Relative potentials of concentrating and two-axis tracking flat-plate photovoltaic arrays for central-station applications

The purpose of this study is to assess the relative economic potentials of concenrating and two-axis tracking flat-plate photovoltaic arrays for central-station applications in the mid-1990's. Specific objectives of this study are to provide information on concentrator photovoltaic collector probabilistic price and efficiency levels to illustrate critical areas of R&D for concentrator cells and collectors, and to compare concentrator and flat-plate PV price and efficiency alternatives for several locations, based on their implied costs of energy. To deal with the uncertainties surrounding research and development activities in general, a probabilistic assessment of commercially achievable concentrator photovoltaic collector efficiencies and prices (at the factory loading dock) is performed. The results of this projection of concentrator photovoltaic technology are then compared with a previous flat-plate module price analysis (performed early in 1983). To focus this analysis on specific collector alternatives and their implied energy costs for different locations, similar two-axis tracking designs are assumed for both concentrator and flat-plate options

Characterization studies of Silicon Photomultipliers and crystals matrices for a novel time of flight PET detector

This paper describes the characterization of crystal matrices and silicon photomultiplier arrays for a novel Positron Emission Tomography (PET) detector, namely the external plate of the EndoTOFPET-US system. The EndoTOFPET-US collaboration aims to integrate Time-Of-Flight PET with ultrasound endoscopy in a novel multimodal device, capable to support the development of new biomarkers for prostate and pancreatic tumors. The detector consists in two parts: a PET head mounted on an ultrasound probe and an external PET plate. The challenging goal of 1 mm spatial resolution for the PET image requires a detector with small crystal size, and therefore high channel density: 4096 LYSO crystals individually readout by Silicon Photomultipliers (SiPM) make up the external plate. The quality and properties of these components must be assessed before the assembly. The dark count rate, gain, breakdown voltage and correlated noise of the SiPMs are measured, while the LYSO crystals are evaluated in terms of light yield and energy resolution. In order to effectively reduce the noise in the PET image, high time resolution for the gamma detection is mandatory. The Coincidence Time Resolution (CTR) of all the SiPMs assembled with crystals is measured, and results show a value close to the demanding goal of 200 ps FWHM. The light output is evaluated for every channel for a preliminary detector calibration, showing an average of about 1800 pixels fired on the SiPM for a 511 keV interaction. Finally, the average energy resolution at 511 keV is about 13 %, enough for effective Compton rejection.Comment: 12 pages, 31 figure

Planck-LFI radiometers' spectral response

The Low Frequency Instrument (LFI) is an array of pseudo-correlation radiometers on board the Planck satellite, the ESA mission dedicated to precision measurements of the Cosmic Microwave Background. The LFI covers three bands centred at 30, 44 and 70 GHz, with a goal bandwidth of 20% of the central frequency. The characterization of the broadband frequency response of each radiometer is necessary to understand and correct for systematic effects, particularly those related to foreground residuals and polarization measurements. In this paper we present the measured band shape of all the LFI channels and discuss the methods adopted for their estimation. The spectral characterization of each radiometer was obtained by combining the measured spectral response of individual units through a dedicated RF model of the LFI receiver scheme. As a consistency check, we also attempted end-to-end spectral measurements of the integrated radiometer chain in a cryogenic chamber. However, due to systematic effects in the measurement setup, only qualitative results were obtained from these tests. The measured LFI bandpasses exhibit a moderate level of ripple, compatible with the instrument scientific requirements.Comment: 16 pages, 9 figures, this paper is part of the Prelaunch status LFI papers published on JINST: http://www.iop.org/EJ/journal/-page=extra.proc5/jins

Development of an Analytic Nodal Diffusion Solver in Multigroups for 3D Reactor Cores with Rectangular or Hexagonal Assemblies.

More accurate modelling of physical phenomena involved in present and future nuclear reactors requires a multi-scale and multi-physics approach. This challenge can be accomplished by the coupling of best-estimate core-physics, thermal-hydraulics and multi-physics solvers. In order to make viable that coupling, the current trends in reactor simulations are along the development of a new generation of tools based on user-friendly, modular, easily linkable, faster and more accurate codes to be integrated in common platforms. These premises are in the origin of the NURESIM Integrated Project within the 6th European Framework Program, which is envisaged to provide the initial step towards a Common European Standard Software Platform for nuclear reactors simulations. In the frame of this project and to reach the above-mentioned goals, a 3-D multigroup nodal solver for neutron diffusion calculations called ANDES (Analytic Nodal Diffusion Equation Solver) has been developed and tested in-depth in this Thesis. ANDES solves the steady-state and time-dependent neutron diffusion equation in threedimensions and any number of energy groups, utilizing the Analytic Coarse-Mesh Finite-Difference (ACMFD) scheme to yield the nodal coupling equations. It can be applied to both Cartesian and triangular-Z geometries, so that simulations of LWR as well as VVER, HTR and fast reactors can be performed. The solver has been implemented in a fully encapsulated way, enabling it as a module to be readily integrated in other codes and platforms. In fact, it can be used either as a stand-alone nodal code or as a solver to accelerate the convergence of whole core pin-by-pin code systems. Verification of performance has shown that ANDES is a code with high order definition for whole core realistic nodal simulations. In this paper, the methodology developed and involved in ANDES is presented

Condition monitoring of an advanced gas-cooled nuclear reactor core

A critical component of an advanced gas-cooled reactor station is the graphite core. As a station ages, the graphite bricks that comprise the core can distort and may eventually crack. Since the core cannot be replaced, the core integrity ultimately determines the station life. Monitoring these distortions is usually restricted to the routine outages, which occur every few years, as this is the only time that the reactor core can be accessed by external sensing equipment. This paper presents a monitoring module based on model-based techniques using measurements obtained during the refuelling process. A fault detection and isolation filter based on unknown input observer techniques is developed. The role of this filter is to estimate the friction force produced by the interaction between the wall of the fuel channel and the fuel assembly supporting brushes. This allows an estimate to be made of the shape of the graphite bricks that comprise the core and, therefore, to monitor any distortion on them

Extending systems-on-chip to the third dimension : performance, cost and technological tradeoffs.

Because of the today's market demand for high-performance, high-density portable hand-held applications, electronic system design technology has shifted the focus from 2-D planar SoC single-chip solutions to different alternative options as tiled silicon and single-level embedded modules as well as 3-D integration. Among the various choices, finding an optimal solution for system implementation dealt usually with cost, performance and other technological trade-off analysis at the system conceptual level. It has been identified that the decisions made within the first 20% of the total design cycle time will ultimately result up to 80% of the final product cost. In this paper, we discuss appropriate and realistic metric for performance and cost trade-off analysis both at system conceptual level (up-front in the design phase) and at implementation phase for verification in the three-dimensional integration. In order to validate the methodology, two ubiquitous electronic systems are analyzed under various implementation schemes and discuss the pros and cons of each of them