Download or read book Subsurface Transport of Radionuclides at the Nevada Test Site written by Margaret Ann Guell and published by . This book was released on 1997 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Underground nuclear detonations at the Nevada Test Site (NTS) provide a unique opportunity to study the behavior of radionuclides in a field environment. The 1965 Cambric event, a small detonation in the saturated zone of the Valley Fill alluvial aquifer at NTS, has been studied extensively to improve the understanding of groundwater flow and radionuclide migration. The 1974 field investigation of the Cambric event included: (1) a re-entry boring into the original detonation cavity and (2) the installation of a pumping well 91 meters away from the cavity to draw mobile radionuclides such as tritium and krypton-85. This satellite well, sampled regularly over 16 years, produced some unexpected results. Because of the supposed ideality of tritium and krypton as tracers, their arrival was expected to be concurrent; however, krypton-85 arrival was delayed compared to tritium. More important is the fact that, while over 90% of the decay-corrected tritium from the original blast was drawn out through the well, less than half of the krypton was recovered. This work presents a hypothesis for understanding these unexpected results based on the site hydrogeology and underground detonation phenomenology. Carbon dioxide evolved from caliche during the detonation appears to have caused the upward migration of krypton-85 and other gaseous radionuclides through the collapsing chimney and into the unsaturated zone above. In the process, krypton became distributed throughout the cavity and chimney, while tritium remained immediately around the cavity. This post-detonation movement of krypton-85 provides one explanation, then, of the unexpected elution curve results. To demonstrate the validity of this hypothesis, a variety of numerical simulations were performed using the finite difference code TRACR3D. Calibrating two unknown hydraulic conductivity parameters on the tritium field data, it was shown that krypton-85 may indeed have been distributed throughout the chimney as suggested by the hypothesis."--Abstract.
Download or read book 1979 80 written by and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Phase II Transport Model of Corrective Action Unit 98 written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This document, the Phase II Frenchman Flat transport report, presents the results of radionuclide transport simulations that incorporate groundwater radionuclide transport model statistical and structural uncertainty, and lead to forecasts of the contaminant boundary (CB) for a set of representative models from an ensemble of possible models. This work, as described in the Federal Facility Agreement and Consent Order (FFACO) Underground Test Area (UGTA) strategy (FFACO, 1996; amended 2010), forms an essential part of the technical basis for subsequent negotiation of the compliance boundary of the Frenchman Flat corrective action unit (CAU) by Nevada Division of Environmental Protection (NDEP) and National Nuclear Security Administration Nevada Site Office (NNSA/NSO). Underground nuclear testing via deep vertical shafts was conducted at the Nevada Test Site (NTS) from 1951 until 1992. The Frenchman Flat area, the subject of this report, was used for seven years, with 10 underground nuclear tests being conducted. The U.S. Department of Energy (DOE), NNSA/NSO initiated the UGTA Project to assess and evaluate the effects of underground nuclear tests on groundwater at the NTS and vicinity through the FFACO (1996, amended 2010). The processes that will be used to complete UGTA corrective actions are described in the "Corrective Action Strategy" in the FFACO Appendix VI, Revision No. 2 (February 20, 2008).
Download or read book Exposure Assessment of Groundwater Transport of Tritium from the Central Nevada Test Area written by Karl F. Pohlmann and published by . This book was released on 1995 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: This exposure assessment provides a range of possible human health risk at two locations due to groundwater transport from the Faultless underground nuclear test. These locations correspond to the boundary of the land under DOE control (where no wells currently exist) and the closest existing well (Six Mile Well). The range in excess risk is within the EPA goal for excess risk due to environmental contaminants (10−6) at Six Mile Well. Calculations considering high spatial variability in hydraulic properties and/or high uncertainty in the mean groundwater velocity are also within the EPA goal. At the DOE boundary, the range in excess risk exceeds the EPA goal, regardless of the values of spatial variability and uncertainty. The range in values of excess risk can be reduced with additional field data from the site; however, incorporation of additional data, which would likely be obtained at great expense, is unlikely to result in significant refinement of the results.
Download or read book Assessment of Hydrologic Transport of Radionuclides from the Rulison Underground Nuclear Test Site Colorado written by Sam Earman and published by . This book was released on 1996 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Serendipitous Long Term Infiltration Experiment written by and published by . This book was released on 2008 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: Underground nuclear weapons testing at the Nevada Test Site introduced numerous radionuclides that may be used to characterize subsurface hydrologic transport processes in arid climates. A sixteen year pumping experiment designed to examine radionuclide migration away from the CAMBRIC nuclear test, conducted in groundwater beneath Frenchman Flat in 1965, gave rise to an unintended second experiment involving radionuclide infiltration through the vadose zone, as induced by seepage of pumping effluents beneath an unlined discharge trench. The combined experiments have been reanalyzed using a detailed, three-dimensional numerical model of transient, variably saturated flow and mass transport, tailored specifically for large scale and efficient calculations. Simulations have been used to estimate radionuclide travel and residence times in various parts of the system for comparison with observations in wells. Model predictions of mass transport were able to clearly demonstrate radionuclide recycling behavior between the ditch and pumping well previously suggested by isotopic age dating information; match travel time estimates for radionuclides moving between the ditch, the water table, and monitoring wells; and provide more realistic ways in which to interpret the pumping well elution curves. Collectively, the results illustrate the utility of integrating detailed numerical modeling with diverse observational data in developing accurate interpretations and forecasts of contaminant migration processes.
Download or read book The LLNL Nevada Test Side Underground Radionuclide Source term Inventory written by and published by . This book was released on 1995 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The potential for the contamination of ground water beneath the Nevada Test Site (NTS) by nuclear testing has long been recognized. The United States has conducted underground nuclear weapons testing at NTS since 1957, and a considerable amount of radioactive material has been deposited in the subsurface by this work. As a part of the U.S. Department of Energy Nevada Operations Office's Underground Test Area Operable Unit (UGTA OP), the Lawrence Livermore National Laboratory (LLNL) has compiled an inventory of radionuclides produced by underground LLNL weapons tests from 1957 through 1992. It is well known that some groundwater at NTS has been contaminated by radionuclides from weapons testing. Nearly one-third of the nuclear tests were conducted near or beneath the pre-test static water level (SWL). An important responsibility of the UGTA OP is to assess the migration potential of contaminants beneath the NTS and surrounding lands. Except for tritium (3H), which is capable of migration with water as molecular HTO, the ability of radionuclides to migrate significant distances from their source is presently thought to be very low. However, before this potential for migration can be fully assessed, the quantity of existing contaminants must be carefully estimated. The inventory of the radionuclide source term provides an upper limit on the availability of radionuclides for migration. However, an accurate assessment of risk to the public depends on more than an inventory of radionuclides remaining from underground testing. An estimate of the hydrologic source term consisting of radionuclides dissolved in or transported by ground water must compliment the radionuclide source term.
Download or read book Unclassified Source Term and Radionuclide Data for Corrective Action Unit 98 written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Frenchman Flat is one of several areas of the Nevada Test Site (NTS) used for underground nuclear testing (Figure 1-1). These nuclear tests resulted in groundwater contamination in the vicinity of the underground test areas. As a result, the U.S. Department of Energy (DOE), National Nuclear Security Administration Nevada Site Office (NNSA/NSO) is currently conducting a corrective action investigation (CAI) of the Frenchman Flat underground test areas. Since 1996, the Nevada Division of Environmental Protection (NDEP) has regulated NNSA/NSO corrective actions through the ''Federal Facility Agreement and Consent Order'' ([FFACO], 1996). Appendix VI of the FFACO agreement, ''Corrective Action Strategy'', was revised on December 7, 2000, and describes the processes that will be used to complete corrective actions, including those in the Underground Test Area (UGTA) Project. The individual locations covered by the agreement are known as corrective action sites (CASs), which are grouped into corrective action units (CAUs). The UGTA CASs are grouped geographically into five CAUs: Frenchman Flat, Central Pahute Mesa, Western Pahute Mesa, Yucca Flat/Climax Mine, and Rainier Mesa/Shoshone Mountain (Figure 1-1). These CAUs have distinctly different contaminant source, geologic, and hydrogeologic characteristics related to their location (FFACO, 1996). The Frenchman Flat CAU consists of 10 CASs located in the northern part of Area 5 and the southern part of Area 11 (Figure 1-1). This report documents the evaluation of the information and data available on the unclassified source term and radionuclide contamination for Frenchman Flat, CAU 98. The methodology used to estimate hydrologic source terms (HSTs) for the Frenchman Flat CAU is also documented. The HST of an underground nuclear test is the portion of the total inventory of radionuclides that is released over time into the groundwater following the test. The total residual inventory of radionuclides associated with one or more tests is known as the radiologic source term (RST). The RST is comprised of radionuclides in water, glass, or other phases or mineralogic forms. This evaluation was conducted in support of the development of a CAU contaminant transport model for the Frenchman Flat CAU.
Download or read book Radionuclide Mobility at the Nevada Test Site written by D. Smith and published by . This book was released on 2003 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: Underground nuclear tests conducted at the Nevada Test Site (NTS) are characterized by abundant fission product and actinide source terms. Included are {sup 99}Tc and other soluble radionuclides ({sup 3}H, {sup 14}C, {sup 36}Cl, {sup 85}Kr, and {sup 129}I), which are presumably mobile in groundwater and potentially toxic to down-gradient receptors. NTS provides the Office of Civilian Radioactive Waste Management (OCRWM) with an analog of the release of these radionuclides from a nuclear waste repository in the absence of engineered barriers. The investigation described in this report synthesizes a substantial body of data collected on the identity and distribution of soluble radionuclides at field scales over distances of hundreds of meters, for durations up to 40 years, and under hydrogeologic conditions very similar to the proposed geological repository at Yucca Mountain. This body of data is complemented by laboratory transport studies and a synthesis of recent modeling investigations from the NTS, with an emphasis on the ongoing Yucca Mountain Program (YMP) efforts. Overall, understanding the controls of radionuclide mobility associated with these nuclear tests will provide insight into the repository's future performance as well as bounds and calibrations for the numerical predictions of long-term radionuclide releases and migration.
Download or read book Contaminant Boundary at the Faultless Underground Nuclear Test written by and published by . This book was released on 2003 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: The U.S. Department of Energy (DOE) and the Nevada Division of Environmental Protection (NDEP) have reached agreement on a corrective action strategy applicable to address the extent and potential impact of radionuclide contamination of groundwater at underground nuclear test locations. This strategy is described in detail in the Federal Facility Agreement and Consent Order (FFACO, 2000). As part of the corrective action strategy, the nuclear detonations that occurred underground were identified as geographically distinct corrective action units (CAUs). The strategic objective for each CAU is to estimate over a 1,000-yr time period, with uncertainty quantified, the three-dimensional extent of groundwater contamination that would be considered unsafe for domestic and municipal use. Two types of boundaries (contaminant and compliance) are discussed in the FFACO that will map the three-dimensional extent of radionuclide contamination. The contaminant boundary will identify the region wi th 95 percent certainty that contaminants do not exist above a threshold value. It will be prepared by the DOE and presented to NDEP. The compliance boundary will be produced as a result of negotiation between the DOE and NDEP, and can be coincident with, or differ from, the contaminant boundary. Two different thresholds are considered for the contaminant boundary. One is based on the enforceable National Primary Drinking Water Regulations for radionuclides, which were developed as a requirement of the Safe Drinking Water Act. The other is a risk-based threshold considering applicable lifetime excess cancer-risk-based criteria The contaminant boundary for the Faultless underground nuclear test at the Central Nevada Test Area (CNTA) is calculated using a newly developed groundwater flow and radionuclide transport model that incorporates aspects of both the original three-dimensional model (Pohlmann et al., 1999) and the two-dimensional model developed for the Faultless data decision analysis (DDA) (Pohll and Mihevc, 2000). This new model includes the uncertainty in the three-dimensional spatial distribution of lithology and hydraulic conductivity from the 1999 model as well as the uncertainty in the other flow and transport parameters from the 2000 DDA model. Additionally, the new model focuses on a much smaller region than was included in the earlier models, that is, the subsurface within the UC-1 land withdrawal area where the 1999 model predicted radionuclide transport will occur over the next 1,000 years. The purpose of this unclassified document is to present the modifications to the CNTA groundwater flow and transport model, to present the methodology used to calculate contaminant boundaries, and to present the Safe Drinking Water Act and risk-derived contaminant boundaries for the Faultless underground nuclear test CAU.
Download or read book Assessment of Hydrologic Transport of Radionuclides from the Gasbuggy Underground Nuclear Test Site New Mexico written by and published by . This book was released on 1996 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: The U.S. Department of Energy (DOE) is operating an environmental restoration program to characterize, remediate, and close non-Nevada Test Site locations that were used for nuclear testing. Evaluation of radionuclide transport by groundwater from these sites is an important part of the preliminary risk analysis. These evaluations are undertaken to allow prioritization of the test areas in terms of risk, provide a quantitative basis for discussions with regulators and the public about future work at the sites, and provide a framework for assessing data needs to be filled by site characterization. The Gasbuggy site in northwestern New Mexico was the location of an underground detonation of a 29-kiloton nuclear device in 1967. The test took place in the Lewis Shale, approximately 182 m below the Ojo Alamo Sandstone, which is the aquifer closest to the detonation horizon. The conservative assumption was made that tritium was injected from the blast-created cavity into the Ojo Alamo Sandstone by the force of the explosion, via fractures created by the shot. Model results suggest that if radionuclides produced by the shot entered the Ojo Alamo, they are most likely contained within the area currently administered by DOE. The transport calculations are most sensitive to changes in the mean groundwater velocity, followed by the variance in hydraulic conductivity, the correlation scale of hydraulic conductivity, the transverse hydrodynamic dispersion coefficient, and uncertainty in the source size. This modeling was performed to investigate how the uncertainty in various physical parameters affects calculations of radionuclide transport at the Gasbuggy site, and to serve as a starting point for discussion regarding further investigation at the site; it was not intended to be a definitive simulation of migration pathways or radionuclide concentration values.
Download or read book Uncertainties Associated with the Definition of a Hydrologic Source Term for the Nevada Test Site written by and published by . This book was released on 1995 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: The U.S. Department of Energy, Nevada Operations Office (DOE/NV) Environmental Restoration Division is seeking to evaluate groundwater contamination resulting from 30 years of underground nuclear testing at the Nevada Test Site (NTS). This evaluation requires knowledge about what radioactive materials are in the groundwater and how they are transported through the underground environment. This information coupled with models of groundwater flow (flow paths and flow rates) will enable predictions of the arrival of each radionuclide at a selected receptor site. Risk assessment models will then be used to calculate the expected environmental and human doses. The accuracy of our predictions depends on the validity of our hydrologic and risk assessment models and on the quality of the data for radionuclide concentrations in ground water at each underground nuclear test site. This paper summarizes what we currently know about radioactive material in NTS groundwater and suggests how we can best use our limited knowledge to proceed with initial modeling efforts. The amount of a radionuclide available for transport in groundwater at the site of an underground nuclear test is called the hydrologic source term. The radiologic source term is the total amount of residual radionuclides remaining after an underground nuclear test. The hydrologic source term is smaller than the radiologic source term because some or most of the radionuclide residual cannot be transported by groundwater. The radiologic source term has been determined for each of the underground nuclear tests fired at the NTS; however, the hydrologic source term has been estimated from measurements at only a few sites.
Download or read book Histoire e de la p dagogie du l7e si cle nos jours written by and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Assessing Field scale Migration of Mobile Radionuclides at the Nevada Test Site written by and published by . This book was released on 2006 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerous long-lived radionuclides, including 99Tc (technetium) and 129I (iodine), are present in groundwater at the Nevada Test Site (NTS) as a result of 828 underground nuclear weapons tests conducted between 1951 and 1992. We synthesize a body of groundwater data collected on the distribution of a number of radionuclides (3H, 14C, 36Cl, 99Tc and 129I), which are presumably mobile in the subsurface and potentially toxic to down-gradient receptors, to assess their migration at NTS, at field scales over distances of hundreds of meters and for durations of more than thirty years. Qualitative evaluation of field-scale migration of these radionuclides in the saturated zone provides an independent approach to validating their presumably conservative transport in the performance assessment of the proposed geological repository at Yucca Mountain, which is located on the western edge of NTS. The analyses show that the interaction of 3H with a solid surface via an isotopic exchange with clay lattice hydroxyls may cause a slight delay in the transport of 3H. The transport of 14C could be retarded by its isotopic exchange with carbonate minerals, and the exchange may be more pronounced in the alluvial aquifer. In particular, 99Tc may not necessarily exist as a mobile and conservative species 99TcO4−, as commonly assumed for NTS groundwater. This is corroborated with recent in situ redox potential measurements, both across and near Yucca Mountain, showing that groundwater at multiple locations is not oxidizing. Speciation of iodine and its associated reactivity and mobility is also complex in the groundwater at the NTS and deserves further attention. The assumption of no retardation for the transport of 99Tc (especially) and 129I, used at the performance assessment of Yucca Mountain repository, is probably overly conservative and results in unrealistically high estimated doses for down-gradient receptors.
Download or read book Evaluation of the Radiochemistry of Near Field Water Samples at the Nevada Test Site Applied to the Definition of a Hydrologic Source Term written by and published by . This book was released on 2002 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: Effective management of available groundwater resources and strategies for remediation of water impacted by past nuclear testing practices depend on knowledge about the migration of radionuclides in groundwater away from the sites of the explosions. A primary concern is to assess the relative mobilities of the different radionuclide species found near sites of underground nuclear tests and to determine the concentration, extent, and speed of this movement. Ultimately the long term transport behavior of radionuclides with half-lives long enough that they will persist for decades, their interaction with groundwater, and the resulting flux of these contaminants is of paramount importance. As part of a comprehensive approach to these assessments, more than three decades of site-specific sites studies have been undertaken at the Nevada Test Site (NTS) which have focused on the means responsible for the observed or suspected movement of radionuclides away from underground nuclear tests (RNM, 1983). More recently regional and local models of groundwater flow and radionuclide transport have been developed as part of a federal and state of Nevada program to assess the long-term effects of underground nuclear testing on human health and environment (e.g., U.S. DOE/NV, 1997a; Tompson et al., 1999; Pawloski et al., 2001). Necessary to these efforts is a reliable measure of the hydrologic source term which is defined as those radionuclides dissolved in or otherwise transported by groundwater (Smith et al., 1995). Measurement of radionuclides in waters sampled near the sites of underground nuclear test provides arguably the best opportunity to bound the hydrologic source term. This empirical approach was recognized early and concentration data has been collected annually since mid-1970's. Initially three sites were studied at the NTS; over the years the program has been expanded to include more than fifteen study locations. As part of various field programs, Lawrence Livermore National Laboratory and Los Alamos National Laboratory have annually returned water samples from wells in near-field locations at the NTS for radiochemical analyses. This report makes the distinction between samples taken in the near-field and the far field. The near-field includes the area extending radially (almost equal to)300 meters from surface ground zero (the firing point of an underground nuclear test projected upwards on ground surface). Over the years this sampling program has also been refereed to as the ''hot-well monitoring program'' because these water samples contained concentrations of tritium above natural background (tritium concentrations in southern Nevada precipitation are 0.5 to 2.0 Bq/L, Farmer et al., 1998). A majority of the hot wells contain tritium in excess of the 741 Bq/L (20,000 pCi/L) drinking water standard (Smith et al., 1996a; Smith et al., 1997). The sites which comprise our current hot well sampling network are plotted on a map of the NTS in Figure 1.
Download or read book Nevada Test Site NTS and Off site Locations in the State of Nevada Tonopah Test Range Portions of the Nellis AFB Range NAFR Complex the Central Nevada Test Area and Shoal Area Nye County written by and published by . This book was released on 1996 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Laboratory and Field Studies Related to Radionuclide Migration at the Nevada Test Site in Support of the Underground Test Area and Hydrologic Resources Management Projects written by and published by . This book was released on 2002 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report details the work of Chemistry Division personnel from Los Alamos National Laboratory in FY 2001 for the U.S. Department of Energy National Nuclear Security Administration Nevada Operations Office (NNSA/NV) under its Defense Programs and Environmental Restoration divisions. Los Alamos is one of a number of agencies collaborating in an effort to describe the present and future movement of radionuclides in the underground environment of the Nevada Test Site. This fiscal year we collected and analyzed water samples from a number of expended test locations at the Nevada Test Site. We give the results of these analyses and summarize the information gained over the quarter century that we have been studying several of these sites. We find that by far most of the radioactive residues from a nuclear test are contained in the melt glass in the cavity. Those radionuclides that are mobile in water can be transported if the groundwater is moving due to hydraulic or thermal gradients. The extent to which they move is a function of their chemical speciation, with neutral or anionic materials traveling freely relative to cationic materials that tend to sorb on rock surfaces. However, radionuclides sorbed on colloids may be transported if the colloids are moving. Local conditions strongly influence the distribution and movement of radionuclides, and we continue to study sites such as Almendro, which is thermally quite hot, and Nash and Bourbon, where radionuclides had not been measured for 8 years. We collected samples from three characterization wells in Frenchman Flat to obtain baseline radiochemistry data for each well, and we analyzed eight wells containing radioactivity for 237Np, using our highly sensitive ICP/MS. We have again used our field probe that allows us to measure important groundwater properties in situ. We conclude our report by noting document reviews and publications produced in support of this program.
