bluuebunny/crossref_metadata_2025_split huggingface dataset:
The 4th Unit of the Chernobyl NPP: Its Present State and Problems Related to its Transformation into an Ecologically Safe System
Authors: Anderson E. B. , Borovoy A. A. , Pazukhin E. M. 
Published: September 2012

ABSTRACTThe following problems related to the destroyed 4thUnit of the Chernobyl Nuclear Power Plant (NPP) are considered.Monitoring of the unit's current state, including:1)Monitoring of the atmospheric release of radioactive elements in the form of aerosols. In this case the problem is the unqualified area of cracks and holes that have formed in the “Sarcophagus” (the “Shelter”) since 1986. In addition, the method used to evaluate the release, in which an uncontrolled escape of radioactive contamination is possible, raises objections;2)Monitoring of the aquatic medium both inside the “Shelter” and on the industrial site. At present, the quantity of water in the 4thUnit is about 3000 m, which in fact is low- and intermediate-level radioactive waste. This quantity is not constant and essentially varies depending on the season, amount of atmospheric precipitation, the intensity of dust suppression, etc. In this case the problem is that the paths of water migration inside the unit are not known, so that an uncontrolled penetration of water into the ground, via the damaged foundation slab or the unit's walls, is quite possible;3)Monitoring of the state of lava-like fuel-containing masses (LFCM) and the fuel. The problem is that the exact location of the fuel in the 4thUnit, the amount of fuel in major aggregates of LFCM, and the nuclear safety of these aggregates are all unknown to date.The arrangements for the stabilization of the 4thUnit first of all include the reinforcement of the structural construction.The transformation of the “Shelter” into an ecologically safe system is subject to many questions still unresolved. In particular:Whether to create a common “Shelter-2” for the 3rand 4thUnits or to merely encase the destroyed 4thUnit in concrete (the project “Cube”);Whether to peace a plant for conditioning and reprocessing of radioactive waste under the roof of the “Shelter-2”, or to build this plant separately;Where to create a temporary repository for containers of radioactive waste from the ChNPP 4thUnit;How to solve the problem of radioactive waste permanent storage in the territory of the Ukraine with proper observation of all nuclear and radiation safety requirements
The Behavior of Nuclear Fuel in First Days of the Chernobyl Accident
Authors: Burakov B. E. , Anderson E. B. , Shabalev S. I. , Strykanova E. E. , Ushakov S. V. , Trotabas M. , Blanc J-Y. , Winter P. , Duco J. 
Published: September 2012

ABSTRACTVarious types of Chernobyl fuel containing masses named black “lava”, brown “lava”, porous “ceramic” and “hot” particles that formed during first days of the accident at the Chernobyl Nuclear Power Plant 4th Unit were studied by methods of optical and electron microscopy, microprobe and x-ray diffraction. Data about their chemical, phase and radionuclide composition are summarized. The products of interaction between fuel, zircaloy and concrete, produced under experiments in laboratory were examined for comparison with samples of Chernobyl “lava” and “hot” particles. The behavior of nuclear fuel in first days of the Chernobyl accident was a three-stage process. The first stage occurred before the moment of the Chernobyl explosion and was exceptionally short-lasting, perhaps, less than a few seconds. It was characterized by reaching a high temperature, ≥2600 °C, in the epicenter of accident and formation of a Zr-U-O melt in a local part of the core, which is estimated to be not more than 30% of whole core volume. The second stage lasted for about 6 days since the explosion, during which there was interaction between uranium products of the destroyed reactor: UOx, UOx with Zr, Zr-U-O, with the environment and silicate structural materials of the 4th Unit. The third stage, after 6 days involved the process of final formation of the radioactive silicate melt or Chernobyl “lava” at one of the sections of the destroyed 4th Unit. During this stage the melt's lamination occurred, followed by a break-through of the “lava” reservoir on the 11 th day of the accident and penetration of the “lava” into space under the reactor.
Secondary Uranium Minerals on the Surface of Chernobyl
“Lava”
Authors: Burakov B. E. , Strykanova E. E. , Anderson E. B. 
Published: September 2012

ABSTRACTThe formation of uranium minerals is still continuing in Chernobyl Unit No.
4. Yellow products of alteration that stain the surface of Chernobyl “lava”
have been examined by SEM and X-ray diffraction methods. Secondary minerals
of uranium identified are: UO4·4H2O studtite;
UO3·2H2O epiianthinite;
UO2·CO3 rutherfordine; also,
Na4(UO2)(CO3)3 was identified
together with the sodium carbonate phases
Na3H(CO3)2·2H2O and
Na2CO3·H2O. These minerals formed due to
the interaction between fuel-containing masses or “lava”, water and air. The
matrices of the “lava” do not contain significant amounts of sodium. The
source of sodium may be water that has penetrated into the “Sarcophagus”.
All identified secondary minerals of uranium are highly unstable, and their
continued formation can seriously endanger the radiological situation of the
4th Unit.
Properties and Genesis of Hot Particles from the Chernobyl
Reactor Accident
Authors: Schubert-Bischoff Peter , Lutze Werner , Burakov Boris E. 
Published: September 2012

ABSTRACTOn April 25, 1986, the nuclear reactor Unit 4 (RBMK) at Chernobyl, Ukraine,
exploded. Besides molecular species, the fallout contained particles of
relatively high specific activity (hot particles) with a wide range of
chemical compositions. The composition of a hot particle bears information
about its genesis. Particle sizes ranged from a few to 100s of micrometers.
Data on a hot particle, found in Berlin, Germany, is presented and discussed
in context with earlier measurements on other particles to understand their
genesis. The chemical composition was determined by electron probe micro
analysis. Our particles are either reactor fuel (one) or fission product
alloys (nine). The alloys were formed during normal reactor operation.
Strongly varying concentrations of Fe and Ni suggest that at least some of
our particles reacted with molten structural material of the reactor. The
particles were mobilized by fuel oxidation or fuel dust generation during
the accident. The fission product composition can only be explained if we
assume that the alloys remained in the solid state in the course of the
accident. Some particles may have been ejected during the explosion, others
later while the reactor was burning. Activities (103Ru and
106Ru, originally up to 160,000 Bq) of our ten year old
particles were re-measured but were no longer detectable. No long-lived
γ-emitters were found. The 99Tc activity was calculated and found
to only lBq. The γ -spectrum of the fuel particle still shows
137Cs (1 Bq) and 60Co (<1 Bq).
General Classification of “Hot” Particles from the Nearest
Chernobyl Contaminated Areas
Authors: Shabalev S. I. , Burakov B. E. , Anderson E. B. 
Published: September 2012

ABSTRACTThe morphology and composition both chemical and radionuclide of the main
types of the solid-phase “hot” particles formed following the accident on
the Chernobyl NPP have been studied by SEM, electron microprobe and
gamma-spectrometry methods. Differences in many isotopes including:
106Ru, 134Cs, 137Cs dependent upon the
hot particle matrix chemical composition was observed. The classification of
hot particles based upon the chemical composition of their matrices has been
done. It includes three main types: 1) fuel particles with UOx
matrix; 2) fuel-constructional particles with Zr-U-0 matrix, 3) hot
particles with metallic inclusions of Fe-Cr-Ni. Moreover, there are more
rare types of hot particles with silicate or metal matrices. It was shown
that only metallic inclusions of Fe-Cr-Ni are concentrators of
106Ru, which caused this nuclides assimilation in the molten
stainless steel during the initial stages of the accident. Soils
contamination of non-radioactive lead oxide particles in the Chernobyl NPP
region were noticed. It was supposed that part of metallic lead, dropped
from helicopters into burning reactor during first days of accident, was
evaporated and oxidized accompanying solid oxide particles formation.
Dissolution Rates of DWPF Glasses from Long-Term
PCT
Authors: Ebert W. L. , Tam S.-W. 
Published: September 2012

ABSTRACTWe have characterized the corrosion behavior of several Defense Waste
Processing Facility (DWPF) reference waste glasses by conducting static
dissolution tests with crushed glasses. Glass dissolution rates were
calculated from measured B concentrations in tests conducted for up to five
years. The dissolution rates of all glasses increased significantly after
certain alteration phases precipitated. Calculation of the dissolution rates
was complicated by the decrease in the available surface area as the glass
dissolves. We took the loss of surface area into account by modeling the
particles to be spheres, then extracting from the short-term test results
the dissolution rate corresponding to a linear decrease in the radius of
spherical particles. The measured extent of dissolution in tests conducted
for longer times was less than predicted with this linear dissolution model.
This indicates that advanced stages of corrosion are affected by another
process besides dissolution, which we believe to be associated with a
decrease in the precipitation rate of the alteration phases. These results
show that the dissolution rate measured soon after the formation of certain
alteration phases provides an upper limit for the long-term dissolution
rate, and can be used to determine a bounding value for the source term for
radionuclide release from waste glasses. The long-term dissolution rates
measured in tests at 20,000 m−1 at 90°C in tuff groundwater at pH
values near 12 are about 0.2,0.07, and 0.04 g/(m2•d) for the
Environmental Assessment glass and glasses made with SRL 131 and SRL 202
frits, respectively.
Simulation of Natural Corrosion by Vapor Hydration Test:
Seven-Year Results
Authors: Luo J. S. , Ebert W. L. , Mazer J. J. , Bates J. K. 
Published: September 2012

ABSTRACTWe have investigated the alteration behavior of synthetic basalt and SRL 165
borosilicate waste glasses that had been reacted in water vapor at 70°C for
time periods up to seven years. The nature and extent of corrosion of
glasses have been determined by characterizing the reacted glass surface
with optical microscopy, scanning electron microscopy (SEM), transmission
electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDS).
Alteration in 70°C laboratory tests was compared to that which occurs at
150–200°C and also with Hawaiian basaltic glasses of 480 to 750 year old
subaerially altered in nature. Synthetic basalt and waste glasses, both
containing about 50 wt % SiO2, were found to react with water
vapor to form an amorphous hydrated gel that contained small amounts of
clay, nearly identical to palagonite layers formed on naturally altered
basaltic glass. This result implies that the corrosion reaction in nature
can be simulated with a vapor hydration test. These tests also provide a
means for measuring the corrosion kinetics, which are difficult to determine
by studying natural samples because alteration layers have often spalled off
the samples and we have only limited knowledge of the conditions under which
alteration occurred.
Isothermal Crystallization Kinetics in Simulated High-Level
Nuclear Waste Glass
Authors: Vienna John D. , Hrma Pavel , Smith Donald E. 
Published: September 2012

ABSTRACTCrystallization kinetics of a simulated high-level waste (HLW) glass were
measured and modelled. Kinetics of acmite growth in the standard HW39–4
glass were measured using the isothermal method. A
time-temperature-transformation (TTT) diagram was generated from these data.
Classical glass-crystal transformation kinetic models were empirically
applied to the crystallization data. These models adequately describe the
kinetics of crystallization in complex HLW glasses (i.e., RSquared = 0.908).
An approach to measurement, fitting, and use of TTT diagrams for prediction
of crystallinity in a HLW glass canister is proposed.
Further Development of the Jantzen - Plodinec Model of Glass
Durability
Authors: Shakhmatkin B. A. , Vedishcheva N. M. , Aloy A. S. , Plodinec M. J. , Marra S. L. 
Published: September 2012

ABSTRACTThe hydration thermodynamic approach to the prediction of glass durability
was originally applied to nuclear waste glasses by Jantzen and Plodinec.
This approach is useful for control of the production of nuclear waste
glasses. However, improvements are necessary if the approach is to be
extended to different glasses, particularly those with higher alkali metal
concentrations. This is of special significance for vitrification of the
salt wastes at Hanford. Various methods for improving the predictive power
of the approach have been examined. Combining a more accurate representation
of the alkali metal species in the glass with a more rigorous thermodynamic
approach is a promising avenue to improved predictive power.
The Effect of Humic Acids on the Element Release from High Level Waste Glass
Authors: Wei J. , Van Iseghem P. 
Published: September 2012

ABSTRACTEu and Am doped glasses were interacted with synthetic interstitial clay water (SIC) and corresponding reference leachant, humic acids free interstitial solution (IS) to investigate the influence of humic acids on the leaching behaviour of the waste glass. Static leach tests were carried out at 40°C and 90°C. The release of the lanthanide Eu and the actinide Am from the glass was obviously enhanced by the presence of humic acids. The leaching of transition elements, Fe and Ti strongly depends on the humic acids concentration. The leaching of glass matrix components, Al and B was also influenced by the concentrations of humic acids. However, humic acids have little effect on the leaching of glass matrix element Si.
Sintered Glasses for High-Level Wastes
Authors: Russo D. O. , Messi de Bernasconi N. B. , Sterba M. E. , Heredia A. D. , Sanfilippo M. , Prastalo S. , Sbriller J. C. 
Published: September 2012

ABSTRACTThe objective of the work was to evaluate the long-term capacity of sintered
glass to retain high-level nuclear wastes (HLW) in near-repository
conditions. We have studied the corrosion behavior of waste forms partially
devitrified (43 vol.%) in different aqueous media. Devitrified samples were
irradiated at doses (γ radiation from a Co 60 source) ranging
from 1.4 × 106 Gy to 2.0 × 108 Gy, in order to study
their aqueous corrosion resistance in simulated underground water. The
results show little or no effect of irradiation on the density,
microstructure and corrosion resistance. The global dissolution rate was
almost constant around a value of 5×10−5 g. cm−2
d−1. Elemental dissolution rates were also unaffected by
radiation.
Effects of Redox Conditions of Water on Pu and Cm Leaching from Waste Glass
Authors: Inagaki Y. , Sakai A. , Furuya H. , Idemitsu K. , Arima T. , Banba T. , Maeda T. , Matsumoto S. , Tamura Y. 
Published: September 2012

ABSTRACTStatic corrosion tests were performed on the simulated waste glass doped with Pu and Cm (PuO2; 0.22wt%, Cm2O3; 0.09%) in deionized water at 90 °C with S/V ratio of 2600 m−1under oxidizing and reducing conditions, respectively. The corrosion tests under oxidizing conditions were performed in air, while the corrosion tests under reducing conditions were performed in an airtight stainless steel container purged with mixed gas (Ar+5%H2), where the Eh of the solution was maintained at approximately -0.45 V vs SHE. The results showed that the redox conditions have no remarkable influence on the leaching behavior of Pu and Cm. It was also observed that the Pu and Cm concentrations in the 1.8nm filtered solutions were one or two orders of magnitude lower than those in the 450nm filtered solutions under both redox conditions, which suggests that the insoluble suspended fractions (colloidal particles) with the size from 1.8nm to 450nm are dominant phase for Pu and Cm in the solution under both redox conditions.
Waste Glass Leaching and Alteration Under Conditions of Open
Site Tests
Authors: Sobolev I. A. , Ojovan M. I. , Batyukhnova O.G , Ojovan N. V. , Scherbatova T. D. 
Published: September 2012

ABSTRACTThe behaviour of waste glass was investigated under open site disposal
conditions. This glass was produced by vitrification of intermediate level
radioactive waste from nuclear power plants. Two types of borosilicate
glasses were obtained for two different reactor wastes, WWER and RBM.K.
Leaching and alteration mechanisms are discussed as well as the data
processing technique used for these long term tests. The decay of
radionuclides was accounted for in order to obtain correct results. The
leaching factors obtained can be used for the assesment of radionuclide
retention. Discontinuous leaching of Cs-137 has been observed during more
than 8 years testing time. The fluctuating leaching rate depends on glass
composition. The average leaching rate remains within (0.4 – 4) μg/sq.
sm·day.Alteration of waste glass includes the formation of surface layers and
cracks on the glass surface. SEM analysis of glass was used to show these
surface layers. The thickness of the layers was determined to be within 2–6
μm. The structure of these layers depends on glass composition and the
interfacing environment.
A Direct, Single-Step Plasma ARC-Vitreous Ceramic Process for
Stabilizing Spent Nuclear Fuels, Sludges, and Associated
Wastes
Authors: Feng Xiangdong , Einziger Robert E. , Eschenbach Richard C. 
Published: September 2012

ABSTRACTA single-step plasma arc-vitreous ceramic (PAVC) process is described for
converting spent nuclear fuel (SNF), SNF sludges, and associated wastes into
a vitreous ceramic waste form. This proposed technology is built on
extensive experience of nuclear waste form development and nuclear waste
treatment using the commercially available plasma arc centrifugal (PAC)
system. SNF elements will be loaded directly into a PAC furnace with minimum
additives and converted into vitreous ceramics with up to 90 wt% waste
loading. The vitreous ceramic waste form should meet the functional
requirements for borosilicate glasses for permanent disposal in a geologic
repository and for interim storage. Criticality safety would be ensured
through the use of “batch” modes, and controlling the amount of fuel
processed in one batch. The minimum requirements on SNF characterization and
pretreatment, the one-step process, and minimum secondary waste generation
may reduce treatment duration, radiation exposure, and treatment cost.
Accelerated Testing of Waste forms using a Novel Pressurized
Unsaturated flow (PUF) Method
Authors: McGrail B. P. , Martin P. F. , Lindenmeier C. W. 
Published: September 2012

ABSTRACTA new experimental technique has been developed to test waste forms and
other proposed engineered-barrier materials under unsaturated conditions.
Laboratory experiments using the pressurized unsaturated flow (PUF)
apparatus have been performed with a Na-Ca-Al borosilicate glass being
studied for immobilization of low-activity tank wastes and a reference
borosilicate glass for immobilization of high-level wastes (SRL-202). A
complex coupling between glass corrosion, secondary phase precipitation, and
unsaturated flow behavior was observed. Precipitation of a family of
Na-Ca-Al zeolites was also found to cause an acceleration in the reaction
rate of the low-activity waste glass. This same effect was observed after
approximately 1 year in high solid-to-liquid ratio batch tests but after
only 12 days using the PUF method at the same temperature. The onset of
secondary phase precipitation was tracked by monitoring changes in
volumetric water content and by inline chemical analysis. Finally, elemental
release of the major glass components and solution pH were found to differ
under unsaturated flow-through conditions as compared with saturated, batch
tests. These findings, while preliminary, have important implications for
understanding and modeling glass corrosion behavior under unsaturated
conditions.
Nepheline Precipitation in High-Level Waste Glasses :
Compositional Effects and Impact on the Waste Form
Acceptability
Authors: Li H. , Vienna J. D. , Hrma P. , Smith D. E. , Schweiger M. J. 
Published: September 2012

ABSTRACTThe impact of crystalline phase precipitation in glass during canister
cooling on chemical durability of the waste form limits waste loading in
glass, especially for vitrification of certain high-level waste (HLW)
streams rich in Na2O and Al2O3. This study
investigates compositional effects on nepheline precipitation in simulated
Hanford HLW glasses during canister centerline cooling (CCC) heat treatment.
It has been demonstrated that the nepheline primary phase field defined by
the Na2O-Al2O3-SiO2 ternary
system can be used as an indicator for screening HLW glass compositions that
are prone to nepheline formation. Based on the CCC results, the component
effects on increasing nepheline precipitation can be approximately ranked as
Al2O3 > Na2O > Li2O ≈
K2O ≈ Fe2O3 > CaO >
SiC2. The presence of nepheline in glass is usually
detrimental to chemical durability. Using x-ray diffraction data in
conjunction with a mass balance and a second-order mixture model for 7-day
product consistency test (PCT) normalized B release, the effect of glass
crystallization on glass durability can be predicted with an uncertainty
less than 50% if the residual glass composition is within the range of the
PCT model.
Phase Separation in Simulated Plutonium Glasses with Phosphate and Fluorine and the effect on Glass Corrosion in Water
Authors: Li H. , Vienna J. D. , Chen Y. L. , Wang L. Q. , Liu J. 
Published: September 2012

ABSTRACTThe solubility limit of phosphate in glass was found to decrease as fluorine increased. Amorphous phase separation was found in the glass as a result of interaction between phosphate and fluorine, in which Ce and Gd strongly partitioned. The glasses exhibiting amorphous phase separation showed higher normalized B releases according to the 31-day product consistency test (PCT) compared to glasses without phase separation. Phosphate that leached from glass into water increased the concentrations of Ce and Gd in the 7- and 31-day PCT solutions by more than an order of magnitude. The liquid state31P-NMR results suggested that phosphate in water interacts with Ce or Gd. Therefore, the observed concentration jump for Ce and Gd in the PCT solution may be attributed to the increases in the solubility limits of Ce and Gd as a result of phosphate complexation with Ce and Gd.
Chemistry and Performance of Blended Cements and Backfills for use in Radioactive Waste Disposal
Authors: Duerden S. , Glasser F. P. , Goldthorpe K. , Pedersen J. , Quillin K. , Ross D. , Stronach S. A. , Tyrer M. 
Published: September 2012

ABSTRACTThe ability of NaCl and MgSO4to impair the performance of Portland cement, blended cements containing slag and fly ash and of a permeable backfill have been measured. Performance is determined by decrease in pH, changes in mineralogy and loss of physical coherence. Experiments have been made at 25°, 55° and 85°C and extensively backed up by chemical models of cement performance. NaCl, up to 1.5M, has a comparatively slight impact on performance but MgSO4rapidly and almost quantitatively reacts, lowering system pH's to < 10, conditioned by mixtures of Mg(OH)2and magnesium silicates with gypsum.