Effects of Flaw Sizing Errors on the Reliability of Vessels and Piping

1998 ◽  
Vol 120 (4) ◽  
pp. 365-373 ◽  
Author(s):  
F. A. Simonen ◽  
M. A. Khaleel
Keyword(s):  
Detection Probability ◽  
Flaw Detection ◽  
Probability Of Detection ◽  
Limiting Factor ◽  
Numerical Implementation ◽  
Detection Capability ◽  
Acceptance Criteria ◽  
Flaw Sizing ◽  
Detection Capabilities ◽  
Flaw Detection Probability

This paper describes probabilistic fracture mechanics calculations that simulate fatigue crack growth, flaw detection, flaw sizing accuracy, and the impacts of flaw acceptance criteria. The numerical implementation of the model is based on a Latin hypercube approach. Calculations have been performed for a range of parameters. For representative values of flaw detection probability, flaw sizing errors, and flaw acceptance criteria, detection capability is the most limiting factor with regard to the ability of the inservice inspections to reduce leak probabilities. However, gross sizing errors or significant relaxations of current flaw acceptance standards could negate the benefits of outstanding probability of detection capabilities.

Cumulative Detection Probability as a Basis for Pressure Vessel Inspection Intervals

1995 ◽  
Vol 117 (4) ◽  
pp. 399-403 ◽  
Author(s):  
G. Garic
Keyword(s):  
Fracture Mechanics ◽  
Pressure Vessel ◽  
Detection Probability ◽  
Flaw Detection ◽  
Probability Of Detection ◽  
Acceptable Level ◽  
Cumulative Probability ◽  
Failure Risk ◽  
Flaw Detection Probability

This work discusses use of the cumulative flaw detection probability as the basis for establishing pressure vessel inspection intervals. The method is based on the accumulated probability of detecting a flaw over several inspections. It explicitly incorporates a user decision as to the acceptable level of failure risk. A four-step approach is outlined including fracture mechanics flaw growth calculations with probabilistic treatment of detection probability. It is concluded that (a) inspection intervals based on the cumulative probability of detection provide significant advantages over traditional cycle-based methods, (b) pressure vessel recertification inspections should rely on high percentage inspections conducted on a relatively infrequent basis.

Reliability Assessment of Piping in a Nuclear Power Plant Considering Flaw Detection Probability

2004 ◽  
Author(s):  
Hideo Machida ◽  
Norimichi Yamashita ◽  
Shinobu Yoshimura ◽  
Genki Yagawa
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Detection Probability ◽  
Nuclear Power ◽  
Power Plants ◽  
Plant Stress ◽  
Flaw Detection ◽  
Reliability Assessment ◽  
Flaw Detection Probability

This study was performed to clarify the effects of flaw detection probability on piping reliability of a nuclear power plant. Stress-corrosion cracking (SCC) is still sporadically detected in austenitic stainless steel piping in Japanese BWR plants. The suitability for continued service of cracked pipes is basically evaluated by using the “Rules on fitness -for service for nuclear power plants.” Here future inspection rules are employed. However, the possibility of undetection of existing cracks and that of inaccurate measurements cannot be eliminated in UT-based inspection. Thus a probabilistic fracture mechanics (PFM) analysis was carried out referring measured flaw size, and the reliability of piping was evaluated considering the possibility of undetection of existing cracks and that of inaccurate measurements. The results of the analysis indicate that, if the interval and quality of the inspection are maintained at a certain specified level, the possibility of undetection of existing cracks and that of inaccurate measurements less affect failure probability.

scholarly journals Evaluating the Probability of Detection Capability of Permanently Installed Sensors Using a Structural Integrity Informed Approach

2021 ◽  
Vol 40 (3) ◽  
Author(s):  
Michael Siu Hey Leung ◽  
Joseph Corcoran
Keyword(s):  
Structural Integrity ◽  
Real Life ◽  
Probability Of Detection ◽  
Field Of View ◽  
Probabilistic Framework ◽  
Detection Capability ◽  
Damage Location ◽  
Detection Capabilities ◽  
Integrity Assessments ◽  
System Designs

AbstractThere is a growing interest in using permanently installed sensors to monitor for defects in engineering components; the ability to collect real-time measurements is valuable when evaluating the structural integrity of the monitored component. However, a challenge in evaluating the detection capabilities of a permanently installed sensor arises from its fixed location and finite field-of-view, combined with the uncertainty in damage location. A probabilistic framework for evaluating the detection capabilities of a permanently installed sensor is thus proposed. By combining the spatial maps of sensor sensitivity obtained from model-assisted methods and probability of defect location obtained from structural mechanics, the expectation and confidence in the probability of detection (POD) can be estimated. The framework is demonstrated with four sensor-component combinations, and the results show the ability of the framework to characterise the detection capability of permanently installed sensors and quantify its performance with metrics such as the $${\mathrm{a}}_{90|95}$$ a 90 | 95 value (the defect size where there is 95% confidence of obtaining at least 90% POD), which is valuable for structural integrity assessments as a metric for the largest defect that may be present and undetected. The framework is thus valuable for optimising and qualifying monitoring system designs in real-life engineering applications.

Sensitivity Study on the Effects of Nondestructive Examinations on Failure Probabilities of Reactor Pressure Vessels

2018 ◽  
Author(s):  
Kensaku Arai ◽  
Jinya Katsuyama ◽  
Yinsheng Li
Keyword(s):  
Power Plants ◽  
Flaw Detection ◽  
Sensitivity Study ◽  
Pressure Vessels ◽  
Probability Of Detection ◽  
Flaw Size ◽  
Irradiation Embrittlement ◽  
Energy Agency ◽  
Detection Capabilities ◽  
Reactor Pressure

Reactor pressure vessels (RPVs) in nuclear power plants are important components that prevent non-ductile fracture considering neutron irradiation embrittlement as aging degradation and several types of transients. An analysis code called PASCAL for assessing failure frequencies of RPVs based on probabilistic fracture mechanics has been developed by the Japan Atomic Energy Agency. In failure frequency analyses, flaw size distribution in RPVs is one of the most important parameters, and it is determined by considering possible flaws generated during fabrication and the flaw-detection capabilities of nondestructive examinations (NDEs). Flaw-detection capabilities of NDEs are represented as probability of detection (POD) curves related to flaw sizes. In this study, the effects of NDEs on failure frequencies of RPVs are evaluated using PASCAL considering simplified POD curves in terms of minimum detectable flaw size, the smallest probability of non-detection (PND), and flaw size where POD value reaches the smallest PND.

scholarly journals Analysis of Low Probability of Detection Capability for Chaotic Standard Map-Based FH-OFDMA System

2021 ◽  
Vol 11 (5) ◽  
pp. 2198
Author(s):  
Junwoo Jung ◽  
Jaesung Lim ◽  
Sungyeol Park ◽  
Haengik Kang ◽  
Seungbok Kwon
Keyword(s):  
Detection Probability ◽  
Probability Of Detection ◽  
Lower Probability ◽  
Symbol Sequence ◽  
Ofdma System ◽  
Standard Map ◽  
Detection Probabilities ◽  
Low Probability ◽  
Transmitted Symbol ◽  
Basic Symbol

A frequency hopping orthogonal frequency division multiple access (FH-OFDMA) can provide low probability of detection (LPD) and anti-jamming capabilities to users against adversary detectors. To obtain an extreme LPD capability that cannot be provided by the basic symbol-by-symbol (SBS)-based FH pattern, we proposed two FH patterns, namely chaotic standard map (CSM) and cat map for FH-OFDMA systems. In our previous work, through analysis of complexity to regenerate the transmitted symbol sequence, at the point of adversary detectors, we found that the CSM had a lower probability of intercept than the cat map and SBS. It is possible when a detector already knows symbol and frame structures, and the detector has been synchronized to the FH-OFDMA system. Unlike the previous work, here, we analyze whether the CSM provides greater LPD capability than the cat map and SBS by detection probability using spectrum sensing technique. We analyze the detection probability of the CSM and provide detection probabilities of the cat map and SBS compared to the CSM. Based on our analysis of the detection probability and numerical results, it is evident that the CSM provides greater LPD capability than both the cat map and SBS-based FH-OFDMA systems.

scholarly journals A probabilistic method for structural integrity assurance based on damage detection structural health monitoring data

2021 ◽  
pp. 147592172110388
Author(s):  
Michael Siu Hey Leung ◽  
Joseph Corcoran
Keyword(s):  
Damage Detection ◽  
Particle Filtering ◽  
Structural Integrity ◽  
Probabilistic Method ◽  
Probability Of Detection ◽  
Monitoring Systems ◽  
Negative Results ◽  
Systematic Effects ◽  
Detection Capabilities ◽  
Integrity Assurance

The value of using permanently installed monitoring systems for managing the life of an engineering asset is determined by the confidence in its damage detection capabilities. A framework is proposed that integrates detection data from permanently installed monitoring systems with probabilistic structural integrity assessments. Probability of detection (POD) curves are used in combination with particle filtering methods to recursively update a distribution of postulated defect size given a series of negative results (i.e. no defects detected). The negative monitoring results continuously filter out possible cases of severe damage, which in turn updates the estimated probability of failure. An implementation of the particle filtering method that takes into account the effect of systematic uncertainty in the detection capabilities of a monitoring system is also proposed, addressing the problem of whether negative measurements are simply a consequence of defects occurring outside the sensors field of view. A simulated example of fatigue crack growth is used to demonstrate the proposed framework. The results demonstrate that permanently installed sensors with low susceptibility to systematic effects may be used to maintain confidence in fitness-for-service while relying on fewer inspections. The framework provides a method for using permanently installed sensors to achieve continuous assessments of fitness-for-service for improved integrity management.

Ultrasonic Inspection of Dissimilar Metal Welds for Probabilistic Reliability Assessment of Pipe Welds

2017 ◽  
Author(s):  
Sandra Dugan ◽  
Anne Jüngert
Keyword(s):  
Material Properties ◽  
Ultrasonic Inspection ◽  
Probability Of Detection ◽  
Grain Structure ◽  
Simple Relationship ◽  
Dissimilar Metal ◽  
Flaw Sizing ◽  
Safety Research ◽  
Lifetime Analysis ◽  
Ultrasonic Propagation

There are several sources of uncertainties which need to be considered in a probabilistic reliability and lifetime assessment of safety-relevant components. In addition to the probabilistic distribution of material properties, the size and properties of flaws present in a component contribute to uncertainties in the lifetime analysis. In a current reactor safety research project, a methodology for a probabilistic fracture mechanics assessment of reliability for components with austenitic and dissimilar metal welds will be developed using the combined results from statistical evaluation of material properties and ultrasonic inspection (UT). Dissimilar metal welds present a particular challenge for ultrasonic testing due to the effects of the material anisotropy on ultrasonic propagation and scattering. Evaluation of inspection results is typically done using image-based techniques. As there is no simple relationship between UT response and flaw size, criteria for image evaluation and flaw sizing have to be defined taking into account the influence of various factors such as material and flaw properties on the UT response. In this paper, we present results from a study of the influence of grain structure on the ultrasonic inspection results and discuss the challenges of extracting data for probability of detection (POD) analyses.

scholarly journals Wildfire Detection Probability of MODIS Fire Products under the Constraint of Environmental Factors: A Study Based on Confirmed Ground Wildfire Records

2019 ◽  
Vol 11 (24) ◽  
pp. 3031 ◽  
Author(s):  
Lingxiao Ying ◽  
Zehao Shen ◽  
Mingzheng Yang ◽  
Shilong Piao
Keyword(s):  
Environmental Factors ◽  
Detection Probability ◽  
Ground Level ◽  
Omission Error ◽  
Limiting Factor ◽  
Commission Error ◽  
Fire Size ◽  
Weather Factors ◽  
Local Conditions ◽  
Wildfire Occurrence

The Moderate Resolution Imaging Spectroradiometer (MODIS) has been widely used for wildfire occurrence and distribution detecting and fire risk assessments. Compared with its commission error, the omission error of MODIS wildfire detection has been revealed as a much more challenging, unsolved issue, and ground-level environmental factors influencing the detection capacity are also variable. This study compared the multiple MODIS fire products and the records of ground wildfire investigations during December 2002–November 2015 in Yunnan Province, Southwest China, in an attempt to reveal the difference in the spatiotemporal patterns of regional wildfire detected by the two approaches, to estimate the omission error of MODIS fire products based on confirmed ground wildfire records, and to explore how instantaneous and local environmental factors influenced the wildfire detection probability of MODIS. The results indicated that across the province, the total number of wildfire events recorded by MODIS was at least twice as many as that in the ground records, while the wildfire distribution patterns revealed by the two approaches were inconsistent. For the 5145 confirmed ground records, however, only 11.10% of them could be detected using multiple MODIS fire products (i.e., MOD14A1, MYD14A1, and MCD64A1). Opposing trends during the studied period were found between the yearly occurrence of ground-based wildfire records and the corresponding proportion detected by MODIS. Moreover, the wildfire detection proportion by MODIS was 11.36% in forest, 9.58% in shrubs, and 5.56% in grassland, respectively. Random forest modeling suggested that fire size was a primary limiting factor for MODIS fire detecting capacity, where a small fire size could likely result in MODIS omission errors at a threshold of 1 ha, while MODIS had a 50% probability of detecting a wildfire whose size was at least 18 ha. Aside from fire size, the wildfire detection probability of MODIS was also markedly influenced by weather factors, especially the daily relative humidity and the daily wind speed, and the altitude of wildfire occurrence. Considering the environmental factors’ contribution to the omission error in MODIS wildfire detection, we emphasized the importance of attention to the local conditions as well as ground inspection in practical wildfire monitoring and management and global wildfire simulations.

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