High Thermal Flux Research Articles

Organic matter appraisal of the Lower Eocene (Ypresian) Bou Dabbous Formation in Tunisia

Various facies characterize the Lower Eocene (Ypresian) that had been named formations which include the Bou Dabbous Formation. It is one of the four lateral equivalents of the Metlaoui Group and consists of micrite and marls with abundant planktonic foraminifera (Globigerina). In this paper, we report on the organic matter (OM) analyses of the Bou Dabbous Formation from nine outcrop cross sections in central and northern Tunisia. The total organic carbon (TOC) values and Rock-Eval analysis showed that this formation had preserved type II/III marine OM. Locally, such as at Oueds Sidi Mansour and Bou Jabia, TOC values are very high. These values are reliable to the structural framework (subsiding grabens) during the deposition of the Bou Dabbous Formation. Biomarker (steranes and terpanes) analysis showed that this OM is very rich in these compounds. Our results exposed that the Bou Dabbous Formation OM is represented by an open planctonic to estuarine algal facies with bacterial contribution as revealed by the relative abundance of the C27 (37–43 %), C28 (26–31 %), and C29 (30–34 %) steranes and the dominance of the hopane compounds for all the samples. The good preservation of OM in the Bou Dabbous Formation has been evidenced by the high abundance of gammacerane and the preservation of the C34 and C35 homohopanes in central Tunisia (Oueds Souinia and Sidi Mansour) compared to the northern part (Tellian Atlas). We interpreted that the development of anoxic conditions in central Tunisia had been induced by water stratification of super-salt water under arid and warm climate. These results concord with the structural and the paleogeographic setting where the Bou Dabbous Formation in central Tunisia was deposited in subsiding grabens separated from the open sea by high sills (horst). In northern Tunisia, eastern upwelling waters rich nutriments enhanced primary organic productivity and therefore the development of anoxic conditions. Rock-Eval maximum pyrolysis temperature (T max) values fitting with the interval 425–454 °C show that the OM thermal maturity ranges from immature (central Tunisia), marginally mature (Bizerte region) to the peak of oil generation window (NW Tunisia). We showed that these thermal maturity differentiations were related to the geodynamic evolution that had gone separately central and northern Tunisia. Therefore, the Bou Dabbous formation in central Tunisia had gone subsidence inversion and tendencies to emersion since the Late Eocene epoch and consequently not enough to reach the oil generation window. On the other hand, at the Oligocene–Early Miocene, extensional activity favored dissymmetric subsidence where northern Tunisia (Tellian Atlas) had gone active subsidence associated with high thermal flux in relationship to magmatic activities. Consequently, this feature explains the thermal maturation of the Bou Dabbous OM at this province.

Going further with Fresnel Receiver: New Design Window for Direct Steam Generation

Nowadays, parabolic trough collectors constitute the first concentrating solar thermal technology regarding global installed power. Central receivers and Fresnel receivers appear with smaller value and commercial solar dishes power are practically negligible. Several features have driven parabolic troughs to this first position, but some disadvantages are appearing, i.e. the cost reduction is not as quick as expected, the flexible or ball joints constitute leak problems with high pressure and temperature, and simplification of the mechanical structures is quite difficult. At this point, Fresnel receivers appear as a main competitor with troughs, offering lower cost but also lower efficiency; if the reduction in cost is higher than in efficiency, or if Fresnel efficiency is improved, there are potential facts which can make this simpler technology more competitive than trough collectors.In order to improve the Fresnel capabilities, it could be useful to analyze its optical properties. One important feature of Fresnel solar fields is that receiver and concentrator are mechanically separated, providing the system of a new freedom degree in comparison with trough collectors. This degree of freedom can be used in multi-tube receivers, using the high intensity thermal flux impinging in the receiver to illuminate the tubes where the fluid has higher film coefficient (i.e. where the phase change occurs) to obtain a high thermal efficiency, and using the lower thermal flux for preheating and reheating.The idea presented in this paper is to use a multi-tube Fresnel receiver with an adequate optical system that permits tailoring the thermal flux mapping in the receiver in coherence with the convection process of the thermal fluid. In order to obtain this objective, the mass flow will undergo preheating through the peripheral tubes (where the radiation flux will be lower due to the tracking, mirrors shape and sun shape errors) and will be driven afterwards to the high intensity thermal flux, where boiling (that implies high film coefficient values) takes place. A four tube receiver configuration, according to these ideas, will have two main possibilities. The first one a one-way mass flow through the peripheral tubes (inlets to the receiver) and a second pass inside the internal tubes (outlets). The second possibility assumes the mass-flow inlet receiver through one peripheral tube and the exit at the other one, the mass flow passing consecutively through the other two tubes.

Approaches to multifield numerical analysis for components of the ITER core CXRS upper port plug diagnostics

The core charge exchange recombination spectroscopy (cCXRS) upper port plug diagnostic system serves to control and optimize plasma performance. The system contains a labyrinth of optical mirrors delivering the visible light from the plasma to the end spectrometers. Harsh ITER near plasma environment, resulting in high thermal fluxes and severe electromagnetic (EM) loads, dictates a necessity of a robust design for the plug components.The structural response of the plug components to combined loading coming from different sources has to be calculated and analyzed. The global ANSYS EM model featuring the reference cCXRS layout has been upgraded to be in line with the recent ITER generic upper port plug. Impact of different parameters on the plug EM loading was studied. The dynamic structural behavior of the plug (new baseline layout) under the EM forces has been analyzed. The plug lateral deflection is about 9mm and does not exceed the ITER limit of 12mm.The cooling and supporting system of the cCXRS first mirrors, located near the plasma, have to cope with significant EM loads and high heat fluxes. The engineering ‘express’ approach, that was recently effectively used to calculate the eddy currents and EM forces for the cCXRS fast shutter, has been further validated for the mirrors. The paper outlines approaches to a multifield analysis of the first mirror.

Neutron Imaging of Alkali Metal Heat Pipes

Abstract High-temperature heat pipes are two-phase, capillary driven heat transfer devices capable of passively providing high thermal fluxes. Such a device using a liquid-metal coolant can be used as a solution for successful thermal management on hypersonic flight vehicles. Imaging of the liquid-metal coolant inside will provide valuable information in characterizing the detailed heat and mass transport. Neutron imaging possesses an inherent advantage from the fact that neutrons penetrate the heat pipe metal walls with very little attenuation, but are significantly attenuated by the liquid metal contained inside. Using the BT-2 beam line at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, preliminary efforts have been conducted on a nickel-sodium heat pipe. The contrast between the attenuated beam and the background is calculated to be approximately 3%. This low contrast requires sacrifice in spatial or temporal resolution so efforts have since been concentrated on lithium (Li) which has a substantially larger neutron attenuation cross section. Using the CG-1D beam line at the High Flux Isotope Reactor (HFIR) of Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, the first neutron images of high-temperature molybdenum (Mo)-Li heat pipes have been achieved. The relatively high neutron cross section of Li allows for the visualization of the Li working fluid inside the heat pipes. The evaporator region of a gravity assisted cylindrical heat pipe prototype 25 cm long was imaged from start-up to steady state operation up to approximately 900 °C. In each corner of the square bore inside, the capillary action raises the Li meniscus above the bulk Li pool in the evaporator region. As the operational temperature changes, the meniscus shapes and the bulk meniscus height also changes. Furthermore, a three-dimensional tomographic image is also reconstructed from the total of 128 projection images taken 1.4o apart in which the Li had already cooled and solidified.

Mechanical properties of quartz at the α‐β phase transition: Implications for tectonic and seismic anomalies

The anelastic response of single‐crystal and polycrystalline quartz and quartz‐rich sandstones to applied stress at low frequencies has been investigated by dynamic mechanical analysis and force torsion pendulum measurements. The dynamic modulus was measured on heating and cooling through the α‐β phase transition under shear and bending stress applied at low frequency (~1 Hz). Single crystal quartz shows highly anisotropic properties in both the real and imaginary part of the modulus. Polycrystalline novaculite quartz displays the α‐β phase transition temperatures (Tc) around 8°C higher than seen in single crystal quartz, due to the pinning stress effect of grain boundaries. The properties of the sandstone vary with heating and cooling cycles as the cementation and microfracturing of the grain structure changes at high temperature. The phase transition in quartz is ferrobielastic, and as such energy differences between domains in the transformation microstructure arise under conditions of applied shear stress. Pre‐transition softening and an increase in anelastic loss above Tc are attributed to ferrobielastic switching of incipient domain microstructures that arise in the silica microstructure. The influence of temperature on this microstructure is to induce increased switching of domains as a response to thermal stress inherent in the anisotropic thermal expansion of the polycrystalline structure. These results indicate that ferrobielastic switching in quartz is an important mechanism in controlling changes in mechanical properties. As such, we anticipate that it will induce measurable anomalies in seismic signatures of quartz‐rich portions of the Earth's crust in regions of high thermal flux. The transition may also be responsible for observed seismic velocity reductions and tectonic weakening in western North America and in certain parts of Tibetan plateau.

Bk and Cf chromatographic separation and 249Bk/248Cm and 249Cf/248Cm elemental ratios determination by inductively coupled plasma quadrupole mass spectrometry

The French Atomic Energy Commission has carried out several experiments for the study of minor-actinide transmutation processes in high intensity thermal neutron flux. In this context a Cm sample enriched in 248Cm (∼97%) was irradiated in a thermal neutron flux at the High Flux Reactor (HFR) of the Laue–Langevin Institute (ILL). The precise and accurate determination of Cf isotope ratios and of 249Bk/248Cm and 249Cf/248Cm elemental ratios in the 248Cm irradiated sample is crucial for the calculation of actinide neutron capture cross-sections. This work describes an analytical procedure for the separation and the isotope ratio measurement of Bk and Cf in the irradiated sample. The Bk and Cf separation is based on a lanthanides separation protocol previously developed by the laboratory. Well-defined retention times for Bk and Cf were obtained by coupling the Ionic Chromatography (IC) with an ICP-QMS. All conditions of element separation by IC and the different steps of the analytical protocol in order to obtain the isotopic and elemental ratios are presented. Relative uncertainties of Cf isotopic ratios range from 0.3% to 0.5% and the uncertainty of the 249Bk/248Cm and 249Cf/248Cm elemental ratios are respectively 6.1% and 3.2%. This level of uncertainty for both isotopic and elemental ratios is in perfect agreement with the requirement for transmutation studies.

A core design concept for multi-purpose research reactors

A new core design concept for multi-purpose research reactors is presented. New concept cores using material test reactor (MTR) type fuel are constructed with the edge trimmed in-core irradiation hole. Conventional research reactors have core configurations with a constant assembly pitch. Sizes of in-core irradiation holes are limited to a multiple size of fuel assembly. The new concept enables a core configuration to have different sizes of in-core irradiation holes using the same size of fuel assembly. Two types of cores for multi-purpose research reactors are constructed and the performance results using MCNP calculation are compared. The new compact core for utilizing mainly beam tubes has a larger in-core irradiation hole and gives higher thermal neutron flux at the hole. The maximum thermal flux at the reflector region is almost the same. The new large core for utilizing in-core irradiation holes has small and large holes, while the conventional core has holes of the same size. The small hole is useful for high fast neutron flux and the large hole is useful for high thermal neutron flux. Compared to the conventional cores, the new cores use a smaller fuel assembly, which leads to enhanced safety at a high coolant speed for high power density. Two types of fuel plates are required for the conventional cores, but only one type of fuel plate will do for the new cores. This new design concept gives us several advantages and will be very useful for core design of multi-purpose research reactors.

Devolatilization‐induced pressure build‐up: Implications for reaction front movement and breccia pipe formation

AbstractGeneration of fluids during metamorphism can significantly influence the fluid overpressure, and thus the fluid flow in metamorphic terrains. There is currently a large focus on developing numerical reactive transport models, and with it follows the need for analytical solutions to ensure correct numerical implementation. In this study, we derive both analytical and numerical solutions to reaction‐induced fluid overpressure, coupled to temperature and fluid flow out of the reacting front. All equations are derived from basic principles of conservation of mass, energy and momentum. We focus on contact metamorphism, where devolatilization reactions are particularly important owing to high thermal fluxes allowing large volumes of fluids to be rapidly generated. The analytical solutions reveal three key factors involved in the pressure build‐up: (i) The efficiency of the devolatilizing reaction front (pressure build‐up) relative to fluid flow (pressure relaxation), (ii) the reaction temperature relative to the available heat in the system and (iii) the feedback of overpressure on the reaction temperature as a function of the Clapeyron slope. Finally, we apply the model to two geological case scenarios. In the first case, we investigate the influence of fluid overpressure on the movement of the reaction front and show that it can slow down significantly and may even be terminated owing to increased effective reaction temperature. In the second case, the model is applied to constrain the conditions for fracturing and inferred breccia pipe formation in organic‐rich shales owing to methane generation in the contact aureole.

Expendable High Energy Density Thermal Management Material: Ammonium Carbamate

I NCREASING power loads for various electronic devices have created a demand for novel thermal management (TM) technologies that allow these devices to operate in their ideal temperature ranges in order to ensure device efficiency and lifetime. Most electronic devices need to operate between 20 and 100 C. Cooling these devices with air or conventional liquid coolants can be energy intensive, require a large TM system, or even be impossible when dealing with high thermal fluxes [1]. Traditionally, cooling in these devices is accomplished using the sensible heat associated with a temperature change of a fluid such as air or water. Air cooling systems are the simplest but cannot handle high thermal loads. The higher specific heat of water allows it to handle greater thermal loads than air. Nevertheless, the specific heat of water is low relative to that of its phase changes, which cannot be used for the temperature range of interest. Since latent heats accompanying phase changes are fundamentally higher than sensible heats on a mass basis, phase change materials (PCMs) have garnered intense interest for TM. Additionally, as PCMs offer the ability to maintain a constant temperature, they are being explored for the temperature range of interest. One class of PCMs being explored for this temperature range is graphitic or metallic foams impregnated with paraffin wax [1–6]. Waxes are advantageous since their melting temperatures can be tuned between 5 and 95 C, but they suffer from low specific energy densities on the order of 200 kJ=kg for the purematerial. The systemlevel properties (specific energy density and thermal power) are much lower since the low thermal conductivity of waxes, which is around 0:2 W=m K, necessitates system-level architectures that enhance the heat transfer rate in order to achieve a practical thermal power rating [7]. Much of the work in using waxes as PCMs has concentrated on incorporating them into thermally conductive carbon or metal matrices in order to improve the thermal conductivity. This has shown success but lowers the system-specific properties to less than half those of the neat waxes [1,2,4,8]. TM systems based on chemical reactions, rather than sensible or latent heats, are another class of materials being explored. In principle, chemical reaction systems can yield the highest gravimetric TM capacities since the energies associated with changes in chemical bonding are intrinsically greater than those of physical phase changes. One class of chemical reaction systems involves a solid that exothermically reacts with a gas to form a complex. The complex can then be disassociated in an endothermic process, which can serve as a heat sink.Ammoniates are representative of this type of system. They work by using ammonia gas and a salt (normally period 4, 5, and 6 metal chlorides) to form complexes with ammonia [9–11]. The problem with these systems is that they require high pressures and large amounts of the salts, which lead to low specific properties and makes them unsuitable for applications in which specific energy and specific thermal power are key drivers at the system level. Metal hydride-based chemical reaction systems function by using hydrogen gas that exothermically reacts with metals to form a metalhydrogen complex from which the hydrogen can then be endothermically released. Metal hydrides can have very high gravimetric thermal energy densities, and there are many possible metal-hydrogen storage material systems that have been reported elsewhere [12,13]. Much of the research into metal hydrides is being conducted for the purpose of hydrogen storage in fuel cell vehicles. This application requiresminimization of the thermal load associated with the sorption process. However, metal hydride systems with a high thermal load may be good candidates for TM. The Mg=MgH2 system is well characterized with a thermal storage density of 1850 kJ=kg, while LiAlH4 has been reported to have the extremely Presented as Paper 2011-3950 at the 42nd AIAA Thermophysics Conference, Honolulu, HI, 27–30 June 2011; received 21 June 2011; revision received 11 August 2011; accepted for publication 5 September 2011. This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 percopy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0887-8722/12 and $10.00 in correspondence with the CCC. Research Engineer, Materials and Manufacturing Directorate, Thermal Sciences and Materials Branch, 2977 Hobson Way. Principle Research Chemist, Materials and Manufacturing Directorate, Thermal Sciences and Materials Branch, 2977 Hobson Way (Corresponding Author). Professor of Chemistry, Department of Science and Mathematics, 251 N. Main Street. JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER Vol. 26, No. 2, April–June 2012

Design and Study of a Phase Change Micro-Channel Heat Sink

It is difficult to cool high thermal flux electronics by traditional methods such as air cooling, common liquid cooling and so on. However, vapor compressor refrigeration system is an efficient approach to solve this problem. Heat sink is important equipment in system, so the goal of this paper is to design a heat sink which is similar to an evaporator in vapor compression system with head load 100W. Mathematical model of heat sink is set up. Different heat flux, pressure drop, heat transfer area and weight with different micro-channel width are obtained finally.

Architecture and phases composition of suspension plasma sprayed alumina–titania sub-micrometer-sized coatings

Sub-micrometer-sized Al 2O 3–TiO 2 plasma-sprayed coatings exhibit superior performances compared to micrometer-sized ones. Two routes can be implemented to manufacture such finely structured coatings: i) spraying micrometer-sized agglomerates of nanometer-sized particles which results in a two-scale coating architecture and ii) spraying a suspension of sub-micrometer-sized particles (suspension plasma spraying, SPS). SPS was implemented in this study and Al 2O 3-base coatings with 13 and 60 wt.% of titania, respectively, were manufactured by spraying a suspension made of a mixture of Al 2O 3 and TiO 2 particles both of 300 nm, average diameter. Coating structural features and phase contents were studied. Results show that the coatings exhibit a very fine lamellar structure with a homogeneous repartition of Al and Ti. Complex phases, made of intermediate Al, Ti, and O oxides, have been also identified. Indeed, coatings formation results from rapid solidification rates and high transient thermal fluxes imparted by the plasma flow to the substrate due to the short spray distance encountered in SPS (in the order of 30 mm) requested by the small kinetics and thermal inertia of sub-micrometer-sized particles.

Research on Thermocouple Embedded Theory for Thermal State of CC Mould Copper Plate with High Casting Speed

High casting speed would change the thermal state of the mould copper plate, The coupled visco-elasto-plastic FEM models have been presented for thermal process analysis of steel shell and the mould copper plates. With the understanding to the mould thermal state for different casting speed, the characters of mould copper plate thermal flux is obtained. It is shown that, the highest thermal flux zone is getting downward with casting speed increasing, and it would also make harder for breakout signals catching.

Recent Developments on Micrometric Fission Chambers Dedicated for High Neutron Fluxes

With the development of innovative nuclear systems and new generation neutron sources, the nuclear instrumentation should be adapted. Since several years, we developed microscopic fission chambers to study the transmutation of minor actinides in high thermal-neutron fluxes. The recent developments done to fulfill the drastic conditions of irradiations are described in this paper together with the feedback from the measurements. Two installations were used: the HFR of the ILL for its high thermal neutron flux and the MEGAPIE target which was the first liquid Pb-Bi spallation target in the MW range.

Neutron Bound β-Decay-BOB

The bound neutron β-decay(BOB) into a hydrogen atom and an electron antineutrino is investigated. The hyperfinestate population of the monoenergetic hydrogen atoms yields the neutrino left-handedness or a possible right-handed admixture and possible small scalar and tensor contributions to the weak force. The BOB H(2s) hyperfine states are separated with a Lamb shift spin filter. The H(2s) atoms are detected either by quenching yielding Lyman-α photons, or ionizing or charge exchanging into protons and H-, respectively. A first experiment is planned at the FRM2 high thermal neutron flux beam reactor SR6 through-going beam pipe. The neutron and ray background suppression with absorbing traps between SR6 and the experiment has been simulated using MCNP4 and GEANT4. The Lyman-α photon background produced by protons hitting the vacuum chamber wall was measured in a mockup setup.

Interface delamination of the thermal barrier coating subjected to local heating

To investigate the possible failure modes of the thermal barrier coating (TBC) used to protect the scramjet combustion chamber, the local heating via laser beam irradiation was utilized to simulate the service condition of high thermal flux and high temperature gradient. Firstly, the experimental method and process were described and the typical fracture morphology of the TBC under test were provided. Then, the theoretical and finite element modeling were carried out to study the temperature, deformation and stresses of the specimen when the top ceramic coat was subjected to local heating, and to demonstrate the mechanism on the failure of the TBC. It is revealed that the interface delamination shall appear and ultimately lead to the failure of the TBC under such thermal loading of local quick heating. According to the outcome of this study, the driving force of the interface delamination is influenced greatly by the key structural parameters and performance matching. Moreover, by utilizing the rules of the effects of these parameters on the fracture driving force, there is some possibility for the designer to optimize the performances of the TBC.

Detection of SNM by delayed gamma rays from induced fission

The Pulsed Neutron Interrogation Test Assembly (PUNITA) is an experimental device for research in NDA methods and field applicable instrumentation for nuclear safeguards and security applications. PUNITA incorporates a standard 14-MeV (D-T) pulsed neutron generator inside a large graphite mantle. The generator target is surrounded by a thick tungsten filter with the purpose to increase the neutron output and to tailor the neutron energy spectrum . In this configuration a sample may be exposed to a relatively high average thermal neutron flux of about (2.2±0.1)×10 3 s −1 cm −2 at only 10% of the maximum target neutron emission . The sample cavity is large enough to allow variation of the experimental setup including the fissile sample, neutron and gamma detectors , and shielding materials. The response from SNM samples of different fissile material content was investigated with various field-applicable scintillation gamma detectors such as the 3×2 in. LaBr 3 detector. Shielding in the form of tungsten and cadmium was applied to the detector to improve the signal to background ratio. Gamma and neutron shields surrounding the samples were also tested for the purpose of simulating clandestine conduct. The energy spectra of delayed gamma rays were recorded in the range 100 keV–9 MeV. In addition time spectra of delayed gamma rays in the range 3.3–8 MeV were recorded in the time period of 10 ms–120 s after the 14-MeV neutron burst. The goal of the experiment was to optimize the sample/detector configuration including the energy range and time period for SNM detection. The results show, for example, that a 170 g sample of depleted uranium can be detected with the given setup in less than 3 min of investigation. Samples of higher enrichment or higher mass are detected in much shorter time.

The dose comparison between the THOR and HFR epithermal neutron beams

Abstract This study is a part of the beam comparison campaign, inter-center dose comparison, between boron neutron capture therapy facilities at the Tsing Hua Open-pool Reactor and the High Flux Reactor. The clinical information exchange can improve the dosimetry uncertainty for medical physics in a mixed field. The method of paired Mg(Ar) and TE(TE) ionization chambers was used to determine the gamma-ray and neutron dose rates. Furthermore, activation foils, including gold, copper, and manganese, were employed to estimate the thermal and epithermal neutron fluxes. Measurements were performed free in air and also in a PMMA phantom. All the chambers were calibrated using a 60Co primary standard source at the Institute of Nuclear Energy Research, Taiwan. Spectrum dependent neutron sensitivity of TE(TE) chamber is one of the important parameters to evaluate dose components. The requested neutron spectra were calculated by the Monte Carlo code MCNP. The measured thermal neutron fluxes, gamma-ray and neutron dose rates of the THOR beam in the phantom were 2.6, 2.2, and 2.1 times of the HFR beam at 2.5-cm depth, respectively. The higher thermal neutron flux and neutron and gamma-ray dose rates are due to the higher epithermal neutron beam intensity of the THOR.

Accurate determination of Curium and Californium isotopic ratios by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) in 248Cm samples for transmutation studies

Abstract The French Atomic Energy Commission has carried out several experiments including the mini-INCA (INcineration of Actinides) project for the study of minor-actinide transmutation processes in high intensity thermal neutron fluxes, in view of proposing solutions to reduce the radiotoxicity of long-lived nuclear wastes. In this context, a Cm sample enriched in 248Cm (∼97%) was irradiated in thermal neutron flux at the High Flux Reactor (HFR) of the Laue-Langevin Institute (ILL). This work describes a quadrupole ICP-MS (ICP-QMS) analytical procedure for precise and accurate isotopic composition determination of Cm before sample irradiation and of Cm and Cf after sample irradiation. The factors that affect the accuracy and reproducibility of isotopic ratio measurements by ICP-QMS, such as peak centre correction, detector dead time, mass bias, abundance sensitivity and hydrides formation, instrumental background, and memory blank were carefully evaluated and corrected. Uncertainties of the isotopic ratios, taking into account internal precision of isotope ratio measurements, peak tailing, and hydrides’ formations ranged from 0.3% to 1.3%. This uncertainties’ range is quite acceptable for the nuclear data to be used in transmutation studies.

Rapid injection molding of high-aspect-ratio nanostructures

The authors have developed a method for thermal injection molding of high-aspect-ratio nanostructures involving dynamic heating of the mold surface. The conventional injection molding of nanostructures is difficult to achieve because of the rapid formation of a solidified layer caused by high thermal flux from the melted polymer to the cold mold. In our system, a nanostructured mold surface was heated during polymer filling and then immediately cooled by the mold bases, which are kept at a lower temperature. Using polystyrene, we demonstrated the replication of line-and-space (pitch: 800 nm, depth: 400 nm) and cone patterns (pitch: 200 nm, depth: 400 nm) with a cycle time of less than 15 s.

Optimization of the core configuration design using a hybrid artificial intelligence algorithm for research reactors

To successfully carry out material irradiation experiments and radioisotope productions, a high thermal neutron flux at irradiation box over a desired life time of a core configuration is needed. On the other hand, reactor safety and operational constraints must be preserved during core configuration selection. Two main objectives and two safety and operational constraints are suggested to optimize reactor core configuration design. Suggested parameters and conditions are considered as two separate fitness functions composed of two main objectives and two penalty functions. This is a constrained and combinatorial type of a multi-objective optimization problem. In this paper, a fast and effective hybrid artificial intelligence algorithm is introduced and developed to reach a Pareto optimal set. The hybrid algorithm is composed of a fast and elitist multi-objective genetic algorithm (GA) and a fast fitness function evaluating system based on the cascade feed forward artificial neural networks (ANNs). A specific GA representation of core configuration and also special GA operators are introduced and used to overcome the combinatorial constraints of this optimization problem. A software package (Core Pattern Calculator 1) is developed to prepare and reform required data for ANNs training and also to revise the optimization results. Some practical test parameters and conditions are suggested to adjust main parameters of the hybrid algorithm. Results show that introduced ANNs can be trained and estimate selected core parameters of a research reactor very quickly. It improves effectively optimization process. Final optimization results show that a uniform and dense diversity of Pareto fronts are gained over a wide range of fitness function values. To take a more careful selection of Pareto optimal solutions, a revision system is introduced and used. The revision of gained Pareto optimal set is performed by using developed software package. Also some secondary operational and safety terms are suggested to help for final trade-off. Results show that the selected benchmark case study is dominated by gained Pareto fronts according to the main objectives while safety and operational constraints are preserved.