Adsorption of actinides within speleothems

2016 ◽  
Vol 80 (5) ◽  
pp. 765-780 ◽  
Author(s):  
P. Sengupta ◽  
J. Sanwal ◽  
N. L. Dudwadkar ◽  
S. C. Tripathi ◽  
P. M. Gandhi
Keyword(s):  
Valence State ◽  
Experimental Studies ◽  
Distribution Coefficients ◽  
Nuclear Wastes ◽  
Lesser Himalayas ◽  
Safety Assessments ◽  
High Level ◽  
Long Term Performance ◽  
Term Performance

AbstractStalagmites and stalactites, as observed within natural caves, may develop inside geological repositories during constructional and post-operational periods. It is therefore important to understand actinide sorption within such materials. Towards this, experimental studies were carried out with 233U, 238Np (VI), 238Np (IV), 239Pu and 241Am radiotracers using natural speleothem samples collected from the Dharamjali cave of the Kumaon Lesser Himalayas, India. Petrological/mineralogical studies showed that natural speleothems have three general domains: (1) columnar calcite; (2) microcrystalline calcite; and (3) botryoidal aragonite – each with ferruginous materials. Results showed that all domains of speleothems can take up >99% actinides, irrespective of valence state and pH (1–6 range) of the solution. However, distribution coefficients were found to be at a maximum in aragonite for most of the actinides. Such data are very important for long-term performance and safety assessments of the deep geological repositories planned for the disposal of high-level nuclear wastes.

scholarly journals Development of the Asphalt Multi-Integrated Roller Field and Experimental Studies

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Abd El Halim Omar Abd El Halim ◽  
Amir Omar Abd El Halim ◽  
Moustafa Awadalla ◽  
Mohamed Adel Hassanin
Keyword(s):  
Research Work ◽  
Experimental Studies ◽  
Geographic Location ◽  
Field Trials ◽  
Asphalt Pavements ◽  
Flat Plates ◽  
New Developments ◽  
Long Term Performance ◽  
Term Performance

Asphalt pavements have been compacted using steel drum rollers for a century. However, the problems that are observed today on these pavements are universal with no solution in sight. Intensive research work has been invested to identify the mechanisms that cause these problems. A recent development was the introduction of SuperPave mix design, GP asphalt cements, and the use of reinforcing elements ranging from polymer to steel bars. Yet it seems that none of these solutions have succeeded in eliminating any of the old problems. The pavements suffer from serious distresses regardless of the geographic location of the pavements and its design, materials, traffic loads, and climate condition. This paper presents a new approach to deal with the problems facing the asphalt pavements. While the research efforts to date concentrated on materials-related solutions, this paper identifies conventional compaction equipment as the cause of many problems observed on the pavements. The paper provides the development of the new Asphalt Multi-Integrated Roller, AMIR, and discusses new developments leading to a number of commercial field trials on several Ontario highways. The paper concludes that current compactors must be replaced with soft flat plates in order to achieve the required specifications for long term performance.

Doe Progress in Assessing the Long Term Performance of Waste Package Materials

1986 ◽  
Vol 84 ◽  
Author(s):  
A. Berusch ◽  
E. Gause
Keyword(s):  
Site Characterization ◽  
The United States ◽  
High Level Waste ◽  
Design Studies ◽  
Waste Package ◽  
License Application ◽  
High Level ◽  
Long Term Performance ◽  
Term Performance

Summary:Each of the projects has made significant progress toward the eventual operation of a repository for the disposal of high-level radioactive wastes in the United States. Although much has been accomplished, much remains to be done. For example, the Site Characterization Plans for BWIP and NNWSI are nearing completion to be followed by initiation of site characterization activities. The Site Characterization Plan for the selected salt site is scheduled for completion later in 1987. Waste package advanced conceptual design studies are currently scheduled to begin at each project before the end of FY 1987. These efforts will lead to selections of concepts to be detailed in the license application design phase. Compliance with the NRC criteria that require long-term waste package performance will be demonstrated by DOE by performing all of the aforementioned activities. In doing so, the DOE will also be assured that its plan for the safe disposal of high-level waste will be satisfactorily implemented.

Earnings Management and IPO Anomalies—Evidence from Indian Stock Market

2021 ◽  
pp. 227853372199471
Author(s):  
Aprajita Pandey ◽  
J. K. Pattanayak
Keyword(s):  
Earnings Management ◽  
Stock Returns ◽  
Initial Public Offering ◽  
Public Offering ◽  
High Level ◽  
Long Term Performance ◽  
Indian Stock Market ◽  
Term Performance ◽  
The Relationship

This study examines the relationship between the extent of earnings management in a firm, the level of underpricing during an initial public offering (IPO), and their long-term performance. Earnings management has been acknowledged as a matter of concern during IPOs since long; however, its relationship with underpricing and long-term returns remained inconclusive in emerging markets like India. Using a sample of Indian IPO firms, this study finds that firms that manage accruals aggressively in the pre-IPO period have high initial returns and subsequently low stock returns in the post-IPO period. This study also observed that firms that have used abnormal accruals more conservatively while reporting earnings have better returns in the third year after IPO compared to the firms that reported more aggressively. The results are in consonance with the theory of information asymmetry and suggest that valuation of an IPO firm becomes ambiguous with high level of earnings management, which leads to higher underpricing.

A Kinetic Model for the Stability of the Spent Fuel Matrix Under Oxic Conditions: Model Development Against Experimental Evidence

1996 ◽  
Vol 465 ◽  
Author(s):  
Jordi Bruno ◽  
E. Cera ◽  
L. Duro ◽  
T. E. Eriksen ◽  
P. Sellin ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Closed System ◽  
Model Development ◽  
Experimental Studies ◽  
Experimental Information ◽  
Spent Fuel ◽  
The Stability ◽  
Long Term Performance ◽  
Term Performance

ABSTRACTA kinetic model recently developed [1] for the radiolytically induced oxidative dissolution of the spent fuel matrix is presented. This is based on experimental studies on the generation and evolution of radiolytic products in a closed system containing fragments of PWR-fuel [2]. The outcome of this model is currently being integrated in the present PA exercise being prepared by SKB. The calibration of the model against various experimental information and its predictive capabilities for the long term performance of the spent fuel matrix are presented.

scholarly journals Preliminary Performance Assessment for Deep Borehole Disposal of High-Level Radioactive Waste

2012 ◽  
Vol 1475 ◽  
Author(s):  
Peter N. Swift ◽  
Bill W. Arnold ◽  
Patrick V. Brady ◽  
Geoff Freeze ◽  
Teklu Hadgu ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Performance Assessment ◽  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
High Level Radioactive Waste ◽  
Deep Boreholes ◽  
High Level ◽  
Long Term Performance ◽  
Term Performance

ABSTRACTDeep boreholes have been proposed for many decades as an option for permanent disposal of high-level radioactive waste and spent nuclear fuel. Disposal concepts are straightforward, and generally call for drilling boreholes to a depth of four to five kilometers (or more) into crystalline basement rocks. Waste is placed in the lower portion of the hole, and the upper several kilometers of the hole are sealed to provide effective isolation from the biosphere. The potential for excellent long-term performance has been recognized in many previous studies. This paper reports updated results of what is believed to be the first quantitative analysis of releases from a hypothetical disposal borehole repository using the same performance assessment methodology applied to mined geologic repositories for high-level radioactive waste. Analyses begin with a preliminary consideration of a comprehensive list of potentially relevant features, events, and processes (FEPs) and the identification of those FEPs that appear to be most likely to affect long-term performance in deep boreholes. The release pathway selected for preliminary performance assessment modeling is thermally-driven flow and radionuclide transport upwards from the emplacement zone through the borehole seals or the surrounding annulus of disturbed rock. Estimated radionuclide releases from deep borehole disposal of spent nuclear fuel, and the annual radiation doses to hypothetical future humans associated with those releases, are extremely small, indicating that deep boreholes may be a viable alternative to mined repositories for disposal of both high-level radioactive waste and spent nuclear fuel.

Solubility constraints on uranium concentrations in groundwaters of the Tono uranium deposit, Japan

2004 ◽  
Vol 92 (9-11) ◽  
Author(s):  
T. Iwatsuki ◽  
R. Arthur ◽  
K. Ota ◽  
R. Metcalfe
Keyword(s):  
Uranium Deposit ◽  
Thermodynamic Evaluation ◽  
Nuclear Wastes ◽  
Hydrous Oxide ◽  
Geological Disposal ◽  
Long Term Stability ◽  
Safety Assessments ◽  
High Level ◽  
Gifu Prefecture

SummaryA key concept underpinning most safety assessments of geological disposal systems for high-level nuclear wastes is that the maximum aqueous concentrations of actinide elements released from the waste will be limited by the solubility of the corresponding tetravalent oxide or hydrous oxide. The validity of this concept for U is evaluated in the present study using hydrochemical and mineralogical data from the Tono uranium (U) deposit in Gifu Prefecture, Japan. In addition, the long-term stability of U mineralization in the Tono deposit is assessed in terms of plausible range of U solubilities in paleogroundwaters migrating through the deposit.A thermodynamic evaluation of the aqueous-speciation and solubility behaviour of U indicates that U concentrations in the coexisting groundwaters greatly exceed the solubility of both uraninite [UO

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