scholarly journals Insights to Repository Performance through Study of a Nuclear Test Site

2000 ◽  
Vol 663 ◽  
Author(s):  
D.K. Smith ◽  
A.B. Kersting ◽  
J.L. Thompson ◽  
D.L. Finnegan
Keyword(s):  
Tectonic Setting ◽  
Test Site ◽  
Yucca Mountain ◽  
Nuclear Test ◽  
High Level Waste ◽  
Radionuclide Transport ◽  
Source Terms ◽  
Nevada Test Site ◽  
Waste Repository ◽  
High Level

ABSTRACTUnderground nuclear test sites offer an unprecedented opportunity to evaluate processes relevant to high-level waste repository performance in the absence of engineered barriers. Radionuclide migration programs at the Nevada Test Site represent a twenty-five year systematic investigation of the diverse radiologic source terms residual from weapons testing and the evolution of the hydrologic source term which comprises those radionuclides dissolved in or otherwise available for transport by groundwater. The Nevada Test Site shares actinide source terms, correlative geology, an identical tectonic setting, similar climate, and a thick unsaturated zone with the adjacent potential Yucca Mountain high-level waste repository and provides a natural laboratory to assess long-term radionuclide transport in the near field. Analog studies may ultimately help validate predictions of radionuclide transport from the potential Yucca Mountain repository.

Study of the Performance of Sealing Systems for Access Shafts in a High-Level Waste Repository

1992 ◽  
Vol 294 ◽  
Author(s):  
A. Saotome ◽  
K. Hara ◽  
J. Okamoto
Keyword(s):  
Host Rock ◽  
Ground Surface ◽  
Sensitivity Analyses ◽  
High Level Waste ◽  
Radionuclide Transport ◽  
Radionuclide Migration ◽  
Backfill Material ◽  
Disturbed Zone ◽  
Waste Repository ◽  
High Level

ABSTRACTShaft sealing in a high-level waste(HLW) disposal system functions to minimize the water flow passage, and retard the radionuclide transport from the repository to the accessible environment. It is important to estimate the radionuclide migration along the sealed shaft from the viewpoint of the design and the performance assessment of the sealing system.This study presents the results of sensitivity analyses on the radionuclide migration in the vicinity of the access shaft of a repository in order to evaluate the effects of the length of a plug, as well as the number of plugs, and curtain grouts.In this study, the upward hydraulic gradient of the groundwater flow along shafts was used, based on transient coupled thermo-hydraulic analyses around a repository. Hydraulic conductivities of the backfill material and the disturbed zones around the shaft tunnels were also assumed to be one order and two orders of magnitude higher than that of the host rock, respectively.The results show that the velocity of the groundwater within the shaft and the disturbed zone is reduced by a factor of one third by installing a few plugs into the shaft filled with backfill material. The curtain grouts have the effect of retarding the radionuclide migration from the repository to the ground surface at a factor of approximately five. A few plug installations have the same effect. The sealing system properly constituted with backfill, plugs, and grouts can provide the same performance as the original host rock.

scholarly journals Ion Exchange and Dehydration Effects on Potassium and Argon Contents of Clinoptilolite

1995 ◽  
Vol 412 ◽  
Author(s):  
G. Woldegabriel ◽  
S. Levy
Keyword(s):  
Unsaturated Zone ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Radionuclide Transport ◽  
Geochemical Processes ◽  
Saturated Zone ◽  
High Level Nuclear Waste ◽  
Waste Repository ◽  
Natural Clinoptilolite ◽  
High Level

AbstractZeolite-rich Miocene tuffs are an important part of the principal hydrochemical barrier to water-borne radionuclide transport from a potential high-level nuclear waste repository at Yucca Mountain, Nevada. The timing of zeolitization is an issue that relates to paleohydrology, permeability, zeolite stability, and unsaturated-zone geochemical processes. Exploratory K/Ar dating of clinoptilolite, the most abundant and widespread zeolite, shows a striking and consistent pattern of increasing apparent ages (2–13 Ma) with depth. Only the isotopic ages from the saturated zone are compatible with geologic evidence suggesting an age >10 Ma for most of the zeolites.Factors that may be responsible for the young apparent ages in the unsaturated zone were investigated. Cation exchange with recharge water and Ar diffusion under unsaturated conditions (processes that may be characteristic of the unsaturated zone) were evaluated experimentally for their effects on K/Ar systematics. Cation exchanging a natural clinoptilolite with Ca-, Cs-, K-, and Na-chloride solutions showed minimal effects on radiogenic Ar content. However, clinoptilolite heated at 2007deg;C for 16 hours in air lost a significant amount of its radiogenic Ar compared with minimal losses from clinoptilolite heated in water at 100°C for over 5 months. The preliminary results indicate that Ar loss from incompletely hydrated clinoptilolite may be a major factor contributing to the young apparent ages of clinoptilolite in the unsaturated zone at Yucca Mountain.

Numerical Simulation of Flow and Transport in Fractured Tuff

1983 ◽  
Vol 26 ◽  
Author(s):  
B. J. Travis ◽  
S. W. Hodson ◽  
H. E. Nuttall ◽  
T. L. Cook ◽  
R. S. Rundberg
Keyword(s):  
Numerical Simulation ◽  
Heat Flow ◽  
Radioactive Waste ◽  
Numerical Models ◽  
Test Site ◽  
Yucca Mountain ◽  
Nevada Test Site ◽  
Flow And Transport ◽  
Geologic Storage ◽  
High Level

ABSTRACTThe unsaturated, fractured tuff of Yucca Mountain in the Nevada Test Site is one of the potential sites for geologic storage of high-level radioactive waste. A modeling study of flow and transport in this geologically complex site is presented. Numerical models of mass and heat flow in conjunction with analytical solutions are being used for sensitivity and pathway analysis studies and to aid in design and interpretation of laboratory and field flow and transport tests in tuff.

scholarly journals The Hydrothermal Stability of Cement Sealing Materials in the Potential Yucca Mountain High Level Nuclear Waste Repository

1991 ◽  
Vol 245 ◽  
Author(s):  
J. L. Krumhansl ◽  
T. E. Hinkebein ◽  
J. Myers
Keyword(s):  
Geochemical Modeling ◽  
Test Site ◽  
Cementitious Materials ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
X Ray Diffraction ◽  
Nevada Test Site ◽  
Post Test ◽  
High Level ◽  
Modeling Code

ABSTRACTCementitious materials, together with other materials, are being considered to seal a potential repository at Yucca Mountain. A concern with cementitious materials is the chemical and mineralogic changes that may occur as these materials age while in contact with local ground waters. A combined theoretical and experimental approach was taken to determine the ability to theoretically predict mineralogic changes. The cementitious material selected for study has a relatively low Ca:Si ratio approaching that of the mineral tobermorite. Samples were treated hydrothermally at 200°C with water similar to that obtained from the J-13 well on the Nevada Test Site. Post-test solutions were analyzed for pH as well as dissolved K, Na, Ca, Al, and Si. Solid phases formed during these experiments were characterized by scanning electron microscopy and X-ray diffraction. These findings were compared with predictions made by the geochemical modeling code EQ3NR/EQ6. It was generally found that there was good agreement between predicted and experimental results.

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