bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability of Mineral Matter in Aqueous Media of the Chernobyl
Unit-4 Shelter: Thermodynamic Evaluation
Authors: Sinitsyn V. A. , Kulik D. A. , Skhodorivski M. , Kurepin V. A. , Abramis A. Y. , Kolyabina I. L. , Shurpach N. A. 
Published: September 2012

ABSTRACTA special geochemical environment exists within the Shelter (”Sarcophagus”)
erected in 1986 over the destroyed Unit-4 of Chernobyl nuclear power plant
(NPP). Based upon the available in situ and compositional
data, thermodynamic models of solid-aqueous interactions were developed to
clarify the leaching behaviour of various materials within the Shelter. The
“Selektor-A” code, based on a convex programming approach to Gibbs free
energy minimization, was used for the calculations. A built-in flexible
hybrid thermodynamic database for the system
Na-K-Ca-Mg-Cl-S-N-H-O-Si-P-Fe-Al-Sr-Cs was extended with the critically
selected and matched parameters for aqueous species and solid phases in the
U-Zr-Si-O-H subsystem, secondary U-minerals, mineral phases of fully
hydrated Portland cements and U-bearing zircons. Modeling results show that
the “Shelter waters” can selectively leach a significant quantity of U and
Si from the fuel-containing masses, while Zr, Fe, Ca, Mg and some other
components are rather insoluble. Serpentinite, assemblages of fully-hydrated
phases of Portland cements, and oxidation products of steel structural
elements are estimated to be sufficiently stable in the aqueous environment
of the Shelter. Our calculations also define some feasible pathways for
secondary mineral formation from evaporation of Shelter water solutions and
interactions between these waters with the mineral matter inside the
Shelter.
Modeling the Migration of 99Sr and 137Cs
in the Subsurface from the Chernobyl NPP Unit-4 Shelter
Authors: Kivva S. L. , Stelya O. B. , Proskura N. I. 
Published: September 2012

ABSTRACTThe Shelter constructed above the destroyed Unit-4 of the Chernobyl NPP
contains 20 MCi of nuclear fuel. More than 1000 m3 of
intermediate-level radioactive water is disposed in its basement. The
purpose of this work was to simulate migration of the radionuclides
90Sr and 137Cs from the Shelter into the subsurface
environment to evaluate their migration rate and migration paths. A
mathematical model accounting for the coupled transport of water and
radionuclides in variably saturated media was used. The lack of suitable
experimental and field studies excluded the possibility of complete
validating the model. Results of the simulations will be useful for future
field studies.
Optimization of Savannah River M-Area Mixed Waste for
Vitrification
Authors: Fu Sabrina S. , Gan Hao , Muller Isabelle S. , Pegg Ian L. , Macedo Pedro B. 
Published: September 2012

ABSTRACTVitrification studies of actual Savannah River M-Area mixed wastes have
shown that the limiting factor for high waste loading of this waste stream
is its chemical durability as defined by the toxicity characteristics
leaching procedure (TCLP). As part of the optimization study of Savannah
River M-Area wastes, a number of additives were examined including
Na2O, Li2O, B2O3,
ZrO2, and TiO2. This paper reports on the effect of
varying the boron to total alkali ratio and on the effect of substitutions
such as ZrO2 for waste and TiO2 for SiO2 on
the chemical durability and processability of M-Area waste glasses.
Solution-Borne Colloids from Drip Tests using actinide-Doped and
Fully-Radioactive Waste Glasses
Authors: Fortner Jeffrey A. , Wolf Stephen F. , Buck Edgar C. , Mertz Carol J. , Bates John K. 
Published: September 2012

ABSTRACTDrip tests designed to replicate the synergistic interactions between waste
glass, repository groundwater, water vapor, and sensitized 304L stainless
steel in the potential Yucca Mountain Repository have been ongoing in our
laboratory for over ten years. Results will be presented from three sets of
these drip tests: two with actinide-doped glasses, and one with a
fully-radioactive glass. Periodic sampling of these tests have revealed
trends in actinide release behavior that are consistent with their
entrainment in colloidal material when as-cast glass is reacted. Results
from vapor hydrated glass show that initially the actinides are completely
dissolved in solution, but as the reaction proceeds, the actinides become
suspended in solution. Sequential filtering and alpha spectroscopy of
colloid-bearing leachate solutions indicate that more than 80% of the
plutonium and americium are bound to particles that are captured by a 0.1 μm
filter, while less than 10% of the neptunium is stopped by a 0.1 μm filter.
Analytical transmission electron microscopy has been used to examine
particles from leachate solutions and to identify several actinide-bearing
phases which are responsible for the majority of actinide release during
glass corrosion.
Waste Glass Analytical Bias Correction Using a Reference
Standard Glass
Authors: Smith Gary L. , Eggett Dennis L. , Smith Harry D. 
Published: September 2012

ABSTRACTAnalytical round robins were established to allow laboratories responsible
for the analysis of (nuclear) wastes glasses to compare their analytical
capabilities and techniques with one another in a non-competitive
atmosphere. In addition the quality of analyses using different analytical
techniques on the same materials could be compared. Analytical Round Robin 7
had two primary objectives: 1) to evaluate the effect of using the same
analytical reference glass as a reference standard for bias correcting
analytical results for all the participating laboratories in making the
analyses; and 2) to discuss the analytical methods and results from the
participating laboratories between the participants for the purpose of
evaluating quality and interlaboratory consistency. This paper will
primarily address the first objective.The purpose of an analytical reference material is to bring the analytical
results from various laboratories into better agreement by providing them a
common reference point No reference glass is likely to be ideal for each
element in the glass being analyzed. Obviously, the closer the reference
material is to the unknown, the more confidence there will be in the results
because less judgement is called for. Use of the reference glass to bias
correct analytical results for a standard set of analyses from several
laboratories provides the data needed to determine the effectiveness of an
Analytical Reference Glass (ARG) in producing interlaboratory agreement.
Concurrently, whether or not the analytical results using ARG-1 are more
valid or systematically biased can be evaluated using standard statistical
methods. The conclusion is that bias correcting with a standard glass such
as ARG-1 for results obtained by the inductively coupled plasma - atomic
emission spectroscopy (ICP-AES) analytical technique produces more accurate
results.
Modelling Glass Dissolution in Clay with Analytic and Stochastic
Methods
Authors: Aertsens Marc 
Published: September 2012

ABSTRACTWe present a stochastic method to model the dissolution of nuclear glass.
Using this method, we solve the diffusion equation in a stochastic way. We
do this by giving a large number of particles Brownian displacements.
Simultaneously, these particles can participate in other processes, like a
chemical reaction or convection.We apply this method to solve the Pescatore model for the dissolution of
nuclear glass in clay. This model combines diffusion of silica in the pore
water of the clay with the glass dissolution rate law proposed by Grambow.
We use the model for fitting the dissolution data of four glasses in clay
slurries (with a high and with a low clay content) and in pure clay. We
present the values of the fitting parameters. The solution of the model,
obtained by the simulation method, agrees with the analytical solution. We
also extend the Pescatore model with a moving boundary, taking into account
the receding of the glass surface by corrosion.
Applicability of
V2O5-P2O5 Glass System for
Low-Temperature Vitrification
Authors: Nishi T. , Noshita K. , Naitoh T. , Namekawa T. , Takahashi K. , Matsuda M. 
Published: September 2012

ABSTRACTThe V2O5-P2O5 glass system (vanadate glass) has been developed to provide
low temperature vitrification of radioactive waste without volatilization of
radionuclides. The dissolution behaviour of vanadate glass was determined
from the results of the MCC-1 static leach test at 70 ‘C using deionized
water, cement-saturated alkaline water, and cement-saturated alkaline water
with 3% NaCl. The solubility of vanadate glass was remarkably reduced by the
addition of Sb2O3to the glass. It was also lowered in
the cement-saturated water due to formation of a precipitation layer.
Although the presence of NaCl in the solution accelerated the dissolution of
vanadate glass, the addition of alkaline earth metal oxide to the glass gave
a dissolution rate three orders lower than non-additive vanadate glass. The
results of leach tests using simulated vitrified waste form containing 5moI%
of Cs2 and SrO showed there was a possibility of fixing Cs and Sr
into the glass structure.
Uranium Speciation in Glass Corrosion Layers: an XAFS Study
Authors: Biwer Bruce M. , Soderholm L. , Greegort R. B. , Lytle F. W. 
Published: September 2012

ABSTRACTUranium L3X-ray absorption data were obtained from two borosilicate glasses, which are considered as models for radioactive wasteforms, both before and after leaching. Surface sensitivity to uranium speciation was attained by a novel application of simultaneous fluorescence and electron-yield detection. Changes in speciation are clearly discernible, from U(VI) in the bulk to (UO2)2+-uranyl in the corrosion layer. The uranium concentrations within the corrosion layer also show variations with leaching times that can be determined from the data.
Colloid Formation During the Interaction of HLW Glass with Interstitial Clay Water
Authors: Wei J. , Van Iseghem P. 
Published: September 2012

ABSTRACTDuring the reaction of HLW glass with interstitial clay water at different temperatures with various ratios of glass surface area to solution volume (SA/V) and durations, Eu released from the glass forms predominantly Eu-humate colloids (organic colloids) by a complexation reaction. The size distribution and stability of Eu-humate colloids have been characterized. It is likely that inorganic colloids which are mainly composed of Si, Al and Ca are generated from the corrosion of waste glass by a nucleation reaction.
Influence of the Degraded Surface Layer on the Long-Term
Behavior of Cement Pastes
Authors: Faucon P. , Jacquinot J. F. , Adenot F. , Virlet J. , Petit J. C. 
Published: September 2012

ABSTRACTLeaching of a cement paste by a demineralized solution results in the
progressive dissolution of the zone in contact with the aggressive solution.
In the long term, this dissolution will determine the kinetics of
degradation of the material. These kinetics will depend principally on the
solubility of calcium in the zone in contact with the aggressive
solution.
Science Underlying Radioactive Waste Management: Status and
Needs-Twenty Years Later
Authors: Roy Rustum 
Published: September 2012

ABSTRACTThe setting of the technical subsystem within the overall
socio-political-economic-technical radwaste system will be described and the
highly interactive nature of the larger setting emphasized. It will be shown
that because of the dominance of the socio-political subsystem, the
importance of the technical subsystem is overshadowed. Moreover the key
issue in the technical subsystem, whether to put more reliance on the
immobilization (via the waste package or engineeered barriers) or the
isolation (via the geology) has stayed tilted toward the latter since 1978,
when we organized the first symposium on radwaste science (at the Materials
Research Society meeting). Now that the isolation strategy is stymied, the
opportunity arises again for the materials community to make a compelling
case for the waste package's true significance.This review is made mainly from the perspective of one laboratory in one
country, the U.S. What is remarkable about the state of research in the
technical subsystem is how little the big picture of the
science or the technology has changed after some
billions spent on R/D. The borosilicate glass (almost unchanged) is still
the establishment's choice of reference waste form for HLW Cost, however, is
finally forcing cement encapsulated forms to be given a second look.
Mineral-modeled ceramics have received a great deal of scientific attention
but remain esoteric to managers. It will be shown that in the author's
opinion an enormous amount of detailed science has been done but most of it
is unlikely to prove to be of any relevance or use. The policy implications
for future R/D are discussed.
PCT Leach Tests of Hot Isostatically Pressed (HIPped) Zeolitic
Concretes
Authors: Siemer D. D. , Roy Delia M. , Grutzeck Michael W. , Gougar M. L. D. , Scheetz Barry E. 
Published: September 2012

ABSTRACTThe logical place for the US Federal government to site a permanent
repository for its massive accumulation of cold-war reprocessing radwaste
would be at its primary cold-war nuclear device testing reservation, the
Nevada Test Site(1). Regardless of whether it eventually chooses
to implement that repository by drilling lateral “drifts” into consolidated
rock (e.g. its proposed Yucca Mountain facility) or by augering
moderately-deep boreholes into unwelded alluvium beds (e.g. the “Greater
Confinement Disposal (GCD) repository implemented at Frenchman Flats in 1984
(2), zeolitic hydroceramic materials would be more stable than
would glasses. The thermodynamic rationale for this is that in such regions,
soil solutions and soil gasses both tend to “weather” buried natural glasses
to zeolitic materials(3). It has also been demonstrated that the
same type of phases form when properly designed cementitious “grouts” are
cured under mild hydrothermal conditions(4,5) - precisely those
conditions assumed by DOE's repository modelers for “failed” (i.e. flooded)
repositories and under which radwaste-type glasses rapidly decompose to form
crystalline zeolitic phases(6,7).
Evaluation of Microbially Influenced Degradation as a Method for the Decontamination of Radio Actively Contaminated Concrete
Authors: Rogers R. D. , Hamilton M. A. , Nelson L. O. , Benson J. , Green M. 
Published: September 2012

ABSTRACTBecause there are literally square kilometers of radioactively contaminated concrete surfaces within the U.S. Department of Energy (DOE) complex, the task (both scope and cost) of decontamination is staggering. Complex-wide cleanup using conventional methodology does not appear to be feasible for every facility because of prioritization, cost, and manual effort required.We are investigating the feasibility of using microbially influenced degradation (MID) of concrete as a unique, innovative approach for the decontamination of concrete. Currently, work is being conducted to determine the practicality and cost effectiveness of using this environmentally acceptable method for decontamination of large surface concrete structures. Under laboratory conditions, the biodecontamination process has successfully been used to remove 2 mm of the surface of concrete slabs. Subsequently, initial field application data from an ongoing pilot-scale demonstration have shown that an average of 2 mm of surface can be removed from meter-square areas of contaminated concrete. The cost for the process has been estimated as $1.29/m2. Methodologies for field application of the process are being developed and will be tested. This paper provides information on the MID process, laboratory evaluation of its use for decontamination, and results from the pilot field application.
Plutonium and Neptunium Incorporation in Zirconolite
Authors: Begg B. D. , Vance E. R. , Day R.A , Hambley M. , Conradson S. D. 
Published: September 2012

ABSTRACTThe incorporation of Pu and Np in zirconolite (CaZrTi2O7) has been investigated over a range of redox conditions. Zirconolite formulations designed to favour either trivalent or tetravalent Pu and Np were prepared by limiting the amount of charge compensating additives available to maintain electroneutrality. From near-edge X-ray absorption spectroscopy the Pu valence state was found to vary with the processing atmosphere, from completely tetravalent when fired in air, and located on either the Ca or Zr sites, to trivalent, when substituted on the Ca site after annealing in 3.5% H2/N2. Np was predominantly tetravalent over the range of redox conditions examined and was readily incorporated on either of zirconolite's Ca or Zr sites. The charge compensation mechanisms at work in different zirconolites are also discussed.
Synroc Derivatives for the Hanford Waste Remediation
Task
Authors: Vance E. R. , Hart K. P. , Day R. A. , Carter M. L. , Hambley M. , Blackford M. G. , Begg B. D. 
Published: September 2012

ABSTRACTThree wt% each of Cs and Tc were mixed with the standard Synroc precursor
and the ceramic was formed by hot-pressing. Attempts were made to
incorporate the Tc as either metal or Tc 4+, using different
redox conditions in processing. Volatile losses of Tc during calcination
were < 0.1% in all cases. Short-term Tc leach rates when the Tc was
present as a metal alloy were in the order of 10−4 g/m /d at 90°C
with frequently changed water, and decreased with increasing leaching time.
The valence of the Tc was monitored by X-ray absorption spectroscopy at the
drying and calcination stages of the production. The general viability of
Synroc/glass composites for immobilising the Hanford HLW sludges is further
demonstrated by using further refinements of additive schemes for the
inactive “All-blend” formulation and initial studies using the U-containing
“All-blend” waste formulation.
Fundamental Chemistry and Materials Science of Americium in
Selected Immobilization Glasses
Authors: Haire R. G. , Stump N. A. 
Published: September 2012

ABSTRACTWe have pursued some of the fundamental chemistry and materials science of
americium in three glass matrices, two being high-temperature (850° and
1400°C melting points) silicate-based glasses and the third a sol-gel glass.
Optical spectroscopy was the principal investigating tool in the studies.
One aspect of this work was to determine the oxidation state exhibited by
americium in these matrices, as well as factors that control and/or may
alter this state. We have noted a correlation between the oxidation state of
the f-elements in the two high-temperature glasses with their
high-temperature oxide chemistries. One exception was americium: although
americium dioxide is the stable oxide encountered in air, when this dioxide
was incorporated into the high-temperature glasses, only trivalent americium
was found in the products. When trivalent americium was used to prepare the
sol-gel glasses at ambient temperature, and after these products were heated
in air to 800°C, again only trivalent americium was observed. Potential
explanations for the unexpected behavior of americium is offered in the
context of its basic chemistry. Experimental spectra, spectroscopie
assignments and other pertinent data obtained in the studies are
discussed.
Salt-Occluded Zeolite Waste Forms: Crystal Structures and
Transformability
Authors: Richardson J. W. 
Published: September 2012

ABSTRACTNeutron diffraction studies of salt-occluded zeolite and zeolite/glass
composite samples, simulating nuclear waste forms loaded with fission
products, have revealed complex structures, with cations assuming the dual
roles of charge compensation and occlusion (cluster formation). These
clusters roughly fill the 6–8 Å diameter pores of the zeolites. Samples are
prepared by equilibrating zeolite-A with complex molten Li, K, Cs, Sr, Ba, Y
chloride salts, with compositions representative of anticipated waste
systems. Samples prepared using zeolite 4A (which contains exclusively
sodium cations) as starting material are observed to transform to sodalite,
a denser alumi-nosilicate framework structure, while those prepared using
zeolite 5A (sodium and calcium ions) more readily retain the zeolite-A
structure. Because the sodalite framework pores are much smaller than those
of zeolite-A, clusters are smaller and more rigorously confined, with a
correspondingly lower capacity for waste containment. Details of the
sodalite structures resulting from transformation of zeolite-A depend upon
the precise composition of the original mixture. The enhanced resistance of
salt-occluded zeolites prepared from zeolite 5A to sodalite transformation
is thought to be related to differences in the complex chloride clusters
present in these zeolite mixtures. Data relating processing conditions to
resulting zeolite composition and structure can be used in the selection of
processing parameters which lead to optimal waste forms.
Comparison of Sodium Zirconium Phosphate-Structured HLW Forms
and Synroc for High-Level Nuclear Waste Immobilization
Authors: Zyryanov V. N. , Vance E. R. 
Published: September 2012

ABSTRACTThe incorporation of (a) Cs and Sr as; (b) simulated actinides, and (c)
simulated Purex waste in sodium zirconium phosphate (NZP) has been studied.
The samples were prepared by sintering, by hot pressing and by hot isostatic
pressing in metal bellows containers. The short-term chemical durability of
the phosphate-based material containing Purex waste was within an order of
magnitude ofthat for Synroc-C, as measured by 7-day MCC-1 tests at 90°C. The
dissolution behaviour showed evidence of re-precipitation phenomena, even
after times as short as 28 days. Potential for improvement of NZP-based
ceramics for HLW management is discussed.
Synthetic Mineral-Like Matrices for HLLW Solidification:
Preparation by Induction Melter with a Cold Crucible (CCIM)
Authors: Smelova T. V. , Krylova N. V. , Shestoperov I. N. 
Published: September 2012

ABSTRACTA technique for solidification of high-level liquid wastes (HLLW) to obtain
mineral-like forms through the use of water-cooled melters with direct
induction heating of a melt (CCIM) has been developed at the State
Scientific Center of the Russian Federation VNIINM (SSC RF VNIINM).Mineral-like materials of different classes such as pyroxenes,
pyrosilicates, garnets of the andradite group, titanosilicates and Synroc D
were synthesized by the CCIM method at temperatures of 1250 – 1550°C.The preliminary X-ray diffraction studies of these materials indicate that
the structures synthesized by the CCIM method have compositions that are
identical to those of the corresponding natural analogs. The chemical
durabilities of the synthesized materials upon their exposure to distilled
water at 20°C have been determined.In addition to the investigation of solidification of liquid HLW, the CCIM
method is examined and applied to the synthesis of mineral-like compositions
involving simulated waste components (nonsoluble residues, ashes, and pulps)
produced by the chemical and metallurgical manufacturing of fissile
materials.