Authors:K. Varga, Z. Németh, J. Somlai, I. Varga, R. Szánthó, J. Borszéki, P. Halmos, J. Schunk, and P. Tilky
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.
Authors:Z. Homonnay, A. Vértes, E. Kuzmann, K. Varga, P. Baradlai, G. Hirschberg, J. Schunk, and P. Tilky
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.
Authors:Z. Homonnay, P. Szilágyi, E. Kuzmann, K. Varga, Z. Németh, A. Szabó, K. Radó, J. Schunk, P. Tilky, and G. Patek
57Fe-conversion electron Mössbauer spectroscopy (CEMS) — a sensitive tool to analyze the phase composition of corrosion products
on the surface of stainless steel — was applied to study real specimens from the Paks Nuclear Power Plant, Hungary. The primary
circuit side of the heat exchanger tubes was studied on selected samples cut out from the steam generators during regular
maintenance. Mostly Cr-and Ni-substituted magnetite, amorphous Fe-oxides/oxyhydroxides as well as the signal of bulk austenitic
steel of the tubes were detected. The level of Cr-and Ni-substitution in the magnetite phase could be estimated from the Mössbauer
spectra. It is suggested that Cr-Ni substitution occurs simultaneously so that the inverse spinel structure of magnetite is
preserved up to a certain limit which appears to be roughly at [Fe3+]tet[Fe2+1/4Ni2+3/4Fe3+1/4Cr3+3/4]octO4. Further decrease of the iron content of this phase results in the formation of nickel chromite of regular spinel structure,
with very low Fe content. This transformation may be responsible for the hybrid structure of the protective oxide layer, being
substantially accelerated by previously performed, factory developed and proposed AP-CITROX decontamination cycles.
Authors:E. Gyurkovics, P. Arányi, Zs. Turóczi, D. Garbaisz, M. Varga, V. Hegedüs, G. Lotz, P. Kupcsulik, and A. Szijártó
External aortic compression due to acute gastric dilation is a rare etiology of the lower limb ischemia. This phenomenon leads the author to design experimental study for reperfusion syndrome. The lower limb ischemia-reperfusion (IR) injury consists of local and systemic components called the reperfusion syndrome. It can progrediate into a multi-organ failure which defines postoperative survival. A postconditioning is a surgical technique, which has a potential to reduce IR injury, therefore to prohibit the development of reperfusion syndrome.
XXXto examine on an experimental model, whether postonditioning is a practicable technique in infarenal aortic surgeries.
Materials and Methods
Male Wistar rats underwent 180 minutes of infrarenal aortic occlusion with 4, 24 and 72 hours of reperfusion. Postconditioning (10 sec. reocclusion / 10 sec. perfusion in 6 cycles) was applied in one group of each reperfusion time. Blood, urine, and histological (muscle, lung, kidney and liver) samples were collected at the postischemic 4th, 24th, and 72th hour.
The early inflammatory response (TNFa, free radicals) and late local inflammation were reduced by posctonditioning significantly. Postconditioning was able to reduce the remote organ injury of lungs and kidneys, the morphological and laboratorial results showed significant difference between the postconditioning and the control group in these two organs. The method's positive effect on remote organ injury remained long-term.
Postconditioning seems to be an applicable process to reduce both local inflammatory and systemic complications of IR injury following vascular surgeries.
Authors:E. Besenyei, P. G. Ott, Z. Bozsó, A. Czelleng, Á. Szatmári, G. J. Varga, and Z. Klement
The development of local early basal resistance (EBR), is a form of non-specific general defence response of plants to bacteria, greatly depending on temperature. This symptomless defence mechanism is easily detected by its inhibitory action on the hypersensitive response (HR) caused by a subsequent incompatible pathogenic bacterium. Both EBR and HR were investigated at different temperatures ranging from 30 °C to 5 °C. At normal temperatures (30-20 °C) both heat-killed Pseudomonas syringae pv. syringae 61 (polyvirulent to many plants) and Pseudomonas savastanoi pv. phaseolicola S21 (pathogenic to bean) induced EBR in tobacco leaves within a few hours, but below 10 °C it was greatly delayed and at 5 °C usually no EBR response could be detected within 2-3 days. The time required for development of EBR did not depend on the bacterial pathovars or strains. However, the induction time of HR was not as sensitive to low temperatures as that of EBR, instead, it depended on the bacterial pathovars used.
Authors:É. Varga, É. Palkonyai, P. Temesvári, F. Tóth, and I. B. Petri
We investigated the HLA-DRB, and DQB polymorphism and haplotypes in RA subjects of Hungarian origin by PCR typing using sequence-specific primers. Molecular subtyping of HLA-DRB1*04 alleles in RA patients showed strongest association with highest relative risk with DRB1*0404. A significantly decreased frequency of DRB1*0403 was observed in patients compared to controls. A significant number of patients carried DR4 haplotypes on DQB1*0302 (54%) relative to DQB1*0301 which was present on 36% of the haplotypes. When compared to controls, the frequency was higher in the latter allele only. Few unique DRB-DQB haplotypes were observed in Hungarian RA patients. In spite of the fact, that the Hungarian population has been isolated linguistically over centuries, a considerable racial admixture has occurred following immigration and invasions, thus the present study confirms in Hungarian patients with RA, previous findings for RA and HLA in European countries.
Authors:P. Kádár, K. Varga, Z. Németh, N. Vajda, T. Pintér, and J. Schunk
The surface contamination by uranium and transuranium (Pu, Am, Cm) nuclides in the primary circuit of pressurized water nuclear
reactors is a fairly complex problem as (i) different chemical forms (molecular, colloidal and/or disperse) of these atoms
can be present in the boric acid coolant, and (ii) only limited information about the extent, kinetics and mechanism of uranium
and transuranium (TRU) accumulation on constructional materials is available in the literature. A comprehensive program has
been initiated in order to study the accumulation of uranium and TRU species on some structural materials used at Soviet made
VVER-type pressurized water reactors (such as heat exchanger tube of steam generators and stainless steel canister material).
This paper, which is the first part of a series of two, provides a comprehensive view on the main experimental parameters
influencing the extent and character of the surface contamination by uranium and TRU nuclides. Specifically, we give a brief
summary of relevant literature data on the chemistry of uranium and TRU elements and review the dominant chemical forms and
their relative sorbability on austenitic stainless steel and Zr(Nb) alloy surfaces. Moreover, some findings on the distribution
of uranium, plutonium, americium, and curium species in a model solution of boric acid coolant obtained by the VisualMINTEQ
computer code are also presented and discussed.
Authors:Z. Wéber, Z. Bus, K. Gribovszki, B. Süle, Gy Szeidovitz, and P. Varga
In this paper, research activities at the Theoretical Division of the Seismology Department of GGRI (in short: Seismological Observatory) are summarized. The reported investigations have been carried out since 1999, when the division was founded with three members. Detailed discussions of the presented results can be found in various national and international scientific journals.
Authors:P. Varga, Z. Bus, B. Süle, A. Schreider, C. Bizouard, D. Gambis, and C. Denis
In its first part this work focuses on connection of length of day (LOD) with centered and eccentric geomagnetic dipole fields described with the use of Gaussian coefficients derived from global geomagnetic observations is discussed for the epoch 1900–2000. The statistical comparison of temporal variation of earth magnetic and astronomical data shows close correlation of geomagnetic dipole momentum
and ΔLOD. It should be mentioned that the time-correlation is closer when the centred geomagnetic dipole is used for statistical modelling. In the same time no relation was found between ΔLOD and the orientation variations of the geomagnetic dipole.In the second part of present study the connection of geomagnetic field and the LOD is investigated in geological time-scale. A significant ΔLOD was found which coincides in time with the geomagnetic Mesozoic low. The reason of this coincidence is enigmatic.
Authors:Gy Szeidovitz, I. Paskaleva, K. Gribovszki, K. Kostov, G. Surány, P. Varga, and G. Nikolov
Karst regions are very vulnerable with respect to natural and human-activity related hazards. Some of them with beautiful caves were proposed to be of national value. The examination of broken and slim intact speleothems in Bulgarian caves (Varteshkata and Elata caves, western part of Balkan Mountain Range, North-West Bulgaria) allows estimating an upper limit for horizontal peak ground acceleration (PGA) generated by paleo-earthquakes.The density, the Young’s modulus and the tensile failure stress of the samples originating from broken speleothems have been measured in a laboratory.The fundamental frequency and damping of speleothems have been measured in cavity by in situ observations.The value of the upper limit horizontal ground acceleration resulting in failure and the natural frequency of speleothems were assessed by theoretical calculations using mechanical parameters — the density, the Young’s modulus and the tensile failure stress — of the samples originating from a broken speleothem from Elata cave.The ages of the samples taken from the investigated stalagmites have been determined by alpha spectrometry.The pure elastic behaviour in analytical modeling and calculations have been used.According to our modeling results the investigated speleothem has not been excited by a horizontal acceleration higher than 0.144 g in case of Varteshkata cave, and 0.326 g in case of Elata cave during the last few thousand years. These results can serve to improve the present seismic risk policy for karst regions, too.