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In the last 15 years, there has been a growing interest in the small modular nuclear reactors (SMR) and their applications. SMRs offer numerous benefits, including inherent safety features. SMRs are under development for all main reactor lines, but an important role for its outstanding safety features will be played by the so-called integral pressurized water nuclear reactors (iPWR). To achieve high proliferation resistance, extended fuel cycles for iPWR have been proposed. Obtaining such a large cycle length, using low fuel enrichment, without shuffle, and with a relatively small core size is a challenge for the neutronic design of the reactor core. In this work, a full-core neutronic computational model based in Serpent code was developed, it permitted to simulate the performance of the proposed reactor core configurations. Different variants of use of integral burnable absorbents in 48-months fuel cycle were studied, and the reactivity worth of the control rod groups was estimated. A fuel cycle extended of more than 1400 EFPDs is reached, and a minimal reactivity penalty was obtained.

Nowadays, 99mTc is the most common radioisotope used in nuclear medicine, with up to 30–40 million procedures worldwide every year. Furthermore, medical diagnostic imaging techniques using 99mTc represent approximately 80% of all nuclear medicine procedures. Currently, 99mTc is almost exclusively produced from the beta-decay of its 66-h parent 99Mo. The 99Mo production in an Aqueous Homogeneous Reactor (AHR) is potentially advantageous because of its low cost, small critical mass, inherent passive safety, and simplified fuel handling, processing, and purification characteristics. This paper studies an AHR conceptual design using low-enriched uranium for the production of 99Mo. Aspects related to the neutronic behavior such as critical height, medical isotopes production, uranium consumption, plutonium production and the reactivity feedback introduced in the solution by the volumetric expansion of the fuel solution were evaluated using the computational code MCNPX version 2.6e. In addition, important reactor kinetic parameters such as the effective delayed neutron fraction, βeff, and mean neutron generation time, Λ, were calculated. A benchmarking exercise was solved using available results of critical experiments performed at the Russian Research Center “Kurchatov Institute”. The neutronic calculations demonstrated that the reactor is able to produce 99 six-day Ci of 99Mo in operation cycles of five days. The reactivity feedbacks introduced by the volumetric expansion of the fuel solution is at about −1460 pcm, which represents approximately the 48% of the planned initial reactivity reserve in the core. The calculated effective delayed neutron fraction and the average mean neutron generation time were 785 pcm and 134.08 µs, respectively.

The nuclear energy is a good alternative to meet the continuous increase in world energy demand. In this pers-pective, VHTRs (Very High Temperature Reactors) are serious candidates for energy generation due to its inherently safe performance, low power density and high conversion efficiency. However, the viability of these reactors depends on an efficient safety system in the operation of nuclear plants. The HTR (High Temperature Reactor)-10 model, an experimental reactor of the pebble bed type, is used as a case study in this work to perform the thermohydraulic simulation. Due to the complex patterns flow that appear in the pebble bed reactor core CFD (Computational Fluid Dynamics) techniques are used to simulate these reactors. A realistic approach is adopted to simulate the central annular column of the reactor core. As geometrical model of the fuel elements was selected the BCC (Body Centered Cubic) arrangement. Parameters considered for reactor design are available in the technical report of benchmark issues by IAEA (TECDOC-1694). We obtain the temperature profile distribution in the core for regimes where the coolant flow rate is smaller than recommended in a normal operation. In general, the temperature distributions calculated are consistent with phenomenological behavior. Even without considering the reactivity changes to reduce the reactor power or other safety mechanisms, the maximum temperatures do not exceed the recommended limits for TRISO fuel elements.

One of the greatest concerns when studying a nuclear reactor is the warranty of safe temperature limits all over the system at all times. The preservation of core structure along with the constraint of radioactive material into a controlled system are the main focus during the operation of a reactor. The purpose of this paper is to present the temperature distribution for a nominal channel of the AP1000 reactor developed by Westinghouse Co. during steady-state and transient operations. In the analysis, the system was subjected to normal operation conditions and then to blockages of the coolant flow. The time necessary to achieve a new safe stationary stage (when it was possible) was presented. The methodology applied in this analysis was based on a two-dimensional survey accomplished by the application of Finite Volume Method (FVM). A steady solution is obtained and compared with an analytical approach that disregards axial heat transport to determine its relevance. The results show the importance of considering axial heat transport in this type of study. A transient analysis shows the behavior of the system when submitted to coolant blockage at channel’s entrance. Three blockages were simulated (10%, 20% and 30%) and the results show that, for a nominal channel, the system can still be considerate safe (there’s no bubble formation until that point).

It is well known that safety in the operation of nuclear power plants is a primary requirement because a failure of this system can result in serious problems to the environment. A nuclear reactor has several systems that help keep it in normal operation, within safety margins. Many of these systems operate in the control of variable quantities in the primary circuit of a reactor. However, nuclear reactors are nonlinear physical systems, and this introduces a complexity in the control strategies. Among several mechanisms in the thermal-hydraulic system of a reactor that actuate as a controller, the pressurizer is the component responsible for absorbing pressure variations that occur in the primary circuit. This work aims at the development of a PID controller (Proportional Integral Derivative) based on fuzzy logic to operate in a pressurizer of a nuclear Pressurized Water Reactor. A Fuzzy Controller was developed using the process of fuzzification, inference, and defuzzification of the variables of interest to a pressurizer, then this controller was coupled to a PID Controller building a PID Controller, but oriented by Fuzzy logic. Subsequently, the PID-Fuzzy Controller was experimentally validated in a Simulation Plant in which transients like those in a PWR were conducted. The PID parameters were analyzed and adjusted for better responses and results. The results of the validation were also compared to simple controllers (on / off).

The Very High Temperature Reactor (VHTR) is one of the candidates of next generation of the nuclear reactors according to IAEA. Predicting the thermohydraulic behavior of High Temperature Reactors (HTR) is an important contribution to the development of this technology. Evaluation of thermohydraulic performance and a comparison with experimental data were proposed to the international research community. The impact of porosity of pebble beds in the thermohydraulic performance in normal operation and under accident condition is the goal of many kinds of research. In this sense, the three-dimensional CFD thermohydraulic simulation of a HTR using ANSYS CFX has been done. The full-scale approach is used to study the influence of different porosity scheme in the main structural materials of the HTR-10 reactor. The porous medium model was used to simulate the pebble bed core zone and the discharge system of pebbles. A comparison with experimental data was made. The steady-state thermohydraulic performance of the HTR-10 reactor at normal operation and anticipated transients without scram (ATWS) tests result, were used. In this work, was possible to estimate the effect of the porosity in the interior regions of the reactor and the impact on the temperature distribution. Finally, the study broadens the knowledge about the impact that the use of variable porosity has on safety analyses in pebble beds reactors.

In an iPWR (integral pressurized water reactor), the pressurizer is located at the top of the reactor vessel; this configuration requires the investigation of the mechanisms adopted for the homogenization of boron. In previous work, three representative experiments were conducted in an experimental installation made of stainless steel with a volumetric scale equal to 1:200, representing one-fourth of the pressurizer of an iPWR. The test facility layout was mounted so that the test section was fed with water or saline solutions with different concentrations, representing scenarios of boration or deboration. To determine the concentration at the inlet and outlet of the test section, samples have been collected every 10 min during the experiments representing some scenarios. The main goal in this work was to investigate how well mixing during boron dilution transients in the pressurizer of a small modular reactor can be modelled accurately by CFD (Computational Fluid Dynamics) codes. Two CFD codes were used, the commercial ANSYS CFX and the open source CFD code OpenFOAM. The use of open source software such as OpenFOAM offers a way to CFD gain acceptance in the licensing. The results of the comparison of simulations with an experiment at the test section were presented and showed a very good agreement. It was verified that deviations are less than 4%, both codes can be used to accurately represent this phenomenon. In order to improve future experiments, the dispersion of the solution inside the test section is studied with the aim to propose positions for sensors. A first simple configuration is proposed, but some further simulations will be done to find an optimum configuration.

Aqueous Homogeneous Reactors (AHRs) or simply solution reactors present nowadays a promising alternative to produce medical isotopes, especially 99Mo. The AHR medical production concept has been proposed to produce medical isotopes directly in the fuel solution, resulting in a potentially competitive alternative in comparison with the solid target irradiation method in heterogeneous reactors. Furthermore, the utilization of AHRs for medical isotopes production has been strengthened because of the successful operation of the ARGUS reactor since 1981 and its conversion to low-enriched uranium (LEU) fuel during 2012-2014. Those successes positively influenced in the decisions to construct a Proof-Of-Concept production site based on the ARGUS operational experience in Sarov (500 km from Moscow) and to restore the Argus-FTI at the Umarov Physical and Technical Institute in Dushanbe, Tajikistan. However, demonstrating the viability of the AHRs for medical isotopes requires solving several significant challenges related with the safe operation of these reactors. Consequently, not only for the design, licensing and safe operation of the AHRs, but also for the prediction of accident scenarios it is very important to be able to simulate and predict the behavior of the fuel solutions through a group of relevant physical parameters. Accordingly, this paper aims to show the advances made to improve the predictive capabilities during the multi-physics computational modeling of AHRs.

The studies summarized in this paper aims to predict the steady state operation of a low-enriched uranium fuel ARGUS type aqueous homogeneous reactor for producing 99Mo to meet the domestic demand of Brazil through a coupled multi-physics (Neutronics + Thermal-hydraulics) evaluation. The coupled multi-physics evaluation included aspects related to the neutronic behavior such as fission induced energy deposition profile, medical isotopes production; and the thermal-hydraulic behavior such as temperature, velocities and gas volume fraction profiles. The methodology followed for the multi-physics and multi-scale coupling of the neutronic and thermal-hydraulic codes (MCNP + ANSYS-CFX), discussed in detail in this paper, represent one of the main outcomes of the current study. The methodology was tested for two different operating configurations of the ARGUS reactor, the original high-enriched uranium configuration used since 1981, and the new low-enriched uranium configuration after the conversion process during 2012-2014. The calculations carried out showed that the reactor, in the studied configuration, is able to produce 246.5 six days Curie of 99Mo in operation cycles of five days. Which is equivalent to more than a third of the estimated Brazilian demand for 2025.

Hydrogen, rather than oil, must be produced in volumes not provided by the currently employed methods. In this work, two high-temperature hydrogen production methods coupled with an advanced nuclear system are presented. A new design of a pebble-bed accelerator nuclear-driven system called TADSEA (Transmutation Advanced Device for Sustainable Energy Applications) was chosen because of the advantages in transmutation and safety. A detailed flowsheet of the high-temperature electrolysis process coupled to TADSEA through a Brayton gas cycle was developed using chemical process simulation software: Aspen HYSYS®. It is obtained 0.1627 kg/s of hydrogen with the model with optimized operating conditions, resulting in an overall process efficiency of 34.51%, a value in the range of results reported by other authors. A conceptual design of a plant using the iodine-sulfur thermochemical water splitting cycle was carried out producing 5.66e-2 kg/s and electric energy in cogeneration. The overall efficiency was calculated performing an energy balance resulting in 22.56%. A brief hydrogen production cost estimation was performed for both methods obtaining 5.96$/kg for the sulfur-iodine (SI) and 4.8 $/kg for the high-temperature electrolysis (HTE) process.

A viabilidade tecnologica de sistemas nucleares depende de um sistema de seguranca eficiente na operacao de suas plantas. Para os promissores reatores de temperatura muito elevada refrigerados a gas com nucleo de leito de bolas, esforcos estao sendo empreendidos com alguns reatores experimentais, a exemplo do modelo HTR (High Temperature Reactor)-10. Neste trabalho, sao realizadas simulacoes termohidraulicas do nucleo do reator de tipo leito de bolas HTR-10, usado como estudo de caso, para investigar, dentre outros fatores, o efeito da reducao da taxa de escoamento do fluido refrigerante no perfil de temperatura do nucleo. Adotou-se tecnicas de dinâmica de fluidos computacional (CFD) com uma abordagem realistica para modelar e simular uma geometria que representa uma coluna da secao central do nucleo do reator. Para simplificar a disposicao dos elementos combustiveis no interior do nucleo, e usado o arranjo cubico centrado no corpo (BCC). Os dados de entrada usados foram extraidos do relatorio tecnico de problemas de benchmark divulgado pela IAEA (TECDOC-1694). Os resultados mostram os perfis de temperatura no interior das bolas de combustivel considerando regimes de perda de refrigerante. As temperaturas maximas alcancadas nao excedem o limite de seguranca projetado para o tipo de combustivel nuclear do reator.

The present work consisted in solving the Navier-Stokes equations, in conservative and structured forms, in the two-dimensional space, employing a finite difference formulation for spatial discretization. It was implemented the Jameson and Mavriplis algorithm to perform the numerical experiments, as well the isotropic scalar linear and nonlinear models of Pulliam, aiming to provide numerical stability to the algorithm. The Backward Euler method for explicit marching in time was also implemented to accelerate the convergence process. The physical problem of subsonic internal flow to a rectangular channel with obstacle configuration was studied. A spatially variable time step is employed aiming to accelerate the convergence to the steady state solution. The main objective was to implement computational tools to the future application in the nuclear sector of numerical techniques widely applied in aeronautical problems, due to the common employed governing equations of the fluid motion, for preliminary studies of density, velocity, pressure, Mach number and energy contours to the flow of gas helium coolant present in the core of the Very High Temperature Gas-cooled Reactor, the VHTGR. A study involving the algorithm's characteristics in relation to the overall quality of the solution is also accomplished. After the simulations, it was found good behavior of Jameson and Mavriplis algorithm, as well as satisfactory performance of the nonlinear Pulliam operator in scheme convergence, showing the nonlinear model as providing better treatment to the numerical solutions obtained.

Sulfur-Iodine thermochemical water splitting cycle coupled is one of the most promising methods for hydrogen production using a nuclear reactor as the primary energy source. However, there are not references in the scientific publications of a test facility that allow to evaluate the efficiency of the overall process. A computational model for the evaluation and optimization of the sulfur-iodine cycle coupled to a very high temperature reactor for nuclear hydrogen production was developed using a chemical process simulator Aspen HYSYS®. Some operational and design parameters of the cycle sections can be optimized in order to obtain the maximum hydrogen production and higher efficiency. The optimized sections of the flowsheet are coupled to a very high temperature nuclear system (TADSEA) through a Brayton gas cycle for power cogeneration. It is proposed a closed flowsheet for the sulfur-iodine thermochemical water splitting cycle coupled to an accelerator driven system, considering a Brayton cycle for the energy production. It is obtained an acceptable value of global efficiency for the initial operating condition. Several parametric studies are conducted using the flowsheet proposed to evaluate important operating parameters in the overall process efficiency.

Small Modular Reactors, SMRs, are variants of compact modular reactors of generation III+ that present attractive features such as simplicity, enhanced safety and are economically competitive. In an iPWR (integral pressurized water reactor), the pressurizer is located at the top of the reactor vessel; this configuration requires the investigation of the mechanisms adopted for the homogenization of boron. The present work shows the contributions to the design of an experimental installation proposed to provide relevant data to study the boron homogenization phenomena in a pressurizer of an SMR. For this, an experimental installation was built with a test section made of stainless steel with a volumetric scale equal to 1:200, representing one-fourth of the pressurizer of an iPWR. The experimental installation has a test section, a heat exchanger, two pumps, five flow meters and three stainless steel tanks with capacities of 0.143, 0.069 and 0.216 m 3 . The test facility layout was mounted so that the test section was fed with water or saline solutions with different concentrations, representing scenarios of boration or deboration. To determine the concentration at the inlet and outlet of the test section, samples have been collected every 10 min during the experiments representing some scenarios (boration/deboration). The electrical conductivity of these samples was determined by a conductivity meter and converted to the concentration of the tracer element (NaCl) used. Three representative experiments were conducted and it was possible to prove the viability of using the experimental setup in a reliable form, for the range of values occurring in the boron homogenization phenomenon in a pressurizer of a compact modular reactor.

The work describes two proposals for hydrogen production using the HTR-PM reactor as an energy source. Both proposals take advantage of the high output temperatures of the 2 × 250 MWth HTR-PM project to increase the efficiency of hydrogen production processes. Two proposals are analysed, the hydrogen production through the Cu-Cl cycle and the high temperature electrolysis process. To evaluate the efficiency of the proposed conceptual designs, two computational models were developed in a chemical process simulator. A determination of the efficiency of the hydrogen production process coupled to the HTR-PM was carried out using the computational model developed. The high temperature electrolysis (HTE) process can produce 0.7821 kg/s of hydrogen with 27.37% of efficiency. The Cu-Cl process, although producing less hydrogen, 0.5637 kg/s, has higher overall efficiency (32.12%) than the HTE, mainly due to less global exergy destruction and higher exergetic efficiency.

The cultivation of the soil causes changes in their physical-hydrics attributes, depending on the management which are submitted. Thus, the objective of this...

The technique of sensibility analysis studies the behavior of the ratio between the variation of output results and the variation of input parameters in general. This study performed in the reactor pressurizer, which is a component responsible for controlling of the pressure inside the vessel, has the fundamental importance in designing the security of any concept of an advanced reactor. In fact, for its feature of passive action of the pressurizer (there is no spray), this analysis becomes a necessary step for safety and performance of the plant. The direct method through code MODPRESS, which represents the pressurizer model of the International Reactor Innovative and Secure (IRIS), has required a huge computational effort. To solve this problem, artificial neural networks (ANNs), beyond faster, has been used to replace the MODPRESS in this article. The ANNs do not require linear behavior of the system and can use both, simulated or experimental data for their training and learning. In order this, we adopted a classical non-supervised training ANN for mapping and forecasting of the pressurized using initially simulated data. In next future, we will incorporate the experimental data from the operation of the CRCN-NE reduced-scale test facility mapping. Moreover, based on the results obtained in this study, one can conclude that the artificial neural networks are presented as an alternative to MODPRESS code, and artificial neural networks are actually a great tool to calculate the sensitivity coefficient.

Small Modular Reactors (SMR) are considered as having several advantages over typical nuclear reactors under various specific conditions. They are thought to be installed in countries with small or medium power grid, in which a large power plant is not necessary or in isolated communities far from distribution centers. A plenty of developing countries are in this situation, so that a significant demand on this type of reactor is expected in a near future. The IRIS reactor is the top-front of SMRs, making its complete development very attractive, since it can fulfill the essential requirements for a future nuclear power plant: better economics, safety-by-design, low proliferation risk and environmental sustainability. IRIS reactor is an integral type PWR in which all primary components are arranged inside the pressure vessel. This configuration involves important changes when compared with a conventional PWR. These changes require several studies to comply with the safe operational limits for the reactor. In light water reactors, a solution of boric acid is used in the coolant of the primary loop to absorb neutrons, aiming to adjust the reactivity of the reactor. A significant decrease in the boron concentration in the core might lead to a considerable power excursion. Several studies on PWR have established correlations between power excursions and deficiencies in homogenization of boric acid diluted in the coolant. The IRIS reactor, due to its integral configuration, does not possess a spray system for boron homogenization which may cause power transients. In this paper, a study has been conducted to develop a dynamic model (named MODIRIS) for transient analysis, implemented in the MATLAB'S software SIMULINK, allowing the analysis of IRIS behavior by considering the neutron point kinetics model for power generation. The methodology is based on generating a set of differential equations of neutronic and thermal-hydraulic balances which describes the dynamics of the primary circuit, as well as a set of differential equations describing the dynamics of secondary circuit. The equations and initialization parameters at full power were inserted into the SIMULINK and the code was validated by comparing with RELAP simulations for a transient of feedwater reduction in the steam generators. Furthermore, the current paper looks for studying and developing a dynamic model for calculating the variations in the boric acid concentration. Then, a simplified model for boron dispersion was implemented into the code MODIRIS to simulate power transients which occur due to variations in the boron concentration in the primary loop of the IRIS reactor. The results for boron concentration, inserted reactivity and steam production showed a good precision and represented the expected behavior very well in the range of operational transients.

Brazil is the world's third largest producer of castor. The crop is mainly cultivated in the northeastern region of the country, but little information is available concerning the diurnal, seasonal and interannual variability of evapotranspiration (ET) and energy exchange of castor crops grown in the region, as well as the water use efficiency and yield. To address this gap in knowledge, the Bowen ratio method was used to measure energy balance and ET in 2004, 2005 and 2007. The experiments were performed in a 4-ha area at the Centro de Ciencias Agrarias, Federal University of Paraiba in Areia in the state of Paraiba, Brazil (6°58′ S, 35°41′ W, elevation 620 m). The study site had a micrometeorological tower with sensors for measuring air temperature and relative humidity located at two heights above castor canopy. Global and net radiation, rainfall, soil heat flux, and stored soil water at 0–1.0 m depth were also measured. Measurements from all of the sensors were recorded by a data logger every 60 s and mean/sum data were logged every 1800 s. Over 3 years, the net radiation (Rn) varied from 53.2 to 461.7 W m−2 and soil heat flux (G) varied from −10.5 to 58.9 W m−2. Variation in energy partitioning into latent (LE) and sensible (H) heat fluxes was mainly associated with changes in stored soil water. H values were higher in 2004 and 2005 (35% and 37% of Rn, respectively) than in 2007 (25% of Rn). Daily ET was very similar in 2004 and 2005 (2.29 and 2.34 mm day−1, respectively) but increased to 3.42 mm day−1 in 2007, mainly due to increased volume and more even rainfall distribution throughout the growing season. Total ET was 299.5, 334.3 and 656.6 mm in 2004, 2005 and 2007, respectively. Castor showed a low yield (60, 324 and 988.3 kg ha−1 in 2004, 2005 and 2007, respectively) and low water use efficiency (0.02, 0.10 and 0.15 kg m−3 in 2004, 2005 and 2007, respectively), especially in drier years, indicating that under short water supply the water use efficiency of castor plants was very low. The seed oil content varied from 33.6% to 49.2% by weight. There was also a strong correlation between castor yield and daily ET (R2 = 0.9433, RMSE = 91.1 kg ha−1), and between castor yield and rainfall (R2 = 0.9902, RMSE = 30.6 kg ha−1).

Resumen en: In the areas of rainfed agriculture it is very important to be able to quantify losses of water by evapotranspiration (ET). The water (WB) and energy (EB...

The reactivity control of a nuclear reactor to pressurized water is made by means of controlling bars or by boron dilution in the water from the coolant of a primary circuit. The control with boron dilution has great importance, despite inserting small variations in the reactivity in the reactor, as it does not significantly affect the distribution of the neutron flux. A simplified experimental bench with a test section manufactured in transparent acrylic, was built in reduced scale as to be used in a boron homogenizing process, simulating an IRIS reactor pressurizer (International Reactor Innovative and Secure). The bench was assembled in the Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE), an entity linked to the Comissao Nacional de Energia Nuclear (CNEN), Recife – PE.

Reference evapotranspiration (ETo) is an important parameter used in numerous applications, such as climatological and hydrological studies, as well as for water resources planning and management. There are several methods to estimate ETo, being that the FAO Penman-Monteith (EToPM) method is considered standard. This method needs many parameters (solar radiation, air temperature, humidity and wind speed), however there are still many uncovered areas, suggesting the need for methods of calculating evapotranspiration based on few meteorological elements, such as air temperature. Therefore, this study aimed to determine the ETo by Hargreaves-Samani method in the experimental watershed of the “Riacho do Papagaio” farm, in county of Sao Joao, in north-eastern Brazil, using data of 2011 and 2012. Reference evapotranspiration estimated by non-calibrated Hargreaves-Samani method (EToHS) was overestimated in all months (RMSE = 1.43 mm·d-1), mainly in months of lower evaporative demand (from May to July). Because of these tendencies, this method cannot be used in its original form to estimate ET for this region; therefore, a calibration of radiation adjustment coefficient (kRs) was performed. The calibrated Hargreaves-Samani method (EToHSc) had better performance (RMSE = 0.52 mm·d-1), being suitable for predicting ETo in this region.

An integral, modular and medium size nuclear reactor, known as IRIS, is being developed by Westinghouse and by research centers. IRIS is characterized by having most of its components inside the pressure vessel, eliminating the probability of accidents. Due to its integral configuration, there is no spray system for boron homogenization, which may cause power transients. Thus, boron mixing must be investigated. The aim of this paper is to establish the conditions under which a test section has to be built for boron dispersion analysis inside IRIS reactor pressurizer. Through Fractional Scaling Analysis, which is a new methodology of similarity, the main parameters for a test section are obtained. By combining Fractional Scaling Analysis with local scaling for the densimetric Froude number and a previously established volumetric scale factor, the values of recirculation orifices, inlet water temperature, time scale factor and recirculation flow for the test section (model) are determined so that boron distribution is well represented in IRIS reactor pressurizer (prototype). Analytical solutions were used to validate the adopted methodology and when the results simulated in the model are compared to those that characterize the prototype, the agreement for both systems is absolute. The thermal power also influences boron distribution inside the test section. This power is determined by condensation laws in the vapor region and by suitable correlations for free convection. The fractions for rising inlet recirculation water enthalpy and vapor formation are also considered.

Nowadays, except for very few imported furnaces, the monitoring of the conversion of the produced plaster at the Pole Plaster of Araripe is not done with aid of online techniques. This research work shows a simulation of operational conditions with an online meter of chemically combined water in plaster, by means of Central Composite Rotatable Designs (CCRD) and nuclear technique of gamma-ray transmission. In the family of central composite rotatable designs, the CCRD is more efficient than the others, regarding uniformity of variances of the points at the same distance from the center of the design. This process is a simulation of operational conditions with an online meter of the chemically combined water in plaster, by means of gamma radiation transmission technique. Such determination can be achieved by the effect caused by the variation of the mass attenuation coefficient of the partially dehydrated material. An Americium-241 gamma source (60 keV) was simulated in the implementation of the Beer–Lambert equation. The nuclear data required for simulation were obtained from XMuDat software, available from the site of the International Atomic Energy Agency. A program in Matlab programming language has demonstrated the possibility of monitoring at all stages of the dehydration process, with measurements of the specific mass of the sample having an estimated error of the order of 1%. To verify the operating conditions suitable for the process, experiments were simulated using a CCRD. The independent variables were the sample thickness and the amount of chemically combined water in plaster. Optimal conditions of the process were determined, which allowed the derivation of a model represented by response surface of the gypsum conversion.

O presente trabalho objetivou comparar o fluxo de calor sensível obtido pelo método do balanço de energia-razão de Bowen (H_B) e pelo método aerodinâmico (H_A), em uma área de 4 ha cultivada com feijão-caupi em Areia-PB (6º 58' 12" S e 35º 42' 15" O, 620 m). Foram coletados dados de saldo de radiação, fluxo de calor no solo, temperatura e umidade do solo, temperatura e umidade relativa do ar, velocidade do vento e precipitação pluvial, os quais eram lidos a cada minuto, e armazenados, em uma central de aquisição de dados, como médias a cada 30 min, com exceção da pluviometria, cujo valor foi totalizado no período. Obteve-se excelente concordância entre H_A e H_B, com um índice "d " de 0,980, um erro padrão (EP) de 14,88 W m-2, e sem diferença significativa entre H_A e H_B, pelo teste t-Student. Deste modo, o método aerodinâmico pode ser usado em conjunto com medidas de saldo de radiação e de fluxo de calor no solo, para se estimar o fluxo de calor latente e, consequentemente, a evapotranspiração da cultura do feijão-caupi, para as condições edafoclimáticas do Brejo Paraibano.

Objetivou-se determinar os componentes do balanço de energia (saldo de radiação, fluxos de calor latente, sensível e no solo), a evapotranspiração (ET) e a eficiência no uso de água (EUA) do feijão caupi cultivado sob condições de sequeiro. O experimento foi conduzido numa área de quatro hectares, localizada no CCA/UFPB, Areia, PB (6º58'12" S e 35º42'15" O e 620 m), durante o período de 22/07/2003 a 17/10/2003. Para a determinação dos componentes do balanço de energia e da ET utilizou-se o método da razão de Bowen, sendo que para isso foi instalada, no centro da área, uma torre micrometeorológica com sensores para medição da temperatura e da umidade relativa, em dois níveis acima do dossel do caupi, além de sensores para a medição do saldo de radiação, da radiação solar global, do fluxo de calor no solo e da precipitação pluvial. Verificou-se que o valor médio da razão saldo de radiação/radiação global (Rn/Rg) foi de 79%, sendo a Rn utilizada, em média, como 65% no fluxo de calor latente (LE/Rn), 23% como fluxo de calor sensível (H/Rn) e 12% como fluxo de calor no solo (G/Rn). Em relação à evapotranspiração, observou-se que o valor total durante o período experimental foi 330,7 mm e o médio de 3,8 mm dia-1. A produção do caupi foi de apenas 206,0 kg ha-1, com uma EUA baixa (0,06 kg m-3), a qual se deu, provavelmente, devido ao déficit hídrico ocorrido na fase reprodutiva. The objective of this study was to assess the energy balance components (net radiation, latent heat flux, sensible heat flux and soil heat flux), evapotranspiration (ET) and water use efficiency (WUE) of cowpea grown under rainfed conditions. The experiment was conducted in a 4 ha area in the CCA, UFPB, belonging to the Municipality of Areia, PB (6º58' S, 35º41' W and 620 m) during the period from July, 22 2003 to October, 17 2003. To determine the energy balance components and ET, it was used the Bowen ratio method, and for that, the area was instrumented with a micrometeorological tower containing sensors for measuring air temperature and relative humidity at two levels above the canopy of cowpea. Measurements of net and global radiation, soil heat flux and rainfall were also made. The average value of the net radiation was 79% of the global solar radiation (Rn/Rg), in which 65% appeared as latent heat flux (LE/Rn), 23% as sensible heat flux (H/Rn) and 12% as soil heat flux (G/Rn). The total and average values for actual evapotranspiration were 330.7 mm and 3.8 mm day-1, respectively. The production of cowpea was only 206.0 kg ha-1 with low WUE (0.06 kg m-3), which occurred probably due to water deficit at reproductive stage.

In this work, a computational model to develop the conceptual design for hydrogen production and seawater desalination based on a modular nuclear reactor as an energy source is presented. The four-step copper-chlorine (Cu-Cl) process is used to produce hydrogen coupled to the gas turbine modular helium reactor (GT-MHR) nuclear system through a Brayton cycle for the electrical energy generation. A fraction of the thermal energy from the GT-MHR system is used to reach and maintain the temperature requirements in the Cu-Cl process. The rejected heat from the oxy-decomposition reaction is used to desalinate seawater through a multi-stage flash (MSF) process. It is employed a chemical process simulator in order to develop a computational model of the proposed system. The global energy and exergy efficiencies of the proposal are 32.47% and 52.20% respectively, producing 0.2190 kg/s of hydrogen and desalinating 4.9492 kg/s of seawater. It is made an estimate of the cost of hydrogen produced using HEEP®, resulting in 2.77 $/kgH2.

About twenty organizations joined in a consortium led by Westinghouse to develop an integral, modular and medium size pressurized water reactor (PWR), known as international reactor innovative and secure (IRIS), which is characterized by having most of its components inside the pressure vessel, eliminating or minimizing the probability of severe accidents. The pressurizer is responsible for pressure control in PWRs. A small continuous flow is maintained by the spray system in conventional pressurizers. This mini-flow allows a mixing between the reactor coolant and the pressurizer water, warranting acceptable limits for occasional differences in boron concentrations. There are neither surge lines nor spray in IRIS pressurizer, but surge and recirculation orifices that promote a circulation flow between primary system and pressurizer, avoiding power transients whether outsurges occur. The construction of models is a routine practice in engineering, being supported by similarity rules. A new method of scaling systems, Fractional Scaling Analysis, has been successfully used to analyze pressure variations, considering the most relevant agents of change. The aim of this analysis is to obtain the initial boron concentration ratio and the volumetric flows that ensure similar behavior for boron dispersion in a prototype and its model.

Resumen pt: A mamona e uma das culturas mais adaptadas a producao de biodiesel na regiao Nordeste, alem de apresentar elevada potencialidade para gerar empregos e fi...

The water balance components (evapotranspiration, variation of the water storage in the soil, deep drainage, capillary rise, rainfall), were determined for an Oxisoil cultivated with cowpea (Vigna unguiculata (L.) Walp.). An automated rainfall gauge and three plots were installed in an area of 4 ha in the CCA/UFPB, Areia-PB (latitude 6o58’12" S, longitude 35o42’15" W, altitude: 620 m). Each plot consisted of an access tube for neutron probe measurements and a set of eight tensiometers. Infiltration tests were performed for the determination of the saturated soil hydraulic conductivity. It was verified that the deep drainage was underestimated, due to the small value (-17.23 mm) found for that soil type. The variation of water storage in the soil followed the variations in rainfall. The evapotranspiration was higher in the periods of increased water availability, with the average value of 4.12 mm d -1 , and the greater water consumption occurred in the reproductive phase.

Os componentes do balanço de energia num solo cultivado com feijão caupi nas condições do Brejo Paraibano, foram determinados numa área de 4 ha do Centro de Ciências Agrárias, da UFPB, localizada no município de Areia, PB (6o 58' S, 35o 41' W e 620 m). Para tal, instalou-se uma torre no centro da área, contendo um pluviógrafo, um piranômetro, um saldo radiômetro e sensores para medida da temperatura e da umidade relativa do ar, em dois níveis acima do dossel da cultura; além disso, dois locais no solo foram instrumentados, cada um com duas sondas térmicas instaladas horizontalmente, nas profundidades de z1 = 2,0 cm e z2 = 8,0 cm, além de uma placa destinada à medida do fluxo de calor no solo, a 5,0 cm. Essas medidas foram armazenadas a cada 30 min, num sistema de aquisição de dados. Verificou-se que o valor médio do saldo de radiação (Rn) foi de 78%, sendo a Rn utilizada, em média, como 71% no fluxo de calor latente (LE), 19% como fluxo de calor sensível (H) e 10% como fluxo de calor no solo (G). A fração do saldo de radiação utilizada como fluxo de calor latente aumentou com a evolução da cobertura do solo pela cultura, enquanto a fração utilizada como fluxo de calor sensível e de calor no solo, diminuiu.

A procedure for filtering the photopeak intensity from the Compton continuum interference is described. A continuum energy region of up to 0.478 and the 0.662 MeV photopeak are well defined in a cesium-137 theoretical spectrum. The filter was applied to a high intensity Compton region in the gamma spectrum obtained by the attenuation measurements in laboratory experiments. A Cs-137 (γ = 0.662 MeV) source, of 4 m Ci, steel tubes and a NaI detector was utilized for measuring the catalyst density in a collimated gamma beam. Such an assembly simulates the measuring conditions for gamma tomography in the riser of a FCC-fluid catalyst cracking unit. A Canberra multichannel data acquisition, records the gamma spectrum whose data file is exported to the Matlab software. Following the spectrum reconstruction, the peak area evaluation in both systems, shows a good agreement. Based on the Fourier transform equation, a filtering method for the photopeak, using Matlab functions, was developed. By means of a lowpass filter that lets the low frequencies pass, but not the high frequencies. The filtering results in a significant reduction in the interference from the Compton effect on the photopeak. For little interference and also for a high continuum background under a nonsymmetrical photopeak the filtering works. After the filtering process the peak becomes fairly similar to a Gaussian curve and the liquid counts are enhanced. The associated standard deviation decreases by a factor of 4, while the resolution of the 0.662 MeV photopeak, is kept within detector characteristics.

A simplified model representing the small reservoir–ebb tide system by a set of different interacting water storage reservoirs has been proposed. The first one is the small reservoir, which represents the main water storage, accumulated during the rainy season. The second reservoir is the ebb tide zone. The link between the two reservoirs, the saturated zone, represents a buffer reservoir for water transfer. The water transfer in the system is described by a set of two balance equations, with two unknowns: water level in the reservoir and piezometric levels in the ebb tide area, both time-dependent. The solution for the set of equations depends on the equivalent saturated hydraulic conductivity of the medium and on atmospheric conditions. In order to evaluate the preferential flow throughout the network of fissures located in the deepest part of the reservoir two approaches have been considered, denominated the equivalent medium and the new model formulation. Four parameters were calibrated by inverse method using data of 70 days during a the monitoring period (23rd July–1st October 1998) and the model was validated for a 243 days period (17th April–16th December 1998) with different measured initial conditions and evaporation flux variation in time. Both the approaches were capable of reproducing the water levels in the reservoir and in the aquifer. In spite of differences in the estimated daily values, the two approaches predicted well-cumulative water flow and preferential flow. This study allowed a better understanding of the water transfer process in the reservoir–ebb tide system during the evaporation period.

Building on the success of the large nuclear plants, small modular reactors (SMRs) offer the potential to expand the use of clean, reliable nuclear energy to a broad range of customers and energy applications. In this work, a model to describe the neutronics parameters of a SMR core that can produce up to 530 MW of thermal power was developed. Using this model, several configurations of fuel enrichment to obtain the most homogeneous distributions of the power inside the fuel assemblies during all the core lifetime were studied. Temperature reactivity coefficients and mass variation of the principal isotopes for the optimised core were calculated. Finally, a model that allows the thermal hydraulic evaluation of the hottest section of the fuel elements was developed. The outlet coolant temperature, temperature distributions in the pins and the radial temperature distribution in the hottest pin were calculated.

Tc99m is a very useful radioisotope, which is used in nearly 80% of all nuclear medicine procedures. Tc99m is produced from 99Mo decay. A potentially advantageous alternative to meeting current and future demand for 99Mo is the use of Aqueous Homogeneous Reactors (AHR). In this paper, a thermal-hydraulics study of the core of a 75 kWth AHR conceptual design based on the ARGUS reactor for 99Mo production is presented. As the ARGUS heat removal systems were designed for working at 20 kWth, the main objective of the thermal-hydraulics study was evaluating the heat removal systems in order to show that sufficient cooling capacity exists to prevent fuel solution overheating. The numerical simulations of an AHR model were carried out using the Computational Fluid Dynamic (CFD) code ANSYS CFX 14. Evaluation shows that the ARGUS heat removal systems working at 75 kWth are not able to provide sufficient cooling capacity to prevent fuel solution overheating. To solve this problem, the number of coiled cooling pipes inside the core was increased from one to five. The results of the CFD simulations with this modification in the design show that acceptable temperature distributions can be obtained.

O saldo de radiacao (Rn) e a energia utilizada em diversos processos que ocorrem no sistema solo-planta-atmosfera, a exemplo da evapotranspiracao; no entanto, sua medicao direta nao esta disponivel para a maioria das estacoes meteorologicas do Brasil. Dessa forma, o presente trabalho objetivou determinar a relacao entre o Rn e a radiacao solar global incidente (Rg) sobre dosseis de caupi e mamona. Os dados de Rn e Rg foram coletados de experimentos realizados durante os anos de 2002 e 2003 (caupi), de 2004 e 2005 (mamona) em Areia-PB (6 o 58 ’ S, 35 o 41 ’ W e 620 m), e de 2009 (mamona) em Garanhuns-PE (8 o 53’ S, 36 o 29’ W e 842 m). Os dados foram integrados durante o periodo diurno, das 6 as 18h, e depois foi obtida a relacao Rn/Rg para cada dia. Obtiveram-se equacoes com elevado R 2 (acima de 0,93), indices d e c (acima de 0,90), e baixo RQME (abaixo de 0,83), indicando boa precisao da estimativa do Rn em funcao do Rg nas culturas do caupi e da mamona. A equacao geral para mamona foi Rn = 0,5965 Rg (R 2 = 0,943) e para caupi foi Rn = 0,7822 Rg (R 2 = 0,976). O Rn, em dosseis de caupi e mamona, pode ser estimado satisfatoriamente a partir da Rg. 800x600 Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";} A B S T R A C T Net radiation (Rn) is the quantity of radiant energy used in many process occurring in the soil-plant-atmosphere continuum, such as evapotranspiration, however, its direct measurement is not available for most weather stations in Brazil. Thus, the objective of this work was to determine the relationship between Rn and incident solar radiation (Rg) in cowpea and castor bean canopies. The Rn and Rg data were collected from experiments conducted during in the years 2002 and 2003 (cowpea), 2004 and 2005 (castor bean) in Areia, PB (6 o 58’ S, 35 o 41’ W e 620 m), and 2009 (castor bean) in Garanhuns-PE (8 o 53’ S, 36 o 29’ W e 842 m). Were performed daily sums of Rn and Rg, from 6 to 18h, and then it was calculated the Rn/Rg ratio for each day. Models with high R 2 (above 0.93), d and c indices (above 0.90) and low RMSE (below 0.83) were obtained in test between measured and estimated values, indicating precision to estimate Rn in cowpea and castor bean canopies as a function of Rg. The general linear function for castor bean and cowpea were Rn = 0.5965 Rg (R 2 = 0.943) and Rn = 0.7822 Rg (R 2 = 0.976), respectively. Net radiation can be satisfactorily estimated from incoming solar radiation for both crops. Key words: Evapotranspiration, Solar Radiation, Vigna unguiculata, Ricinus communis

This paper is part of the ongoing efforts to contribute to the thermal-hydraulic analysis of one of the most promising alternatives to produce medical isotopes and meeting current and future demand for 99Mo: the use of Aqueous Homogeneous Reactors (AHRs). In this paper, the effects of some calculation parameters like mesh refinement, time step size, turbulence models, transient schemes and numerical advection scheme on the computational modelling of key parameters of an AHR steady-state operation have been investigated. For this purpose, a 75 kWth AHR conceptual design based on the ARGUS reactor, six meshes, five time step sizes, three different models for solving flow problems, three numerical advection schemes and the available transient schemes were used in the simulations. The numerical simulations were carried out using the Computational Fluid Dynamic (CFD) code ANSYS CFX 14. The results of the CFD simulations allow developing a detailed and improved CFD model of the AHR core on which the effects of the investigated calculation parameters are quantifiable.

This paper presents a method to classify the current polluted level on insulator surfaces, i.e., to diagnose the operational conditions of the electrical system isolation through pattern recognition techniques using the ultrasonic signals obtained from surface discharges on outdoor insulators. Pattern extraction techniques on the input signals by Artificial Neural Networks were used in order to enable a reliable computation during the training. It can be point out that the area centroid of the ultrasonic signals showed a powerful extraction technique. Here, the Multilayer Perceptron Network was used as a single classifier or as a combination of multiple classifiers. Moreover, the developed networks have one or six neurons in their output layer to represent the classes of pollution. A comparison among the four developed neural net models shows the improvement of the networks with six output neurons and that the use of combined models is a powerful technique for this type of application.