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1.
K. Radó Z. Németh K. Varga J. Schunk F. Kőrösi 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):313-322
Summary During
the period of 1993-2001 chemical decontaminations of 24 SGs in the units 1-3 of
the Paks NPP were carried out by a non-regenerative version of AP-CITROX
technology, even in two or three consecutive cycles. A comprehensive
investigation of the above decontamination method have revealed that the
fundamental issues of analytical chemistry and corrosion science were not taken
into consideration during the elaboration of AP-CITROX procedure. Therefore,
the non-regenerative version of the technology utilized at Paks NPP can be
considered to be not an adequate method for the chemical decontamination of any
reactor equipments having large steel surfaces (e.g., SGs). As a consequence of
the lack of the appropriate decontamination method, initiation of a R&D project
focused on the elaboration of the required technology should not be postponed.
In this paper, we present a brief overview on the fundamental issues of the
technology development. Selected findings obtained in our laboratory on
the field of the improvement of the AP-CITROX technology are also reviewed in
order to demonstrate the crucial role of some selection criteria.</p>
</p> 相似文献
2.
K. Varga Z. Németh J. Somlai I. Varga R. Szánthó J. Borszéki P. Halmos J. Schunk P. Tilky 《Journal of Radioanalytical and Nuclear Chemistry》2002,254(3):589-596
During the optimization of the AP-CITROX decontamination technology the effect of the different flow rates of the decontamination solutions on the radioactive contamination and corrosion state of stainless steel tube samples originating from steam generators of Paks NPP were studied by a pilot-plant circulation system. The results have proved that a significant increase (up to 2.89 m/s) in the flow rate of the decontamination solution in the 1-5 steps is highly recommended and in order to improve the passivity of the surfaces it should be kept as low as possible (0.5 m/s) during the passivation. 相似文献
3.
Hong-Joo Ahn Myung-Ho Lee Se-Chul Sohn Kwang Yong Jee Kyuseok Song 《Journal of Radioanalytical and Nuclear Chemistry》2010,285(2):199-205
In order to evaluate radionuclide inventories as an essential item for the permanent disposal of spent fuel storage racks,
chemical conditions for a sample pretreatment of a spent fuel storage rack were studied. Especially, the surface microstructure
and the radionuclide distributions for the spent fuel storage rack were investigated by using a SEM–EDX and γ-spectrometer
for minimizing the matrix effect which could affect a chemical separation process of some β-emitting radionuclides. The samples
were pretreated with a mixed solution of 5 M HCl and 2 M HNO3 by an ultrasonic surface leaching method. Some radionuclides in the raw racks showed the radioactivity of 102–103 Bq for about 10 g of sample weight. From the sample pretreatment, it was confirmed that almost all radionuclides in the rack
were completely extracted from the rack when the dissolved thickness of the rack became a maximum 15 μm by the ultrasonic
surface leaching method. The established pretreatment method was applied for all spent fuel storage rack generated from Korean
NPPs to determine the scaling factor. The radioactivities of 60Co and 137Cs radionuclides in the pretreated solutions were in the range of 4.9E−1~1.5E+2 and 1.2E−1~9.0E+0 Bq/g, respectively. 相似文献
4.
Andrzej Lewenstam 《Journal of Solid State Electrochemistry》2011,15(1):15-22
In most interpretations of potentiometric ion sensor responses with glass, solid, or liquid/polymer membranes, a model assuming
electrochemical equilibrium between the aqueous sample and the membrane is used. This model is often called a phase boundary
model to emphasize the importance of ion-exchange processes at the interface. The essence of the phase boundary model is that
it accepts electroneutrality and thermodynamic equilibrium, and thus ignores electrochemical migration and the time-dependent
effects. For this reason, this model is in conflict with many experimental reports on ion sensors in which both kinetic (time-dependent)
discrimination of ions to improve selectivity and non-equilibrium transmembrane ion transport for lowering the detection limits
are deliberately used. To respond to the experimental challenges in the author’s groups, we elevated the potentiometric modeling
by using the Nernst–Planck–Poisson (NPP) equations system to model the non-equilibrium response. In the NPP model, electroneutrality
and steady-state/equilibrium assumptions are abandoned, and thus we access the space and time domain. This approach describes
the concentration changes of ions participating in the ion-exchange and transport processes, as well as the electrical potential
evolution over space and time, and allows in particular, the inspection of the equilibrium set by the phase boundary models
as a special “stationary” case after infinite time. Additionally, directly predicting the selectivity and the low detection
limit variability over time and the influence of other parameters, e.g., ion diffusibility, is possible. As a coherent and
non-arbitral model, the NPP system facilitates solving the inverse problem, i.e., to optimize the sensor properties and measurement
conditions in a customized way via desired target functions and hierarchical genetical strategy modeling. In this way the
NPP allows setting the conditions under which the experimentally measured selectivity coefficients are true (unbiased) and
the detection limits are optimized. 相似文献
5.
Z. Homonnay A. Vértes E. Kuzmann K. Varga P. Baradlai G. Hirschberg J. Schunk P. Tilky 《Journal of Radioanalytical and Nuclear Chemistry》2000,246(1):131-136
A real specimen originating from the primary circuit of a VVER-440 type pressurized water cooled nuclear reactor has been studied by Conversion Electron Mössbauer Spectroscopy (CEMS) in order to find out how the AP-CITROX decontamination procedure modifies the structure and composition of the surface oxide layer of stainless steel which is used in the steam generator. Other methods like voltammetry, gravimetry, and SEM-EDAX were also applied to characterize the samples and to help the interpretation of CEMS results. It was found that, in contradiction with expectations, the presence of the surface magnetite layer could not be convincingly identified even on the non-decontaminated sample. This finding together with the relatively weak Mössbauer signals indicated that the surface oxide layer is strongly Fe-depleted. It was also concluded that the upper layer of the bulk steel (under the oxide layer) has an altered composition probably due to irradiation-enhanced diffusion of the metallic constituents. It was established that the AP-CITROX decontamination procedure does not exert detrimental effects on the thickness and composition of the surface oxide layer. 相似文献
6.
Cappelletto Elisa Callone Emanuela Campostrini Renzo Girardi Fabrizio Maggini Simona della Volpe Claudio Siboni Stefano Di Maggio Rosa 《Journal of Sol-Gel Science and Technology》2012,62(3):441-452
Paper is an organic material widely used in cultural heritage and mainly composed of cellulose mixed with lignin, hemicellulose
and small amounts of additives. This paper deals with siloxane coatings on pure cellulose paper, applied by sol–gel dipping
in sols prepared with different siloxane precursors (tetraethoxysilane, methyl triethoxysilane, dimethyl diethoxysilane, trimethyl
monoethoxysilane). The coated samples were characterized using various techniques (Fourier Transform Infrared Spectroscopy
FT-IR, Nuclear Magnetic Resonance NMR and Scanning Electron Microscopy and Energy Dispersive Spectroscopy SEM–EDS), measuring
their mechanical properties, flame resistance and contact angles, and a colorimetric test. The coated samples’ behavior was
more hydrophobic the higher the methyl number of siloxane precursor, regardless of the coating’s thickness. Increasing the
thickness improved the mechanical and thermal properties. The thickest coatings were obtained using a double coating process
and a basic catalyst for the hydrolysis step, but this latter condition facilitated the formation of surface agglomerates,
which make the paper too stiff and yellow. 相似文献
7.
Electrochemically deposited Zn–Co alloys under various deposition conditions were investigated using anodic linear sweep voltammetry
for phase structure determination, scanning electron microscopy for surface morphology analysis, atomic absorption spectroscopy
for determination of chemical composition, and polarization measurements and open circuit potential measurements for determination
of corrosion properties. The influence of deposition current density, temperature, and composition of deposition solution
on the phase structure and corrosion properties of Zn–Co alloys was studied. It was shown that the ratio of cobalt to zinc
ions in the plating bath strongly affects the chemical content and phase structure, as well as corrosion stability, of Zn–Co
alloys. Zn–Co alloys deposited from plating baths with the lowest and the highest ratios of cobalt and zinc ions exhibited
the lowest corrosion rate. 相似文献
8.
Uwe Burghaus 《Journal of Thermal Analysis and Calorimetry》2011,106(1):123-128
The effect of carbon nanotubes’ (CNT) crystal structure on chemical reactivity has been studied in much detail in the liquid
phase using CNT suspension. This type of information is pertinent for developing CNT separation strategies. However, few experimental
studies are available providing data for gas–CNT interactions utilizing ultra-high vacuum (UHV) surface science techniques.
Structure–activity relationships (SAR) for gas–surface interactions are important for sensor designs and heterogeneous catalysis
exploring, for example, CNT’s potential as a support for fuel cell catalysts. We report on UHV kinetics experiments with single-wall
metallic, semiconducting, and mixed CNTs in order to provide the experimental basis to correlate CNT’s crystal structure and
chemical activity. Thermal desorption spectroscopy (TDS), a simple temperature ramping technique, has been used to determine
the binding energies of a number of probe molecules including alkanes, alcohols, thiophene, benzene, and water on CNTs at
UHV conditions. TDS allows for the identification of adsorption sites of probe molecules in CNT bundles, using gold foil or
silica as a support for the drop-and-dry technique. A weak and probe molecule dependent SAR is present for adsorption inside
the CNTs but not for the population of external sites by the probe molecules. The experimental data are in part consistent
with current theoretical predictions by other groups. In addition, the effect of different solvents (methanol, SDS, and NMP)
and cleaning procedures will briefly be discussed using results of spectroscopic (Auger electron spectroscopy) and kinetic
techniques. Furthermore, molecular beam scattering techniques were utilized to characterize the adsorption dynamics, i.e.,
the gas-to-surface energy transfer processes of alkanes on CNTs. For example, opening the CNT tube ends by high temperature
annealing, increases the so-called initial adsorption probability, that is, the probability for adsorption in the limit of
zero surface concentration (coverage). This result directly illustrates the effect of large surface areas of CNTs, using internal
and external surfaces, for gas adsorption. 相似文献
9.
Masoud Salavati-Niasari Mohammad Reza Ganjali Parviz Norouzi 《Transition Metal Chemistry》2007,32(1):1-8
Nanocavity zeolite-Y (host) encapsulated Co(II), Ni(II) and Cu(II) complexes of unsaturated 16-membered octaaza; 3,4,11,12-tetramethyl-1,2,5,6,9,10,13,14-octaazacyclohexadecane
‘Me4[16]aneN8’; macrocycle (guest) were synthesized and characterized by chemical analyses, s.e.m., x.r.d., u.v.–vis., d.r.s., surface
area, pore volume, conductometric, magnetic measurements and i.r. spectroscopy with a view to confirming the encapsulation
of complexes and to arrive at the composition, structure and geometry of encapsulated complexes. The characterization data
show the absence of extraneous complexes, retention of zeolite crystaline structure and encapsulation in the nanocavities.
Host–Guest Nanocomposite Materials (HGNM) ‘[M(Me4[16]aneN8)]2+-NaY’ are catalytically very efficient as compared to other neat complexes for the partial oxidation of benzyl alcohol which
is stable and becomes recycled without much deterioration. 相似文献
10.
By anodic oxidation of hydrogen on the Pt ring of a metal-disk-Pt-ring rotating electrode in aqueous acid (pH 0.5–3) sulfate
solutions, it is shown that during the polarization of the metal disk hydrogen coevolves by two parallel reactions. One is
the well known electrochemical charge transfer process, while the other one is a direct chemical reaction of the metal, i.e.
iron, with water molecules from the electrolyte. This process was proposed a long time ago by Kolotyrkin and co-workers, but
their experimental results were subjected to serious criticism which is taken care of in the present paper. The chemical reaction
is potential- and pH-independent and, depending on the actual conditions during the corrosion processes (actual potential,
pH, etc.), can be of greater or smaller importance in the overall process. The consequences of the existence of this direct
chemical reaction of metal with water molecules (i.e. H2O-induced corrosion or chemical corrosion) on pitting and stress corrosion cracking of metals is discussed.
Dedicated to the ninetieth anniversary of Ya.M. Kolotyrkin’s birth.
This article was submitted by the authors in English. 相似文献
11.
The first step in decommissioning of NPP is connected with defueling and successful disposal of liquid radioactive wastes (LRW), both from previous production and all work connected with this step. These require precise knowledge about the concentration of radioactive nuclides presented, especially alpha-emitters in all material fluxes arising in sich work (namely shut-down after some accident). This paper reports, results of the determination of U, Pu, Am and Cm by means of both the commonly used and the newly developed radiochemical procedures in various types of materials, e.g., LRW, aerosol filters, ashes resulted from incineration technology, metal surfaces, decontamination solutions etc. 相似文献
12.
Helmut Tributsch 《Journal of Solid State Electrochemistry》2009,13(7):1127-1140
Nanocrystalline solar cells promise significant advantages with respect to cost-efficient mass production, since they do not
require imprinted chemical potential gradients for charge separation (e.g., electrical fields generated by p, n doping, which
should last for one to three decades). They, however, require kinetic charge separation and chemical electronic mechanisms,
which rectify photocurrents for energy conversion. Such mechanisms are presently not well understood, since the existing nanosolar
cells (dye and polymer solar cells) have evolved largely empirically. It is shown in this paper that function and properties
of kinetically determined solar cells can be derived from irreversible thermodynamic principles considering minimum entropy
production (or the principle of least action) and involve solid-state electrochemical processes. Based on this model, presently
studied nanosolar cells and also the primary photosynthetic mechanism are analyzed to identify the most significant physical–chemical
factors involved.
Dedicated to the 85th birthday of John O’M. Bockris.
Parts of this contribution were previously reported as a lecture at QUANTSOL 2008, Bad Gastein, Austria, March 2–7, and at
NANOMAT 2008, Ankara, Turkey. 相似文献
13.
Effects of exposure time on the anodic dissolution of Monel-400 in aerated stagnant sodium chloride solutions 总被引:1,自引:0,他引:1
El-Sayed M. Sherif 《Journal of Solid State Electrochemistry》2012,16(3):891-899
The anodic dissolution of Monel-400 (63.0% Ni, 28–34% Cu) alloy after its immersion in freely aerated stagnant 3.5% NaCl solutions
for 0, 24, and 72 h has been investigated. The study was carried out using a variety of electrochemical techniques and gravimetric
measurements after varied exposure periods (5–160 days). The work was complemented by scanning electron microscopy and energy
dispersive X-ray analyzer (SEM/EDX) investigations. The electrochemical measurements showed that Monel suffers both general
and pitting corrosion. The severity of uniform corrosion decreased, while pitting one increased with increasing the immersion
time to 24 h and further to 72 h before measurements. Gravimetric data indicated that the weight loss increased, while the
corrosion rate decreased for Monel with time. SEM images and EDX profile analyses confirmed that the corrosion of Monel after
160 days immersion in NaCl solutions occurs due to the selective dissolution of nickel. 相似文献
14.
Mesoporous titania nanoparticles (denoted as MTN) with high surface area (e.g., 252 m2 g−1) were prepared using tetrapropyl orthotitanate (TPOT) as a titania precursor and 10–20 nm or 20–30 nm silica colloids as
templates. Co-assembly of TPOT and silica colloids in an aerosol-assisted process and immediate calcination at 450 °C resulted
in anatase/silica composite nanoparticles. Subsequent removal of the silica colloids from the composite by NaOH solution created
mesopores in the TiO2 nanoparticles with pore size corresponding to that of silica colloids. Effects of silica colloids’ contents on MTN porosity
and crystallites’ growth at a higher calcination temperature (e.g., 1000 °C) were investigated. Silica colloids suppressed
the growth of TiO2 crystallites during calcination at a higher calcination temperature and controllable contents of the silica colloids in precursor
solution resulted in various atomic ratios of anatase to rutile in the calcinated materials. The mesostructure and crystalline
structure of these titania materials were characterized by transmission electron microscope (TEM), scanning electron microscope
(SEM), X-ray diffraction (XRD), differential thermal analysis (DTA)-thermo-gravimetric analysis (TGA), and N2 sorption. 相似文献
15.
Ganesha Achary H. P. Sachin S. Shivakumara Y. Arthoba Naik T. V. Venkatesha 《Russian Journal of Electrochemistry》2007,43(7):844-849
The zinc metal surface is chemically modified by newly synthesized Schiff’s bases and its corrosion protection is investigated.
The influence of concentration of Schiff’s bases on modification of zinc surface and immersion time in treatment bath are
investigated and optimized for maximum corrosion protection efficiency. The electrochemical studies of treated zinc specimens
are performed in aqueous acid solution using galvanostatic polarization technique. The treated zinc samples show good corrosion
resistance. The recorded electrochemical data of chemically treated samples indicate a basic modification of the zinc surface.
The protection efficiency of organic layer formed on zinc surface is tested by varying the acid concentration and temperature
of the corrosive medium. The corrosion protection efficiency increases with the concentration of Schiff’s bases and immersion
time. This is due to a strong interaction between zinc and the organic molecules, which results in the formation of a protective
layer. This layer prevents the contact of aggressive medium with the zinc surface. The surface modification is confirmed by
the scanning electron microscopy images. The interaction between metal atoms and Schiff’s bases is also established by IR
studies.
Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 7, pp. 886–892.
The text was submitted by the authors in English. 相似文献
16.
The relationship between the experimental ionization potentials and energies of the highest occupied MO was analyzed for various
conformations of styrene derivatives using the photoelectron spectra of a series of α-substituted styrenes and quantum chemical
calculations of their electronic structure. The characteristics of the HOMO of the planar conformations correlate both with
the ionization potentials and the reactivities of these molecules.
Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg St., Donetsk,
Ukraine 340014, Institute of Technical and Macromolecular Chemistry, Martin Luther University, Halle Wittenberg, Merseburg,
Germany D-06217. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 1, pp. 36–42, January–February,
1998. 相似文献
17.
A reaction–diffusion system consisting of one, two or three chemical species and taking place in an arbitrary number of spatial
dimensions cannot exhibit Turing instability if none of the reaction steps express cross‐inhibition. A corollary of this result
– obtained by elementary calculations – underlines the importance of nonlinearity in the formation of stationary structures,
a kind of self‐organization on a chemical basis. Relations to global stability of reaction–diffusion systems, and results
on multispecies systems are also mentioned. The statements are not restricted to mass action type models. As a by‐product,
the solution of a basic inverse problem of formal kinetics is also presented which extends a previous result by Hárs and Tóth
(1981) to models with arbitrary – including rational – functions as reaction rates so often occurring, e.g., in enzyme kinetics.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
Stefan Wellert Henrik Imhof Michael Dolle Hans-Jürgen Altmann André Richardt Thomas Hellweg 《Colloid and polymer science》2008,286(4):417-426
At the present time, considerable efforts are being made to develop new media for the decontamination of a variety of toxic
compounds. In the present contribution, new microemulsions with promising properties are presented. Moreover, the decontamination
of surfaces, with an emphasis on varnished metal surfaces of exterior and interior equipment, is investigated using these
microemulsions. Studies of the phase behavior of the system water–perchloroethylene–IHF–2-propanol are reported and the microemulsion
phases are recognized. The wetting behavior on contaminated surfaces and the extraction capabilities with respect to contaminants
are essential for an efficient decontamination. Hence, suitable microemulsions are identified on the basis of these properties.
The decontamination efficiency of these microemulsions is first estimated on the basis of the ability to wet typical chemical
nonresistant varnished steel sheets, which are authentic model systems for real surfaces. Afterwards, promising microemulsions
and, as reference, different solvents are tested with respect to their capability to solubilize sulfur-mustard agent, again
using realistic surfaces contaminated with this chemical warfare agent. Several microemulsions are found, which have the desired
properties. 相似文献
19.
Nanoparticles are usually 1–100 nm in each spatial dimension considered as building blocks of the next generation of optoelectronics,
electronics, and various chemical and biochemical sensors. In the synthesis of nanoparticles use of microorganisms emerges
as an eco-friendly and exciting approach that reduce waste products (ultimately leading to atomically precise molecular manufacturing
with zero waste); the use of nanomaterials as catalysts for greater efficiency in current manufacturing processes by minimizing
or eliminating the use of toxic materials (green chemistry principles); the use of nanomaterials and nanodevices to reduce
pollution (e.g. water and air filters); and the use of nanomaterials for more efficient alternative energy production (e.g.
solar and fuel cells). Fungi have many advantages for nanoparticle synthesis compared with other organisms. In this study,
Geotricum sp. found to successfully produce Ag nanoparticles. Geotricum sp. was grown in SDA (Sabro Dextrose Agar) medium at 25 ± 1 °C for 96 h. The mycelia were used to convert silver nitrate
solution into nano-silver. Silver nanoparticles were synthesized using these fungi (Geotricum sp.) extracellularly. UV–VIS spectroscopy, Atomic Force Microscopy (AFM) and Scanning Electron Microscopy images shows the
nanoparticle formation in the medium. Energy-dispersive X-ray spectroscopy (EDX) also confirmed that silver nanoparticles
in the range of 30–50 nm were synthesized extracellularly. FTIR analyses confirmed the presence of amide (I) and (II) bands
of protein as capping and stabilizing agent on the surface of nanoparticles. 相似文献
20.
R. Ramanauskas L. Gudavičiūtė A. Kaliničenko R. Juškėnas 《Journal of Solid State Electrochemistry》2005,9(12):900-908
The influence of pulse plating parameters on the surface morphology, grain size, lattice imperfection and corrosion properties
of Zn–Ni alloy has been studied. The coatings were electrodeposited in an alkaline cyanide-free solution. AFM was applied
for surface morphology examination, XRD measurements were carried out for phase composition and texture analysis, electron
probe microanalysis was used for alloy chemical composition studies, while electrochemical techniques were applied for corrosion
performance evaluation. The pulse plated Zn–Ni coatings appeared to consist of the γ-Zn21Ni5 phase and the composition of the alloy depended on the plating parameters. The grain size, lattice imperfection and homogeneity
of grain distribution were established to be the main factors determining corrosion behaviour of the coating.
Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, March 13–16, 2005 相似文献