Quantitative Risk Analysis of Hydrogen Events at WTP: Part 1 of 2 — The Operational Frequency Analysis Model

2012 ◽  
Author(s):  
C. Ray Lux ◽  
Kevin R. O’Kula ◽  
Michael G. Wentink ◽  
Ryan E. Jones ◽  
Jean E. Collin ◽  
...  
Keyword(s):  
Risk Analysis ◽  
Frequency Analysis ◽  
Chemical Industry ◽  
Fault Tree ◽  
Piping System ◽  
Hanford Site ◽  
Quantitative Risk Analysis ◽  
Piping Systems ◽  
Operational Frequency ◽  
Pocket Formation

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

2012 ◽  
Author(s):  
Ryan E. Jones ◽  
Jean E. Collin ◽  
David J. Gross ◽  
Michael G. Wentink ◽  
Kevin O’Kula
Keyword(s):  
Risk Analysis ◽  
Human Error ◽  
Waste Treatment ◽  
Mitigation Strategies ◽  
Normal System ◽  
Event Analysis ◽  
Quantitative Risk Analysis ◽  
Plant Operations ◽  
Hydrogen Ignition ◽  
Operational Frequency

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.

Quantitative assessment of risks on construction projects using fault tree analysis with hybrid uncertainties

2019 ◽  
Vol 19 (1) ◽  
pp. 48-70 ◽  
Author(s):  
Shahab Shoar ◽  
Farnad Nasirzadeh ◽  
Hamid Reza Zarandi
Keyword(s):  
Risk Analysis ◽  
Uncertainty Analysis ◽  
Fuzzy Set ◽  
Fault Tree ◽  
Analysis Method ◽  
Content Type ◽  
Quantitative Risk Analysis ◽  
Probability Of Occurrence ◽  
Hybrid Uncertainty ◽  
The Impact

Purpose The purpose of this paper is to present a fault tree (FT)-based approach for quantitative risk analysis in the construction industry that can take into account both objective and subjective uncertainties. Design/methodology/approach In this research, the identified basic events (BEs) are first categorized based on the availability of historical data into probabilistic and possibilistic. The probabilistic and possibilistic events are represented by probability distributions and fuzzy numbers, respectively. Hybrid uncertainty analysis is then performed through a combination of Monte Carlo simulation and fuzzy set theory. The probability of occurrence of the top event is finally calculated using the proposed FT-based hybrid uncertainty analysis method. Findings The efficiency of the proposed method is demonstrated by implementing in a real steel structure project. A quantitative risk assessment is performed for weld cracks, taking into account of both types of uncertainties. An importance analysis is finally performed to evaluate the contribution of each BE to the probability of occurrence of weld cracks and adopt appropriate response strategies. Research limitations/implications In this research, the impact of objective (aleatory) dependence between the occurrences of different BEs and subjective (epistemic) dependence between estimates of the epistemically uncertain probabilities of some BEs are not considered. Moreover, there exist limitations to the application of fuzzy set rules, which were used for aggregating experts’ opinions and ranking purposes of the BEs in the FT model. These limitations can be investigated through further research. Originality/value It is believed that the proposed hybrid uncertainty analysis method presents a robust and powerful tool for quantitative risk analysis, as both types of uncertainties are taken into account appropriately.

Non-Linear Design Verification of Nuclear Power Piping According to ASME III NB/NC

2008 ◽  
Author(s):  
Lingfu Zeng ◽  
Lennart G. Jansson
Keyword(s):  
Nuclear Power ◽  
Design Evaluation ◽  
Piping System ◽  
Design Verification ◽  
Intensive Study ◽  
Non Linear ◽  
Piping Systems ◽  
Design Requirements

A nuclear piping system which is found to be disqualified, i.e. overstressed, in design evaluation in accordance with ASME III, can still be qualified if further non-linear design requirements can be satisfied in refined non-linear analyses in which material plasticity and other non-linear conditions are taken into account. This paper attempts first to categorize the design verification according to ASME III into the linear design and non-linear design verifications. Thereafter, the corresponding design requirements, in particular, those non-linear design requirements, are reviewed and examined in detail. The emphasis is placed on our view on several formulations and design requirements in ASME III when applied to nuclear power piping systems that are currently under intensive study in Sweden.

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane, and Mixed Mode Bending Under Seismic Load: An Experimental Approach

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Dynamic Behavior ◽  
Failure Modes ◽  
Seismic Load ◽  
Piping System ◽  
Shake Table ◽  
Shake Table Tests ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Plane Bending

Pressurized piping systems used for an extended period may develop degradations such as wall thinning or cracks due to aging. It is important to estimate the effects of degradation on the dynamic behavior and to ascertain the failure modes and remaining strength of the piping systems with degradation through experiments and analyses to ensure the seismic safety of degraded piping systems under destructive seismic events. In order to investigate the influence of degradation on the dynamic behavior and failure modes of piping systems with local wall thinning, shake table tests using 3D piping system models were conducted. About 50% full circumferential wall thinning at elbows was considered in the test. Three types of models were used in the shake table tests. The difference of the models was the applied bending direction to the thinned-wall elbow. The bending direction considered in the tests was either of the in-plane bending, out-of-plane bending, or mixed bending of the in-plane and out-of-plane. These models were excited under the same input acceleration until failure occurred. Through these tests, the vibration characteristic and failure modes of the piping models with wall thinning under seismic load were obtained. The test results showed that the out-of-plane bending is not significant for a sound elbow, but should be considered for a thinned-wall elbow, because the life of the piping models with wall thinning subjected to out-of-plane bending may reduce significantly.

scholarly journals City Fire Risk Analysis based on Coupling Fault Tree Method and Triangle Fuzzy Theory

2014 ◽  
Vol 84 ◽  
pp. 204-212 ◽  
Author(s):  
Wu Aiyou ◽  
Shi Shiliang ◽  
Li Runqiu ◽  
Tang Deming ◽  
Tang Xiafang
Keyword(s):  
Risk Analysis ◽  
Fuzzy Theory ◽  
Fault Tree ◽  
Fire Risk ◽  
Fire Risk Analysis ◽  
Coupling Fault ◽  
Tree Method

scholarly journals Quantitative Risk Analysis for N-Methyl Pyrrolidone Using Physiologically Based Pharmacokinetic and Benchmark Dose Modeling

2009 ◽  
Vol 113 (2) ◽  
pp. 468-482 ◽  
Author(s):  
Torka S. Poet ◽  
Chris R. Kirman ◽  
Michael Bader ◽  
Christoph van Thriel ◽  
Michael L. Gargas ◽  
...  
Keyword(s):  
Risk Analysis ◽  
Benchmark Dose ◽  
Quantitative Risk Analysis ◽  
Physiologically Based Pharmacokinetic ◽  
Physiologically Based ◽  
Methyl Pyrrolidone

The Influence of Support Hardware and Piping System Seismic Response on Snubber Support Damping

1997 ◽  
Vol 119 (4) ◽  
pp. 451-456 ◽  
Author(s):  
C. Lay ◽  
O. A. Abu-Yasein ◽  
M. A. Pickett ◽  
J. Madia ◽  
S. K. Sinha
Keyword(s):  
Seismic Response ◽  
Fundamental Frequency ◽  
Damping Ratio ◽  
Damping Coefficient ◽  
Piping System ◽  
Nodal Displacement ◽  
Damping Coefficients ◽  
Fundamental Frequencies ◽  
Piping Systems

The damping coefficients and ratios of piping system snubber supports were found to vary logarithmically with pipe support nodal displacement. For piping systems with fundamental frequencies in the range of 0.6 to 6.6 Hz, the support damping ratio for snubber supports was found to increase with increasing fundamental frequency. For 3-kip snubbers, damping coefficient and damping ratio decreased logarithmically with nodal displacement, indicating that the 3-kip snubbers studied behaved essentially as coulomb dampers; while for the 10-kip snubbers studied, damping coefficient and damping ratio increased logarithmically with nodal displacement.

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