MITSUO YAMAGUCHI
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Artigo IPEN-doc 24804 Thermal hydraulic analysis improvement for the IEA-R1 research reactor and fuel assembly design modification2018 - UMBEHAUN, PEDRO E.; TORRES, WALMIR M.; SOUZA, JOSE A.B.; YAMAGUCHI, MITSUO; SILVA, ANTONIO T. e; MESQUITA, ROBERTO N. de; SCURO, NIKOLAS L.; ANDRADE, DELVONEI A. deThis paper presents the sequence of activities to improve the thermal hydraulic analysis of the IEA-R1 research reactor to operate in safe conditions after power upgrade from 2 to 5 MW and core size reduction from 30 to 24 fuel assemblies. A realistic analysis needs the knowledge of the actual operation conditions (heat flow, flow rates) beyond the geometric data and the uncertainties associated with manufacturing and measures. A dummy fuel assembly was designed and constructed to measure the actual flow rate through the core fuel assemblies and its pressure drop. First results showed that the flow distribution over the core is nearly uniform. Nevertheless, the values are below than the calculated ones and the core bypass flow rate is greater than those estimated previously. Based on this, several activities were performed to identify and reduce the bypass flow, such as reduction of the flow rate through the sample irradiators, closing some unnecessary secondary holes on the matrix plate, improvement in the primary flow rate system and better fit of the core components on the matrix plate. A sub-aquatic visual system was used as an important tool to detect some bypass flow path. After these modifications, the fuel assemblies flow rate increased about 13%. Additional tests using the dummy fuel assembly were carried out to measure the internal flow distribution among the rectangular channels. The results showed that the flow rate through the outer channels is 10% - 15% lower than the internal ones. The flow rate in the channel formed between two adjacent fuel assemblies is an estimated parameter and it is difficult to measure because this is an open channel. A new thermal hydraulic analysis of the outermost plates of the fuel assemblies takes into account all this information. Then, a fuel design modification was proposed with the reduction of 50% in the uranium quantity in the outermost fuel plates. In order to avoid the oxidation of the outermost plates by high temperature, low flow rate, a reduction of 50% in the uranium density in the same ones was shown to be adequate to solve the problem.Artigo IPEN-doc 21604 Neutronic analysis of a U-Mo-Al fuel and europium as burnable poison2016 - MUNIZ, RAFAEL O.R.; SANTOS, ADIMIR dos; YAMAGUCHI, MITSUO; ROSSI, PEDRO C.R.; DOMINGOS, DOUGLAS B.; MURA, LUIS F.; TEIXEIRA e SILVA, ANTONIOArtigo IPEN-doc 09333 Dimensionamento termo-hidraulico de um dispositivo de irradiacao de mini-placas combustiveis para o reator IEA-R12002 - UMBEHAUN, P.E.; ANDRADE, D.A.; TORRES, W.M.; YAMAGUCHI, M.Artigo IPEN-doc 09332 Calculo de temperatura no silicio irradiado no reator IEA-R12002 - UMBEHAUN, P.E.; YORIYAZ, H.; YAMAGUCHI, M.Artigo IPEN-doc 09343 Avaliacao do sistema SCALE 4.4a no Reator IPEN/MB-012002 - ABE, A.; YAMAGUCHI, M.; SANTOS, A.; MENDONCA, A.G.Artigo IPEN-doc 11668 A proposal of a benchmark for Beta sub(eff), Betasub(eff)/Lambda, and Lambda of thermal reactors fueled with slightly enriched uranium2006 - SANTOS, ADIMIR dos; DINIZ, RICARDO; FANARO, LEDA C.C.B.; JEREZ, ROGERIO; ANDRADE e SILVA, GRACIETE S. de; YAMAGUCHI, MITSUOArtigo IPEN-doc 11577 The application of the multiple transient technique for the experimental determination of the relative abundances and decay constants of delayed neutrons of the IPEN/MB-01 reactor2006 - SANTOS, ADIMIR dos; DINIZ, RICARDO; JEREZ, ROGERIO; MAI, LUIZ A.; YAMAGUCHI, MITSUOArtigo IPEN-doc 12260 Qualification program of research reactor fuels manufactured at IPEN-CNEN/SP2008 - TEIXEIRA e SILVA, A.; TERREMOTO, L.A.A.; SILVA, J.E.R.; ALMEIDA, C.T.; DAMY, M.A.; UMBEHAUN, P.E.; YAMAGUCHI, M.In the last years, IPEN-CNEN/SP has developed the project, technical specifications and the manufacturing of U3O8-Al and U3Si2-Al dispersion fuels. Non-destructive analysis techniques have been an important part of the qualification program of these fuels. Today, for utilization in the IEA-R1 research reactor core of IPEN, the U3O8-Al fuel is qualified up to a uranium density of 2.3 gU/cm3 and the U3Si2-Al fuel up to a uranium density of 3.0 gU/cm3. Also, analogous to the qualification process of U3O8-Al and U3Si2-Al fuels, an extended bibliography revision on the irradiation performance of U-Mo alloy dispersed in aluminum matrix (Al) was carried out to establish a set of parameters that could help in the definition of the technical specifications for manufacturing of this type of fuel at IPEN aiming its posterior utilization in the IEA-R1 reactor. The irradiation performance aspects were associated to the neutronic and thermal-hydraulics aspects in order to propose a new core configuration to the IEA-R1 research reactor using U-Mo dispersion fuels. Core configurations using U-10Mo-Al fuels with uranium densities ranging from 3 to 8 gU/cm3 were analyzed with the computational programs CITATION and MTRCR-IEA-R1. Core configurations for fuels with uranium densities ranging from 3 to 5 gU/cm3 showed to be adequate to be used in IEA-R1 reactor and would present a stable in-reactor performance even at high burnup.