Source-Term Constraints for the Proposed Repository at Yucca Mountain, Nevaida, Derived from the Natural Analog at PeÑa Blanca, Mexico

1991 ◽  
Vol 257 ◽  
Author(s):  
William M. Murphy ◽  
English C. Pearcy
Keyword(s):  
Nuclear Waste ◽  
Source Term ◽  
Yucca Mountain ◽  
Performance Assessments ◽  
Nuclear Waste Repository ◽  
Advective Transport ◽  
Silicate Minerals ◽  
Natural Analog ◽  
Rate Limiting ◽  
Nuclear Waste Forms

ABSTRACTThe source term for nuclear waste repository performance assessments can be constrained by the solubilities of radioelement-bearing solids and/or the rates of release of radioelements from nuclear waste forms. Both solubility and rate limits for the proposed repository at Yucca Mountain, Nevada, can be assessed using information from the natural analog at PeÑa Blanca, Mexico. Petrographic and field relations indicate that uraninite oxidation and transformation to secondary uranyl silicate minerals have been rapid relative to mass transport of uranium out of the PeÑa Blanca system. The rate limiting process for uranium removal is likely to be advective transport in groundwaters with uranium contents controlled by interactions with uranyl silicate minerals such as uranophane. A maximum limit on the rate of uraninite oxidation at PeÑa Blanca is calculated to be 0.032 tons of UO2 per year using geologic constraints on the amount of oxidation and the available time.

A Quantitative Risk Assessment Perspective on the Source Term for the Proposed Nuclear Waste Repository at Yucca Mountain

2009 ◽  
Vol 1193 ◽  
Author(s):  
William M. Murphy ◽  
B. John Garrick ◽  
Bruce E. Kirstein
Keyword(s):  
Risk Assessment ◽  
Nuclear Waste ◽  
Source Term ◽  
Initial Conditions ◽  
Yucca Mountain ◽  
Quantitative Risk Assessment ◽  
Nuclear Waste Repository ◽  
Event Tree ◽  
Geologic Repository ◽  
Isolation System

AbstractA quantitative risk assessment methodology is outlined for the source term for the proposed geologic repository for high-level nuclear waste at Yucca Mountain, Nevada. The methodology involves construction of a logical event tree to identify scenarios for the success or failure of the waste isolation system. Uncertainties in the intervening events between initial conditions and consequences can be quantified using probability distributions for steps along each scenario path. Likelihood is quantified according to the frequencies for each split fraction in the event tree. The result is a calculated probability of frequency curve for the release rate(s) of the modeled radionuclide(s).

Vegetation-Derived Insights on the Mobilization and Potential:Transport of Radionuclides from the Nopal I Natural Analog Site, Mexico

1999 ◽  
Vol 556 ◽  
Author(s):  
Bret W. Leslie ◽  
David A. Pickett ◽  
English C. Pearcy
Keyword(s):  
Source Term ◽  
Activity Ratio ◽  
Decay Chain ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Natural Analog ◽  
Ore Body ◽  
Term Model ◽  
High Level ◽  
Source Term Model

AbstractThe Nopal I uranium (U) deposit, Peñia Blanca, Mexico is a source term and contaminant transport natural analog to the proposed high-level nuclear waste repository at Yucca Mountain, Nevada. In an attempt to characterize the mobilization and potential transport of adionuclides in the unsaturated zone at the Nopal I deposit, vegetation growing on ore piles was analyzed for 238U, 235U, and 232Th decay-series isotopes. Specimens of Phacelia robusta growing on highgrade piles of U ore were collected and analyzed by alpha autoradiography, and by alpha and gamma spectrometry. Activities for U, thorium (Th), and radium (Ra) isotopes (Bq/kg dried plant) were 300, 1000, and 7000 for 238U, 230Th, and 226Ra, respectively. The 226Ra activities in these specimens are among the highest ever measured for plants; furthermore, the plant-to-soil 226Ra concentration ratio is higher than expected. These results demonstrate the large mobility and bio-availability of Ra in the Nopal I environment, and support previous indications of recent loss of 226Ra from the ore body. Comparison between the activities of 238U and 232Th decay-chain Th isotopes in the plants and in the ore substrate indicate that relative mobilization into pore solutions of 228Th > 230Th > 232Th, in a ratio of about 50 – 25:4:1, respectively. The similarity of the plant's 234U/238U activity ratio (˜1.2) to that of a caliche deposit that formed adjacent to the Nopal ore body around 54 ka suggests the 234U/238U activity ratio of U released from the ore is approximately 1.2. The U and 236Ra isotope activities of the plants and ore substrate, and solubility considerations, are used to assess a source term model of the potential Yucca Mountain repository. These results suggest the use of a natural analog source term model in performance assessments may be non-conservative.

Oxidative Alteration of Uraninite at the Nopal I Deposit, Mexico: Possible Contaminant Transport and Source Term Constraints for the Proposed Repository at Yucca Mountain

1992 ◽  
Vol 294 ◽  
Author(s):  
Bret W. Leslie ◽  
English C. Pearcy ◽  
James D. Prikryl
Keyword(s):  
Contaminant Transport ◽  
Source Term ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Fracture Density ◽  
Secular Equilibrium ◽  
Natural Analog ◽  
Decay Series ◽  
High Level Nuclear Waste ◽  
High Level

ABSTRACTThe Nopal I uranium deposit at Pefla Blanca, Mexico is being studied as a natural analog of the proposed high-level nuclear waste repository at Yucca Mountain. Identification of secondary uranium phases at Nopal I, and the sequence of their formation after uraninite oxidation, provides insight into the source term for uranium, and suggests that uranophane may control uranium release and transport in a silicic, tuffaceous, chemically oxidizing, and hydrologically unsaturated environment. Possible constraints on contaminant transport at Nopal I are derived from the spatial distribution of uranium and from measurements of 238U decay-series isotopes. The analyses indicate that flow of U-bearing fluids was influenced strongly by fracture density, but that the flow of these fluids was not restricted to fractures. Gamma spectroscopic measurements of 238U decay-series isotopes indicate secular equilibrium, which suggests undetectable U transport under present conditions.

Mechanisms for the Formation of a Perched Water Zone in Fractured Tuff: a Natural Analogue Study

1996 ◽  
Vol 465 ◽  
Author(s):  
E. G. Woodhouse ◽  
R. L. Bassett
Keyword(s):  
Structural Features ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Arid Environments ◽  
Perched Water ◽  
Natural Analog ◽  
Welded Tuff ◽  
Geochemical Properties ◽  
Water Zone ◽  
Mountain Site

ABSTRACTPerched water zones have been identified in the fractured, welded tuff in the semi-arid to arid environments of Yucca Mountain, Nevada and near Superior, Arizona. An understanding of the formation of such zones is necessary in order to predict where future perched water might form at Yucca Mountain, the proposed site of a high-level nuclear waste repository. The formation or growth of a perched zone near a repository is one of the factors to be considered in the risk assessment of the Yucca Mountain site.The Apache Leap Research Site near Superior, Arizona is a natural analog to the Yucca Mountain site in terms of geology, hydrology, and climate. Information used to study possible mechanisms for the formation of the perched zone included data regarding isotopie and geochemical properties of the waters in and above the perched water zone; measured hydrologie parameters of the perched zone; geophysical and measured parameters of the tuff; megascopic and microscopic observations of the tuff, including mineralogical, alteration, and structural features; and the lateral and vertical extent of perched water in the region.Aquifer test, geophysical, geochemical, and radioisotopic data show that fractures are the means by which water is recharging the perched zone. The reduced hydraulic conductivity of the formation in the perched zone appears to result from both a severe reduction in matrix porosity and permeability caused by welding, devitrification, and vapor phase crystallization; and by an increase in fracture filling which restricts the pathways for flow.

Experimental Investigation of Hydrous Pyrolysis of Diesel Fuel and the Effect of Pyrolysis Products on Performance of the Candidate Nuclear Waste Repository at Yucca Mountain

1993 ◽  
Vol 333 ◽  
Author(s):  
Kenneth J. Jackson ◽  
Susan A. Carroll
Keyword(s):  
Experimental Investigation ◽  
Nuclear Waste ◽  
Diesel Fuel ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Hydrothermal Solutions ◽  
Pyrolysis Products ◽  
Analytical Technique ◽  
Hydrous Pyrolysis ◽  
Waste Repository

It is thought that a significant amount of diesel fuel and other hydrocarbon-rich phases may remain inside the candidate nuclear waste repository at Yucca Mountain after construction and subsequent emplacement of radioactive waste. Although the proposed repository horizon is above the water table, the remnant hydrocarbon phases may react with hydrothermal solutions generated by high temperature conditions that will prevail for a period of time in the repository. The preliminary experimental results of this study show that diesel fuel hydrous pyrolysis is minimal at 200°C and 70 bars. The composition of the diesel fuel remained constant throughout the experiment and the concentration of carboxylic acids in the aqueous phases was only slightly above the detection limit (1–2 ppm) of the analytical technique.

scholarly journals Thermohydeologic Behavior at the Potential Yucca Mountain Nuclear Waste Repository

2000 ◽  
Author(s):  
T A Buscheck ◽  
N D Rosenburg ◽  
J Gansemer ◽  
Y Sun
Keyword(s):  
Nuclear Waste ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Waste Repository

NNWSI Performance Assessment Considerations

1983 ◽  
Vol 26 ◽  
Author(s):  
L. D. Tyler ◽  
R. R. Peters ◽  
N. K. Hayden ◽  
J. K. Johnstone ◽  
S. Sinnock
Keyword(s):  
Performance Assessment ◽  
Nuclear Waste ◽  
Yucca Mountain ◽  
Department Of Energy ◽  
Nuclear Waste Repository ◽  
Nuclear Waste Storage ◽  
Human Environment ◽  
Assessment Task ◽  
Waste Storage ◽  
A Site

ABSTRACTThe Nevada Nuclear Waste Storage Investigations (NNWSI) project includes a Performance Assessment task to evaluate the containment and isolation potential for a nuclear waste repository at Yucca Mountain in southern Nevada. This task includes calculations of the rates and concentrations at which radionuclides might be released and transported from the repository and will predict their consequences if they enter the human environment. Among the major tasks required for these calculations will be the development of models for water flow and nuclide transport under unsaturated conditions and in fractured hard rock. The program must also quantify the uncertainties associated with the results of the calculations. The performance assessment will provide evaluations needed for making major decisions as the U. S. Department of Energy seeks a site for a repository. An evaluation will be part of the environmental assessments prepared to accompany the potential nomination of the site. If the Yucca mountain site is selected for characterization and development as a repository, the assessments will be required for an environmental impact statement, a safety analysis report, and other documents.This program has been divided into five tasks. Collectively they will provide the performance assessments needed for the NNWSI Project.

Yucca mountain nuclear waste repository takes next step - [News]

IEEE Spectrum ◽  
2002 ◽  
Vol 39 (2) ◽  
pp. 28-28
Author(s):  
David P. Amber ◽  
Willie D. Jones
Keyword(s):  
Nuclear Waste ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Waste Repository
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