bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquidus Temperature of Spinel Precipitating High-Level Waste
Glasses
Authors: Mika M. , Schweiger M. J. , Vienna J. D. , Hrma P. 
Published: September 2012

ABSTRACTThe liquidus temperature (TL) often limits the loading of
high-level waste in glass through the constraint that TL must be
at least 100°C below the temperature at which the glass viscosity is 5 Pa-s.
In this study, values of TL for spinel primary crystalline phase
were measured as a function of glass composition. The test glasses were
based on high-iron Hanford Site tank wastes. All studied glasses
precipitated spinel (Ni,Fe,Mn)(Cr,Fe)2O4 as the
primary crystalline phase. TL was increased by additions of
Cr2O3, NiO, Al2O3,
Fe2O3, MgO, and MnO; while Li2O,
Na2O, B2O3, and SiO2 had a
negative effect. Empirical mixture models were fitted to data.
Complexation of Transuranic Ions by Humic Substances: Application of Laboratory Results to the Natural System
Authors: Czerwinski Ken , Kim Jae-Il 
Published: September 2012

ABSTRACTEnvironmental investigations show transuranic ions sorb to humic substances. The resulting species are often mobile and are expected to be important vectors in the migration of transuranic ions in natural systems. However, theses environmental studies yield no quantitative data useful for modeling. Laboratory complexation experiments with transuranic ions and humic substances generate mermodynamic data required for complexation modeling. The data presented in this work are based on the metal ion charge neutralization model, which is briefly described. When a consistent complexation model is used, similar results are obtained from different experimental conditions, techniques, and laboratories. Trivalent transuranic ions (CM(III), AM(III)) have been extensively studied with respect to pH, ionic strength, origin of humic acid, and mixed species formation. The complexation of Np(V) has been examined over a large pH and metal ion concentration range with different humic acids. Some data does exist on the complexation of plutonium with humic acid, however further work is needed. Calculations on the Gorleben aquifer system using the thermodynamic data are presented. Critical information lacking from the mermodynamic database is identified.
The Effect of Specific Surface Area on Radionuclide Sorption on
Crushed Crystalline Rock
Authors: Hölttä P. , Siitari-Kauppi M. , Huihuri P. , Lindberg A. , Hautojärvt A. 
Published: September 2012

ABSTRACTThe sorption of sodium (22Na), calcium (45Ca) and
strontium (85Sr) was studied on mica gneiss, unaltered,
moderately altered and strongly altered tonalite samples taken from hole
SY-KR7 drilled in the Syyry area in Sievi, Western Finland. The crushed rock
samples were sieved into six fractions from 71 μm to 1250 μm. A proportional
mineral composition for the different fractions were estimated by X-ray
diffraction. The specific fraction surface areas were determined by the BET
nitrogen adsorption method. The fractal method was applied to characterize
rocks and to describe quantitatively surface irregularity. The mass
distribution ratio values for each fraction were determined using the static
batch method. The sorption of tracers onto different minerals was observed
using rock thin sections. Kd-values calculated from thin section
Ka-values and Kd revalues obtained from batch
experiments were in good agreement. Mass distribution ratios for different
size fractions are given, and the effect of the specific surface area is
discussed. Owing to larger specific surface areas considerably higher
sorption on smaller fractions was found for altered tonalites.
The Effect of Temperature on the Sorption of Technetium, Uranium, Neptunium and Curium on Bentonite, Tuff and Granodiorite
Authors: Baston G M N , Berry J A , Brownsword M , Heath T G , Blett D J , Tweed C J , Yui M 
Published: September 2012

ABSTRACTA study of the sorption of the radioelements: technetium; uranium; neptunium; and curium onto geological materials has been carried out as part of the PNC programme to increase confidence in the performance assessment for a high-level radioactive waste repository in Japan. Batch sorption experiments have been performed in order to study the sorption of the radioelements onto bentonite, tuff and granodiorite from equilibrated de-ionised water under strongly-reducing conditions at both room temperature and at 60°C.Mathematical modelling using the geochemical speciation program HARPHRQ in conjunction with the HATCHES database has been undertaken in order to interpret the experimental results.
Characterization of Electroactive Cs Ion-Exchange Materials
using XAS
Authors: Hess N. J. , Sukamto J. H. , Rassat S. D. , Hallen R. T. , Orth R. J. , Lilga M. A. , Lawrence W. E. 
Published: September 2012

ABSTRACTVarious ion exchange materials have been proposed for the removal of Cs from
high level waste streams produced during the reprocessing of fuel rods. Cs
can be released from loaded traditional exchange resins by elution and then
the resin can be reused. However large quantities of secondary wastes are
generated. Another class of “single use” exchangers is directly incorporated
in the loaded state into a solid waste form (e.g. borosilicate glass logs).
A third alternative is electroactive ion-exchange materials, where the
uptake and elution of Cs are controlled by an applied potential. This
approach has several advantages over traditional reusable ion-exchange
resins including much reduced secondary waste, higher Cs selectivity, and
higher durability.XAS experiments were conducted at the Fe K-edge and Cs Lm-edge on
a series of electrochemically produced nickel ferrocyanide films to
determine the effects of deposition conditions and subsequent alkali
exchange on structural and chemical aspects of the films. The deposition
conditions include methods described in the literature and PNNL proprietary
procedures. Although the performance and the durability of the films do vary
with processing conditions, Fe K-edge EXAFS results indicate that all
deposition conditions result in the. formation of the cubic phase. Initial
results from Cs Lm-edge EXAFS analysis suggest that the Cs ion is
present as a hydrated species.
Groundwater Colloid Properties and their Potential Influence on
Radionuclide Transport
Authors: Degueldre C. 
Published: September 2012

ABSTRACTColloid facilitated transport is still an issue in radioactive waste
management. Sophisticated phenomenological transport models are available,
but progress is required to fully understand mechanisms and parameters. This
study lead in this direction. Investigation of the marl groundwater colloids
in steady-state conditions at Wellenberg, shows that their concentration is
independent of the water flow rate. Their generation is caused by the
re-suspension of the rock clay fraction only. The re-suspension process is
presently being studied under flow transient conditions. Extension of our
measurements to other safety relevant systems as well as a literature survey
show that the colloid concentration under steady-state conditions is
correlated to the concentration of alkali elements and earth alkali
elements. The higher their respective concentration, the fewer colloids are
occurring. Considerations on colloid contamination models are also included.
The paper emphasises various colloid transport mechanisms including colloid
generation from the irreversibly contaminated aquifer.
Investigation of Rock Samples Using X-Ray-Microcomputer-Tomography Before and After Mercury Intrusion Porosimetry
Authors: Klobes P. , Riesemeier H. , Meyer K. , Goebbels J. , Siitari-Kauppi M. , Hellmuth K-H. 
Published: September 2012

ABSTRACTA new method for the physical characterization of rock matrices for use in site investigations of nuclear waste repositories has been developed. The method can provide information needed in the assessment of the performance of the geosphere working as a natural barrier retarding the migration of radionuclides by diffusion into the rock matrix. Most conventional methods for the physical characterization of rocks give only bulk information. The combination of mercury po-rosimetry and computer tomography can give 3-D data on mineral-specific porosity distributions with additional pore size information. Additionally, limits for mineral-specific internal surface areas can be estimated, which is essential for the assessment of water-rock interaction and reactive interaction with radionuclides (sorption). Results of measurements on granitic rock (granodiorite) from the Baltic shield are discussed and integrated with results by complementary methods.
Matrix Diffusion of Some Alkali- and Alkaline Earth-Metals in
Granitic Rock
Authors: Johansson H. , Byegård J. , Skarnemark G. , Skålberg M. 
Published: September 2012

ABSTRACTStatic through-diffusion experiments were performed to study the diffusion
of alkali- and alkaline earth-metals in fine-grained granite and
medium-grained Äspö-diorite. Tritiated water was used as an inert reference
tracer. Radionuclides of the alkali- and alkaline earth-metals (mono- and
divalent elements which are not influenced by hydrolysis in the pH-range
studied) were used as tracers, i.e.
22Na+, 45Ca2+ and Sr The
effective diffusivity and the rock capacity factor were calculated by
fitting the breakthrough curve to the one-dimensional solution of the
diffusion equation. Sorption coefficients, Kd, that were derived
from the rock capacity factor (diffusion experiments) were compared with
Kd determined in batch experiments using crushed material of
different size fractions.The results show that the tracers were retarded in the same order as was
expected from the measured batch Kd. Furthermore, the largest
size fraction was the most representative when comparing batch Kd
with Kd evaluated from the diffusion experiments. The observed effective
diffusivities tended to decrease with increasing cell lengths, indicating
that the “transport” porosity decreases with increasing sample lengths used
in the diffusion experiments.
Behaviour of Plutonium Interacting with Bentonite and Sulfate-Reducing Anaerobic Bacteria
Authors: Kudo A. , Zheng J. , Cayer I. , Fujikawa Y. , Asano H. , Arai K. , Yoshikawa H. , Ito M. 
Published: September 2012

ABSTRACTThe interactions between sulfate reducing anaerobic bacteria and plutonium, with or without bentonite present, were investigated using distribution coefficients {Kd (ml/g)} as an index of the radionuclide behaviour. Plutonium Kds for living bacteria varied within a large range, from 1,804 to 112,952, depending on the pH, while the Kds ranged from 1,180 to 5,931 for dead bacteria. In general, living bacteria had higher plutonium Kds than dead bacteria. Furthermore, the higher Kd values of 39,677 to 106,915 for living bacteria were obtained for a pH range between 6.83 and 8.25, while no visible pH effect was observed for dead bacteria. These Kd values were obtained using tracers for both236Pu and239Pu, which can check the experimental procedures and mass balance.Another comparison was conducted for plutonium Kd values of mixtures of living bacteria with bentonite and sterilized bacteria with bentonite. The range of Kd values for the non-sterilized bacteria with bentonite were 1,194 to 83,648 while Kd values for the sterilized bacteria with bentonite were from 624 to 17,236. Again, the Kd values for the living bacteria with bentonite were higher than those of sterilized bacteria with bentonite. In other words, the presence of living anaerobic bacteria with bentonite increased, by roughly 50 times, the Kd values of239Pu when compared to the mixture of dead bacteria with bentonite. The plutonium Kd values for bentonite alone, both non-sterilized and sterilized, were within a constant range of around 10,000 even though some of the data are not yet available.The bentonite used for this experiment was a product of Japan and the sulfate reducing anaerobic bacteria was previously used for the treatment of a pulp and paper wastewater. The results indicate that the effects of anaerobic bacteria within the engineered barrier system (in this case bentonite) will play a significant role in the behaviour of plutonium in geologic repositories.
Effect of Dry Density on Activation Energy for Diffusion of
Strontium in Compacted Sodium Montmorillonite
Authors: Kozaki Tamotsu , Sato Hiroki , Fujishima Atsushi , Saito Nobuhiko , Sato Seichi , Ohashi Hiroshi 
Published: September 2012

ABSTRACTFor performance assessments of geological disposal of high-level radioactive
waste, activation energies for the diffusion of strontium ions and the basal
spacings of compacted sodium montmorillonite in the water-saturated state
were determined.Basal spacings determined by XRD indicated changes in the interlamellar
space from a three-water layer hydrate state to a two-water layer hydrate
state as the dry density of the montmorillonite increased from 1.0 to 1.8 Mg
m-3. Activation energies from 17.3 to 30.8 kJ mol-1
for the apparent diffusion coefficients of strontium ions were obtained. The
lower activation energies than for diffusion of strontium ions in free water
were determined for montmorillonite specimens of lower dry density (1.2 Mg
m-3 and below), while the higher activation energies were at
higher dry densities (1.4 Mg m-3 and above).These findings cannot be explained by changes in only the geometric
parameters, which the pore water diffusion model is based upon. Possible
explanations for the dry density dependence of the activation energy are the
changes of the temperature dependence of the distribution coefficients
and/or of the diffusion process with increasing dry density
Estimation of the Radionuclide Transport by Applying the Mean,
the Standard Deviation and the Skewness of Permeability
Authors: Niibori Y. , Tochiyama O. , Chida T. 
Published: September 2012

ABSTRACTA new method for estimating the mass transport by using the stochastic
values (the arithmetic mean, the standard deviation and the skewness) of
permeability is presented. Generally, detail of permeability distribution
cannot be obtained except for moments of the distribution. Also, measurement
results of permeability for the rock matrix including cracks or fast
flowpaths do not always follow the log-normal distribution frequently
applied. In such a situation, we must evaluate the characteristic
permeabilities for the whole or some regions of the disposal site including
the accessible environment.The authors have investigated the characteristic permeability on the basis
of some probability density functions of permeability, applying the Monte
Carlo method and FEM. It was found that its value does not depend on type of
probability density function of permeability, but on the arithmetic mean,
the standard deviation and the skewness of permeability [1].This paper describes the use of the stochastic values of permeability for
estimating the rate of radioactivity release to the accessible environment,
applying the advection-dispersion model to two-dimensional, heterogeneous
media. When a discrete probability density function (referred to as ‘the
Bernoulli trials’) and the lognormal distribution have common values for the
arithmetic mean, the standard deviation and the skewness of permeability,
the calculated transport rates (described as the pseudo impulse responses)
show good agreements for Peclet number around 10 and the
dimensionless standard deviation around 1. Further, it is
found that the transport rates apparently depends not only on the arithmetic
mean and the standard deviation, but also on the skewness of permeability.
When the value of skewness dose not follow the lognormal distribution which
has only two independent parameters (the mean and the standard deviation),
we can replicate the three moments estimated from an observed distribution
of permeability, by using the Bernoulli trials having three independent
parameters.
Near-Field Chemical Composition of Porewaters in a Near-Surface
Low-Level Radioactive Waste Vault
Authors: Caron F. , Haas M. K. , Manni G. , Torok J. 
Published: September 2012

ABSTRACTA long-term waste degradation experiment has been performed with actual
low-level radioactive wastes (LLRW) at the Chalk River Laboratories (CRL),
to support the licensing and modelling efforts for near-surface disposal.
The wastes consist of paper, mop heads, paper towels, used clothing, etc.
The wastes were compacted into bales and sealed into separate steel
containers, which were connected to leachate collection systems for
sampling. The leachates collected had a composition typical of landfill
leachates. The major inorganic ions were Na, Ca, Cl, and Fe, and the ionic
strength was ∼0.05 M. The relative distribution of inorganic ions in the
leachates was remarkably similar between bales. Volatile fatty acids (VFA)
were the major species of dissolved organic carbon (DOC, total DOC up to
7000 mg/L). A typical composition of leachates is proposed, which can be
used in geochemical and source term modelling.
Direct Characterization of Transport Parameters in Near-Field
and Engineered Backfill/Invert Materials
Authors: Conca J. L. , Robinson B. A. , Triay I. R. , Bussod G. Y. 
Published: September 2012

ABSTRACTPerformance assessment of a potential repository at Yucca Mountain includes
flow and transport modeling of the unsaturated zone as the critical
predictive component, and involves a series of model calculations that
provide predictions of the migration of important radionuclides in the
inventory to the water table. The modeling requires the relevant properties
of both the natural environment and the engineered systems. The Unsaturated
Flow Apparatus, UFA, was used to directly measure the unsaturated and
saturated transport properties of whole rock tuff cores and candidate
barrier materials to provide real input parameters to the models. These
properties included hydraulic conductivity, matric potential, air
permeability, and diffusion coefficient, all of which are strong functions
of the volumetric water content. Results show that for all recharges above
0.1 mm/yr, fractures will be partially saturated and conducting at that
recharge rate. Whenever the thermal conditions relax enough to allow
rewetting of the host rock, there will be dripping from the drift ceiling.
Unsaturated transport of colloids through fractured cores of Topopah Spring
and Prow Pass tuffs was also investigated and found to depend primarily upon
colloid charge, and not size, for the rock cores investigated.
Experimental Study of Colloid Filtration by Compacted
Bentonite
Authors: Kurosawa Susumu , Yui Mikazu , Yoshikawa Hideki 
Published: September 2012

ABSTRACTIn this study, the transport behavior of colloids through compacted
bentonite and sand-bentonite mixtures was investigated. Colloidal gold was
used to simulate mobile colloids because it was well characterized and its
dispersivity was controlled. The bentonite used was a sodium bentonite. The
sand-bentonite mixtures were prepared by mixing up to 50wt.% silica sand
with the bentonite. The bentonite and the sand-bentonite mixtures were
compacted to dry densities of 1000 and 1800 kg/m3 and then
saturated with distilled water. The sand-bentonite mixture was also
saturated with synthetic sea-water. Column experiments were performed to
investigate colloidal transport. Further, colloidal particles stabilities in
high ionic strength water such as bentonite porewater or saline groundwater
were interpreted based on the repulsion potential from the double layer
force and the attraction potential from the van der Waals force.The results indicated that the colloidal particles were effectively filtered
by both the compacted bentonite and the sand-bentonite mixtures. This study
indicated that the effect of colloids on radionuclide transport in compacted
bentonite is negligible for the safety assessment of high level radioactive
waste (HLW) disposal.
Experimental Study on Self-Healing of Bentonite / Sand Mixtures
and its Impact on Hydraulic Permeability
Authors: Hokari Toshiyuki , Okihara Mitsunobu , Ishii Takashi , Kojima Keiji 
Published: September 2012

ABSTRACTThe effects of gas permeation on the hydraulic permeability of
bentonite/sand mixtures were studied experimentally by conducting
permeability tests with various fluids and by microscopic observations. In
these tests, hydraulic permeabilities were measured before and after helium
gas was applied to permeate the mixtures.Although gas formed preferential migration paths through the mixtures, the
imperviousness of the bentonite/sand mixtures to the tested fluids never
deteriorated because the paths became filled by swelling bentonite on
re-saturation.
Comparative Tests for Evaluating Permeability Changes of a
Compacted Bentonite/Sand Mixture During Shear
Authors: Esaki T. , Zhang M. , Mitani Y. 
Published: September 2012

ABSTRACTA compacted mixture of Kunigeru VI bentonite and D-sand is being considered
for use as an engineered barrier in low-level radioactive waste disposal
facilities in Japan. An important issue is the maintenance of the
retardation property of the mixture during shear that might be induced in
such barriers by earthquakes and/or gradual tectonic deformations occurring
over the design life of the facility. To investigate this issue, comparative
tests on a bentonite-sand mixture and kaolin-sand mixture were conducted by
means of a recently-developed coupled shear and permeability testing
apparatus under temperature controlled condition. In addition to
permeability, the specific storage of bentonite-sand specimen during shear
is also systematically evaluated with the new analytical theory for the
constant flow permeability test. The present study reveals that 1)
temperature control is preferred for measuring the permeability of
extremely-low permeability materials with the constant-flow pump method; 2)
both the permeability and specific storage of the mixture of Kunigeru VI
bentonite and D-sand (bentonite to sand weight ratio = 15: 85) were not
significantly influenced by shear strains up to 3% whereas the permeability
of the kaolin-sand mixture increased almost linearly with the increment of
shear strain; 3) the swelling of bentonite in the mixture under low
confining stress decreases both the permeability and specific storage of
bentonite-sand mixture. This feature of bentonite helps maintain the
long-term retardation property of the mixture; and 4) the constant flow
permeability test method, with the newly derived theoretical analysis,
promises to become a very effective means of investigating, rapidly and
systematically, the permeability and specific storage of extremely-low
permeability materials with relatively-low (i.e. close to in situ) hydraulic
gradients. This is necessary for the design and long-term performance
assessment of engineered barriers.