News & View, Volume 46 | Assessing Prestress Losses in a Nuclear Containment Structure for License Renewal

News & Views, Volume 46 | Assessing Prestress Losses in a Nuclear Containment Structure for License Renewal

By: Eric Kjolsing

News & View, Volume 46 | Assessing Prestress Losses in a Nuclear Containment Structure for License RenewalNuclear power plants around the world are approaching the end of their original 40-year design life.  Efforts are underway to extend the operating license for these plants to 60 years or beyond.  As part of the license extension, it must be demonstrated that the reactor containment building remains able to safely perform its intended functions for the extended duration of operation.  Many of these containment buildings utilize a post-tensioned concrete design where the tendons are grouted after tensioning.  Since these grouted tendons cannot be re-tensioned, an assessment for the loss in prestress beyond the original design life must be performed.

This article describes a methodology to assess the structural performance of a containment structure over time as a function of confidence in the tendon losses and is split into three parts:

  1. A description of the methodology
  2. A representative probabilistic assessment
  3. Representative analysis results

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News & View, Volume 46 | Strategies, Projects and Technologies to Help Improve NDE Reliability in the Pipeline Industry

News & Views, Volume 46 | Strategies, Projects and Technologies to Help Improve NDE Reliability in the Pipeline Industry

By: Scott Riccardella, Jason Van Velsor, and Roger Royer

News & View, Volume 46 | Strategies, Projects and Technologies to Help Improve NDE Reliability in the Pipeline Industry

Pipeline operators face a multitude of threats, including service, environmental, or operational induced degradation to pipelines and related facilities. Non-Destructive Examination (NDE) is often used to characterize the nature and extent of this degradation. Thus, there is a critical need for reliable NDE as pipeline operators rely extensively on NDE as the basis for validating In-Line Inspection (ILI) results, determining fitness for service, and making repair and other operational decisions. Erroneous or inaccurate characterization of these defects can lead to unexpected leaks or failures, unnecessary and costly repairs, the establishment of an incorrect remaining life or re-assessment interval, and inaccurate (in)validation of ILI results.

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News & View, Volume 46 | Acoustic and Blowdown Load Calculations for Reactor Internals

News & Views, Volume 46 | Acoustic and Blowdown Load Calculations for Reactor Internals

By: Matthew Walter

News & View, Volume 46 | Acoustic and Blowdown Load Calculations for Reactor InternalsAs part of the general design criteria for nuclear power plants, the primary structures and systems of the plant must be designed to handle postulated accident events, including the dynamic effects of postulated pipe ruptures. For a Boiling Water Reactor, analyzed events include various accident conditions in the recirculation piping, including a Loss of Coolant Accident (LOCA). One postulated LOCA event is assumed to be an instantaneous double-ended guillotine break of the recirculation line. This event causes several loads to be imparted on the reactor vessel, attached piping, and reactor internal components. [Some loads such as jet impingement, annulus pressurization, and pipe whip impart loads on the outside of the reactor vessel and the attached piping.][ Other loads, including flow-induced drag and acoustic loads, transmit loads inside the vessel on critical components such as jet pumps, core shroud, and the shroud support structure.] Figure 1 shows the pipe and resulting loads.

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News & View, Volume 46 | Adding Value Through Test Informed Modeling- Hydro Structures

News & Views, Volume 46 | Adding Value Through Test Informed Modeling: Hydro Structures

By: Eric Kjolsing and Dan Parker

News & View, Volume 46 | Adding Value Through Test Informed Modeling- Hydro StructuresIn 2018, Structural Integrity Associates (SI) supported a utility in the structural assessment of a submerged concrete intake tower.  The tower is nearly a century old and was investigated as part of the utility’s periodic maintenance program. 

The assessment required the generation of an analysis model that accounted for both the structure and the surrounding water.  When accounting for fluid effects, a typical analysis approach is to develop a fluid-structure interaction (FSI) model that explicitly accounts for the interaction between the surrounding water and concrete tower.  However, this modeling approach is expensive both in terms of (a) cost, due to the increased effort needed in generating the model and (b) schedule, due to the increased analysis run time.  In lieu of developing an FSI model, SI implemented an alternative numerical approach to model the effects of the water and justified the approach through physical testing of the in-situ structure.

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News & View, Volume 46 | The Newest Phased Array Ultrasonic Technique- Full Matrix Capture

News & Views, Volume 46 | The Newest Phased Array Ultrasonic Technique: Full Matrix Capture

By: Jeff Milligan, Steve Gressler, and Allen PorterNews & View, Volume 46 | The Newest Phased Array Ultrasonic Technique- Full Matrix Capture

Full Matrix Capture (FMC) and Total Focusing Method (TFM) have evolved over the past few years into NDE buzz words that warrant explanation and context for their proper and successful application.  Structural Integrity (SI) is well vested and engaged in FMC and actively exploring the use of this technology where it enhances ultrasonic sensitivity and characterization to bring added value to our clients.  An explanation of these technologies and what they mean to the future of ultrasonic inspection follows.

Phased Array Ultrasonic Testing (PAUT) has evolved significantly over the last 20+ years, with improvements and innovations in sensor design, signal processing, and data interpretation; however, the method by which PAUT is applied has remained relatively unchanged: Excite an array of transducer elements with predetermined time delays, called focal laws, and receive resulting reflections with the array of transducer elements,

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News & View, Volume 46 | NDE Best Practices for Generator Rotors

News & Views, Volume 46 | NDE Best Practices for Generator Rotors

By: Paul Zayicek News & View, Volume 46 | NDE Best Practices for Generator Rotors

Three factors typically drive inspection intervals of generator rotors:

  1. a timeframe recommended by the insurance carrier or OEM
  2. an engineering evaluation that supports a different inspection interval due to service operation events or existing rotor damage
  3. industry best practices

Drivers from the OEM include issues defined in service bulletins or technical information letters that pertain to the entire fleet or some subset of the population. Intervals based on engineering evaluations can be derived from an identified damage mechanism with the rotor or with a critical component. An engineering evaluation can also provide for extended inspection intervals in situations where the generator has no inherent material issues, has a clean inspection record, and sees limited operational stress such as in a base-load unit.

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News & View, Volume 46 | Hydrogen Fueling Structural Integrity into New Markets

News & Views, Volume 46 | Hydrogen Fueling Structural Integrity into New Markets

By:  Daniel Peters and Myles ParrNews & View, Volume 46 | Hydrogen Fueling Structural Integrity into New Markets

Energy sources that don’t have carbon emissions are rapidly developing in the country and around the world today.  The use of renewable energy sources such as wind, hydro, and solar is becoming increasingly common.  One area that is also changing is in the automotive arena.  The use of alternative fuels in the transportation sector, such as natural gas and hydrogen, has been under development for many years.  Natural gas is quite common today in the public transportation sector in many cities for fueling buses in cities. 

Development of hydrogen fuel cell automobiles increased significantly around the turn of the century and recently has gained increasing popularity.  Many hurdles have been considered and needed to be overcome to make this a practical reality.  Issues such as reliability of components used in cars, risks of fires due to leaks, and sources of hydrogen needed for those cars are just a few of them.

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News & View, Volume 46 | Plant Integrity Assistant – There’s an App for That! PlantTrack App Now Available

News & Views, Volume 46 | Plant Integrity Assistant – There’s an App for That!

By:  Matt Freeman

PlantTrack App now available

News & View, Volume 46 | Plant Integrity Assistant – There’s an App for That! PlantTrack App Now AvailablePlant engineers must often answer ‘what damage is this piece of equipment susceptible to, and what can we do about it?’ or ‘how much longer can this component continue operating’?   A free app is now available in both the Google Play store and the Apple App store to help answer these and other equipment integrity questions (see figure 1).

The PlantTrack App is a plant integrity assistant that provides life calculators, damage mechanism guides, technical articles, lab sample submittal form, and other functions relevant for plant engineers.  While it is geared towards fossil (both coal and gas) power plants, it has applicability for equipment at other plants as well.  For subscribers to the PlantTrack web application, the mobile app also provides a dashboard view of inspection history, action items, damage tracking results, etc.  Users of the PlantTrack software will recognize some of the features from the ‘PlantTrack Tools’ that have previously been available through a web browser.

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News & View, Volume 45 | Improved Asset Management Through Test Informed Analysis

News & Views, Volume 45 | Improved Asset Management Through Test Informed Analysis

News & View, Volume 45 | Improved Asset Management Through Test Informed AnalysisBy:  Eri Kjolsing

Introduction
Structures may experience unforeseen operating environments or site-specific hazards leading to changes in the structure’s performance, safety, and longevity.  These changes often prompt asset owners to undertake analysis efforts to ensure satisfactory structural performance for the updated conditions. However, conventional analyses that fail to capture the true behavior of a structure can lead to inaccurate analysis results, causing owners to make less than ideal asset management decisions.  Structural Integrity (SI) is uniquely positioned to pair our dynamic characterization and advanced structural analysis capabilities to generate a better structural model.  SI vibration experts use impact testing, forced vibration, or ambient excitation sources, along with proprietary signal processing software, to non-destructively characterize the dynamic behavior of structural systems.  This characterization is used to inform advanced structural analyses by SI analysis experts to provide more accurate results related to operational improvements, damage location, and retrofits.

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News & View, Volume 45 | Interval Relief from RPV Threads in Flange Examination Requirements

News & Views, Volume 45 | Interval Relief from RPV Threads in Flange Examination Requirements

By:  Scott Chesworth

News & View, Volume 45 | Interval Relief from RPV Threads in Flange Examination RequirementsASME Code Section XI requires that the RPV Threads in Flange component (Category B-G-1, Item Number B6.40, see Figure 1) be inspected each inspection Interval using volumetric examination.  However, there is general agreement that the inspection does not contribute to the overall safety of the RPV.  Industry experience indicates that these examinations have not been identifying service-induced degradation and that they have negative impacts on worker exposure, personnel safety, and outage critical path time.  Savings from the elimination of this inspection can be applied to other more meaningful inspections of other more risk-significant plant components.

EPRI Report 3002007626 (March 2016) provides the basis for eliminating the RPV Threads in Flange examination requirement.  This report includes the results of an industry survey in which 168 units provided the status of their RPV Threads in Flange examination, as well as insight into the impacts of conducting these examinations.

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