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‣ The conditional/generalized maximum likelihood logit computer program : instructions for use, energy management and economics

Massachusetts Institute of Technology Energy Laboratory in association with the Sloan School of Management and the Dept. of Urban Studies and Planning.
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 1072505 bytes; application/pdf
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Prepared for the U.S. Dept. of Energy under Contract no. EX-76-A-01-2295, Task order 37.

‣ LWR core thermal-hydraulic analysis : assessment and comparison of the range of applicability of the codes COBRA IIIC/MIT and COBRA IV-I

Kelly, J. E.; Loomis, James N.; Wolf, Lothar
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 7751688 bytes; application/pdf
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This report summarizes the result of studies concerning the range of applicability of two subchannel codes for a variety of thermal-hydraulic analyses. The subchannel codes used include COBRA IIIC/MIT and the newly developed code, COBRA IV-I which is considered the benchmark code for the purpose of this report. Hence, through the comparisons of the two codes, the applicability of COBRA IIIC/MIT is assessed with respect to COBRA IV-I. A variety of LWR thermal-hydraulic analyses are examined. Results of both codes for steady-state and transient analyses are compared. The types of analysis include BWR bundle-wide analysis, a simulated rod ejection and loss of flow transients for a PWR. The system parameters were changed drastically to reach extreme coolant conditions, thereby establishing upper limits. In addition to these cases, both codes are compared to experimental data including measured coolant exit temperatures in a core, interbundle mixing for inlet flow upset cases and two-subchannel flow blockage measurements. The comparisons showed that, overall, COBRA IIIC/MIT predicts most thermal-hydraulic parameters quite satisfactorily. However, the clad temperature predictions differ from those calculated by COBRA IV-I and appear to be in error. These incorrect predictions are caused by the discontinuity in the heat transfer coefficient at the start of boiling. Hence...

‣ A condensed review of nuclear reactor thermal-hydraulic computer codes for two-phase flow analysis

Kazimi, Mujid S.; Massoud, Mahmoud
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 5295128 bytes; application/pdf
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A review is made of the computer codes developed in the U.S. for thermal-hydraulic analysis of nuclear reactors. The intention of this review is to compare these codes on the basis of their numerical method and physical models with particular attention to the two-phase flow and heat transfer characteristics. A chronology of the most documented codes such as COBRA and RELAP is given. The features of the recent codes as RETRAN, TRAC and THERMIT are also reviewed. The range of application as well as limitations of the various codes are discussed.; Sponsored by Boston Edison Company and others under MIT Energy Laboratory Electric Utility Program.

‣ SYSGEN : production costing and reliability model user documentation

Finger, Susan
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 6040020 bytes; application/pdf
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"Updated February 1980".; Sponsored by the Dept. of Energy under Contract no. EX-76-A-01-2295.

‣ Development and testing of three dimensional, two-fluid code THERMIT for LWR core and subchannel applications

Kelly, John Edward; Kazimi, Mujid S.
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 5117191 bytes; application/pdf
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At head of title: Energy Laboratory and Dept. of Nuclear Engineering.; Sponsored by Boston Edison Company and others under MIT Energy Laboratory Electric Utility Program.

‣ Development of models for the sodium version of the two-phase three dimensional thermal hydraulics code THERMIT

Wilson, Gregory James; Kazimi, Mujid S.
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 6959220 bytes; application/pdf
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Several different models and correlations were developed and incorporated in the sodium version of THERMIT, a thermal- hydraulics code written at MIT for the purpose of analyzing transients under LMFBR conditions. This includes: a mechanism for the inclusion of radial heat conduction in the sodium coolant as well as radial heat loss to the structure surrounding the test section. The fuel rod conduction scheme was modified to allow for more flexibility in modelling the gas plenum regions and fuel restructuring. The formulas for mass and momentum exchange between the liquid and vapor phases were improved. The single phase and two phase friction factors were replaced by correlations more appropriate to LMFBR assembly geometry. The models incorporated in THERMIT were tested by running the code to simulate the results of the THORS Bundle 6A experiments performed at Oak Ridge National Laboratory. The results demonstrate the increased accuracy provided by the inclusion of these effects.; "Sponsored by U.S Department of Energy, General Electric Co. and Hanford Engineering Development Laboratory."

‣ A two dimensional, two fluid model for sodium boiling in LMFBR fuel assemblies

Granziera, Mario Roberto; Kazimi, Mujid S.
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 11731420 bytes; application/pdf
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A two dimensional numerical model for the simulation of sodium boiling transient was developed using the two fluid set of conservation equations. A semiimplicit numerical differencing scheme capable of handling the problems associated with the ill-posedness implied by the complex characteristic roots of the two fluid problems was used, which took advantage of the dumping effect of the exchange terms. Of particular interest in the development of the model was the identi- fication of the numerical problems caused by the strong disparity between the axial and radial dimensions of fuel assemblies. A solution to this problem was found which uses the particular geometry of fuel assemblies to accelerate the convergence of the iterative technique used in the model. The most important feature of the model was its ability to simulate severe conditions of sodium boiling, in particular flow reversal, which was shown in the tests performed with the model. Three sodium boiling experiments were simulated with the model, with good agreement between the experimental results and the model predictions.; "Sponsored by U.S Department of Energy, General Electric Co. and Hanford Engineering Development Laboratory."

‣ Primer on Demand-Side Management : With an Emphasis on Price-Responsive Programs

World Bank
Fonte: Washington, DC Publicador: Washington, DC
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The practice of Demand-Side Management (DSM) has evolved over the past three decades in response to lessons learned from implementation in different global settings, and also in response to the changing needs of restructured power markets. The most notable change that is occurring today is the inclusion of programs that emphasize price responsiveness in the DSM portfolio. Traditionally, DSM programs were confined to energy efficiency and conservation programs with reliability-driven load management programs being used occasionally to manage emergency situations. Electric prices were taken as a given when designing such programs, hampering the eventual success of all such efforts. This Primer has been written to introduce the new concepts of price-responsive DSM that are currently being investigated in a variety of different market settings. It highlights different criteria and taxonomies for classification and evaluation of DSM programs and recommends programs that will likely provide a better fit with the objectives, expected needs and outcomes of DSM initiatives in developing and transition countries. As defined in this primer, such initiatives include both load shifting programs (that either clip peak loads or shift energy used in the peak period to off-peak periods) and efficiency programs (that reduce the total amount of energy). The purpose of the primer is to provide successful examples of price-responsive DSM programs from the developed world and by discussing their workings...

‣ The fuel cycle economics of improved uranium utilization in light water reactors

Abbaspour, Ali Tehrani; Driscoll, Michael J.
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 9420038 bytes; application/pdf
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A simple fuel cycle cost model has been formulated, tested satisfactorily (within better than 3% for a wide range of cases) using a more elaborate computer program, and applied to evaluate a variety of PWR fuel cyclesand fuel management options, with an emphasis on issues pertinent to the NASAP/INFCE efforts. The uranium and thorium cycles were examined, lattice fuel-to-moderator and burnup were varied, and once-through and recycle modes were examined. It was found that increasing core burnup was economically advantageous, particularly if busbar or total system cost is considered in lieu of fuel cycle cost only, for both once-through and recycle modes, so long as the number of staggered core batches is increased concurrently. When optimized under comparable ground rules, the once-through fuel cycle is competitive with the recycle option; differences are well within the rather large (+ 20%) one sigma uncertainty estimated for the overall fuel cycle costs by propagating uncertainties in input data. Optimization on mills/kwhre and ore usage, tones/GWe,yr, are generally, but not universally, compatible criteria. To the extent evaluated, the thorium fuel cycle was not found to be economically competitive. Cost-optimum thorium lattices were found to be drier than for current PWRs...

‣ Development of a method for BWR subchannel analysis

Faya, Artur José Goncalves; Wolf, Lothar; Todreas, Neil E.
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 6493270 bytes; application/pdf
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This study deals with the development of a computer pro- gram for steady-state and transient BWR subchannel analysis. The conservation equations for the subchannels are obtained by area-averaging of the two-fluid model conservation equa- tions and reducing them to the drift-flux model formulation. The conservation equations are solved by a marching type technique which limits the code to analysis of operational transients only. The transfer of mass, momentum and energy between adjacent subchannels is split into diversion cross- flow and turbulent mixing components. The transfer of mass by turbulent mixing is assumed to occur in a volume-for- volume scheme reflecting experimental observations. The phenomenon of lateral vapor drift and mixing enhancement with flow regime are included in the mixing model of the program. The following experiments are used for the purpose of the assessment of the code under steady-state conditions: 1) GE Nine-Rod tests with radially uniform and nonuniform heating 2) Studsvik Nine-rod tests with strong radial power tilt 3) Ispra Sixteen-rod tests with radially uniform heating Comparison of calculated results with these data shows that the program is capable of predicting the correct trends in exit mass velocity and quality distributions.; Originally presented as the author's thesis...

‣ CANAL user's manual

Faya, Artur José Goncalves; Wolf, Lothar; Todreas, Neil E.
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 4194381 bytes; application/pdf
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This report gives a detailed description of the input data and contains a listing of the computer program CANAL. A sample problem is also provided.

‣ Qualitative and quantitative reliability analysis of safety systems

Karimi, Roohollah
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 11009616 bytes; application/pdf
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A code has been developed for the comprehensive analysis of a fault tree.' The code designated UNRAC (UNReliability Analysis Code) calculates the following characteristics of an Tnput fauTt tree: a) minimal cut sets, b) top event unavailability as point estimate and/or in time dependent form, c) quantitative importance of each component involved, and d) error bound on the top event unavailability UNRAC can analyze fault trees, with any kind of gates (EOR, NAND, NOR, AND, OR), up to a maximum of 250 components and/or gates. For generating minimal cut sets the method of bit manipu- lation is employed. In order to calculate each component's time dependent unavailability, a general and consistent set of mathematical models is developed and the repair time density function is allowed to be represented by constant, exponen- tial, 2nd order erlangian and log-normal distributions. A normally operating component is represented by a three-state model in order to be able to incorporate probabilities for revealed faults, non-revealed faults and false failures in unavailability calculations. For importance analysis, a routine is developed that will rearrange the fault tree to evaluate the importance of each component to system failure...

‣ WOSUB : a subchannel code for steady-state and transient thermal-hydraulic analysis of BWR fuel pin bundles.

Wolf, Lothar; Guillebaud, Louis Jean Marie; Faya, A.
Fonte: Massachusetts Institute of Technology. Energy Laboratory Publicador: Massachusetts Institute of Technology. Energy Laboratory
Tipo: Relatório Formato: 7735220 bytes; application/pdf
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The WOSUB-codes are spin-offs and extensions of the MATTEO-code [1]. The series of three reports describe WOSUB-I and WOSUB-II in their respective status as of July 31, 1977. This report is the first in a series of three, the second of which contains the user's manual [2] and the third [3] summarizes the assessment and comparison with experimental data and various other subchannel codes. The present report introduces the drift-flux and vapor diffusion models employed by the code, discusses the solution method and reviews the constitutive equations presently built into the code. Wherever applicable, possible exteriors of the models are indicated especially with due regard of the findings presented in [3]. Overall, the review of the model and the package of constitutive equations demonstrate that WOSUB-I and II constitute true alternatives for BWR bundle and PWR test bundle calculations as compared to the commonly applied COBRA-IIIC, and COBRA-IIIC/MIT codes which were primarily designed for PWR subchannel and core calculations, respectively. In fact, the incorporation of the drift flux and the vapor diffusion pro- cesses into a subchannel code has to be cdnsidered.a major step towards a more basic understanding and a well balanced engineer- ing approach without the extra burden of a true two-fluid two- phase model. Recommendations for improvements in the various areas are indicated and should serve as guidelines for future develop- ment of this code which in light of the encouraging results pre- sented in [3] seems to be highly warranted. The WOSUB-code is still in the stage of evolutionary development. In this context...

‣ WOSUB : a subchannel code for steady-state and transient thermal-hydraulic analysis of BWR fuel pin bundles. Volume II. User's Manual

Guillebaud, Louis Jean Marie.; Levine, A.; Boyd, W.; Faya, A.; Wolf, Lothar
Fonte: MIT Energy Laboratory Publicador: MIT Energy Laboratory
Tipo: Relatório Formato: 10033375 bytes; application/pdf
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The WOSUB-codes are spin-offs and extensions of the MATTEO- code [ 2 ]. The series of reports describe WOSUB-I and WOSUB-II in their respective status as of July 31, 1977. This report is the second of a series of three reports describing the WOSUB code. It gives a detailed description of the input data, flow charts, and output, and contains the list- ings of WOSUB-I and WOSUB-II. For the purpose of future ex- tensions parameters, common blocks and variables used in the code are listed in full detail. WOSUB-I and WOSUB-II are subchannel computer codes for the steady-state and transient analysis of the thermal-hydraulic characteristics of Boiling Water Reactor (BWR) fuel rod bundles. Both codes are also applicable'to analyze PR bundles, especially when these are ducted--a situation which most often arises in experimental set-ups. The main difference between WOSUB-I and WOSUB-II is that the former is designed to analyze small bundles, whereas the latter is capable to handle symmetric sections of today's large- sized BWR bundles. In addition, WOSUB-II does not contain all of the additions made in WOSUB-I yet, because it is deemed appropriate to introduce these into the smaller code first, before they are implemented into the bigger one. Both codes are still in the stage of evolutionary develop- ment. Thus...

‣ Electricity Demand and Energy Consumption Management System

Sarmiento, Juan Ojeda
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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This project describes the electricity demand and energy consumption management system and its application to Southern Peru smelter. It is composed of an hourly demand-forecasting module and of a simulation component for a plant electrical system. The first module was done using dynamic neural networks with backpropagation training algorithm; it is used to predict the electric power demanded every hour, with an error percentage below of 1%. This information allows efficient management of energy peak demands before this happen, distributing the raise of electric load to other hours or improving those equipments that increase the demand. The simulation module is based in advanced estimation techniques, such as: parametric estimation, neural network modeling, statistic regression and previously developed models, which simulates the electric behavior of the smelter plant. These modules facilitate electricity demand and consumption proper planning, because they allow knowing the behavior of the hourly demand and the consumption patterns of the plant, including the bill components, but also energy deficiencies and opportunities for improvement, based on analysis of information about equipments, processes and production plans, as well as maintenance programs. Finally the results of its application in Southern Peru smelter are presented.

‣ On the Value and Limits of Multi-level Energy Consumption Static Analysis for Deeply Embedded Single and Multi-threaded Programs

Georgiou, Kyriakos; Kerrison, Steve; Eder, Kerstin
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/10/2015 Português
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There is growing interest in lowering the energy consumption of computation. Energy transparency is a concept that makes a program's energy consumption visible from software to hardware through the different system layers. Such transparency can enable energy optimizations at each layer and between layers, and help both programmers and operating systems make energy aware decisions. The common methodology of extracting the energy consumption of a program is through direct measurement of the target hardware. This usually involves specialized equipment and knowledge most programmers do not have. In this paper, we examine how existing methods for static resource analysis and energy modeling can be utilized to perform Energy Consumption Static Analysis (ECSA) for deeply embedded programs. To investigate this, we have developed ECSA techniques that work at the instruction set level and at a higher level, the LLVM IR, through a novel mapping technique. We apply our ECSA to a comprehensive set of mainly industrial benchmarks, including single-threaded and also multi-threaded embedded programs from two commonly used concurrency patterns, task farms and pipelines. We compare our ECSA results to hardware measurements and predictions obtained based on simulation traces. We discuss a number of application scenarios for which ECSA results can provide energy transparency and conclude with a set of new research questions for future work.; Comment: 29 pages...

‣ Modeling and visualizing networked multi-core embedded software energy consumption

Kerrison, Steve; Eder, Kerstin
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/09/2015 Português
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In this report we present a network-level multi-core energy model and a software development process workflow that allows software developers to estimate the energy consumption of multi-core embedded programs. This work focuses on a high performance, cache-less and timing predictable embedded processor architecture, XS1. Prior modelling work is improved to increase accuracy, then extended to be parametric with respect to voltage and frequency scaling (VFS) and then integrated into a larger scale model of a network of interconnected cores. The modelling is supported by enhancements to an open source instruction set simulator to provide the first network timing aware simulations of the target architecture. Simulation based modelling techniques are combined with methods of results presentation to demonstrate how such work can be integrated into a software developer's workflow, enabling the developer to make informed, energy aware coding decisions. A set of single-, multi-threaded and multi-core benchmarks are used to exercise and evaluate the models and provide use case examples for how results can be presented and interpreted. The models all yield accuracy within an average +/-5 % error margin.

‣ Static analysis of energy consumption for LLVM IR programs

Grech, Neville; Georgiou, Kyriakos; Pallister, James; Kerrison, Steve; Morse, Jeremy; Eder, Kerstin
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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Energy models can be constructed by characterizing the energy consumed by executing each instruction in a processor's instruction set. This can be used to determine how much energy is required to execute a sequence of assembly instructions, without the need to instrument or measure hardware. However, statically analyzing low-level program structures is hard, and the gap between the high-level program structure and the low-level energy models needs to be bridged. We have developed techniques for performing a static analysis on the intermediate compiler representations of a program. Specifically, we target LLVM IR, a representation used by modern compilers, including Clang. Using these techniques we can automatically infer an estimate of the energy consumed when running a function under different platforms, using different compilers. One of the challenges in doing so is that of determining an energy cost of executing LLVM IR program segments, for which we have developed two different approaches. When this information is used in conjunction with our analysis, we are able to infer energy formulae that characterize the energy consumption for a particular program. This approach can be applied to any languages targeting the LLVM toolchain...

‣ Inferring Parametric Energy Consumption Functions at Different Software Levels: ISA vs. LLVM IR

Liqat, Umer; Georgiou, Kyriakos; Kerrison, Steve; Lopez-Garcia, Pedro; Gallagher, John P.; Hermenegildo, Manuel V.; Eder, Kerstin
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/11/2015 Português
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The static estimation of the energy consumed by program executions is an important challenge, which has applications in program optimization and verification, and is instrumental in energy-aware software development. Our objective is to estimate such energy consumption in the form of functions on the input data sizes of programs. We have developed a tool for experimentation with static analysis which infers such energy functions at two levels, the instruction set architecture (ISA) and the intermediate code (LLVM IR) levels, and reflects it upwards to the higher source code level. This required the development of a translation from LLVM IR to an intermediate representation and its integration with existing components, a translation from ISA to the same representation, a resource analyzer, an ISA-level energy model, and a mapping from this model to LLVM IR. The approach has been applied to programs written in the XC language running on XCore architectures, but is general enough to be applied to other languages. Experimental results show that our LLVM IR level analysis is reasonably accurate (less than 6.4% average error vs. hardware measurements) and more powerful than analysis at the ISA level. This paper provides insights into the trade-off of precision versus analyzability at these levels.; Comment: 22 pages...

‣ Minimizing Energy Consumption of MPI Programs in Realistic Environment

Guermouche, Amina; Triquenaux, Nicolas; Pradelle, Benoit; Jalby, William
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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Dynamic voltage and frequency scaling proves to be an efficient way of reducing energy consumption of servers. Energy savings are typically achieved by setting a well-chosen frequency during some program phases. However, determining suitable program phases and their associated optimal frequencies is a complex problem. Moreover, hardware is constrained by non negligible frequency transition latencies. Thus, various heuristics were proposed to determine and apply frequencies, but evaluating their efficiency remains an issue. In this paper, we translate the energy minimization problem into a mixed integer program that specifically models most current hardware limitations. The problem solution then estimates the minimal energy consumption and the associated frequency schedule. The paper provides two different formulations and a discussion on the feasibility of each of them on realistic applications.