bluuebunny/crossref_metadata_2025_split huggingface dataset:
Depleted Uranium Oxides and Silicates as Spent Nuclear Fuel
Waste Package Fill Materials
Authors: Forsberg C. W. 
Published: September 2012

ABSTRACTA new repository waste package (WP) concept for spent nuclear fuel (SNF) is
being investigated. The WP uses depleted uranium (DU) to improve performance
and reduce the uncertainties of geological disposal of SNF. The WP would be
loaded with SNF. Void spaces would then be filled with DU (∼0.2 wt %
235U) dioxide (UO2) or DU silicate-glass beads.Fission products and actinides can not escape the SNF UO2
crystals until the UO2 dissolves or is transformed into other
chemical species. After WP failure, the DU fill material slows dissolution
by three mechanisms: (1) saturation of WP groundwater with DU and
suppression of SNF dissolution, (2) maintenance of chemically reducing
conditions in the WP that minimize SNF solubility by sacrificial oxidation
of DU from the +4 valence state, and (3) evolution of DU to lower-density
hydrated uranium silicates. The fill expansion minimizes water flow in the
degraded WP. The DU also isotopically exchanges with SNF uranium as the SNF
degrades to reduce long-term nuclear-criticality concerns.
Study on the Formation of Lanthanum Phosphate for Highly
Efficient Incorporation of Actinides from Radioactive Liquid
Waste
Authors: Sasoh Michitaka , Miyamoto Shinya , Toyohara Masumitu , Wada Mikio 
Published: September 2012

ABSTRACTWe have studied a co-precipitation method to remove actinides from
radioactive liquid waste. Lanthanum phosphate was selected as a
co-precipitation material because actinides and lanthanides are among the
homology series in the periodic table. In this report, the conditions, under
which the lanthanum compound is precipitated was looked at, as well as, ways
to widen the pH range in which the precipitation occurrs in sodium nitrate
solution. The properties of the resulting precipitates were also
investigated. Further, we investigated the incorporation ratio of amerícium
(decontamination factor), one of the actinides, into the precipitate from
sodium nitrate solution. Lanthanum phosphate was found to be more effective
compared to ferric compounds as the co-precipitation material to remove
amerícium. The incorporation conditions for strontium using lanthanum
phosphate were also investigated. The removal of strontium, by this method,
was more effective when the pH is above 7.0.
Formation of Paramagnetic Defects in Oxide Glasses During the
Bombardment of Their Surface with Charged Particles
Authors: Bogomolova L. D. , Stef Ano Vsky S. V. , Teplyakov Y. G. , Dmitriev S. A. 
Published: September 2012

ABSTRACTHeavy-ion bombardment of a glass surface is a conventional laboratory
technique for producing damage of interest for radioactive waste
encapsulation. At energy of order 100 keV such a bombardment simulates the
damage produced by α-recoil nuclei and fission fragments resulting from the
nuclear decay. The damage region is 100–500 nm depending on conditions of
the bombardment.In the present work some results of EPR study of point defects formed in
silicate, borate, borosilicate, phosphate and other oxide glasses irradiated
with different charge particles (C, N, O, Ar. Mn, Cu, Pb) at energy E=150
keV and large total fluence of ions (up to 1017 cm-2)
are reported. Electron paramagnetic resonance (EPR) is a very sensitive
technique which gives an information on the structure of point defects and
their content. It is shown that in some cases (for example, in borate
glasses) the oxygen hole centers similar to ones observed in γ-irradiated
glasses are formed after ion bombardment. However, in the majority of cases
new defects which are not typical of γ-irradiated oxide glasses were found
They were large molecular oxygen ions (O2-O3-O4-) located in the cavities formed under ion bombardment in the
near surface layer of glass. It should be noted that the relative content of
these defects is of the order of several tens per 1000 incident ions. This
content decreases with increasing fluence and atomic mass of incident ions.
It indicates indirectly that point defects are clustered when the damage of
the near surface layer becomes strong. The formation of gaseous oxygen is
possible in cavities of the damage surface layer.It was found that some elements (for example C, N and transition metals)
form chemical compounds with oxygen. The migration of alkali ions promotes
the formation of such compounds since the chemical compounds were detected
by means EPR in glasses rich in alkali oxides.
Numerical Predictions of Dry Oxidation of Iron and Low-Carbon
Steel at Moderately Elevated Temperatures
Authors: Henshall G. A. 
Published: September 2012

ABSTRACTWrought and cast low-carbon steel are candidate materials for the thick
(e.g. 10 cm) outer barrier of nuclear waste packages being considered for
use in the potential geological repository at Yucca Mountain. Dry oxidation
is one potential degradation mode for these materials at the moderately
elevated temperatures expected at the container surface, e.g. 323–533 K
(50–260 °C). Therefore, numerical predictions of dry oxidation damage have
been made based on experimental data for iron and low-carbon steel and the
theory of parabolic oxidation. A numerical approach employing the Forward
Euler method has been implemented to integrate the parabolic rate law for
arbitrary, complex temperature histories. Assuming growth of a defect-free,
adherent oxide, the surface penetration of a low-carbon steel barrier
following 5000 years of exposure to a severe, but repository-relevant,
temperature history is predicted to be only about 0.127 mm, less than 0.13%
of the expected container thickness of 10 cm. Allowing the oxide to spall
upon reaching a critical thickness increases the predicted metal penetration
values, but degradation is still computed to be negligible. Based on these
physically-based model calculations, dry oxidation is not expected to
significantly degrade the performance of thick, corrosion allowance barriers
constructed of low-carbon steel.
Development of Mathematical Models for Long-Term Prediction of
Corrosion Behaviour of Carbon Steel Overpacks for Radioactive Waste
Disposal
Authors: Hoch A. R. , Honda A. , Porter F. M. , Sharland S. M. , Taniguchi N. 
Published: September 2012

ABSTRACTMathematical models to enable long-term prediction of the corrosion
behaviour of carbon steel overpacks for radioactive waste have been
developed. An existing model of the growth of pits, implemented in the CAMLE
software, has been extended and used to investigate the sensitivity of the
predictions to input parameters, including cathodic reaction kinetics and
the relative position of the anode and cathode. Predictions have also been
made of the aeration period of the repository, during which localised
corrosion is possible.
Spectroscopic Investigation of Actinide Speciation in
Concentrated Chloride Solution
Authors: Runde W. , Neu M. P. , Conradson S. D. , Clark D. L. , Palmer P. D. , Reilly S. D. , Scott B. L. , Tait C. D. 
Published: September 2012

ABSTRACTActinide solubilities in highly concentrated chloride solutions are about
one order of magnitude higher than in similar inert electrolyte
(NaClO4) solutions. This increased solubility is due to
interactions between actinide and chloride ions. Contradictory results exist
regarding the interaction mechanism between actinide and chloride ions.
Specifically, both inner-sphere complex formation and ion pair association
have been implicated in the interpretation of spectrophotometric and
extraction data. To address this controversy, we investigated the
interaction between actinide ions in the (III), (IV), (V) and (VI) oxidation
states and chloride ions using a multi-method approach. Spectroscopie
techniques (TRLFS, Raman, UV-Vis absorption, EXAFS) were used to distinguish
between changes in the inner coordination sphere of the actinide ion and
effects of ion pairing. X-ray absorption spectroscopy and single crystal
X-ray diffraction were used to determine structural details of the actinide
chloro complexes formed in solution and solid states.
Retrograde Solubilities of Source Term Phases
Authors: Murphy William M. 
Published: September 2012

ABSTRACTNatural analog, experimental, and thermodynamic studies indicate that the
properties of secondary uranyl minerals are likely to control the source
term for U and other radioéléments incorporated in these phases in the
proposed Yucca Mountain repository. Thermodynamic calculations using data
from the 1992 NEA data base indicate an increase in the equilibrium constant
for schoepite dissolution from 103.1 to 104.8 with
decreasing temperature from 100° to 25°C, i.e., retrograde solubility.
Enthalpies for mineral transformation reactions that consume protons and
release cations are typically negative, suggesting that solubilities of
other uranyl phases such as uranophane increase more than that of schoepite
with decreasing temperature. Solubilities of mineral phases associated with
spent nuclear fuel will be initially relatively low under the elevated
repository temperature regime. As the temperature of the repository
decreases due to radioactive decay and heat dissipation, source term mineral
solubilities increase. The rate of release of U and other species is
controlled by a series of processes: transport of oxidants and flux of
water; oxidative dissolution of spent fuel; uranyl mineral precipitation;
uranyl mineral dissolution or transformation; and radionuclide transport.
Decreasing diffusion and reaction rates and increasing uranyl mineral
solubilities with decreasing temperature may lead to a change with time from
solubility to transport or reaction rate as a source term controlling
mechanism. Preservation of large quantities of uranyl minerals formed by
oxidation of uraninite and radiometrie ages of secondary uranophane at the
natural analog site at Peña Blanca indicate that oxidative alteration of
uraninite was fast relative to transport of U away from the deposit. The
successive formation of schoepite and uranophane in natural settings where
uraninite has been oxidized may represent a paragenesis reflecting
increasing temperature or increasing incorporation of environmental
components. In contrast, diminishing temperature conditions in a repository
source area could lead to the reverse sequence of mineral formation.
The Effects of the Chemical and Radiolytic Degradation of
Asphalt on Plutonium Solubility
Authors: Greenfield B. F. , Ito M. , Spindler M. W. , Williams S. J. , Yui M. 
Published: September 2012

ABSTRACTThe influence of alkaline degradation or radiolytic degradation of asphalt
on plutonium solubility has been investigated. Asphalt has been contacted
with water, sodium hydroxide solution or concrete leachate at 80°C for
periods of up to approximately 2 years. Sodium nitrate was also present in
some of the experiments. Plutonium solubilities were measured at pH 12 in
the leachates and found to be less than 10-8 mol dm-3
for most degradations. Relatively low levels of Total Organic Carbon were
measured in the leachates. Alpha radiolysis of asphalt in the presence of
concrete and water has also been studied. Samples of asphalt were
encapsulated in concrete after coating with the
238PuO2, crushed and leached at room temperature.
The solubility of plutonium was measured in samples of the leachates after
approximately 90 days and 180 days had elapsed. The results showed that the
solubility of plutonium in the α-radiolysis leachates remained low and was
in the range 2 × 10-11 to 8 × 10-9 mol
dm-3. A consideration of these results, and data published
elsewhere, suggests that chemical and radiolytic attack on asphalt or
bitumen under anaerobic, alkaline conditions typical of a deep cementitious
repository is unlikely to generate complexants for plutonium which are
effective at high pH. Any enhancement of plutonium solubility is likely to
be less significant than that arising from the degradation of some other
organic materials.
Characterization of Th Carbonate Solutions Using XAS and
Implications for Thermodynamic Modeling
Authors: Hess N. J. , Felmy A. R. , Rai D. , Conradson S. D. 
Published: September 2012

ABSTRACTThe chemical behavior of actinide elements in tank solutions, in soil, and
in groundwater is dependent upon the chemical species that form when aqueous
solutions come in contact with the actinide compounds. In particular the
chemical speciation of the reduced actinide oxidation states (III and IV)
are important, for example, to DOE waste tank processing and, more
generally, to nuclear waste disposal issues. Predicting the solubility of
the actinides in these solutions requires identification of the strong
aqueous complexes, such as carbonates and organic chelating agents, that can
form in aqueous solution.Previous speciation work has often relied on indirect techniques such as
potentiometric titrations or solubility measurements. Recent XAS experiments
determine directly the speciation of the Th carbonato species of seven
solutions under a range of carbonate concentrations and pH conditions. The
presence of the pentacarbonato complex is confirmed and the complex's
stability at low carbonate concentrations is determined. These experimental
results support a proposed thermodynamic model that describes the solubility
of Th(IV) hydrous oxide in the aqueous Na+-HCO3--CO32--OH--ClO4--H2O system extending to high concentrations at 25°C.
This model is relatively simple in that only two aqueous species are
included Th(OH)3CO3- and Th(CO3)56-.
The Effect of Mineral Variability on the Solubility of Some
Actinides: an Uncertainty Analysis
Authors: Ekberg Christian , Emrén Allan T. , Samuelsson Anders 
Published: September 2012

ABSTRACTThe use of computer simulations in the performance assessment for a
repository for spent nuclear fuel, are in many cases the only method to get
information on how the rock-repository system will work. One important
factor is the solubility of the elements released if the repository is
breached. This solubility may be determined experimentally or simulated.
Ifit is simulated, several factors such as thermodynamical uncertainties
will affect the reliability of the results. If these uncertainties are
assumed to be small, the composition of the water used in the calculations
may play a major part in the uncertainties in solubility. The water
composition, in tum, is either determined experimentally or calculated
through water-rock interactions. Thus, if the mineral composition of the
rock is known, it is possible to foresee the water composition. However, in
most cases a determination of the rock composition is made from drilling
cores and is thus quite uncertain. Therefore, if solubility calculations are
to be based on water properties calculated from rock-water interactions
another uncertainty is introduced. This paper is focused on uncertainty and
sensitivity analysis of rock-water interaction simulations and the
uncertainties thus obtained are propagated through a program making
uncertainty and sensitivity analysis of the solubility calculations. In both
cases the latin hypercube sampling technique have been used. The results
show that the solubilities are in most cases log normal distributed while
the different elements in the simulated groundwater in some cases diverge
significantly from such a distribution. The numerical results are comforting
in that the uncertainty intervals of the solubilities are rather small, i.e.
up to 30%.
The Use of Laboratory Adsorption Data and Models to Predict Radionuclide Releases from a Geological Repository: a Brief History
Authors: Langmuir Donald 
Published: September 2012

ABSTRACTRadionuclide (RN) adsorption has long been recognized as important to assure the isolation of nuclear wastes in a geological repository [1]. Laboratory measured RN adsorption data have generally been expressed as distribution coefficient (Kd) values or adsorption isotherms. The proper application of these models is to site conditions nearly identical to those used in the laboratory adsorption experiments. This has required that multiple Kd's and isotherms be determined in a wide range of experiments designed to bracket expected repository conditions.The surface complexation (SC) adsorption models were introduced in the late 1970's. The best known of these models incorporate electrical double layer (EDL) theory [2]. Their use requires that the water chemistry and surface properties of adsorbing rocks and minerals be fully characterized. Adsorption is then studied as reactions involving specific aqueous RN species (often complexes) and specific surface sites. Because the SC models are relatively mechanistic, they may allow extrapolation of adsorption results to repository conditions that lie outside the limited experimental range used to parameterize a given model. Turner [3] has shown that the diffuse layer model (the simplest SC model) fits a wide range of RN adsorption data as well as the more complex models. Others have suggested ways to generalize and estimate SC model parameters for a variety of minerals, rocks and engineered materials (cf. [4,5,6,7,8,9,10,11,12]. Degueldre and Werlni [12] and Degueldre et al. [13] have proposed a simplified SC model for RN adsorption that avoids EDL theory, in which the adsorption of RN species is estimated from linear free energy relationships.It is appropriate to ask how accurately RN adsorption behavior must be known or understood for total system performance analysis (TSPA). In most geological settings now being considered for repository development globally, it may suffice to select bounding Kdvalues for the different rock types (cf. [14,15]). Use of the SC models to describe RN adsorption can provide us with increased confidence that minimum Kd's and the distribution of Kdvalues we might propose for TSPA are in fact conservative.
Influence of Carbonate Ions on Europium Sorption onto Iron-Oxides
Authors: Fujita T. , Tsukamoto M. 
Published: September 2012

ABSTRACTThe sorption behavior of europium onto two iron-oxides, goethite and magnetite, focused on the effect of carbonate species concentration was investigated in 0.01 M NaClO4solution by the batch method over a pH range of 4 to 11. It was found that sorption of europium was enhanced in the higher concentration solution of carbonate species for both materials. The zeta-potential of goethite in the solutions including sodium bicarbonate was also measured to estimate the effect of sorbed carbonate species. Our experimental results and model calculation suggest that the production of surface carboxylic group FeOCOO by the sorption of carbonate species lowered the zeta-potential and enhanced europium sorption.
Liquidus Temperature Model for Hanford High-Level Waste Glasses
with High Concentrations of Zirconia
Authors: Crum J. V. , Schweiger M. J. , Hrma P. , Vienna J. D. 
Published: September 2012

ABSTRACTA study was conducted on glasses based on a simulated transuranic waste with
high concentrations of ZrO2and Bi2O3 to
determine the compositional dependence of primary crystalline phases and
liquidus temperature (TL). Starting from a baseline composition, glasses were formulated by
changing mass fractions of Al2O3,
B2O3, Bi2O3, CeO2,
Li2O, Na2O, P2O5,
SiO2, and ZrO2, one at a time, while keeping the
remaining components in the same relative proportions as in the baseline
glass. Liquidus temperature was measured by heat treating glass samples for
24 h in a uniform temperature furnace. The primary crystalline phase in the
baseline glass and the majority of the glasses was zircon
(ZrSiO4). A change in the concentration of certain components
(Al2O3, ZrO2, Li2O,
B2O3 and SiO2) changed the primary phase
to baddeleyite (ZrO2), while cerium oxide (CeO2)
precipitated from glasses with more than 3 wt% CeO2. Zircon
TL was strongly increased by Al2O3,
Zrb2 and CeO2, and slightly by
P2O5 and SiO2; decreased strongly by
Li2O and Na2O and moderately by
B2O3. A first-order model was constructed for
TL as a function of composition for zircon primary crystalline phase
glass.
Uranyl Sorption Onto Alumina
Authors: Jacobsson Anna-Maria M. , Rundberg Robert S. 
Published: September 2012

ABSTRACTThe mechanism for the adsorption of uranyl onto alumina from aqueous
solution was studied experimentally and the data were modeled using a triple
layer surface complexation model. The experiments were carried out at low
uranium concentrations (9×10-11 - 5×10-8M) in a
CO2 free environment at varying electrolyte concentrations
(0.01 – 1 M) and pH (4.5 – 12). The first and second acid dissociation
constants, pKal and pKa2, of the alumina surface were
determined from potentiometric titrations to be 7.2 ± 0.6 and 11.2 ± 0.4,
respectively. The adsorption of uranium was found to be independent of the
electrolyte concentration. We therefore conclude that the uranium binds as
an inner sphere complex. The results were modeled using the code FITEQL. Two
reactions of uranium with the surface were needed to fit the data, one
forming a uranyl complex with a single surface hydroxyl and the other
forming a bridged or bidentate complex reacting with two surface hydroxyls
of the alumina. There was no evidence from these experiments of site
heterogeneity. The constants used for the reactions were based in part on
predictions made utilizing the Hard Soft Acid Base, HSAB, theory, relating
the surface complexation constants to the hydrolysis of the sorbing metal
ion and the acid dissociation constants of the mineral oxide surface.
Adsorption of Sn(IV) on Goethite in 0.01M NaCl Solution at
Ambient Temperature
Authors: Amaya Takayuki , Suzuki Kazunori , Oda Chie , Yoshdcawa Hideki , Yui Mikazu 
Published: September 2012

ABSTRACTThe adsorption of soluble Sn(TV) species on goethite (FeOOH), a naturally
occurring mineral, was investigated in 0.01 M NaCl solution at ambient
temperature. The sequential spike method was used to obtain the distribution
coefficient (Kd). Kd values of higher than 1×107 ml/g at neutral
pH, and 3×105 ml/g at pH 11 were obtained. It is observed that Kd
values decrease with increasing pH. In the desorption experiment, the
sequential extraction method was applied. The extractants such as 0.1 M
NaOH, Tamm's acid oxalate and Coffin's reagent were used. The result
indicates that the adsorption consists of both reversible and irreversible
reactions, and that the most of fractions in adsorption of Sn on goethite
correspond to the irreversible adsorption or a stable fixation. Moreover, it
is suggested that the reversible adsorption converts to the irreversible
adsorption with time.
Sorption Processes of UO22+Ions onto Zirconium and Thorium Phosphate Surfaces: Thermodynamical and Structural Aspects
Authors: Drol R. , Simoni E. , Cavcllcc R. , Pradin V. , Dcnauwcr Ch. , Ehrhardl J. J. 
Published: September 2012

ABSTRACTMost of the studies on sorption processes take into account only a ihcrmodynamic approach, and only lew studies have paid attention to ihc structural aspect (i.e. structure of ihc postulated surface complex). Experiments were conducted to study UO22+sorption onto zirconium and thorium phosphate surfaces. Moreover, in order to identify the nature of the sorption sites and the structure of the surface complex, various spectroscopie techniques such as EXAFS, XPS and laser induced fluorescence have been used. Two different types of sorption sites on the thorium phosphate but only one on the zirconium phosphate have been detected.