GAIANE SABUNDJIAN

Resumo

Possui graduação em Bacharel e Licenciatura Em Física pela Pontifícia Universidade Católica de São Paulo(1978), mestrado em Tecnologia Nuclear / Reatores de Potência pelo Instituto de Pesquisas Energéticas e Nucleares(1981) e doutorado em Engenharia Mecânica pela Escola Politêcnica de São Paulo(1999). Atualmente é TECNOLOGISTA SENIOR do Comissão Nacional de Energia Nuclear. Tem experiência na área de Engenharia Nuclear, com ênfase em Tecnologia dos Reatores. Atuando principalmente nos seguintes temas:Elementos Finitos, Formulação Petrov-Galerkin, Equações de Navier-Stokes, Fluidos Incompressíveis, Funções de Expansão Hierárquicas. (Texto extraído do Currículo Lattes em 13 out. 2021)

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Agora exibindo 1 - 10 de 32
  • Artigo IPEN-doc 30242
    RELAP5 code theoretical simulation of the experiment of natural circulation STAR
    2023 - SABUNDJIAN, GAIANE; BELCHIOR JUNIOR, ANTONIO; MAPRELIAN, EDUARDO
    Studies have been carried out on nuclear reactors with safety characteristics that do not depend on external intervention by operators or even on an external energy source. In this type of reactors, cooling is carried out by natural circulation, both during normal operation and during shutdown. For this reason, the STAR experiment was built in the IEA-R1 research reactor installed at the Institute for Energy and Nuclear Research (IPEN) – Brazil, with the aim of simulating experiments with the RELAP5 code in order to validate its models in two scenarios: total and partial emptying of the STAR. The results obtained with the RELAP5 code were compared to the experimental ones for the two proposed scenarios. These results showed that the mathematical correlations contained in RELAP5 are capable of reliably and safely reproducing the phenomenology of natural circulation in nuclear reactors.
  • Artigo IPEN-doc 27183
    Total and partial loss of coolant experiments in an instrumented fuel assembly of IEA-R1 research reactor
    2020 - MAPRELIAN, EDUARDO; TORRES, WALMIR M.; BELCHIOR JUNIOR, ANTONIO; UMBEHAUN, PEDRO E.; BERRETTA, JOSE R.; SABUNDJIAN, GAIANE
    The safety of nuclear facilities has been a growing global concern, mainly after the Fukushima nuclear accident. Studies on nuclear research reactor accidents such as the Loss of Coolant Accident (LOCA), many times considered a design basis accident, are important for ensure the integrity of the plant. A LOCA may lead to the partial or complete uncovering of the fuel assemblies and it is necessary to assure the decay heat removal as a safety condition. This work aimed to perform, in a safe way, partial and complete uncovering experiments for an Instrumented Fuel Assembly (IFA), in order to measure and compare the actual fuel temperatures behavior for LOCA in similar conditions to research reactors. A test section for experimental simulation of Loss of Coolant Accident named STAR was designed and built. The IFA was irradiated in the IEA-R1 core and positioned in the STAR, which was totally immersed in the reactor pool. Thermocouples were installed in the IFA to measure the clad and fluid temperatures in several axial and radial positions. Experiments were carried out for five levels of uncovering of IFA, being one complete uncovering and four partial uncovering, in two different conditions of decay heat. It was observed that the cases of complete uncovering of the IFA were the most critical ones, that is, those cases presented higher clad temperatures when compared with partial uncovering cases, for the specific conditions of heat decay intensity and dissipation analyzed. The maximum temperatures reached in all experiments were quite below the fuel blister temperature, which is around 500 °C. The STAR has proven to be a safe and reliable experimental apparatus for conducting loss of coolant experiments.
  • Artigo IPEN-doc 26326
    Análise teórico/experimental do fenômeno de circulação natural no circuito de circulação natural do IPEN
    2019 - FRENZEL, LUCAS S.; SABUNDJIAN, GAIANE
    O objetivo deste trabalho é o estudo do fenômeno de circulação natural em circuitos experimentais para aplicação em instalações nucleares. Trabalhos sobre circuitos de circulação natural ganharam força após o acidente de Three Mile Island. Este acidente mostrou que a segurança deste tipo de reator não era suficientemente confiável. Outro ponto importante é relacionado a necessidade de intervenção humana para a entrada de operação dos sistemas de segurança, evidenciando que erros operacionais foram as maiores causas para o acidente de Three Mile Island. Assim, há um crescente interesse da comunidade científica no estudo da circulação natural devido ao seu uso na nova geração de reatores nucleares compactos. O circuito experimental utilizado neste estudo foi reparado/ modernizado, e se encontra no Centro de Engenharia Nuclear do Instituto de Pesquisas Energéticas e Nucleares (CEN-IPEN). Para a realização deste trabalho, foi simulado alguns experimentos com diferentes: níveis de potência e vazão de água no secundário; originando um banco de dados experimentais que é utilizado para validar alguns programas termohidráulicos. Particularmente para este estudo, os resultados experimetais obtidos são comparados com o modelo teórico criado com o código RELAP/MOD3.3 [1]. Os resultados obtidos com o programa são satisfatórios quando comparados com os experimentais.
  • Resumo IPEN-doc 25180
    Experimento de circulação natural
    2018 - FRENZEL, LUCAS S.; SABUNDJIAN, GAIANE
  • Artigo IPEN-doc 24758
    Classification of natural circulation two-phase flow image patterns based on self-organizing maps of full frame DCT coefficients
    2018 - MESQUITA, ROBERTO N. de; CASTRO, LEONARDO F.; TORRES, WALMIR M.; ROCHA, MARCELO da S.; UMBEHAUN, PEDRO E.; ANDRADE, DELVONEI A.; SABUNDJIAN, GAIANE; MASOTTI, PAULO H.F.
    Many of the recent nuclear power plant projects use natural circulation as heat removal mechanism. The accuracy of heat transfer parameters estimation has been improved through models that require precise prediction of two-phase flow pattern transitions. Image patterns of natural circulation instabilities were used to construct an automated classification system based on Self-Organizing Maps (SOMs). The system is used to investigate the more appropriate image features to obtain classification success. An efficient automated classification system based on image features can enable better and faster experimental procedures on two-phase flow phenomena studies. A comparison with a previous fuzzy inference study was foreseen to obtain classification power improvements. In the present work, frequency domain image features were used to characterize three different natural circulation two-phase flow instability stages to serve as input to a SOM clustering algorithm. Full-Frame Discrete Cosine Transform (FFDCT) coefficients were obtained for 32 image samples for each instability stage and were organized as input database for SOM training. A systematic training/test methodology was used to verify the classification method. Image database was obtained from two-phase flow experiments performed on the Natural Circulation Facility (NCF) at Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN), Brazil. A mean right classification rate of 88.75% was obtained for SOMs trained with 50% of database. A mean right classificationrate of 93.98% was obtained for SOMs trained with 75% of data. These mean rates were obtained through 1000 different randomly sampled training data. FFDCT proved to be a very efficient and compact image feature to improve image-based classification systems. Fuzzy inference showed to be more flexible and able to adapt to simpler statistical features from only one image profile. FFDCT features resulted in more precise results when applied to a SOM neural network, though had to be applied to the full original grayscale matrix for all flow images to be classified.
  • Artigo IPEN-doc 24003
    Comparison between RELAP5 versions for a two-phase natural circulation analysis
    2017 - BRAZ FILHO, FRANCISCO A.; RIBEIRO, GUILHERME B.; SABUNDJIAN, GAIANE; CALDEIRA, ALEXANDRE D.
    RELAP5 is one of the most used numerical tools to predict thermal-hydraulic and neutronic phenomena in nuclear reactors. RELAP5-3D is the latest version of this software family, but RELAP5-mod3 is still widely used in Brazilian research institutes and it is also used as benchmark for several nuclear applications. Among these applications, the use of passive heat transfer mechanisms, such as natural circulation, has drawn attention of several studies, especially after the Fukushima-Daiichi accident. Considering this aforementioned aspect, this study proposes a comparison of RELAP5-3D and RELAP5-mod3 versions, focusing on a two-phase natural circulation loop. For comparison purposes, an experimental data set is part of the analysis. Results showed that during the single-phase regime, the temperature difference between versions is negligible. However, when the two-phase flow regime takes place, different wavelengths and amplitudes of flow instabilities were obtained for each version. When compared to the experimental data set, the RELAP5-3D version provided the best prediction results.
  • Artigo IPEN-doc 23156
    Assessment of RELAP5 matrix solvers for a two-phase natural circulation loop
    2017 - BRAZ FILHO, FRANCISCO A.; SABUNDJIAN, GAIANE; RIBEIRO, GUILHERME B.; CALDEIRA, ALEXANDRE D.
    The heat transfer mechanism of natural convection has been extensively studied as a passive heat removal system of new nuclear power plants. Considering this aspect, the main objective of this study is to present an assessment of RELAP5 linear-equation solver under a transient two-fluid model for a two-phase natural circulation loop (NCL). For this assessment, three different approaches of linearequation solvers for the hydrodynamic model are presented: the sparse matrix solver based on the Lower-Upper (LU) decomposition, the Border-Profile Lower Upper (BPLU) solver and the iterative method named Generalized Minimal Residual Method (GMRES). For comparison purposes, an experimental natural circulation loop made of glass tubes and using water as working fluid is analyzed. The onset of nucleate boiling observed during the experiment was predicted by all RELAP5 solvers as well as the representation of flow oscillations along the loop. Furthermore, it was noticed that the choice of the solver algorithm has a strong influence on the prediction of the two-phase natural circulation phenomena, since different wavelengths and amplitudes of flow instabilities were obtained for each approach.
  • Resumo IPEN-doc 22076
    Análise experimental do fenômeno de circulação natural
    2006 - DAMY, OSVALDO L. de; SABUNDJIAN, GAIANE
  • Resumo IPEN-doc 14292
    Analise teorica/experimental do fenomeno de circulacao natural
    2009 - SILVA FILHO, MAURO F. DA; SABUNDJIAN, GAIANE