Preferential Dissolution Phenomena of Nuclear Waste Materials

1982 ◽  
Vol 15 ◽  
Author(s):  
D. R. Clarke ◽  
J. F. Flintoff
Keyword(s):  
Nuclear Waste ◽  
Waste Materials ◽  
Green Density ◽  
Release Rates ◽  
Short Term ◽  
Rate Of Dissolution ◽  
Soluble Phase ◽  
Precursor Powders ◽  
Radionuclide Release ◽  
Preferential Dissolution

ABSTRACTPreferential dissolution of polyphase nuclear waste materials in short term leach tests can exaggerate radionuclide release rates when extrapolated to the lifetime of the waste form. Possible preferential leach phenomena are associated with the presence of cracks, intergranular phases and readily soluble phases. The rate of dissolution and the microstructural connectivity of the most soluble phase determine the period over which perferential dissolution is observable. The connectivity of phases is amenable to control during processing by altering the starting green density of the precursor powders.

The Development of a Mechanistic Basis for Modelling Fuel Dissolution and Container Failures Under Waste Vault Conditions

1988 ◽  
Vol 127 ◽  
Author(s):  
D. W. Shoesmith ◽  
S. Sunder ◽  
B. M. Ikeda ◽  
F. King
Keyword(s):  
Experimental Data ◽  
Titanium Alloys ◽  
Nuclear Waste ◽  
Waste Disposal ◽  
Predictive Models ◽  
Crevice Corrosion ◽  
Electrochemical Techniques ◽  
Short Term ◽  
Mechanistic Basis ◽  
Radionuclide Release

ABSTRACTDue to the long containment periods required for radionuclides in a nuclear waste disposal vault, the justification that a particular containment system is acceptable will be based on relatively short-term experimental data used to support predictive models. To justify this approach, we must possess a sound mechanistic understanding of processes such as fuel dissolution, radionuclide release and container corrosion. Since these processes are driven by oxidants in the vault, it is natural to study them by electrochemical techniques. In this paper, we have reviewed a number of electrochemical methods used in the study of waste vault reactions. More detailed descriptions are given of the development of predictive models for the dissolution of UO2, the crevice corrosion of titanium alloys and the uniform dissolution of copper.

Electrokinetics, Adsorption and Colloid Study of Simulated Nuclear Waste Glasses Leached in Aqueous Solutions

1984 ◽  
Vol 44 ◽  
Author(s):  
Cheng T. Lee ◽  
D. E. Clark
Keyword(s):  
Surface Layer ◽  
Nuclear Waste ◽  
Glass Surface ◽  
Charged Particles ◽  
Electrostatic Repulsion ◽  
Surface Layers ◽  
Short Term ◽  
Chloride Solutions ◽  
Zeta Potentials ◽  
Glass Surfaces

AbstractZeta potentials of SRL-131-29.8% TOS simulated nuclear waste glasses leached in D.I. water, Al, Ca, Mg, and Zn chloride solutions at 90°C were measured as a function of leaching time. For short term leaching, the adsorption of Ca, Mg, Zn and Al reverses the glass surface potential from negative to positive. Colloids were found to be stable in D.I. water and AICl3 solutions after leaching, presumably due to the electrostatic repulsion between the glass surface and similarly charged particles. Colloids were not found in Mg, Zn or Ca chloride solutions after leaching; instead, a relatively thick metasilicate surface layer was formed on glass surfaces leached in these solutions. The concentration of Si in solution is reduced by the formation of these surface layers.

scholarly journals Standard Leach Tests for Nuclear Waste Materials

1981 ◽  
pp. 347-354 ◽  
Author(s):  
D. M. Strachan ◽  
B. O. Barnes ◽  
R. P. Turcotte
Keyword(s):  
Nuclear Waste ◽  
Waste Materials

Diffusion of Plutonium in Compacted, Brine-Saturated Bentonite

1984 ◽  
Vol 44 ◽  
Author(s):  
E. J. Nowak
Keyword(s):  
Radioactive Waste ◽  
Packing Density ◽  
Solution Chemistry ◽  
Lithostatic Pressure ◽  
Release Rates ◽  
Rock Types ◽  
Diffusion Studies ◽  
Engineered Barriers ◽  
Radionuclide Release ◽  
Wyoming Bentonite

AbstractDiffusivities were measured for plutonium in brine-saturated compacted Wyoming bentonite. Complexities of the solution chemistry and retardation of transuranics necessitate diffusion studies under conditions that are specific for repository host rock types in this case salt. Diffusivity values in the range of 10−15 to 10−14 m2/s were obtained for bentonite at a packing density of 1800 kg/m3. That density was obtained by compaction at 15 i0Pa, a typical lithostatic pressure in a repository in salt at 650 m depth. Even a 0.05 m (2 inch) thick bentonite-containing engineered barrier could decrease radionuclide release rates by approximately 4 orders-of-magnitude if the diffusivity for that radionuclide were in the observed range of 10−15 to 10−14 m2/s. These results confirm the effectiveness of uncompacted bentonite-containing materials as engineered barriers for radioactive waste isolation.

scholarly journals The dissolution of simulant vitrified intermediate level nuclear waste in young cement water

MRS Advances ◽  
2020 ◽  
Vol 5 (3-4) ◽  
pp. 131-140
Author(s):  
Colleen Mann ◽  
Jeremy R. Eskelsen ◽  
Donovan N. Leonard ◽  
Eric Pierce ◽  
Claire L Corkhill
Keyword(s):  
Nuclear Waste ◽  
Alkaline Earth ◽  
Water Solution ◽  
Cementitious Materials ◽  
Intermediate Level ◽  
Short Term ◽  
Alkaline Earth Elements ◽  
Altered Layer ◽  
Safety Case ◽  
The Uk

AbstractIt is pertinent to the safety case for geological disposal in the UK that the behaviour of vitrified wastes in proximity to cementitious materials is understood. In this study, vitrified simulant intermediate level nuclear waste (ILW) was subject to dissolution in a synthetic cement water solution to simulate disposal conditions. Results show that the presence of alkali / alkaline earth elements in the cementitious solution can be favourable, at least in the short-term, leading to lower dissolution rates associated with incorporation of these elements into the altered layer of the glass.

Second Difference Electron Energy-Loss Spectroscopy with the Gatan Imaging Filter

1999 ◽  
Vol 5 (S2) ◽  
pp. 808-809
Author(s):  
E.C. Buck
Keyword(s):  
Nuclear Waste ◽  
High Frequency ◽  
Waste Materials ◽  
White Line ◽  
Minor Elements ◽  
Gain Variation ◽  
Line Absorption ◽  
Electron Energy Loss ◽  
Frequency Features ◽  
Array Gain

The large number of minor elements present in geological specimens and nuclear waste materials, can make TEM/EDS analysis of such samples troublesome. With a parallel detector such as the Gatan PEELS 666, the second difference technique has been shown to be effective at removing the channel-to-channel gain variation [1]. As spectroscopy performed with the Gatan Imaging Filter (GIF200) averages over a 2D array, gain variations are minimal; however, the second-difference technique selectively enhances the high frequency features such as the “white line” absorption edges, particularly of rare earth elements (REE) and transuranics (TRU). The second difference method may thus still have merit with the GIF200. A script was created within the controlling software program (DigitalMicrograph ™) which permitted second difference acquisition [2]. The Spectroscopy Package was also modified with ResEdit and the required values were added to the Global Tags to enable easy application of the second difference routine.

Opportunities for Research in the UK for Decommissioning and Disposal

2008 ◽  
Vol 1107 ◽  
Author(s):  
Neil Smart
Keyword(s):  
Nuclear Waste ◽  
Life Time ◽  
Short Term ◽  
Site License ◽  
Technology Gaps ◽  
The Uk ◽  
High Level ◽  
Technical Solutions ◽  
Programme Delivery ◽  
Fund Research

AbstractThe NDA remit as set out within the Energy Act includes – “promote, and where necessary fund, research relevant to nuclear clean up”. The NDA need to underpin delivery and / or accelerate programmes to fulfil the overall mission and technical underpinning of these activities is critical. In this paper we will present consideration of the investment required in nuclear waste Research and Development.Firstly, NDA set the requirement for nuclear sites to write down within the Life Time Plans (LTP), at a high level, the proposed technical baseline underpinning the LTP activities; furthermore we required technology gaps / opportunities in the technical baselines to be outlined in a R&D requirements section to the LTP. Criteria were established to categorise the R&D in three areas:“needs” - those development activities needed to underpin the proposed technical solutions“risks” – those activities required to reduce / eliminate key risks to the proposed technical solutions“opportunities” – innovations / changes to the technical baselinesThe purpose of production of the technical baselines and underpinning R&D requirements is to establish an auditable trail through the LTP from programme components into how the programme will be delivered.NDA believes the production of the technical baselines and R&D requirements will be of benefit to the Site License Companies (SLC) in terms of ensuring a focus on overall programme delivery and not just short term activities. Furthermore, we can ensure that investment in technology is targeted at priority areas, with common issues and requirements identified and solutions on a broader scale will be achievable.

Estimating rates of fish movement from tag recoveries: conditioning by recapture

2002 ◽  
Vol 59 (6) ◽  
pp. 1054-1064 ◽  
Author(s):  
Richard McGarvey ◽  
John E Feenstra
Keyword(s):  
South Australia ◽  
Total Mortality ◽  
Transition Matrices ◽  
Release Rates ◽  
Short Term ◽  
Time Step ◽  
Fish Stocks ◽  
Movement Rates ◽  
Tag Loss ◽  
Spatial Cell

Tag-recovery data are commonly used to estimate movement rates of fish stocks. Fishers report tagged fish found in their catch; however, not all recoveries are reported to fishery researchers and the rate of nonreporting is usually not known or is imprecisely estimated. To obviate the problem of nonreporting, an estimator of movement rates is proposed that does not use the number originally tagged but is fitted to the relative proportions recaptured in each cell in each time step subsequent to release. Rates of processes that occur in the tag-release spatial cell, such as short-term tagging mortality and survival, cancel from the predicted likelihood probabilities. Similarly, rates in the recapture cell for processes of ongoing tag loss, natural mortality, and tag nonreporting, if they can be reasonably approximated as uniform across cells, also cancel. Estimators are presented assuming one of two levels of auxiliary fishery inputs: (i) total mortality by cell or time step, or (ii) if mortality can be approximated as spatially uniform, effort totals in each cell, by time step. Yearly movement transition matrices were estimated for King George whiting (Sillaginodes punctata) in South Australia among 11 spatial cells from tag recoveries gathered over a period of three decades.

scholarly journals Radiation Effects in Nuclear Waste Materials

2000 ◽  
Author(s):  
William J. Weber ◽  
L. Rene Corrales ◽  
Nancy J. Ness ◽  
Ralph E. Williford ◽  
Howard L. Heinisch ◽  
...  
Keyword(s):  
Nuclear Waste ◽  
Radiation Effects ◽  
Waste Materials
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