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5. The effect of different surface treatments of 310S austenitic stainless steel on the corrosion behavior in supercritical water using slow positron methods.

Author

Song, Yamin, Krsjak, Vladimir, Slugen, Vladimir, Novotny, Radek, Sojak, Stanislav, Novak, Michal, Dekan, Julius, Cao, Xingzhong, and Degmova, Jarmila

Subjects
AUSTENITIC stainless steel, STAINLESS steel corrosion, SUPERCRITICAL water, POSITRON beams, POSITRONS, WATER use
Abstract

The corrosion behavior of 310S austenitic stainless steel, subjected to different surface treatments machined (MA), sandblasting (SB), and polishing (PO), was exposed to a 550°C supercritical water (SCW) environment. The aged samples were analyzed using variable‐energy slow positron beam techniques. The obtained results revealed that the plastic deformation of the near‐surface region of the MA and SB samples was substantially recovered in the SCW conditions. At least two distinct oxide layers formed, and the oxidation process created a Fe/Cr depletion zone in the inner layer. Various surface treatments, however, led to different corrosion profiles. The depth profile of slow positron beam characterization suggests that significant residual stress and deformation zones on the surfaces of the sandblasted samples probably provided a diffusion path for the oxidation of the 310S. Only the SB samples exhibited a negative weight change after SCW exposure. At the same time, the SB samples showed the highest concentration of the positron traps in this region, which was explained by open‐volume defects associated with the microcracks introduced by sandblasting. [ABSTRACT FROM AUTHOR]

Published
2024
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22. Criticality safety parametric analyses of spent fuel storage pool for VVER-440

Author

Kristofova Kristina Kristofova, Kaprinayova Katarina Kaprinayova, Farkas Gabriel Farkas, Slugen Vladimir Slugen, and Hausner Peter Hausner

Subjects
Storage pool, Nuclear Energy and Engineering, Criticality, Nuclear engineering, Environmental science, VVER, Spent nuclear fuel, Parametric statistics
Published
2019

31. Influence of corrosive environments on steels studied by positron annihilation spectroscopy.

Author

Sojak, Stanislav, Krsjak, Vladimir, Degmova, Jarmila, Petriska, Martin, and Slugen, Vladimir

Subjects
POSITRON annihilation, AUSTENITIC stainless steel, NUCLEAR power plants, CONSTRUCTION materials, POINT defects, CORROSION resistance, SUPERCRITICAL water
Abstract

Corrosion is one of the negative effects influencing the current structural materials of nuclear power plants. The adequate corrosion resistance of structural materials, including austenitic stainless steels, has to be also considered in new designs of nuclear power plants. One of the approaches leading to the improvement of the corrosion resistance of steels goes through surface modifications. In this work, the influence of specimens surface treatment on their corrosion resistance was studied on materials for supercritical water reactor (SCWR) applications. The surface of the steels was prepared by different techniques, including sandblasting, polishing, shot peening and machining, in order to obtain information on the point defects behaviour after exposure to the supercritical water for various exposure times. The microstructural changes of studied steels 800HT and 310S were investigated by Pulsed Low Energy Positron System (PLEPS) [1,2]. A very distinct depth profile of point defects was observed in polished specimens, and the results indicate a significant decrease of the positron diffusion towards the surface in all mechanically modified samples. The increase of the SCW exposure time led to a clearly visible change in the obtained positron lifetimes, i.e., in the size of microstructural defects. [ABSTRACT FROM AUTHOR]

Published
2021
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40. Positron annihilation spectroscopy study of vacancy-type defects in He implanted polycrystalline alpha-SiC

Author

Li, Bingsheng, Krsjak, Vladimir, Degmova, Jarmila, Wang, Zhiguang, Shen, Tielong, Li, Hui, Sojak, Stanislav, Slugen, Vladimir, Kawasuso, Atsuo, and Atsuo, Kawasuso

Subjects
Condensed Matter::Materials Science
Abstract

The evolution of He implantation-induced defects in polycrystalline α-SiC has been investigated by a combination of positron annihilation Doppler broadening spectroscopy (DBS) and transmission electron microscopy (TEM). Samples implanted at room temperature with 230 keV He+ ions to fluences of 1 × 1015, 5 × 1015 and 1 × 1016 ions/cm2 were isochronally annealed in vacuum at temperatures up to 1400 °C with a step of 100 °C. Excellent correlation between the calculated damage profile and the positron annihilation depth profile were obtained at low annealing temperatures, after considering the positron depth distribution given by so-called Makhovian profiles. The DBS data from the peak region revealed a reasonable correlation between positron trapping at vacancy-type defects and the He-to-dpa ratio. Thermal annealing at 1400 °C resulted in the incomplete recovery of the microstructure, where large cavities distributed along grain boundaries in the damage peak region are surrounded by small agglomerations of (helium)vacancy-type defects.

Published
2020

42. Knowledge survey based on published works in the area of WWER reactor pressure vessel steels microstructure

Author

Slugen, Vladimir

Subjects
Knowledge-based systems -- Analysis, Neutrons -- Analysis, Radiation chemistry -- Analysis, Nuclear pressure vessels -- Properties, Nuclear pressure vessels -- Analysis, Knowledge-based system, Petroleum, energy and mining industries
Abstract

Byline: Vladimir Slugen The effects of intensive fluxes of neutrons, thermal ageing or other external factors result in considerable changes of material microstructures and properties. In particular, the development of the fine scale radiation-induced defects which impede the dislocation motion under the applied stress, known as the irradiation embrittlement, leads to mechanical properties degradation which can results to the partial loss of plasticity and to the increase of brittle fracture. Defects are formed from vacancies and interstitials created in collision cascaded processes. With the aim to reveal processes connected to WWER pressure vessel steel degradation, the importance of experimental microstructural studies was accented in many comprehensive works during the last 40 years. Many of these investigations resulted in valuable findings used worldwide. This paper is focused on the survey of knowledge extracted from relevant papers in area WWER steel microstructure selected by group of experts in frame of EC framework projects 'Nuclear Knowledge Preservation & Consolidation' coordinated by JRC Petten.

Published
2010

44. Evaluation of the Role of Cr, Ni, Mn and Si Si in Reactor Pressure Vessel Steel

Author

DEGMOVA Jarmila, VETERNIKOVA Jana, SOJAK Stanislav, SLUGEN Vladimir, KRSJAK VLADIMIR, and ACOSTA IBORRA Beatriz

Abstract

In this paper we report initial results from a study focused on investigation of the role of elements as Cr, Ni, Mn and Si in the radiation stability of reactor pressure vessel steels. Twelve model ferritic steels with basic composition derivated from Russian WWER-1000 and Western PWR reactor pressure vessel materials were studied by Charpy-V impact, magnetic Barkhausen noise, Vickers hardness tests, Relative Seebeck Coefficient measurements and Positron annihilation spectroscopy. Higher Cr content in model steels was found generally to give increased root mean square values independent of Mn and Si contents. The ductile¿brittle transition temperatures and hardness values of the model steels were found to be independent of composition. The correlation between ductile¿brittle transition temperatures and hardness values has potential for prompt determination of the effect of composition and irradiation on the steel properties. The next stage of the assessment will study the effect of irradiation of the model steels to accumulated neutron fluences of 10e19 n.cm-2., JRC.DDG.F.4-Safety of future nuclear reactors

Published
2010

49. Angular correlation positron annihilation spectroscopy applied in investigation of neutron irradiated RPV-steels.

Author

Slugen, Vladimir, Hascik, Jan, and Grone, Rudolf

Subjects
*ANGULAR correlations (Nuclear physics), *POSITRON annihilation, *SPECTRUM analysis, *NUCLEAR reactors
Abstract

Abstract. Angular correlation positron annihilation spectroscopy (AC PAS) has been used for the investigation of reactor pressure vessel (RPV) specimens prepared for the "Extended surveillance specimen program" in the 3rd and 4th units of NPP Jaslovske Bohunice (Slovakia). PAS spectra showed that the changes associated with the effects of neutron irradiation can be well detected. The samples from RPV base material (15Kh2MFA) and weld (Sv 10KhMFT) were measured by angular correlation positron annihilation spectrometer before and after irradiation. Samples have been irradiated in VVER-440 reactor (units 3 and 4 in Bohunice) by neutron fluence from 7.8 x 10[sup 23] m[sup -2] up to 2.5 x 1024 m[sup -2]. Results of PAS measurements are presented and discussed in detail. [ABSTRACT FROM AUTHOR]

Published
2000
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