11th International Probabilistic Safety Assessment and Management Conference and the Annual European Safety and Reliability Conference 2012, PSAM11 ESREL 2012
Many of the Performance Shaping Factors (PSFs) used in Human Reliability Analysis (HRA) methods are not directly measurable or observable. Methods like SPAR-H require the analyst to assign values for all of the PSFs, regardless of the PSF observability; this introduces subjectivity into the human error probability (HEP) calculation. One method to reduce the subjectivity of HRA estimates is to formally incorporate information about the probability of the PSFs into the methodology for calculating the HEP. This can be accomplished by encoding prior information in a Bayesian Network (BN) and updating the network using available observations. We translated an existing HRA methodology, SPAR-H, into a Bayesian Network to demonstrate the usefulness of the BN framework. We focus on the ability to incorporate prior information about PSF probabilities into the HRA process. This paper discusses how we produced the model by combining information from two sources, and how the BN model can be used to estimate HEPs despite missing observations. Use of the prior information allows HRA analysts to use partial information to estimate HEPs, and to rely on the prior information (from data or cognitive literature) when they are unable to gather information about the state of a particular PSF. The SPAR-H BN model is a starting point for future research activities to create a more robust HRA BN model using data from multiple sources.
Sixty-three years of aero-hydro-elastic loads simulations are demonstrated for a 5 MW offshore wind turbine deployed in shallow water. This large amount of simulation was made possible through the use of a high-performance computing cluster. The resulting one-hour extreme load distributions are examined; the extensive number of one-hour realizations allows for direct estimation of fifty-year return loads, without resorting to extrapolation. This type of simulation study opens up new possibilities for developing wind turbine design standards and discovering physical mechanisms that lead to extreme loads on wind turbine components.
A research project has recently begun to explore the viability of vertical axis wind turbines (VAWT) for future U.S. offshore installations, especially in resource-rich, deep-water locations. VAWTs may offer reductions in cost across multiple categories, including operations and maintenance (O&M), support structure, installation, and electrical infrastructure costs. The cost of energy (COE) reduction opportunities follow from three fundamental characteristics of the VAWT: lower turbine center of gravity, reduced machine complexity, and the opportunity for scaling the machine to very large sizes (10-20 MW). This paper discusses why VAWTs should be considered for offshore installation, describes the project that has been created to explore this prospect, and gives some early results from the project. These results indicate a potential for COE reduction of over 20%.
A research project has recently begun to explore the viability of vertical axis wind turbines (VAWT) for future U.S. offshore installations, especially in resource-rich, deep-water locations. VAWTs may offer reductions in cost across multiple categories, including operations and maintenance (O&M), support structure, installation, and electrical infrastructure costs. The cost of energy (COE) reduction opportunities follow from three fundamental characteristics of the VAWT: lower turbine center of gravity, reduced machine complexity, and the opportunity for scaling the machine to very large sizes (10-20 MW). This paper discusses why VAWTs should be considered for offshore installation, describes the project that has been created to explore this prospect, and gives some early results from the project. These results indicate a potential for COE reduction of over 20%.
ASME 2012 Heat Transfer Summer Conf. Collocated with the ASME 2012 Fluids Engineering Div. Summer Meeting and the ASME 2012 10th Int. Conf. on Nanochannels, Microchannels and Minichannels, HT 2012
22nd Annual International Symposium of the International Council on Systems Engineering, INCOSE 2012 and the 8th Biennial European Systems Engineering Conference 2012, EuSEC 2012
In this paper we present Maestro, a model-based systems engineering (MBSE) environment for design and simulation of complex electronic systems using Orchestra-a simulation tool developed at Sandia National Laboratories. Maestro is deployed as a plugin for MagicDraw and uses Orchestra domain-specific language (DSL) which is based on SysML. Maestro enables a model-based design and analysis approach that replaces the traditional document-based systems engineering process. It provides a unified graphical modeling environment to domain experts who have had to depend on drawing tools for defining system architecture and manual transcription of system topology in creating complex simulation models.
This work develops a new approach for generating stochastic permeability fields from complex three-dimensional fracture networks to support physical and economic performance analyses of enhanced geothermal systems (EGS). The approach represents multiple fracture sets with different dips, orientations, apertures, spacing, and lengths by homogenizing discrete fracture permeabilities onto a regular grid using continuum methods. A previously developed algorithm is used for combining multiple fracture sets at arbitrary orientations into a full anisotropic permeability tensor for every grid block. Fracture properties for each grid cell can either be independently specified or spatially correlated using a variety of probability distributions. The generated stochastic permeability fields are used in mass and heat transport models to represent a variety of complex fracture networks to provide realistic simulations of long-term thermal performance.
The thermal cycling effects as well as isothermal conditions on a conductive multi-walled carbon nanotube (MWCNT) filled latex film are presented and analyzed for a multi-day exposure period. Using a water-based latex solution, multi-walled CNT's have been doped within it and then applied with stencil masked spray deposition to the surface of a non-conductive manufactured substrate. Four-point probe resistivity measurements were conducted in-situ via electrodes deposited across the width of the latex film on the top surface via brush application. The temperature range of consideration was computer controlled using a nitrogen purged environmental chamber cycling between-50 to 80 °C with isothermal holds at each extrema. We have identified long term and short-term temperature-dependent resistivity trends as well as a correlation between environmental conditions and the effect on electrical properties of the nanocomposite.
Damage evaluation for fiber-reinforced polymer composites has been a topic of interest for more than 30 years, and for good reason. With damage modes significantly different than monolithic alloys, engineers have had to design composite structures to tolerate delamination, fiberbreakage, matrix cracking, and fiber-matrix debonding. Accomplishment of this goal has required understanding how and why these damage modes manifest themselves and grow to critical levels, even when the damage is barely visible from the surface. To this end, many nondestructive evaluation techniques have been developed, each with their advantages and disadvantages to characterize these damage forms. In this study, a series of non-destructive evaluation techniques are performed and evaluated on a set of damaged carbon fiber reinforced plastic (CFRP) specimens that have been subjected to varying levels of incident kinetic energy from low velocity impact (LVI). Specifically, 3-D x-ray computed tomography (CT), active thermography, electrical impedance tomography (EIT), and vibrothermography have been systematically utilized for evaluation of the specimens. The advantages and disadvantages are thoroughly explored and reported for each method in order to gain insight into the limitation of each of the damage detection methods and the damage morphology resulting from LVI.
The US Department of Energy Nuclear Criticality Safety Program (NCSP) has supported hands-on criticality safety training at Los Alamos National Laboratory in the past and more recently at Lawrence Livermore National Laboratory. These courses have provided a practical understanding of the processes involved in nuclear criticality through laboratory exercises for a large number of students over many years. The NCSP sponsored the development of an expanded training course for Nuclear Criticality Safety Engineers that includes a one-week session of classroom training to be offered at LANL and two equivalent one-week hands-on training sessions at the critical experiment facility at the Nevada National Security Site and at the critical experiment facility at Sandia National Laboratories (SNL) The class is now being offered as part of the training for Nuclear Criticality Safety Engineers. This paper describes the critical experiment training course offered at SNL.
11th International Probabilistic Safety Assessment and Management Conference and the Annual European Safety and Reliability Conference 2012, PSAM11 ESREL 2012
Various circumstances around the world have resulted in the potential need to store used nuclear fuel longer than times allowed by the regulations. While current storage of used fuel is safe and is likely to remain safe for extended periods of time, material degradation issues may arise that have not necessarily been considered when used fuel storage was licensed for relatively short periods of time. Material degradation issues associated with the fuel, cask internals, storage overpack, closure seals and bolts, and the storage pad all need to be assessed relative to long term performance. Key functional requirements for this long term performance include subcriticality, containment, shielding, thermal performance, and retrievability. A sufficient degree of understanding of the material degradation issues relative to the functional requirements for storage is necessary to develop the technical basis to ensure material performance over extended periods of time. An important initial step in addressing material degradation issues is to identify technical data gaps relative to existing understanding that are important over long storage periods. An effort has been under way since June 2010 to develop a list and prioritization of technical gaps from an international perspective. This effort is being conducted under the aegis of the U.S. Electric Power Research Institute (EPRI) Extended Storage Collaboration Program (ESCP). As part of this program, an International Subcommittee has been established to solicit the international community's input on storage system material degradation issues associated with long term storage and transportation. The first goal of this subcommittee is to develop a report on the technical data gaps from an international perspective. Since used fuel is stored in various configurations around the world, it is expected that different priorities will be identified relative to importance in maintaining the key performance functions. The second goal of the subcommittee is to identify areas for international collaboration for research on degradation issues in order to leverage existing program and facilities. The current status of the international data gap effort is a draft list of High, Medium, and Low priority issues that should be addressed to demonstrate sufficient understanding of material performance of storage system components over extended operational periods. Although there are differences in the identified gaps and associated priorities due to different regulations and storage and transportation systems, there are also areas of commonalities that are important to recognize. These are the areas that have the greatest potential for collaboration.
ASME 2012 Heat Transfer Summer Conf. Collocated with the ASME 2012 Fluids Engineering Div. Summer Meeting and the ASME 2012 10th Int. Conf. on Nanochannels, Microchannels and Minichannels, HT 2012
In this study we report a novel method of dispersing multi-walled carbon nanotubes (MWCNTs) using an electrospinning depositional process onto a conventional, uncured preimpregnated composite material. The main focus is the determination of the process parameters in order to consistently and homogeneously disperse MWCNTs onto a secondary substrate. Due to the exceptional thermal, mechanical, and electrical properties that can be exploited in CNTs, a homogenous dispersion can lead to isotropy in material properties of interest-mechanical, thermal, electrical etc. By combining these materials with structural composite materials, the true spirit of a tailored engineering material can be exploited even further to induce specific properties that are desired for a particular application. Through the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images, as well as vertical scanning interferometry, the resulting electrospun fibers are imaged and correlated with process parameters.
The ACRR at SNL is being considered as a viable alternative for the restart of transient nuclear fuels testing in the US. A full analysis of the capabilities and limitations of the ACRR has been performed to support a comparison of alternatives. Analysis of the ACRR has shown that it is both physically and technically capable of performing nearly all of the potential experiments for future fuels testing. In addition, it is an operating reactor within the DOE complex that has proven to be a valuable asset previously with past fuels testing and in its current mission. Conclusions from the analysis also show that although the ACRR can perform the required duties, there are limitations. Active fuel motion measurement and a hot cell are the two main items lacking at SNL that a transient fuels testing program must take into account if utilizing the ACRR. Overall, the ACRR is an extremely attractive choice for the immediate and near-term restart of transient nuclear fuels testing in the US.
ASME 2012 Heat Transfer Summer Conf. Collocated with the ASME 2012 Fluids Engineering Div. Summer Meeting and the ASME 2012 10th Int. Conf. on Nanochannels, Microchannels and Minichannels, HT 2012
In response to the accident at the Fukushima Daiichi nuclear power station in Japan, the US Nuclear Regulatory Commission and Department of Energy agreed to jointly sponsor an accident reconstruction study as a means of the assessing severe accident modeling capability of the MELCOR code. Objectives of the project included reconstruction of the accident progressions using computer models and accident data, and validation of the MELCOR code and the Fukushima models against plant data.
Establishing design and inspection criteria for impulsively loaded vessels requires a precise understanding of the damage mechanisms and failure modes experienced by the vessels. To that end, Stress Engineering Services, Inc. performed a metallurgical examination of three impulsively loaded vessels that Sandia National Laboratories had intentionally tested to failure, two by impulsive loading and one by hydrotest after impulsive load testing. The vessels were scale models of Type 316 stainless steel vessels use for disposal of chemical ordnance. The examination identified microstructural effects, mechanical damage, and fractographic features associated with exposure to impulsive loads. In particular, the examination identified damage associated with wave interference patterns and unusual patterns of deformation and cracking associated with residual ferrite stringers within the austenitic matrix of the alloy. The characterization of the damage mechanisms leading to failure has direct relevance to ASME design criteria, to the selection of appropriate materials, and to inspection practices for impulsively loaded vessels.
This work develops a new approach for generating stochastic permeability fields from complex three-dimensional fracture networks to support physical and economic performance analyses of enhanced geothermal systems (EGS). The approach represents multiple fracture sets with different dips, orientations, apertures, spacing, and lengths by homogenizing discrete fracture permeabilities onto a regular grid using continuum methods. A previously developed algorithm is used for combining multiple fracture sets at arbitrary orientations into a full anisotropic permeability tensor for every grid block. Fracture properties for each grid cell can either be independently specified or spatially correlated using a variety of probability distributions. The generated stochastic permeability fields are used in mass and heat transport models to represent a variety of complex fracture networks to provide realistic simulations of long-term thermal performance.
Ceramic foams with porosities over 90% are created by drying and sintering particle stabilized oil-water emulsions. This technique is optimized for the creation of magnesium oxide (MgO) porous scaffolds. Processing parameters such as emulsion mixing speed, particle concentration, and drying time are related to final properties such as porosity, permeability, and mechanical strength. The hydroxylation of magnesium oxide to form a gel can also be used to create green ceramics with very low densities directly without the additional steps to form an emulsion. The quality of these ceramic foams compares well to porous ceramics produced by other methods, specifically tape casting of an MgO slip with added poreformers and sponge impregnation of reticulated foam with a slip in a replication process.
We have developed a hands-on criticality experiments class. It is part of the US DOE Nuclear Criticality Safety Program (NCSP) Training and Education Program for Nuclear Criticality Safety Engineers.
In response to the accident at the Fukushima Daiichi nuclear power station in Japan, the US Nuclear Regulatory Commission and Department of Energy agreed to jointly sponsor an accident reconstruction study as a means of the assessing severe accident modeling capability of the MELCOR code. Objectives of the project included reconstruction of the accident progressions using computer models and accident data, and validation of the MELCOR code and the Fukushima models against plant data.
The ACRR at SNL is being considered as a viable alternative for the restart of transient nuclear fuels testing in the US. A full analysis of the capabilities and limitations of the ACRR has been performed to support a comparison of alternatives. Analysis of the ACRR has shown that it is both physically and technically capable of performing nearly all of the potential experiments for future fuels testing. In addition, it is an operating reactor within the DOE complex that has proven to be a valuable asset previously with past fuels testing and in its current mission. Conclusions from the analysis also show that although the ACRR can perform the required duties, there are limitations. Active fuel motion measurement and a hot cell are the two main items lacking at SNL that a transient fuels testing program must take into account if utilizing the ACRR. Overall, the ACRR is an extremely attractive choice for the immediate and near-term restart of transient nuclear fuels testing in the US.
Operations and maintenance costs for offshore wind plants are expected to be significantly higher than the current costs for onshore plants. One way in which these costs may be able to be reduced is through the use of a structural health and prognostic management system as part of a condition based maintenance paradigm with smart load management. To facilitate the creation of such a system a multiscale modeling approach has been developed to identify how the underlying physics of the system are affected by the presence of damage and how these changes manifest themselves in the operational response of a full turbine. The developed methodology was used to investigate the effects of a candidate blade damage feature, a trailing edge disbond, on a 5-MW offshore wind turbine and the measurements that demonstrated the highest sensitivity to the damage were the local pitching moments around the disbond. The multiscale method demonstrated that these changes were caused by a local decrease in the blade's torsional stiffness due to the disbond, which also resulted in changes in the blade's local strain field. Full turbine simulations were also used to demonstrate that derating the turbine power by as little as 5% could extend the fatigue life of a blade by as much as a factor of 3. The integration of the health monitoring information, conceptual repair cost versus damage size information, and this load management methodology provides an initial roadmap for reducing operations and maintenance costs for offshore wind farms while increasing turbine availability and overall profit.
During an urban wide-area incident involving the release of a biological warfare agent, the recovery/restoration effort will require extensive resources and will tax the current capabilities of the government and private contractors. In fact, resources may be so limited that decontamination by facility owners/occupants may become necessary and a simple decontamination process and material should be available for this use. One potential process for use by facility owners/occupants would be a liquid sporicidal decontaminant, such as pHamended bleach or activated-peroxide, and simple application devices. While pH-amended bleach is currently the recommended low-tech decontamination solution, a less corrosive and toxic decontaminant is desirable. The objective of this project is to provide an operational assessment of an alternative to chlorine bleach for low-tech decontamination applications activated hydrogen peroxide. This report provides the methods and results for activatedperoxide evaluation experiments. The results suggest that the efficacy of an activated-peroxide decontaminant is similar to pH-amended bleach on many common materials.
This report investigates strategies to mitigate anticipated wind energy curtailment on Maui, with a focus on grid-level energy storage technology. The study team developed an hourly production cost model of the Maui Electric Company (MECO) system, with an expected 72 MW of wind generation and 15 MW of distributed photovoltaic (PV) generation in 2015, and used this model to investigate strategies that mitigate wind energy curtailment. It was found that storage projects can reduce both wind curtailment and the annual cost of producing power, and can do so in a cost-effective manner. Most of the savings achieved in these scenarios are not from replacing constant-cost diesel-fired generation with wind generation. Instead, the savings are achieved by the more efficient operation of the conventional units of the system. Using additional storage for spinning reserve enables the system to decrease the amount of spinning reserve provided by single-cycle units. This decreases the amount of generation from these units, which are often operated at their least efficient point (at minimum load). At the same time, the amount of spinning reserve from the efficient combined-cycle units also decreases, allowing these units to operate at higher, more efficient levels.
Energy management in a commercial facility can be segregated into two areas: energy efficiency and demand response (DR). Energy efficiency focuses on steady-state load minimization. Demand response reduces load for event driven periods during the peak load. Demand response driven changes in electricity use are designed to be short-term in nature, centered on critical hours during the day when demand is high or, utilized when the electricity supplier's reserve margins are low. Due to the recent Federal Energy Regulatory Commission (FERC) Order 745, Demand Response Compensation in Organized Wholesale Energy Markets, the potential annual compensation to Sandia National Laboratories (SNL) from performing DR ranges from $\$$200K to $\$$1,800K. While the current energy supply contract does not offer any compensation for participating in DR, there is benefit in understanding the issues and potential value in performing a DR event. This Report will be helpful in upcoming energy supply contract negotiations to quantify the energy savings and power reduction potential from DR at SNL. On August 25, 2011 and August 9, 2012 the Facilities Management and Operations Center (FMOC) performed the first and second DR pilot events at SNL/NM. This report describes the details and results of these DR events.
Most photovoltaic (PV) performance models currently available are designed to use irradiance and weather data and predict PV system output using a module or array performance model and an inverter model. While these models can give accurate results, they do so for an idealized system. That is, a system that does not experience component failures or outages. We have developed the Photovoltaic Reliability and Performance Model (PV-RPM) to more accurately model these PV systems by including a reliability component that simulates failures and repairs of the components of the system, as well as allow for the disruption of the system by external events such as lightning or grid disturbances. In addition, a financial component has also been included to help assess the profitability of a PV system. In this report we provide some example analyses of three different PV system designs using the PV-RPM.
Spontaneous Raman spectra for important hydrocarbon fuels and combustion intermediates were recorded over a range of low-to-moderate flame temperatures using the multiscalar measurement facility located at Sandia/CA. Recorded spectra were extrapolated to higher flame temperatures and then converted into empirical spectral libraries that can readily be incorporated into existing post-processing analysis models that account for crosstalk from overlapping hydrocarbon channel signal. Performance testing of the developed libraries and reduction methods was conducted through an examination of results from well-characterized laminar reference flames, and was found to provide good agreement. The diagnostic development allows for temporally and spatially resolved flame measurements of speciated hydrocarbon concentrations whose parent is more chemically complex than methane. Such data are needed to validate increasingly complex flame simulations.