Recent Developments in Constraint-Based Fracture Mechanics Methodology with Applications to the Assessment of Structural Integrity

2003 ◽  
Vol 80 (11) ◽  
pp. 753 ◽  
Author(s):  
David Lidbury
Keyword(s):  
Fracture Mechanics ◽  
Structural Integrity ◽  
Recent Developments

Fracture mechanics in design and service: ‘living with defects’ - Statistical aspects of design: risk assessment and structural integrity

1981 ◽  
Vol 299 (1446) ◽  
pp. 111-130 ◽  
Keyword(s):  
Fracture Mechanics ◽  
Structural Reliability ◽  
Structural Integrity ◽  
Product Liability ◽  
Probabilistic Methods ◽  
Statistical Variations ◽  
Engineering Designs ◽  
Recent Developments ◽  
Quantitative Basis ◽  
And Control

Statistical variations in input parameters that affect structural reliability have historically been incorporated approximately in engineering designs by application of safety factors. Increased concerns over the injury potential and costs of licensing, insurance, field repairs or recalls, and product liability claims now demand more quantitative evaluation of possible flaws or unusual usage conditions that might result from statistical variations or uncertainties. This paper describes the basic concepts of probabilistic fracture mechanics that are used to assess and control risk. Recent developments in combined analysis methods are presented that utilize field experience data with probabilistic analysis to improve the accuracy of the structural integrity predictions. Several specific examples are described that illustrate how these probabilistic methods are used to assess risk and to provide a quantitative basis for establishing design, operation or maintenance allowables. These procedures, which realistically model the actual statistical variations that exist, can eliminate unnecessarily conservative approximations and often achieve improved reliability at reduced cost.

Verification of Probabilistic Fracture Mechanics Analysis Code for Reactor Pressure Vessel

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
Yinsheng Li ◽  
Genshichiro Katsumata ◽  
Koichi Masaki ◽  
Shotaro Hayashi ◽  
Yu Itabashi ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Working Group ◽  
Power Plants ◽  
Structural Integrity ◽  
Pressure Vessels ◽  
Irradiation Embrittlement ◽  
Energy Agency ◽  
Probabilistic Fracture Mechanics ◽  
Integrity Assessments ◽  
Reactor Pressure

Abstract Nowadays, it has been recognized that probabilistic fracture mechanics (PFM) is a promising methodology in structural integrity assessments of aged pressure boundary components of nuclear power plants, because it can rationally represent the influencing parameters in their inherent probabilistic distributions without over conservativeness. A PFM analysis code PFM analysis of structural components in aging light water reactor (PASCAL) has been developed by the Japan Atomic Energy Agency to evaluate the through-wall cracking frequencies of domestic reactor pressure vessels (RPVs) considering neutron irradiation embrittlement and pressurized thermal shock (PTS) transients. In addition, efforts have been made to strengthen the applicability of PASCAL to structural integrity assessments of domestic RPVs against nonductile fracture. A series of activities has been performed to verify the applicability of PASCAL. As a part of the verification activities, a working group was established with seven organizations from industry, universities, and institutes voluntarily participating as members. Through one-year activities, the applicability of PASCAL for structural integrity assessments of domestic RPVs was confirmed with great confidence. This paper presents the details of the verification activities of the working group, including the verification plan, approaches, and results.

Recent Developments of Fracture Mechanics Tools for Nozzle Corners

2017 ◽  
Author(s):  
Arnaud Blouin ◽  
Stéphane Chapuliot ◽  
Stéphane Marie ◽  
André Jaubert ◽  
Stephan Courtin
Keyword(s):  
Fracture Mechanics ◽  
Shock Loading ◽  
Recent Effort ◽  
Analytical Scheme ◽  
Evaluation Scheme ◽  
Important Target ◽  
Recent Developments ◽  
Growth Evaluation ◽  
Large Benefit ◽  
High Level

A recent effort was performed within AREVA-NP in order to develop and validate specific tools dedicated to the Fracture Mechanics Assessment of nozzle and penetration corners. This work is motivated by the need to perform accurate defect assessments for this geometry potentially submitted to a high level of stress. It includes: • The development of a specific compendium for the calculation of the Stress Intensity Factor under various types of loading like internal pressure or cold thermal shocks; • The evaluation of the effect of plasticity through simplified analytical schemes; • The validation through the comparison to existing solutions. One important target of those tools being the Fatigue Crack Growth evaluation under cyclic thermal shock loading situations, a validation of the fully analytical evaluation scheme was performed by a comparison to a complex 3D Finite Element Modelling of a defect propagating at a flange corner. This comparison is presented in the paper and illustrates the large benefit in terms of time and simplicity of the analytical scheme for such evaluation.

Review of the Current Conservatisms in the Assessment of Thin-Walled Structures

2009 ◽  
Author(s):  
R. S. Kulka ◽  
A. J. Price
Keyword(s):  
Fracture Mechanics ◽  
Best Practice ◽  
Structural Integrity ◽  
Fracture Behaviour ◽  
Stress Distributions ◽  
Limit Loads ◽  
Thin Walled Structures ◽  
Commercial Drivers ◽  
Thin Walled ◽  
Integrity Assessments

Current methods for performing fracture mechanics assessments of thin-walled structures possess significant levels of conservatism, since they are often for general use with both thin-walled and thick-walled structures. In many industries, there are significant commercial drivers for reducing the amount of conservatism in these assessments. An enhanced understanding of the fracture behaviour of thin-walled structures in different situations may lead to the development of more appropriate structural integrity assessments. A review of the information pertaining to fracture mechanics analysis of thin-walled structures has been conducted. There are indications that improvements to the best practice methodology may be made, through improved tensile and toughness properties, consideration of limit loads, and the effect of residual stress distributions.

Bit Dysfunction Characterization Using a Sensor System at the Bit

2007 ◽  
Author(s):  
Sorin G. Teodorescu ◽  
Eric C. Sullivan ◽  
Paul E. Pastusek
Keyword(s):  
Structural Integrity ◽  
Sensor System ◽  
Sensor Data ◽  
Drilling Performance ◽  
Rock Formations ◽  
Drill Bits ◽  
Pdc Bit ◽  
Recent Developments ◽  
Drilling Operations ◽  
Rock Bit

Drilling operations represent a major cost in discovering and exploring new petroleum reserves. Poor drilling performance, for example low ROP, can lead to high cost per foot. In order to optimize the performance of drill bits, the dynamic behavior of the bit and the drillstring has to be monitored. In recent developments, we have deployed a sensor / data acquisition (DAQ) system that is mounted at the bit, which can monitor the behavior of the drill bit and dynamic dysfunctions associated with the operating parameters, different rock formations and rock/bit interactions. A modified shank accommodates the sensor / DAQ system. Its location was determined based on extensive analysis of the bit’s structural integrity. Initial tests verified the ability of the system to identify PDC bit dysfunctions, such as backward whirl — one of the most bit damaging events in the drilling operation. Placing a sensor system in the bit allows for accurate pattern recognition and severity determination in terms of dynamic dysfunctions of the bit and can aid in optimizing drilling parameters in pursuit of increased ROP and reduced drilling costs.

Deterministic and Probabilistic Assessments of the Reactor Pressure Vessel Structural Integrity: Benchmark Comparisons

2003 ◽  
Author(s):  
Silvia Turato ◽  
Vincent Venturini ◽  
Eric Meister ◽  
B. Richard Bass ◽  
Terry L. Dickson ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Pressure Vessel ◽  
Structural Integrity ◽  
Safety Concern ◽  
Nuclear Regulatory Commission ◽  
Reactor Pressure Vessel ◽  
Oak Ridge ◽  
Integrity Assessment ◽  
Probabilistic Fracture Mechanics ◽  
Reactor Pressure

The structural integrity assessment of a nuclear Reactor Pressure Vessel (RPV) during accidental conditions, such as loss-of-coolant accident (LOCA), is a major safety concern. Besides Conventional deterministic calculations to justify the RPV integrity, Electricite´ de France (EDF) carries out probabilistic analyses. Since in the USA the probabilistic fracture mechanics analyses are accepted by the Nuclear Regulatory Commission (NRC), a benchmark has been realized between EDF and Oak Ridge Structural Assessments, Inc. (ORSA) to compare the models and the computational methodologies used in respective deterministic and probabilistic fracture mechanics analyses. Six cases involving two distinct transients imposed on RPVs containing specific flaw configurations (two axial subclad, two circumferential surface-breaking, and two axial surface-braking flaw configurations) were defined for a French vessel. In two separate phases, deterministic and probabilistic, fracture mechanics analyses were performed for these six cases.

NESC-VII: Fracture Mechanics Analyses of WPS Experiments on Large-Scale Cruciform Specimen

2011 ◽  
Author(s):  
Shengjun Yin ◽  
Paul T. Williams ◽  
B. Richard Bass
Keyword(s):  
Fracture Mechanics ◽  
Large Scale ◽  
Structural Integrity ◽  
National Laboratory ◽  
Pressure Vessels ◽  
Cooperative Action ◽  
Oak Ridge ◽  
Integrity Assessment ◽  
Feasibility Test ◽  
Reactor Pressure

This paper describes numerical analyses performed to simulate warm pre-stress (WPS) experiments conducted with large-scale cruciform specimens within the Network for Evaluation of Structural Components (NESC-VII) project. NESC-VII is a European cooperative action in support of WPS application in reactor pressure vessel (RPV) integrity assessment. The project aims in evaluation of the influence of WPS when assessing the structural integrity of RPVs. Advanced fracture mechanics models will be developed and performed to validate experiments concerning the effect of different WPS scenarios on RPV components. The Oak Ridge National Laboratory (ORNL), USA contributes to the Work Package-2 (Analyses of WPS experiments) within the NESC-VII network. A series of WPS type experiments on large-scale cruciform specimens have been conducted at CEA Saclay, France, within the framework of NESC VII project. This paper first describes NESC-VII feasibility test analyses conducted at ORNL. Very good agreement was achieved between AREVA NP SAS and ORNL. Further analyses were conducted to evaluate the NESC-VII WPS tests conducted under Load-Cool-Transient-Fracture (LCTF) and Load-Cool-Fracture (LCF) conditions. This objective of this work is to provide a definitive quantification of WPS effects when assessing the structural integrity of reactor pressure vessels. This information will be utilized to further validate, refine, and improve the WPS models that are being used in probabilistic fracture mechanics computer codes now in use by the NRC staff in their effort to develop risk-informed updates to Title 10 of the U.S. Code of Federal Regulations (CFR), Part 50, Appendix G.

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