News & View, Volume 44 | Integrated Flow Distributors (IFD) for Bottom Tubesheet Filter:Demineralizers Initial Installation & Performance at Browns Ferry Nuclear Station

News & Views, Volume 44 | Integrated Flow Distributors (IFD)

By:  Ed Dougherty and Al Jarvis

for Bottom Tubesheet Filter/Demineralizers Initial Installation and Performance at Browns Ferry Nuclear StatioNews & View, Volume 44 | Integrated Flow Distributors (IFD) for Bottom Tubesheet Filter:Demineralizers Initial Installation & Performance at Browns Ferry Nuclear StationThe Browns Ferry Nuclear Station (BFNS) intends to implement an extended power uprate (EPU) at all three units beginning in 2018 for Unit 3 and Unit 1, and in 2019 for Unit 2. EPU implementation will increase the total thermal power of each unit by 494 MWth resulting in a total uprate of 20% from the originally licensed thermal power of 3293 MWth.

Each BFNS unit is currently designed with ten bottom tubesheet condensate filter/demineralizers (CF/Ds) in the condensate treatment system that require an application of a powdered resin precoat to perform the function of demineralization. The precoat material is applied as an overlay on top of vertical filter septa. The filter septa have an inner pleated area, and with a precoat overlay, perform the function of demineralization as well as particulate iron removal. In the absence of circulating water leakage into the condenser, the primary function of the CF/Ds is to remove particulate iron that collects in the condenser hotwell. The iron source is from the corrosion of carbon steel piping and components in contact with main steam and heater drain systems.

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News & View, Volume 44 | Strategic Internal Corrosion Monitoring for Gas Pipelines

News & Views, Volume 44 | Strategic Internal Corrosion Monitoring for Gas Pipelines

By:  Lance Barton and Tom Pickthall (EnhanceCo)

REGULATORY OVERVIEW
News & View, Volume 44 | Strategic Internal Corrosion Monitoring for Gas PipelinesA March 16, 2017, advisory bulletin (Docket No. PHMSA-2016-0131 – “Pipeline Safety: Deactivation of Threats”) gave guidance on the deactivation of pipeline threats, including the threat of internal corrosion.  On April 8, 2016, PHMSA issued a Notice of Proposed Rulemaking (NPRM) entitled “Safety of Gas Transmission and Gathering Pipelines”. Section §192.478 “Internal Corrosion Control: Onshore transmission monitoring and mitigation” of the NPRM would increase the scrutiny and requirements for monitoring and mitigating the threat of internal corrosion for the gas industry.

This bulletin and NPRM reinforce the requirements of CFR part 192-subpart O, Section 192.937, requiring gas pipeline operators to continuously assess their pipelines for the threat of internal corrosion as part of their overall integrity management program.  One of the requirements is to determine if the gas entering the system is corrosive or not corrosive.  The optimal way to prove that the gas is not corrosive is to build a thorough continuous monitoring program that considers guidance from the NPRM and the advisory bulletin.

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News & View, Volume 44 | Dissimilar Metal Welds in Grade 91 Steel

News & Views, Volume 44 | Dissimilar Metal Welds in Grade 91 Steel

By:  Terry Totemeier

Introduction
News & View, Volume 44 | Dissimilar Metal Welds in Grade 91 SteelA dissimilar metal weld (DMW) is created whenever alloys with substantially different chemical compositions are welded together – for example, when a low-alloy steel such as Grade 22 (2¼ Cr-1Mo) is welded to an austenitic stainless steel such as TP304H (18Cr-8Ni).  Many DMWs are commonly present in fossil-fired power plants, examples being material transitions in boiler furnace tubes, stainless steel attachments welded onto ferritic steel tubes or pipes, and stainless steel thermowells or steam sampling lines in ferritic steel pipes.  The chemical composition gradients associated with DMWs present unique issues relative to their design, in-service behavior, and life management, particularly for those DMWs operating at elevated temperatures where solid-state diffusion and cyclic thermal stresses are factors, which was previously presented in News and Views (Volume 43, page 19).

With the now widespread use of Grade 91 steel (9Cr-1Mo-V-Nb) for elevated-temperature applications in modern power plants, DMWs involving this material have become common, and increasing service experience has revealed some unique characteristics and failure mechanisms, especially in thicker-section DMWs with austenitic materials.  This article presents a short overview of Grade 91 DMWs:  their design, fabrication, and failure, with emphasis on current industry issues.

There are two basic classes of DMWs in Grade 91 steel:  ferritic-to-ferritic and ferritic-to-austenitic.  The first type corresponds to Grade 91 welded to another ferritic steel with a lower chromium content, such as Grade 22; the second type corresponds to Grade 91 welded to an austenitic stainless steel such as TP304H.  Each of these types has unique concerns and considerations.

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News & View, Volume 44 | Real-Time Damage Tracking with SI Technology and GP Strategies’ EtaPro Expanding Capabilities in Condition-based Pressure-part Integrity Management

News & Views, Volume 44 | Real-Time Damage Tracking with SI Technology and GP Strategies’ EtaPro

By:  Matt Freeman

Expanding Capabilities in Condition-based Pressure-part Integrity Management

News & View, Volume 44 | Real-Time Damage Tracking with SI Technology and GP Strategies’ EtaPro Expanding Capabilities in Condition-based Pressure-part Integrity ManagementStructural Integrity and GP Strategies recently announced an agreement to bring SI’s technology for calculating, tracking, and trending life consumption of piping and boiler components to GP Strategies EtaPRO real-time monitoring platform (Press release here).  SI has a long history with creep and fatigue damage monitoring applications, most recently with the suite of applications available as part of SI’s PlantTrack platform.  The partnership with GP Strategies brings that technology to EtaPRO, which is used worldwide by power-generating organizations to monitor the performance and reliability of their generation assets.

EtaPRO users will benefit from easy integration of SI’s leading-edge Boiler and Piping Component Reliability (BPCR) modules to quantify damage to high-pressure, high-temperature components such as tubing, piping, headers, and desuperheaters. The BPCR modules track and trend accumulated creep and fatigue damage in real time using SI’s proprietary algorithms that combine actual operating data and material condition with a plant’s specific configuration. Plant operators can use the resulting life consumption estimates to guide asset management decisions, such as changes in operating procedures, targeted inspections, or off-line analysis of anomalous conditions.

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News & View, Volume 44 | Radiation Source Term Assessments

News & Views, Volume 44 | Radiation Source Term Assessments

By:  Jen Jarvis and Al Jarvis

News & View, Volume 44 | Radiation Source Term AssessmentsNuclear plant workers accrue most of their radiation exposure during refueling outages, when many plant systems are opened for corrective and preventive maintenance. The total refueling outage radiation exposure can be 100-200 person-Rem at a typical Boiling Water Reactor (BWR), and 30-100 person-Rem at a typical Pressurized Water Reactor (PWR). Accrued refueling outage radiation exposure values can be significantly greater than these values depending upon radiation fields, outage work scope, and emergent work. Outage radiation exposure is one metric used by a plant to determine outage success and by industry regulators in assessing the overall performance of a plant. Plants with high personnel radiation exposure tend to be those plants with more equipment problems and more unscheduled shutdowns; consequently, they may be subjected to increased regulatory oversight.

Radiation source term assessments are performed to understand the causes of high collective radiation exposure and to help plants evaluate their strategies for source term reduction. This involves understanding how a plant’s material choices and chemistry and operational history influence the radiation fields that develop in the plant systems. Consequently, a source term evaluation is very plant-specific, but can help a plant identify which strategies may be most effective for their specific situation. 

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News & View, Volume 44 | The Impact of the ASCE 7-16 Standard on Seismic Design and Certification of Equipment

News & Views, Volume 44 | The Impact of the ASCE 7-16 Standard on Seismic Design and Certification of Equipment

By:  Matt Tobolski

News & View, Volume 44 | The Impact of the ASCE 7-16 Standard on Seismic Design and Certification of EquipmentThings change, that’s just a fact of life. But when it comes to engineering codes and standards, change can be confusing, frustrating and expensive. As it relates to seismic design and certification of equipment, it is beneficial to understand the impact of code changes early to begin incorporating requirements in new equipment design, product updates and in the certification process.

One of the main structural design codes used in the United States and abroad, American Society of Civil Engineering (ASCE) 7, undergoes revisions on a five-year cycle. These revisions are based on input from committee members, building officials, interested parties and academia with the goal of ensuring specific performance objectives are achieved as well as incorporating lessons learned from practice. With the increase in enforcement of seismic certification provisions over the past 10 years, there has been a noticeable increase in industry lessons learned. The updates to the seismic provisions in ASCE 7-16 relating to equipment design and certification can primarily be attributed to these lessons learned.

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News & View, Volume 43 | In-Line Inspection An Improvement Over Pressure Testing for Pipeline Integrity Management

News & Views, Volume 43 | In-Line Inspection – An Improvement Over Pressure Testing for Pipeline Integrity Management

By:  Scott Riccardella, Dilip Dedhia, and Peter Riccardella 

News & View, Volume 43 | In-Line Inspection An Improvement Over Pressure Testing for Pipeline Integrity ManagementStructural Integrity recently performed probabilistic fracture mechanics (PFM) analysis of a gas transmission pipeline for a major U.S. operator.  The analysis yielded interesting insights in several areas:

Pressure Testing versus In-Line Inspection
Pressure testing has long been considered the gold standard for assuring pipeline integrity.  By testing at a factor (e.g., 1.25x or 1.5x) above the Maximum Allowable Operating Pressure (MAOP), any size critical flaws in the line would fail at this pressure level and are thus removed prior to future service.  Subcritical flaws that remain after the test will be smaller than the critical flaw sizes during operation, and thus can be assumed to have some margin for growth before they become critical in service.  Flaw growth rates can be calculated based on operational and environmental factors to establish a reassessment interval for future testing or inspections.

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News & View, Volume 43 | Perforation, Scabbing, and Reinforcement Optimization in an Aircraft Impact Analysis (AIA)

News & Views, Volume 43 | Perforation, Scabbing, and Reinforcement Optimization in an Aircraft Impact Analysis (AIA)

By:  Eric Kjolsing

BackgroundNews & View, Volume 43 | Perforation, Scabbing, and Reinforcement Optimization in an Aircraft Impact Analysis (AIA)
A 2016 project utilized a variety of Structural Integrity competencies to analyze a beyond design basis threat at an overseas nuclear power plant.  The client was assessing a plant design and approached Structural Integrity to investigate local perforation and scabbing of a reinforced concrete wall due to hard missile impact.  Perforation occurs when a missile fully penetrates and passes through a target while scabbing occurs when material is ejected from the back face of a target, potentially striking personnel and equipment inside the facility.  The client also sought to reduce the volume of wall reinforcement, a potentially large cost savings, while still meeting the facility’s strict design criteria.  The project is best described in four stages and took advantage of our AIA experience, finite element (FE) modeling expertise, and proprietary concrete constitutive model ANACAP.

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News & View, Volume 43 | Attemperator Damage Prevention A Case Study Using Online Monitoring

News & Views, Volume 43 | Attemperator Damage Prevention A Case Study Using Online Monitoring

By:  Fred DeGrooth and Ulrich Woerz

News & View, Volume 43 | Attemperator Damage Prevention A Case Study Using Online MonitoringAttemperators (aka desuperheaters) are used in fossil and combined cycle plants to protect boiler/HRSG components and steam turbines from temperature transients that occur during startup or load changes. The attemperator sprays water droplets into the superheated steam to ensure that the downstream, mixed, steam temperature will not adversely affect downstream components.  While there are a number of attemperator designs and configurations (Figure 1 shows a schematic of a typical arrangement), all of them are potentially vulnerable to damage, making attemperators one of the most problematic components – particularly in combined cycle plants. If the causes of damage are not identified (and addressed) early, then cracking and steam leaks can occur leading to costly repairs and replacements. 

The frequent cycling and wide operating range of combined cycle plants impose particular demands on attemperator functionality.  Spraywater demand to the attemperator can fluctuate greatly within a startup where heat input to the boiler and steam flow are changing rapidly.  At part load operation spraywater may be required continuously to moderate steam temperatures because of high exhaust gas temperature from the combustion turbine.  Spraywater may also be demanded when duct burners are fired. 

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News & View, Volume 43 | Wind Project Continued Operation Beyond Designed Life

News & Views, Volume 43 | Wind Project Continued Operation Beyond Designed Life

By:  Ceci Wilson

News & View, Volume 43 | Wind Project Continued Operation Beyond Designed LifeWith the increase of renewable energy into the power generation market, aggressive state renewable targets, and recently renewed production tax credit (PTC), wind power generation demand is positioned to increase significantly. This is good news not only for new wind projects but also for existing wind power infrastructure.

As the wind energy market and demand has grown quickly, so has the technology – better turbine controls, more efficient drivetrains, longer and lighter blade designs, and taller towers. Figure 1 shows that in 2000 wind turbines had an average nameplate capacity of slightly less then 1 MW and 30% capacity factors, while the average nameplate capacity in 2016 was 2.15 MW [1], with capacity factors near 40%. Blade lengths of 25 meters in 2000 are dwarfed by the more recent 50 meter blades (see Figure 2). Longer blades at higher hub heights and more efficient controls means that new wind projects can achieve more power generation capacity with half (or less) the number of turbines compared to 10-year-old projects.

A typical wind turbine is designed for 20-year operation. In 2017, most of the US wind turbine fleet is less than 10 years old, with 20% of the fleet between 10 and 16 years of age. As wind turbines age and near their design life of 20 years, owners should start assessing their future options for continued operation:

  1. Partial repowering: Would it be beneficial to invest in upgrades that take advantage of new technology to increase power generation and/or turbine life?
  2. Repowering: Given technology development, is it better to replace existing wind turbines with new ones?
  3. Life extension: Can the operating wind turbines continue operating past 20 years as-is (or with minor adjustments)?

The answers to these questions are project and site specific.

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