ANTONIO ALVES DE FREITAS
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Artigo IPEN-doc 23509 Decommissioning of uranium pilot plants at IPEN-CNEN/SP: facilities dismantling, decontamination and reuse as new laboratories for strategic programs2016 - LAINETTI, PAULO E. de O.; FREITAS, ANTONIO A. de; VASQUES, FRANCISCO M.F.; FERREIRA, ROBSON de J.; COTRIM, MARYCEL E.B.; PIRES, MARIA A.F.From beginning of 90’s, the Brazilian nuclear policy has been changed radically. This determined the interruption of most R&D fuel cycle activities and the facilities shutdown at Nuclear and Energetic Research Institute (IPEN). The existence of those facilities also implicated in the need of constant surveillance, representing additional obligations, costs and problems. The reasons to promote the dismantling of the IPEN’s Nuclear Fuel Cycle Pilot Plants elapsed mainly from the need of physical space for new activities, since the R&D in the nuclear fuel cycle area were interrupted. In the last decade, IPEN has changed its “nuclear profile” to a “comprehensive and multidisciplinary profile”. With the end of most nuclear fuel cycle activities, the former facilities were distributed in four different centers. Each center has adopted a different strategy and priority to face the D&D problem. The available resources depend on the specific program in each area’s development (resources available from other sources, not only from Brazilian National Nuclear Energy Commission (CNEN). One of those new activities is the IPEN’s Environmental Program. This paper describes the procedures, problems faced and results related to the reintegration of the former pilot plant areas as new laboratories of the Chemical and Environmental Technology CenterCQMA of the IPEN.Artigo IPEN-doc 20546 Review of brazilian activities related to the thorium fuel cycle and production of thorium compounds at IPEN-CNEN/SP2014 - LAINETTI, PAULO E. de O.; FREITAS, ANTONIO A. de; MINDRISZ, ANA C.Artigo IPEN-doc 08264 Preparation of highly pure thorium nitrate via thorium sulfate and thorium peroxide2001 - ABRAO, A.; FREITAS, A.A.; CARVALHO, F.M.S.A simple alternative and selective method has been proposed for the preparation of thorium nitrate using as raw material a hydrated crystalline technical grade thorium sulfate. This salt was produced industrially [1] from the alkaline chemical processing of monazite sand in S. Paulo. From a crude thorium hydroxide as the raw material containing uranium and rare earth elements was prepared a technical grade thorium sulfate [Th(SO4)2.9H2O]. A typical analysis of this salt had shown the following composition: ThO2 47-53%, R2O3 (rare earth oxides) 0.5-0.9%, and UO3 0.01% and minor amounts of iron, titanium, phosphorus, and silicon oxides. The thorium sulfate is dissolved into water and the thorium peroxide is precipitated from acidic medium by addition of hydrogen peroxide. The thorium peroxide is filtered, washed and finally dissolved with nitric acid. Samples of the thorium peroxide were dried and fired to ThO2 and aliquot of the thorium nitrate solution was evaporated to dryness and calcined to obtain the ThO2. Both ThO2 have high purity (>99.5%). The content of total rare earth elements is very low (0.23% as oxide). Uranium was not detected. The great majority of the RE is precipitated and recovered from the filtrate by oxalic acid.Artigo IPEN-doc 09434 Transformação via peróxido de um hidróxido bruto de tório em nitrato para camisas de lampião2002 - FREITAS, A.A.; CARVALHO, F.M.S.; FERREIRA, J.C.; ABRAO, A.Apresenta-se neste trabalho um processo alternativo para a recuperação e purificação de tório partindo-se de um hidróxido bruto como precursor, cuja composição média é 60,1% em óxido de tório (ThO2), 18,6% em óxidos de terra raras (TR2O3) e impurezas comuns como silício, ferro, titânio, chumbo, sódio e outros. Este material foi produzido industrialmente da monazita processada no Brasil e estocado há alguns anos. Este hidróxido de tório bruto é tratado com ácido nítrico a quente e, depois da digestão e adição de floculante, é filtrado para a separação da fração insolúvel. Usando-se esta solução de nitrato de tório, precipitou-se o peróxido após o ajuste do pH e a adição controlada de peróxido de hidrogênio. O peróxido de tório assim obtido foi dissolvido com ácido nítrico e o nitrato de tório resultante tem qualidade para ser usado na fabricação de camisas para lampião a gás. Os elementos das terras raras são recuperados totalmente no filtrado do peróxido de tório.Artigo IPEN-doc 18078 Properties of nanoparticles prepared from NdFeB-based compound for magnetic hyperthermia application2012 - PERIGO, E.A.; SILVA, S.C.; SOUSA, E.M.B. de; FREITAS, A.A.; COHEN, R.; NAGAMINE, L.C.C.M.; TAKIISHI, H.; LANDGRAF, F.J.G.