A comparative study of integral parameters for TRX and BAPL benchmark lattices of thermal reactors using the cross-section library generated from JENDL and JEF evaluated data files

The objective of this paper is to present the results of comparative study of integral parameters for TRX and BAPL benchmark lattices of thermal reactors. The nuclear data processing code NJOY'99 was deployed for the generation of the 69-group cross-section library from the basic evaluated nuclear data files JENDL-3.2 and JEF-2.2. TRX and BAPL benchmark lattices were modeled with optimized inputs, which were suggested in the final report of the WIMS Library Update Project Stage-I. The inputs were the results of a detailed parametric study of the WIMS input options and also optimized for accuracy. The integral parameters (such as k_eff, ρ²⁸, δ²⁵, δ²⁸, C¹) of five uranium-fuel thermal assemblies: TRX-1 and TRX-2 and BAPL-1, BAPL-2, and BAPL-3 were calculated with the help of WIMSD-5B code based on the generated 69-group cross-section library. The calculated results are compared with those of experiments and it is found that the obtained results between the two libraries are in good agreement with each other. Besides, the calculated integral parameters are also well consistent with the measured values, which reflect the validation of the generated 69-group cross-section library and this library thus obtained is necessary to meet up the nuclear data for neutronics calculation of TRIGA Mark-II research reactor at AERE, Savar, Dhaka, Bangladesh.     

A Software Program for Real-Time Data Transmission From a Spex Datamate To a Vax Computer

ABSTRACT

A software program has been implemented to meet the requirements of an acknowledge enabled and Handshake protocol for reading, transmitting and saving of data from a SPEX Dàtamate controller to a VAX computer at real time scanning. The logic of the program can easily be applied to similar analytical instrumentation and computers. It stands forward as powerful method for data acquisition and processing and provides the basis for further calculations and plotting routines.     

Multi-objective optimization for optimum tolerance synthesis with process and machine selection using a genetic algorithm

This paper presents a new approach to the tolerance synthesis of the component parts of assemblies by simultaneously optimizing three manufacturing parameters: manufacturing cost, including tolerance cost and quality loss cost; machining time; and machine overhead/idle time cost. A methodology has been developed using the genetic algorithm technique to solve this multi-objective optimization problem. The effectiveness of the proposed methodology has been demonstrated by solving a wheel mounting assembly problem consisting of five components, two subassemblies, two critical dimensions, two functional tolerances, and eight operations. Significant cost saving can be achieved by employing this methodology.     

Studies on the overall safety aspects during irradiation of TeO2 in the central thimble of the TRIGA research reactor

The purpose of this study is to provide a detailed safety analysis of overall system and components in terms of their ability to provide optimum output from the irradiation of TeO₂ in the central thimble of the 3 MW TRIGA MARK II research reactor at Atomic Energy Research Establishment (AERE), Savar, Dhaka, Bangladesh. It identifies safety issues relevant to ¹³¹I radioisotope production and ensures that safety analysis and design are consistent. It evaluates threats developed within the facility during the irradiation process and ultimately ensures establishment of in-core safety limits and conditions at all stages of ¹³¹I production. In-core irradiation safety not only ensures the safe operation of the reactor but also strengthens the production of radioisotopes (RI). This study attempts to review and modify all safety related events and aspects relating to RI production. The three-dimensional continuous energy Monte Carlo code MCNP is used to develop a versatile and accurate full-core model of the TRIGA core. The cross-section library and fission product inventory are generated by using NJOY and ORIGEN computer codes. The methodology to evaluate heat generation and other relevant parameters necessary to provide enough information for thermal hydraulic analysis are discussed. The neutron flux distribution inside the dry and water filled central thimble is determined in order to locate the highest neutron flux trapping position. The thermal hydraulic and safety analysis are performed by elaborate numerical analysis as well as by using GENGTC computer code. A mock-up facility has also been developed to supplement and verify the theoretically predicted results. The total energy generated during irradiation of 50 gm TeO₂ sample in dry condition is found to be 113.84 w of which 75% energy is due to neutron heating and rest of the amount is from gamma heating. Around 11.28 w of heat energy is also generated in the quartz vial. When the total generated-heat transfer is considered through conduction and radiation mechanisms, the calculated temperature of 50 g of TeO₂ reaches at 970 °C. Considering simultaneous heat transfer mechanisms, (conduction, radiation and convection) the calculated maximum temperature of the 50 g of TeO₂ powder comes down at 680 °C. It may be pointed out that very high amount of heat is generated during the irradiation of TeO₂ at 3 MW reactor power in dry condition which is nearly the melting point of TeO₂ and may be termed as unsafe mode of irradiation.     

Dependence of pressure on elastic,electronic and optical properties of CeO2 and ThO2: A first principles study

The phase transformation of CeO₂ and ThO₂ from fluorite to cotunnite-type structure under pressure is predicted within the density functional theory implemented with the GGA-PW91 method, the pressure induced structural phase transition occurs at 28.9 GPa for CeO₂ and 29.8 GPa for ThO₂. These values are in excellent agreement with the experimentally measured data. The elastic, electronic and optical properties at normal as well as for high-pressure phase have been calculated, particular attention is devoted to the cotunnite phase. Further, the dependence of the elastic constants, the bulk modulus B, the energy band gaps and the dielectric function on the applied pressure are presented.     

A comparative study on life cycle assessment of micro and macro components

Micro manufacturing is an extremely demanding technological field where very special materials are used, extreme production condition like clean room, super high temperature, toxic chemicals, etc. are employed. Due to these facts, micro products can be environmentally damaging even after their smaller dimensional scale. So performing of LCA for micro products is equally important as it is for macro products. Keeping this motivation in mind, current paper systematically performs the LCA of a micro Socket used in hearing aids. The analysis makes a guide line about how to use the conventional knowledge about LCA and tools for the efficient LCA analysis of the micro parts. A comparative study is made in the paper by comparing two different sockets of hearing aid and it shows well how to make a comparative study for LCA when the manufacturer makes a new product to replace an old one. Another comparative study is made in the paper for micro and macro which shows that scaled up effect of the micro product compared to macro counterpart. The critical finding of this comparative study shows that the relative environmental damage done by micro product is higher than the macro product and that is confirmed by the net impact analysis. Finally, the LCA procedure presented in the paper, and the knowledge documented can be a valuable source of information for the researchers and scientists who work with the LCA of micro and macro products.     

Scaling Up of Chemical Injection Experiments

Abstract

It is well known that laboratory experiments are the most useful means of developing predictive models for various engineering applications. However, scaling laws should be known in order to scale up laboratory results to field conditions. This scaling up offers a formidable challenge in scenarios involving complex solid/fluid interactions which are predominant in chemical processes such as in petroleum engineering and environmental remediation. This article presents a series of chemical adsorption tests and provides one with the scaled-up versions; these results are then compared with numerical simulation results. Finally, recommendations are made as to how to interpret laboratory experimental results and apply scaling laws to predict field behavior.     

Solvothermal synthesis of greigite (Fe3S4)– Conducting polypyrrole nanocomposite and its application towards arsenic removal

In the present investigation, Greigite-conducting polypyrrole nanocomposite (GPPy nanocomposite) was prepared, characterized and used to remove arsenite and arsenate from aqueous solution. Fe₃S₄ was synthesized using solvothermal synthetic method and it was grafted to conducting polypyrrole matrix. The nanocomposite was characterized using FE-SEM, EDX, XRD, FTIR, TGA/DSC and BET surface area. Kinetic studies revealed that the removal process followed first order kinetics. Batch isotherm studies were performed to determine the binding capacity. Thermodynamic parameters were also computed and it indicated the spontaneous nature of the process. Electrophoretic studies were carried out to determine the point of zero charge.     

Design and performance analysis of a nanoscaled inverter based on wrap-aroundgate nanowire MOSFETs

The design and analysis of a silicon nanowire inverter with a wrap-around-gate nMOS is presented and its performance is compared with that of a conventional inverter. The analysis shows that the nano-channel structure design can improve carrier mobility by suppressing the transverse component of the electric field. This results in an enhancement in the current drive of the nMOS, and contributes to lowering power consumption and the switching delay. Simulated power consumption and rise time of the proposed design was found to be about 20 μW and 0.5 ns, respectively, compared with 2.5 mW and 1.5 ns achievable with conventional planar MOSFETs. Investigation of the gate length shows that a nMOS with shorter gates have an improved switching response compared with long channel devices.