14C and Other Radionuclides in Impermeable Graphite Material Waste form Long Term Behavior

ABSTRACTThe radiocarbon (14C) content of irradiated graphite is the most important problem for the management of Spanish irradiated graphite (Vandellós I NPP) as L&ILW, due to this material exceeding the maximum14C inventory for the C.A. El Cabril repository. Therefore, the encapsulation of graphite in an impermeable matrix and making an appropriate waste form are indicated as potential management options to be studied. The conversion of the graphite to a long-term stable glass matrix, called IGM (impermeable graphite matrix), uses a long-term stable inorganic binder which additionally encloses the graphite pore system. The world’s first IGM samples made with irradiated graphite have been manufactured in CIEMAT facilities. The durability of the matrix is investigated in leaching experiments in deionized water and granitic bentonite water. The results show that ∼0.05% of14C is leached. A species of organic carbon was found as formate and oxalate (∼10–1mg/L). CO was detected as volatile specie in both media in the first leaching steps; for deionized water (∼3.101mg/L) and in granitic bentonite water (ranging 1.101–3.101mg/L). These low values demonstrated the durability of the IGM glass matrix for final disposal.

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Comparison of 200 Liter and 40 Milliliter Leach Tests

MRS Proceedings ◽

10.1557/proc-15-243 ◽

1982 ◽

Vol 15 ◽

Author(s):

J. H. Westsik ◽

C. O. Harvey ◽

F. P. Roberts ◽

W. A. Ross ◽

R. E. Thornhill

Keyword(s):

Large Scale ◽

Deionized Water ◽

Waste Form ◽

Small Scale ◽

Matrix Elements ◽

Elemental Concentrations ◽

The Past ◽

Leach Test ◽

The Matrix ◽

Scale Test

ABSTRACTDuring the past year we have conducted a modified MCC-1 leach test on a 145 kg block of a cast cement waste form. The leach vessel was a 200 liter Teflon®-lined drum and contained 97.5 liters of deionized water. The results of this large-scale leach test were compared with the results of standard MCC-1 tests (40 ml) on smaller samples of the same waste form. The ratio of leachate volumes between the large and small scale tests was 2500 and the ratio of sample masses was 150,000. The cast cement samples for both tests contained plutonium-doped incinerator ash.The leachates from these tests were analyzed for both plutonium and the matrix elements. Evaluation of plutonium plateout in the large-scale test indicated that the majority of the plutonium leached from the samples deposits onto vessel walls and little (<3 × 10−12M) remains in solution. Comparison of elemental concentrations in the leachates indicates some differences up to 5X in the concentration in the large- and small-scale tests. The differences are attributed to differences in the solubilities of Ca, Si, and Fe at pH ˜11.5 and at pH ˜12.5. The higher pH observed for the large-scale test is a result of the larger quantities of sodium in the large block of cement.

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Mobilization/Retention of Radionuclides during Corrosion of High Burnup Spent Fuel and Backfill Materials in Salt Brines

MRS Proceedings ◽

10.1557/proc-757-ii8.2 ◽

2002 ◽

Vol 757 ◽

Cited By ~ 1

Author(s):

Andreas Loida ◽

Bernhard Kienzler ◽

Horst Geckeis

Keyword(s):

Near Field ◽

Waste Form ◽

Spent Fuel ◽

The Matrix ◽

Backfill Materials ◽

Salt Brine ◽

Solid Phases ◽

Long Term Behavior ◽

The Impact

ABSTRACTWith respect to the assessment of the long-term behavior of the waste form spent fuel it is of high importance to study the fuel alteration in contact with groundwater and near field materials. The aim of this work is to evaluate the impact of candidate backfill materials hydroxylapatite and magnetite on the overall corrosion behavior of this waste form in salt brine; both materials are used in corrosion tests together with spent fuel. The instant releases and the matrix dissolution rates appear to be similar in presence and in absence of any backfill material under study. However, Am,Np,Pu,U and Sr are retained at different ratios on the hydroxylapatite, on the magnetite and on the fuel sample, indicating possibly the formation of different radionuclide containing new solid phases.

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Long-Term Radioactivity Release From Solidified High-Level Waste -Part I: An Approach To Evaluating Experimental Data

MRS Proceedings ◽

10.1557/proc-11-45 ◽

1981 ◽

Vol 11 ◽

Author(s):

Friedrich K. Altenhein ◽

Werner Lutze ◽

Rodney C. Ewing

Keyword(s):

Source Term ◽

Elevated Temperatures ◽

Relative Sensitivity ◽

Reaction Rates ◽

Waste Form ◽

High Level Waste ◽

Leach Rate ◽

Leaching Experiments ◽

High Level

Safety and risk analyses for the isolation of radioactive waste in a repository must begin with a source term to quantify the amount of radioactivity released from the waste form under a specific set of conditions. The interaction of the waste form with aqueous solutions is the most important mechanism to consider, as any material released may be dissolved and reach the biosphere. In this regard the behaviour of heat generating high-level waste is of particular importance, because reaction rates are higher at elevated temperatures. A long-term leach rate was derived from previous and continuing experimental work. The purpose of this paper is not to describe the “real case” release but rather to provide guidelines for the design of leaching experiments and determine the required precision for the data. This can be derived from the relative sensitivity of extrapolated leach rates for various parameters measured in laboratory experiments.

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Study of Natural Minerals of U-Ryrochlore-Type Structure as Analogues of Plutonium Ceramic Waste-form

MRS Proceedings ◽

10.1557/proc-713-jj2.2 ◽

2002 ◽

Vol 713 ◽

Cited By ~ 1

Author(s):

Roman V. Bogdanov ◽

Yuri F. Batrakov ◽

Elena V. Puchkova ◽

Andrey S. Sergeev ◽

Boris E. Burakov

Keyword(s):

Chemical Shifts ◽

Pyrochlore Structure ◽

Type Structure ◽

Waste Form ◽

X Ray ◽

Ceramic Waste ◽

Natural Minerals ◽

The Us ◽

Pyrochlore Type

ABSTRACTAt present, crystalline ceramic based on titanate pyrochlore, (Ca,Gd,Hf,Pu,U)2Ti2O7, is considered as the US candidate waste form for the immobilization of weapons grade plutonium. Naturally occuring U-bearing minerals with pyrochlore-type structure: hatchettolite, betafite, and ellsworthite, were studied in orders to understand long-term radiation damage effects in Pu ceramic waste forms. Chemical shifts (δ) of U(Lδ1)– and U(Lβ1) – X-ray emission lines were measured by X-ray spectrometry. Calculations were performed on the basis of a two-dimensional δLá1- and δLδ1- correlation diagram. It was shown that 100% of uranium in hatchettolite and, probably, 95-100% of uranium in betafite are in the form of (UO2)2+. formal calculation shows that in ellsworthite only 20% of uranium is in the form of U4+ and 80% of the rest is in the forms of U5+ and U6+. The conversion of the initial U4+ ion originally occurring in the pyrochlore structure of natural minerals to (UO2)2+ due to metamict decay causes a significant increase in uranium mobility.

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Long-Term Stability of Different Kinds of Gas Nanobubbles in Deionized and Salt Water

Materials ◽

10.3390/ma14071808 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1808

Author(s):

Yali Zhou ◽

Zhenyao Han ◽

Chunlin He ◽

Qin Feng ◽

Kaituo Wang ◽

...

Keyword(s):

Aqueous Solution ◽

Bubble Size ◽

Ostwald Ripening ◽

Salt Water ◽

Dlvo Theory ◽

Deionized Water ◽

Hydrodynamic Cavitation ◽

Term Stability ◽

Long Term Stability

Nanobubbles have many potential applications depending on their types. The long-term stability of different gas nanobubbles is necessary to be studied considering their applications. In the present study, five kinds of nanobubbles (N2, O2, Ar + 8%H2, air and CO2) in deionized water and a salt aqueous solution were prepared by the hydrodynamic cavitation method. The mean size and zeta potential of the nanobubbles were measured by a light scattering system, while the pH and Eh of the nanobubble suspensions were measured as a function of time. The nanobubble stability was predicted and discussed by the total potential energies between two bubbles by the extended Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. The nanobubbles, except CO2, in deionized water showed a long-term stability for 60 days, while they were not stable in the 1 mM (milli mol/L) salt aqueous solution. During the 60 days, the bubble size gradually increased and decreased in deionized water. This size change was discussed by the Ostwald ripening effect coupled with the bubble interaction evaluated by the extended DLVO theory. On the other hand, CO2 nanobubbles in deionized water were not stable and disappeared after 5 days, while the CO2 nanobubbles in 1 mM of NaCl and CaCl2 aqueous solution became stable for 2 weeks. The floating and disappearing phenomena of nanobubbles were estimated and discussed by calculating the relationship between the terminal velocity of the floating bubble and bubble size.

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The Relationship Between Magnetism and Microstructure of Ethylene Pyrolysis Furnace Tubes after a Long-term Service

Microscopy and Microanalysis ◽

10.1017/s1431927618015180 ◽

2018 ◽

Vol 24 (5) ◽

pp. 478-487 ◽

Cited By ~ 1

Author(s):

Jingfeng Guo ◽

Tieshan Cao ◽

Congqian Cheng ◽

Xianming Meng ◽

Jie Zhao

Keyword(s):

Saturation Magnetization ◽

Outer Region ◽

Cr Content ◽

Pyrolysis Furnace ◽

The Matrix ◽

Furnace Tube ◽

Primary Carbides ◽

The Relationship ◽

Very High

AbstractThe magnetism and microstructure of Cr25Ni35Nb and Cr35Ni45Nb alloy tubes after 5 years of service were investigated in this paper. The saturation magnetization of the Cr25Ni35Nb alloy tube in the thickness direction is more than 20 emu/g, and the tube becomes ferromagnetic. The inner and outer walls of Cr35Ni45Nb alloy tubes also become ferromagnetic. But the saturation magnetization of the Cr35Ni45Nb alloy tubes approaches to zero in the center zone. The primary carbides M7C3 and NbC are changed into M23C6 and G phase at the outer region of the furnace tube. However, the M23C6-type carbides were replaced by carbon-rich carbides M7C3 at the carburization zone. Cr-depleted zones are formed at the inner and outer walls of the furnace tubes owing to oxidation. Carburization and oxidation reduce the Cr content of the matrix. Accordingly, the saturation magnetization is very high at the carburization zone and Cr-depleted zone. The magnetism of Cr25Ni35Nb and Cr35Ni45Nb alloy tubes has a high correlation with the Cr content of the matrix. Carburization and oxidation are the main reasons that make the paramagnetic ethylene pyrolysis furnace tube change to ferromagnetic.

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A clinical review of early outcomes from contemporary flow modulation versus open, fenestrated and branch technologies in the management of thoracoabdominal aortic aneurysm

Vascular ◽

10.1177/1708538117724933 ◽

2017 ◽

Vol 26 (2) ◽

pp. 209-215 ◽

Cited By ~ 3

Author(s):

Sherif Sultan ◽

Edel P Kavanagh ◽

Edward Diethrich ◽

Victor Costache ◽

Mohamed Sultan ◽

...

Keyword(s):

Thoracoabdominal Aortic Aneurysm ◽

Disruptive Technology ◽

Management Options ◽

Flow Modulation ◽

Risk Of Mortality ◽

Clinical Literature ◽

Hybrid Repair ◽

Aortic Pathologies ◽

Treatment Application

Traditional therapeutic options for complex thoracoabdominal aneurysm include open repair, hybrid repair or endovascular repair (involving fenestrated or branched endografts). The Streamliner Multilayer Flow Modulator has been available for treatment of thoracoabdominal aneurysms since 2010. Its design permits blood flow to perfuse through the mesh in a modus that preserves collateral branch patency, while modulating turbulent to laminar flow within the device. The flow then stagnates over time within the surrounding aneurysm sac. Significant complications, including paraplegia, renal failure and cerebrovascular accident, are much lower with Streamliner Multilayer Flow Modulator treatment. Application of the Streamliner Multilayer Flow Modulator to complex aortic pathologies presents a novel solution to an, as of yet, unmet clinical need, and has resulted in promising clinical outcomes when compared to existing solutions. The Streamliner Multilayer Flow Modulator offers potential for treatment of thoracoabdominal aortic pathologies in patients and is not just confined to those with complexity that dictates no other management options. While current literature illustrates that there is a decreased risk of mortality and associated complications when this new disruptive technology is utilised, there is still a need for prospective, long-term clinical trials, as well as comparative trials to accurately assess outcomes of Streamliner Multilayer Flow Modulator treatment that are both precise and reproducible. This article is a review of current clinical literature regarding contemporary flow modulating technology compared with open, branched and fenestrated managements, presenting early outcomes.

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Aging Studies of Pu-238 and -239 Containing Calcium Phosphate Ceramic Waste-forms

MRS Proceedings ◽

10.1557/opl.2013.926 ◽

2013 ◽

Vol 1518 ◽

pp. 73-78 ◽

Cited By ~ 1

Author(s):

Shirley K. Fong ◽

Brian L. Metcalfe ◽

Randall D. Scheele ◽

Denis M. Strachan

Keyword(s):

Calcium Phosphate ◽

Accelerated Aging ◽

Waste Form ◽

Calcium Phosphate Ceramic ◽

Ceramic Waste ◽

Waste Forms ◽

Aging Studies ◽

Flow Through ◽

Pyrochemical Reprocessing

ABSTRACTA calcium phosphate ceramic waste-form has been developed at AWE for the immobilisation of chloride containing wastes arising from the pyrochemical reprocessing of plutonium. In order to determine the long term durability of the waste-form, aging trials have been carried out at PNNL. Ceramics were prepared using Pu-239 and -238, these were characterised by PXRD at regular intervals and Single Pass Flow Through (SPFT) tests after approximately 5 yrs.While XRD indicated some loss of crystallinity in the Pu-238 samples after exposure to 2.8 x 1018 α decays, SPFT tests indicated that accelerated aging had not had a detrimental effect on the durability of Pu-238 samples compared to Pu-239 waste-forms.

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Sediment Mining

Linnaeus Eco-Tech ◽

10.15626/eco-tech.2012.008 ◽

2017 ◽

Author(s):

Homayoun Fathollahzadeh ◽

Fabio Kaczala ◽

Amit Bhatnagar ◽

William Hogland

Keyword(s):

Climate Change ◽

Global Warming ◽

Contaminated Sediments ◽

Management Options ◽

Metals Recovery ◽

Environmental Footprints ◽

Valuable Metals ◽

Short And Long Term ◽

Near Future

The main dilemma of contaminated sediments has been the proper management with reduced environmental footprints. Furthermore, by considering the fact that global warming and climate change may complicate the choice of management options, finding appropriate solutions become extremely critical. In the present work, mining of contaminated sediments to recover valuable constituents such as metals and nutrients is proposed as sustainable strategy, both through enhancing resilience of ecosystem and remediation. Contaminated sediments in the Oskarshamn harbor, southeast of Sweden were collected and analyzed through a modified sequential extraction in order to evaluate the feasibility of metals recovery. The results have shown that among different metals present in the sediments, Cu and Pb can be initially considered as economically feasible to recover. The shifting in the concept of dredging and further remediation of contaminated sediments towards sediment mining and recover of valuable metals can be considered in the near future as a sustainable strategy to tackle contaminated harbor/ports areas. However, it must be highlighted that short and long-term environmental impacts related to such activities should be addressed.

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The social context for conservation: amphibians in human-shaped landscapes

10.7287/peerj.preprints.27918 ◽

2019 ◽

Author(s):

Tibor Hartel ◽

Ben C Scheele ◽

Laurentiu Rozylowicz ◽

Andra Horcea-Milcu ◽

Dan Cogalniceanu

Keyword(s):

Protected Areas ◽

Amphibian Conservation ◽

Social Aspects ◽

Direct Control ◽

Adaptive Potential ◽

Management Options ◽

Economic Context ◽

The Social ◽

Natural Landscapes

Many human-shaped landscapes support viable amphibian populations due to the habitats created and/or maintained as a consequence of human actions. The challenges and approaches required to achieve the persistence of amphibians in human-shaped landscapes are markedly different from approaches commonly applied in protected areas. Contrary to protected areas or natural landscapes where amphibian conservationists can have direct control over management, in human-shaped landscapes, management options are best approached through understanding local communities’ values and socio-economic aspirations. However, consideration of the social aspects of amphibian conservation are vastly under-represented in the amphibian conservation literature. We propose that amphibian conservationists should: (i) assess the controllability of their mitigation actions for achieving long-term sustainability, (ii) understand the values and attitudes of individual landowners towards amphibians and amphibian-friendly management (local scale) and land stewardship on which amphibian conservation initiatives can be built (landscape scale), and (iii) understand the social and economic drivers of land-use change operating at regional levels, which is crucial for building adaptive potential in conservation programs. Since targeted amphibian conservation initiatives are limited in many human-shaped landscapes, consideration of the socio-economic context conducive to amphibian persistence is crucial.

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