PEDRO ERNESTO UMBEHAUN

PEDRO ERNESTO UMBEHAUN

(Fonte: Lattes)

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Possui graduação em Engenharia Mecânica pela Fundação Educacional Inaciana Padre Sabóia de Medeiros -FEI (1985), mestrado em Tecnologia Nuclear pela Universidade de São Paulo (2000) e doutorado em Tecnologia Nuclear pela Universidade de São Paulo (2016). Atualmente é Tecnologista Sênior no Instituto de Pesquisas Energéticas e Nucleares da Comissão Nacional de Energia Nuclear. Tem experiência na área de Engenharia Nuclear, com ênfase em Transferência de Calor, atuando principalmente nos seguintes temas: termo-hidráulica de núcleo de reatores nucleares, engenharia nuclear, reatores de pesquisa, e reator nuclear de potência. Atualmente professor convidado na Escola Politécnica da Universidade de São Paulo nas disciplinas Termohidráulica de Sistemas de Geração de Potência I e II. (Texto extraído do Currículo Lattes em 4 maio 2023)

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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.
A CFD numerical model for the flow distribution in a MTR fuel element
2017 - ANDRADE, D.A.; ANGELOA, G.; ANGELO, E.; SANTOS, P.H.G.; OLIVEIRA, F.B.V.; TORRES, W.M.; UMBEHAUN, P.E.; SOUZA, J.A.B.; BELCHIOR JUNIOR, A.; SABUNDJIAN, G.; PRADO, A.C.
Previously, an instrumented dummy fuel element (DMPV-01), with the same geometric characteristics of a MTR fuel element, was designed and constructed for pressure drop and flow distribution measurement experiments at the IEA-R1 reactor core. This dummy element was also used to measure the flow distribution among the rectangular flow channels formed by element fuel plates. A CFD numerical model was developed to complement the studies. This work presents the proposed CFD model as well as a comparison between numerical and experimental results of flow rate distribution among the internal flow channels. Numerical results show that the model reproduces the experiments very well and can be used for the studies as a more convenient and complementary tool.
Experiments of loss of coolant in the IEA-R1 reactor
2017 - MAPRELIAN, E.; TORRES, W.M.; BELCHIOR JUNIOR, A.; UMBEHAUN, P.E.; SANTOS, S.C.; FRANÇA, R.L.; PRADO, A.C.; MACEDO, L.A.; SILVA, A.T. E; BERRETTA, J.R.; SABUNDJIAN, G.
The Loss of Coolant Accident (LOCA) has been considered Design Basis Accident (DBA) for several kind of reactors. The test section for experimental (STAR) for simulation of LOCA, using the Instrumented Fuel Assembly (IFA) EC-208 was designed, assembled, commissioned, and used for the experiments at the IEA-R1 Reactor. The experiments were performed for five different levels of fuel uncovering and two heat decay conditions. The five levels consisted of one total and four partial uncovering of the IFA. The results obtained for each experiment were the section level and 13 IFA temperatures. A data acquisition system was used to record the process parameters. The STAR section has proved to be a very safe and efficient tool for fuel uncovering experiments to obtain thermal-hydraulic data for research and development, and for the data to be compared with safety analysis code calculations.
Heat transfer mode in the core of the Angra 2 nuclear power plant during small break loca obtained with RELAP5 code
2013 - SABUNDJIAN, GAIANE; BELCHIOR JUNIOR, ANTONIO; CONTI, THADEU das N.; ROCHA, MARCELO da S.; ANDRADE, DELVONEI A. de; TORRES, WALMIR M.; MACEDO, LUIZ A.; UMBEHAUN, PEDRO E.; MESQUITA, ROBERTO N. de; LIMA, ANA C. de S.
This work aims to identify the heat transfer mode with RELAP5/MOD3.2.gama code in the core of Angra 2 facility. The postulate accident is the Loss of Coolant Accident (LOCA) in the primary circuit for Small Break (SB), which is described in Chapter 15 of the Final Safety Analysis Report of Angra 2 (FSAR). The accident consists basically of the total break of the cold leg of Angra 2 facility. The rupture area considered was 380 cm2, which represents 100% of the primary circuit pipe °ow area. The Emergency Core Cooling System (ECCS) e±ciency is also tested in this accident. In this simulation, failure and repair criteria are adopted for the ECCS components in order to verify the system operation e±ciency - preserving the integrity of the reactor core and guaranteeing its cooling - as expected by the project design. SBLOCA accidents are characterized by a fast blowdown in the primary circuit to values that activate the low pressure injection system followed by the water injection from the accumulators. The thermal-hydraulic processes inherent to the accident phenomenon, such as hot leg vaporization and consequently core vaporization cause inappropriate °ow distribution in the reactor core that can lead to reduction in the core liquid level, up to the point that the ECCS is able to re°ood it. This work shows the mode numbers and the wall convection heat transfer used in the RELAP5 code that were accessed during the execution of the program. The results showed that the numerical simulations with RELAP5 were satisfactory and that the ECCS worked e±ciently, guaranteeing the integrity of the reactor core.
Commissioning of the star test section for experimental simulation of loss coolant accident using the EC-208 instrumented fuel assembly of the IEA-R1 reactor
2015 - MAPRELIAN, EDUARDO; TORRES, WALMIR M.; PRADO, ADELK C.; UMBEHAUN, PEDRO E.; FRANÇA, RENATO L.; SANTOS, SAMUEL C.; MACEDO, LUIZ A.; SABUNDJIAN, GAIANE
Study of the natural circulation phenomenon for nuclear reactors
2010 - CONTI, THADEU das N.; SABUNDJIAN, GAIANE; UMBEHAUN, PEDRO E.; MESQUITA, ROBERTO N.
Study of the natural circulation phenomenon for nuclear reactors
2010 - CONTI, THADEU das N.; SABUNDJIAN, GAIANE; TORRES, WALMIR M.; MACEDO, LUIZ A.; ANDRADE, DELVONEI A.; UMBEHAUN, PEDRO E.; MESQUITA, ROBERTO N.
Analise teorico/experimental do fenomeno de circulacao natural
2010 - SABUNDJIAN, GAIANE; CONTI, THADEU N.; TORRES, WALMIR M.; MACEDO, LUIZ A.; ANDRADE, DELVONEI A.; UMBEHAUN, PEDRO E.; MESQUITA, ROBERTO N.; SILVA FILHO, MAURO F.; BRAZ FILHO, FRANCISCO A.; BORGES, EDUARDO M.
Thermal hydraulic phenomenology in a natural circulation circuit
2010 - TORRES, WALMIR M.; MACEDO, LUIZ A.; MESQUITA, ROBERTO N.; MASOTTI, PAULO H.F.; SABUNDJIAN, GAIANE; ANDRADE, DELVONEI A.; UMBEHAUN, PEDRO E.
The behaviour of ANGRA 2 nuclear power plant core for a small break LOCA simulated with RELAP5 code
2012 - SABUNDJIAN, GAIANE; ANDRADE, DELVONEI A.; BELCHIOR JUNIOR, ANTONIO; ROCHA, MARCELO da S.; CONTI, THADEU das N.; TORRES, WALMIR M.; UMBEHAUN, PEDRO E.; MESQUITA, ROBERTO N.; MASOTTI, PAULO H.F.