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Sample records for feedwater system reliability

  1. Comparative assessment of selected PWR auxiliary feedwater system reliability analyses

    SciTech Connect

    Youngblood, R.; Fresco, A.; Papazoglou, I.A.; Tsao, J.

    1985-01-01

    This paper presents a sample of results obtained in reviewing utility submittals of Auxiliary Feedwater System reliability studies. These results are then used to illustrate a few general points regarding such studies. The submittals and reviews for operating license applications are quite significant in that they represent an application of probabilistic risk assessment techniques in the licensing process.

  2. Review of the Vogtle Units 1 and 2 Auxiliary Feedwater System reliability analysis

    SciTech Connect

    Fresco, A.; Youngblood, R.; Papazoglou, I.A.

    1985-10-01

    This report presents the results of the review of the Auxiliary Feedwater System reliability analysis for the Vogtle Electric Generating Plant (VEGP) Units 1 and 2. The objective of this report is to estimate the probability that the Auxiliary Feedwater System will fail to perform its mission for each of three different initiators: (1) loss of main feedwater with offsite power available, (2) loss of offsite power, (3) loss of all ac power except vital instrumentation and control 125-V dc/120-V ac power. The scope, methodology, and failure data are prescribed by NUREG-0611, Appendix III. The results are compared with those obtained in NUREG-0611 for other Westinghouse plants.

  3. Review of the Shearon Harris Unit 1 auxiliary feedwater system reliability analysis

    SciTech Connect

    Fresco, A.; Youngblood, R.; Papazoglou, I.A.

    1986-02-01

    This report presents the results of a review of the Auxiliary Feedwater System Reliability Analysis for the Shearon Harris Nuclear Power Plant (SHNPP) Unit 1. The objective of this report is to estimate the probability that the Auxiliary Feedwater System will fail to perform its mission for each of three different initiators: (1) loss of main feedwater with offsite power available, (2) loss of offsite power, (3) loss of all ac power except vital instrumentation and control 125-V dc/120-V ac power. The scope, methodology, and failure data are prescribed by NUREG-0611 for other Westinghouse plants.

  4. Review of the Catawba Units 1 and 2 auxiliary feedwater system reliability analysis

    SciTech Connect

    Fresco, A.; Youngblood, R.; Papazoglou, I.A.

    1983-10-01

    This report presents the results of a review of the Auxiliary Feedwater System Reliability Analysis for Catawba Units 1 and 2. The objective of this report is to estimate the probability that the Auxiliary Feedwater System will fail to perform its mission for each of three different initiators: (1) loss of main feedwater with offsite power available, (2) loss of offsite power, (3) loss of all ac power except for vital instrumentation and control power. The scope, methodology, and failure data are prescribed by NUREG-0611, Appendix III. The results are compared with those obtained in NUREG-0611 for other Westinghouse plants.

  5. Review of the Seabrook Units 1 and 2 auxiliary feedwater system reliability analysis

    SciTech Connect

    Fresco, A.; Youngblood, R.; Papazoglou, I.A.

    1984-02-01

    This report presents the results of a review of the Emergency Feedwater System Reliability Analysis for Seabrook Nuclear Station Units 1 and 2. The objective of this report is to estimate the probability that the Emergency Feedwater System will fail to perform its mission for each of three different initiators: (1) loss of main feedwater with offsite power available, (2) loss of offsite power, (3) loss of all ac power except vital instrumentation and control 125 VDC/120 VAC power. The scope, methodology, and failure data are prescribed by NUREG-0611, Appendix III. The results are compared with those obtained in NUREG-0611 for other Westinghouse plants.

  6. A Markov Model for Assessing the Reliability of a Digital Feedwater Control System

    SciTech Connect

    Chu,T.L.; Yue, M.; Martinez-Guridi, G.; Lehner, J.

    2009-02-11

    A Markov approach has been selected to represent and quantify the reliability model of a digital feedwater control system (DFWCS). The system state, i.e., whether a system fails or not, is determined by the status of the components that can be characterized by component failure modes. Starting from the system state that has no component failure, possible transitions out of it are all failure modes of all components in the system. Each additional component failure mode will formulate a different system state that may or may not be a system failure state. The Markov transition diagram is developed by strictly following the sequences of component failures (i.e., failure sequences) because the different orders of the same set of failures may affect the system in completely different ways. The formulation and quantification of the Markov model, together with the proposed FMEA (Failure Modes and Effects Analysis) approach, and the development of the supporting automated FMEA tool are considered the three major elements of a generic conceptual framework under which the reliability of digital systems can be assessed.

  7. Feedwater temperature control methods and systems

    SciTech Connect

    Moen, Stephan Craig; Noonan, Jack Patrick; Saha, Pradip

    2014-04-22

    A system for controlling the power level of a natural circulation boiling water nuclear reactor (NCBWR) is disclosed. The system, in accordance with an example embodiment of the present invention, may include a controller configured to control a power output level of the NCBWR by controlling a heating subsystem to adjust a temperature of feedwater flowing into an annulus of the NCBWR. The heating subsystem may include a steam diversion line configured to receive steam generated by a core of the NCBWR and a steam bypass valve configured to receive commands from the controller to control a flow of the steam in the steam diversion line, wherein the steam received by the steam diversion line has not passed through a turbine. Additional embodiments of the invention may include a feedwater bypass valve for controlling an amount of flow of the feedwater through a heater bypass line to the annulus.

  8. Condensate and feedwater systems, pumps, and water chemistry. Volume seven

    SciTech Connect

    Not Available

    1986-01-01

    Subject matter includes condensate and feedwater systems (general features of condensate and feedwater systems, condenser hotwell level control, condensate flow, feedwater flow), pumps (principles of fluid flow, types of pumps, centrifugal pumps, positive displacement pumps, jet pumps, pump operating characteristics) and water chemistry (water chemistry fundamentals, corrosion, scaling, radiochemistry, water chemistry control processes, water pretreatment, PWR water chemistry, BWR water chemistry, condenser circulating water chemistry.

  9. System Study: Auxiliary Feedwater 1998-2014

    SciTech Connect

    Schroeder, John Alton

    2015-12-01

    This report presents an unreliability evaluation of the auxiliary feedwater (AFW) system at 69 U.S. commercial nuclear power plants. Demand, run hours, and failure data from fiscal year 1998 through 2014 for selected components were obtained from the Institute of Nuclear Power Operations (INPO) Consolidated Events Database (ICES). The unreliability results are trended for the most recent 10 year period, while yearly estimates for system unreliability are provided for the entire active period. No statistically significant increasing or decreasing trends were identified in the AFW results.

  10. System Study: Auxiliary Feedwater 1998–2013

    SciTech Connect

    Schroeder, John Alton

    2014-12-31

    This report presents an unreliability evaluation of the auxiliary feedwater (AFW) system at 69 U.S. commercial nuclear power plants. Demand, run hours, and failure data from fiscal year 1998 through 2013 for selected components were obtained from the Institute of Nuclear Power Operations (INPO) Consolidated Events Database (ICES). The unreliability results are trended for the most recent 10-year period, while yearly estimates for system unreliability are provided for the entire active period. No statistically significant increasing or decreasing trends were identified in the AFW results.

  11. Design of a Software Sensor for Feedwater Flow Measurement Using a Fuzzy Inference System

    SciTech Connect

    Na, Man Gyun; Shin, Sun Ho; Jung, Dong Won

    2005-06-15

    Venturi meters are used to measure the feedwater flow rate in most current pressurized water reactors. These meters can decrease the thermal performance of nuclear power plants because the feedwater flow rate can be overmeasured due to their fouling phenomena that make corrosion products caused by long-term operation accumulate in the feedwater flow meters. Therefore, in this paper, a software sensor using a fuzzy inference system is developed in order to increase the thermal efficiency by accurately estimating online the feedwater flow rate. The fuzzy inference system to be used for black-box modeling of the feedwater system is equipped with an automatic design algorithm that automates the selection of the input signals to the fuzzy inference system and its fuzzy rule generation including parameter optimization. The proposed algorithm was verified by using the numerical simulation data of the MARS code for Kori Nuclear Power Plant Unit 1 and also the real plant data of Yonggwang Nuclear Power Plant Unit 3. In the simulations using numerical simulation data and real plant data, the relative 2{sigma} errors and the relative maximum error are small enough. The proposed method can be applied successfully to validate and monitor the existing feedwater flow meters.

  12. Modeling a high output marine steam generator feedwater control system which uses parallel turbine-driven feed pumps

    NASA Astrophysics Data System (ADS)

    Qiu, Zhi-Qiang; Zou, Hai; Sun, Jian-Hua

    2008-09-01

    Parallel turbine-driven feedwater pumps are needed when ships travel at high speed. In order to study marine steam generator feedwater control systems which use parallel turbine-driven feed pumps, a mathematical model of marine steam generator feedwater control system was developed which includes mathematical models of two steam generators and parallel turbine-driven feed pumps as well as mathematical models of feedwater pipes and feed regulating valves. The operating condition points of the parallel turbine-driven feed pumps were calculated by the Chebyshev curve fit method. A water level controller for the steam generator and a rotary speed controller for the turbine-driven feed pumps were also included in the model. The accuracy of the mathematical models and their controllers was verified by comparing their results with those from a simulator.

  13. Experimental study on the operational and the cooling performance of the APR+ passive auxiliary feedwater system

    SciTech Connect

    Kang, K. H.; Bae, B. U.; Kim, S.; Cho, Y. J.; Park, Y. S.; Kim, B. D.

    2012-07-01

    The passive auxiliary feedwater system (PAFS) is one of the advanced safety features adopted in the APR+ which is intended to completely replace the conventional active auxiliary feedwater system. The PAFS cools down the steam generator secondary side and eventually removes the decay heat from the reactor core by introducing a natural driving force mechanism; i.e., condensing steam in nearly-horizontal U-tubes submerged inside the passive condensation cooling tank (PCCT). With an aim of validating the cooling and operational performance of the PAFS, the separate effect test, PASCAL (PAFS Condensing Heat Removal Assessment Loop), is being performed to experimentally investigate the condensation heat transfer and natural convection phenomena in the PAFS. A single nearly-horizontal U-tube whose dimension is same as the prototypic U-tube of the APR+ PAFS is simulated in the PASCAL test. By performing the PASCAL test, the major thermal-hydraulic parameters such as local/overall heat transfer coefficients, fluid temperature inside the tube, wall temperature of the tube, and pool temperature distribution in the PCCT were produced not only to evaluate the current condensation heat transfer model but also to present database for the safety analysis related with the PAFS. (authors)

  14. Auxiliary feedwater system aging study. Volume 2, Phase 1: Follow-on study

    SciTech Connect

    Kueck, J.D.

    1993-07-01

    This report documents the results of a Phase I follow-on study of the Auxiliary Feedwater (AFW) System that has been conducted for the US Regulatory Commission`s Nuclear Plant Aging research Program. The Phase I study found a number of significant AFW System functions that are not being adequately tested by conventional test methods and some that are actually being degraded by conventional testing. Thus, it was decided that this follow-on study would focus on these testing omissions nd equipment degradation. The deficiencies in current monitoring and operating practice are categorized and evaluated. Areas of component degradation caused by current practice are discussed. Recommendations are made for improved diagnostic methods and test procedures.

  15. San Onofre/Zion auxiliary feedwater system seismic fault tree modeling

    SciTech Connect

    Najafi, B.; Eide, S.

    1982-02-01

    As part of the study for the seismic evaluation of the San Onofre Unit 1 Auxiliary Feedwater System (AFWS), a fault tree model was developed capable of handling the effect of structural failure of the plant (in the event of an earthquake) on the availability of the AFWS. A compatible fault tree model was developed for the Zion Unit 1 AFWS in order to compare the results of the two systems. It was concluded that if a single failure of the San Onofre Unit 1 AFWS is to be prevented, some weight existing, locally operated locked open manual valves have to be used for isolation of a rupture in specific parts of the AFWS pipings.

  16. Auxiliary feedwater system risk-based inspection guide for the South Texas Project nuclear power plant

    SciTech Connect

    Bumgardner, J.D.; Nickolaus, J.R.; Moffitt, N.E.; Gore, B.F.; Vo, T.V.

    1993-12-01

    In a study sponsored by the US Nuclear Regulatory Commission (NRC), Pacific Northwest Laboratory has developed and applied a methodology for deriving plant-specific risk-based inspection guidance for the auxiliary feedwater (AFW) system at pressurized water reactors that have not undergone probabilistic risk assessment (PRA). This methodology uses existing PRA results and plant operating experience information. Existing PRA-based inspection guidance information recently developed for the NRC for various plants was used to identify generic component failure modes. This information was then combined with plant-specific and industry-wide component information and failure data to identify failure modes and failure mechanisms for the AFW system at the selected plants. South Texas Project was selected as a plant for study. The product of this effort is a prioritized listing of AFW failures which have occurred at the plant and at other PWRs. This listing is intended for use by the NRC inspectors in preparation of inspection plans addressing AFW risk important components at the South Texas Project plant.

  17. Auxiliary feedwater system risk-based inspection guide for the H. B. Robinson nuclear power plant

    SciTech Connect

    Moffitt, N.E.; Lloyd, R.C.; Gore, B.F.; Vo, T.V.; Garner, L.W.

    1993-08-01

    In a study sponsored by the US Nuclear Regulatory Commission (NRC), Pacific Northwest Laboratory has developed and applied a methodology for deriving plant-specific risk-based inspection guidance for the auxiliary feedwater (AFW) system at pressurized water reactors that have not undergone probabilistic risk assessment (PRA). This methodology uses existing PRA results and plant operating experience information. Existing PRA-based inspection guidance information recently developed for the NRC for various plants was used to identify generic component failure modes. This information was then combined with plant-specific and industry-wide component information and failure data to identify failure modes and failure mechanisms for the AFW system at the selected plants. H. B. Robinson was selected as one of a series of plants for study. The product of this effort is a prioritized listing of AFW failures which have occurred at the plant and at other PWRs. This listing is intended for use by NRC inspectors in the preparation of inspection plans addressing AFW risk-important components at the H. B. Robinson plant.

  18. Auxiliary feedwater system risk-based inspection guide for the McGuire nuclear power plant

    SciTech Connect

    Bumgardner, J.D.; Lloyd, R.C.; Moffitt, N.E.; Gore, B.F.; Vo, T.V.

    1994-05-01

    In a study sponsored by the US Nuclear Regulatory Commission (NRC), Pacific Northwest Laboratory has developed and applied a methodology for deriving plant-specific risk-based inspection guidance for the auxiliary feedwater (AFW) system at pressurized water reactors that have not undergone probabilistic risk assessment (PRA). This methodology uses existing PRA results and plant operating experience information. Existing PRA-based inspection guidance information recently developed for the NRC for various plants was used to identify generic component failure modes. This information was then combined with plant-specific and industry-wide component information and failure data to identify failure modes and failure mechanisms for the AFW system at the selected plants. McGuire was selected as one of a series of plants for study. The product of this effort is a prioritized listing of AFW failures which have occurred at the plant and at other PWRs. This listing is intended for use by NRC inspectors in the preparation of inspection plans addressing AFW risk-important components at the McGuire plant.

  19. Auxiliary feedwater system risk-based inspection guide for the J. M. Farley Nuclear Power Plant

    SciTech Connect

    Vo, T.V.; Pugh, R.; Gore, B.F.; Harrison, D.G. )

    1990-10-01

    In a study sponsored by the US Nuclear Regulatory Commission (NRC), Pacific Northwest Laboratory has developed and applied a methodology for deriving plant-specific risk-based inspection guidance for the auxiliary feedwater (AFW) system at pressurized water reactors that have not undergone probabilistic risk assessment(PRA). This methodology uses existing PRA results and plant operating experience information. Existing PRA-based inspection guidance recently developed for the NRC for various plants was used to identify generic component failure modes. This information was then combined with plant-specific and industry-wide component information and failure data to identify failure modes and failure mechanisms for the AFW system at the selected plants. J. M. Farley was selected as the second plant for study. The product of this effort is a prioritized listing of AFW failures which have occurred at the plant and at other PWRs. This listing is intended for use by NRC inspectors in the preparation of inspection plans addressing AFW risk-important at the J. M. Farley plant. 23 refs., 1 fig., 1 tab.

  20. Auxiliary feedwater system risk-based inspection guide for the Ginna Nuclear Power Plant

    SciTech Connect

    Pugh, R.; Gore, B.F.; Vo, T.V.; Moffitt, N.E. )

    1991-09-01

    In a study sponsored by the US Nuclear Regulatory Commission (NRC), Pacific Northwest Laboratory has developed and applied a methodology for deriving plant-specific risk-based inspection guidance for the auxiliary feedwater (AFW) system at pressurized water reactors that have not undergone probabilistic risk assessment (PRA). This methodology uses existing PRA results and plant operating experience information. Existing PRA-based inspection guidance information recently developed for the NRC for various plants was used to identify generic component failure modes. This information was then combined with plant-specific and industry-wide component information and failure data to identify failure modes and failure mechanisms for the AFW system at the selected plants. Ginna was selected as the eighth plant for study. The product of this effort is a prioritized listing of AFW failures which have occurred at the plant and at other PWRs. This listing is intended for use by NRC inspectors in the preparation of inspection plans addressing AFW risk-important components at the Ginna plant. 23 refs., 1 fig., 1 tab.

  1. Auxiliary feedwater system risk-based inspection guide for the Byron and Braidwood nuclear power plants

    SciTech Connect

    Moffitt, N.E.; Gore, B.F.: Vo, T.V. )

    1991-07-01

    In a study sponsored by the US Nuclear Regulatory Commission (NRC), Pacific Northwest Laboratory has developed and applied a methodology for deriving plant-specific risk-based inspection guidance for the auxiliary feedwater (AFW) system at pressurized water reactors that have not undergone probabilistic risk assessment (PRA). This methodology uses existing PRA results and plant operating experience information. Existing PRA-based inspection guidance information recently developed for the NRC for various plants was used to identify generic component failure modes. This information was then combined with plant-specific and industry-wide component information and failure data to identify failure modes and failure mechanisms for the AFW system at the selected plants. Byron and Braidwood were selected for the fourth study in this program. The produce of this effort is a prioritized listing of AFW failures which have occurred at the plants and at other PWRs. This listing is intended for use by NRC inspectors in the preparation of inspection plans addressing AFW risk-important components at the Byron/Braidwood plants. 23 refs., 1 fig., 1 tab.

  2. Auxiliary feedwater system risk-based inspection guide for the Point Beach nuclear power plant

    SciTech Connect

    Lloyd, R C; Moffitt, N E; Gore, B F; Vo, T V; Vehec, T A

    1993-02-01

    In a study sponsored by the US Nuclear Regulatory Commission (NRC), Pacific Northwest Laboratory has developed and applied a methodology for deriving plant-specific risk-based inspection guidance for the auxiliary feedwater (AFW) system at pressurized water reactors that have not undergone probabilistic risk assessment (PRA). This methodology uses existing PRA results and plant operating experience information. Existing PRA-based inspection guidance information recently developed for the NRC for various plants was used to identify generic component failure modes. This information was then combined with plant-specific and industry-wide component information and failure data to identify failure modes and failure mechanisms for the AFW system at the selected plants. Point Beach was selected as one of a series of plants for study. The product of this effort is a prioritized listing of AFW failures which have occurred at the plant and at other PWRS. This listing is intended for use by NRC inspectors in the preparation of inspection plans addressing AFW risk-important components at the Point Beach plant.

  3. Auxiliary feedwater system risk-based inspection guide for the North Anna nuclear power plants

    SciTech Connect

    Nickolaus, J.R.; Moffitt, N.E.; Gore, B.F.; Vo, T.V. )

    1992-10-01

    In a study sponsored by the US Nuclear regulatory Commission (NRC), Pacific Northwest Laboratory has developed and applied a methodology for deriving plant-specific risk-based inspection guidance for the auxiliary feedwater (AFW) system at pressurized water reactors that have not undergone probabilistic risk assessment (PRA). This methodology uses existing PRA results and plant operating experience information. Existing PRA-based inspection guidance information recently developed for the NRC for various plants was used to identify generic component failure modes. This information was then combined with plant-specific and industry-wide component information and failure data to identify failure modes and failure mechanisms for the AFW system at the selected plants. North Anna was selected as a plant for study. The product of this effort is a prioritized listing of AFW failures which have occurred at the plant and at other PWRs. This listing is intended for use by the NRC inspectors in preparation of inspection plans addressing AFW risk important components at the North Anna plant.

  4. Reliability of fluid systems

    NASA Astrophysics Data System (ADS)

    Kopáček, Jaroslav; Fojtášek, Kamil; Dvořák, Lukáš

    2016-03-01

    This paper focuses on the importance of detection reliability, especially in complex fluid systems for demanding production technology. The initial criterion for assessing the reliability is the failure of object (element), which is seen as a random variable and their data (values) can be processed using by the mathematical methods of theory probability and statistics. They are defined the basic indicators of reliability and their applications in calculations of serial, parallel and backed-up systems. For illustration, there are calculation examples of indicators of reliability for various elements of the system and for the selected pneumatic circuit.

  5. Auxiliary feedwater system risk-based inspection guide for the Diablo Canyon Unit 1 Nuclear Power Plant

    SciTech Connect

    Gore, B.F.; Vo, T.V.; Harrison, D.G.

    1990-08-01

    This document presents a compilation of auxiliary feedwater (AFW) system failure information which has been screened for risk significance in terms of failure frequency and degradation of system performance. It is a risk-prioritized listing of failure events and their causes that are significant enough to warrant consideration in inspection planning at Diablo Canyon. This information is presented to provide inspectors with increased resources for inspection planning at Diablo Canyon. The risk importance of various component failure modes was identified by analysis of the results of probabilistic risk assessments (PRAs) for many pressurized water reactors (PWRs). However, the component failure categories identified in PRAs are rather broad, because the failure data used in the PRAs is an aggregate of many individual failures having a variety of root causes. In order to help inspectors to focus on specific aspects of component operation, maintenance and design which might cause these failures, an extensive review of component failure information was performed to identify and rank the root causes of these component failures. Both Diablo Canyon and industry-wide failure information was analyzed. Failure causes were sorted on the basis of frequency of occurrence and seriousness of consequence, and categorized as common cause failures, human errors, design problems, or component failures. This information permits an inspector to concentrate on components important to the prevention of core damage. Other components which perform essential functions, but which are not included because of high reliability or redundancy, must also be addressed to ensure that degradation does not increase their failure probabilities, and hence their risk importances. 23 refs., 1 fig., 1 tab.

  6. Hawaii electric system reliability.

    SciTech Connect

    Silva Monroy, Cesar Augusto; Loose, Verne William

    2012-09-01

    This report addresses Hawaii electric system reliability issues; greater emphasis is placed on short-term reliability but resource adequacy is reviewed in reference to electric consumers' views of reliability %E2%80%9Cworth%E2%80%9D and the reserve capacity required to deliver that value. The report begins with a description of the Hawaii electric system to the extent permitted by publicly available data. Electrical engineering literature in the area of electric reliability is researched and briefly reviewed. North American Electric Reliability Corporation standards and measures for generation and transmission are reviewed and identified as to their appropriateness for various portions of the electric grid and for application in Hawaii. Analysis of frequency data supplied by the State of Hawaii Public Utilities Commission is presented together with comparison and contrast of performance of each of the systems for two years, 2010 and 2011. Literature tracing the development of reliability economics is reviewed and referenced. A method is explained for integrating system cost with outage cost to determine the optimal resource adequacy given customers' views of the value contributed by reliable electric supply. The report concludes with findings and recommendations for reliability in the State of Hawaii.

  7. Photovoltaic system reliability

    SciTech Connect

    Maish, A.B.; Atcitty, C.; Greenberg, D.

    1997-10-01

    This paper discusses the reliability of several photovoltaic projects including SMUD`s PV Pioneer project, various projects monitored by Ascension Technology, and the Colorado Parks project. System times-to-failure range from 1 to 16 years, and maintenance costs range from 1 to 16 cents per kilowatt-hour. Factors contributing to the reliability of these systems are discussed, and practices are recommended that can be applied to future projects. This paper also discusses the methodology used to collect and analyze PV system reliability data.

  8. Multidisciplinary System Reliability Analysis

    NASA Technical Reports Server (NTRS)

    Mahadevan, Sankaran; Han, Song; Chamis, Christos C. (Technical Monitor)

    2001-01-01

    The objective of this study is to develop a new methodology for estimating the reliability of engineering systems that encompass multiple disciplines. The methodology is formulated in the context of the NESSUS probabilistic structural analysis code, developed under the leadership of NASA Glenn Research Center. The NESSUS code has been successfully applied to the reliability estimation of a variety of structural engineering systems. This study examines whether the features of NESSUS could be used to investigate the reliability of systems in other disciplines such as heat transfer, fluid mechanics, electrical circuits etc., without considerable programming effort specific to each discipline. In this study, the mechanical equivalence between system behavior models in different disciplines are investigated to achieve this objective. A new methodology is presented for the analysis of heat transfer, fluid flow, and electrical circuit problems using the structural analysis routines within NESSUS, by utilizing the equivalence between the computational quantities in different disciplines. This technique is integrated with the fast probability integration and system reliability techniques within the NESSUS code, to successfully compute the system reliability of multidisciplinary systems. Traditional as well as progressive failure analysis methods for system reliability estimation are demonstrated, through a numerical example of a heat exchanger system involving failure modes in structural, heat transfer and fluid flow disciplines.

  9. Load Control System Reliability

    SciTech Connect

    Trudnowski, Daniel

    2015-04-03

    This report summarizes the results of the Load Control System Reliability project (DOE Award DE-FC26-06NT42750). The original grant was awarded to Montana Tech April 2006. Follow-on DOE awards and expansions to the project scope occurred August 2007, January 2009, April 2011, and April 2013. In addition to the DOE monies, the project also consisted of matching funds from the states of Montana and Wyoming. Project participants included Montana Tech; the University of Wyoming; Montana State University; NorthWestern Energy, Inc., and MSE. Research focused on two areas: real-time power-system load control methodologies; and, power-system measurement-based stability-assessment operation and control tools. The majority of effort was focused on area 2. Results from the research includes: development of fundamental power-system dynamic concepts, control schemes, and signal-processing algorithms; many papers (including two prize papers) in leading journals and conferences and leadership of IEEE activities; one patent; participation in major actual-system testing in the western North American power system; prototype power-system operation and control software installed and tested at three major North American control centers; and, the incubation of a new commercial-grade operation and control software tool. Work under this grant certainly supported the DOE-OE goals in the area of “Real Time Grid Reliability Management.”

  10. Digital feedwater and recirculation flow control for GPUN Oyster Creek

    SciTech Connect

    Burjorjee, D. ); Gan, B. )

    1992-01-01

    This paper describes the digital system for feedwater and recirculation control that GPU Nuclear will be installing at Oyster Creek during its next outage - expected circa December 1992. The replacement was motivated by considerations of reliability and obsolescence - the analog equipment was aging and reaching the end of its useful life. The new system uses Atomic Energy of Canada Ltd.'s software platform running on dual, redundant, industrial-grade 386 computers with opto-isolated field input/output (I/O) accessed through a parallel bus. The feedwater controller controls three main feed regulating valves, two low flow regulating valves, and two block valves. The recirculation controller drives the five scoop positioners of the hydraulic couplers. The system also drives contacts that lock up the actuators on detecting an open circuit in their current loops.

  11. Ultimately Reliable Pyrotechnic Systems

    NASA Technical Reports Server (NTRS)

    Scott, John H.; Hinkel, Todd

    2015-01-01

    This paper presents the methods by which NASA has designed, built, tested, and certified pyrotechnic devices for high reliability operation in extreme environments and illustrates the potential applications in the oil and gas industry. NASA's extremely successful application of pyrotechnics is built upon documented procedures and test methods that have been maintained and developed since the Apollo Program. Standards are managed and rigorously enforced for performance margins, redundancy, lot sampling, and personnel safety. The pyrotechnics utilized in spacecraft include such devices as small initiators and detonators with the power of a shotgun shell, detonating cord systems for explosive energy transfer across many feet, precision linear shaped charges for breaking structural membranes, and booster charges to actuate valves and pistons. NASA's pyrotechnics program is one of the more successful in the history of Human Spaceflight. No pyrotechnic device developed in accordance with NASA's Human Spaceflight standards has ever failed in flight use. NASA's pyrotechnic initiators work reliably in temperatures as low as -420 F. Each of the 135 Space Shuttle flights fired 102 of these initiators, some setting off multiple pyrotechnic devices, with never a failure. The recent landing on Mars of the Opportunity rover fired 174 of NASA's pyrotechnic initiators to complete the famous '7 minutes of terror.' Even after traveling through extreme radiation and thermal environments on the way to Mars, every one of them worked. These initiators have fired on the surface of Titan. NASA's design controls, procedures, and processes produce the most reliable pyrotechnics in the world. Application of pyrotechnics designed and procured in this manner could enable the energy industry's emergency equipment, such as shutoff valves and deep-sea blowout preventers, to be left in place for years in extreme environments and still be relied upon to function when needed, thus greatly enhancing

  12. Space Shuttle Propulsion System Reliability

    NASA Technical Reports Server (NTRS)

    Welzyn, Ken; VanHooser, Katherine; Moore, Dennis; Wood, David

    2011-01-01

    This session includes the following sessions: (1) External Tank (ET) System Reliability and Lessons, (2) Space Shuttle Main Engine (SSME), Reliability Validated by a Million Seconds of Testing, (3) Reusable Solid Rocket Motor (RSRM) Reliability via Process Control, and (4) Solid Rocket Booster (SRB) Reliability via Acceptance and Testing.

  13. Thermal-hydraulic analysis for changing feedwater check valve leakage rate testing methodology

    SciTech Connect

    Fuller, R.; Harrell, J.

    1996-12-01

    The current design and testing requirements for the feedwater check valves (FWCVs) at the Grand Gulf Nuclear Station are established from original licensing requirements that necessitate extremely restrictive air testing with tight allowable leakage limits. As a direct result of these requirements, the original high endurance hard seats in the FWCVs were modified with elastomeric seals to provide a sealing surface capable of meeting the stringent air leakage limits. However, due to the relatively short functional life of the elastomeric seals compared to the hard seats, the overall reliability of the sealing function actually decreased. This degraded performance was exhibited by frequent seal failures and subsequent valve repairs. The original requirements were based on limited analysis and the belief that all of the high energy feedwater vaporized during the LOCA blowdown. These phenomena would have resulted in completely voided feedwater lines and thus a steam environment within the feedwater leak pathway. To challenge these criteria, a comprehensive design basis accident analysis was developed using the RELAP5/MOD3.1 thermal-hydraulic code. Realistic assumptions were used to more accurately model the post-accident fluid conditions within the feedwater system. The results of this analysis demonstrated that no leak path exists through the feedwater lines during the reactor blowdown phase and that sufficient subcooled water remains in various portions of the feedwater piping to form liquid water loop seals that effectively isolate this leak path. These results provided the bases for changing the leak testing requirements of the FWCVs from air to water. The analysis results also established more accurate allowable leakage limits, determined the real effective margins associated with the FWCV safety functions, and led to design changes that improved the overall functional performance of the valves.

  14. US electric power system reliability

    NASA Astrophysics Data System (ADS)

    Electric energy supply, transmission and distribution systems are investigated in order to determine priorities for legislation. The status and the outlook for electric power reliability are discussed.

  15. Calculating system reliability with SRFYDO

    SciTech Connect

    Morzinski, Jerome; Anderson - Cook, Christine M; Klamann, Richard M

    2010-01-01

    SRFYDO is a process for estimating reliability of complex systems. Using information from all applicable sources, including full-system (flight) data, component test data, and expert (engineering) judgment, SRFYDO produces reliability estimates and predictions. It is appropriate for series systems with possibly several versions of the system which share some common components. It models reliability as a function of age and up to 2 other lifecycle (usage) covariates. Initial output from its Exploratory Data Analysis mode consists of plots and numerical summaries so that the user can check data entry and model assumptions, and help determine a final form for the system model. The System Reliability mode runs a complete reliability calculation using Bayesian methodology. This mode produces results that estimate reliability at the component, sub-system, and system level. The results include estimates of uncertainty, and can predict reliability at some not-too-distant time in the future. This paper presents an overview of the underlying statistical model for the analysis, discusses model assumptions, and demonstrates usage of SRFYDO.

  16. Reliable inverter systems

    NASA Technical Reports Server (NTRS)

    Nagano, S.

    1979-01-01

    Base driver with common-load-current feedback protects paralleled inverter systems from open or short circuits. Circuit eliminates total system oscillation that can occur in conventional inverters because of open circuit in primary transformer winding. Common feedback signal produced by functioning modules forces operating frequency of failed module to coincide with clock drive so module resumes normal operating frequency in spite of open circuit.

  17. Photovoltaic power system reliability considerations

    NASA Technical Reports Server (NTRS)

    Lalli, V. R.

    1980-01-01

    An example of how modern engineering and safety techniques can be used to assure the reliable and safe operation of photovoltaic power systems is presented. This particular application is for a solar cell power system demonstration project designed to provide electric power requirements for remote villages. The techniques utilized involve a definition of the power system natural and operating environment, use of design criteria and analysis techniques, an awareness of potential problems via the inherent reliability and FMEA methods, and use of fail-safe and planned spare parts engineering philosophy.

  18. On Component Reliability and System Reliability for Space Missions

    NASA Technical Reports Server (NTRS)

    Chen, Yuan; Gillespie, Amanda M.; Monaghan, Mark W.; Sampson, Michael J.; Hodson, Robert F.

    2012-01-01

    This paper is to address the basics, the limitations and the relationship between component reliability and system reliability through a study of flight computing architectures and related avionics components for NASA future missions. Component reliability analysis and system reliability analysis need to be evaluated at the same time, and the limitations of each analysis and the relationship between the two analyses need to be understood.

  19. Removable feedwater sparger assembly

    DOEpatents

    Challberg, R.C.

    1994-10-04

    A removable feedwater sparger assembly includes a sparger having an inlet pipe disposed in flow communication with the outlet end of a supply pipe. A tubular coupling includes an annular band fixedly joined to the sparger inlet pipe and a plurality of fingers extending from the band which are removably joined to a retention flange extending from the supply pipe for maintaining the sparger inlet pipe in flow communication with the supply pipe. The fingers are elastically deflectable for allowing engagement of the sparger inlet pipe with the supply pipe and for disengagement therewith. 8 figs.

  20. Removable feedwater sparger assembly

    DOEpatents

    Challberg, Roy C.

    1994-01-01

    A removable feedwater sparger assembly includes a sparger having an inlet pipe disposed in flow communication with the outlet end of a supply pipe. A tubular coupling includes an annular band fixedly joined to the sparger inlet pipe and a plurality of fingers extending from the band which are removably joined to a retention flange extending from the supply pipe for maintaining the sparger inlet pipe in flow communication with the supply pipe. The fingers are elastically deflectable for allowing engagement of the sparger inlet pipe with the supply pipe and for disengagement therewith.

  1. Defining Requirements for Improved Photovoltaic System Reliability

    SciTech Connect

    Maish, A.B.

    1998-12-21

    Reliable systems are an essential ingredient of any technology progressing toward commercial maturity and large-scale deployment. This paper defines reliability as meeting system fictional requirements, and then develops a framework to understand and quantify photovoltaic system reliability based on initial and ongoing costs and system value. The core elements necessary to achieve reliable PV systems are reviewed. These include appropriate system design, satisfactory component reliability, and proper installation and servicing. Reliability status, key issues, and present needs in system reliability are summarized for four application sectors.

  2. An optimized periodic inspection program for condensers and feedwater heaters

    SciTech Connect

    Reinhart, E.R.; Kaminski, S.

    1996-12-31

    Tube failures in steam plant surface condensers and feedwater heaters are a significant reliability problem for the electric power industry. Tube failures can also result in an increase in replacement power costs. In addition, condenser leaks from failed tubes have potentially harmful effects on major components such as steam generators and turbines. To reduce the number of tube failures and consequent leakage, periodic maintenance programs have used the nondestructive evaluation (NDE) method of eddy-current testing (ET) to inspect the condition of the tubes from the water side. This NDE method can identify tubes that have experienced major degradation and should be plugged to prevent in-service failure. However, the use of NDE methods in plant maintenance of condensers and feedwater heaters is not standard practice and varies significantly throughout the utility industry. Variability of inspection results and difficulty in inspecting some types of tubing (monel, carbon steel) have caused many utility sites to question the value of in-service inspection of heat transfer tubing from the water side. Recognizing the above problem, advanced ET systems have been developed that use multi-frequency, remote field and digital data processing techniques to inspect a wide variety of tubing materials and produce on-site inspection reports. Recent field examination results will be presented.

  3. Development of Multi-Stage Steam Injector for Feedwater Heaters in Simplified Nuclear Power Plant

    NASA Astrophysics Data System (ADS)

    Narabayashi, Tadashi; Ohmori, Shuichi; Mori, Michitsugu; Asanuma, Yutaka; Iwaki, Chikako

    A steam injector (SI) is a simple, compact and passive pump and also acts as a high-performance direct-contact compact heater to heat up feedwater by using extracted steam from the turbine. To develop high performance compact feedwater heater, it is necessary to quantify the characteristics between physical properties of the flow field. Its performance depends on the phenomena of steam condensation onto the water jet surface and heat transfer in the water jet due to turbulence on to the phase-interface. The analysis was conducted by using CFD code embedded separate two-phase flow models that were confirmed by the experimental data. As the four-stage SI is compact heater, the system is expected to bring about great simplification and materials-saving effects, and high reliability of its operation. Therefore, it is confirmed that the simplification of the power plant by replacing all low-pressure feedwater heaters with the four-stage SI system, having steam extraction pressures equal to those for the existing ABWR system.

  4. Reliability Evaluation of Passive Systems Through Functional Reliability Assessment

    SciTech Connect

    Burgazzi, Luciano

    2003-11-15

    A methodology, to quantify the reliability of passive safety systems, proposed for use in advanced reactor design, is developed. Passive systems are identified as systems that do not need any external input or energy to operate and rely only upon natural physical laws (e.g., gravity, natural circulation, heat conduction, internally stored energy, etc.) and/or intelligent use of the energy inherently available in the system (e.g., chemical reaction, decay heat, etc.). The reliability of a passive system refers to the ability of the system to carry out the required function under the prevailing condition when required: The passive system may fail its mission, in addition to the classical mechanical failure of its components, for deviation from the expected behavior, due to physical phenomena or to different boundary and initial conditions. The present research activity is finalized at the reliability estimation of passive B systems (i.e., implementing moving working fluids, see IAEA); the selected system is a loop operating in natural circulation including a heat source and a heat sink.The functional reliability concept, defined as the probability to perform the required mission, is introduced, and the R-S (Resistance-Stress) model taken from fracture mechanics is adopted. R and S are coined as expressions of functional Requirement and system State. Water mass flow circulating through the system is accounted as a parameter defining the passive system performance, and probability distribution functions (pdf's) are assigned to both R and S quantities; thus, the mission of the passive system defines which parameter values are considered a failure by comparing the corresponding pdfs according to a defined safety criteria. The methodology, its application, and results of the analysis are presented and discussed.

  5. System and Software Reliability (C103)

    NASA Technical Reports Server (NTRS)

    Wallace, Dolores

    2003-01-01

    Within the last decade better reliability models (hardware. software, system) than those currently used have been theorized and developed but not implemented in practice. Previous research on software reliability has shown that while some existing software reliability models are practical, they are no accurate enough. New paradigms of development (e.g. OO) have appeared and associated reliability models have been proposed posed but not investigated. Hardware models have been extensively investigated but not integrated into a system framework. System reliability modeling is the weakest of the three. NASA engineers need better methods and tools to demonstrate that the products meet NASA requirements for reliability measurement. For the new models for the software component of the last decade, there is a great need to bring them into a form that they can be used on software intensive systems. The Statistical Modeling and Estimation of Reliability Functions for Systems (SMERFS'3) tool is an existing vehicle that may be used to incorporate these new modeling advances. Adapting some existing software reliability modeling changes to accommodate major changes in software development technology may also show substantial improvement in prediction accuracy. With some additional research, the next step is to identify and investigate system reliability. System reliability models could then be incorporated in a tool such as SMERFS'3. This tool with better models would greatly add value in assess in GSFC projects.

  6. 75 FR 71625 - System Restoration Reliability Standards

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-24

    ... Reliability Standards for the Bulk-Power System, Order No. 693, 72 FR 16416 at P 297 (Apr. 4, 2007), FERC... No. 486, 52 FR 47897 (Dec. 17, 1987), FERC Stats. & Regs. ] 30,783 (1987). \\34\\ 18 CFR 380.4(a)(5... Energy Regulatory Commission 18 CFR Part 40 System Restoration Reliability Standards November 18,...

  7. Reliability Growth in Space Life Support Systems

    NASA Technical Reports Server (NTRS)

    Jones, Harry W.

    2014-01-01

    A hardware system's failure rate often increases over time due to wear and aging, but not always. Some systems instead show reliability growth, a decreasing failure rate with time, due to effective failure analysis and remedial hardware upgrades. Reliability grows when failure causes are removed by improved design. A mathematical reliability growth model allows the reliability growth rate to be computed from the failure data. The space shuttle was extensively maintained, refurbished, and upgraded after each flight and it experienced significant reliability growth during its operational life. In contrast, the International Space Station (ISS) is much more difficult to maintain and upgrade and its failure rate has been constant over time. The ISS Carbon Dioxide Removal Assembly (CDRA) reliability has slightly decreased. Failures on ISS and with the ISS CDRA continue to be a challenge.

  8. Production Facility System Reliability Analysis Report

    SciTech Connect

    Dale, Crystal Buchanan; Klein, Steven Karl

    2015-10-06

    This document describes the reliability, maintainability, and availability (RMA) modeling of the Los Alamos National Laboratory (LANL) design for the Closed Loop Helium Cooling System (CLHCS) planned for the NorthStar accelerator-based 99Mo production facility. The current analysis incorporates a conceptual helium recovery system, beam diagnostics, and prototype control system into the reliability analysis. The results from the 1000 hr blower test are addressed.

  9. B-52 stability augmentation system reliability

    NASA Technical Reports Server (NTRS)

    Bowling, T. C.; Key, L. W.

    1976-01-01

    The B-52 SAS (Stability Augmentation System) was developed and retrofitted to nearly 300 aircraft. It actively controls B-52 structural bending, provides improved yaw and pitch damping through sensors and electronic control channels, and puts complete reliance on hydraulic control power for rudder and elevators. The system has experienced over 300,000 flight hours and has exhibited service reliability comparable to the results of the reliability test program. Development experience points out numerous lessons with potential application in the mechanization and development of advanced technology control systems of high reliability.

  10. Reliability Results of NERSC Systems

    SciTech Connect

    Petascale Data Storage Institute; Mokhtarani, Akbar; Mokhtarani, Akbar; Kramer, William; Hick, Jason

    2008-05-27

    In order to address the needs of future scientific applications for storing and accessing large amounts of data in an efficient way, one needs to understand the limitations of current technologies and how they may cause systeminstability or unavailability. A number of factors can impact system availability ranging from facility-wide power outage to a single point of failure such as network switches or global file systems. In addition, individual component failure in a system can degrade the performance of that system. This paper focuses on analyzing both of these factors and their impacts on the computational and storage systems at NERSC. Component failure data presented in this report primarily focuses on disk drive in on of the computational system and tape drive failure in HPSS. NERSC collected available component failure data and system-wide outages for its computational and storage systems over a six-year period and made them available to the HPC community through the Petascale Data Storage Institute.

  11. Multi-Disciplinary System Reliability Analysis

    NASA Technical Reports Server (NTRS)

    Mahadevan, Sankaran; Han, Song

    1997-01-01

    The objective of this study is to develop a new methodology for estimating the reliability of engineering systems that encompass multiple disciplines. The methodology is formulated in the context of the NESSUS probabilistic structural analysis code developed under the leadership of NASA Lewis Research Center. The NESSUS code has been successfully applied to the reliability estimation of a variety of structural engineering systems. This study examines whether the features of NESSUS could be used to investigate the reliability of systems in other disciplines such as heat transfer, fluid mechanics, electrical circuits etc., without considerable programming effort specific to each discipline. In this study, the mechanical equivalence between system behavior models in different disciplines are investigated to achieve this objective. A new methodology is presented for the analysis of heat transfer, fluid flow, and electrical circuit problems using the structural analysis routines within NESSUS, by utilizing the equivalence between the computational quantities in different disciplines. This technique is integrated with the fast probability integration and system reliability techniques within the NESSUS code, to successfully compute the system reliability of multi-disciplinary systems. Traditional as well as progressive failure analysis methods for system reliability estimation are demonstrated, through a numerical example of a heat exchanger system involving failure modes in structural, heat transfer and fluid flow disciplines.

  12. Operational reliability of standby safety systems

    SciTech Connect

    Grant, G.M.; Atwood, C.L.; Gentillon, C.D.

    1995-04-01

    The Idaho National Engineering Laboratory (INEL) is evaluating the operational reliability of several risk-significant standby safety systems based on the operating experience at US commercial nuclear power plants from 1987 through 1993. The reliability assessed is the probability that the system will perform its Probabilistic Risk Assessment (PRA) defined safety function. The quantitative estimates of system reliability are expected to be useful in risk-based regulation. This paper is an overview of the analysis methods and the results of the high pressure coolant injection (HPCI) system reliability study. Key characteristics include (1) descriptions of the data collection and analysis methods, (2) the statistical methods employed to estimate operational unreliability, (3) a description of how the operational unreliability estimates were compared with typical PRA results, both overall and for each dominant failure mode, and (4) a summary of results of the study.

  13. Reliability improvement of distribution systems using SSVR.

    PubMed

    Hosseini, Mehdi; Shayanfar, Heidar Ali; Fotuhi-Firuzabad, Mahmoud

    2009-01-01

    This paper presents a reliability assessment algorithm for distribution systems using a Static Series Voltage Regulator (SSVR). Furthermore, this algorithm considers the effects of Distributed Generation (DG) units, alternative sources, system reconfiguration, load shedding and load adding on distribution system reliability indices. In this algorithm, load points are classified into 8 types and separated restoration times are considered for each class. Comparative studies are conducted to investigate the impacts of DG and alternative source unavailability on the distribution system reliability. For reliability assessment, the customer-oriented reliability indices such as SAIFI, SAIDI, CAIDI ASUI and also load- and energy-oriented indices such as ENS and AENS are evaluated. The effectiveness of the proposed algorithm is examined on the two standard distribution systems consisting of 33 and 69 nodes. The best location of the SSVR in distribution systems is determined based on different reliability indices, separately. Results show that the proposed algorithm is efficient for large-scale radial distribution systems and can accommodate the effects of fault isolation and load restoration. PMID:19006802

  14. a Reliability Evaluation System of Association Rules

    NASA Astrophysics Data System (ADS)

    Chen, Jiangping; Feng, Wanshu; Luo, Minghai

    2016-06-01

    In mining association rules, the evaluation of the rules is a highly important work because it directly affects the usability and applicability of the output results of mining. In this paper, the concept of reliability was imported into the association rule evaluation. The reliability of association rules was defined as the accordance degree that reflects the rules of the mining data set. Such degree contains three levels of measurement, namely, accuracy, completeness, and consistency of rules. To show its effectiveness, the "accuracy-completeness-consistency" reliability evaluation system was applied to two extremely different data sets, namely, a basket simulation data set and a multi-source lightning data fusion. Results show that the reliability evaluation system works well in both simulation data set and the actual problem. The three-dimensional reliability evaluation can effectively detect the useless rules to be screened out and add the missing rules thereby improving the reliability of mining results. Furthermore, the proposed reliability evaluation system is applicable to many research fields; using the system in the analysis can facilitate obtainment of more accurate, complete, and consistent association rules.

  15. Demand Response For Power System Reliability: FAQ

    SciTech Connect

    Kirby, Brendan J

    2006-12-01

    Demand response is the most underutilized power system reliability resource in North America. Technological advances now make it possible to tap this resource to both reduce costs and improve. Misconceptions concerning response capabilities tend to force loads to provide responses that they are less able to provide and often prohibit them from providing the most valuable reliability services. Fortunately this is beginning to change with some ISOs making more extensive use of load response. This report is structured as a series of short questions and answers that address load response capabilities and power system reliability needs. Its objective is to further the use of responsive load as a bulk power system reliability resource in providing the fastest and most valuable ancillary services.

  16. Multiphase reliability analysis of complex systems

    NASA Astrophysics Data System (ADS)

    Azam, Mohammad S.; Tu, Fang; Pattipati, Krishna R.

    2003-08-01

    Modern industrial systems assume different configurations to accomplish multiple objectives during different phases of operation, and the component parameters may also vary from one phase to the next. Consequently, reliability evaluation of complex multi-phased systems is a vital and challenging issue. Maximization of mission reliability of a multi-phase system via optimal asset selection is another key demand; incorporation of optimization issues adds to the complexities of reliability evaluation processes. Introduction of components having self-diagnostics and self-recovery capabilities, along with increased complexity and phase-dependent configuration variations in network architectures, requires new approaches for reliability evaluation. This paper considers the problem of evaluating the reliability of a complex multi-phased system with self-recovery/fault-protection options. The reliability analysis is based on a colored digraph (i.e., multi-functional) model that subsumes fault trees and digraphs as special cases. These models enable system designers to decide on system architecture modifications and to determine the optimum levels of redundancy. A sum of disjoint products (SDP) approach is employed to compute system reliability. We also formulated the problem of optimal asset selection in a multi-phase system as one of maximizing the probability of mission success under random load profiles on components. Different methods (e.g., ordinal optimization, robust design, and nonparametric statistical testing) are explored to solve the problem. The resulting analytical expressions and the software tool are demonstrated on a generic programmable software-controlled switchgear, a data bus controller system and a multi-phase mission involving helicopters.

  17. System Reliability for LED-Based Products

    SciTech Connect

    Davis, J Lynn; Mills, Karmann; Lamvik, Michael; Yaga, Robert; Shepherd, Sarah D; Bittle, James; Baldasaro, Nick; Solano, Eric; Bobashev, Georgiy; Johnson, Cortina; Evans, Amy

    2014-04-07

    Results from accelerated life tests (ALT) on mass-produced commercially available 6” downlights are reported along with results from commercial LEDs. The luminaires capture many of the design features found in modern luminaires. In general, a systems perspective is required to understand the reliability of these devices since LED failure is rare. In contrast, components such as drivers, lenses, and reflector are more likely to impact luminaire reliability than LEDs.

  18. Large-scale systems: Complexity, stability, reliability

    NASA Technical Reports Server (NTRS)

    Siljak, D. D.

    1975-01-01

    After showing that a complex dynamic system with a competitive structure has highly reliable stability, a class of noncompetitive dynamic systems for which competitive models can be constructed is defined. It is shown that such a construction is possible in the context of the hierarchic stability analysis. The scheme is based on the comparison principle and vector Liapunov functions.

  19. 76 FR 16277 - System Restoration Reliability Standards

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-23

    ... System, Order No. 693, 72 FR 16416 (Apr. 4, 2007), FERC Stats. & Regs. ] 31,242, at P 297, order on reh'g...\\ System Restoration Reliability Standards, Notice of Proposed Rulemaking, 75 FR 71625 (Nov. 24, 2010... required. \\29\\ Regulations Implementing the National Environmental Policy Act, Order No. 486, 52 FR...

  20. System reliability analysis through corona testing

    NASA Technical Reports Server (NTRS)

    Lalli, V. R.; Mueller, L. A.; Koutnik, E. A.

    1975-01-01

    A corona vacuum test facility for nondestructive testing of power system components was built in the Reliability and Quality Engineering Test Laboratories at the NASA Lewis Research Center. The facility was developed to simulate operating temperature and vacuum while monitoring corona discharges with residual gases. The facility is being used to test various high-voltage power system components.

  1. Theory of reliable systems. [systems analysis and design

    NASA Technical Reports Server (NTRS)

    Meyer, J. F.

    1973-01-01

    The analysis and design of reliable systems are discussed. The attributes of system reliability studied are fault tolerance, diagnosability, and reconfigurability. Objectives of the study include: to determine properties of system structure that are conducive to a particular attribute; to determine methods for obtaining reliable realizations of a given system; and to determine how properties of system behavior relate to the complexity of fault tolerant realizations. A list of 34 references is included.

  2. Theory of reliable systems. [reliability analysis and on-line fault diagnosis

    NASA Technical Reports Server (NTRS)

    Meyer, J. F.

    1974-01-01

    Research is reported in the program to refine the current notion of system reliability by identifying and investigating attributes of a system which are important to reliability considerations, and to develop techniques which facilitate analysis of system reliability. Reliability analysis, and on-line fault diagnosis are discussed.

  3. Sustainable, Reliable Mission-Systems Architecture

    NASA Technical Reports Server (NTRS)

    O'Neil, Graham; Orr, James K.; Watson, Steve

    2005-01-01

    A mission-systems architecture, based on a highly modular infrastructure utilizing open-standards hardware and software interfaces as the enabling technology is essential for affordable md sustainable space exploration programs. This mission-systems architecture requires (8) robust communication between heterogeneous systems, (b) high reliability, (c) minimal mission-to-mission reconfiguration, (d) affordable development, system integration, end verification of systems, and (e) minimal sustaining engineering. This paper proposes such an architecture. Lessons learned from the Space Shuttle program and Earthbound complex engineered systems are applied to define the model. Technology projections reaching out 5 years are made to refine model details.

  4. Sustainable, Reliable Mission-Systems Architecture

    NASA Technical Reports Server (NTRS)

    O'Neil, Graham; Orr, James K.; Watson, Steve

    2007-01-01

    A mission-systems architecture, based on a highly modular infrastructure utilizing: open-standards hardware and software interfaces as the enabling technology is essential for affordable and sustainable space exploration programs. This mission-systems architecture requires (a) robust communication between heterogeneous system, (b) high reliability, (c) minimal mission-to-mission reconfiguration, (d) affordable development, system integration, and verification of systems, and (e) minimal sustaining engineering. This paper proposes such an architecture. Lessons learned from the Space Shuttle program and Earthbound complex engineered system are applied to define the model. Technology projections reaching out 5 years are mde to refine model details.

  5. Long life reliability thermal control systems study

    NASA Technical Reports Server (NTRS)

    Scollon, T. R., Jr.; Killen, R. E.

    1972-01-01

    The results of a program undertaken to conceptually design and evaluate a passive, high reliability, long life thermal control system for space station application are presented. The program consisted of four steps: (1) investigate and select potential thermal system elements; (2) conceive, evaluate and select a thermal control system using these elements; (3) conduct a verification test of a prototype segment of the selected system; and (4) evaluate the utilization of waste heat from the power supply. The result of this project is a conceptual thermal control system design which employs heat pipes as primary components, both for heat transport and temperature control. The system, its evaluation, and the test results are described.

  6. Structural system reliability under multiple failure modes

    NASA Technical Reports Server (NTRS)

    Mahadevan, S.; Chamis, C. C.

    1993-01-01

    This paper describes a computational method for system reliability estimation of propulsion structures. The failure domain of the entire structural system is computed through the union of failure regions for various critical system failure modes. The effect of non-critical progressive damage is incorporated through structural reanalysis, resulting in the construction of several linear segments to approximately cover the system failure domain. An adaptive damage imposition scheme is outlined for the sake of computational efficiency. The proposed method is used to construct the system survival cdf (cumulative distribution function) of a two-rotor system.

  7. Reliability achievement in high technology space systems

    NASA Technical Reports Server (NTRS)

    Lindstrom, D. L.

    1981-01-01

    The production of failure-free hardware is discussed. The elements required to achieve such hardware are: technical expertise to design, analyze, and fully understand the design; use of high reliability parts and materials control in the manufacturing process; and testing to understand the system and weed out defects. The durability of the Hughes family of satellites is highlighted.

  8. Making real-time reactive systems reliable

    NASA Technical Reports Server (NTRS)

    Marzullo, Keith; Wood, Mark

    1990-01-01

    A reactive system is characterized by a control program that interacts with an environment (or controlled program). The control program monitors the environment and reacts to significant events by sending commands to the environment. This structure is quite general. Not only are most embedded real time systems reactive systems, but so are monitoring and debugging systems and distributed application management systems. Since reactive systems are usually long running and may control physical equipment, fault tolerance is vital. The research tries to understand the principal issues of fault tolerance in real time reactive systems and to build tools that allow a programmer to design reliable, real time reactive systems. In order to make real time reactive systems reliable, several issues must be addressed: (1) How can a control program be built to tolerate failures of sensors and actuators. To achieve this, a methodology was developed for transforming a control program that references physical value into one that tolerates sensors that can fail and can return inaccurate values; (2) How can the real time reactive system be built to tolerate failures of the control program. Towards this goal, whether the techniques presented can be extended to real time reactive systems is investigated; and (3) How can the environment be specified in a way that is useful for writing a control program. Towards this goal, whether a system with real time constraints can be expressed as an equivalent system without such constraints is also investigated.

  9. Reliability systems for implantable cardiac defibrillator batteries

    NASA Astrophysics Data System (ADS)

    Takeuchi, Esther S.

    The reliability of the power sources used in implantable cardiac defibrillators is critical due to the life-saving nature of the device. Achieving a high reliability power source depends on several systems functioning together. Appropriate cell design is the first step in assuring a reliable product. Qualification of critical components and of the cells using those components is done prior to their designation as implantable grade. Product consistency is assured by control of manufacturing practices and verified by sampling plans using both accelerated and real-time testing. Results to date show that lithium/silver vanadium oxide cells used for implantable cardiac defibrillators have a calculated maximum random failure rate of 0.005% per test month.

  10. Reliability Issues in Stirling Radioisotope Power Systems

    NASA Technical Reports Server (NTRS)

    Shah, Ashwin R.; Schreiber, Jeffrey G.

    2004-01-01

    Stirling power conversion is a potential candidate for use in a Radioisotope Power System (RPS) for space science missions because it offers a multifold increase in the conversion efficiency of heat to electric power and reduced requirement of radioactive material. Reliability of an RPS that utilizes Stirling power conversion technology is important in order to ascertain long term successful performance. Owing to long life time requirement (14 years), it is difficult to perform long-term tests that encompass all the uncertainties involved in the design variables of components and subsystems comprising the RPS. The requirement for uninterrupted performance reliability and related issues are discussed, and some of the critical areas of concern are identified. An overview of the current on-going efforts to understand component life, design variables at the component and system levels, and related sources and nature of uncertainties are also discussed. Current status of the 110 watt Stirling Radioisotope Generator (SRG110) reliability efforts is described. Additionally, an approach showing the use of past experience on other successfully used power systems to develop a reliability plan for the SRG110 design is outlined.

  11. Reliability Issues in Stirling Radioisotope Power Systems

    NASA Technical Reports Server (NTRS)

    Schreiber, Jeffrey; Shah, Ashwin

    2005-01-01

    Stirling power conversion is a potential candidate for use in a Radioisotope Power System (RPS) for space science missions because it offers a multifold increase in the conversion efficiency of heat to electric power and reduced requirement of radioactive material. Reliability of an RPS that utilizes Stirling power conversion technology is important in order to ascertain long term successful performance. Owing to long life time requirement (14 years), it is difficult to perform long-term tests that encompass all the uncertainties involved in the design variables of components and subsystems comprising the RPS. The requirement for uninterrupted performance reliability and related issues are discussed, and some of the critical areas of concern are identified. An overview of the current on-going efforts to understand component life, design variables at the component and system levels, and related sources and nature of uncertainties are also discussed. Current status of the 110 watt Stirling Radioisotope Generator (SRG110) reliability efforts is described. Additionally, an approach showing the use of past experience on other successfully used power systems to develop a reliability plan for the SRG110 design is outlined.

  12. Reliability mechanisms in distributed data base systems

    SciTech Connect

    Son, S.H.

    1986-01-01

    Distributed database systems operate in computer networking environments where component failures are inevitable during normal operation. Failures not only threaten normal operation of the system, but they may destroy the correctness of the data base by direct damage to the storage subsystem. In order to cope with these failures, distributed data base systems must provide reliability mechanisms that maintain the system consistency. There are two major parts in this dissertation. In the first part, mechanisms are presented for recovery management in distributed data base system. The recovery management of a distributed data bases system consists of two parts: the preparation for the recovery by saving necessary information during normal operation of the data base system, and the coordination of the actual recovery in order to avoid the possible inconsistency after the recovery. The preparation for the recovery is done through the checkpointing and logging. A new scheme is proposed for reconstruction of the data base in distributed environments. In the second part, a token-based resiliency control scheme for replicated distributed data base systems. The proposed control scheme increases the reliability as well as the degree of concurrency while maintaining the consistency of the system.

  13. Subsea pipeline isolation systems: Reliability and costs

    SciTech Connect

    Masheder, R.R.

    1996-08-01

    Since the Piper Alpha disaster, more than 80 subsea isolation systems (SSIS) have been installed in subsea gas and oil pipelines in the U.K. continental shelf at an estimated cost in the region of {Brit_pounds}500 million. The reliability and costs of these installations have now been assessed between Dec. 1992 and Oct. 1993. This assessment was based upon comprehensive reliability and cost databases which were established so that the studies could be based upon factual information in order to obtain a current status as required by the sponsoring group. The study consultants report findings have now been consolidated into a report by the UKOOA Pipeline Valve Work Group. Probabilities of failure for different types of valves and systems have been assessed and expenditures broken down and compared. The results of the studies and the conclusions drawn by UKOOA Pipeline Valve Group and the HSE Offshore Safety Division are presented in this paper.

  14. Mass and Reliability System (MaRS)

    NASA Technical Reports Server (NTRS)

    Barnes, Sarah

    2016-01-01

    The Safety and Mission Assurance (S&MA) Directorate is responsible for mitigating risk, providing system safety, and lowering risk for space programs from ground to space. The S&MA is divided into 4 divisions: The Space Exploration Division (NC), the International Space Station Division (NE), the Safety & Test Operations Division (NS), and the Quality and Flight Equipment Division (NT). The interns, myself and Arun Aruljothi, will be working with the Risk & Reliability Analysis Branch under the NC Division's. The mission of this division is to identify, characterize, diminish, and communicate risk by implementing an efficient and effective assurance model. The team utilizes Reliability and Maintainability (R&M) and Probabilistic Risk Assessment (PRA) to ensure decisions concerning risks are informed, vehicles are safe and reliable, and program/project requirements are realistic and realized. This project pertains to the Orion mission, so it is geared toward a long duration Human Space Flight Program(s). For space missions, payload is a critical concept; balancing what hardware can be replaced by components verse by Orbital Replacement Units (ORU) or subassemblies is key. For this effort a database was created that combines mass and reliability data, called Mass and Reliability System or MaRS. The U.S. International Space Station (ISS) components are used as reference parts in the MaRS database. Using ISS components as a platform is beneficial because of the historical context and the environment similarities to a space flight mission. MaRS uses a combination of systems: International Space Station PART for failure data, Vehicle Master Database (VMDB) for ORU & components, Maintenance & Analysis Data Set (MADS) for operation hours and other pertinent data, & Hardware History Retrieval System (HHRS) for unit weights. MaRS is populated using a Visual Basic Application. Once populated, the excel spreadsheet is comprised of information on ISS components including

  15. System statistical reliability model and analysis

    NASA Technical Reports Server (NTRS)

    Lekach, V. S.; Rood, H.

    1973-01-01

    A digital computer code was developed to simulate the time-dependent behavior of the 5-kwe reactor thermoelectric system. The code was used to determine lifetime sensitivity coefficients for a number of system design parameters, such as thermoelectric module efficiency and degradation rate, radiator absorptivity and emissivity, fuel element barrier defect constant, beginning-of-life reactivity, etc. A probability distribution (mean and standard deviation) was estimated for each of these design parameters. Then, error analysis was used to obtain a probability distribution for the system lifetime (mean = 7.7 years, standard deviation = 1.1 years). From this, the probability that the system will achieve the design goal of 5 years lifetime is 0.993. This value represents an estimate of the degradation reliability of the system.

  16. Design philosophy for reliable systems, including control

    SciTech Connect

    Gabriel, J.R.

    1984-04-01

    In the past, use of computers and software to manage physical plant has usually involved systems similar to the clockwork automata of the 17th century. The next generation of plant control will include intelligent systems - computer systems having knowledge of the plant and being capable of intelligent behavior, even though only some control functions will need such expertise. This report develops a framework for a universe of discourse usable by such non-human experts. It is based on the idea that a design has many features of a contract and may be described as a contract between humans and a machine, defining what each must do to attain a goal. Several points are discussed: the use of techniques in analytical redundancy and their place as analogues in administrative control for conventional techniques in physical control; the use of redundant computer systems to protect against hardware faults; the necessity to prove properties of software used in redundant hardware, because software faults are common modes across redundant hardware; and some issues in choosing a programming language for provable control software. Because proof of correctness is costly, it should be used only where necessary. This report concludes that the degree of reliability needed by the plant model used in analytic redundancy protection need not be nearly as reliable as the mechanism to detect discrepancy between plant and model.

  17. Pump system characterization and reliability enhancement

    SciTech Connect

    Staunton, R.H.

    1997-09-01

    Pump characterization studies were performed at the Oak Ridge National Laboratory (ORNL) to review and analyze six years (1990 to 1995) of data from pump systems at domestic nuclear plants. The studies considered not only pumps and pump motors but also pump related circuit breakers and turbine drives (i.e., the pump system). One significant finding was that the number of significant failures of the pump circuit breaker exceeds the number of significant failures of the pump itself. The study also shows how regulatory code testing was designed for the pump only and therefore did not lead to the discovery of other significant pump system failures. Potential diagnostic technologies both experimental and mature, suitable for on-line and off-line pump testing were identified. The study does not select or recommend technologies but proposes diagnostic technologies and monitoring techniques that should be further evaluated/developed for making meaningful and critically needed improvements in the reliability of the pump system.

  18. SLAC modulator system improvements and reliability results

    SciTech Connect

    Donaldson, A.R.

    1998-06-01

    In 1995, an improvement project was completed on the 244 klystron modulators in the linear accelerator. The modulator system has been previously described. This article offers project details and their resulting effect on modulator and component reliability. Prior to the project, the authors had collected four operating cycles (1991 through 1995) of MTTF data. In this discussion, the '91 data will be excluded since the modulators operated at 60 Hz. The five periods following the '91 run were reviewed due to the common repetition rate at 120 Hz.

  19. Fault tolerant highly reliable inertial navigation system

    NASA Astrophysics Data System (ADS)

    Jeerage, Mahesh; Boettcher, Kevin

    This paper describes a development of failure detection and isolation (FDI) strategies for highly reliable inertial navigation systems. FDI strategies are developed based on the generalized likelihood ratio test (GLRT). A relationship between detection threshold and false alarm rate is developed in terms of the sensor parameters. A new method for correct isolation of failed sensors is presented. Evaluation of FDI performance parameters, such as false alarm rate, wrong isolation probability, and correct isolation probability, are presented. Finally a fault recovery scheme capable of correcting false isolation of good sensors is presented.

  20. Reliable timing systems for computer controlled accelerators

    NASA Astrophysics Data System (ADS)

    Knott, Jürgen; Nettleton, Robert

    1986-06-01

    Over the past decade the use of computers has set new standards for control systems of accelerators with ever increasing complexity coupled with stringent reliability criteria. In fact, with very slow cycling machines or storage rings any erratic operation or timing pulse will cause the loss of precious particles and waste hours of time and effort of preparation. Thus, for the CERN linac and LEAR (Low Energy Antiproton Ring) timing system reliability becomes a crucial factor in the sense that all components must operate practically without fault for very long periods compared to the effective machine cycle. This has been achieved by careful selection of components and design well below thermal and electrical limits, using error detection and correction where possible, as well as developing "safe" decoding techniques for serial data trains. Further, consistent structuring had to be applied in order to obtain simple and flexible modular configurations with very few components on critical paths and to minimize the exchange of information to synchronize accelerators. In addition, this structuring allows the development of efficient strategies for on-line and off-line fault diagnostics. As a result, the timing system for Linac 2 has, so far, been operating without fault for three years, the one for LEAR more than one year since its final debugging.

  1. Reliability of dynamic systems under limited information.

    SciTech Connect

    Field, Richard V., Jr.; Grigoriu, Mircea

    2006-09-01

    A method is developed for reliability analysis of dynamic systems under limited information. The available information includes one or more samples of the system output; any known information on features of the output can be used if available. The method is based on the theory of non-Gaussian translation processes and is shown to be particularly suitable for problems of practical interest. For illustration, we apply the proposed method to a series of simple example problems and compare with results given by traditional statistical estimators in order to establish the accuracy of the method. It is demonstrated that the method delivers accurate results for the case of linear and nonlinear dynamic systems, and can be applied to analyze experimental data and/or mathematical model outputs. Two complex applications of direct interest to Sandia are also considered. First, we apply the proposed method to assess design reliability of a MEMS inertial switch. Second, we consider re-entry body (RB) component vibration response during normal re-entry, where the objective is to estimate the time-dependent probability of component failure. This last application is directly relevant to re-entry random vibration analysis at Sandia, and may provide insights on test-based and/or model-based qualification of weapon components for random vibration environments.

  2. Integrated Reliability and Risk Analysis System (IRRAS)

    SciTech Connect

    Russell, K D; McKay, M K; Sattison, M.B. Skinner, N.L.; Wood, S T; Rasmuson, D M

    1992-01-01

    The Integrated Reliability and Risk Analysis System (IRRAS) is a state-of-the-art, microcomputer-based probabilistic risk assessment (PRA) model development and analysis tool to address key nuclear plant safety issues. IRRAS is an integrated software tool that gives the user the ability to create and analyze fault trees and accident sequences using a microcomputer. This program provides functions that range from graphical fault tree construction to cut set generation and quantification. Version 1.0 of the IRRAS program was released in February of 1987. Since that time, many user comments and enhancements have been incorporated into the program providing a much more powerful and user-friendly system. This version has been designated IRRAS 4.0 and is the subject of this Reference Manual. Version 4.0 of IRRAS provides the same capabilities as Version 1.0 and adds a relational data base facility for managing the data, improved functionality, and improved algorithm performance.

  3. Distribution system reliability assessment using hierarchical Markov modeling

    SciTech Connect

    Brown, R.E.; Gupta, S.; Christie, R.D.; Venkata, S.S.; Fletcher, R.

    1996-10-01

    Distribution system reliability assessment is concerned with power availability and power quality at each customer`s service entrance. This paper presents a new method, termed Hierarchical Markov Modeling (HMM), which can perform predictive distribution system reliability assessment. HMM is unique in that it decomposes the reliability model based on system topology, integrated protection systems, and individual protection devices. This structure, which easily accommodates the effects of backup protection, fault isolation, and load restoration, is compared to simpler reliability models. HMM is then used to assess the reliability of an existing utility distribution system and to explore the reliability impact of several design improvement options.

  4. Reliability analysis of the combined district heating systems

    NASA Astrophysics Data System (ADS)

    Sharapov, V. I.; Orlov, M. E.; Kunin, M. V.

    2015-12-01

    Technologies that improve the reliability and efficiency of the combined district heating systems in urban areas are considered. The calculation method of reliability of the CHP combined district heating systems is proposed. The comparative estimation of the reliability of traditional and combined district heating systems is performed.

  5. Evaluation Applied to Reliability Analysis of Reconfigurable, Highly Reliable, Fault-Tolerant, Computing Systems for Avionics

    NASA Technical Reports Server (NTRS)

    Migneault, G. E.

    1979-01-01

    Emulation techniques are proposed as a solution to a difficulty arising in the analysis of the reliability of highly reliable computer systems for future commercial aircraft. The difficulty, viz., the lack of credible precision in reliability estimates obtained by analytical modeling techniques are established. The difficulty is shown to be an unavoidable consequence of: (1) a high reliability requirement so demanding as to make system evaluation by use testing infeasible, (2) a complex system design technique, fault tolerance, (3) system reliability dominated by errors due to flaws in the system definition, and (4) elaborate analytical modeling techniques whose precision outputs are quite sensitive to errors of approximation in their input data. The technique of emulation is described, indicating how its input is a simple description of the logical structure of a system and its output is the consequent behavior. The use of emulation techniques is discussed for pseudo-testing systems to evaluate bounds on the parameter values needed for the analytical techniques.

  6. Reliable, efficient systems for biomedical research facility

    SciTech Connect

    Basso, P.

    1997-05-01

    Medical Sciences Research Building III (MSRB III) is a 10-story, 207,000 ft{sup 2} (19,230 m{sup 2}) biomedical research facility on the campus of the University of Michigan. The design of MSRB III required a variety of technological solutions to complex design issues. The systems also had to accommodate future modifications. Closely integrated, modular systems with a high degree of flexibility were designed to respond to this requirement. Additionally, designs were kept as simple as possible for operation and maintenance personnel. Integrated electronic controls were used to provide vital data during troubleshooting and maintenance procedures. Equipment was also specified that provides reliability and minimizes maintenance. Other features include 100% redundancy of all central equipment servicing the animal housing area; redundant temperature controls for each individual animal housing room for fail-safe operation to protect the animals against overheating; and accessibility to all items requiring maintenance through an above-ceiling coordination process. It is critical that the engineering systems for MSRB III provide a safe, comfortable, energy efficient environment. The achievement of this design intent was noted by the University`s Commissioning Review Committee which stated: The Commissioning Process performed during both the design phase and construction phase of MSRB III was a significant success, providing an efficiently functioning facility that has been built in accordance with its design intent.

  7. Augmenting system reliability analyses with observation priors

    SciTech Connect

    Lawrence, Earl; Anderson-cook, Christine

    2009-01-01

    Occasionally, a system may fail a test without an obvious component being at fault. Instead, experts may know that at least one of a set of components has failed, but there is uncertainty about which members in the set were the actual failures. When no further information is available, this missing data may be imputed using standard data augmentation (DA). This process is already used in the current implementation of the JMP complex-system reliability modeling codes. In some cases when this situation arises, there may be some supplemental information about the nature of the failure that suggests which subset of components are more likely to have failed. the behavior of the system during the failure may make certain components more likely candidates, and lead the engineering experts to have certain prior beliefs about what occurred. In this case, it is still known that at least one of a set of components failed, but the experts have some idea that certain failure scenarios are more likely than others. This white paper addresses this situation by modifying the imputation process of data augmentation through the use of an observation prior. This prior is specific to particular observations, and a given outcome which is repeated several times could potentially have different observation priors associated with each occurrence.

  8. Mechanical system reliability for long life space systems

    NASA Technical Reports Server (NTRS)

    Kowal, Michael T.

    1994-01-01

    The creation of a compendium of mechanical limit states was undertaken in order to provide a reference base for the application of first-order reliability methods to mechanical systems in the context of the development of a system level design methodology. The compendium was conceived as a reference source specific to the problem of developing the noted design methodology, and not an exhaustive or exclusive compilation of mechanical limit states. The compendium is not intended to be a handbook of mechanical limit states for general use. The compendium provides a diverse set of limit-state relationships for use in demonstrating the application of probabilistic reliability methods to mechanical systems. The compendium is to be used in the reliability analysis of moderately complex mechanical systems.

  9. Reliability design for impact vibration of hydraulic pressure pipeline systems

    NASA Astrophysics Data System (ADS)

    Zhang, Tianxiao; Liu, Xinhui

    2013-09-01

    The research of reliability design for impact vibration of hydraulic pressure pipeline systems is still in the primary stage, and the research of quantitative reliability of hydraulic components and system is still incomplete. On the condition of having obtained the numerical characteristics of basic random parameters, several techniques and methods including the probability statistical theory, hydraulic technique and stochastic perturbation method are employed to carry out the reliability design for impact vibration of the hydraulic pressure system. Considering the instantaneous pressure pulse of hydraulic impact in pipeline, the reliability analysis model of hydraulic pipeline system is established, and the reliability-based optimization design method is presented. The proposed method can reflect the inherent reliability of hydraulic pipe system exactly, and the desired result is obtained. The reliability design of hydraulic pipeline system is achieved by computer programs and the reliability design information of hydraulic pipeline system is obtained. This research proposes a reliability design method, which can solve the problem of the reliability-based optimization design for the hydraulic pressure system with impact vibration practically and effectively, and enhance the quantitative research on the reliability design of hydraulic pipeline system. The proposed method has generality for the reliability optimization design of hydraulic pipeline system.

  10. Decomposition in reliability analysis of fault-tolerant systems

    NASA Technical Reports Server (NTRS)

    Trivedi, K. S.; Geist, R. M.

    1983-01-01

    The existing approaches to reliability modeling are briefly reviewed. An examination of the limitations of the existing approaches in modeling ultrareliable fault-tolerant systems illustrates the need to use decomposition techniques. The notion of behavioral decomposition is introduced for dealing with reliability models with a large number of states, and a series of examples is presented. The CARE (computer-aided reliability estimation) and HARP (hybrid automated reliability predictor) approaches to reliability are discussed.

  11. 76 FR 42534 - Mandatory Reliability Standards for Interconnection Reliability Operating Limits; System...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-19

    ... Reliability Operating Limits; System Restoration Reliability Standards AGENCY: Federal Energy Regulatory... system studies to allow the calculation of IROLs. See NERC Glossary available at http://www.nerc.com/docs... distribution providers to ensure that plans, facilities, and personnel are prepared to enable...

  12. Development of distribution system reliability and risk analysis models

    NASA Astrophysics Data System (ADS)

    Northcote-Green, J. E. D.; Vismor, T. D.; Brooks, C. L.

    1981-08-01

    The overall objectives of a research project were to: determine distribution reliability assessment methods currently used by the industry; develop a general outage reporting scheme suitable for a wide variety of distributing utilities (reliability model); develop a model for predicting the reliability of future system configurations (risk model); and compile a handbook of reliability assessment methods designed specifically for use by the practicing distribution engineer. Emphasis was placed on compiling and organizing reliability assessment techniques presently used by the industry. The project examined reliability evaluation from two perspectives: historical and predictive assessment. Two reliability assessment models, HISRAM - the historical reliability assessment model and PRAM - the predictive reliability assessment model were developed. Each model was tested in a utility environment by the Duquesne Light Company and the Public Service Electric and Gas Company of New Jersey. A survey of 56 diverse utilities served as a basis for examining current distribution reliability assessment practices in the electric power industry.

  13. SMART reliability mechanism for very large storage systems

    NASA Astrophysics Data System (ADS)

    Luo, Dongjian; Zhong, Haifeng; Pei, Canhao; Wu, Wei; Zhang, Chengfeng

    2008-12-01

    In this paper, we investigate the reliability in a petabyte scale storage system built from thousands of Object-Based Storage Devices and study the mechanisms to protect data loss when disk failure happens. We delve in two underlying redundancy mechanisms: 2-way mirroring, 3-way mirroring. To accelerate data reconstruction, Fast Mirroring Copy is employed where the reconstructed objects are stored on different OBSDs throughout the system. A SMART reliability for enhancing the reliability in very large-scale storage system is proposed. Results show that our SMART Reliability Mechanism can utilize the spare resources (including processing, network, and storage resources) to improve the reliability in very large storage systems.

  14. Reliability Sensitivity for ROTOR-STATOR Systems with Rubbing

    NASA Astrophysics Data System (ADS)

    Zhang, Y. M.; Wen, B. C.; Liu, Q. L.

    2003-01-01

    On the basis of the dynamic equations of the Jeffcott rotor-stator model with imbalance, the reliability sensitivity of the rotor-stator systems with rubbing is examined. A statistical fourth moment method is developed to determine the first four moments of system response and state function. The distribution function of the system state function is approximately determined by the standard normal distribution functions using the Edgeworth series technique. The reliability and reliability sensitivity are obtained and the effect on reliability and reliability sensitivity of shaft stiffness and damping, stator stiffness and damping, radial clearance and stator radial stiffness is studied. Numerical results are also presented and discussed.

  15. Preparation and reactivity of lepidocrocite under simulated feedwater conditions

    SciTech Connect

    McGarvey, G.B.; Burnett, K.B.; Owen, D.G.

    1998-02-01

    Lepidocrocite ({gamma}-FeOOH), prepared using several different aging temperatures and aging times, possesses widely varying morphological and structural features. Mean particle dimensions and surface areas were all found to depend on the conditions of the synthesis. Studies of the aqueous reduction of several of the lepidocrocite samples to magnetite indicated that the initial steps in the dissolution-reprecipitation process were influenced by the crystallinity of the material. Results of the morphological studies and the transformation reaction studies are described within the context of corrosion-product generation and stability in secondary feedwater systems of pressurized heavy-water nuclear reactors.

  16. User's guide to the Reliability Estimation System Testbed (REST)

    NASA Technical Reports Server (NTRS)

    Nicol, David M.; Palumbo, Daniel L.; Rifkin, Adam

    1992-01-01

    The Reliability Estimation System Testbed is an X-window based reliability modeling tool that was created to explore the use of the Reliability Modeling Language (RML). RML was defined to support several reliability analysis techniques including modularization, graphical representation, Failure Mode Effects Simulation (FMES), and parallel processing. These techniques are most useful in modeling large systems. Using modularization, an analyst can create reliability models for individual system components. The modules can be tested separately and then combined to compute the total system reliability. Because a one-to-one relationship can be established between system components and the reliability modules, a graphical user interface may be used to describe the system model. RML was designed to permit message passing between modules. This feature enables reliability modeling based on a run time simulation of the system wide effects of a component's failure modes. The use of failure modes effects simulation enhances the analyst's ability to correctly express system behavior when using the modularization approach to reliability modeling. To alleviate the computation bottleneck often found in large reliability models, REST was designed to take advantage of parallel processing on hypercube processors.

  17. Reliability techniques for combined hardware and software systems

    NASA Astrophysics Data System (ADS)

    Friedman, M. A.; Tran, P. Y.; Goddard, P. L.

    1992-02-01

    Techniques were developed for reliability prediction, allocation, growth and demonstration testing of systems that contain both hardware and software. The techniques are compatible with existing hardware reliability concepts, standards and procedures. A draft DOD-HDBK containing the various reliability techniques was also prepared as a part of this study effort. It is intended that the study results and handbook will form the basis for an approved DOD Handbook on software reliability assessment.

  18. Expert system for UNIX system reliability and availability enhancement

    NASA Astrophysics Data System (ADS)

    Xu, Catherine Q.

    1993-02-01

    Highly reliable and available systems are critical to the airline industry. However, most off-the-shelf computer operating systems and hardware do not have built-in fault tolerant mechanisms, the UNIX workstation is one example. In this research effort, we have developed a rule-based Expert System (ES) to monitor, command, and control a UNIX workstation system with hot-standby redundancy. The ES on each workstation acts as an on-line system administrator to diagnose, report, correct, and prevent certain types of hardware and software failures. If a primary station is approaching failure, the ES coordinates the switch-over to a hot-standby secondary workstation. The goal is to discover and solve certain fatal problems early enough to prevent complete system failure from occurring and therefore to enhance system reliability and availability. Test results show that the ES can diagnose all targeted faulty scenarios and take desired actions in a consistent manner regardless of the sequence of the faults. The ES can perform designated system administration tasks about ten times faster than an experienced human operator. Compared with a single workstation system, our hot-standby redundancy system downtime is predicted to be reduced by more than 50 percent by using the ES to command and control the system.

  19. Expert System for UNIX System Reliability and Availability Enhancement

    NASA Technical Reports Server (NTRS)

    Xu, Catherine Q.

    1993-01-01

    Highly reliable and available systems are critical to the airline industry. However, most off-the-shelf computer operating systems and hardware do not have built-in fault tolerant mechanisms, the UNIX workstation is one example. In this research effort, we have developed a rule-based Expert System (ES) to monitor, command, and control a UNIX workstation system with hot-standby redundancy. The ES on each workstation acts as an on-line system administrator to diagnose, report, correct, and prevent certain types of hardware and software failures. If a primary station is approaching failure, the ES coordinates the switch-over to a hot-standby secondary workstation. The goal is to discover and solve certain fatal problems early enough to prevent complete system failure from occurring and therefore to enhance system reliability and availability. Test results show that the ES can diagnose all targeted faulty scenarios and take desired actions in a consistent manner regardless of the sequence of the faults. The ES can perform designated system administration tasks about ten times faster than an experienced human operator. Compared with a single workstation system, our hot-standby redundancy system downtime is predicted to be reduced by more than 50 percent by using the ES to command and control the system.

  20. The 747 primary flight control systems reliability and maintenance study

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The major operational characteristics of the 747 Primary Flight Control Systems (PFCS) are described. Results of reliability analysis for separate control functions are presented. The analysis makes use of a NASA computer program which calculates reliability of redundant systems. Costs for maintaining the 747 PFCS in airline service are assessed. The reliabilities and cost will provide a baseline for use in trade studies of future flight control system design.

  1. Trends in reliability modeling technology for fault tolerant systems

    NASA Technical Reports Server (NTRS)

    Bavuso, S. J.

    1979-01-01

    Reliability modeling for fault tolerant avionic computing systems was developed. The modeling of large systems involving issues of state size and complexity, fault coverage, and practical computation was discussed. A novel technique which provides the tool for studying the reliability of systems with nonconstant failure rates is presented. The fault latency which may provide a method of obtaining vital latent fault data is measured.

  2. Comprehensive Design Reliability Activities for Aerospace Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Christenson, R. L.; Whitley, M. R.; Knight, K. C.

    2000-01-01

    This technical publication describes the methodology, model, software tool, input data, and analysis result that support aerospace design reliability studies. The focus of these activities is on propulsion systems mechanical design reliability. The goal of these activities is to support design from a reliability perspective. Paralleling performance analyses in schedule and method, this requires the proper use of metrics in a validated reliability model useful for design, sensitivity, and trade studies. Design reliability analysis in this view is one of several critical design functions. A design reliability method is detailed and two example analyses are provided-one qualitative and the other quantitative. The use of aerospace and commercial data sources for quantification is discussed and sources listed. A tool that was developed to support both types of analyses is presented. Finally, special topics discussed include the development of design criteria, issues of reliability quantification, quality control, and reliability verification.

  3. Optimization of life support systems and their systems reliability

    NASA Technical Reports Server (NTRS)

    Fan, L. T.; Hwang, C. L.; Erickson, L. E.

    1971-01-01

    The identification, analysis, and optimization of life support systems and subsystems have been investigated. For each system or subsystem that has been considered, the procedure involves the establishment of a set of system equations (or mathematical model) based on theory and experimental evidences; the analysis and simulation of the model; the optimization of the operation, control, and reliability; analysis of sensitivity of the system based on the model; and, if possible, experimental verification of the theoretical and computational results. Research activities include: (1) modeling of air flow in a confined space; (2) review of several different gas-liquid contactors utilizing centrifugal force: (3) review of carbon dioxide reduction contactors in space vehicles and other enclosed structures: (4) application of modern optimal control theory to environmental control of confined spaces; (5) optimal control of class of nonlinear diffusional distributed parameter systems: (6) optimization of system reliability of life support systems and sub-systems: (7) modeling, simulation and optimal control of the human thermal system: and (8) analysis and optimization of the water-vapor eletrolysis cell.

  4. System availability management technique for reliability and maintainability analysis

    NASA Technical Reports Server (NTRS)

    Davenport, G. K.

    1970-01-01

    Method for total system availability analysis is based on numerical prediction of the reliability, maintainability, and availability of each function system. It incorporates these functional-system estimates into an overall mathematical model.

  5. Reliable data acquisition for inspection systems

    NASA Astrophysics Data System (ADS)

    Silva, V. P.; Silva, D. S.; Boccardo, D. R.; Machado, R. C. S.; Carmo, L. F. R. C.

    2015-01-01

    In Brazil, the road transportation of dangerous goods is subject to regulatory control, which is conducted by Inmetro, the National Institute of Metrology, Quality and Technology. Currently, the process of monitoring such inspections is done manually, leaving the possibility of some inconsistencies: inspections held outside the authorized local inspection, incorrectly, incompletely, or even be held. Thus, in order to increase the reliability of such inspections, it is needed a closer monitoring by the regulatory agency. One approach towards that, is the implementation of an automated process in which evidences are collected in a reliable way during the inspections, enabling further analyses. This work employs security mechanisms on a portable device to ensure the confidence of the evidences collected during an inspection, paving the way for later more robust analyzes.

  6. Identification of components to optimize improvement in system reliability

    SciTech Connect

    Painton, L.; Campbell, J.

    1993-10-01

    The fields of reliability analysis and risk assessment have grown dramatically since the 1970s. There are now bodies of literature and standard practices which cover quantitative aspects of system analysis such as failure rate and repair models, fault and event tree generation, minimal cut sets, classical and Bayesian analysis of reliability, component and system testing techniques, decomposition methods, etc. In spite of the growth in the sophistication of reliability models, however, little has been done to integrate optimization models within a reliability analysis framework. That is, often reliability models focus on characterization of system structure in terms of topology and failure/availability characteristics of components. A number of approaches have been proposed to help identify the components of a system that have the largest influence on overall system reliability. While this may help rank order the components, it does not necessarily help a system design team identify which components they should improve to optimize overall reliability (it may be cheaper and more effective to focus on improving two or three components of smaller importance than one component of larger importance). In this paper, we present an optimization model that identifies the components to be improved to maximize the increase in system MTBF, subject to a fixed budget constraint. A dual formulation of the model is to minimize cost, subject to achieving a certain level of system reliability.

  7. Reliability analysis and optimization in the design of distributed systems

    SciTech Connect

    Hariri, S.

    1986-01-01

    Reliability measures and efficient evaluation algorithms are presented to aid in designing reliable distributed systems. The terminal reliability between a pair of computers is a good measure in computer networks. For distributed systems, to capture more effectively the redundancy in resources, such as programs and files, two new reliability measures are introduced. These measures are Distributed Program Reliability (DPR) and Distributed System Reliability (DSR). A simple and efficient algorithm, SYREL, is developed to evaluate the reliability between two computing centers. This algorithm incorporates conditional probability, set theory, and Boolean algebra in a distinct approach to achieve fast execution times and obtain compact expressions. An elegant and unified approach based on graph-theoretic techniques is used in developing algorithms to evaluate DPR and DSR measures. It performs a breadth-first search on the graph representing a given distributed system to enumerate all the subgraphs that guarantee the proper accessibility for executing the given tasks(s). These subgraphs are then used to evaluate the desired reliabilities. Several optimization algorithms are developed for designing reliable systems under a cost constraint.

  8. Evaluation of reliability modeling tools for advanced fault tolerant systems

    NASA Technical Reports Server (NTRS)

    Baker, Robert; Scheper, Charlotte

    1986-01-01

    The Computer Aided Reliability Estimation (CARE III) and Automated Reliability Interactice Estimation System (ARIES 82) reliability tools for application to advanced fault tolerance aerospace systems were evaluated. To determine reliability modeling requirements, the evaluation focused on the Draper Laboratories' Advanced Information Processing System (AIPS) architecture as an example architecture for fault tolerance aerospace systems. Advantages and limitations were identified for each reliability evaluation tool. The CARE III program was designed primarily for analyzing ultrareliable flight control systems. The ARIES 82 program's primary use was to support university research and teaching. Both CARE III and ARIES 82 were not suited for determining the reliability of complex nodal networks of the type used to interconnect processing sites in the AIPS architecture. It was concluded that ARIES was not suitable for modeling advanced fault tolerant systems. It was further concluded that subject to some limitations (the difficulty in modeling systems with unpowered spare modules, systems where equipment maintenance must be considered, systems where failure depends on the sequence in which faults occurred, and systems where multiple faults greater than a double near coincident faults must be considered), CARE III is best suited for evaluating the reliability of advanced tolerant systems for air transport.

  9. Systems reliability analysis for the national ignition facility

    SciTech Connect

    Majumdar, K.C.; Annese, C.E.; MacIntyre, A.T.; Sicherman, A.

    1996-06-12

    A Reliability, Availability and Maintainability (RAM) analysis was initiated for the National Ignition Facility (NIF). The NIF is an inertial confinement fusion research facility designed to achieve controlled thermonuclear reaction; the preferred site for the NIF is the Lawrence Livermore National Laboratory (LLNL). The NIF RAM analysis has three purposes: (1) to allocate top level reliability and availability goals for the systems, (2) to develop an operability model for optimum maintainability, and (3) to determine the achievability of the allocated goals of the RAM parameters for the NIF systems and the facility operation as a whole. An allocation model assigns the reliability and availability goals for front line and support systems by a top-down approach; reliability analysis uses a bottom-up approach to determine the system reliability and availability from component level to system level.

  10. Reliability studies of Integrated Modular Engine system designs

    NASA Technical Reports Server (NTRS)

    Hardy, Terry L.; Rapp, Douglas C.

    1993-01-01

    A study was performed to evaluate the reliability of Integrated Modular Engine (IME) concepts. Comparisons were made between networked IME systems and non-networked discrete systems using expander cycle configurations. Both redundant and non-redundant systems were analyzed. Binomial approximation and Markov analysis techniques were employed to evaluate total system reliability. In addition, Failure Modes and Effects Analyses (FMEA), Preliminary Hazard Analyses (PHA), and Fault Tree Analysis (FTA) were performed to allow detailed evaluation of the IME concept. A discussion of these system reliability concepts is also presented.

  11. Reliability studies of integrated modular engine system designs

    NASA Technical Reports Server (NTRS)

    Hardy, Terry L.; Rapp, Douglas C.

    1993-01-01

    A study was performed to evaluate the reliability of Integrated Modular Engine (IME) concepts. Comparisons were made between networked IME systems and non-networked discrete systems using expander cycle configurations. Both redundant and non-redundant systems were analyzed. Binomial approximation and Markov analysis techniques were employed to evaluate total system reliability. In addition, Failure Modes and Effects Analyses (FMEA), Preliminary Hazard Analyses (PHA), and Fault Tree Analysis (FTA) were performed to allow detailed evaluation of the IME concept. A discussion of these system reliability concepts is also presented.

  12. Reliability studies of Integrated Modular Engine system designs

    NASA Astrophysics Data System (ADS)

    Hardy, Terry L.; Rapp, Douglas C.

    1993-06-01

    A study was performed to evaluate the reliability of Integrated Modular Engine (IME) concepts. Comparisons were made between networked IME systems and non-networked discrete systems using expander cycle configurations. Both redundant and non-redundant systems were analyzed. Binomial approximation and Markov analysis techniques were employed to evaluate total system reliability. In addition, Failure Modes and Effects Analyses (FMEA), Preliminary Hazard Analyses (PHA), and Fault Tree Analysis (FTA) were performed to allow detailed evaluation of the IME concept. A discussion of these system reliability concepts is also presented.

  13. Reliability studies of integrated modular engine system designs

    NASA Astrophysics Data System (ADS)

    Hardy, Terry L.; Rapp, Douglas C.

    1993-06-01

    A study was performed to evaluate the reliability of Integrated Modular Engine (IME) concepts. Comparisons were made between networked IME systems and non-networked discrete systems using expander cycle configurations. Both redundant and non-redundant systems were analyzed. Binomial approximation and Markov analysis techniques were employed to evaluate total system reliability. In addition, Failure Modes and Effects Analyses (FMEA), Preliminary Hazard Analyses (PHA), and Fault Tree Analysis (FTA) were performed to allow detailed evaluation of the IME concept. A discussion of these system reliability concepts is also presented.

  14. BWR feedwater nozzle and control-rod-drive return line nozzle cracking

    SciTech Connect

    Not Available

    1981-11-01

    In its 1978 Annual Report to Congress, the Nuclear Regulatory Commission identified as an unresolved safety issue the appearance of cracks in feedwater nozzles at boiling-water reactors (BWRs). Later similar cracking, detected in return water lines for control-rod-drive systems at BWRs, was designated Part II of the issue. This article outlines the resolution of these cracking problems.

  15. Reliability of degrading dynamic systems subject to dynamic random loads

    NASA Technical Reports Server (NTRS)

    Grigoriu, Mircea

    1990-01-01

    Reliability was determined for two degrading dynamic systems subject to random load processes. Damage is caused by loss of components for Daniels systems and crack extension for plates with cracks. The analysis accounted for the coupling between response and current damage state of the system. It is based on mean crossing rates of conditional processes and properties of diffusion models. Simple systems are used to illustrate proposed methods for estimating reliability.

  16. Reliability analysis and initial requirements for FC systems and stacks

    NASA Astrophysics Data System (ADS)

    Åström, K.; Fontell, E.; Virtanen, S.

    In the year 2000 Wärtsilä Corporation started an R&D program to develop SOFC systems for CHP applications. The program aims to bring to the market highly efficient, clean and cost competitive fuel cell systems with rated power output in the range of 50-250 kW for distributed generation and marine applications. In the program Wärtsilä focuses on system integration and development. System reliability and availability are key issues determining the competitiveness of the SOFC technology. In Wärtsilä, methods have been implemented for analysing the system in respect to reliability and safety as well as for defining reliability requirements for system components. A fault tree representation is used as the basis for reliability prediction analysis. A dynamic simulation technique has been developed to allow for non-static properties in the fault tree logic modelling. Special emphasis has been placed on reliability analysis of the fuel cell stacks in the system. A method for assessing reliability and critical failure predictability requirements for fuel cell stacks in a system consisting of several stacks has been developed. The method is based on a qualitative model of the stack configuration where each stack can be in a functional, partially failed or critically failed state, each of the states having different failure rates and effects on the system behaviour. The main purpose of the method is to understand the effect of stack reliability, critical failure predictability and operating strategy on the system reliability and availability. An example configuration, consisting of 5 × 5 stacks (series of 5 sets of 5 parallel stacks) is analysed in respect to stack reliability requirements as a function of predictability of critical failures and Weibull shape factor of failure rate distributions.

  17. Reliability modeling of fault-tolerant computer based systems

    NASA Technical Reports Server (NTRS)

    Bavuso, Salvatore J.

    1987-01-01

    Digital fault-tolerant computer-based systems have become commonplace in military and commercial avionics. These systems hold the promise of increased availability, reliability, and maintainability over conventional analog-based systems through the application of replicated digital computers arranged in fault-tolerant configurations. Three tightly coupled factors of paramount importance, ultimately determining the viability of these systems, are reliability, safety, and profitability. Reliability, the major driver affects virtually every aspect of design, packaging, and field operations, and eventually produces profit for commercial applications or increased national security. However, the utilization of digital computer systems makes the task of producing credible reliability assessment a formidable one for the reliability engineer. The root of the problem lies in the digital computer's unique adaptability to changing requirements, computational power, and ability to test itself efficiently. Addressed here are the nuances of modeling the reliability of systems with large state sizes, in the Markov sense, which result from systems based on replicated redundant hardware and to discuss the modeling of factors which can reduce reliability without concomitant depletion of hardware. Advanced fault-handling models are described and methods of acquiring and measuring parameters for these models are delineated.

  18. Evolving Reliability and Maintainability Allocations for NASA Ground Systems

    NASA Technical Reports Server (NTRS)

    Munoz, Gisela; Toon, T.; Toon, J.; Conner, A.; Adams, T.; Miranda, D.

    2016-01-01

    This paper describes the methodology and value of modifying allocations to reliability and maintainability requirements for the NASA Ground Systems Development and Operations (GSDO) programs subsystems. As systems progressed through their design life cycle and hardware data became available, it became necessary to reexamine the previously derived allocations. This iterative process provided an opportunity for the reliability engineering team to reevaluate allocations as systems moved beyond their conceptual and preliminary design phases. These new allocations are based on updated designs and maintainability characteristics of the components. It was found that trade-offs in reliability and maintainability were essential to ensuring the integrity of the reliability and maintainability analysis. This paper discusses the results of reliability and maintainability reallocations made for the GSDO subsystems as the program nears the end of its design phase.

  19. Evolving Reliability and Maintainability Allocations for NASA Ground Systems

    NASA Technical Reports Server (NTRS)

    Munoz, Gisela; Toon, Troy; Toon, Jamie; Conner, Angelo C.; Adams, Timothy C.; Miranda, David J.

    2016-01-01

    This paper describes the methodology and value of modifying allocations to reliability and maintainability requirements for the NASA Ground Systems Development and Operations (GSDO) program’s subsystems. As systems progressed through their design life cycle and hardware data became available, it became necessary to reexamine the previously derived allocations. This iterative process provided an opportunity for the reliability engineering team to reevaluate allocations as systems moved beyond their conceptual and preliminary design phases. These new allocations are based on updated designs and maintainability characteristics of the components. It was found that trade-offs in reliability and maintainability were essential to ensuring the integrity of the reliability and maintainability analysis. This paper discusses the results of reliability and maintainability reallocations made for the GSDO subsystems as the program nears the end of its design phase.

  20. Evolving Reliability and Maintainability Allocations for NASA Ground Systems

    NASA Technical Reports Server (NTRS)

    Munoz, Gisela; Toon, Jamie; Toon, Troy; Adams, Timothy C.; Miranda, David J.

    2016-01-01

    This paper describes the methodology that was developed to allocate reliability and maintainability requirements for the NASA Ground Systems Development and Operations (GSDO) program's subsystems. As systems progressed through their design life cycle and hardware data became available, it became necessary to reexamine the previously derived allocations. Allocating is an iterative process; as systems moved beyond their conceptual and preliminary design phases this provided an opportunity for the reliability engineering team to reevaluate allocations based on updated designs and maintainability characteristics of the components. Trade-offs in reliability and maintainability were essential to ensuring the integrity of the reliability and maintainability analysis. This paper will discuss the value of modifying reliability and maintainability allocations made for the GSDO subsystems as the program nears the end of its design phase.

  1. Application of reliability concepts to the Nepal power system

    SciTech Connect

    Billinton, R.; Pandey, M.; Aboreshaid, S.; Fotuhi-Firuzabad, M.

    1995-12-31

    In many of the less industrialized countries throughout the world, reliability is incorporated in power system planning and operation using traditional deterministic techniques. This is the case with the Nepal Power System (NPS), where developed expansion plans have been based on non-probabilistic criteria. This paper illustrates the application of probabilistic methods to reliability evaluation of the NPS. Evaluations at both the generation and composite generation and transmission system levels have been performed. The overall system and nine major load centers have been assessed. These load points carry in total more than 54% of the system load. An assessment of an expansion plan proposed by the Nepal Electricity Authority (NEA) has been performed. The results indicate the reliability implications associated with the system and the proposed expansion plan, and show that quantitative reliability evaluation of the NPS is both possible and practical.

  2. Subsea pipeline isolation systems: Reliability and costs

    SciTech Connect

    Masheder, R.R.

    1995-12-31

    On the night of 6/7 July 1988 a major oil production platform known as Piper Alpha in the UK sector of the North Sea was destroyed by explosion and fire, with the loss of 167 lives. This led to the appointment of Lord Cullen, a senior Scottish Judge, to hold a Public Inquiry into the Piper Alpha Disaster. The Cullen Enquiry Report consisting of 23 chapters set out in 2 volumes, was published on 12 November 1990. One of the important conclusions drawn by Lord Cullen resulted in a recommendation for studies to be conducted to consider ways of improving the reliability and reducing the costs of SSIVs (Subsea Isolation Valves) so that it is more often reasonably practicable to install them. To address the Cullen recommendations, a joint industry study was conducted by UKOOA (United Kingdom Offshore Operators Association) and the HSE/OSD (Health and Safety Executive Offshore Safety Division) in conjunction with independent consultants. The results of the studies and the conclusions drawn by UKOOA Pipeline Valve Group and the HSE Offshore Safety Division are presented in this paper.

  3. A System for Integrated Reliability and Safety Analyses

    NASA Technical Reports Server (NTRS)

    Kostiuk, Peter; Shapiro, Gerald; Hanson, Dave; Kolitz, Stephan; Leong, Frank; Rosch, Gene; Coumeri, Marc; Scheidler, Peter, Jr.; Bonesteel, Charles

    1999-01-01

    We present an integrated reliability and aviation safety analysis tool. The reliability models for selected infrastructure components of the air traffic control system are described. The results of this model are used to evaluate the likelihood of seeing outcomes predicted by simulations with failures injected. We discuss the design of the simulation model, and the user interface to the integrated toolset.

  4. 75 FR 35689 - System Personnel Training Reliability Standards

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-23

    ... Reliability Standards for the Bulk-Power System, Order No. 693, Federal Register 72 FR 16,416 (Apr. 4, 2007... Corporation, the Electric Reliability Organization (ERO) certified by the Commission. In addition, pursuant to... develop rules for operating staff to follow.\\8\\ In addition, the Task Force urged NERC to...

  5. 75 FR 72664 - System Personnel Training Reliability Standards

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-26

    ...\\ Mandatory Reliability Standards for the Bulk-Power System, Order No. 693, 72 FR 16416 (Apr. 4, 2007), FERC... operations each year using realistic simulations.\\5\\ \\4\\ Id. P 1331. \\5\\ Reliability Standard PER-002-0. 4... further identifies those entities required to use simulation technology such as a simulator,...

  6. A highly reliable RAID system based on GPUs.

    SciTech Connect

    Curry, Matthew L.

    2010-06-01

    While RAID is the prevailing method of creating reliable secondary storage infrastructure, many users desire more flexibility than offered by current implementations. To attain needed performance, customers have often sought after hardware-based RAID solutions. This talk describes a RAID system that offloads erasure correction coding calculations to GPUs, allowing increased reliability by supporting new RAID levels while maintaining high performance.

  7. Techniques for increasing the reliability of accelerator control system electronics

    SciTech Connect

    Utterback, J.

    1993-09-01

    As the physical size of modern accelerators becomes larger and larger, the number of required control system circuit boards increases, and the probability of one of those circuit boards failing while in service also increases. In order to do physics, the experimenters need the accelerator to provide beam reliably with as little down time as possible. With the advent of colliding beams physics, reliability becomes even more important due to the fact that a control system failure can cause the loss of painstakingly produced antiprotons. These facts prove the importance of keeping reliability in mind when designing and maintaining accelerator control system electronics.

  8. A high reliability battery management system

    NASA Technical Reports Server (NTRS)

    Moody, M. H.

    1986-01-01

    Over a period of some 5 years Canadian Astronautics Limited (CAL) has developed a system to autonomously manage, and thus prolong the life of, secondary storage batteries. During the development, the system was aimed at the space vehicle application using nickel cadmium batteries, but is expected to be able to enhance the life and performance of any rechargeable electrochemical couple. The system handles the cells of a battery individually and thus avoids the problems of over, and under, drive that inevitably occur in a battery of cells managed by an averaging system. This individual handling also allow cells to be totally bypassed in the event of failure, thus avoiding the losses associated with low capacity, partial short circuit, and the catastrophe of open circuit. The system has an optional capability of managing redundant batteries simultaneously, adding the advantage of on line reconditioning of one battery, while the other maintains the energy storage capability of the overall system. As developed, the system contains a dedicated, redundant, microprocessor, but the capability exists to have this computing capability time shared, or remote, and operating through a data link. As adjuncts to the basic management system CAL has developed high efficiency, polyphase, power regulators for charge and discharge power conditioning.

  9. Reliability model of a monopropellant auxiliary propulsion system

    NASA Technical Reports Server (NTRS)

    Greenberg, J. S.

    1971-01-01

    A mathematical model and associated computer code has been developed which computes the reliability of a monopropellant blowdown hydrazine spacecraft auxiliary propulsion system as a function of time. The propulsion system is used to adjust or modify the spacecraft orbit over an extended period of time. The multiple orbit corrections are the multiple objectives which the auxiliary propulsion system is designed to achieve. Thus the reliability model computes the probability of successfully accomplishing each of the desired orbit corrections. To accomplish this, the reliability model interfaces with a computer code that models the performance of a blowdown (unregulated) monopropellant auxiliary propulsion system. The computer code acts as a performance model and as such gives an accurate time history of the system operating parameters. The basic timing and status information is passed on to and utilized by the reliability model which establishes the probability of successfully accomplishing the orbit corrections.

  10. Reliable Fiber Sensor System with Star-Ring-Bus Architecture

    PubMed Central

    Peng, Peng-Chun; Wang, Jun-Bo; Huang, Kuan-Yan

    2010-01-01

    This work presents a novel star-ring-bus sensor system and demonstrates its effectiveness. The main trunk of the proposed sensor system is a star topology and the sensing branches comprise a series of bus subnets. Any weakness in the reliability of the sensor system is overcome by adding remote nodes and switches to the ring and bus subnets. To construct the proposed star-ring-bus sensor system, a fiber ring laser scheme is used to improve the signal-to-noise ratio of the sensor system. The proposed system increases the reliability and capacity of fiber sensor systems. PMID:22399876

  11. Diverse Redundant Systems for Reliable Space Life Support

    NASA Technical Reports Server (NTRS)

    Jones, Harry W.

    2015-01-01

    Reliable life support systems are required for deep space missions. The probability of a fatal life support failure should be less than one in a thousand in a multi-year mission. It is far too expensive to develop a single system with such high reliability. Using three redundant units would require only that each have a failure probability of one in ten over the mission. Since the system development cost is inverse to the failure probability, this would cut cost by a factor of one hundred. Using replaceable subsystems instead of full systems would further cut cost. Using full sets of replaceable components improves reliability more than using complete systems as spares, since a set of components could repair many different failures instead of just one. Replaceable components would require more tools, space, and planning than full systems or replaceable subsystems. However, identical system redundancy cannot be relied on in practice. Common cause failures can disable all the identical redundant systems. Typical levels of common cause failures will defeat redundancy greater than two. Diverse redundant systems are required for reliable space life support. Three, four, or five diverse redundant systems could be needed for sufficient reliability. One system with lower level repair could be substituted for two diverse systems to save cost.

  12. Reliability models for dataflow computer systems

    NASA Technical Reports Server (NTRS)

    Kavi, K. M.; Buckles, B. P.

    1985-01-01

    The demands for concurrent operation within a computer system and the representation of parallelism in programming languages have yielded a new form of program representation known as data flow (DENN 74, DENN 75, TREL 82a). A new model based on data flow principles for parallel computations and parallel computer systems is presented. Necessary conditions for liveness and deadlock freeness in data flow graphs are derived. The data flow graph is used as a model to represent asynchronous concurrent computer architectures including data flow computers.

  13. Allocating SMART Reliability and Maintainability Goals to NASA Ground Systems

    NASA Technical Reports Server (NTRS)

    Gillespie, Amanda; Monaghan, Mark

    2013-01-01

    This paper will describe the methodology used to allocate Reliability and Maintainability (R&M) goals to Ground Systems Development and Operations (GSDO) subsystems currently being designed or upgraded.

  14. Software reliability and safety in nuclear reactor protection systems

    SciTech Connect

    Lawrence, J.D.

    1993-11-01

    Planning the development, use and regulation of computer systems in nuclear reactor protection systems in such a way as to enhance reliability and safety is a complex issue. This report is one of a series of reports from the Computer Safety and Reliability Group, Lawrence Livermore that investigates different aspects of computer software in reactor National Laboratory, that investigates different aspects of computer software in reactor protection systems. There are two central themes in the report, First, software considerations cannot be fully understood in isolation from computer hardware and application considerations. Second, the process of engineering reliability and safety into a computer system requires activities to be carried out throughout the software life cycle. The report discusses the many activities that can be carried out during the software life cycle to improve the safety and reliability of the resulting product. The viewpoint is primarily that of the assessor, or auditor.

  15. 49 CFR 230.57 - Injectors and feedwater pumps.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Appurtenances Injectors, Feedwater Pumps, and Flue Plugs § 230.57 Injectors and feedwater pumps. (a) Water... water to the boiler, at least one of which is a live steam injector. (b) Maintenance and testing... delivering water to the boiler. Boiler checks, delivery pipes, feed water pipes, tank hose and tank...

  16. 49 CFR 230.57 - Injectors and feedwater pumps.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Appurtenances Injectors, Feedwater Pumps, and Flue Plugs § 230.57 Injectors and feedwater pumps. (a) Water... water to the boiler, at least one of which is a live steam injector. (b) Maintenance and testing... delivering water to the boiler. Boiler checks, delivery pipes, feed water pipes, tank hose and tank...

  17. 49 CFR 230.57 - Injectors and feedwater pumps.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Appurtenances Injectors, Feedwater Pumps, and Flue Plugs § 230.57 Injectors and feedwater pumps. (a) Water... water to the boiler, at least one of which is a live steam injector. (b) Maintenance and testing... delivering water to the boiler. Boiler checks, delivery pipes, feed water pipes, tank hose and tank...

  18. 49 CFR 230.57 - Injectors and feedwater pumps.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Appurtenances Injectors, Feedwater Pumps, and Flue Plugs § 230.57 Injectors and feedwater pumps. (a) Water... water to the boiler, at least one of which is a live steam injector. (b) Maintenance and testing... delivering water to the boiler. Boiler checks, delivery pipes, feed water pipes, tank hose and tank...

  19. 49 CFR 230.57 - Injectors and feedwater pumps.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 4 2013-10-01 2013-10-01 false Injectors and feedwater pumps. 230.57 Section 230.57 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION STEAM LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS Boilers and Appurtenances Injectors, Feedwater Pumps,...

  20. Synthetical Reliability Analysis Model of CNC Software System

    NASA Astrophysics Data System (ADS)

    Xu, Yue; Xia, Yinjie; Wan, Yi

    CNC technology is the core of advanced manufacturing technology, and CNC software system is the very important part of numerical control system. The entire CNC system will not work normally, once the potential failure makes the software invalid. As to the current study of CNC sysytem, in use of the FAULT glitch tree, established a glitch tree for the CNC system; find the minimum cut sets with Fussed method and then according to the probability of several common glitches, make quantitative analysis in the reliability of the CNC system so that scientific ways can be provided for the reliability design, maintenance and management of the CNC system.

  1. The ATS F&G systems reliability program.

    NASA Technical Reports Server (NTRS)

    Doyle, H.

    1972-01-01

    Assurance of reliability, quality, and proper testing requires a large coordinating effort and a means for connecting the various areas involved. All parts used on the spacecraft are required to meet strict specifications and consequently must be approved by the systems reliability manager. The parts program has access to a computer data bank into which all information concerning nonstandard parts approval requests has been stored. Through the data bank, the system collects and distributes timely information concerning quality and reliability to all departments that may be concerned.

  2. Reliability Modeling of Microelectromechanical Systems Using Neural Networks

    NASA Technical Reports Server (NTRS)

    Perera. J. Sebastian

    2000-01-01

    Microelectromechanical systems (MEMS) are a broad and rapidly expanding field that is currently receiving a great deal of attention because of the potential to significantly improve the ability to sense, analyze, and control a variety of processes, such as heating and ventilation systems, automobiles, medicine, aeronautical flight, military surveillance, weather forecasting, and space exploration. MEMS are very small and are a blend of electrical and mechanical components, with electrical and mechanical systems on one chip. This research establishes reliability estimation and prediction for MEMS devices at the conceptual design phase using neural networks. At the conceptual design phase, before devices are built and tested, traditional methods of quantifying reliability are inadequate because the device is not in existence and cannot be tested to establish the reliability distributions. A novel approach using neural networks is created to predict the overall reliability of a MEMS device based on its components and each component's attributes. The methodology begins with collecting attribute data (fabrication process, physical specifications, operating environment, property characteristics, packaging, etc.) and reliability data for many types of microengines. The data are partitioned into training data (the majority) and validation data (the remainder). A neural network is applied to the training data (both attribute and reliability); the attributes become the system inputs and reliability data (cycles to failure), the system output. After the neural network is trained with sufficient data. the validation data are used to verify the neural networks provided accurate reliability estimates. Now, the reliability of a new proposed MEMS device can be estimated by using the appropriate trained neural networks developed in this work.

  3. Integrated performance and reliability specification for digital avionics systems

    NASA Technical Reports Server (NTRS)

    Brehm, Eric W.; Goettge, Robert T.

    1995-01-01

    This paper describes an automated tool for performance and reliability assessment of digital avionics systems, called the Automated Design Tool Set (ADTS). ADTS is based on an integrated approach to design assessment that unifies traditional performance and reliability views of system designs, and that addresses interdependencies between performance and reliability behavior via exchange of parameters and result between mathematical models of each type. A multi-layer tool set architecture has been developed for ADTS that separates the concerns of system specification, model generation, and model solution. Performance and reliability models are generated automatically as a function of candidate system designs, and model results are expressed within the system specification. The layered approach helps deal with the inherent complexity of the design assessment process, and preserves long-term flexibility to accommodate a wide range of models and solution techniques within the tool set structure. ADTS research and development to date has focused on development of a language for specification of system designs as a basis for performance and reliability evaluation. A model generation and solution framework has also been developed for ADTS, that will ultimately encompass an integrated set of analytic and simulated based techniques for performance, reliability, and combined design assessment.

  4. Final Report for the Virtual Reliability Realization System LDRD

    SciTech Connect

    DELLIN, THEODORE A.; HENDERSON, CHRISTOPHER L.; O'TOOLE, EDWARD J.

    2000-12-01

    Current approaches to reliability are not adequate to keep pace with the need for faster, better and cheaper products and systems. This is especially true in high consequence of failure applications. The original proposal for the LDRD was to look at this challenge and see if there was a new paradigm that could make reliability predictions, along with a quantitative estimate of the risk in that prediction, in a way that was faster, better and cheaper. Such an approach would be based on the underlying science models that are the backbone of reliability predictions. The new paradigm would be implemented in two software tools: the Virtual Reliability Realization System (VRRS) and the Reliability Expert System (REX). The three-year LDRD was funded at a reduced level for the first year ($120K vs. $250K) and not renewed. Because of the reduced funding, we concentrated on the initial development of the expertise system. We developed an interactive semiconductor calculation tool needed for reliability analyses. We also were able to generate a basic functional system using Microsoft Siteserver Commerce Edition and Microsoft Sequel Server. The base system has the capability to store Office documents from multiple authors, and has the ability to track and charge for usage. The full outline of the knowledge model has been incorporated as well as examples of various types of content.

  5. Assuring long-term reliability of concentrator PV systems

    NASA Astrophysics Data System (ADS)

    McConnell, R.; Garboushian, V.; Brown, J.; Crawford, C.; Darban, K.; Dutra, D.; Geer, S.; Ghassemian, V.; Gordon, R.; Kinsey, G.; Stone, K.; Turner, G.

    2009-08-01

    Concentrator PV (CPV) systems have attracted significant interest because these systems incorporate the world's highest efficiency solar cells and they are targeting the lowest cost production of solar electricity for the world's utility markets. Because these systems are just entering solar markets, manufacturers and customers need to assure their reliability for many years of operation. There are three general approaches for assuring CPV reliability: 1) field testing and development over many years leading to improved product designs, 2) testing to internationally accepted qualification standards (especially for new products) and 3) extended reliability tests to identify critical weaknesses in a new component or design. Amonix has been a pioneer in all three of these approaches. Amonix has an internal library of field failure data spanning over 15 years that serves as the basis for its seven generations of CPV systems. An Amonix product served as the test CPV module for the development of the world's first qualification standard completed in March 2001. Amonix staff has served on international standards development committees, such as the International Electrotechnical Commission (IEC), in support of developing CPV standards needed in today's rapidly expanding solar markets. Recently Amonix employed extended reliability test procedures to assure reliability of multijunction solar cell operation in its seventh generation high concentration PV system. This paper will discuss how these three approaches have all contributed to assuring reliability of the Amonix systems.

  6. Distribution System Reliability Analysis for Smart Grid Applications

    NASA Astrophysics Data System (ADS)

    Aljohani, Tawfiq Masad

    Reliability of power systems is a key aspect in modern power system planning, design, and operation. The ascendance of the smart grid concept has provided high hopes of developing an intelligent network that is capable of being a self-healing grid, offering the ability to overcome the interruption problems that face the utility and cost it tens of millions in repair and loss. To address its reliability concerns, the power utilities and interested parties have spent extensive amount of time and effort to analyze and study the reliability of the generation and transmission sectors of the power grid. Only recently has attention shifted to be focused on improving the reliability of the distribution network, the connection joint between the power providers and the consumers where most of the electricity problems occur. In this work, we will examine the effect of the smart grid applications in improving the reliability of the power distribution networks. The test system used in conducting this thesis is the IEEE 34 node test feeder, released in 2003 by the Distribution System Analysis Subcommittee of the IEEE Power Engineering Society. The objective is to analyze the feeder for the optimal placement of the automatic switching devices and quantify their proper installation based on the performance of the distribution system. The measures will be the changes in the reliability system indices including SAIDI, SAIFI, and EUE. The goal is to design and simulate the effect of the installation of the Distributed Generators (DGs) on the utility's distribution system and measure the potential improvement of its reliability. The software used in this work is DISREL, which is intelligent power distribution software that is developed by General Reliability Co.

  7. System reliability, performance and trust in adaptable automation.

    PubMed

    Chavaillaz, Alain; Wastell, David; Sauer, Jürgen

    2016-01-01

    The present study examined the effects of reduced system reliability on operator performance and automation management in an adaptable automation environment. 39 operators were randomly assigned to one of three experimental groups: low (60%), medium (80%), and high (100%) reliability of automation support. The support system provided five incremental levels of automation which operators could freely select according to their needs. After 3 h of training on a simulated process control task (AutoCAMS) in which the automation worked infallibly, operator performance and automation management were measured during a 2.5-h testing session. Trust and workload were also assessed through questionnaires. Results showed that although reduced system reliability resulted in lower levels of trust towards automation, there were no corresponding differences in the operators' reliance on automation. While operators showed overall a noteworthy ability to cope with automation failure, there were, however, decrements in diagnostic speed and prospective memory with lower reliability. PMID:26360226

  8. Reliability analysis framework for computer-assisted medical decision systems

    SciTech Connect

    Habas, Piotr A.; Zurada, Jacek M.; Elmaghraby, Adel S.; Tourassi, Georgia D.

    2007-02-15

    We present a technique that enhances computer-assisted decision (CAD) systems with the ability to assess the reliability of each individual decision they make. Reliability assessment is achieved by measuring the accuracy of a CAD system with known cases similar to the one in question. The proposed technique analyzes the feature space neighborhood of the query case to dynamically select an input-dependent set of known cases relevant to the query. This set is used to assess the local (query-specific) accuracy of the CAD system. The estimated local accuracy is utilized as a reliability measure of the CAD response to the query case. The underlying hypothesis of the study is that CAD decisions with higher reliability are more accurate. The above hypothesis was tested using a mammographic database of 1337 regions of interest (ROIs) with biopsy-proven ground truth (681 with masses, 656 with normal parenchyma). Three types of decision models, (i) a back-propagation neural network (BPNN), (ii) a generalized regression neural network (GRNN), and (iii) a support vector machine (SVM), were developed to detect masses based on eight morphological features automatically extracted from each ROI. The performance of all decision models was evaluated using the Receiver Operating Characteristic (ROC) analysis. The study showed that the proposed reliability measure is a strong predictor of the CAD system's case-specific accuracy. Specifically, the ROC area index for CAD predictions with high reliability was significantly better than for those with low reliability values. This result was consistent across all decision models investigated in the study. The proposed case-specific reliability analysis technique could be used to alert the CAD user when an opinion that is unlikely to be reliable is offered. The technique can be easily deployed in the clinical environment because it is applicable with a wide range of classifiers regardless of their structure and it requires neither additional

  9. Reliability Performance Optimization of Meshed Electrical Distribution System Considering Customer and Energy based Reliability Indices

    NASA Astrophysics Data System (ADS)

    Arya, L. D.; Kela, K. B.

    2013-12-01

    This paper describes a methodology for determination of optimum failure rate and repair time for each component of a meshed distribution system. In this paper the reliability indices for a sample meshed network are optimized. An objective function incorporating customer and energy based reliability indices and their target values is formulated. These indices are function of failure rate and repair time of a section of a distribution network. Modification of failure rate and repair time modifies the cost attached to them. Hence the optimization of the objective function is achieved by modifying the failure rate and repair time of each section of the meshed distribution system accounting constraint on budget allocated. The problem has been solved using population based differential evolution and bare bones particle swarm optimization techniques and results have been compared for a sample meshed distribution system.

  10. Software Reliability Issues Concerning Large and Safety Critical Software Systems

    NASA Technical Reports Server (NTRS)

    Kamel, Khaled; Brown, Barbara

    1996-01-01

    This research was undertaken to provide NASA with a survey of state-of-the-art techniques using in industrial and academia to provide safe, reliable, and maintainable software to drive large systems. Such systems must match the complexity and strict safety requirements of NASA's shuttle system. In particular, the Launch Processing System (LPS) is being considered for replacement. The LPS is responsible for monitoring and commanding the shuttle during test, repair, and launch phases. NASA built this system in the 1970's using mostly hardware techniques to provide for increased reliability, but it did so often using custom-built equipment, which has not been able to keep up with current technologies. This report surveys the major techniques used in industry and academia to ensure reliability in large and critical computer systems.

  11. UPT scenarios: Implications for system reliability

    NASA Astrophysics Data System (ADS)

    Walsh, Daniel W.

    1992-12-01

    The objective of this project was to examine the corrosion resistance of 316L stainless steel in several urine pre-treat solutions. Four solutions were examined: untreated urine (control); urine pretreated with oxone (potassium peroxymonosulfate sulfate); urine pretreated with sodium hypochlorite (NaOCl); and urine pretreated with ozone (O3). In accordance with current procedures, all solutions but the control were acidified to a pH of 2.5 using sulfuric acid--this suppresses the generation of ammonia in the solutions and is intended to limit microbial growth. Welded and unwelded coupons were exposed to each solution. In addition, Titanium coupons (welded and unwelded) were exposed to biologically active environmental control and life support system (ECLSS) water. Microbial attachment and biofilm growth were monitored. Ozone was examined as a biocide/oxidizer/corrosion preventative (simultaneous addition) and as a remediation method (added one week after exposure). In an unrelated effort, HP 9-4-30 coupons were exposed to biologically active solutions. Corrosion rates for welded and unwelded samples were determined--results were correlated to the ongoing HP 9-4-30 weldment stress corrosion study.

  12. UPT scenarios: Implications for system reliability

    NASA Technical Reports Server (NTRS)

    Walsh, Daniel W.

    1992-01-01

    The objective of this project was to examine the corrosion resistance of 316L stainless steel in several urine pre-treat solutions. Four solutions were examined: untreated urine (control); urine pretreated with oxone (potassium peroxymonosulfate sulfate); urine pretreated with sodium hypochlorite (NaOCl); and urine pretreated with ozone (O3). In accordance with current procedures, all solutions but the control were acidified to a pH of 2.5 using sulfuric acid--this suppresses the generation of ammonia in the solutions and is intended to limit microbial growth. Welded and unwelded coupons were exposed to each solution. In addition, Titanium coupons (welded and unwelded) were exposed to biologically active environmental control and life support system (ECLSS) water. Microbial attachment and biofilm growth were monitored. Ozone was examined as a biocide/oxidizer/corrosion preventative (simultaneous addition) and as a remediation method (added one week after exposure). In an unrelated effort, HP 9-4-30 coupons were exposed to biologically active solutions. Corrosion rates for welded and unwelded samples were determined--results were correlated to the ongoing HP 9-4-30 weldment stress corrosion study.

  13. Computer-aided reliability estimation. [for fault-tolerant systems

    NASA Technical Reports Server (NTRS)

    Stiffler, J. J.

    1977-01-01

    Computer-aided reliability estimation (CARE) programs are developed to improve the tools available for estimating the reliability of fault-tolerant systems. A description is presented of a program, called CARE II, which was developed after the first program reported by Mathur (1971). Attention is given to the CARE II reliability model, the CARE II coverage model, and CARE II limitations which are to be rectified in CARE III. It is pointed out that the present coverage model in CARE II is extremely versatile. The major limitation is related to the burden placed on the user to determine the basic parameters from which the coverage calculations are made.

  14. FFTF (Fast Flux Test Facility) reactor shutdown system reliability reevaluation

    SciTech Connect

    Pierce, B.F.

    1986-07-01

    The reliability analysis of the Fast Flux Test Facility reactor shutdown system was reevaluated. Failure information based on five years of plant operating experience was used to verify original reliability numbers or to establish new ones. Also, system modifications made subsequent to performance of the original analysis were incorporated into the reevaluation. Reliability calculations and sensitivity analyses were performed using a commercially available spreadsheet on a personal computer. The spreadsheet was configured so that future failures could be tracked and compared with expected failures. A number of recommendations resulted from the reevaluation including both increased and decreased surveillance intervals. All recommendations were based on meeting or exceeding existing reliability goals. Considerable cost savings will be incurred upon implementation of the recommendations.

  15. An Overview of the Reliability and Availability Data System (RADS)

    SciTech Connect

    T. E. Wierman; K. J. Kvarfordt; S. A. Eide; D. M. Rasmuson

    2005-09-01

    The Reliability and Availability Data System (RADS) is a database and analysis code, developed by the Idaho National Engineering and Environmental Laboratory (INEEL) for the U.S. Nuclear Regulatory Commission (USNRC). The code is designed to estimate industry and plant-specific reliability and availability parameters for selected components in risk-important systems and initiating events for use in risk-informed applications. The RADS tool contains data and information based on actual operating experience from U.S. commercial nuclear power plants. The data contained in RADS is kept up-to-date by loading the most current quarter's Equipment Performance and Information Exchange (EPIX) data and by yearly lods of initiating event data from licensee event reports (LERS). The reliability parameters estimated by RADS are (1) probability of failure on demand, (2) failure rate during operation (used to calculate failure to run probability) and (3) time trends in reliability parameters.

  16. Dynamic evidential reasoning algorithm for systems reliability prediction

    NASA Astrophysics Data System (ADS)

    Hu, Chang-Hua; Si, Xiao-Sheng; Yang, Jian-Bo

    2010-07-01

    In this article, dynamic evidential reasoning (DER) algorithm is applied to forecast reliability in turbochargers engine systems and a reliability prediction model is developed. The focus of this study is to examine the feasibility and validity of DER algorithm in systems reliability prediction by comparing it with some existing approaches. To build an effective DER forecasting model, the parameters of prediction model must be set carefully. To solve this problem, a generic nonlinear optimisation model is investigated to search for the optimal parameters of forecasting model, and then the optimal parameters are adopted to construct the DER forecasting model. Finally, a numerical example is provided to demonstrate the detailed implementation procedures and the validity of the proposed approach in the areas of reliability prediction.

  17. Survey of Software Assurance Techniques for Highly Reliable Systems

    NASA Technical Reports Server (NTRS)

    Nelson, Stacy

    2004-01-01

    This document provides a survey of software assurance techniques for highly reliable systems including a discussion of relevant safety standards for various industries in the United States and Europe, as well as examples of methods used during software development projects. It contains one section for each industry surveyed: Aerospace, Defense, Nuclear Power, Medical Devices and Transportation. Each section provides an overview of applicable standards and examples of a mission or software development project, software assurance techniques used and reliability achieved.

  18. The Challenges of Credible Thermal Protection System Reliability Quantification

    NASA Technical Reports Server (NTRS)

    Green, Lawrence L.

    2013-01-01

    The paper discusses several of the challenges associated with developing a credible reliability estimate for a human-rated crew capsule thermal protection system. The process of developing such a credible estimate is subject to the quantification, modeling and propagation of numerous uncertainties within a probabilistic analysis. The development of specific investment recommendations, to improve the reliability prediction, among various potential testing and programmatic options is then accomplished through Bayesian analysis.

  19. The art of fault-tolerant system reliability modeling

    NASA Technical Reports Server (NTRS)

    Butler, Ricky W.; Johnson, Sally C.

    1990-01-01

    A step-by-step tutorial of the methods and tools used for the reliability analysis of fault-tolerant systems is presented. Emphasis is on the representation of architectural features in mathematical models. Details of the mathematical solution of complex reliability models are not presented. Instead the use of several recently developed computer programs--SURE, ASSIST, STEM, PAWS--which automate the generation and solution of these models is described.

  20. Estimates Of The Orbiter RSI Thermal Protection System Thermal Reliability

    NASA Technical Reports Server (NTRS)

    Kolodziej, P.; Rasky, D. J.

    2002-01-01

    In support of the Space Shuttle Orbiter post-flight inspection, structure temperatures are recorded at selected positions on the windward, leeward, starboard and port surfaces. Statistical analysis of this flight data and a non-dimensional load interference (NDLI) method are used to estimate the thermal reliability at positions were reusable surface insulation (RSI) is installed. In this analysis, structure temperatures that exceed the design limit define the critical failure mode. At thirty-three positions the RSI thermal reliability is greater than 0.999999 for the missions studied. This is not the overall system level reliability of the thermal protection system installed on an Orbiter. The results from two Orbiters, OV-102 and OV-105, are in good agreement. The original RSI designs on the OV-102 Orbital Maneuvering System pods, which had low reliability, were significantly improved on OV-105. The NDLI method was also used to estimate thermal reliability from an assessment of TPS uncertainties that was completed shortly before the first Orbiter flight. Results fiom the flight data analysis and the pre-flight assessment agree at several positions near each other. The NDLI method is also effective for optimizing RSI designs to provide uniform thermal reliability on the acreage surface of reusable launch vehicles.

  1. Stationary Engineers Apprenticeship. Related Training Modules. 17.1-17.3 Feedwater.

    ERIC Educational Resources Information Center

    Lane Community Coll., Eugene, OR.

    This learning module, one in a series of 20 related training modules for apprentice stationary engineers, deals with feedwater. Addressed in the individual instructional packages included in the module are the following topics: types of feedwater, equipment for use in working with feedwater, water treatments, and procedures for testing feedwater.…

  2. Reliability assessment of solar domestic hot water systems

    NASA Astrophysics Data System (ADS)

    Wang, P. Y.; Wolosewicz, R. M.

    This paper presents reliability and mean-time-between-failure studies of six generic solar domestic hot water systems. Failure rate data for system components were obtained from product literature or from consumer product industries. Reliability block diagrams are employed for the analyses, and exponential distribution functions are assumed for individual components. Since some components do not operate continuously, a duty-cycle factor is developed and defined as the ratio of operating time to total mission time. To accommodate systems experiencing different duty cycles, an averaged duty cycle is introduced to estimate mean lives. Large variations in system reliability and mean life were found and result from wide failure-rate bands for some of the components.

  3. Reliability assessment for components of large scale photovoltaic systems

    NASA Astrophysics Data System (ADS)

    Ahadi, Amir; Ghadimi, Noradin; Mirabbasi, Davar

    2014-10-01

    Photovoltaic (PV) systems have significantly shifted from independent power generation systems to a large-scale grid-connected generation systems in recent years. The power output of PV systems is affected by the reliability of various components in the system. This study proposes an analytical approach to evaluate the reliability of large-scale, grid-connected PV systems. The fault tree method with an exponential probability distribution function is used to analyze the components of large-scale PV systems. The system is considered in the various sequential and parallel fault combinations in order to find all realistic ways in which the top or undesired events can occur. Additionally, it can identify areas that the planned maintenance should focus on. By monitoring the critical components of a PV system, it is possible not only to improve the reliability of the system, but also to optimize the maintenance costs. The latter is achieved by informing the operators about the system component's status. This approach can be used to ensure secure operation of the system by its flexibility in monitoring system applications. The implementation demonstrates that the proposed method is effective and efficient and can conveniently incorporate more system maintenance plans and diagnostic strategies.

  4. 78 FR 77574 - Protection System Maintenance Reliability Standard

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-24

    .... 824o (2012). \\2\\ Mandatory Reliability Standards for the Bulk Power System, Order No. 693, 72 FR 16,416... informational filing on the development of a guidance report concerning the commissioning of power system... reflect the known and reported condition or the historical performance of the relevant devices. 24....

  5. Long life high reliability thermal control systems study data handbook

    NASA Technical Reports Server (NTRS)

    Scollon, T. R., Jr.; Carpitella, M. J.

    1971-01-01

    The development of thermal control systems with high reliability and long service life is discussed. Various passive and semi-active thermal control systems which have been installed on space vehicles are described. The properties of the various coatings are presented in tabular form.

  6. System reliability and risk assessment task goals and status

    NASA Technical Reports Server (NTRS)

    Cruse, T. A.; Mahadevan, S.

    1991-01-01

    The major focus for continued development of the Numerical Evaluation of Stochastic Structures Under Stress (NESSUS) codes is in support of system testing and certification of advanced propulsion systems. Propulsion system testing has evolved over the years from tests designed to show success, to tests designed to reveal reliability issues before service use. Such test conditions as performance envelope corners, high rotor imbalance, power dwells, and overspeed tests are designed to shake out problems that can be associated with low and high cycle fatigue, creep, and stress rupture, bearing durability, and the like. Subsystem testing supports system certification by standing as an early evaluation of the same durability and reliability concerns as for the entire system. The NESSUS software system is being further developed to support the definition of rigorous subsystem and system test definition and reliability certification. The principal technical issues are outlined which are related to system reliability, including key technology issues such as failure mode synergism, sequential failure mechanisms, and fault tree definition.

  7. Reliability-Based Decision Fusion in Multimodal Biometric Verification Systems

    NASA Astrophysics Data System (ADS)

    Kryszczuk, Krzysztof; Richiardi, Jonas; Prodanov, Plamen; Drygajlo, Andrzej

    2007-12-01

    We present a methodology of reliability estimation in the multimodal biometric verification scenario. Reliability estimation has shown to be an efficient and accurate way of predicting and correcting erroneous classification decisions in both unimodal (speech, face, online signature) and multimodal (speech and face) systems. While the initial research results indicate the high potential of the proposed methodology, the performance of the reliability estimation in a multimodal setting has not been sufficiently studied or evaluated. In this paper, we demonstrate the advantages of using the unimodal reliability information in order to perform an efficient biometric fusion of two modalities. We further show the presented method to be superior to state-of-the-art multimodal decision-level fusion schemes. The experimental evaluation presented in this paper is based on the popular benchmarking bimodal BANCA database.

  8. On reliable control system designs with and without feedback reconfigurations

    NASA Technical Reports Server (NTRS)

    Birdwell, J. D.; Castanon, D. A.; Athans, M.

    1979-01-01

    This paper contains an overview of a theoretical framework for the design of reliable multivariable control systems, with special emphasis on actuator failures and necessary actuator redundancy levels. Using a linear model of the system, with Markovian failure probabilities and quadratic performance index, an optimal stochastic control problem is posed and solved. The solution requires the iteration of a set of highly coupled Riccati-like matrix difference equations; if these converge one has a reliable design; if they diverge, the design is unreliable, and the system design cannot be stabilized. In addition, it is shown that the existence of a stabilizing constant feedback gain and the reliability of its implementation is equivalent to the convergence properties of a set of coupled Riccati-like matrix difference equations. In summary, these results can be used for offline studies relating the open loop dynamics, required performance, actuator mean time to failure, and functional or identical actuator redundancy, with and without feedback gain reconfiguration strategies.

  9. Reliability of Rechargeable Batteries in a Photovoltaic Power Supply System

    SciTech Connect

    Barney, P.; Jungst, R.G., Ingersoll, D.; O'Gorman, C.; Paez, T.L.; Urbina, A.

    1998-11-30

    We investigate the reliability If a rechargeable battery acting as the energy storage component in a photovoltaic power supply system. A model system was constructed for this that includes the solar resource, the photovoltaic power supp Iy system, the rechargeable battery and a load. The solar resource and the system load are modeled as SI ochastic processes. The photovoltaic system and the rechargeable battery are modeled deterministically, imd an artificial neural network is incorporated into the model of the rechargeable battery to simulate dartage that occurs during deep discharge cycles. The equations governing system behavior are solved simultaneously in the Monte Carlo framework and a fwst passage problem is solved to assess system reliability.

  10. Laboratory Information Management System Chain of Custody: Reliability and Security

    PubMed Central

    Tomlinson, J. J.; Elliott-Smith, W.; Radosta, T.

    2006-01-01

    A chain of custody (COC) is required in many laboratories that handle forensics, drugs of abuse, environmental, clinical, and DNA testing, as well as other laboratories that want to assure reliability of reported results. Maintaining a dependable COC can be laborious, but with the recent establishment of the criteria for electronic records and signatures by US regulatory agencies, laboratory information management systems (LIMSs) are now being developed to fully automate COCs. The extent of automation and of data reliability can vary, and FDA- and EPA-compliant electronic signatures and system security are rare. PMID:17671623

  11. Looking south at boiler feedwater pumps (steam turbine pump on ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Looking south at boiler feedwater pumps (steam turbine pump on left, electric motor pump on right). - Wheeling-Pittsburgh Steel Corporation, Allenport Works, Boiler House, Route 88 on West bank of Monongahela River, Allenport, Washington County, PA

  12. Experience in the repair of steam generator auxiliary feedwater nozzle

    SciTech Connect

    Chao, K.K.N.

    1996-12-01

    The auxiliary feedwater nozzle is quite often subjected to more thermal stress cycles and other loading mechanisms during their service life than the material was designed and fabricated for at the nozzle of the earlier steam generators in many nuclear plants. During plant operation, the auxiliary feedwater nozzle outlet is exposed to the hot steam from the generator side, while the auxiliary feedwater piping which contains subcooled water from the inlet often induces water hammer as a result of the steam-water mixing phenomena. The thermal cycles and the steam bubble collapse at the nozzle may cause cracking in the nozzle liner and interior surface of the nozzle, and subsequently results in structural damage to the steam generator. This presentation is intended to share the lessons learned from the evaluation of the nozzle condition and the subsequent modification and repair made to the auxiliary feedwater nozzle at the Palisades Nuclear Plant. Other nuclear plant owners may benefit from this experience.

  13. 29. NORTHWEST VIEW OF BOILER FEEDWATER CHEMICAL REACTION TANKS, WITH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    29. NORTHWEST VIEW OF BOILER FEEDWATER CHEMICAL REACTION TANKS, WITH FORMER GENERAL OFFICE BUILDING IN BACKGROUND. - U.S. Steel Duquesne Works, Fuel & Utilities Plant, Along Monongahela River, Duquesne, Allegheny County, PA

  14. Detail view of feedwater pump (below) and preheater tanks (above) ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail view of feedwater pump (below) and preheater tanks (above) in boiler house. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV

  15. Corrosion-related failures in feedwater heaters. Final report

    SciTech Connect

    Beavers, J.A.; Agrawal, A.K.; Berry, W.E.

    1983-07-01

    A survey of the literature was performed for the Electric Power Research Institute on corrosion-related failures in feedwater heaters. The survey was directed toward failures in fossil and in pressurized water reactor (PWR) nuclear power plants, but includes some pertinent information related to failures in boiling water reactor (BWR) power plants. The survey was organized into sections on the commonly used feedwater heater materials; C steel, brasses, Cu-Ni alloys, MONEL Alloy 400, and Type 304 Stainless Steel. A section on Ti as a potential feedwater heater material also is given in the appendices. Each section is divided into subsections on field experience and laboratory studies tat relate to the field failures that have been observed. Appendices are given on a feedwater heater description, water quality in power plants, forms of corrosion, and failure analysis techniques.

  16. 77 FR 7526 - Interpretation of Protection System Reliability Standard

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-13

    ... Making, 75 FR 81,152 (Dec. 27, 2010), FERC Stats. & Regs. ] 32,669 (2010). I. Background 2. Section 215... (Transmission and Generation Protection System Maintenance and Testing). On December 16, 2010, the Commission... R1 of Commission- approved Reliability Standard PRC-005-1 (Transmission and Generation...

  17. Development of dual solid cryogens for high reliability refrigeration system

    NASA Technical Reports Server (NTRS)

    Caren, R. P.; Coston, R. M.

    1967-01-01

    High reliability solid cryogen refrigeration system consists of a container initially filled with a solid cryogen which is coupled thermally to an infrared detector by means of a link of high thermal conductivity extending from a heat exchanger within the cryogen container.

  18. Automated Energy Distribution and Reliability System (AEDR): Final Report

    SciTech Connect

    Buche, D. L.

    2008-07-01

    This report describes Northern Indiana Public Service Co. project efforts to develop an automated energy distribution and reliability system. The purpose of this project was to implement a database-driven GIS solution that would manage all of the company's gas, electric, and landbase objects.

  19. Automated Energy Distribution and Reliability System Status Report

    SciTech Connect

    Buche, D. L.; Perry, S.

    2007-10-01

    This report describes Northern Indiana Public Service Co. project efforts to develop an automated energy distribution and reliability system. The purpose of this project was to implement a database-driven GIS solution that would manage all of the company's gas, electric, and landbase objects.

  20. DRINKING WATER DISTRIBUTION SYSTEM RELIABILITY: A CASE STUDY

    EPA Science Inventory

    The purpose of the study was to present a tool useful to water utilities that not only could analyze historical distribution system reliability data, but also provide a flexible and expandable mechanism for record-keeping enabling overall management of water work's facilities and...

  1. Modular reliability modeling of the TJNAF personnel safety system

    SciTech Connect

    Cinnamon, J.; Mahoney, K.

    1997-08-01

    A reliability model for the Thomas Jefferson National Accelerator Facility (formerly CEBAF) personnel safety system has been developed. The model, which was implemented using an Excel spreadsheet, allows simulation of all or parts of the system. Modularity of the model's implementation allows rapid {open_quotes}what if{open_quotes} case studies to simulate change in safety system parameters such as redundancy, diversity, and failure rates. Particular emphasis is given to the prediction of failure modes which would result in the failure of both of the redundant safety interlock systems. In addition to the calculation of the predicted reliability of the safety system, the model also calculates availability of the same system. Such calculations allow the user to make tradeoff studies between reliability and availability, and to target resources to improving those parts of the system which would most benefit from redesign or upgrade. The model includes calculated, manufacturer's data, and Jefferson Lab field data. This paper describes the model, methods used, and comparison of calculated to actual data for the Jefferson Lab personnel safety system. Examples are given to illustrate the model's utility and ease of use.

  2. Modular reliability modeling of the TJNAF personnel safety system

    SciTech Connect

    Cinnamon, J.; Mahoney, K.

    1997-08-01

    A reliability model for the Thomas Jefferson National Accelerator Facility (formerly CEBAF) personnel safety system has been developed. The model, which was implemented using an Excel spreadsheet, allows simulation of all or parts of the system. Modularity os the model`s implementation allows rapid {open_quotes}what if{open_quotes} case studies to simulate change in safety system parameters such as redundancy, diversity, and failure rates. Particular emphasis is given to the prediction of failure modes which would result in the failure of both of the redundant safety interlock systems. In addition to the calculation of the predicted reliability of the safety system, the model also calculates availability of the same system. Such calculations allow the user to make tradeoff studies between reliability and availability, and to target resources to improving those parts of the system which would most benefit from redesign or upgrade. The model includes calculated, manufacturer`s data, and Jefferson Lab field data. This paper describes the model, methods used, and comparison of calculated to actual data for the Jefferson Lab personnel safety system. Examples are given to illustrate the model`s utility and ease of use.

  3. Plant data comparisons for Comanche Peak 1/2 main feedwater pump trip transient

    SciTech Connect

    Boatwright, W.J.; Choe, W.G; Hiltbrand, D.W.

    1995-09-01

    A RETRAN-02 MOD5 model of Comanche Peak Steam Electric Station was developed by TU Electric for the purpose of performing core reload safety analyses. In order to qualify this model, comparisons against plant transient data from a partial loss of main feedwater flow were performed. These comparisons demonstrated that good representations of the plant response could be obtained with RETRAN-02 and the user-developed models of the primary-to-secondary heat transfer and plant control systems.

  4. Electrical network reliability and system blackout development simulations

    NASA Astrophysics Data System (ADS)

    Nepomnyashchiy, V. A.

    2015-12-01

    The main regulations of the author's model of electrical network reliability and system blackout development are stated. The model allows one to analytically determine the main technical and economic parameters indicators of reliability of electrical network operation, taking into account the generating power dislocations and electric loads, operation conditions, and dynamic and static stability of operation, while simultaneously calculating short circuit currents. The model also considers open-phase modes at singlephase short circuits and allows one to choose the most efficient operation conditions. The calculations are finished with an estimate of the annual averages of undersupply of energy and economic losses of customers due to their power supply interruptions.

  5. Reliability program requirements for Space and Terrestrial Nuclear Power Systems

    SciTech Connect

    Not Available

    1982-10-01

    The objectives of the reliability program requirements described in this report are (1) to provide contractors with an outline of the reliability requirements established by the Department of Energy (DOE) in the areas of design, development, production, testing, and acceptance of space and terrestrial nuclear systems hardware, and (2) to guide the contractor in meeting these requirements. This publication or particular portions of it is applicable as specified in the contract. Whether the contractors/subcontractors are subject to all the requirements or only to part of them will be specified by contract, program letter, or by the contract statement-of-work.

  6. Software safety and reliability issues in safety-related systems

    SciTech Connect

    Zucconi, L.

    1992-09-01

    The increasing number of accidents attributed to computer-based systems is causing increased public awareness of the risk associated with these systems' use in safety-related applications. Examples include the Therac-25 medical LINAC deaths, the growing number of Airbus A320 crashes, the AT T Long-Lines disaster on Martin Luther King Day in 1990, the spate of regional telephone outages of the summer of 1991, and many more. How do safety and reliability sometimes conflict What practical computer system and software development technologies and processes can be applied to increase the safety and reliability of computer systems What are the technical and managerial issues contributing to the construction of less-than-safe computer-based systems How can systems engineers and software engineers work together. to address the issues related to safety and reliability of computer systems This paper will address these topics and include an assessment of the best current state-of-the-practice and upcoming technologies that will carry us into the 21st century.

  7. Safety and reliability issues in safety-related systems

    SciTech Connect

    Zucconi, L.

    1992-03-20

    The increasing number of accidents attributed to computer-based systems is causing increased public awareness of the risk associated with these systems` use in safety-related applications. Examples include the Therac-25 medical LINAC deaths, the growing number of Airbus A320 crashes, the AT&T Long-Lines disaster on Martin Luther King Day in 1990, the spate of regional telephone outages of the summer of 1991, and many more. How do safety and reliability sometimes conflict? What practical computer system and software development technologies and processes can be applied to increase the safety and reliability of computer systems? What are the technical and managerial issues contributing to the construction of less-than-safe computer-based systems? How can systems engineers and software engineers work together to address the issues related safety and reliability of computer systems? This paper will address these topics and include an assessment of the best current state-of-the-practice and of upcoming technologies that will carry us into the 21st century.

  8. Software safety and reliability issues in safety-related systems

    SciTech Connect

    Zucconi, L.

    1992-09-01

    The increasing number of accidents attributed to computer-based systems is causing increased public awareness of the risk associated with these systems` use in safety-related applications. Examples include the Therac-25 medical LINAC deaths, the growing number of Airbus A320 crashes, the AT&T Long-Lines disaster on Martin Luther King Day in 1990, the spate of regional telephone outages of the summer of 1991, and many more. How do safety and reliability sometimes conflict? What practical computer system and software development technologies and processes can be applied to increase the safety and reliability of computer systems? What are the technical and managerial issues contributing to the construction of less-than-safe computer-based systems? How can systems engineers and software engineers work together. to address the issues related to safety and reliability of computer systems? This paper will address these topics and include an assessment of the best current state-of-the-practice and upcoming technologies that will carry us into the 21st century.

  9. Safety and reliability issues in safety-related systems

    SciTech Connect

    Zucconi, L.

    1992-03-20

    The increasing number of accidents attributed to computer-based systems is causing increased public awareness of the risk associated with these systems' use in safety-related applications. Examples include the Therac-25 medical LINAC deaths, the growing number of Airbus A320 crashes, the AT T Long-Lines disaster on Martin Luther King Day in 1990, the spate of regional telephone outages of the summer of 1991, and many more. How do safety and reliability sometimes conflict What practical computer system and software development technologies and processes can be applied to increase the safety and reliability of computer systems What are the technical and managerial issues contributing to the construction of less-than-safe computer-based systems How can systems engineers and software engineers work together to address the issues related safety and reliability of computer systems This paper will address these topics and include an assessment of the best current state-of-the-practice and of upcoming technologies that will carry us into the 21st century.

  10. An integrated approach to system design, reliability, and diagnosis

    NASA Technical Reports Server (NTRS)

    Patterson-Hine, F. A.; Iverson, David L.

    1990-01-01

    The requirement for ultradependability of computer systems in future avionics and space applications necessitates a top-down, integrated systems engineering approach for design, implementation, testing, and operation. The functional analyses of hardware and software systems must be combined by models that are flexible enough to represent their interactions and behavior. The information contained in these models must be accessible throughout all phases of the system life cycle in order to maintain consistency and accuracy in design and operational decisions. One approach being taken by researchers at Ames Research Center is the creation of an object-oriented environment that integrates information about system components required in the reliability evaluation with behavioral information useful for diagnostic algorithms. Procedures have been developed at Ames that perform reliability evaluations during design and failure diagnoses during system operation. These procedures utilize information from a central source, structured as object-oriented fault trees. Fault trees were selected because they are a flexible model widely used in aerospace applications and because they give a concise, structured representation of system behavior. The utility of this integrated environment for aerospace applications in light of our experiences during its development and use is described. The techniques for reliability evaluation and failure diagnosis are discussed, and current extensions of the environment and areas requiring further development are summarized.

  11. The REPAS Study: Reliability Evaluation of Passive Safety Systems

    SciTech Connect

    Ricotti, M.E.; Bianchi, F.; Burgazzi, L.; D'Auria, F.; Galassi, G.

    2002-07-01

    The strategy of approach to the problem moves from the consideration that a passive system should be theoretically more reliable than an active one. In fact it does not need any external input or energy to operate and it relies only upon natural physical laws (e.g. gravity, natural circulation, internally stored energy, etc.) and/or 'intelligent' use of the energy inherently available in the system (e.g. chemical reaction, decay heat, etc.). Nevertheless the passive system may fail its mission not only as a consequence of classical mechanical failure of components, but also for deviation from the expected behaviour, due to physical phenomena mainly related to thermal-hydraulics or due to different boundary and initial conditions. The main sources of physical failure are identified and a probability of occurrence is assigned. The reliability analysis is performed on a passive system which operates in two-phase, natural circulation. The selected system is a loop including a heat source and a heat sink where the condensation occurs. The system behavior under different configurations has been simulated via best-estimate code (Relap5 mod3.2). The results are shown and can be treated in such a way to give qualitative and quantitative information on the system reliability. Main routes of development of the methodology are also depicted. (authors)

  12. Passive System Reliability Analysis: A Study on the Isolation Condenser

    SciTech Connect

    Burgazzi, Luciano

    2002-07-15

    This paper deals with the reliability assessment of passive systems that have been developed in recent years by suppliers, industries, utilities, and research organizations, aimed at plant safety improvement and substantial simplification in its implementation. The present study concerns the passive decay heat removal systems that use, for the most part, a condenser immersed in a cooling pool. The focus of the paper is a reliability study of the isolation condenser system foreseen for advanced boiling water reactors (BWRs) for the removal of the excess sensible and core decay heat from the BWR by natural circulation. Furthermore, an approach aimed at the thermal-hydraulic performance assessment (i.e., the natural circulation failure evaluation) from the probability point of view is given. The study is not plant-specific-related but pertains to the conceptual design of the foregoing system.

  13. Reliability of emergency ac power systems at nuclear power plants

    SciTech Connect

    Battle, R E; Campbell, D J

    1983-07-01

    Reliability of emergency onsite ac power systems at nuclear power plants has been questioned within the Nuclear Regulatory Commission (NRC) because of the number of diesel generator failures reported by nuclear plant licensees and the reactor core damage that could result from diesel failure during an emergency. This report contains the results of a reliability analysis of the onsite ac power system, and it uses the results of a separate analysis of offsite power systems to calculate the expected frequency of station blackout. Included is a design and operating experience review. Eighteen plants representative of typical onsite ac power systems and ten generic designs were selected to be modeled by fault trees. Operating experience data were collected from the NRC files and from nuclear plant licensee responses to a questionnaire sent out for this project.

  14. Development of a composite system reliability evaluation program

    SciTech Connect

    Pereira, M.V.F.; Pinto, L.M.V.G. ); Mazumdar, M.; Yengar, S.I. )

    1990-08-01

    This report describes in detail the mathematical models and techniques used in the development of a new composite reliability evaluation tool, CREAM. The methodology is based on Monte Carlo sampling of equipment availability (generators and circuits, including weather-dependent and common-cause or dependent outages) and load level (including system load or bus load vector scenario). The analysis of a sampled scenario is based on the linearized power flow model. Remedial actions and load curtailment are carried out by an efficient linear programming routine. Besides calculating adequacy indices (LOLP and EPNS) both at system and bus levels, the program produces the sensitivity of the reliability indices with respect to incremental reinforcements of generation capacities and circuit capacities. The required number of Monte Carlo samples is reduced through a new variance reduction technique, which uses analytical models (such a single-bus generation capacity reliability model) as a regression variable.'' The component of reliability indices explained'' by these variables is then factored out'' of the Monte Carlo sampling scheme. The program is demonstrated in case studies with two 500-bus utility-derived test systems. 12 refs., 1 fig., 7 tabs.

  15. Development of a composite system reliability evaluation program

    SciTech Connect

    Pereira, M.V.F.; Pinto, L.M.V.G. ); Mazumdar, M.; Yengar, S.I. )

    1990-08-01

    This report describes the methodology and computational results of a new composite reliability evaluation tool, CREAM. The methodology is based on Monte Carlo sampling of equipment availability (generators and circuits, including weather-dependent and common-cause or dependent outages) and load level (including system load or bus load vector scenario). The analysis of a samples scenario is based on the linearized power flow model. Remedial actions and load curtailment are carried out by an efficient linear programming routine. Besides calculating adequacy indices (LOLP and EPNS) both at system and bus levels, the program produces the sensitivity of the reliability indices with respect to incremental reinforcements of generation capacities and circuit capacities. The required number of Monte Carlo samples is reduced through a new variance reduction technique, which uses analytical models (such a single-bus generation capacity reliability model) as a regression variable.'' The component of reliability indices explained'' by these variables is then factored out'' of the Monte Carlo sampling scheme. The program is demonstrated in case studies with two 500-bus utility-derived test systems. 17 refs., 10 figs., 18 tabs.

  16. Development of a composite system reliability evaluation program

    SciTech Connect

    Pereira, M.V.F.; Pinto, L.M.V.G. ); Mazumdar, M.; Yengar, S.I. )

    1990-08-01

    This report describes the input data format and installation details of a new composite reliability evaluation tool, CREAM. The methodology is based on Monte Carlo sampling of equipment availability (generators and circuits, including weather-dependent and common-cause or dependent outages) and load level (including system load or bus load vector scenario). The analysis of a sampled scenario is based on the linearized power flow model. Remedial actions and load curtailment are carried out by an efficient linear programming routine. Besides calculating adequacy indices (LOLP and EPNS) both at system and bus levels, the program produces the sensitivity of the reliability indices with respect to incremental reinforcements of generation capacities and circuit capacities. The required number of Monte Carlo samples is reduced through a new variance reduction technique, which uses analytical models (such a single-bus generation capacity reliability model) as a regression variable.'' The component of reliability indices explained'' by these variables is then factored out'' of the Monte Carlo sampling scheme. The program is demonstrated in case studies with two 500-bus utility-derived test systems.

  17. Packaging and Reliability Issues in Micro/Nano Systems

    NASA Astrophysics Data System (ADS)

    Kim, Jongbaeg; Cheng, Yu-Ting; Chiao, Mu; Lin, Liwei

    The potential of MEMS/NEMS technologies has been viewed as a revolution comparable or even bigger than that of microelectronics. These scientific and engineering advancements in micro-/nano-electromechanical systems (MEMS)/(NEMS) could bring previously unthinkable applications to reality, from space systems, environmental instruments, to daily-life appliances. As presented in previous chapters, the development of core MEMS/NEMS processes has already demonstrated a lot of commercial applications as well as future potentials with elaborate functionalities. However, creating a low-cost reliable package for the protection of these MEMS/NEMS products is still a very difficult task. Without addressing these packaging and reliability issues, no commercial products can be sold on the market. Packaging design and modeling, packaging material selection, packaging process integration, and packaging cost are the main issues to be considered. In this chapter, we will present the fundamentals of MEMS/NEMS packaging technology, including packaging processes, hermetic and vacuum encapsulations, thermal issues, packaging reliability, and future packaging trends. The future development of MEMS packaging will rely on the success of the implementation of several unique techniques, such as packaging design kits for system and circuit designer, low-cost wafer-level and chip-scale packaging techniques, effective testing techniques, and reliable fabrication of an interposer [56.1] with vertical through-interconnects for device integrations.

  18. Practical reliability and uncertainty quantification in complex systems : final report.

    SciTech Connect

    Grace, Matthew D.; Ringland, James T.; Marzouk, Youssef M.; Boggs, Paul T.; Zurn, Rena M.; Diegert, Kathleen V.; Pebay, Philippe Pierre; Red-Horse, John Robert

    2009-09-01

    The purpose of this project was to investigate the use of Bayesian methods for the estimation of the reliability of complex systems. The goals were to find methods for dealing with continuous data, rather than simple pass/fail data; to avoid assumptions of specific probability distributions, especially Gaussian, or normal, distributions; to compute not only an estimate of the reliability of the system, but also a measure of the confidence in that estimate; to develop procedures to address time-dependent or aging aspects in such systems, and to use these models and results to derive optimal testing strategies. The system is assumed to be a system of systems, i.e., a system with discrete components that are themselves systems. Furthermore, the system is 'engineered' in the sense that each node is designed to do something and that we have a mathematical description of that process. In the time-dependent case, the assumption is that we have a general, nonlinear, time-dependent function describing the process. The major results of the project are described in this report. In summary, we developed a sophisticated mathematical framework based on modern probability theory and Bayesian analysis. This framework encompasses all aspects of epistemic uncertainty and easily incorporates steady-state and time-dependent systems. Based on Markov chain, Monte Carlo methods, we devised a computational strategy for general probability density estimation in the steady-state case. This enabled us to compute a distribution of the reliability from which many questions, including confidence, could be addressed. We then extended this to the time domain and implemented procedures to estimate the reliability over time, including the use of the method to predict the reliability at a future time. Finally, we used certain aspects of Bayesian decision analysis to create a novel method for determining an optimal testing strategy, e.g., we can estimate the 'best' location to take the next test to

  19. Reliability Analysis of Systems Subject to First-Passage Failure

    NASA Technical Reports Server (NTRS)

    Lutes, Loren D.; Sarkani, Shahram

    2009-01-01

    An obvious goal of reliability analysis is the avoidance of system failure. However, it is generally recognized that it is often not feasible to design a practical or useful system for which failure is impossible. Thus it is necessary to use techniques that estimate the likelihood of failure based on modeling the uncertainty about such items as the demands on and capacities of various elements in the system. This usually involves the use of probability theory, and a design is considered acceptable if it has a sufficiently small probability of failure. This report contains findings of analyses of systems subject to first-passage failure.

  20. Determination of Turboprop Reduction Gearbox System Fatigue Life and Reliability

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin V.; Lewicki, David G.; Savage, Michael; Vlcek, Brian L.

    2007-01-01

    Two computational models to determine the fatigue life and reliability of a commercial turboprop gearbox are compared with each other and with field data. These models are (1) Monte Carlo simulation of randomly selected lives of individual bearings and gears comprising the system and (2) two-parameter Weibull distribution function for bearings and gears comprising the system using strict-series system reliability to combine the calculated individual component lives in the gearbox. The Monte Carlo simulation included the virtual testing of 744,450 gearboxes. Two sets of field data were obtained from 64 gearboxes that were first-run to removal for cause, were refurbished and placed back in service, and then were second-run until removal for cause. A series of equations were empirically developed from the Monte Carlo simulation to determine the statistical variation in predicted life and Weibull slope as a function of the number of gearboxes failed. The resultant L(sub 10) life from the field data was 5,627 hr. From strict-series system reliability, the predicted L(sub 10) life was 774 hr. From the Monte Carlo simulation, the median value for the L(sub 10) gearbox lives equaled 757 hr. Half of the gearbox L(sub 10) lives will be less than this value and the other half more. The resultant L(sub 10) life of the second-run (refurbished) gearboxes was 1,334 hr. The apparent load-life exponent p for the roller bearings is 5.2. Were the bearing lives to be recalculated with a load-life exponent p equal to 5.2, the predicted L(sub 10) life of the gearbox would be equal to the actual life obtained in the field. The component failure distribution of the gearbox from the Monte Carlo simulation was nearly identical to that using the strict-series system reliability analysis, proving the compatibility of these methods.

  1. Design for Verification: Using Design Patterns to Build Reliable Systems

    NASA Technical Reports Server (NTRS)

    Mehlitz, Peter C.; Penix, John; Koga, Dennis (Technical Monitor)

    2003-01-01

    Components so far have been mainly used in commercial software development to reduce time to market. While some effort has been spent on formal aspects of components, most of this was done in the context of programming language or operating system framework integration. As a consequence, increased reliability of composed systems is mainly regarded as a side effect of a more rigid testing of pre-fabricated components. In contrast to this, Design for Verification (D4V) puts the focus on component specific property guarantees, which are used to design systems with high reliability requirements. D4V components are domain specific design pattern instances with well-defined property guarantees and usage rules, which are suitable for automatic verification. The guaranteed properties are explicitly used to select components according to key system requirements. The D4V hypothesis is that the same general architecture and design principles leading to good modularity, extensibility and complexity/functionality ratio can be adapted to overcome some of the limitations of conventional reliability assurance measures, such as too large a state space or too many execution paths.

  2. Reliability evaluation of the Savannah River reactor leak detection system

    SciTech Connect

    Daugherty, W.L.; Sindelar, R.L. ); Wallace, I.T. )

    1991-01-01

    The Savannah River Reactors have been in operation since the mid-1950's. The primary degradation mode for the primary coolant loop piping is intergranular stress corrosion cracking. The leak-before-break (LBB) capability of the primary system piping has been demonstrated as part of an overall structural integrity evaluation. One element of the LBB analyses is a reliability evaluation of the leak detection system. The most sensitive element of the leak detection system is the airborne tritium monitors. The presence of small amounts of tritium in the heavy water coolant provide the basis for a very sensitive system of leak detection. The reliability of the tritium monitors to properly identify a crack leaking at a rate of either 50 or 300 lb/day (0.004 or 0.023 gpm, respectively) has been characterized. These leak rates correspond to action points for which specific operator actions are required. High reliability has been demonstrated using standard fault tree techniques. The probability of not detecting a leak within an assumed mission time of 24 hours is estimated to be approximately 5 {times} 10{sup {minus}5} per demand. This result is obtained for both leak rates considered. The methodology and assumptions used to obtain this result are described in this paper. 3 refs., 1 fig., 1 tab.

  3. Bayesian estimation of system reliability under asymmetric loss

    NASA Astrophysics Data System (ADS)

    Thompson, Ronald David

    This research is concerned with estimating the reliability of a k-out-of-p system when the lifetimes of its p components are iid, when subjective beliefs about the behavior of the system's individual components are available, and when losses corresponding to overestimation and underestimation errors can be approximated by a suitable family of asymmetric loss functions. Point estimates for such systems are discussed in the context of Bayes estimation with respect to loss functions. A set of properties is proposed as being minimal properties that all loss functions appropriate to reliability estimation might satisfy. Several families of asymmetric loss functions that satisfy these minimal properties are discussed, and their corresponding posterior Bayes estimators are derived. One of these families, squarex loss functions, is a generalization of linex loss functions. The concept of loss robustness is discussed in the context of parametric families of asymmetric loss functions. As an application, the reliability of O-rings critical to the 1986 catastrophic failure of the Space Shuttle Challenger is estimated. Point estimation of negative exponential stress-strength k-out-of-p systems with respect to reference priors is discussed in this context of asymmetric loss functions.

  4. Optimal reliability design method for remote solar systems

    NASA Astrophysics Data System (ADS)

    Suwapaet, Nuchida

    A unique optimal reliability design algorithm is developed for remote communication systems. The algorithm deals with either minimizing an unavailability of the system within a fixed cost or minimizing the cost of the system with an unavailability constraint. The unavailability of the system is a function of three possible failure occurrences: individual component breakdown, solar energy deficiency (loss of load probability), and satellite/radio transmission loss. The three mathematical models of component failure, solar power failure, transmission failure are combined and formulated as a nonlinear programming optimization problem with binary decision variables, such as number and type (or size) of photovoltaic modules, batteries, radios, antennas, and controllers. Three possible failures are identified and integrated in computer algorithm to generate the parameters for the optimization algorithm. The optimization algorithm is implemented with a branch-and-bound technique solution in MS Excel Solver. The algorithm is applied to a case study design for an actual system that will be set up in remote mountainous areas of Peru. The automated algorithm is verified with independent calculations. The optimal results from minimizing the unavailability of the system with the cost constraint case and minimizing the total cost of the system with the unavailability constraint case are consistent with each other. The tradeoff feature in the algorithm allows designers to observe results of 'what-if' scenarios of relaxing constraint bounds, thus obtaining the most benefit from the optimization process. An example of this approach applied to an existing communication system in the Andes shows dramatic improvement in reliability for little increase in cost. The algorithm is a real design tool, unlike other existing simulation design tools. The algorithm should be useful for other stochastic systems where component reliability, random supply and demand, and communication are

  5. Evaluation and testing of semiconductor laser reliability in optic system

    NASA Astrophysics Data System (ADS)

    Tang, Wenyan; Fan, Xianguang; Sun, Heyi

    2007-01-01

    In order to improve the performance of an optic system, a new evaluation and testing methodology for the light source which uses semiconductor laser is presented. A new system, combining high accuracy source and measure capabilities for pulsed testing, is developed to achieve the aim of automatic measurement of Light-Current-Power (LIV) for semiconductor laser. The test can provide customer with L-I, V-I curves and other correlative parameters, such as the threshold current and slope efficiency, and so on. Meanwhile, the change of environment temperature versus lasing wavelength under pulse injection is discussed, and the relationship between the lasing wavelength and the width and cycle of injection pulse is obtained. The temperature character of packaged laser unit is measured conveniently. Making use of the above examined curves and parameters, the reliability of semiconductor laser and quality of device can be compared directly and evaluated accurately. The technique is successfully applied for the evaluation of semiconductor laser reliability.

  6. System safety and reliability using object-oriented programming techniques

    SciTech Connect

    Patterson-Hine, F.A.; Koen, B.V.

    1987-01-01

    Direct evaluation fault tree codes have been written in recursive, list-processing computer languages such as PL/1 (PATREC-I) and LISP (PATREC-L). The pattern-matching strategy implemented in these codes has been used extensively in France to evaluate system reliability. Recent reviews of the risk management process suggest that a data base containing plant-specific information be integrated with a package of codes used for probabilistic risk assessment (PRA) to alleviate some of the difficulties that make a PRA so costly and time-intensive. A new programming paradigm, object-oriented programming, is uniquely suited for the development of such a software system. A knowledge base and fault tree evaluation algorithm, based on previous experience with PATREC-L, have been implemented using object-oriented techniques, resulting in a reliability assessment environment that is easy to develop, modify, and extend.

  7. Markov reliability models for digital flight control systems

    NASA Technical Reports Server (NTRS)

    Mcgough, John; Reibman, Andrew; Trivedi, Kishor

    1989-01-01

    The reliability of digital flight control systems can often be accurately predicted using Markov chain models. The cost of numerical solution depends on a model's size and stiffness. Acyclic Markov models, a useful special case, are particularly amenable to efficient numerical solution. Even in the general case, instantaneous coverage approximation allows the reduction of some cyclic models to more readily solvable acyclic models. After considering the solution of single-phase models, the discussion is extended to phased-mission models. Phased-mission reliability models are classified based on the state restoration behavior that occurs between mission phases. As an economical approach for the solution of such models, the mean failure rate solution method is introduced. A numerical example is used to show the influence of fault-model parameters and interphase behavior on system unreliability.

  8. Reliability Value of Fast State Estimation on Power Systems

    SciTech Connect

    Elizondo, Marcelo A.; Chen, Yousu; Huang, Zhenyu

    2012-05-07

    Monitoring the state of a power system under stress is key to achieving reliable operation. State estimation and timely measurements become more important when applying and designing corrective control actions (manual and automatic) to arrest or mitigate cascading blackouts. The execution time of each process, including state estimation, should be as short as possible to allow for timely action. In this paper, we provide a methodology for estimating one of the components of value of faster and more frequent state estimation: the reliability value of state estimation to assist corrective control actions for arresting or mitigating cascading blackouts. We present a new algorithm for estimating the time between successive line trips in a cascading failure. The algorithm combines power flow calculations with characteristics of the protection system to estimate the time between successive equipment trips. Using this algorithm, we illustrate the value of fast state estimation by calculating the time remaining for automatic or manual corrective actions after state estimation is finalized.

  9. Reliable compact electrical power source systems for space launch vehicles

    SciTech Connect

    Young, A.R.

    1996-12-31

    Described herein are several key technologies utilized in the design of a family of direct-drive turboalternator systems for space launch vehicles. These systems automatically provide conditioned and regulated electrical power at various voltages, powering actuators, valves, and avionics throughout the vehicle. The simple and robust ring-wound two-pole toothless alternator operates at peripheral speeds, making it suitable to be driven directly by a turbine, thereby eliminating the weight, reliability, zero ``g`` lubrication, and cooling issues of a speed-reducing gearbox, while allowing the turbine to operate at reasonable efficiency. Additionally, the use of self-aligning foil bearing and catalytic combustors or cold gas propellants enhance the reliability. The power conditioner and electronic controller provide hands-off regulated ac or dc power on demand, maintaining critical parameters within established limits and performance while reporting on built-in health-monitoring tests.

  10. Providing Reliability of Physical Systems: Partially Programmable Circuit Design

    NASA Astrophysics Data System (ADS)

    Matrosova, A. Yu.; Ostanin, S. A.; Kirienko, I. E.

    2014-10-01

    One of the important properties of physical systems is reliability.of their functioning, in particular, reliability of functioning of logical control components of the systems. A new approach to partially programmable circuit design that allows masking stuck-at faults at gate poles of logical circuits is considered. The logical circuit consists of gates. It is supposed that only one gate pole may be fault. There are reserved programmable blocks configurable logic blocks (CLBs) based on Look Up Table (LUT) technology that may mask the fault. First, the suggested approach in contrast to the well-known ones, allows masking any stuck-at fault rather than a part of them. Second, the approach is oriented to deriving more simple masking circuit from CLBs based on a compact description of incompletely specified functions of subcircuits.

  11. Comparison Modeling of System Reliability for Future NASA Projects

    NASA Technical Reports Server (NTRS)

    Gillespie, Amanda M.; Monaghan, Mark W.; Chen, Yuan

    2011-01-01

    A National Aeronautics and Space Administration (NASA) supported Reliability, Maintainability, and Availability (RMA) analysis team developed a unique RMA analysis methodology using cut set and importance measure analysis in order to comparison model proposed avionics computing architectures. In this paper we will present this efficient application of the RMA analysis methodology for importance measures that includes Reliability Block Diagram (RED) Analysis, Comparison modeling, Cut Set Analysis, and Importance Measure Analysis. We will also demonstrate that integrating RMA early in the system design process as a key to success by providing a fundamental decision metric supporting design selection. The RMA analysis methodology presented in this paper and applied to the avionics architectures enhances the usual way of predicting the need for redundancy based on failure rates or subject matter expert opinion. Using the REDs and the minimal cut sets, along with the Fussell-Vesely (FV) factors, importance measures are calculated for each functional element in the architectures. This paper presents an application of the FV importance measures and presents an improved methodology for using importance measures in success space (instead of failure space) to compare architectures. These importance measures are used to determine which functional element would be most likely to cause a system failure, thus, quickly identifying the path to increase the overall system reliability by either procuring more reliable functional elements or adding redundancy. This application of the RMA analysis methodology, using RBD analysis, cut set analysis, and the importance measure analysis, allows the avionics design team to better understand and compare the vulnerabilities in each of the architectures, enabling them to address the deficiencies in the design architectures more efficiently, while balancing the need to design for optimum weight and space allocations.

  12. Reliability of Fault Tolerant Control Systems. Part 2

    NASA Technical Reports Server (NTRS)

    Wu, N. Eva

    2000-01-01

    This paper reports Part II of a two part effort that is intended to delineate the relationship between reliability and fault tolerant control in a quantitative manner. Reliability properties peculiar to fault-tolerant control systems are emphasized, such as the presence of analytic redundancy in high proportion, the dependence of failures on control performance, and high risks associated with decisions in redundancy management due to multiple sources of uncertainties and sometimes large processing requirements. As a consequence, coverage of failures through redundancy management can be severely limited. The paper proposes to formulate the fault tolerant control problem as an optimization problem that maximizes coverage of failures through redundancy management. Coverage modeling is attempted in a way that captures its dependence on the control performance and on the diagnostic resolution. Under the proposed redundancy management policy, it is shown that an enhanced overall system reliability can be achieved with a control law of a superior robustness, with an estimator of a higher resolution, and with a control performance requirement of a lesser stringency.

  13. A reliability study of instrument air system design options

    SciTech Connect

    Guey, C.; Skelley, W. ); Gilbert, L.; Anoba, R.; Stutzke, M. )

    1992-01-01

    The existing instrument air system at Turkey Point station uses mobile diesel-driven air compressors. Although these diesel compressors have performed their function well, they represent a maintenance and financial burden requiring engineering review. An engineering evaluation is ongoing to develop several feasible conceptual design options to upgrade the instrument air systems. This phase-1 study was performed to assess the reliability of the various proposed design options. A phase-2 study will be conducted later to determine the core damage frequency for a selected option.

  14. Reliability measurement during software development. [for a multisensor tracking system

    NASA Technical Reports Server (NTRS)

    Hecht, H.; Sturm, W. A.; Trattner, S.

    1977-01-01

    During the development of data base software for a multi-sensor tracking system, reliability was measured. The failure ratio and failure rate were found to be consistent measures. Trend lines were established from these measurements that provided good visualization of the progress on the job as a whole as well as on individual modules. Over one-half of the observed failures were due to factors associated with the individual run submission rather than with the code proper. Possible application of these findings for line management, project managers, functional management, and regulatory agencies is discussed. Steps for simplifying the measurement process and for use of these data in predicting operational software reliability are outlined.

  15. Reliability-Based Control Design for Uncertain Systems

    NASA Technical Reports Server (NTRS)

    Crespo, Luis G.; Kenny, Sean P.

    2005-01-01

    This paper presents a robust control design methodology for systems with probabilistic parametric uncertainty. Control design is carried out by solving a reliability-based multi-objective optimization problem where the probability of violating design requirements is minimized. Simultaneously, failure domains are optimally enlarged to enable global improvements in the closed-loop performance. To enable an efficient numerical implementation, a hybrid approach for estimating reliability metrics is developed. This approach, which integrates deterministic sampling and asymptotic approximations, greatly reduces the numerical burden associated with complex probabilistic computations without compromising the accuracy of the results. Examples using output-feedback and full-state feedback with state estimation are used to demonstrate the ideas proposed.

  16. Summary of Research on Reliability Criteria-Based Flight System Control

    NASA Technical Reports Server (NTRS)

    Wu, N. Eva; Belcastro, Christine (Technical Monitor)

    2002-01-01

    This paper presents research on the reliability assessment of adaptive flight control systems. The topics include: 1) Overview of Project Focuses; 2) Reliability Analysis; and 3) Design for Reliability. This paper is presented in viewgraph form.

  17. An integrated approach to system design, reliability, and diagnosis

    NASA Technical Reports Server (NTRS)

    Patterson-Hine, F. A.; Iverson, David L.

    1990-01-01

    The requirement for ultradependability of computer systems in future avionics and space applications necessitates a top-down, integrated systems ingeneering approach for design, implementation, testing, and operation. The functional analyses of hardware and software systems must be combined by models that are flexible enough to represent their interactions and behavior. The information contained in these models must be accessible throughout all phases of the system life cycle in order to maintain consistency and accuracy in design and operational decisions. One approach being taken by researchers at Ames Research Center is the creation of an object-oriented environment that integrates information about system components required in the reliability evaluation with behavioral information useful for diagnostic algorithms.

  18. Aspects of efficient and reliable multibody system simulation

    NASA Technical Reports Server (NTRS)

    Schwertassek, R.; Fuehrer, C.; Rulka, W.

    1989-01-01

    Multibody system equations can be generated in various forms. All of these may be interpreted as results of two basic approaches, the augmentation- and the elimination-method. The former method yields the descriptor form of the system motion, a set of differential-algebraic equations (DAE), and the latter the state space representation, a minimal set of ordinary differential equations (ODE). Both of these methods are surveyed. Particular emphasis is on the discussion of recursive computational schemes, generating the equations of motion with a number of operations, which is proportional to the number N of system bodies (O(N)-formulations). For simulation purposes one would like to create that set of system equations, which can be generated most efficiently and for which the most efficient and reliable solution techniques are available. Numerical solution techniques for ODE have been studied in great detail and they are well-developed. By contrast, DAE have not been investigated for such a long time. In view of new developments in the latter field the generation of all the equations required for an efficient and reliable solution of DAE describing multibody system motion is discussed. These methods, i.e., an O(N)-formulation and new techniques for solving DAE, are implemented in the SIMPACK code. Its capabilities are illustrated by simulation of multibody robot models.

  19. The reliability of an instrumented start block analysis system.

    PubMed

    Tor, Elaine; Pease, David L; Ball, Kevin A

    2015-02-01

    The swimming start is highly influential to overall competition performance. Therefore, it is paramount to develop reliable methods to perform accurate biomechanical analysis of start performance for training and research. The Wetplate Analysis System is a custom-made force plate system developed by the Australian Institute of Sport--Aquatic Testing, Training and Research Unit (AIS ATTRU). This sophisticated system combines both force data and 2D digitization to measure a number of kinetic and kinematic parameter values in an attempt to evaluate start performance. Fourteen elite swimmers performed two maximal effort dives (performance was defined as time from start signal to 15 m) over two separate testing sessions. Intraclass correlation coefficients (ICC) were used to determine each parameter's reliability. The kinetic parameters all had ICC greater than 0.9 except the time of peak vertical force (0.742). This may have been due to variations in movement initiation after the starting signal between trials. The kinematic and time parameters also had ICC greater than 0.9 apart from for the time of maximum depth (0.719). This parameter was lower due to the swimmers varying their depth between trials. Based on the high ICC scores for all parameters, the Wetplate Analysis System is suitable for biomechanical analysis of swimming starts. PMID:25268512

  20. On reliable control system designs. Ph.D. Thesis; [actuators

    NASA Technical Reports Server (NTRS)

    Birdwell, J. D.

    1978-01-01

    A mathematical model for use in the design of reliable multivariable control systems is discussed with special emphasis on actuator failures and necessary actuator redundancy levels. The model consists of a linear time invariant discrete time dynamical system. Configuration changes in the system dynamics are governed by a Markov chain that includes transition probabilities from one configuration state to another. The performance index is a standard quadratic cost functional, over an infinite time interval. The actual system configuration can be deduced with a one step delay. The calculation of the optimal control law requires the solution of a set of highly coupled Riccati-like matrix difference equations. Results can be used for off-line studies relating the open loop dynamics, required performance, actuator mean time to failure, and functional or identical actuator redundancy, with and without feedback gain reconfiguration strategies.

  1. Spaceflight Ground Support Equipment Reliability & System Safety Data

    NASA Technical Reports Server (NTRS)

    Fernandez, Rene; Riddlebaugh, Jeffrey; Brinkman, John; Wilkinson, Myron

    2012-01-01

    Presented were Reliability Analysis, consisting primarily of Failure Modes and Effects Analysis (FMEA), and System Safety Analysis, consisting of Preliminary Hazards Analysis (PHA), performed to ensure that the CoNNeCT (Communications, Navigation, and Networking re- Configurable Testbed) Flight System was safely and reliably operated during its Assembly, Integration and Test (AI&T) phase. A tailored approach to the NASA Ground Support Equipment (GSE) standard, NASA-STD-5005C, involving the application of the appropriate Requirements, S&MA discipline expertise, and a Configuration Management system (to retain a record of the analysis and documentation) were presented. Presented were System Block Diagrams of selected GSE and the corresponding FMEA, as well as the PHAs. Also discussed are the specific examples of the FMEAs and PHAs being used during the AI&T phase to drive modifications to the GSE (via "redlining" of test procedures, and the placement of warning stickers to protect the flight hardware) before being interfaced to the Flight System. These modifications were necessary because failure modes and hazards were identified during the analysis that had not been properly mitigated. Strict Configuration Management was applied to changes (whether due to upgrades or expired calibrations) in the GSE by revisiting the FMEAs and PHAs to reflect the latest System Block Diagrams and Bill Of Material. The CoNNeCT flight system has been successfully assembled, integrated, tested, and shipped to the launch site without incident. This demonstrates that the steps taken to safeguard the flight system when it was interfaced to the various GSE were successful.

  2. Reliability and availability requirements analysis for DEMO: fuel cycle system

    SciTech Connect

    Pinna, T.; Borgognoni, F.

    2015-03-15

    The Demonstration Power Plant (DEMO) will be a fusion reactor prototype designed to demonstrate the capability to produce electrical power in a commercially acceptable way. Two of the key elements of the engineering development of the DEMO reactor are the definitions of reliability and availability requirements (or targets). The availability target for a hypothesized Fuel Cycle has been analysed as a test case. The analysis has been done on the basis of the experience gained in operating existing tokamak fusion reactors and developing the ITER design. Plant Breakdown Structure (PBS) and Functional Breakdown Structure (FBS) related to the DEMO Fuel Cycle and correlations between PBS and FBS have been identified. At first, a set of availability targets has been allocated to the various systems on the basis of their operating, protection and safety functions. 75% and 85% of availability has been allocated to the operating functions of fuelling system and tritium plant respectively. 99% of availability has been allocated to the overall systems in executing their safety functions. The chances of the systems to achieve the allocated targets have then been investigated through a Failure Mode and Effect Analysis and Reliability Block Diagram analysis. The following results have been obtained: 1) the target of 75% for the operations of the fuelling system looks reasonable, while the target of 85% for the operations of the whole tritium plant should be reduced to 80%, even though all the tritium plant systems can individually reach quite high availability targets, over 90% - 95%; 2) all the DEMO Fuel Cycle systems can reach the target of 99% in accomplishing their safety functions. (authors)

  3. Structuring an EPICS System to Optimize Reliability, Performance and Cost

    SciTech Connect

    Bickley, Matthew; White, Karen S

    2005-10-10

    Thomas Jefferson National Accelerator Facility (Jefferson Lab) uses EPICS as the basis for its control system, effectively operating a number of plants at the laboratory, including the Continuous Electron Beam Accelerator (CEBA), a Free Electron Laser (FEL), Central Helium Liquefier, and several ancillary systems. We now use over 200 distributed computers running over a complex segmented network with 350,000 EPICS records and 50,000 control points to support operation of two machines for three experimental halls, along with the supporting infrastructure. During the 10 years that EPICS has been in use we have made a number of design and implementation choices in the interest of optimizing control system reliability, performance, security and cost. At the highest level, the control system is divided into a number of distinct segments, each controlling a separate operational plant. This supports operational independence, and therefore reliability, and provides a more flexible environment for maintenance and support. The control system is relatively open, allowing any of the 300 account holders to look at data from any segment. However security and operational needs mandate restricted write access to the various control points based on each user's job function and the operational mode of the facility. Additionally, the large number of simultaneous users, coupled with the amount of available data, necessitates the use of throttling mechanisms such as a Nameserver, which effectively reduces broadcast traffic and improves application initialization performance. Our segmented approach provides natural boundaries for managing data flow and restricting access, using tools such as the EPICS Gateway and Channel Access Security. This architecture enables cost optimizations by allowing expensive resources, such as Oracle, to be effectively shared throughout the control system, while minimizing the impact of a failure in any single area. This paper discusses the various design

  4. HiRel: Hybrid Automated Reliability Predictor (HARP) integrated reliability tool system, (version 7.0). Volume 2: HARP tutorial

    NASA Technical Reports Server (NTRS)

    Rothmann, Elizabeth; Dugan, Joanne Bechta; Trivedi, Kishor S.; Mittal, Nitin; Bavuso, Salvatore J.

    1994-01-01

    The Hybrid Automated Reliability Predictor (HARP) integrated Reliability (HiRel) tool system for reliability/availability prediction offers a toolbox of integrated reliability/availability programs that can be used to customize the user's application in a workstation or nonworkstation environment. The Hybrid Automated Reliability Predictor (HARP) tutorial provides insight into HARP modeling techniques and the interactive textual prompting input language via a step-by-step explanation and demonstration of HARP's fault occurrence/repair model and the fault/error handling models. Example applications are worked in their entirety and the HARP tabular output data are presented for each. Simple models are presented at first with each succeeding example demonstrating greater modeling power and complexity. This document is not intended to present the theoretical and mathematical basis for HARP.

  5. Reliability and Maintainability Data for Liquid Metal Cooling Systems

    SciTech Connect

    Cadwallader, Lee Charles

    2015-05-01

    One of the coolants of interest for future fusion breeding blankets is lead-lithium. As a liquid metal it offers the advantages of high temperature operation for good station efficiency, low pressure, and moderate flow rate. This coolant is also under examination for use in test blanket modules to be used in the ITER international project. To perform reliability, availability, maintainability and inspectability (RAMI) assessment as well as probabilistic safety assessment (PSA) of lead-lithium cooling systems, component failure rate data are needed to quantify the system models. RAMI assessment also requires repair time data and inspection time data. This paper presents a new survey of the data sets that are available at present to support RAMI and PSA quantification. Recommendations are given for the best data values to use when quantifying system models.

  6. NLC Reliability Analysis Notes: Klystron-Modulator System (LCC-0029)

    SciTech Connect

    Wilson, Z.

    2004-03-23

    This paper address the reliability and availability issues to be faced in deploying and operating the klystron modulator assemblies proposed for the Next Linear Collider (NLC). The rf power sources are a major system of the NLC and require a high uptime in order to reach the goal of 0.85 availability. Since the NLC is made up of several systems, not just klystron-modulator assemblies, the availability goal for the assemblies must be higher than 0.85. Currently this goal is at least 0.95. This short paper summarizes the analysis currently under way to determine whether the design of the rf power system will meet the design availability goal.

  7. Value-based reliability-constrained power system stability

    NASA Astrophysics Data System (ADS)

    Elfayoumy, Mahmoud Khamil Aly

    For power system operation, the acceptance of reliability is determined on the basis of design criteria expressed in terms of contingencies of pre-defined severity that the system is able to withstand with acceptable transient and steady state performance. The essential operating objective is the delivery to the customers of power with acceptable quality at minimum cost. Both the meaning of "minimum cost" and "acceptable quality" are the result of a number of technical, economic, and ecological perceptions which evolve with time. In the work presented in this dissertation, an integrated framework for value-based reliability constrained power system stability with a benefit allocation scheme for multi utility power system is proposed. The scheme consists of two main parts. The first part proposes a scheme that uses multiple objective optimization that employs Goal Decision network approach and post optimization analysis to produce Pareto-Optimal control strategies and recommends a solution for the Decision-Maker. The second part deals with the economical analysis of the Pareto-Optimal control strategy in terms of cost/benefit analysis to find out the most economical control strategy using a set of indices. It also presents a benefit allocation strategy that is based on a proposed scheme utilizing game theory to model the cooperation and competition between the different utilities forming the power system. The proposed integrated scheme was tested on IEEE test systems and the results show that the proposed scheme is very efficient not only in optimizing both adequacy and security but also in assessing different control strategies economically while providing an efficient strategy for the benefit allocation.

  8. Reliability analysis of repairable systems using system dynamics modeling and simulation

    NASA Astrophysics Data System (ADS)

    Srinivasa Rao, M.; Naikan, V. N. A.

    2014-07-01

    Repairable standby system's study and analysis is an important topic in reliability. Analytical techniques become very complicated and unrealistic especially for modern complex systems. There have been attempts in the literature to evolve more realistic techniques using simulation approach for reliability analysis of systems. This paper proposes a hybrid approach called as Markov system dynamics (MSD) approach which combines the Markov approach with system dynamics simulation approach for reliability analysis and to study the dynamic behavior of systems. This approach will have the advantages of both Markov as well as system dynamics methodologies. The proposed framework is illustrated for a standby system with repair. The results of the simulation when compared with that obtained by traditional Markov analysis clearly validate the MSD approach as an alternative approach for reliability analysis.

  9. Study of turboprop systems reliability and maintenance costs

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The overall reliability and maintenance costs (R&MC's) of past and current turboprop systems were examined. Maintenance cost drivers were found to be scheduled overhaul (40%), lack of modularity particularly in the propeller and reduction gearbox, and lack of inherent durability (reliability) of some parts. Comparisons were made between the 501-D13/54H60 turboprop system and the widely used JT8D turbofan. It was found that the total maintenance cost per flight hour of the turboprop was 75% higher than that of the JT8D turbofan. Part of this difference was due to propeller and gearbox costs being higher than those of the fan and reverser, but most of the difference was in the engine core where the older technology turboprop core maintenance costs were nearly 70 percent higher than for the turbofan. The estimated maintenance cost of both the advanced turboprop and advanced turbofan were less than the JT8D. The conclusion was that an advanced turboprop and an advanced turbofan, using similar cores, will have very competitive maintenance costs per flight hour.

  10. System life and reliability modeling for helicopter transmissions

    NASA Technical Reports Server (NTRS)

    Savage, M.; Brikmanis, C. K.

    1986-01-01

    A computer program which simulates life and reliability of helicopter transmissions is presented. The helicopter transmissions may be composed of spiral bevel gear units and planetary gear units - alone, in series or in parallel. The spiral bevel gear units may have either single or dual input pinions, which are identical. The planetary gear units may be stepped or unstepped and the number of planet gears carried by the planet arm may be varied. The reliability analysis used in the program is based on the Weibull distribution lives of the transmission components. The computer calculates the system lives and dynamic capacities of the transmission components and the transmission. The system life is defined as the life of the component or transmission at an output torque at which the probability of survival is 90 percent. The dynamic capacity of a component or transmission is defined as the output torque which can be applied for one million output shaft cycles for a probability of survival of 90 percent. A complete summary of the life and dynamic capacity results is produced by the program.

  11. Reliability Considerations of ULP Scaled CMOS in Spacecraft Systems

    NASA Technical Reports Server (NTRS)

    White, Mark; MacNeal, Kristen; Cooper, Mark

    2012-01-01

    NASA, the aerospace community, and other high reliability (hi-rel) users of advanced microelectronic products face many challenges as technology continues to scale into the deep sub-micron region. Decreasing the feature size of CMOS devices not only allows more components to be placed on a single chip, but it increases performance by allowing faster switching (or clock) speeds with reduced power compared to larger scaled devices. Higher performance, and lower operating and stand-by power characteristics of Ultra-Low Power (ULP) microelectronics are not only desirable, but also necessary to meet low power consumption design goals of critical spacecraft systems. The integration of these components in such systems, however, must be balanced with the overall risk tolerance of the project.

  12. Reliability-based design optimization of multiphysics, aerospace systems

    NASA Astrophysics Data System (ADS)

    Allen, Matthew R.

    Aerospace systems are inherently plagued by uncertainties in their design, fabrication, and operation. Safety factors and expensive testing at the prototype level traditionally account for these uncertainties. Reliability-based design optimization (RBDO) can drastically decrease life-cycle development costs by accounting for the stochastic nature of the system response in the design process. The reduction in cost is amplified for conceptually new designs, for which no accepted safety factors currently exist. Aerospace systems often operate in environments dominated by multiphysics phenomena, such as the fluid-structure interaction of aeroelastic wings or the electrostatic-mechanical interaction of sensors and actuators. The analysis of such phenomena is generally complex and computationally expensive, and therefore is usually simplified or approximated in the design process. However, this leads to significant epistemic uncertainties in modeling, which may dominate the uncertainties for which the reliability analysis was intended. Therefore, the goal of this thesis is to present a RBDO framework that utilizes high-fidelity simulation techniques to minimize the modeling error for multiphysics phenomena. A key component of the framework is an extended reduced order modeling (EROM) technique that can analyze various states in the design or uncertainty parameter space at a reduced computational cost, while retaining characteristics of high-fidelity methods. The computational framework is verified and applied to the RBDO of aeroelastic systems and electrostatically driven sensors and actuators, utilizing steady-state analysis and design criteria. The framework is also applied to the design of electrostatic devices with transient criteria, which requires the use of the EROM technique to overcome the computational burden of multiple transient analyses.

  13. Space Shuttle Program Primary Avionics Software System (PASS) Success Legacy - Quality and Reliability Date

    NASA Technical Reports Server (NTRS)

    Orr, James K.; Peltier, Daryl

    2010-01-01

    Thsi slide presentation reviews the avionics software system on board the space shuttle, with particular emphasis on the quality and reliability. The Primary Avionics Software System (PASS) provides automatic and fly-by-wire control of critical shuttle systems which executes in redundant computers. Charts given show the number of space shuttle flights vs time, PASS's development history, and other charts that point to the reliability of the system's development. The reliability of the system is also compared to predicted reliability.

  14. A particle swarm model for estimating reliability and scheduling system maintenance

    NASA Astrophysics Data System (ADS)

    Puzis, Rami; Shirtz, Dov; Elovici, Yuval

    2016-05-01

    Modifying data and information system components may introduce new errors and deteriorate the reliability of the system. Reliability can be efficiently regained with reliability centred maintenance, which requires reliability estimation for maintenance scheduling. A variant of the particle swarm model is used to estimate reliability of systems implemented according to the model view controller paradigm. Simulations based on data collected from an online system of a large financial institute are used to compare three component-level maintenance policies. Results show that appropriately scheduled component-level maintenance greatly reduces the cost of upholding an acceptable level of reliability by reducing the need in system-wide maintenance.

  15. Reliability of windstorm predictions in the ECMWF ensemble prediction system

    NASA Astrophysics Data System (ADS)

    Becker, Nico; Ulbrich, Uwe

    2016-04-01

    Windstorms caused by extratropical cyclones are one of the most dangerous natural hazards in the European region. Therefore, reliable predictions of such storm events are needed. Case studies have shown that ensemble prediction systems (EPS) are able to provide useful information about windstorms between two and five days prior to the event. In this work, ensemble predictions with the European Centre for Medium-Range Weather Forecasts (ECMWF) EPS are evaluated in a four year period. Within the 50 ensemble members, which are initialized every 12 hours and are run for 10 days, windstorms are identified and tracked in time and space. By using a clustering approach, different predictions of the same storm are identified in the different ensemble members and compared to reanalysis data. The occurrence probability of the predicted storms is estimated by fitting a bivariate normal distribution to the storm track positions. Our results show, for example, that predicted storm clusters with occurrence probabilities of more than 50% have a matching observed storm in 80% of all cases at a lead time of two days. The predicted occurrence probabilities are reliable up to 3 days lead time. At longer lead times the occurrence probabilities are overestimated by the EPS.

  16. A Reliable Wireless Control System for Tomato Hydroponics.

    PubMed

    Ibayashi, Hirofumi; Kaneda, Yukimasa; Imahara, Jungo; Oishi, Naoki; Kuroda, Masahiro; Mineno, Hiroshi

    2016-01-01

    Agricultural systems using advanced information and communication (ICT) technology can produce high-quality crops in a stable environment while decreasing the need for manual labor. The system collects a wide variety of environmental data and provides the precise cultivation control needed to produce high value-added crops; however, there are the problems of packet transmission errors in wireless sensor networks or system failure due to having the equipment in a hot and humid environment. In this paper, we propose a reliable wireless control system for hydroponic tomato cultivation using the 400 MHz wireless band and the IEEE 802.15.6 standard. The 400 MHz band, which is lower than the 2.4 GHz band, has good obstacle diffraction, and zero-data-loss communication is realized using the guaranteed time-slot method supported by the IEEE 802.15.6 standard. In addition, this system has fault tolerance and a self-healing function to recover from faults such as packet transmission failures due to deterioration of the wireless communication quality. In our basic experiments, the 400 MHz band wireless communication was not affected by the plants' growth, and the packet error rate was less than that of the 2.4 GHz band. In summary, we achieved a real-time hydroponic liquid supply control with no data loss by applying a 400 MHz band WSN to hydroponic tomato cultivation. PMID:27164105

  17. A Reliable Wireless Control System for Tomato Hydroponics

    PubMed Central

    Ibayashi, Hirofumi; Kaneda, Yukimasa; Imahara, Jungo; Oishi, Naoki; Kuroda, Masahiro; Mineno, Hiroshi

    2016-01-01

    Agricultural systems using advanced information and communication (ICT) technology can produce high-quality crops in a stable environment while decreasing the need for manual labor. The system collects a wide variety of environmental data and provides the precise cultivation control needed to produce high value-added crops; however, there are the problems of packet transmission errors in wireless sensor networks or system failure due to having the equipment in a hot and humid environment. In this paper, we propose a reliable wireless control system for hydroponic tomato cultivation using the 400 MHz wireless band and the IEEE 802.15.6 standard. The 400 MHz band, which is lower than the 2.4 GHz band, has good obstacle diffraction, and zero-data-loss communication is realized using the guaranteed time-slot method supported by the IEEE 802.15.6 standard. In addition, this system has fault tolerance and a self-healing function to recover from faults such as packet transmission failures due to deterioration of the wireless communication quality. In our basic experiments, the 400 MHz band wireless communication was not affected by the plants’ growth, and the packet error rate was less than that of the 2.4 GHz band. In summary, we achieved a real-time hydroponic liquid supply control with no data loss by applying a 400 MHz band WSN to hydroponic tomato cultivation. PMID:27164105

  18. Code System to Calculate Integrated Reliability and Risk Analysis.

    Energy Science and Technology Software Center (ESTSC)

    2002-02-18

    Version 04 IRRAS Version 4.16, the latest in a series (2.0, 2.5, 4.0, 4.15), is a program developed for the purpose of performing those functions necessary to create and analyze a complete Probabilistic Risk Assessment (PRA). This program includes functions to allow the user to create event trees and fault trees, to define accident sequences and basic event failure data, to solve system and accident sequence fault trees, to quantify cut sets, and to performmore » uncertainty analysis on the results. Also included in this program are features to allow the analyst to generate reports and displays that can be used to document the results of an analysis. Since this software is a very detailed technical tool, the user of this program should be familiar with PRA concepts and the methods used to perform these analyses. IRRAS Version 4.16 is the latest in the stand-alone IRRAS series (2.0, 2.5, 4.0, 4.15). Be sure to review the PSR-405/ SAPHIRE 7.06 package which was released in January 2000 and includes three programs: the Integrated Reliability and Risk Analysis System (IRRAS), the System Analysis and Risk Assessment (SARA) system, the Models And Results Database (MAR-D) system, and the Fault tree, Event tree and P&ID (FEP) editors.« less

  19. Field Reliability of Comprehensive System Scoring in an Adolescent Inpatient Sample

    ERIC Educational Resources Information Center

    McGrath, Robert E.; Pogge, David L.; Stokes, John M.; Cragnolino, Ana; Zaccario, Michele; Hayman, Judy; Piacentini, Teresa; Wayland-Smith, Douglas

    2005-01-01

    The extent to which the Comprehensive System for the Rorschach is reliably scored has been a topic of some controversy. Although several studies have concluded it can be scored reliably in research settings, little is known about its reliability in field settings. This study evaluated the reliability of both response-level codes and protocol-level…

  20. System-reliability studies for wave-energy generation

    NASA Astrophysics Data System (ADS)

    Dawson, J. M.; Din, S.; Mytton, M. G.; Shore, N. L.; Stansfield, H. B.

    1980-06-01

    A study is reported that is being undertaken in the United Kingdom to determine means of developing the potential of the large wave-energy resource around the coast, in particular, that to the west facing the Atlantic. It is shown that derivation of the mean annual energy to be expected involved knowledge, not only of the wave climates, conversion efficiency characteristics of the proposed devices and of the power transmission system, but also of factors reflecting the availability overall. Attention is given to a simplified approach to the quantifying of reliability for each stage of the process. An appropriate method of analysis is established and a summary of the results obtained is given.

  1. Analysis of the reliability of submersible centrifugal electric pumping systems

    SciTech Connect

    Shilyaev, V.A.; Solodovnikov, G.G.; Vikhman, R.G.; Koshelev, V.A.; Zhitina, G.S.; Chirkova, N.I.

    1987-01-01

    A modern submersible centrifugal electric pumping system (SCEPS) for oil production consists of a submersible part which includes a centrifugal pump, an electric motor, a hydroprotection arrangement, a cable line, and an aboveground part that includes a control station and a transformer. The author discusses the mean service life of the submersible part of the SCEPS as the most important parameter of reliability of the SCEPS. The effect of the operating factors is assessed by calculating the mean service life of the submersible part of the typical SCEPS, making allowance for failures resulting from all causes. The mean operating time until failure of the submersible part of the new SCEPS due to design and technological error was determined.

  2. First Stage of a Highly Reliable Reusable Launch System

    NASA Technical Reports Server (NTRS)

    Kloesel, Kurt J.; Pickrel, Jonathan B.; Sayles, Emily L.; Wright, Michael; Marriott, Darin; Holland, Leo; Kuznetsov, Stephen

    2009-01-01

    Electromagnetic launch assist has the potential to provide a highly reliable reusable first stage to a space access system infrastructure at a lower overall cost. This paper explores the benefits of a smaller system that adds the advantages of a high specific impulse air-breathing stage and supersonic launch speeds. The method of virtual specific impulse is introduced as a tool to emphasize the gains afforded by launch assist. Analysis shows launch assist can provide a 278-s virtual specific impulse for a first-stage solid rocket. Additional trajectory analysis demonstrates that a system composed of a launch-assisted first-stage ramjet plus a bipropellant second stage can provide a 48-percent gross lift-off weight reduction versus an all-rocket system. The combination of high-speed linear induction motors and ramjets is identified, as the enabling technologies and benchtop prototypes are investigated. The high-speed response of a standard 60 Hz linear induction motor was tested with a pulse width modulated variable frequency drive to 150 Hz using a 10-lb load, achieving 150 mph. A 300-Hz stator-compensated linear induction motor was constructed and static-tested to 1900 lbf average. A matching ramjet design was developed for use on the 300-Hz linear induction motor.

  3. Reliable sources and uncertain decisions in multisensor systems

    NASA Astrophysics Data System (ADS)

    Minor, Christian; Johnson, Kevin

    2015-05-01

    Conflict among information sources is a feature of fused multisource and multisensor systems. Accordingly, the subject of conflict resolution has a long history in the literature of data fusion algorithms such as that of Dempster-Shafer theory (DS). Most conflict resolution strategies focus on distributing the conflict among the elements of the frame of discernment (the set of hypotheses that describe the possible decisions for which evidence is obtained) through rescaling of the evidence. These "closed-world" strategies imply that conflict is due to the uncertainty in evidence sources stemming from their reliability. An alternative approach is the "open-world" hypothesis, which allows for the presence of "unknown" elements not included in the original frame of discernment. Here, conflict must be considered as a result of uncertainty in the frame of the discernment, rather than solely the province of evidence sources. Uncertainty in the operating environment of a fused system is likely to appear as an open-world scenario. Understanding the origin of conflict (source versus frame of discernment uncertainty) is a challenging area for research in fused systems. Determining the ratio of these uncertainties provides useful insights into the operation of fused systems and confidence in their decisions for a variety of operating environments. Results and discussion for the computation of these uncertainties are presented for several combination rules with simulated data sets.

  4. A Statistical Approach to Characterizing the Reliability of Systems Utilizing HBT Devices

    NASA Technical Reports Server (NTRS)

    Chen, Yuan; Wang, Qing; Kayali, Sammy

    2004-01-01

    This paper presents a statistical approach to characterizing the reliability of systems with HBT devices. The proposed approach utilizes the statistical reliability information of the HBT individual devices, along with the analysis on the critical paths of the system, to provide more accurate and more comprehensive reliability information about the HBT systems compared to the conventional worst-case method.

  5. Reliability study of an emerging fire suppression system

    SciTech Connect

    Miller, David A.; Rossati, Lyric M.; Fritz, Nathan K.; Cournoyer, Michael E.; Granzow, Howard N.

    2015-02-07

    Self-contained fire extinguishers are a robust, reliable and minimally invasive means of fire suppression for gloveboxes. Plutonium gloveboxes are known to present harsh environmental conditions for polymer materials, these include radiation damage and chemical exposure, both of which tend to degrade the lifetime of engineered polymer components. The primary component of interest in self-contained fire extinguishers is the nylon 6-6 machined tube that comprises the main body of the system.Thermo-mechanical modeling and characterization of nylon 6-6 for use in plutonium glovebox applications has been carried out. Data has been generated regarding property degradation leading to poor, or reduced, engineering performance of nylon 6-6 components. In this study, nylon 6-6 tensile specimens conforming to the casing of self-contained fire extinguisher systems have been exposed to hydrochloric, nitric, and sulfuric acids. This information was used to predict the performance of a load bearing engineering component comprised of nylon 6-6 and designed to operate in a consistent manner over a specified time period. The study provides a fundamental understanding of the engineering performance of the fire suppression system and the effects of environmental degradation due to acid exposure on engineering performance. Data generated help identify the limitations of self-contained fire extinguishers. No critical areas of concern for plutonium glovebox applications of nylon 6-6 have been identified when considering exposure to mineral acid.

  6. Reliability study of an emerging fire suppression system

    DOE PAGESBeta

    Miller, David A.; Rossati, Lyric M.; Fritz, Nathan K.; Cournoyer, Michael E.; Granzow, Howard N.

    2015-02-07

    Self-contained fire extinguishers are a robust, reliable and minimally invasive means of fire suppression for gloveboxes. Plutonium gloveboxes are known to present harsh environmental conditions for polymer materials, these include radiation damage and chemical exposure, both of which tend to degrade the lifetime of engineered polymer components. The primary component of interest in self-contained fire extinguishers is the nylon 6-6 machined tube that comprises the main body of the system.Thermo-mechanical modeling and characterization of nylon 6-6 for use in plutonium glovebox applications has been carried out. Data has been generated regarding property degradation leading to poor, or reduced, engineering performancemore » of nylon 6-6 components. In this study, nylon 6-6 tensile specimens conforming to the casing of self-contained fire extinguisher systems have been exposed to hydrochloric, nitric, and sulfuric acids. This information was used to predict the performance of a load bearing engineering component comprised of nylon 6-6 and designed to operate in a consistent manner over a specified time period. The study provides a fundamental understanding of the engineering performance of the fire suppression system and the effects of environmental degradation due to acid exposure on engineering performance. Data generated help identify the limitations of self-contained fire extinguishers. No critical areas of concern for plutonium glovebox applications of nylon 6-6 have been identified when considering exposure to mineral acid.« less

  7. Reliability and coverage analysis of non-repairable fault-tolerant memory systems

    NASA Technical Reports Server (NTRS)

    Cox, G. W.; Carroll, B. D.

    1976-01-01

    A method was developed for the construction of probabilistic state-space models for nonrepairable systems. Models were developed for several systems which achieved reliability improvement by means of error-coding, modularized sparing, massive replication and other fault-tolerant techniques. From the models developed, sets of reliability and coverage equations for the systems were developed. Comparative analyses of the systems were performed using these equation sets. In addition, the effects of varying subunit reliabilities on system reliability and coverage were described. The results of these analyses indicated that a significant gain in system reliability may be achieved by use of combinations of modularized sparing, error coding, and software error control. For sufficiently reliable system subunits, this gain may far exceed the reliability gain achieved by use of massive replication techniques, yet result in a considerable saving in system cost.

  8. Systems Analysis Programs for Hands-On Integrated Reliability Evaluations.

    SciTech Connect

    2014-08-01

    Version 00 The U.S. Nuclear Regulatory Commission (NRC) has developed a powerful personal computer (PC) software application for performing probabilistic risk assessments (PRAs), called Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) Version 8. Using SAPHIRE 8 on a PC, an analyst can perform a PRA for any complex system, facility, or process. Regarding nuclear power plants, SAPHIRE can be used to model a plant's response to initiating events, quantify associated core damage frequencies, and identify important contributors to core damage (Level 1 PRA). It can also be used to evaluate containment failure and release models for severe accident conditions, given that core damage has occurred (Level 2 PRA). It can be used for a PRA assuming that the reactor is at full power, at low power, or at shutdown conditions. Furthermore, it can be used to analyze both internal and external initiating events, and it has special features for transforming models built for internal event analysis to models for external event analysis. It can also be used in a limited manner to quantify risk for release consequences to both the public and the environment (Level 3 PRA). For all of these models, SAPHIRE can evaluate the uncertainty inherent in the probabilistic models. SAPHIRE has evolved with advances in computer technology.

  9. Systems Analysis Programs for Hands-On Integrated Reliability Evaluations.

    Energy Science and Technology Software Center (ESTSC)

    2014-08-01

    Version 00 The U.S. Nuclear Regulatory Commission (NRC) has developed a powerful personal computer (PC) software application for performing probabilistic risk assessments (PRAs), called Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) Version 8. Using SAPHIRE 8 on a PC, an analyst can perform a PRA for any complex system, facility, or process. Regarding nuclear power plants, SAPHIRE can be used to model a plant's response to initiating events, quantify associated core damage frequencies,more » and identify important contributors to core damage (Level 1 PRA). It can also be used to evaluate containment failure and release models for severe accident conditions, given that core damage has occurred (Level 2 PRA). It can be used for a PRA assuming that the reactor is at full power, at low power, or at shutdown conditions. Furthermore, it can be used to analyze both internal and external initiating events, and it has special features for transforming models built for internal event analysis to models for external event analysis. It can also be used in a limited manner to quantify risk for release consequences to both the public and the environment (Level 3 PRA). For all of these models, SAPHIRE can evaluate the uncertainty inherent in the probabilistic models. SAPHIRE has evolved with advances in computer technology.« less

  10. Significant Inter-Test Reliability across Approximate Number System Assessments

    PubMed Central

    DeWind, Nicholas K.; Brannon, Elizabeth M.

    2016-01-01

    The approximate number system (ANS) is the hypothesized cognitive mechanism that allows adults, infants, and animals to enumerate large sets of items approximately. Researchers usually assess the ANS by having subjects compare two sets and indicate which is larger. Accuracy or Weber fraction is taken as an index of the acuity of the system. However, as Clayton et al. (2015) have highlighted, the stimulus parameters used when assessing the ANS vary widely. In particular, the numerical ratio between the pairs, and the way in which non-numerical features are varied often differ radically between studies. Recently, Clayton et al. (2015) found that accuracy measures derived from two commonly used stimulus sets are not significantly correlated. They argue that a lack of inter-test reliability threatens the validity of the ANS construct. Here we apply a recently developed modeling technique to the same data set. The model, by explicitly accounting for the effect of numerical ratio and non-numerical features, produces dependent measures that are less perturbed by stimulus protocol. Contrary to their conclusion we find a significant correlation in Weber fraction across the two stimulus sets. Nevertheless, in agreement with Clayton et al. (2015) we find that different protocols do indeed induce differences in numerical acuity and the degree of influence of non-numerical stimulus features. These findings highlight the need for a systematic investigation of how protocol idiosyncrasies affect ANS assessments. PMID:27014126