TUFIC MADI FILHO
118 resultados
Resultados de Busca
Agora exibindo 1 - 10 de 118
Resumo IPEN-doc 30152 Response of CsI:Pb scintillator crystal to neutron radiation2023 - PEREIRA, MARIA da C.C.; MADI FILHO, TUFIC; BERRETTA, JOSE R.; ALVES, JOAO P. da S.The helium-3 world crisis requires a development of new methods of neutron detection to replace commonly used 3He proportional counters. In the past decades, great effort was made to developed efficient and fast scintillators to detect radiation.[1] These detectors should, then, be carefully characterized both experimentally and by means of advanced simulation code. Ideally, the detector should have the capability to separate neutron and gamma induced events either by amplitude or through pulse shape differences. As neutron sources also generate gamma radiation, which can interfere with the measurement, it is necessary that the detector be able to discriminate the presence of such radiation. Considerable progress has been achieved to develop new inorganic scintillators, in particular increasing the light output and decreasing the decay time by optimized doping. Crystals may be found to suit neutron detection. In this report, we will present the results of the study of lead doped cesium iodide crystals (CsI:Pb) grown in our laboratory, using the vertical Bridgman technique. The concentration of the lead doping element (Pb) was studied in the range 5x10-4M to 10-2M. The crystals grown were subjected to annealing (heat treatment). In this procedure, vacuum of 10-6 mbar and continuous temperature of 350°C, for 24 hours, were employed. In response to neutron radiation, an AmBe source with energy range of 1 MeV to 12 MeV was used. The activity of the AmBe source was 1Ci Am. The fluency was 2.6 x 106 neutrons/second. The operating voltage of the photomultiplier tube was 1300 V; the accumulation time in the counting process was 600 s and 1800 s. The scintillator crystals used were cut with dimensions of 20 mm diameter and 10 mm height. The Monte Carlo method was used to determine the neutron flux arriving in the detector and the calculated values were obtained by means of MCNP code.Resumo IPEN-doc 26679 The growth and scintillation characteristics of lithium doped CsI crystals2011 - PEREIRA, MARIA da C.C.; CARDENAS, JOSE P.N.; MADI FILHO, TUFICInorganic scintillators play an important role in the detection and spectroscopy of gamma and X-rays, as well as in neutrons and charged particles. For a variety of applications, new inorganic scintillation materials are being studied. New scintillation detector applications arise continuously and the interest in the introduction of new fast scintillators becomes relevant. Scintillation crystals based on cesium iodide (CsI) have relatively low hygroscope, easy handling and low cost, features that favor their use as radiation detectors. In this work, lithium doped CsI crystals were grown using the vertical Bridgman technique. In this technique, the charge is maintained at high temperature for 10 h to for the material melting and complete reaction. The temperature gradient 21° C/cm and 1 mm/h descending velocity are chosen as technique parameters. After growth is finished, the furnace is cooled at a rate of 20° C/h to room temperature. The concentration of the lithium doping element (Li) studied was 10-3 M. Analyses were carried out to evaluate the scintillator developed concerning two responses: a) to the gamma radiation, in the energy range of 350 keV to 1330 keV and b) to neutron from AmBe source, with energy range of 1MeV to 12 MeV. T.S. Korolevaa et al [1] describe in their paper about new scintillation materials, for registration of gamma-rays, X-rays, neutrons and neutrinos. One of these materials is 6Li. Lithium can capture neutrons without gamma-ray emission and, thus, reducing the back-ground. The neutron detection reaction is 6Li(n,a)3H with a thermal neutron cross section that 940 barns. In this paper we investigated the feasibility of the CsI:Li crystal as a gamma ray and neutron detector which can be used for monitoring, due to the fact that in our work environment we have two nuclear research reactors, calibration systems and radioisotope production.Artigo IPEN-doc 28850 Determination of the bromine, manganese and antimony in Nicotiana tabacum solanaceae by using the neutron activation analysis technique2022 - MADI FILHO, TUFIC; FERREIRA, ELSON B.; BERRETTA, JOSE R.; PEREIRA, MARIA da C.C.Tobacco addiction has been mentioned as a leading cause of preventable illnesses and premature disability. Smoking is the main cause of lung cancer and one of the factors that most contribute to the occurrence of heart diseases, among others. The herbaceous species Nicotiana tabacum is a plant of the solanaceae family used for tobacco production. Some authors have conducted research about heavy metals and the toxicity of tobacco. It is, frequently, found in low concentrations in the ground, and superficial and underground waters, even though they do not have environmental anthropogenic contributions. However, with the increase of industrial activities and mining together with the agrochemical use of contaminated organic and inorganic fertilizers, an alteration of the geochemical cycle occurs. As a consequence, the natural flow of these materials increases and is released into the biosphere, where they are often accumulated in the superior layer of the ground, accessible to the roots of the plants. During planting and plant development, fertilizers and insecticides, including organochlorines and organophosphates, are used; consequently, the smoke from cigarette smoking presents various toxic substances, such as bromine (Br), manganese (Mn) and antimony (Sb), elements studied in this work. The procedures for the preparation of the samples were carried out in our laboratories and submitted to irradiation with thermal neutrons at Nuclear and Energy Research Institute (IPEN/CNEN-SP), in the Atomic Energy Institute IEA-R1 research reactor. The irradiated material was, then, analyzed by gamma spectrometry, using a high purity germanium detector (HPGe).Capítulo IPEN-doc 28372 Characteristics of PB2+ doped CsI matrix under gamma and neutron excitations2021 - PEREIRA, MARIA da C.C.; MADI FILHO, TUFIC; BERRETTA, JOSE R.; TOMAZ, LUCAS F.In recent years, there has been an increasing interest in finding new fast scintillating material or improve the characteristics of known scintillatorsfor the demand of high energy physics, industrial and nuclear medical applications. Divalent lead ions Pb2+ built in some crystal structures are efficient emission centers and their applications in scintillators wereand arestill the reason of an intensive study of emission properties of different compounds containing these ions. In this context, the crystals of Pb2+ doped CsI matrix were grown by the vertical Bridgman techniqueandsubjected to annealing in vacuum of 10-6 mbar and constanttemperatureof 350°C, for 24 hours, and then they were employed. To evaluate the response of the CsI:Pb scintillator crystal to gamma radiation, radioactive sources of 137Cs (662 keV), 60Co (1173 keV and 1333 keV), 22Na (511 keV and 1275 keV) and 133Ba (355 keV) wereused. The operating voltage of the photomultiplier was 2700 V for the detection of gamma rays and the accumulation time in the counting process was 600 s. The scintillator response to neutron radiation from a radioactive source of AmBe with energy range of 1 to 12 MeV was available. The activity of the AmBe source was 1 Ci Am. The emission ratewas 2.2x 106 neutrons/ second. The operating voltage of the photomultiplier tube was 1300 V. The accumulation time in the counting process was 600 s. With the results obtained, it may be observed that the crystals are sensitive to these radiations.Artigo IPEN-doc 28299 Growth of scintillating bromide-doped cesium iodide crystals for radiation detection2021 - ALVES, J.P.S.; M.FILHO, T.; PEREIRA, M.C.C.Artigo IPEN-doc 27897 Growth and optical characteristics of the CsI:Li scintillator crystal for use as radiation detector2021 - PEREIRA, M.C.C.; FILHO, T.M.; TOMAZ, L.F.; BERRETTA, J.R.Materials capable of converting ionizing radiation into light photons are called scintillators, some have specific efficiencies for certain applications and types of radiation, e.g. gamma, X-ray, alpha, beta and neutrons. CsI:Tl and NaI:Tl crystals are commonly found in the market because they have several applications, but few studies have been done on lithium doped cesium iodide crystal (CsI:Li). The lithium element, in this crystal used as a dopant, is also exploited as a converter for neutron detection, as it has a shock section of 940 barns for thermal neutrons. The study of the CsI:Li crystal is convenient considering the natural abundance of the lithium element with 7.5%, besides the interest in having a low cost national scintillator material, with an opportunity to search for the response of a detector for different types of radiation. The CsI:Li crystal was grown with molar concentration 10-4 to 10-1, using the vertical Bridgman technique. The parameters involved in the growth process were investigated. The transmittance was evaluated in the spectral region from 190 nm to 1100 nm. Luminescence emission spectra for the CsI:Li crystal were evaluated by photometric analysis of the crystal stimulated with a 137Cs (662 keV) source in front of the coupled sample at the monochromator input. The crystals showed maximum luminescence intensity at the wavelength of 420 nm. It was evaluated the response of the scintillators, when excited with gamma radiation of 241Am, 133Ba, 22Na, 137Cs, 60Co and neutron radiation from the AmBe source, with energy range of 1 MeV to 12 Mev.Artigo IPEN-doc 27106 Analysis and construction of the high density storage racks for spent fuel of the research reactor IEA-R12018 - RODRIGUES, ANTONIO C.I.; MADI FILHO, TUFIC; SILVA, DAVILSON G. daThe IEA-R1 research reactor works 40h weekly, with 4.5 Mw power. The storage rack for spent fuel elements has less than half of its initial capacity. Under these conditions, the reactor operating for 32h/week will have 3 spent fuel by year, approximately 3 utilization rate Positions/year; thus, we will have only about six years of capacity for storage. Since the desired service life of the IEA-R1 is at least another 20 years, it will be necessary to increase the storage capacity of spent fuel by doubling the wet storage in the reactor’s pool. 3M’s neutron absorber BoralcanTM was chosen after reviewing the literature about available materials for the construction of a new storage rack. This work presents studies for the construction of new storage racks with double of capacity using the same place of the current ones. Criticality safety analysis was performed with MCNP-5 Monte Carlo code, using two Evaluated Nuclear Data Files (ENDF/B-VI and ENDF/B-VII) in calculations, and subsequently, the results were compared. The full charge of the storage rack with only new fuel elements (maximum reactivity) was considered to calculate the keff. The results obtained in the simulations show that it is possible doubling the storage capacity of the spent fuel elements. Additionally, it complies with safety limits established by International Atomic Energy Agency (IAEA) and Brazilian Commission of Nuclear Energy (CNEN) standards to the criticality criteria (keff <0.95). This is only possible with the use of neutron absorber material.Resumo IPEN-doc 27085 The use of the neutron activation analysis technique to determine heavy metals in Nicotiana tabacum solanaceae2018 - MADI FILHO, TUFIC; FERREIRA, ELSON B.; PEREIRA, MARIA da C.C.; BERRETTA, JOSE R.Tobacco addiction has been mentioned as a leading cause of preventable illnesses and premature disability and tobacco smoking is the main cause of lung cancer and one of the factors that most contribute to the occurrence of heart diseases, among others. The herbaceous species Nicotiana tabacum is a plant of the solanaceae family used for tobacco production. Some authors have researched about heavy metals and the toxicity of tobacco. Heavy metals are frequently found in low concentrations in ground, superficial and underground waters, even though it does not have environmental anthropogenic contributions. However, with the increase of the industrial activities and mining and the agrochemical use of contaminated organic and inorganic fertilizers, an alteration of the geochemical cycle occurs. As a consequence, the natural flow of heavy metals increases the release of these elements into the biosphere, where they are frequently accumulated in the superior layer of the ground, accessible to the roots of the plants. Traces of available heavy metals may be found in surface and subsurface aquatic systems and soils, even when there is no anthropogenic influence on the environment, and they frequently accumulate in the upper layer of the soil, where they are accessible to the roots of the plants. Except for the exclusion species, most plant species that grow on soil contaminated by heavy metals cannot avoid the absorption of these elements, but only limit their translocation. During planting and plant development, fertilizers and insecticides, including organochlorines and organophosphates, are used and the smoke from cigarette smoking presents various toxic substances, including heavy metals such as Chromium (Cr) and Manganese (Mn). The samples preparation procedures were carried out in our laboratories and submitted to the irradiation with thermal neutrons in the IPEN/CNEN-SP, in the IEA-R1 research reactor. The irradiated material was analyzed by gamma spectrometry using a high purity germanium detector (HPGe).Resumo IPEN-doc 27084 Analysis and project of the high density storage racks for spent fuel of the research reactor IEA-R12018 - RODRIGUES, ANTONIO C.I.; MADI FILHO, TUFIC; SILVA, DAVILSON G. daThe IEA-R1 research reactor works 40h weekly with 4.5 Mw power. The storage rack for spent fuel elements has less than half of its initial capacity. Under these conditions (current conditions of reactor operation 32h weekly will have 3 spend fuel by year, then, approximately 3 utilization rate Positions/year). Thus, we will have only about six years of capacity for storage. Whereas the desired service life of the IEA-R1 is at least another 20 years, it will be necessary to increase the storage capacity of spent fuel. Hence, it is necessary to double the wet storage capacity (storage in the IEA-R1 reactor’s pool). After reviewing the literature about materials available for use in the construction of the new storage rack with absorber of neutrons, the BoralcanTM (manufactured by 3M) was chosen, due to its properties. This work presents studies: (a) for the construction of new storages racks with double of the current capacity using the same place of current storages racks and (b) criticality analysis using the MCNP-5 code. Two American Nuclear Data Libraries were used: ENDF / B-VI and ENDF / B-VII, and the results obtained for each data bases were compared. These analyzes confirm the possibility of doubling the storage capacity of fuel elements burned in the same place occupied by the current storage rack attending to the IEA-R1 reactor needs and attending the safety requirements according to the National Nuclear Energy Commission – CNEN and the International Atomic Energy Agency (IAEA). To calculate the keff new fuel elements (maximum possible reactivity) used in full charge of the storage rack were considered. With the results obtained in the simulation we can conclude that doubling the amount of racks for spent fuel elements are complied with safety limits established in the IAEA standards and CNEN of criticality (keff <0.95). It is mandatory to use neutron absorber material.Artigo IPEN-doc 26850 Optical properties and radiation response of Li ion-doped CsI scintillator crystal2019 - PEREIRA, MARIA da C.C.; MADI FILHO, TUFIC; BERRETTA, JOSE R.; TOMAZ, LUCAS F.; MADI, MIRIAM N.Scintillators are materials that convert the energy of ionizing radiation into a flash of light. Due to the existence of different types of scintillators, they are classified into three groups according to their physicochemical characteristics, namely, inorganic, organic and gaseous scintillators. Among the inorganic crystals, the most frequently used as scintillator consist of alkali metals, in particular alkaline iodides. Scintillation materials have many applications, for instance in medical imaging, security, physics, biology, non-destructive inspection and medicine. In this study, lithium doped CsI scintillator crystals were grown using the vertical Bridgman technique. The concentration of the lithium doping element (Li) studied was 10-4 M to 10-1 M. Analyses were carried out to evaluate the developed scintillators with regard to luminescence emission and optical transmittance. The luminescence emission spectra of these crystals were measured with a monochromator for gamma radiation from 137Cs source excitation. The determination of the dopant distribution along the crystalline axis allowed the identification of the region with Li concentration uniformity, which is the region of the crystalline volume indicated for use as a radiation detector. The crystals were excited with neutron radiation from AmBe source, with the energy range of 1 MeV to 12 MeV. As neutron sources also generate gamma radiation, which can interfere with the measurement, it is necessary that the detector be able to discriminate the presence of such radiation. Accordingly, experiments were performed using gamma radiation in the energy range of 59 keV to 1333 keV in order to verify the ability of the detector to discriminate the presence of different types of radiation.