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Characterization of ODS Steels after Gamma Irradiation for Application in ALLEGRO Reactor

100%
Slugeň V., Bartošová I., Dekan J.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
1090-1092
EN
Oxide-dispersion strengthened steels characterization using various spectroscopic techniques is presented. Microstructure of 15% chromium oxide-dispersion strengthened steels was studied in term of vacancy defects presence and their accumulation after defined irradiation treatment, respectively. Studied materials originated from Kyoto University and studied via IAEA collaborative project focused on generation IV reactors (ALLEGRO). Samples were characterized "as received" by positron annihilation lifetime spectroscopy, the Mössbauer spectroscopy and their microstructure was examined by transmission electron microscopy as well. Samples were afterwards irradiated in Washington State University Nuclear Radiation Center via a strong gamma source (6 TBq). Damage induced by gamma irradiation was evaluated by positron lifetime measurements in emphasis on defect accumulation in the materials. We have demonstrated strong defect production induced by gamma irradiation which results from positron measurement data.
2
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Vickers Hardness and Positron Annihilation Study of Eurofer97 and ODS Eurofer

100%
Bartošová I., Čížek J., Lukáč F., Slugeň V.
Acta Physica Polonica A
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2014
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vol. 125
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issue 3
702-705
EN
This paper describes investigations of Eurofer97 and oxide dispersion strengthened version of this steel, in as received state and after annealing. Vickers hardness test was performed on the as received specimens and after annealing at various temperatures to obtain information about development of the strength of studied materials. After identifying the temperature region where significant changes of the strength take place we applied positron annihilation spectroscopy to probe the microstructural changes in ferritic/martensitic steels. An observation of phase transformation was observed in both steels at various temperatures indicating different behaviour of the base material and its strengthened version. All applied methods proved the importance of strengthening by oxides to improve properties of steels.
3
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Optimization of Positron-Lifetime Measurement Geometry Based on Geant4 Simulation

100%
Saro M., Petriska M., Slugeň V.
Acta Physica Polonica A
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2017
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vol. 132
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issue 5
1634-1636
EN
Proper choice of measuring geometry and experimental setup of nuclear instrumentation modules and photomultipliers is a key element which affects substantial positron lifetime measurement properties: count rate and time resolution. An adequate compromise must be found, when it comes to geometry of measurement. The optimal geometry using three detector layout is inspected in this paper. During our work, we concentrated on the simulation of XP2020Q photomultipliers and the BaF₂ scintillator material. The Geant4 simulation allows to estimate an influence of the measuring geometry on detection efficiency and to choose the most appropriate crystals dimensions and positions. As mentioned in paper of Bečvaŕ et al., slight changes in geometry result in distortion or improvement of measured results. Experimental results already showed, changes of start crystals dimensions can result in significant increase in count rate of three-detector measurement.
4
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Mössbauer Spectroscopy Study of Laboratory Produced ODS Steels

100%
Degmová J., Dekan J., Šimeg Veterníková J., Slugeň V.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
1171-1173
EN
The investigated oxide dispersion strengthened steels were received from laboratories involved in the Coordinated Research Project F11014 "Benchmarking of Structural Materials Pre-selected for Advanced Nuclear Reactors", namely from India (IGCAR), Russia (Bochvar Institute), China (University of Beijing), and Japan (Kyoto University). The application of the Mössbauer spectroscopy on these materials is aimed to reveal the complex information about studied materials via unique characteristics as micromagnetic properties and homogeneity of admixtures distribution in steels. All studied steels mainly differ in content of elements as Cr or Al. Chosen fitting model consists of bcc Fe, bcc Fe with Cr substitution and paramagnetic bcc Cr rich components. These ODS steels are aimed in further study for He implantations.
5
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Effect of the Initial Microstructure on Defect Evolution in Neutron Irradiated Fe-Cr-C Alloys

88%
Brodziansky T., Slugeň V., Sojak S., Petriska M., Konstantinović M.
Acta Physica Polonica A
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2017
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vol. 132
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issue 5
1590-1592
EN
The irradiation-induced evolution of vacancy type defects in various iron-chromium model alloys and high chromium ferritic/martensitic steels have been studied using coincidence Doppler broadening spectroscopy. Specimens were neutron irradiated to 0.11 dpa at two different temperatures, 290°C and 450°C. It has been found that the microstructure (ferrite vs. ferrite/martensite), more precisely distribution of dissolved carbon within the matrix, is one of the key factor that affect response of the materials to neutron irradiation. Presence of dissolved carbon within the matrix leads to formation of stable and immobile carbon-vacancy complexes which act as traps for irradiation induced vacancies and therefore, leading to increased formation of vacancy clusters. Impact of carbon-vacancy complexes on defects evolution during neutron irradiation is relevant only for certain irradiation temperatures.
6
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German and Russian Irradiated Reactor Pressure Vessel Steels from PAS Point of View

64%
Slugeň V., Hein H., Sojak S., Pecko S., Šimeg Veterníková J., Petriska M., Sabelová V., Bartošová I., Stacho M.
Acta Physica Polonica A
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2014
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vol. 125
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issue 3
726-728
EN
This paper presents a comparison of commercially used German and Russian reactor pressure vessel steels from the positron annihilation spectroscopy point of view, having in mind knowledge obtained also from other techniques from the last decades. The second generation of Russian reactor pressure vessel steels seems to be fully comparable with German steels and their quality allows prolongation of NPP operating lifetime over projected 40 years. The embrittlement of CrMoV steels is very low due to the dynamic recovery of radiation-induced defects at reactor operating temperatures. Positron annihilation spectroscopy techniques can be effectively applied for evaluation of microstructural changes caused by extreme external loads by proton implantation, with aim to simulate irradiation and for the evaluation of the effectiveness of post-irradiation thermal treatments. We used our actual and previous results, collected during last 20 years from measurements of different reactor pressure vessel steels in "as received", irradiated and post-irradiation annealed state and compare them with the aim to contribute to general knowledge based on experimental positron annihilation spectroscopy data.
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