The Long-Term Performance of Nuclear Waste Forms: Natural Materials - Three Case Studies

1992 ◽  
Vol 294 ◽  
Author(s):  
Rodney C. Ewing
Keyword(s):  
Case Studies ◽  
Nuclear Waste ◽  
Experimental Results ◽  
Waste Form ◽  
Short Term ◽  
Waste Forms ◽  
Long Term Performance ◽  
Term Performance ◽  
Nuclear Waste Forms

ABSTRACTNatural materials may be used to advantage in the evaluation of the long-term performance of nuclear waste forms. Three case studies are presented: (I) radiation effects in ceramic waste forms; (II) corrosion products of U02 under oxic conditions; (III) corrosion rate of nuclear waste glasses. For each case, a natural phase which is structurally and chemically analogous to the waste form is identified and used to evaluate the long-term behavior of a nuclear waste form. Short-term experimental results are compared to the observations made of analogous natural phases. The three case studies illustrate that results may range between providing fundamental data needed for the long-term evaluation of a waste form to only providing qualitative data of limited use. Although in the most rigorous view the long-term behaviour of a phase cannot be predicted, the correspondence between short-term experimental results and observations made of natural phases provides confidence in the “predicted” behavior of the waste form. The strength of this approach rests with the degree to which a mechanistic understanding of the phenomenon is attained.

The Role of Metal Ion Solubility in Leaching of Nuclear Waste Glasses

1981 ◽  
Vol 11 ◽  
Author(s):  
B. Grambow
Keyword(s):  
Nuclear Waste ◽  
Metal Ion ◽  
Short Term ◽  
Long Term Performance ◽  
Term Performance ◽  
Kinetics Of ◽  
Elemental Release ◽  
Nuclear Waste Forms

The leachability of solid nuclear waste forms has been studied by many investigators to evaluate the short-term kinetics of elemental release or to determine the effects of leachant composition or other system parameters. Some general observations from these studies have included: incongruent leaching; formation of reaction layers that contain rare-earth, alkaline-earth, or transition metal elements; and apparent saturation of some elements in solution while others continue to be leached. Before these observations can be used to predict long-term performance of waste glasses under repository conditions, the mechanisms controlling the release of elements from the solid must be understood.

scholarly journals Preparation and characterization of multiphase ceramic designer waste forms

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Braeden M. Clark ◽  
Priyatham Tumurugoti ◽  
Shanmugavelayutham K. Sundaram ◽  
Jake W. Amoroso ◽  
James C. Marra
Keyword(s):  
Fixed Ratio ◽  
Chemical Durability ◽  
Waste Form ◽  
Ceramic Waste ◽  
Waste Forms ◽  
Plasma Sintering ◽  
Long Term Performance ◽  
Term Performance ◽  
Elemental Release

AbstractThe long-term performance, or resistance to elemental release, is the defining characteristic of a nuclear waste form. In the case of multiphase ceramic waste forms, correlating the long-term performance of multiphase ceramic waste forms in the environment to accelerated chemical durability testing in the laboratory is non-trivial owing to their complex microstructures. The fabrication method, which in turn affects the microstructure, is further compounding when comparing multiphase ceramic waste forms. In this work, we propose a “designer waste form” prepared via spark plasma sintering to limit interaction between phases and grain growth during consolidation, leading to monolithic high-density waste forms, which can be used as reference materials for comparing the chemical durability of multiphase waste forms. Designer waste forms containing varying amounts of hollandite in the presence of zirconolite and pyrochlore in a fixed ratio were synthesized. The product consistency test (PCT) and vapor hydration test (VHT) were used to assess the leaching behavior. Samples were unaffected by the VHT after 1500 h. As measured by the PCT, the fractional Cs release decreased as the amount of hollandite increased. Elemental release from the zirconolite and pyrochlore phases did not appear to significantly contribute to the elemental release from the hollandite phase in the designer waste forms.

scholarly journals Post-Acquisition Performance of Emerging Market Firms: A Multi-Dimensional Analysis of Acquisitions in India

2021 ◽  
Vol 14 (12) ◽  
pp. 567
Author(s):  
Arindam Das
Keyword(s):  
Structural Equation ◽  
Emerging Market ◽  
Empirical Studies ◽  
Short Term ◽  
Firm Level ◽  
Acquisition Performance ◽  
Long Term Performance ◽  
Term Performance ◽  
A Performance

M&A performance is a multifaceted, compound construct with no overarching factor that captures all different dimensions. This paper examines the concept of acquisition performance and proposes a model that links firm-level factors and transaction parameters with firms’ short-term and long-term performance, extending to financial-, market- and innovation measures. Building on past empirical studies on the influence of various factors on M&A performance, a multi-dimensional structural equation model has been developed and it has been tested with a dataset on acquisitions in the Indian technology sector over a period of ten years. The results suggest that: (a) smaller acquirers with higher book value and leveraged firms demonstrate better long-term performance; (b) contrary to established understanding, short-term market returns are not influenced by deal parameters; (c) majority stake purchases show relatively lesser gains—suggesting the possible presence of post-acquisition integration issues and, (d) acquirers with high intangible assets continue to do well on innovation performance post-acquisition. By indicating situations and conditions under which an acquisition would potentially lead to a performance gain for the acquirer, these results provide significant insight to practitioners pursuing M&As for growth opportunities.

scholarly journals Does Corporate Charitable Giving Help Sustain Corporate Performance in China?

2019 ◽  
Vol 11 (5) ◽  
pp. 1491 ◽  
Author(s):  
Keling Wang ◽  
Yaqiong Miao ◽  
Ching-Hui Su ◽  
Ming-Hsiang Chen ◽  
Zhongjun Wu ◽  
...  
Keyword(s):  
Charitable Giving ◽  
Corporate Performance ◽  
Sales Growth ◽  
Short Term ◽  
Return On Equity ◽  
Long Term Performance ◽  
Term Performance ◽  
The Impact ◽  
Total Sales

We examined whether corporate charitable giving (CCG) in China benefits corporate performance (CP) in terms of sales growth (SG), return on asset (ROA), return on equity (ROE), and Tobin’s Q (TQ), and revealed several findings. First, testing shows variation in the impact of CCG on CP. Whereas the ratio of corporate charitable giving (RCCG) to total sales revenue does not significantly enhance SG, ROA, and ROE, it is positively related to TQ. Second, the positive relationship between RCCG and TQ originates from non-state-owned firms (NSOFs) rather than state-owned firms (SOFs). Third, Chinese firms may use CCG as traditional philanthropy to enhance long-term performance instead of strategically using it to generate short-term performance. Lastly, an inverted U-shaped relationship exists between RCCG and TQ, especially for NSOFs.

Ion Implantation Studies of Nuclear Waste Forms

1981 ◽  
Vol 6 ◽  
Author(s):  
Clyde J. M. Northrup ◽  
George W. Arnold ◽  
Thomas J. Headley
Keyword(s):  
Nuclear Waste ◽  
Borosilicate Glass ◽  
Alpha Decay ◽  
Lead Ions ◽  
Waste Form ◽  
Elastic Recoil ◽  
Elastic Recoil Detection ◽  
Waste Forms ◽  
Basic Studies ◽  
Nuclear Waste Forms

ABSTRACTThe first observations of physical and chemical changes induced by lead implantation damage and leaching are reported for two proposed U.S. nuclear waste forms (PNL 76–68 borosilicate glass and Sandia titanate ceramics) for commercial wastes. To simulate the effects of recoil nucleii due to alpha decay, the materials were implanted with lead ions at equivalent doses up to approximately 1 × 1019 a decays/cm3 . In the titanate waste form, the zirconolite, perovskite, hollandite, and rutile phases all exhibited a mottled appearance in the transmission electron microscope (TEM) typical of defect clusters in radiation damaged, crystalline solids. One titanate phase containing uranium was found by TEM to be amorphous after implantation at the highest dose. No enhanced leaching (deionized water, room temperature, 24 hours) of the irradiated titanate waste form, including the amorphous phase, was detected by TEM, but Rutherford backscattering (RBS) suggested a loss of cesium and calcium after 21 hours of leaching. The RBS spectra also indicated enhanced leaching from the PNL 76–68 borosilicate glass after implantation with lead ions, in general agreement with the observations of Dran, et al. [6,7] on other irradiated materials. Elastic recoil detection spectroscopy (ERD), used to profile hydrogen after leaching, showed penetration of the hydrogen to several thousand angstroms for both the implanted and unimplanted materials. These basic studies identified techniques to follow the changes that occur on implantation and leaching of complex amorphous and crystalline waste forms. These studies were not designed to produce comparisons between waste forms of gross leach rates.

scholarly journals Facile incorporation of technetium into magnetite, magnesioferrite, and hematite by formation of ferrous nitrate in situ: precursors to iron oxide nuclear waste forms

2018 ◽  
Vol 47 (30) ◽  
pp. 10229-10239 ◽  
Author(s):  
Wayne W. Lukens ◽  
Sarah A. Saslow
Keyword(s):  
Iron Oxide ◽  
Fission Product ◽  
Nuclear Waste ◽  
Half Life ◽  
Fission Yield ◽  
Waste Forms ◽  
Nuclear Waste Forms

The fission product, 99Tc, presents significant challenges to the long-term disposal of nuclear waste due to its long half-life, high fission yield, and to the environmental mobility of pertechnetate (TcO4−), the stable Tc species in aerobic environments.

scholarly journals The Evaluation of Short- and Long-Term Performance of Cold-Mix Asphalt Patching Materials

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Chien-Wei Huang ◽  
Tsung-Han Yang ◽  
Guan-Bo Lin
Keyword(s):  
Stability Result ◽  
Short Term ◽  
Curing Conditions ◽  
Initial Stability ◽  
Service Durability ◽  
Highly Correlated ◽  
Marshall Stability ◽  
Long Term Performance ◽  
Term Performance

Potholes, one of the major types of distress on pavement surfaces, damage vehicles and are a safety hazard for the travelling public. In order to mitigate the effect of potholes, cold-mix asphalt (CMA) patching materials are commonly used for urgent repair of pavement surfaces before resurfacing can be undertaken. Therefore, the short-term (initial stability) and long-term (in-service durability) performance evaluation of CMA patching materials is necessary. This study conducted several curing conditions in the laboratory to investigate short-term, long-term, and moisture effects on pavement surfaces. Moreover, this study compared the Marshall stability of samples prepared under various compaction conditions. Marshall stability, Cantabro abrasion, and UK wheel tracking tests were conducted to evaluate the performance of CMA patching materials. The results indicated that the Marshall stability of dense-gradation (DG) CMA patching materials was higher than that of open-graded (OG) CMA patching materials and the Marshall stability of OG CMA patching materials was highly influenced by the coarse aggregate proportion. The DG and OG CMA patching materials exhibited comparable abrasion resistance, and the Cantabro abrasion ratio was highly correlated to the estimated asphalt film thickness for the OG CMA patching materials. A moisture indicator (MI) was proposed, and the effect of moisture damage on Marshall stability and Cantabro abrasion ratio was related to the proposed MI. The rutting resistance of the DG CMA patching materials was higher than that of the OG CMA patching materials, which is consistent with the Marshall stability result.

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