Download or read book 2 Page Summary for Neptunium Solubility in the Near field Environment of A Proposed Yucca Mountain Repository written by and published by . This book was released on 2005 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt: The total system performance assessment (TSPA) for the proposed repository at Yucca Mountain, NV, includes a wide variety of processes to evaluate the potential release of radionuclides from the Engineered Barrier System into the unsaturated zone of the geosphere. The principal processes controlling radionuclide release and mobilization from the waste forms are captured in the model to assess the dissolved concentrations of radionuclides in the source-term. The TSPA model of the source-term incorporates the far-from-equilibrium dissolution of, for example, spent nuclear fuel (SNF) to capture bounding rates of radionuclide availability as the SNF degrades. In addition, for individual radionuclides, the source-term model evaluates solubility constraints that are more indicative of longer-term, equilibrium processes that can limit the potential mass transport from the source term in those cases. These solubility limits represent phase saturation and precipitation processes that can occur either at the waste form as it alters, or at other locations in the near-field environment (e.g., within the invert) if chemical conditions are different. Identification and selection of applicable constraints for solubility-limited radionuclide concentrations is a primary focus in formulating the source-term model for the TSPA. Neptunium is a long-lived radionuclide that becomes a larger fraction of the potential dose as radioactive decay of other radionuclides proceeds. To delineate appropriate long-term source-term controls on dissolved neptunium concentrations, a number of alternative models have been defined. The models are based on data both collected within the Yucca Mountain Project and taken from published literature, and have been evaluated against independent data sets to assess their applicability. The alternative models encompass ones based on precipitation of neptunium within its own separate oxide phases (i.e., ''pure'' Np-phases), and those where neptunium is incorporated into the secondary (tertiary, quaternary, etc.) uranyl phases forming as alteration products of SNF (secondary phases). The constraints on dissolved neptunium concentrations from ''pure'' Np-phase models provide more elevated bounds compared to the values derived from models of trace incorporation of Np into secondary uranyl phases. Such secondary phase models depend on a larger set of processes and variables compared to more idealized solubility models for Np-oxides, and therefore, secondary phase models generally will have more complex bases to define adequately the expected behavior.
Download or read book Neptunium Solubility in the Near Field Environment of A Proposed Yucca Mountain Repository written by D. C. Sassani and published by . This book was released on 2004 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt: For representing the source-term of a proposed repository at Yucca Mountain, NV, total system performance assessment models evaluate the disequilibrium degradation of the waste forms to capture a bounding rate for radionuclide source-term availability and use solubility constraints that are more representative of longer-term, equilibrium processes to limit radionuclide mass transport from the source-term. These solubility limits capture precipitation processes occurring either as the waste forms alter, or in the near-field environment as chemical conditions evolve. A number of alternative models for solubility controls on dissolved neptunium concentrations have been evaluated. These include idealized models based on precipitation of neptunium as separate oxide minerals and more complex considerations of trace amounts of neptunium being incorporated into the secondary uranyl phases from waste form alteration. Thermodynamic models for neptunium under oxidizing conditions indicate that tetravalent neptunium (NpO{sub 2}) solids are more stable relative to pentavalent (Np{sub 2}O{sub 5}) phases, and thereby set lower dissolved concentrations of neptunyl species. Data on solids and solutions from slow flow through (dripping) tests on spent fuel grains indicate that neptunium is tetravalent in the spent fuel and that over {approx}9 years the neptunium concentrations are near to or below calculated NpO{sub 2} solubility. The possibility of kinetic rate limitations to NpO{sub 2} precipitation has led to temperature-dependent studies of NpO{sub 2} precipitation kinetics and solubility to reduce uncertainties and confirm application of the model.
Download or read book Measured Solubilities and Speciations of Neptunium Plutonium and Americium in a Typical Groundwater J 13 from the Yucca Mountain Region Milestone Report 3010 WBS 1 2 3 4 1 3 1 written by Heino Nitsche and published by . This book was released on 1993 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Viability Assessment of a Repository at Yucca Mountain Total system performance assessment written by and published by . This book was released on 1998 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transport of Neptunium Through Yucca Mountain Tuffs written by and published by . This book was released on 1993 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neptunium has a high solubility in groundwaters from Yucca Mountain [1]. Uranium in nuclear reactors produces 237Np which has a half-life of 2.1 4 x 106 years. Consequently, the transport of 237Np through tuffs is of major importance in assessing the performance of a high-level nuclear waste repository at Yucca Mountain. The objective of this work is to determine the amount of Np retardation that is provided by the minerals in Yucca Mountain tuffs as a function of groundwater chemistry.
Download or read book Measured Solubilities and Speciations of Neptunium Plutonium and Americium in a Typical Groundwater J 13 from the Yucca Mountain Region Milestone Report 3010 WBS 1 2 3 4 1 3 1 written by and published by . This book was released on 1993 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solubility and speciation data are important in understanding aqueous radionuclide transport through the geosphere. They define the source term for transport retardation processes such as sorption and colloid formation. Solubility and speciation data are useful in verifying the validity of geochemical codes that are part of predictive transport models. Results are presented from solubility and speciation experiments of 237NpO2, 239Pu{sup 4+}, 241Am{sup 3+}/Nd{sup 3+}, and 243Am{sup 3+} in J-13 groundwater (from the Yucca Mountain region, Nevada, which is being investigated as a potential high-level nuclear waste disposal site) at three different temperatures (25°, 60°, and 90°C) and pH values (5.9, 7.0, and 8.5). The solubility-controlling steady-state solids were identified and the speciation and/or oxidation states present in the supernatant solutions were determined. The neptunium solubility decreased with increasing temperature and pH. Plutonium concentrations decreased with increasing temperature and showed no trend with pH. The americium solutions showed no clear solubility trend with increasing temperature and increasing pH.
Download or read book Existing Evidence for the Fate of Neptunium in the Yucca Mountain Repository written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Neptunium, because of its long half life, is an element of long-term interest to the Yucca Mountain repository. The fate of neptunium under repository settings is unknown. This report provides a review and new interpretation of past tests on commercial spent nuclear fuel and experimental evidence on the fate of neptunium. Tests on commercial spent nuclear fuel preformed previously at Pacific Northwest National Laboratory (PNNL) used a bathtub setup by immersing spent fuel in either deionized water or a groundwater typical of those at Yucca Mountain. The main goal of the tests was to determine the different concentrations of radionuclides in solution with different types of cladding defects. Neptunium was not the focus of these tests, nor were the tests designed to study neptunium. Drip tests performed at Argonne National Laboratory (ANL) are unsaturated tests that drip water at different rates on spent fuel. Relatively new tests at ANL examine the corrosion of Np-doped U3O8 in humid air at various temperatures. This review concludes that all tests reported here have analytical problems (i.e., relatively high detection limits for Np) and have been configured such that they limit the ability to interpret the available neptunium data. Past tests on spent nuclear fuel do not unambiguously describe neptunium chemistry as there are multiple mechanisms that may explain the observed behavior in each test. One apparently major shortcoming of most tests is that the extent of fuel reaction was limited by the amount of oxygen present in the system. Further detailed studies under repository-relevant conditions, which include the assumption of a constant 20 percent oxygen atmosphere, are needed to provide the data necessary for the development and validation of models used to predict the long-term fate of neptunium and other radionuclides at Yucca Mountain.
Download or read book Solubility Enhanced Retardation of Neptunium in the Unsaturated Zone at Yucca Mountain written by G. Lu and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measured Solubilities and Speciations from Oversaturation Experiments of Neptunium Plutonium and Americium in UE 25p No 1 Well Water from the Yucca Mountain Region written by and published by . This book was released on 1994 with total page 103 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solubility and speciation are important in understanding aqueous radionuclide transport through the geosphere. They define the source term for transport retardation processes such as sorption and colloid formation. Solubility and speciation data are useful in verifying the validity of geochemical codes that are a part of predictive transport models. Results are presented from solubility and speciation experiments of 237NpO2, 239Pu{sup 4+}, and 241Am{sup 3+}/Nd{sup 3+} in a modified UE-25p No. 1 groundwater (from the Yucca Mountain region, Nevada, which is being investigated as a potential high-level nuclear waste disposal site) at two different temperatures (25° and 60°C) and three pH values (6.0, 7.0, 8.5). The solubility-controlling steady-state solids were identified and the speciation and/or oxidation states present in the supernatant solutions were determined. The neptunium solubility decreased with increasing temperature and pH. Plutonium concentrations significantly decreased with increasing temperature at pH 6 and 7. The concentration at pH 8.5 hardly decreased at all with increasing temperature. At both temperatures the concentrations were highest at pH 8.5, lowest at pH 7, and in between at pH 6. For the americium/neodymium solutions, the solubility decreased significantly with increasing temperature and increased somewhat with increasing pH.
Download or read book Batch Sorption Results for Neptunium Transport Through Yucca Mountain Tuffs written by Ines R. Triay and published by . This book was released on 1996 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: We studied the sorption of neptunium onto tuffs characteristic of the proposed nuclear waste repository at Yucca Mountain, Nevada. The neptunium was in the Np(V) oxidation state under oxidizing conditions in groundwaters from two wells located close to the repository site (J-13 and UE-25 p No. 1). We used devitrified, vitric, zeolitic (with emphasis on clinoptilolite-rich samples), and calcite-rich tuffs characteristic of the geology of the site. Neptunium sorbed well onto calcite and calcite-rich tuffs, indicating that a significant amount of neptunium retardation can be expected under fractured-flow scenarios because of calcite coating of the fractures. Neptunium sorption onto clinoptilolite-rich zeolitic tuffs in J-13 well water (pH from 7 to 8.5) was moderate, increased with decreasing pH, and correlated to surface area and amount of clinoptilolite. Neptunium sorbed poorly onto zeolitic tuffs from UE-25 p No. 1 groundwater (pH from 7 to 9) and onto devitrified and vitric tuffs from J-13 and UE-25 p No. 1 waters (pH from 7 to 9). Iron oxides appeared to be passivated in tuffs, not seeming to contribute to the observed neptunium sorption, even though neptunium sorption onto synthetic iron oxide is significant.
Download or read book Near Field Repository Behavior of Neptunium written by Marc Andre Vial and published by . This book was released on 2002 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Batch Sorption Results for Neptunium Transport Through Yucca Mountain Tuffs Yucca Mountain Site Characterization Program Milestone 3349 written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We studied the sorption of neptunium onto tuffs characteristic of the proposed nuclear waste repository at Yucca Mountain, Nevada. The neptunium was in the Np(V) oxidation state under oxidizing conditions in groundwaters from two wells located close to the repository site (J-13 and UE-25 p No. 1). We used devitrified, vitric, zeolitic (with emphasis on clinoptilolite-rich samples), and calcite-rich tuffs characteristic of the geology of the site. Neptunium sorbed well onto calcite and calcite-rich tuffs, indicating that a significant amount of neptunium retardation can be expected under fractured-flow scenarios because of calcite coating of the fractures. Neptunium sorption onto clinoptilolite-rich zeolitic tuffs in J-13 well water (pH from 7 to 8.5) was moderate, increased with decreasing pH, and correlated to surface area and amount of clinoptilolite. Neptunium sorbed poorly onto zeolitic tuffs from UE-25 p No. 1 groundwater (pH from 7 to 9) and onto devitrified and vitric tuffs from J-13 and UE-25 p No. 1 waters (pH from 7 to 9). Iron oxides appeared to be passivated in tuffs, not seeming to contribute to the observed neptunium sorption, even though neptunium sorption onto synthetic iron oxide is significant.
Download or read book Solubility and Speciation Results from Oversaturation Experiments on Neptunium Plutonium and Americium in a Neutral Electrolyte with a Total Carbonate Similar to Water from Yucca Mountain Region Well UE 25p 1 written by and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Preparation of Neptunium 237 Metal written by A. N. Morgan and published by . This book was released on 1962 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Los Alamos Science written by and published by . This book was released on 2000 with total page 522 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Structural Chemistry of Inorganic Actinide Compounds written by Sergey Krivovichev and published by Elsevier. This book was released on 2006-12-08 with total page 505 pages. Available in PDF, EPUB and Kindle. Book excerpt: Structural Chemistry of Inorganic Actinide Compounds is a collection of 13 reviews on structural and coordination chemistry of actinide compounds. Within the last decade, these compounds have attracted considerable attention because of their importance for radioactive waste management, catalysis, ion-exchange and absorption applications, etc. Synthetic and natural actinide compounds are also of great environmental concern as they form as a result of alteration of spent nuclear fuel and radioactive waste under Earth surface conditions, during burn-up of nuclear fuel in reactors, represent oxidation products of uranium miles and mine tailings, etc. The actinide compounds are also of considerable interest to material scientists due to the unique electronic properties of actinides that give rise to interesting physical properties controlled by the structural architecture of respective compounds. The book provides both general overview and review of recent developments in the field, including such emergent topics as nanomaterials and nanoparticles and their relevance to the transfer of actinides under environmental conditions. * Covers over 2,000 actinide compounds including materials, minerals and coordination polymers* Summarizes recent achievements in the field* Some chapters reveal (secret) advances made by the Soviet Union during the 'Cold war'
Download or read book Handbook of Radioactivity Analysis written by Michael F. L'Annunziata and published by Elsevier. This book was released on 2012-12-02 with total page 810 pages. Available in PDF, EPUB and Kindle. Book excerpt: Handbook of Radioactivity Analysis is written by experts in the measurement of radioactivity. The book describes the broad scope of analytical methods available and instructs the reader on how to select the proper technique. It is intended as a practical manual for research which requires the accurate measurement of radioactivity at all levels, from the low levels encountered in the environment to the high levels measured in radioisotope research. This book contains sample preparation procedures, recommendations on steps to follow, necessary calculations, computer controlled analysis, and high sample throughput techniques. Each chapter includes practical techniques for application to nuclear safety, nuclear safeguards, environmental analysis, weapons disarmament, and assays required for research in biomedicine and agriculture. The fundamentals of radioactivity properties, radionuclide decay, and methods of detection are included to provide the basis for a thorough understanding of the analytical procedures described in the book. Therefore, the Handbook can also be used as a teaching text. Includes sample preparation techniques for matrices such as soil, air, plant, water, animal tissue, and surface swipes Provides procedures and guidelines for the analysis of commonly encountered na
