Performance Assessment of Glass As A Long-Term Barrier To The Release of Radionuclides Into The Environment

1987 ◽  
Vol 112 ◽  
Author(s):  
B. Grambow ◽  
W. Lutze ◽  
R. C. Ewing
Keyword(s):  
Performance Assessment ◽  
Source Term ◽  
Constant Rate ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Nuclear Waste Forms ◽  
Single Constant ◽  
Selection Of ◽  
Weathering Effects

AbstractPerformance assessment of high-level nuclear waste forms in a repository must cover periods of time on the order of hundreds of thousands of years. There has rarely been a need to extrapolate the properties of a material over such long periods of time (except in the geologic sciences, e.g., the evaluation of long-term weathering effects based on results from laboratory experiments) and there has never been a more important need to make accurate and -verifiable “predictions” of the long-term materials performance. The results of such extrapolations could affect decisions concerning the selection of a repository and the number and types of barriers that are required to insure isolation over long periods of time. In typical safety analyses [1,2] waste form corrosion is described by a single constant rate, and no effort is made to evluate whther the modal of the “source term” can be substantiated or verified by comparison similar or analogous processes [3].

Performance Assessments of Geologic Repositories for High-Level Nuclear Waste: Are They Necessary or Sufficient?

2004 ◽  
Vol 824 ◽  
Author(s):  
Rodney C. Ewing
Keyword(s):  
Performance Assessment ◽  
Nuclear Waste ◽  
System Analysis ◽  
Regulatory Compliance ◽  
Performance Assessments ◽  
Data Uncertainty ◽  
Emergent Properties ◽  
Total System ◽  
High Level Nuclear Waste ◽  
High Level

AbstractPerformance assessments of geologic repositories for high-level nuclear waste will be used to determine regulatory compliance. The determination, that with a “reasonable expectation” regulatory limits are met, is based on the presumption that all of the relevant physical, chemical and biological processes have been modeled with enough accuracy to insure that a confident judgment of safety may be made. For the geologic disposal of high-level nuclear waste, this generally means that models must be capable of calculating radiation exposures to a specified population at distances of tens of kilometers for periods of tens to hundreds of thousands of years. A total system performance assessment will consist of a series of cascading models that are meant in toto to capture repository performance. There are numerous sources of uncertainty in these models: scenario uncertainty, conceptual model uncertainty and data uncertainty. These uncertainties will propagate through the analysis, and the uncertainty in the total system analysis must necessarily increase with time. For the highly-coupled, non-linear systems that are characteristic of many of the physical and chemical processes, one may anticipate emergent properties that cannot, in fact, be predicted. For all of these reasons, a performance assessment is not in and of itself a sufficient basis for determining the safety of a repository, but it remains a necessary part of the effort to develop a substantive understanding of a repository site.

scholarly journals Effect of Thermal Treatments on Sn-Alloyed Al-Mg-Si Alloys

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1801
Author(s):  
Florian Schmid ◽  
Peter J. Uggowitzer ◽  
Robin Schäublin ◽  
Marion Werinos ◽  
Thomas Ebner ◽  
...  
Keyword(s):  
Natural Aging ◽  
Positive Influence ◽  
Processing Route ◽  
Thermal Treatments ◽  
Intermetallic Particles ◽  
Aging Kinetics ◽  
High Level ◽  
Fast Quenching ◽  
Selection Of

Sn-alloying, by deploying comparatively high vacancy binding energy, mitigates the undesired natural aging behavior of 6xxx-alloys. Targeted selection of pre-aging parameters can have a positive influence on natural aging and paint-bake performance. In this study, we aimed to combine the two approaches of Sn-alloying and pre-aging. Our results indicate that alloys modified with 100 at.-ppm Sn require altered heat treatment. In terms of solution aging and quenching, we show that the cooling rate needed depends on the types of alloy. The rate must be adapted, according to the number of intermetallic particles, to guarantee a sufficiently high level of Sn atoms in solid solution. The rather high number of intermetallic phases in alloy EN-AW-6061 means that it requires fast quenching, while the comparatively low number of precipitate-forming elements in alloy EN-AW-6016 makes it less sensitive to quenching variations. We also show that Sn reduces pre-aging kinetics. The optimal pre-aging temperature and time were consequently found to increase when Sn is added. We also studied the effect of adding a further thermal spike to the usual long-term pre-aging, at different positions within the processing route. The results we present are discussed based on a simulation of vacancy evolution in the alloy when subjected to these treatments.

Evaporative Evolution of Carbonate-Rich Brines from Synthetic Topopah Spring Tuff Pore Water, YuccaMountain, NV

2004 ◽  
Vol 824 ◽  
Author(s):  
Mark Sutton ◽  
Maureen Alai ◽  
Susan Carroll
Keyword(s):  
Pore Water ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Pore Waters ◽  
Starting Solution ◽  
Sequential Experiments ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Topopah Spring Tuff

AbstractThe evaporation of a range of synthetic pore water solutions representative of the potential high-level-nuclear-waste repository at Yucca Mountain, NV is being investigated. The motivation of this work is to understand and predict the range of brine compositions that may contact the wastecontainers from evaporation of pore waters, because these brines could form corrosive thin films on the containers and impact their long-term integrity. A relatively complex synthetic Topopah Spring Tuff pore water was progressively concentrated by evaporation in a closed vessel, heated to 95°C in a series of sequential experiments. Periodic samples of the evaporating solution were taken to determine the evolving water chemistry. According to chemical divide theory at 25°C and 95°C our starting solution should evolve towards a high pH carbonate brine. Results at 95°C show that this solution evolves towardsa complex brinethat contains about 99 mol% Na+for the cations, and 71 mol% Cl-, 18 mol% ΣCO2(aq), 9 mol% SO42- for the anions. Initial modeling ofthe evaporating solution indicates precipitation of aragonite, halite, silica, sulfate and fluoride phases. The experiments have been used to benchmark the use of the EQ3/6 geochemical code in predicting the evolution of carbonate-rich brines during evaporation.

Comparison of Granite, Tuff, and Basalt as Geologic Media for Long-Term Storage of High-Level Nuclear Waste

1990 ◽  
Vol 212 ◽  
Author(s):  
D. E. Grandstaff ◽  
V. J. Grassi ◽  
A. C. Lee ◽  
G. C. Ulmer
Keyword(s):  
Nuclear Waste ◽  
Nuclear Waste Repository ◽  
Long Term Storage ◽  
Hydrothermal Experiments ◽  
Ion Activity ◽  
Activity Ratios ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Term Storage

ABSTRACTSystematic differences in pH, cation/proton ion activity ratios, and redox have been observed between solutions produced in rock-water hydrothermal experiments with tuff, granite, and basalt. Stable pH values in tuff-water experiments may be as much as 1.5 pH units more acidic than basalt-water experiments at the same temperature and ionic strength. Redox (log fO2) values in 300°C tuff experiments are 4–7 orders of magnitude more oxidizing than basalt experiments and ca. 4 log units more oxidizing than the magnetite-hematite buffer. Such fluid differences could significantly affect the performance of a high-level nuclear waste repository and should be considered in repository design and siting.

Evaporative Evolution of Brines from Synthetic Topopah Spring Tuff Pore Water, Yucca Mountain, NV

2002 ◽  
Vol 757 ◽  
Author(s):  
Maureen Alai ◽  
Susan Carroll
Keyword(s):  
Pore Water ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Level Nuclear Waste ◽  
Series Of Experiments ◽  
High Level ◽  
Topopah Spring Tuff

ABSTRACTWe are investigating the evaporation of pore water representative of the designated high-level-nuclear-waste repository at Yucca Mountain, NV to predict the range of brine compositions that may contact waste containers. These brines could form potentially corrosive thin films on the containers and impact their long-term integrity. Here we report the geochemistry of a relatively complex synthetic Topopah Spring Tuff pore water that was progressively evaporated in a series of experiments. The experiments were conducted in a vented vessel in which HEPA filtered air flowed over the 95°C solution. Samples of the evaporating solution and the condensed vapor were taken and analyzed to determine the evolving water chemistry and gas volatility. The final solid was analyzed by X-ray diffraction.The synthetic Topopah Spring Tuff water evolved towards a complex brine that contained about 45 mol % Cl, 7 mol% NO3, 43 mol% Na, 4 mol % K, and less than 1 mol % each of SO4, Ca, Mg, HCO3 and Si. Trends in the solution data and identification of CaSO4 solids suggest that fluorite, carbonate, sulfate, and Mg-silicate precipitation minimize the corrosion potential of “sulfate type pore water” by removing F, Ca, and Mg during the early stages of evaporation.

NUMO’s Open Solicitation of Volunteer Municipalities for a Potential Disposal Site

2003 ◽  
Author(s):  
Kazumi Kitayama
Keyword(s):  
Radioactive Waste ◽  
Preliminary Investigation ◽  
Disposal Site ◽  
Nuclear Waste Management ◽  
The Public ◽  
Construction Operation ◽  
High Level ◽  
Year 2000 ◽  
Selection Of

In the year 2000, the Japanese geological disposal program for high-level radioactive waste (HLW) moved from the phase of generic research and development into the phase of implementation. Following legislation entitled the “Specified Radioactive Waste Final Disposal Act” (hereafter “the Act”), the Nuclear Waste Management Organization of Japan (NUMO) was established as the implementing organization in October 2000. The assigned activities of NUMO include repository site selection, developing relevant license applications and construction, operation and closure of the repository. To initiate the first stage, NUMO has chosen an “open solicitation” approach for finding candidate sites in the belief that the support of local communities is essential to the success of this highly public, long-term project extending over more than a century. Based on this concept, NUMO announced the start of open solication for volunteer municipalities for selection of Preliminary Investigation Areas to the public on December 19, 2002. This paper describes NUMO’s open solicitation of volunteer municipalities for a potential disposal site.

scholarly journals New trends in the reprocessing of spent nuclear fuel. Separation of minor actinides by solvent extraction

2016 ◽  
Vol 71 (1) ◽  
pp. 123
Author(s):  
Jerzy Narbutt
Keyword(s):  
Solvent Extraction ◽  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
Fission Products ◽  
Natural Uranium ◽  
Heterocyclic Ligands ◽  
High Level Nuclear Waste ◽  
Extraction Processes ◽  
High Level

<p>Recycling of actinides from spent nuclear fuel by their selective separation followed by transmutation in fast reactors will optimize the use of natural uranium resources and minimize the long-term hazard from high-level nuclear waste. This paper describes solvent extraction processes recently developed, aimed at the separation of americium from lanthanide fission products as well as from curium present in the waste. Depicted are novel poly-N-heterocyclic ligands used as selective extractants of actinide ions from nitric acid solutions or as actinide-selective hydrophilic stripping agents.</p>

Sign in / Sign up

Export Citation Format

Share Document