Advances in the Application and Understanding of the CHALMEX FS-13 Process

During the last year, the European demand for electricity has increased and at the same time, the production of planned electricity generation has decreased due to unexpected weather conditions and war. Combined with a limited capability to store energy, low-carbon energy producers such as nuclear power is getting renewed attention in many countries. While having benefits such as reliable, clean, affordable and safe electricity production, the main concerns regarding nuclear power usually refer to the extremely long-lived and radiotoxic final waste. The main contributor to the long-lived radiotoxicity of the spent fuel is Pu and the minor actinides (Np, Am, Cm). The Chalmers Grouped ActiNide EXtraction (CHALMEX) process is a solvent extraction process for the recycling of minor and major actinides as a group, from spent nuclear fuel. By recycling the actinides, and using them as fuel in fast reactors, one can significantly reduce both the overall environmental impact of the nuclear fuel cycle, the lifetime- and the radiotoxicity of the final waste. By combining the extractants TBP with CyMe4-BTBP in the diluent FS-13, the CHALMEX solvent has been shown to have preferential physical properties for use in industrial processes. Separation of the actinides from a spent fuel solution is achieved in only 8 process stages. The co-separation of specific fission products is reduced by the use of masking agents and scrubbing stages. Overall, low degrees of fission product contamination is found in the actinide product stream (<1.5%).The kinetics of the system has also been shown to be compatible with contacting in centrifugal contactors. Despite observation of phase entrainment under certain conditions in a centrifugal contactor, the CHALMEX process is a promising process for the actinide separation from spent nuclear fuels

Path-Based partitioning methods for 3D Networks-on-Chip with minimal adaptive routing

© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Combining the benefits of 3D ICs and Networks-on-Chip (NoCs) schemes provides a significant performance gain in Chip Multiprocessors (CMPs) architectures. As multicast communication is commonly used in cache coherence protocols for CMPs and in various parallel applications, the performance of these systems can be significantly improved if multicast operations are supported at the hardware level. In this paper, we present several partitioning methods for the path-based multicast approach in 3D mesh-based NoCs, each with different levels of efficiency. In addition, we develop novel analytical models for unicast and multicast traffic to explore the efficiency of each approach. In order to distribute the unicast and multicast traffic more efficiently over the network, we propose the Minimal and Adaptive Routing (MAR) algorithm for the presented partitioning methods. The analytical and experimental results show that an advantageous method named Recursive Partitioning (RP) outperforms the other approaches. RP recursively partitions the network until all partitions contain a comparable number of switches and thus the multicast traffic is equally distributed among several subsets and the network latency is considerably decreased. The simulation results reveal that the RP method can achieve performance improvement across all workloads while performance can be further improved by utilizing the MAR algorithm. Nineteen percent average and 42 percent maximum latency reduction are obtained on SPLASH-2 and PARSEC benchmarks running on a 64-core CMP.Ebrahimi, M.; Daneshtalab, M.; Liljeberg, P.; Plosila, J.; Flich Cardo, J.; Tenhunen, H. (2014). Path-Based partitioning methods for 3D Networks-on-Chip with minimal adaptive routing. IEEE Transactions on Computers. 63(3):718-733. doi:10.1109/TC.2012.255S71873363

Studies of intensified liquid-liquid extractions in small-channel contactors and their scale-up

This thesis presents a series of investigations focused on scaling-up intensified liquid-liquid flow processes from single-channel to commercial-scale. The process investigated consists of liquid-liquid extractions of U(VI) from nitric acid to an organic phase. These extractions are relevant to the safety and sustainability of the nuclear fuel cycle. The intensified contactor consists of a tee-junction feeding to a channel with small internal diameter (1 to 4 mm) operating under segmented flow pattern. Segmented flow contactors intensify liquid-liquid extractions in uranium recovery processes because they provide intense mixing, short diffusion distances, and large interfacial area at low energy input. Using high-speed imaging, UV-Vis spectroscopy, pressure gradient measurements, and dimensional analysis, the operation and design trade-offs are quantitatively identified with focus on scale-up. A finite-element model is used to corroborate the experimental mass transfer results. The scale-up is achieved via numbering-up, which increases the number of process units instead of making one larger unit. Economic parallelisation requires effective flow distribution. Multiphase flow distribution has been a persistent problem in the path towards commercialisation. This problem is addressed by modelling a double manifold with a resistance network model and a novel method to quantify maldistribution, derived from multivariate statistical analysis. The relationships between the hydraulic resistances with maldistribution, pumping power, and the number of channels are quantified. Finally, the single-channel results and the flow distributor model are used to design, build, and test a modular multichannel segmented flow contactor prototype. The design and commissioning steps are described along with the experimental maldistribution results, including flow distribution and mass transfer results. The multichannel contactor can be operated with different number of channels at any time, thus changing a long-standing paradigm in reactor design. This promises to accelerate process development by facilitating the transition from bench to pilot and commercial scales

Development of Hybrid Fuel Cell / Li-ion Battery Systems

Electrochemical power systems are needed to de-carbonise the transport industry. Fuel cells and battery systems alone may not be able to meet the diverse set of requirements, but when hybridised, their applicability to this sector is vastly increased. This raises questions around the specific nature of hybridisation. This thesis aims to expand our understanding of fuel cell and lithium-ion battery hybridisation for automotive applications, through a combined experimental and computational approach. Prior to undertaking such research, an understanding of each individual system is required. This is perused along the themes of current heterogeneity, and applied to parallel battery cells in two common electrical configurations and across the active area of a 100 cm2 polymer exchange fuel cell. First, it is shown the electrical configuration of the parallel string has significant impact on the current distribution, impacting the charge throughput of each cell and the usable capacity of the module. Degradation modelling showed the lifetime of the module is reduced by 4.5% in the less optimal configuration. Secondly, the current and thermal distribution within a fuel cell is investigated for a range of operating conditions such as flooding, drying and cold start. Electrochemical impedance spectroscopy is used to understand the conditions of the membrane and reactant time constants in-situ. Results indicate how the design of fuel cells can be refined to improve performance in challenging operating conditions. Finally, the investigation of electrical and thermal hybridisation is conducted on a passenger sized vehicle. A common modelling framework is developed, using the models developed in the fuel cell and battery chapters, to assess electrical energy management systems. A novel fuzzy logic controller is developed which mutates the output membership functions based on the ‘state-of-degradation’, a parameter derived from an interconnected electrochemical surface area loss and system state model. The controller is able to extend the lifetime of the fuel cell by 32.8% in its presented configuration. The common framework is then developed to include dynamic thermal models of the fuel cell, battery pack, radiator and auxiliaries to investigate whether combining the battery pack and fuel cell stack onto a single coolant loop is feasible. The system is tested against a range of operating conditions and its performance is discussed. These findings are expected to aid the transport industry in the transition to a zero emission future

Algorithm and Hardware Design for High Volume Rate 3-D Medical Ultrasound Imaging

abstract: Ultrasound B-mode imaging is an increasingly significant medical imaging modality for clinical applications. Compared to other imaging modalities like computed tomography (CT) or magnetic resonance imaging (MRI), ultrasound imaging has the advantage of being safe, inexpensive, and portable. While two dimensional (2-D) ultrasound imaging is very popular, three dimensional (3-D) ultrasound imaging provides distinct advantages over its 2-D counterpart by providing volumetric imaging, which leads to more accurate analysis of tumor and cysts. However, the amount of received data at the front-end of 3-D system is extremely large, making it impractical for power-constrained portable systems. In this thesis, algorithm and hardware design techniques to support a hand-held 3-D ultrasound imaging system are proposed. Synthetic aperture sequential beamforming (SASB) is chosen since its computations can be split into two stages, where the output generated of Stage 1 is significantly smaller in size compared to the input. This characteristic enables Stage 1 to be done in the front end while Stage 2 can be sent out to be processed elsewhere. The contributions of this thesis are as follows. First, 2-D SASB is extended to 3-D. Techniques to increase the volume rate of 3-D SASB through a new multi-line firing scheme and use of linear chirp as the excitation waveform, are presented. A new sparse array design that not only reduces the number of active transducers but also avoids the imaging degradation caused by grating lobes, is proposed. A combination of these techniques increases the volume rate of 3-D SASB by 4\texttimes{} without introducing extra computations at the front end. Next, algorithmic techniques to further reduce the Stage 1 computations in the front end are presented. These include reducing the number of distinct apodization coefficients and operating with narrow-bit-width fixed-point data. A 3-D die stacked architecture is designed for the front end. This highly parallel architecture enables the signals received by 961 active transducers to be digitalized, routed by a network-on-chip, and processed in parallel. The processed data are accumulated through a bus-based structure. This architecture is synthesized using TSMC 28 nm technology node and the estimated power consumption of the front end is less than 2 W. Finally, the Stage 2 computations are mapped onto a reconfigurable multi-core architecture, TRANSFORMER, which supports different types of on-chip memory banks and run-time reconfigurable connections between general processing elements and memory banks. The matched filtering step and the beamforming step in Stage 2 are mapped onto TRANSFORMER with different memory configurations. Gem5 simulations show that the private cache mode generates shorter execution time and higher computation efficiency compared to other cache modes. The overall execution time for Stage 2 is 14.73 ms. The average power consumption and the average Giga-operations-per-second/Watt in 14 nm technology node are 0.14 W and 103.84, respectively.Dissertation/ThesisDoctoral Dissertation Engineering 201

Doctor of Philosophy

dissertationThis dissertation presents original research that improves the ability of magnetic resonance imaging (MRI) to measure temperature in aqueous tissue using the proton resonance frequency (PRF) shift and T1 measurements in fat tissue in order to monitor focused ultrasound (FUS) treatments. The inherent errors involved in measuring the longitudinal relaxation time T1 using the variable flip angle method with a two-dimensional (2D) acquisition are presented. The edges of the slice profile can contribute a significant amount of signal for large flip angles at steady state, which causes significant errors in the T1 estimate. Only a narrow range of flip angle combinations provided accurate T1 estimates. Respiration motion causes phase artifacts, which lead to errors when measuring temperature changes using the PRF method. A respiration correction method for 3D imaging temperature of the breast is presented. Free induction decay (FID) navigators were used to measure and correct phase offsets induced by respiration. The precision of PRF temperature measurements within the breast was improved by an average factor of 2.1 with final temperature precision of approximately 1 °C. Locating the position of the ultrasound focus in MR coordinates of an ultrasound transducer with multiple degrees of freedom can be difficult. A rapid method for predicting the position using 3 tracker coils with a special MRI pulse iv sequence is presented. The Euclidean transformation of the coil's current positions to their calibration positions was used to predict the current focus position. The focus position was predicted to within approximately 2.1 mm in less than 1 s. MRI typically has tradeoffs between imaging field of view and spatial and temporal resolution. A method for acquiring a large field of view with high spatial and temporal resolution is presented. This method used a multiecho pseudo-golden angle stack of stars imaging sequence to acquire the large field of view with high spatial resolution and k-space weighted image contrast (KWIC) to increase the temporal resolution. The pseudo-golden angle allowed for removal of artifacts introduced by the KWIC reconstruction algorithm. The multiple echoes allowed for high readout bandwidth to reduce blurring due to off resonance and chemical shift as well as provide separate water/fat images, estimates of the initial signal magnitude M(0), T2 * time constant, and combination of echo phases. The combined echo phases provided significant improvement to the PRF temperature precision, and ranged from ~0.3-1.0 °C within human breast. M(0) and T2 * values can possibly be used as a measure of temperature in fat

Fundamental Understanding of Poly(ether ketone ketone) for High Temperature Laser Sintering

High-Temperature Laser Sintering (HT-LS) is a powder bed fusion technique employed to manufacture polymers with high service temperature, usually above 150 oC. The aerospace, automotive, and medical industries have driven the demand for processing high-performance polymers, as they could offer a lighter and cheaper alternative while maintaining the mechanical and chemical performance required to replace metallic parts in particular environments. Kepstan 6002 poly(ether ketone ketone) (PEKK) belongs to poly(aryl ether ketone)s (PAEKs) family and has a promising application in LS. The lower melting temperature united to the high glass transition temperature of PEKK (similar to PEK HP3, first commercially available HT-LS grade) enabled processing at lower temperatures whilst maintaining the high-temperature resistance of the polymer. Furthermore, the kinetics of crystallisation of Kepstan 6002 PEKK is very slow, which can assist layer adhesion during LS and improve mechanical properties in Z orientation. The present research project was developed in collaboration with Arkema. Three different grades of Kepstan 6002 PEKK were selected for initial analyses – HL1327, HL1320, and P12S959a. The powders were characterised for powder size, distribution, morphology, flow, moisture effect, and coalescence behaviour. This screening enabled the selection of HL1327 grade as the most promising for HT-LS application. The PEKK particle and powder analyses continued with an in-depth study of particle size and shape changes as a function of temperature and coalescence. The study revealed individual particle shrinkage prior to melting, followed by increased growth. The same phenomenon was observed for pairs of particles during coalescence and was attributed to the recovering of elastic deformation of the polymeric chains. The effect of intrinsic PEKK characteristics was successfully evaluated and quantified in the overall shrinkage in LS. The results identified powder properties as the main factor causing shrinkage of PEKK, as opposed to crystallisation. These results are supported by the powder characterisation developed in previous chapters. The interaction between material and process was investigated and optimised by testing different combinations of laser parameters and processing temperatures. The resulting properties were monitored regarding mechanical performance, surface topography, porosity, and crystallisation. The optimised PEKK specimens showed excellent mechanical strength (∼90 MPa) and modulus, but poor elongation, a common drawback from the LS process. The combination of fundamental material properties and process optimisation led to the development of a novel route to improve elongation and control the mechanical performance of LS PEKK. The experimental method successfully related cooling time, mechanical properties, and crystallisation of PEKK, and was able to increase elongation at break by 5.4 times. The improvement of elongation at break was attributed to the largely amorphous phase of PEKK when subjected to short cooling times. Lastly, powder recyclability was investigated from a chemical and physical perspective. PEKK can be reused following additional treatment steps, e.g., sieving. The potential for recyclability is an important remark as the material cost is significantly reduced and therefore preferred over the use of metals for high-performance applications