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    617 Alasiminin Kuru Hava Atmosferindeki Yüksek Sicakliklarda Oksidasyon Davranislari
    (Osman SAGDIÇ, 2022) Kaplan, Sevval; Us, Hakan
    Çok yüksek sicaklik reaktörleri (VHTR), elektrik ve hidrojen üretimi konusunda en önemli IV. nesil reaktörlerinden biridir. IV. Nesil reaktörleri, özellikle çok yüksek sicaklik reaktörlerinin (VHTR) yapisinda birçok farkli malzeme düsünülmektedir. Nükleer reaktör aday malzemesi 617 alasiminin yüksek sicakliktaki oksidasyonu farkli sicakliklarda incelenmistir. Kontrollü hava ortamlarinda 24 saat boyunca 800 ° C ile 1000 ° C arasindaki sicakliklarda (100 ° C 'lik adimlarla) izotermal olarak oksidasyon hizi üzerindeki oksidasyon/korozyon etkisinin analizini Termogravimetrik analiz (TGA) ile incelendi. Oksidasyon öncesi ve sonrasi (900 ° C) sicakliklardaki, malzemenin yüzeyleri hakkinda elementel ve kimyasal bilgisi edinmek için yüzey analiz teknigi olan X-ray Fotoelektron Spektroskopisi (XPS) kullanildi ve yüzey morfolojisini incelemek için Atomik Kuvvet Mikroskobu (AFM) kullanilmistir. Oksidasyon davranisi, Wagner'in parabolik oksidasyon kinetik hizi yasasini ile ve Arrhenius denkleminin çözümünü yaparak ilgili verilerle baglantili olarak, aktivasyon enerjisi 800 ° C ile 1000 ° C için 203.91 kJ/mol bulunmustur. TGA sonuçlarina bakildiginda, 800°C ile 1000°C arasinda kütle artisi görülmüstür. XPS tablosundaki verilere göre 617 alasimi numunesinin üzerindeki Cr2O3 tabakasinda sicaklikla birlikte artis görülmüstür. AFM analizi göz önüne alindiginda, sicaklik arttikça açikliklar, ara bosluklar ve tanecikli yapilar sicakliga bagli olarak artis göstermistir. Sekiller, dis oksit ölçeklerinin ve sicakliklarla tane sinirlarinin sürekli büyümesini sirayla göstermektedir. 617 alasiminin oksit morfolojisi ve yapisi, ortamlardan güçlü bir sekilde etkilenmistir. Sicaklik arttikça oksidasyon derinligi artar. Gözenek, bosluk ve tane sinirlarinin olusumuna atfedilen artan oksidasyon sicakliklari, yüksek sicakliklara maruz kalmanin etkisiyle olusmustur.
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    A comparative study of 3D printing and sol-gel polymer production techniques: A case study on usage of ABS polymer for radiation shielding
    (Korean Nuclear Soc, 2024) Ogul, Hasan; Gultekin, Batuhan; Bulut, Fatih; Us, Hakan
    This study focuses on the comparative analysis of ABS polymer samples produced using two distinct manufacturing techniques: 3D printing and the sol -gel methods. In the first approach, ABS polymer was augmented with rare earth oxides, Er 2 O 3 and Gd 2 O 3 , in nano powder form and fabricated into test specimens using 3D printing technology. In the second approach, identical samples were prepared via the sol -gel technique involving mold-based fabrication. Elemental content analysis revealed no significant differences between the samples produced by the two methods. The study proceeds to evaluate the gamma-ray shielding, neutron shielding, temperature resistance, and SEM/EDS pictures of ABS samples generated through both techniques. 3D printing method exhibited more favorable results in terms of structure morphology and thermal stability while there is no significant difference for radiation shielding. The results provide insights into the performance and suitability of each production method for radiation shielding applications. This research not only contributes to enhancing radiation shielding technology but also informs the selection of the most appropriate fabrication method for specific applications in nuclear technologies and diagnostic energy range in medical purposes.
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    Investigation on radiation interactions with some quenched alloys used in nuclear reactors
    (Pergamon-Elsevier Science Ltd, 2025) Ogul, Hasan; Yaz, Abuzer; Us, Hakan; Bulut, Fatih
    This study presents the investigation of the radiation interaction properties for SS304 and Incoloy 800H alloys, which are widely used in PWRs and HTGRs. First of all, theoretical and MC simulation evaluations are performed, then experiments are conducted for further analysis. The findings indicate no significant difference in mass attenuation coefficients (MAC) and gamma-ray radiation protection efficiencies (RPE) between the two alloys. Additionally, both SS304 and Incoloy 800H exhibit similar neutron shielding capabilities, with comparable effective removal cross-sections and numbers of transmitted neutrons at different neutron energies (0.025 eV, 100 eV and 4.5 MeV). The study also examines secondary radiation generated by neutron interactions. The impact of thermal treatment (300 degrees C, 500 degrees C, 700 degrees C and 1000 degrees C) and cooling approaches (quenching and selfcooling) on these alloys were further experimentally examined. Notably, thermal treatment changes the MAC values, particularly at 1000 degrees C, with SS304 showing a more distinct change than Incoloy 800H. Besides, quenched samples have higher MAC values compared to self-cooled samples, especially at 1000 degrees C. However, the microhardness values remained largely unaffected by heat treatment, except at 1000 degrees C, where both alloys exhibited reduced microhardness. The study underscores that there is no significant difference in microhardness between quenching and self-cooling techniques. These results provide valuable insights for enhancing the safety and efficiency of radiation shielding materials in nuclear reactors.
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    Novel 3D-Printed lead-free radiation protection apron in the medical X-ray and thermal neutron energy range
    (Pergamon-Elsevier Science Ltd, 2024) Ogul, Hasan; Gultekin, Batuhan; Yildiz, Hatice; Us, Hakan; Bulut, Fatih
    In this study, we employed 3D printing technology to fabricate poly lactic acid (PLA) polymer samples infused with gadolinium oxide nanoparticles at additive rates of 10% and 20%. The objective was to explore their potential as radiation shielding aprons within the medical X-ray and thermal neutron energy spectrum. To facilitate comparisons, a PLA polymer sample with no additive was also produced. The homogeneity and well-defined structures of the PLA samples were observed using SEM and EDS analyses. Additionally, the excellent thermal stability of the proposed test samples was reported. In terms of gamma-ray shielding, there is a remarkable consistency between experiment, theory and simulation outcomes with a maximum discrepancy of approximately 5%. P-PLA-Gd20 sample exhibits attenuation capabilities against X-rays to a level that could serve as an alternative to lead. Additionally, the thermal and fast neutron attenuation effectiveness of the prepared samples were determined. A shielding effectiveness of 100% against thermal neutrons was achieved using a 10 mm sample thickness and the P-PLA-Gd20 sample. The findings consistently highlight the efficacy of the proposed polymer sample with a 20% gadolinium oxide nanoparticle additive, positioning it as a viable and promising alternative to traditional lead aprons.
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    Öğe
    Production and investigation of 3D printer ABS filaments filled with some rare-earth elements for gamma-ray shielding
    (Korean Nuclear Soc, 2023) Gultekin, Batuhan; Bulut, Fatih; Yildiz, Hatice; Us, Hakan; Ogul, Hasan
    Radiation is the main safety issue for almost all nuclear applications, which must be controlled to protect living organisms and the surrounding materials. In this context, radiation shielding materials have been investigated and used in nuclear technologies. The choice of materials depends on the radiation usage area, type, and energy. Polymer materials are preferred in radiation shielding applications due to their superior characteristics such as chemical inertness, resistivity, low weight, flexibility, strength, and low cost. In the presented work, ABS polymer material, which is possibly the most commonly used material in 3D printers, is mixed with Gd2O3 and Er2O3 nanoparticles. ABS filaments containing these rare-earth elements are then produced using a filament extruder. These produced filaments are used in a 3D printer to create shielding samples. Following the production of shielding samples, SEM, EDS, and gamma-ray shielding analyses (including experiments, WinXCOM, GEANT4, and FLUKA) are performed. The results show that 3D printing technology offers significant enhancements in creating homogeneous and well-structured materials that can be effectively used in gamma-ray shielding applications.