe U.S. Department of Energy is contributing to the design of a potential nuclear waste repository at Yucca Mountain, Nevada. A system to predict the contribution of Yucca Mountain (YM) bacteria to overall corrosion rates of candidate waste package (WP) materials was designed and implemented. DC linear polarization resistance techniques were applied to candidate material coupons that had been inoculated with a mixture of YM-derived bacteria with potentially corrosive activities, or left sterile. Inoculated bacteria caused a 5- to 6-fold increase in corrosion rate of carbon steel C 1020 (to approximately 7-8μm/yr), and an almost 100-fold increase in corrosion rate of Alloy 400 (to approximately μm/yr) was observed due to microbiological activities. Microbiologically Influenced Corrosion (MIC) rates on more resistant materials (CRMs: Alloy 625, Type 304 Stainless Steel, and Alloy C22) were on the order of hundredths of micrometers per year (μm/yr). Bulk chemical and surfacial endpoint analyses of spent media and coupon surfaces showed preferential dissolution of nickel from Alloy 400 coupons and depletion of chromium from CRMs after incubation with YM bacteria. Scanning electron microscopy also showed greater damage to the Alloy 400 surface than that indicated by electrochemical detection methods.

Waste Package Environment for the Yucca Mountain Site Characterization Project

2002 ◽  
Vol 713 ◽  
Author(s):  
G.E. Gdowski ◽  
T.J. Wolery ◽  
N.D. Rosenberg
Keyword(s):  
Relative Humidity ◽  
Aqueous Solutions ◽  
Redox State ◽  
Environmental Parameters ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Relative Humidity Range ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Humidity Range

ABSTRACTEnvironmental parameters that would affect the degradation of engineered materials, including waste packages and drip shields, in the potential high level nuclear waste repository at Yucca Mountain, Nevada are being characterized as part of the Yucca Mountain Project. These parameters include: temperature, relative humidity, range of water chemistry, deliquescence of salts, pH, and electrochemical potential (Eh). The likelihood of various brine compositions forming on the engineered components under repository conditions, and the implications, is discussed. Relative humidity controls the ionic strength and composition of the aqueous solutions, and hence strongly influences the corrosion processes that could occur. Studies are underway to more fully characterize the redox state of aqueous solutions in contact with engineered system components.

Deliquescence Behavior of Multicomponent Salts: Effects on the Drip Shield and Waste Package Chemical Environment of the Proposed Nuclear Waste Repository at Yucca Mountain, Nevada

2002 ◽  
Vol 713 ◽  
Author(s):  
Roberto T. Pabalan ◽  
Lietai Yang ◽  
Lauren Browning
Keyword(s):  
Chloride Concentration ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Aqueous Corrosion ◽  
Calcium Salts ◽  
Accelerated Corrosion ◽  
Waste Package ◽  
Low Concentrations ◽  
Salt Mixtures ◽  
High Chloride Concentration

ABSTRACTThermodynamic calculations were conducted to determine the deliquescence behavior of salt mixtures and to simulate the evaporation of Yucca Mountain groundwaters. The results are consistent with published experimental data that show the deliquescence points of salt mixtures are lower than that of individual salts. For mixtures of NaCl and KCl salts, the deliquescence point of pure NaNO3 salt is an appropriate lower bound. However, mixtures containing magnesium and calcium salts have much lower deliquescence points than pure NaNO3. If magnesium and calcium salts are deposited on waste package and drip shield surfaces, it could lead to earlier initiation of aqueous corrosion than assumed by the DOE in its performance assessment abstractions. Such salt mixtures can be formed by evaporation of waters with compositions similar to some Yucca Mountain porewaters and would be characterized by low deliquescence relative humidity, high chloride concentration, and low concentrations of anions such as free (uncomplexed) nitrate and sulfate that could mitigate against the chloride-enhanced corrosion of the waste package. Evaporation of Yucca Mountain groundwaters also could lead to fluoride concentrations that are above the threshold for accelerated corrosion of the titanium drip shield.

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