bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative Risk Analysis of Hydrogen Events at WTP: Part 1 of 2 — The Operational Frequency Analysis Model
Authors: Lux C. Ray , O’Kula Kevin R. , Wentink Michael G. , Jones Ryan E. , Collin Jean E. , Gross David J. 
Published: August 2013

A Quantitative Risk Analysis (QRA) model has been developed to determine the frequency and severity (potential combustion loads) of postulated hydrogen event types in piping systems and proposed as a design-informing tool for the U.S. Department of Energy’s (DOE) Hanford Tank Waste Treatment and Immobilization Plant (WTP) at the Hanford Site near Richland, Washington. Specifically, the QRA provides a systematic, comprehensive methodology for assessing hydrogen events, including deflagrations, detonations, and deflagration-to-detonation transition (DDT) types in piping systems containing legacy nuclear waste streams being processed for vitrification. The events considered include normal operations as well as postulated upset conditions as a result of internal and external accidents. The QRA approach incorporates three sequential phases, including Operational Frequency Analysis (OFA), Gas Pocket Formation (GPF) and Event Progression Logic (EPL) models in the form of an integrated logic framework. The WTP piping design will be evaluated on a specific piping route basis using a probabilistic sampling approach, with the QRA providing the quantitative dynamic loads for evaluation according to the frequency and type of hydrogen event.
The OFA is based on an industry standard fault tree computer model, CAFTA, and analyzes the frequency of combustible gas pocket formation in a piping system from three primary sources: (1) normal operations; (2) piping system-specific upset conditions affecting transfer operations; and (3) plant-wide initiating events such as fire and seismic accidents. A second output from the OFA is duration time for each event, quantifying the length of time that a gas pocket is likely to develop before the initiating event is terminated, with the information provided directly to QRA event tree models for assessing gas pocket growth. A team of safety, operations and engineering, developed the underlying logic of the fault tree model with the overall modeling approach following applicable nuclear/chemical industry guidance and standards for performing QRA applications. Primary inputs to the OFA module are initiating event, equipment reliability, and human/operator error data and their characteristic distributions, and are drawn from Hanford Site safety documentation, government and commercial sector sources, and related nuclear/chemical industry experience. This paper discusses the overall OFA module, its inputs, the outputs to the GPF and EPL modules, the relative importance of different initiating event conditions, key insights obtained to date, upcoming supporting uncertainty/sensitivity analyses, and summarizes technical peer review assessments.
Quantitative Risk Analysis of Hydrogen Events at WTP: Part 2 of 2 — Development of Event Frequency-Severity Model
Authors: Jones Ryan E. , Collin Jean E. , Gross David J. , Wentink Michael G. , O’Kula Kevin 
Published: August 2013

In late 2008, a Hydrogen in Piping and Ancillary Vessels (HPAV) Assessment Team was chartered by the U.S. Department of Energy’s (DOE) Office of River Protection (DOE-ORP) to investigate the extent of operational complexity in the Hanford Tank Waste Treatment and Immobilization Plant (WTP) due to conservatisms in hydrogen event analysis methodology and related design constraints. The HPAV Assessment Team recommended that a Quantitative Risk Analysis (QRA) be performed to analyze normal plant operating and upset conditions that can lead to accumulation of hydrogen in piping, and determine the frequency and severity of ensuing postulated hydrogen events such that WTP can make risk-informed decisions regarding hydrogen event mitigation strategies and improve operational flexibility.
The QRA application is based on an in-depth review of hydrogen event-affected systems conducted by an interdisciplinary team of system engineers, process engineers, plant operations modelers, operators, and safety personnel to ensure facility ownership of the overall process. The QRA evaluates hydrogen event-affected systems for both normal system operations and possible upset conditions as a result of internal and external events (including human error). The Operational Frequency Analysis (OFA) and Event Progression Logic (EPL) analysis provide an integrated framework for the analysis of initiating events from which hydrogen accumulation can occur and the quantitative analysis of the physical progression of ensuing hydrogen ignition events. The purpose of this paper is to describe the QRA methodology, models, and testing used to quantify the system demand resulting from postulated hydrogen event types, frequencies, and severities, with emphasis on the latter stages of the QRA, overall execution and application.
Vibration Characteristics of a Perforated Plate Immersed in Fluid
Authors: Ito Tomohiro , Shintani Atsuhiko , Nakagawa Chihiro 
Published: August 2013

Perforated plates are used in many mechanical structures in thermal power plants, nuclear power plants, or chemical plants etc. Cylindrical structures made by the perforated plates are also found in many places. However, vibration characteristics of the structures made by perforated plates are not fully clarified, especially for the structures immersed in liquid. The stiffness of the structures becomes smaller than that of ones made by simple plates with no holes, while the mass of the structures also becomes smaller. According to the balance between the stiffness reduction and mass reduction, natural frequencies will be decided. Moreover, added mass and added damping effects are very large in liquid, and are thought to largely change due to holes.
In this study, as a fundamental step, a perforated plate is treated. The vibration characteristics such as natural frequency and damping ratio are studied for various hole numbers or various opening ratios by both numerical simulations and simple test models. Vibration tests are conducted in liquid as well as in air.
Power Spectral Density Analysis of Acoustically Induced Vibration in Piping Systems
Authors: Dweib Ahmed H. 
Published: August 2013

Acoustically induced vibration near points of large pressure reduction in piping systems can cause fatigue failure of the piping material at points of discontinuity.
Empirical design curves have been used extensively for the assessment of acoustic fatigue risk level in piping systems. Subsequent development in the field resulted in the application of more detailed methods of analysis including, displacement-based and energy-based Finite Element Analysis (FEA) and Statistical Energy Analysis (SEA).
Displacement-based FEA, which provides deterministic approach for the detailed analysis of the vibration response, is suitable for low and intermediate frequency range where the dynamic stresses in the pipe wall can be determined with reasonable certainty.
For large complicated systems and high frequency range, the deterministic FEA becomes impractical due to the large number of mode shapes involved and the sensitivity of the results to small changes in system parameters. In these cases, the results of the FEA can have only a statistical value and SEA methods, which are based on statistical approach in contrast to deterministic approach, become more effective. SEA methods require accurate estimation of energy coupling parameters, on which the validity of the methods is dependent.
In this paper, energy-based FEA is utilized for the evaluation of the system response and the SEA parameters. Power Spectral Density (PSD) analysis is performed for finite element model of a system consisting of pipe and acoustic fluid. The system is subjected to acoustically induced vibration through the input of acoustic energy at the downstream of a pressure-reducing valve. The system response is obtained and the parameters required for SEA, including the coupling power factor, are estimated.
Study on the Stress-Strain Redistribution Caused by Inelastic Deformation in Perforated Plate
Authors: Ikeda Sho , Sato Masakazu , Kasahara Naoto 
Published: August 2013

Fast Breeder Reactors and chemical plants that is operated at elevated temperature must be designed considering creep deformation in addition to elastic-plastic deformation. Especially at structural discontinuities, strain concentration induced by stress-strain redistribution reduces creep-fatigue strength. For this reason, a design method is needed for appropriately evaluating inelastic behavior at a structural discontinuity. As one of simplified methods with elastic analysis, a rational method with Stress Redistribution Locus (SRL) has been studied during recent years. Previous studies have shown that SRL does not depend on constitutive equations or on the magnitude of loading. And through the elastic-plastic-creep analysis of a one-dimensional pipe model, it was revealed that there was a relation between stress-strain redistribution and the size of elastic core.
The purpose of this study is to clarify the mechanism of stress-strain redistribution in complex structures like actual components. Multi-dimensional stress-strain distribution and multiaxial stress occur in those structures. For considering those effects, inelastic analyses on perforated plate were performed and the relation between the region of elastic cores and SRL was examined. Then, it was revealed that SRL could be divided into two parts. One half is affected by the region of elastic core and the other half depends on the loading type. Furthermore, this paper proposes the new SRL method based on the mechanism and validates the method.
STYLE: Comparison of Engineering Assessment Methods
Authors: Lauerova Dana , Sharples John 
Published: August 2013

The paper presents results of a sub-task of the STYLE project currently running within the 7th Framework EU programme by way of an overview of deterministic engineering assessment methods (EAM) used for evaluation of flawed nuclear plant components, as used in various European countries (Germany, France, UK, Netherlands, Czech Republic, Spain, Finland and Sweden).
Within STYLE, several mock-up experiments are being performed on specimens containing structural features. Structural features being considered include (1) dissimilar metal welds, (2) repair welds, and (3) austenitic cladding on a ferritic pipe. The overview thus focuses on the evaluation of flaws contained within each of these three types of features.
Information on the procedures and codes applied in the various countries are given: KTA standard, ASME Code in Germany; ZG Appendix of RCC-M, A16 Appendix of RCC-MRx, and App. 5.4–5.6 of RSE-M in France; R6 in the UK; BS7910, R6 in the Netherlands; VERLIFE, ASME Code in the Czech Republic; ASME Code in Spain; SSM Handbook, ASME Code in Finland; and SSM Handbook, ASME Code, ProSACC in Sweden.
An overview and brief description of the different methods is included in the paper, highlighting the commonalities and differences among the various approaches.
Design and Development of Pressure Vessel for Improvement of Manufacturing Rice-Powder Efficiency Using Underwater Shock Wave
Authors: Naha Kazuyuki , Shimojima Ken , Miyafuji Yoshitaka , Itoh Shigeru 
Published: August 2013

The rice-powder paid to attention in Japan, because the various food made by rice-powder. But, conventional method of manufacturing rice-powder generates heat when crushing of rice. One the other hand, the pressure vessel of oval structure for manufactured rice-powder using underwater shock wave has been developed in Okinawa National College of Technology. The merits of this system manufacture rice-powder without heating.
But, the efficiency of this system is low. Therefore, in this paper, we propose new design of pressure vessel for the highly effective rice-powder manufacturing. To design a new pressure vessel, it is clear that the performance of the oval structure pressure vessel. And, we design and manufacturing new pressure vessel for the highly effective rice-powder manufacturing.
Effects of Simulation Parameters on Residual Stresses of Inconel Alloy 600 in Finite Element Laser Shock Peening Analysis
Authors: Kim Ju Hee , Kim Ji Soo , Kim Yun Jae , Bae Hong Yeol , Kim Joung Soo 
Published: August 2013

Laser shock peening (LSP) is an innovative surface treatment technique, which is successfully applied to improve fatigue performance of metallic components. After the treatment, the fatigue strength and fatigue life of a metallic material can be increased remarkably owing to the presence of compressive residual stresses in the material. Recently, the incidences of cracking in Alloy 600 small-caliber penetration nozzles (CRDM (control rod drive mechanism) and BMI (bottom mounted instrument)) have increased significantly. The cracking mechanism has been attributed to primary water stress corrosion cracking (PWSCC) and has been shown to be driven by welding residual stresses and operational stresses in the weld region. For this reason, to mitigating weld residual stress, preventive maintenance of BMI nozzles was considered application of laser shock peening process.
The present study is to predict the residual stresses distribution along the peening surface and the interior of the target (Inconel alloy 600 steel) induced by single and multiple LSP processes using the finite element method. The simulations were accomplished using a commercial finite element package ABAQUS, employing both explicit and implicit methodologies. Effects of parameters related to finite element simulation of laser shock peening process to determine compressive residual stresses of Inconel alloy 600 steel are discussed, in particular parameters associated with the LSP process, such as the maximum pressure, pressure pulse duration, laser spot size and number of shots.
It is found that about 2HEL maximum pressure and a certain range of the pulse duration can produce maximum compressive residual stresses near the surface, and thus proper choices of these parameters are important. But plastically affected depth increase with increasing maximum pressure and pulse duration. For the laser spot size, residual stresses are not affected, provided it is larger than a certain size. Magnitudes of the compressive residual stresses and plastically affected depth are found to increase with increasing number of shots, but the effect is less pronounced for more shots. Thus, the amplitude of the initial tensile residual stresses was remarkably changed by LSP. Additionally, In order to evaluate the influence of initial residual stresses in Inconel alloy 600 steel, the initial condition option was employed in the finite element code.
Experimental Study on Free Standing Rack Loading Full Fuel Assembly
Authors: Iwasaki Akihisa , Nekomoto Yoshitsugu , Morita Hideyuki , Taniguchi Katsuhiko , Okuno Daisaku , Matsuoka Toshihiro , Chigusa Naoki 
Published: August 2013

The spent fuel storage rack of a nuclear plant stores the spent fuel temporarily before it can be moved to a reprocessing facility. Therefore, the spent fuel storage rack must have a high tolerance against large seismic loads. So, the free standing rack is developed in Japan as other countries. The free standing rack structure incorporates the effect of the friction force on the spent fuel pool floor, and the fluid effect.
Under earthquake condition, the free standing rack sliding and rocking motions are induced and the spent fuels rattle in the cells.
In this paper, sliding and rocking motions of full-scale rack model having full loading fuel assembly subjected to the seismic excitation are studied. To develop an analysis evaluation method for rack motions, we carried out seismic test of a full-scale rack model using a shaking table, and obtained the fundamental data about the free standing rack.
Experimental Parameter Study on Free Standing Rack
Authors: Iwasaki Akihisa , Nekomoto Yoshitsugu , Morita Hideyuki , Taniguchi Katsuhiko , Okuno Daisaku , Matsuoka Toshihiro , Chigusa Naoki 
Published: August 2013

The spent fuel rack of a nuclear plant stores the spent fuel temporarily before it can be moved to a reprocessing facility. Therefore, the spent fuel rack must have a high tolerance against big seismic loads. Sliding and rocking motions of full-scale rack model having full loading fuel assembly subjected to the seismic excitation are studied [1]. We carried out the seismic test of the free standing rack under some conditions. The distribution of the fuel assembly affects the sliding and rocking motions of the rack, and the outer plate reduces the rack response level by fluid effect. We made sure of them by seismic experiment using a shaking table.
In this paper, sliding and rocking motions of full-scale rack model under some conditions are studied. To develop an analysis evaluation method of the rack sliding and rocking motions, we obtained the fundamental data about the free standing rack by seismic test using a shaking table.
A Basis for Selecting the Most Appropriate Small Specimen Creep Test Type
Authors: Hyde T. H. , Hyde C. J. , Sun W. 
Published: August 2013

Many components in conventional and nuclear power plant, aero-engines, chemical plant etc, operate at temperatures which are high enough for creep to occur. These include plain pipes, pipe bends, branched pipes etc; the manufacture of such components may also require welds to be inserted in them. In most cases, only nominal operating conditions (i.e. pressure, temperatures, system load etc) are known and hence precise life predictions are not possible. Also, the proportion of life consumed will vary from position to position within a component and the plant. Hence, non-destructive techniques are adopted to assist in making decisions on whether to repair, continue operating or scrap certain components. One such approach is to use scoop samples removed from the components to make small creep test specimens, i.e., sub-size uniaxial creep test specimens, impression creep test specimens, small punch creep test specimens and small ring creep test specimens.
Each specimen type has its own unique advantages and disadvantages and it may not be obvious which one is the most appropriate test method to use. This paper gives a brief description of each specimen and associated test type and describes their practical limitations. The suitability of each of the methods for determining “bulk” material properties is described and it is shown that an appropriate test type can be chosen.
R6 V and Proposed Vg Plasticity Correction Terms for Combined Loading Applied to Experiments
Authors: James Peter , Madew Colin 
Published: August 2013

Engineering components may contain small crack-like defects that experience combinations of primary and secondary stresses during service. A new formalism of the R6 V factor, Vg, has been introduced over previous years to quantify the influence of plasticity interaction under combined primary and secondary loading based upon such defects within a large range of finite element analyses.
The aim of this paper is provide experimental validation to the Vg approach such that it satisfies validation requirements for potential inclusion to R6. Estimates of failure from implementing Vg, as well as the R6 V approach, to experiments available from literature are presented. These experiments include plate tests subjected to weld residual stresses, cylinders subjected to thermal shock conditions and pre-compressed laboratory specimens. This range of specimens covers those considered in validation of the existing approaches in R6 and some more recent experiments.
When applying the existing R6 V and the Vg plasticity interaction parameters the accuracy of the methods diverges with increasing plasticity; with the Vg approach providing the more accurate result at intermediate and high levels of Lr (i.e. beyond Lr = 0.7). However, since both the existing R6 and the Vg plasticity interaction parameters are conservative the experiments provide useful validation to both methods.
“First Estimate” Plastic Collapse Solutions for Flat and Torispherical Ended Pressure Vessels Subjected to Extensive Corrosion Wall Thinning
Authors: Madew Colin , Wilkes Mark , Charles Richard , Symington Ian 
Published: August 2013

Plants in safety-critical industries comprise of a number of different components, including various sizes of pressure vessels, and their integrity is often paramount to the safe running of the plant. In many cases these vessels can contain highly corrosive liquids, which, over time can lead to a degree of thinning in the vessel walls. With corrosion wall-thinning come a number of issues, including a reduced plastic collapse load of the vessel and possible fatigue initiation from corrosion pits. Since failure of these vessels could lead to catastrophic failure and the escape of highly corrosive material, the assessment and maintenance of these vessels is of high importance.
Current Fitness for Service Codes and Standards provide guidance on the assessment of cylinders and pipes with localized wall thinning and general corrosion, with respect to plastic collapse. This guidance, however, is not currently applicable to components with geometric discontinuities (the pressure vessel base-wall junction).
This paper follows a preceding paper presented at the ASME PVP Conference 2010 which derived “First Estimate” plastic collapse solutions for flat-based, corroded, pressure vessels. These solutions have been expanded through further finite element studies to accommodate the estimation of plastic collapse in tori-spherical headed pressure vessels subjected to extensive corrosion wall-thinning. Results from this study are presented in graphical form to enable a quick and efficient first estimate of the effect of wall thinning on the collapse pressure to be attained.
Hydro-Abrasive Wear Damage at Reactor Recirculation Pump Bearing Journals
Authors: Engel Robert , Fibier André , Heldt Jens , Ronecker Andreas 
Published: August 2013

During the refueling and maintenance outage in August 2011 at Leibstadt Nuclear Power Plant in Switzerland, the inspection of the hydrostatic bearings of the two identical recirculation pumps revealed a deep circumferential erosion groove on the inside surface of each of the bearing journals. The bearing journals are made of austenitic stainless steel. The cylindrical journal is welded to the back shroud of the impeller and surrounds the internal stationary heat exchanger of the pump by forming a narrow fluid filled annulus. The location of material removal was the same as in the year 2004 when similar wear damage was fixed by build-up welding.
The plant decided to repair the damage during the subsequent outage in 2012. However, the Swiss Federal Nuclear Safety Inspectorate in return required the plant to identify the precise erosion mechanism, to ensure the structural integrity of the journals by taking into account the rate of material removal from 2004 up to the 2012 outage, and to include provisions for the early detection of a journal failure.
This paper summarizes the previous as well as the latest results of different inspections, investigations, evaluations, and analyses done to meet the requirements of the Swiss regulatory authority. The results show that, from a safety-related and an operational availability perspective, it is acceptable not to repair the damaged bearing journals prior to the 2012 outage.