The handling of wastes is an eternal problem, all societies are confronted to this issue. Their origins are very diverse, they could come from industrial activities, power production, shops, retail or household for instance. While in developed countries the collection is generally efficient and the disposal safe, the situation in developing countries is different. The municipal budget does not allow the construction of advanced and expensive methods of disposal and the collection suffer from the age of vehicles. This generalisation is nevertheless not totally truth as the situation is extremely depend on the country but also of the city considered. Each city will need to adapt its waste management according to its size, climate, wealth, culture, etc... This report will focus on a Namibian medium town, Tsumeb. The aim is to be able to draw a clear picture of the waste management currently achieved. When the situation is well known, new directions to make Tsumeb refuse management more sustainable can be decided. Implementing progressively an integrated waste management (IWM) is a solution to the waste problem as it is considering economic, social and environmental impacts. A waste characterization was done in order to know the exact amount and composition of the waste generated in Tsumeb to implement afterwards the most suitable solution. The refuse of Tsumeb are surprisingly very similar to high income country. Moreover the stakeholders involved in recycling were investigated. A small informal sector is already making a living by recycling a few materials as glass bottle and cans. There is also a possibility to include extra stakeholder in the recycling process in Tsumeb. Recycling companies, recycling organization or investors are also important stakeholder who can be include in Tsumeb recycling plan. Developing recycling in Tsumeb is facing some challenges but it is also full of opportunities. The main issue when it comes to recycling in Namibia is the long transportation distances what makes it expensive. Furthermore, most of the recovered materials have to be sent in South Africa because Namibia does not possess the necessary industries to recycle paper and glass for instance. On another hand the presence in Tsumeb of a small informal sector already working with waste is promising. The workers could be more organized and the municipality can also helping them with logistic and storage to improve the recycling done. The dump site will also be close within the next years and a new sanitary landfill will be open. It will be a great opportunity to implement a recycling facility on site. Informal workers working on the landfill will be more controlled, to avoid for instance children labour. Some stricter health and safety measure can be decided, to give better working condition to the informal manpower. The development of recycling activities in Tsumeb will be highly beneficial to the community. It will create jobs for the poorest part of the population, decrease the cost of the waste management, reduce the pollution and stimulate the local economy.

Fontes radioativas seladas são largamente empregadas no mundo. A Agência Internacional de Energia Atômica AIEA estima em dezenas de milhões de fontes radioativas no mundo. No Brasil, este número é próximo de 500 mil unidades, considerando-se as fontes de pára-raios e detectores de fumaça. Uma fonte selada pode tornar-se desnecessária, seja devido ao seu decaimento ou outro motivo, sendo classificada como fontes radioativas seladas fora de uso (FRS). No Brasil, a maioria das FRS é considerada rejeito radioativo e são encaminhadas a um dos institutos da CNEN. Sem uma estratégia definida para a deposição das FRS, estas são armazenadas aguardando uma solução. A Gerência de Rejeitos Radioativos - GRR do IPEN-CNEN/SP é o principal centro de recepção desse material e até meados de 2010 havia recebido cerca de 14.000 fontes. O processo proposto para a gestão dessas FRS consiste em retirá-las de suas blindagens originais e transferi-las a outra blindagem, projetada para esse fim. As operações de transferência são realizadas em uma cela quente, garantindo a segurança radiológica. Uma das exigências da CNEN é que todas as fontes seladas sejam caracterizadas. No processo estudado, a avaliação da atividade de cada fonte será feita utilizando-se um detector, do tipo câmara de ionização tipo poço. O presente trabalho tem por objetivo desenvolver uma metodologia para aferir ou determinar a atividade de FRS armazenadas na GRR de acordo com sua geometria e determinar suas incertezas. / Sealed radioactive sources are widely used in many applications of nuclear technology in industry, medicine, research and others. The International Atomic Energy Agency (IAEA) estimates tens of millions sources in the world. In Brazil, the number is about 500 thousand sources, if the Americium-241 sources present in radioactive lightning rods and smoke detectors are included in the inventory. At the end of the useful life, most sources become disused, constitute a radioactive waste, and are then termed spent sealed radioactive sources (SSRS). In Brazil, this waste is collected by the research institutes of the Nuclear Commission of Nuclear Energy and kept under centralized storage, awaiting definition of the final disposal route. The Waste Management Laboratory (WML) at the Nuclear and Energy Research Institute is the main storage center, having received until July 2010 about 14.000 disused sources, not including the tens of thousands of lightning rod and smoke detector sources. A program is underway in the WML to replacing the original shielding by a standard disposal package and to determining the radioisotope content and activity of each one. The identification of the radionuclides and the measurement of activities will be carried out with a well type ionization chamber. This work aims to develop a methodology for measuring or to determine the activity SSRS stored in the WML accordance with its geometry and determine their uncertainties.

Fontes radioativas seladas são largamente empregadas no mundo. A Agência Internacional de Energia Atômica AIEA estima em dezenas de milhões de fontes radioativas no mundo. No Brasil, este número é próximo de 500 mil unidades, considerando-se as fontes de pára-raios e detectores de fumaça. Uma fonte selada pode tornar-se desnecessária, seja devido ao seu decaimento ou outro motivo, sendo classificada como fontes radioativas seladas fora de uso (FRS). No Brasil, a maioria das FRS é considerada rejeito radioativo e são encaminhadas a um dos institutos da CNEN. Sem uma estratégia definida para a deposição das FRS, estas são armazenadas aguardando uma solução. A Gerência de Rejeitos Radioativos - GRR do IPEN-CNEN/SP é o principal centro de recepção desse material e até meados de 2010 havia recebido cerca de 14.000 fontes. O processo proposto para a gestão dessas FRS consiste em retirá-las de suas blindagens originais e transferi-las a outra blindagem, projetada para esse fim. As operações de transferência são realizadas em uma cela quente, garantindo a segurança radiológica. Uma das exigências da CNEN é que todas as fontes seladas sejam caracterizadas. No processo estudado, a avaliação da atividade de cada fonte será feita utilizando-se um detector, do tipo câmara de ionização tipo poço. O presente trabalho tem por objetivo desenvolver uma metodologia para aferir ou determinar a atividade de FRS armazenadas na GRR de acordo com sua geometria e determinar suas incertezas. / Sealed radioactive sources are widely used in many applications of nuclear technology in industry, medicine, research and others. The International Atomic Energy Agency (IAEA) estimates tens of millions sources in the world. In Brazil, the number is about 500 thousand sources, if the Americium-241 sources present in radioactive lightning rods and smoke detectors are included in the inventory. At the end of the useful life, most sources become disused, constitute a radioactive waste, and are then termed spent sealed radioactive sources (SSRS). In Brazil, this waste is collected by the research institutes of the Nuclear Commission of Nuclear Energy and kept under centralized storage, awaiting definition of the final disposal route. The Waste Management Laboratory (WML) at the Nuclear and Energy Research Institute is the main storage center, having received until July 2010 about 14.000 disused sources, not including the tens of thousands of lightning rod and smoke detector sources. A program is underway in the WML to replacing the original shielding by a standard disposal package and to determining the radioisotope content and activity of each one. The identification of the radionuclides and the measurement of activities will be carried out with a well type ionization chamber. This work aims to develop a methodology for measuring or to determine the activity SSRS stored in the WML accordance with its geometry and determine their uncertainties.

Caixas de gordura são dispositivos para retenção de material gorduroso, de origem animal e vegetal, proveniente de pias de cozinha. Sua instalação é exigida por muitos municípios para liberação de ligações de esgoto, visando reduzir as concentrações de óleos e graxas (OG) lançadas no sistema público de coleta e tratamento. Um fator primordial para que estas caixas cumpram suas funções é o estabelecimento de rotinas de manutenção envolvendo inspeção e limpeza periódica. A instalação de locais para recebimento e pré-tratamento dos resíduos retirados das caixas de gordura pode incentivar boas práticas de operação e manutenção destes dispositivos. Diante disso, os objetivos desta pesquisa contemplam a caracterização de resíduos acumulados em caixas de gordura e a avaliação da flotação como alternativa para o seu pré- tratamento, seguido de caracterização do óleo extraído da escuma produzida no flotador. Para tanto, materiais acumulados em caixas de gorduras de fontes distintas foram caracterizados, possibilitando observar grande variação em sua composição, e elevadas concentrações de DBO, DQO, SST e OG. Para verificar o desempenho da flotação visando à redução de OG no efluente pré-tratado, foram realizados ensaios em bancadas e testados quatro produtos químicos coagulantes, sendo eles o PAC, o cloreto férrico, o tanino e o polímero catiônico. Todos apresentaram eficiências elevadas na remoção de OG, porém o produto que apresentou mais vantagens na aplicação foi o polímero. Utilizando o polímero, foram realizados ensaios para verificação do desempenho de várias dosagens associadas a três pH de coagulação diferentes e o melhor desempenho se deu com a aplicação de 30 mg/L de polímero combinada ao pH 4,3, natural da amostra. Foram também realizados ensaios utilizando diferentes relações A/S (7,5/1000, 15/1000 e 22/1000 gar/gsólidos),obtendo-se melhores remoções de OG com a utilização da relação 22/1000 gar/gsólidos. Os materiais flotados obtidos nos ensaios de avaliação da relação A/S foram caracterizados e apresentaram concentrações de ST entre 9,7 e 10,6% e de OG entre 6,1 e 6,7%. Baseado nos resultados obtidos a flotação mostra-se como alternativa com bom desempenho para o pré- tratamento dos resíduos estudados. Para avaliar a dificuldade do manuseio dos resíduos provenientes de caixas de gordura, uma planta piloto foi operada, e entre as principias dificuldades observadas estão o odor intenso, a necessidade de remoção de sólidos grosseiros e de homogeneização do resíduo no tanque de equalização. Visando reaproveitamento do resíduo flotado, foi realizada a extração do óleo com solvente de uma amostra deste material (com teor de sólidos de 8,86%), obtendo a recuperação de 30g óleo/L resíduo com acidez de 13,76 mg KOH/L. A elevada acidez indica a necessidade de purificação, se o objetivo for a produção de biodiesel. / Grease traps are devices that retain animal and vegetal fatty material from kitchen sinks. Many municipalities demand its installation in order to connect house wastewater to the public network, aiming to reduce fat, oil and grease concentration in the collecting and treatment systems. The establishment of maintenance schedule involving inspection and periodic cleaning is a key factor to the right functioning of the device. The existence of appropriated sites to receive and pretreat grease trap wastes may stimulate good practices on maintenance and operation of these devices. In this direction, the objectives of this research are the characterization of grease trap wastes and the evaluation of flotation as an alternative for its pretreatment, followed by characterization of the oil extracted from the scum formed at flotator. Therefore, grease trap wastes from different sources were collected and characterized. It could be observed a wide variation on its composition and high concentrations of BOD, COD, TSS and FOG. Lab scale tests were performed to assess flotation performance to reduce pretreated effluent FOG using four chemical coagulants: PAC, ferric chloride, tannin and cationic polymer. All of them achieved high efficiency on FOG removal, however the product that presented more advantages on application was polymer. More tests were performed using several dosages of polymer associated to three pH coagulation conditions. The combination that resulted in the best efficiency was 30 mg/L of polymer combined to pH 4.3, samples natural pH. Different A/S ratios were also tested (7.5/1000, 15/1000, 22/1000 gair/gsolids), the ratio 22/1000 gair/gsolids presented the best FOG removal efficiencies. Floated material from A/S ratio tests were characterized and presented TS concentrations between 9.7% and 10.6% and FOG was from 6.1% to 6.7%. Based on the obtained results, flotation appears as a high performance alternative for the pretreatment of studied wastes. A pilot plant was operated to evaluate problems related to grease trap waste handling. The main problems were: bad odor, the need of screening and waste homogenization in equalization tank. Aiming to reuse the floated waste, oil was extracted from a sample (8.86% solid content) using solvent, achieving the recovery of 30g oil/L waste with 13.76 mgKOH/L acidity. The high acidity points to the need of purification if biodiesel production is intended.

Caixas de gordura são dispositivos para retenção de material gorduroso, de origem animal e vegetal, proveniente de pias de cozinha. Sua instalação é exigida por muitos municípios para liberação de ligações de esgoto, visando reduzir as concentrações de óleos e graxas (OG) lançadas no sistema público de coleta e tratamento. Um fator primordial para que estas caixas cumpram suas funções é o estabelecimento de rotinas de manutenção envolvendo inspeção e limpeza periódica. A instalação de locais para recebimento e pré-tratamento dos resíduos retirados das caixas de gordura pode incentivar boas práticas de operação e manutenção destes dispositivos. Diante disso, os objetivos desta pesquisa contemplam a caracterização de resíduos acumulados em caixas de gordura e a avaliação da flotação como alternativa para o seu pré- tratamento, seguido de caracterização do óleo extraído da escuma produzida no flotador. Para tanto, materiais acumulados em caixas de gorduras de fontes distintas foram caracterizados, possibilitando observar grande variação em sua composição, e elevadas concentrações de DBO, DQO, SST e OG. Para verificar o desempenho da flotação visando à redução de OG no efluente pré-tratado, foram realizados ensaios em bancadas e testados quatro produtos químicos coagulantes, sendo eles o PAC, o cloreto férrico, o tanino e o polímero catiônico. Todos apresentaram eficiências elevadas na remoção de OG, porém o produto que apresentou mais vantagens na aplicação foi o polímero. Utilizando o polímero, foram realizados ensaios para verificação do desempenho de várias dosagens associadas a três pH de coagulação diferentes e o melhor desempenho se deu com a aplicação de 30 mg/L de polímero combinada ao pH 4,3, natural da amostra. Foram também realizados ensaios utilizando diferentes relações A/S (7,5/1000, 15/1000 e 22/1000 gar/gsólidos),obtendo-se melhores remoções de OG com a utilização da relação 22/1000 gar/gsólidos. Os materiais flotados obtidos nos ensaios de avaliação da relação A/S foram caracterizados e apresentaram concentrações de ST entre 9,7 e 10,6% e de OG entre 6,1 e 6,7%. Baseado nos resultados obtidos a flotação mostra-se como alternativa com bom desempenho para o pré- tratamento dos resíduos estudados. Para avaliar a dificuldade do manuseio dos resíduos provenientes de caixas de gordura, uma planta piloto foi operada, e entre as principias dificuldades observadas estão o odor intenso, a necessidade de remoção de sólidos grosseiros e de homogeneização do resíduo no tanque de equalização. Visando reaproveitamento do resíduo flotado, foi realizada a extração do óleo com solvente de uma amostra deste material (com teor de sólidos de 8,86%), obtendo a recuperação de 30g óleo/L resíduo com acidez de 13,76 mg KOH/L. A elevada acidez indica a necessidade de purificação, se o objetivo for a produção de biodiesel. / Grease traps are devices that retain animal and vegetal fatty material from kitchen sinks. Many municipalities demand its installation in order to connect house wastewater to the public network, aiming to reduce fat, oil and grease concentration in the collecting and treatment systems. The establishment of maintenance schedule involving inspection and periodic cleaning is a key factor to the right functioning of the device. The existence of appropriated sites to receive and pretreat grease trap wastes may stimulate good practices on maintenance and operation of these devices. In this direction, the objectives of this research are the characterization of grease trap wastes and the evaluation of flotation as an alternative for its pretreatment, followed by characterization of the oil extracted from the scum formed at flotator. Therefore, grease trap wastes from different sources were collected and characterized. It could be observed a wide variation on its composition and high concentrations of BOD, COD, TSS and FOG. Lab scale tests were performed to assess flotation performance to reduce pretreated effluent FOG using four chemical coagulants: PAC, ferric chloride, tannin and cationic polymer. All of them achieved high efficiency on FOG removal, however the product that presented more advantages on application was polymer. More tests were performed using several dosages of polymer associated to three pH coagulation conditions. The combination that resulted in the best efficiency was 30 mg/L of polymer combined to pH 4.3, samples natural pH. Different A/S ratios were also tested (7.5/1000, 15/1000, 22/1000 gair/gsolids), the ratio 22/1000 gair/gsolids presented the best FOG removal efficiencies. Floated material from A/S ratio tests were characterized and presented TS concentrations between 9.7% and 10.6% and FOG was from 6.1% to 6.7%. Based on the obtained results, flotation appears as a high performance alternative for the pretreatment of studied wastes. A pilot plant was operated to evaluate problems related to grease trap waste handling. The main problems were: bad odor, the need of screening and waste homogenization in equalization tank. Aiming to reuse the floated waste, oil was extracted from a sample (8.86% solid content) using solvent, achieving the recovery of 30g oil/L waste with 13.76 mgKOH/L acidity. The high acidity points to the need of purification if biodiesel production is intended.

nÃo hà / Observa-se que a qualidade de vida da populaÃÃo està diretamente relacionada com a renda, pois em uma economia de mercado, como à o caso de Fortaleza/CE, existem componentes essenciais para o bem-estar das famÃlias que dependem de sua capacidade de comprar produtos, tais como alimentos, vestuÃrio, etc. O presente estudo visa à determinaÃÃo de uma metodologia compatÃvel com a realidade local da cidade de Fortaleza/CE, para o levantamento de parÃmetros fÃsicos, a saber: taxa de geraÃÃo per capita, composiÃÃo gravimÃtrica e massa especÃfica aparente, de resÃduos sÃlidos com caracterÃsticas domiciliar e comercial. A anÃlise da qualidade e quantidade dos resÃduos gerados pelos domicÃlios e comÃrcios da cidade pautou-se na correlaÃÃo com os indicadores de renda. Esta pesquisa fornece dados prioritÃrios e de extrema importÃncia no planejamento e implementaÃÃo de planos e programas relativos ao gerenciamento ou prestaÃÃo dos serviÃos de resÃduos sÃlidos domiciliares e comerciais, podendo-se concluir que a geraÃÃo de resÃduos guarda uma relaÃÃo direta com os padrÃes de consumo de uma sociedade. Na pesquisa, foram obtidos os seguintes dados para Fortaleza: produÃÃo per capita mÃdia de resÃduos domiciliares: 0,74 kg/hab/dia; massa especÃfica aparente mÃdia: 218 kg/m3; cerca de metade dos resÃduos domiciliares à composta por matÃria orgÃnica compostÃvel (50,3 %). / It can be observed that life quality of the population is directly related to income since in market economies there are essential components for the well being of families which depend from families ability to purchase products such as food, clothing etc. The present study is concerned with the determination of a methodology compatible with the reality of Fortaleza/CE, for the gathering of physical parameters of commercial and household wastes such as: production per capita, waste composition expressed in % of total weight of sample; waste density. The analysis of quality and quantity of the household and commercial wastes generated in Fortaleza is correlated to income indicators. This research provides important data for the design and implementation of plans and programmes of waste management and for the provision of services of household and commercial solid wastes. It can be concluded that generation of waste is directly related to the consumption standards of a society. The research obtained the following data for Fortaleza: per capita production of household wastes: 0,74 kg/hab/day; mass density: 218 kg/m3; around half of the household wastes is organic matter subject to composting (50,3%).

Les activités nucléaires génèrent des déchets radioactifs classés selon leur niveau d’activité et la durée de vie des radioéléments présents. La garantie d’un classement et d’une gestion optimale nécessite une caractérisation précise. Les déchets de moyenne et haute activité, contenant des radioéléments à vie très longue, seront stockés en profondeur pendant plusieurs centaines de milliers d’années, à l’issue desquelles il est nécessaire de pouvoir garantir l’absence de risques pour l’homme et l’environnement, non seulement sur le plan radiologique, mais aussi en ce qui concerne des éléments stables, toxiques du point de vue chimique. Cette thèse concerne la caractérisation par activation neutronique de ces éléments toxiques, ainsi que celle des matières nucléaires présentes dans les colis. Elle a été réalisée dans le cadre d’une collaboration entre le Laboratoire de Mesures Nucléaires du CEA Cadarache, en France, et l’institut de Gestion des Déchets Radioactifs et de Sûreté des Réacteurs du centre de recherche FZJ (Forschungszentrum Jülich), en Allemagne. La première étude a consisté à valider le modèle numérique de la cellule d’activation neutronique MEDINA (FZJ) avec le code de transport Monte Carlo MCNP. Les rayonnements gamma prompts de capture radiative d’échantillons contenant des éléments d’intérêt (béryllium, aluminium, chlore, cuivre, sélénium, strontium et tantale) ont été mesurés et comparés aux simulations avec diverses bases de données nucléaires, permettant d’aboutir à un accord satisfaisant et validant le schéma de calcul en vue des études suivantes. Ensuite, la mesure des rayonnements gamma retardés de fissions induites sur les isotopes 235U et 239Pu a été étudiée pour des fûts de 225 L contenant des enrobés bitumineux ou une matrice béton, représentatifs de déchets produits en France et en Allemagne. Les rendements d’émission des rayonnements gamma retardés de fission d’intérêt, cohérents avec ceux publiés dans la littérature, ont été déterminés à partir des mesures d’échantillons métalliques d’uranium et de plutonium dans la cellule d’activation neutronique REGAIN du LMN. Le signal utile a ensuite été extrapolé par simulation MCNP pour une répartition homogène d’isotopes 239Pu ou 235U dans les matrices considérées, en utilisant le modèle numérique de MEDINA. Des signaux faibles, de l’ordre de 100 coups par gramme d’isotope 239Pu ou 235U, ont été obtenus. Pour le colis d’enrobés bitumineux, le niveau d’irradiation gamma très élevé, dû à une activité en 137Cs de l’ordre de 1 TBq par fût, nécessiterait l’utilisation d’une collimation et/ou d’écrans pour éviter la saturation de l’électronique de mesure, rendant indétectables les rayonnements gamma retardés de fission. Les colis de déchets bétonnés produits en Allemagne présentant un niveau d’activité plus faible, il a été possible d’estimer des limites de détection allant de 10 à 290 g d’isotope fissile 235U ou 239Pu, selon la raie gamma considérée, suite à la mesure du bruit de fond actif dans MEDINA avec une matrice béton maquette. Afin d’améliorer ces performances, le blindage du détecteur germanium de MEDINA a été optimisé à l’aide de simulations MCNP, montrant la possibilité de réduire les bruits de fond gamma et neutron d’un facteur 4 et 5, respectivement. La validation expérimentale de l’efficacité du blindage a été effectuée à partir de configuration simples à implémenter dans MEDINA, confirmant les facteurs de réduction attendus. Un blindage du détecteur optimal permettrait d’améliorer les limites de détection et aussi d’utiliser une source de neutrons d’intensité supérieure, comme un générateur de neutron à haut flux ou un accélérateur linéaire d’électrons avec une cible de conversion appropriée. / Nuclear activities produce radioactive wastes classified following their radioactive level and decay time. An accurate characterization is necessary for efficient classification and management. Medium and high level wastes containing long lived radioactive isotopes will be stored in deep geological storage for hundreds of thousands years. At the end of this period, it is essential to ensure that the wastes do not represent any risk for humans and environment, not only from radioactive point of view, but also from stable toxic chemicals. This PhD thesis concerns the characterization of toxic chemicals and nuclear material in radioactive waste, by using neutron activation analysis, in the frame of collaboration between the Nuclear Measurement Laboratory of CEA Cadarache, France, and the Institute of Nuclear Waste Management and Reactor Safety of the research center, FZJ (Forschungszentrum Jülich GmbH), Germany. The first study is about the validation of the numerical model of the neutron activation cell MEDINA (FZJ), using MCNP Monte Carlo transport code. Simulations and measurements of prompt capture gamma rays from small samples measured in MEDINA have been compared for a number of elements of interest (beryllium, aluminum, chlorine, copper, selenium, strontium, and tantalum). The comparison was performed using different nuclear databases, resulting in satisfactory agreement and validating simulation in view of following studies. Then, the feasibility of fission delayed gamma-ray measurements of 239Pu and 235U in 225 L waste drums has been studied, considering bituminized or concrete matrixes representative of wastes produced in France and Germany. The delayed gamma emission yields were first determined from uranium and plutonium metallic samples measurements in REGAIN, the neutron activation cell of LMN, showing satisfactory consistency with published data. The useful delayed gamma signals of 239Pu and 235U, homogeneously distributed in the 225 L matrixes, were then determined by MCNP simulations using MEDINA numerical model. Weak signals of about one hundred counts per gram of 239Pu or 235U after 7200 s irradiation were obtained. Because of the high gamma emission in the bituminized waste produced in France (about 1 TBq of 137Cs per drum), the use of collimator and/or shielding is mandatory to avoid electronic saturation, making fission delayed gamma rays undetectable. However, German concrete drums being of lower activity, their corresponding active background was measured in MEDINA with a concrete mock-up, leading to detection limits between 10 and 290 g of 235U or239Pu, depending on the delayed gamma line. In order to improve these performances, the shielding of MEDINA germanium detector was optimized using MCNP calculations, resulting in gamma and neutron background reduction factors of 4 and 5, respectively. The experimental validation of the shielding efficiency was performed by implementing easy-to-build configurations in MEDINA, which confirmed the expected background reduction factors predicted by MCNP. Thanks to an optimized detector shielding, it will also be possible to use a higher neutron emission source, like a high flux neutron generator or an electron LINAC with appropriate conversion targets, in view to further reduce detection limits.