News & View, Volume 46 | Baffle-Former Bolt Management- Cost:Benefit Studies

News & Views, Volume 46 | Baffle-Former Bolt Management: Cost/Benefit Studies

By:  Tim Griesbach and News & View, Volume 46 | Baffle-Former Bolt Management- Cost:Benefit Studies

For the past several years baffle-former bolt (BFB) cracking in pressurized water reactors has become a significant concern for of PWR plants. In 2016, three similar Westinghouse designed plants (Indian Point 2, Salem 1, and D. C. Cook Unit 2) experienced significant numbers of cracked BFBs, attributed to irradiation-assisted stress corrosion cracking (IASCC). These plants had common characteristics that included the 4-loop plant design, downflow configuration, and Type 347 stainless steel bolting material. BFB cracking is not an entirely new phenomenon as it was initially detected in the French PWR fleet in the 1990s. However, the extent of cracking found in some of the US plants has greatly exceeded prior cracking. Extensive industry programs have identified and categorized by tier group the most susceptible plants, and the EPRI Materials Research Program (MRP) has published guidance regarding baffle-former bolt UT inspections for PWR plants for detection of degraded and cracked bolts in the baffle-former assembly (MRP-2017-009). 

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News & View, Volume 46 | Cross-Weld Creep-Rupture Testing for Seam Weld Life Management

News & Views, Volume 46 | Cross-Weld Creep-Rupture Testing for Seam Weld Life Management

By:  Jonnathan Warwick, Terry Totemeier, and Brian Chambers, Duke Energy

News & View, Volume 46 | Cross-Weld Creep-Rupture Testing for Seam Weld Life ManagementLongitudinal seam-welded hot-reheat steam piping operating in the creep regime is a continuing life-management challenge for many older fossil-fired power plants.  In response to catastrophic seam-welded piping failures in the 1980’s, the Electric Power Research Institute (EPRI) developed a comprehensive inspection protocol to insure continued safe operation of these piping systems [1]. The protocol requires full inspection of seam-welded hot-reheat pipe once a threshold of service exposure (calculated creep life consumption) has been reached, and re-inspection at intervals after the initial inspection depending on the inspection results.  Inspection for sub-surface cracking using ultrasonic testing (conventional or advanced) is strongly recommended, in combination with checking for surface cracking using wet fluorescent magnetic particle testing (WFMT).  Initial inspection and re-inspection of these piping systems represents a large maintenance cost for utilities, especially as older plants remain in service due to the changing economics of power generation.

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News & View, Volume 46 | Multi-discipline Solution for Pressure Vessel Asset Management

News & Views, Volume 46 | Multi-discipline Solution for Pressure Vessel Asset Management

By:  David Segletes and Dan Peters

One of the strengths of the Structural Integrity Associates (SI) team lies in the diversity of the skills and capabilities in the organization. Sure, SI can perform inspection, analysis, design, metallurgy, failure investigations, risk assessments, and project management, but one of the real values of working with SI is when all of those aspects are brought together to solve an issue.

News & View, Volume 46 | Multi-discipline Solution for Pressure Vessel Asset ManagementRecently, a client approached SI after finding a through-wall flaw in an autoclave at the head-to-shell weld as indicated by a visible dye liquid penetrant examination (Figure 1). The autoclave was one of eight similar vessels used for processing the client’s product. Three of the autoclaves are identical in construction to the flawed autoclave and operate with similar process conditions. Remote visual examination by the client indicated that all four autoclaves had similar observations at the inside of the head-to-shell weld, but only one was leaking. The remaining four autoclaves are smaller and are used infrequently. The initial call from the client was for SI to provide emergent support for inspection of the three autoclaves identical to the leaking one to meet production demands. SI responded quickly and examined all four autoclaves using a manual phased array ultra-sonic technique (PAUT) from the exterior of the vessel. The manual PAUT examination provided excellent coverage of the weld region and visualization of the through wall flaw (Figure 2).

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News & View, Volume 46 | Turnkey Rapid-Response Plant Support Disposition of Wall Thinning in Standby Service Water Piping

News & Views, Volume 46 | Turnkey Rapid-Response Plant Support Disposition of Wall Thinning in Standby Service Water Piping

By:  Jason Van Velsor, Roger Royer, and Eric Houston

News & View, Volume 46 | Turnkey Rapid-Response Plant Support Disposition of Wall Thinning in Standby Service Water PipingStructural Integrity recently had the opportunity to support a client’s emergent needs when their Standby Service Water (SSW) piping system experienced a pinhole leak just downstream of a valve. Concerned about other locations in the piping system with similar configurations, the site asked SI to assist with the expedited development of assessment and disposition plans for these other components. In response, SI was able to lean on our core competencies in failure analysis, advanced NDE inspection, and flaw evaluation to develop and deploy a comprehensive solution that met our client’s expedited timeline and helped them to mitigate the threat of future unplanned outages. The following sections outline how SI utilized our in-depth knowledge, cutting-edge technology, and world-class engineering to meet our client’s needs.

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News & View, Volume 46 | Evaluation of Reconfiguration and Damage of BWR Spent Fuel During Storage and Transportation Accidents

News & Views, Volume 46 | Evaluation of Reconfiguration and Damage of BWR Spent Fuel During Storage and Transportation Accidents

By:  Bill Lyon

News & View, Volume 46 | Evaluation of Reconfiguration and Damage of BWR Spent Fuel During Storage and Transportation AccidentsStructural Integrity Associates is participating in a Department of Energy (DOE) Integrated Research Projects (IRP) program focused on storage and transportation of used nuclear fuel (UNF). The project, entitled Cask Mis-Loads Evaluation Techniques, was awarded to a university-based research team in 2016 under the DOE Nuclear Fuels Storage and Transportation (NFST) project. The team is led by the University of Houston (U of H) and includes representatives from the University  of Illinois at Urbana-Champaign, the University of Southern California, the University of Minnesota, Pacific Northwest National Laboratory, and staff members from the Nuclear Fuel Technology and Critical Structures and Facilities divisions of SI. The primary objectives of NFST are to 1) implement interim storage, 2) improve integration of storage into an overall waste management system, and 3) prepare for large-scale transportation of UNF and high-level waste.  The goal of the cask mis-load project is to develop a probabilistically informed methodology, utilizing innovative non-destructive evaluation (NDE) techniques, determining the extent of potential damage or degradation of internal components of UNF canisters/casks during normal conditions of transport (NCT) and hypothetical accident conditions (HAC).

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News & View, Volume 46 | Identifying Failure Mechanisms of Typical I-Section Floodwalls

News & Views, Volume 46 | Identifying Failure Mechanisms of Typical I-Section Floodwalls

By: Eric Kjolsing and Dan Parker

News & View, Volume 46 | Identifying Failure Mechanisms of Typical I-Section FloodwallsIn 2018, Structural Integrity Associates, Inc. (SI) supported the United States Army Corp of Engineers (USACE) in the structural assessment of the concrete-to-steel connection in typical I-Section flood walls. A representative flood wall section is shown in Figure 1. This effort was part of a broader scope of work in which the USACE is revising their guidance for the design of flood and retaining walls, EM 1110-2-6066.  The purpose of the structural assessment was to better understand the mechanics of load transfer from the reinforced concrete section to the embedded sheet pile. Three-dimensional finite element models of the connection were developed employing non-linear constitutive properties for the concrete, structural steel and reinforcement to achieve this goal.  A total of nine different I-Wall configurations with varying wall geometry, sheet pile embedment depth, and connection details were analyzed.  Hydrostatic load was applied incrementally to simulate the actual load distribution due to a rising water level. 

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News & View, Volume 46 | Metallurgical Lab Case Study- Cracking of Grade 23 Steel Furnace Wall Tubes

News & Views, Volume 46 | Metallurgical Lab Case Study: Cracking of Grade 23 Steel Furnace Wall Tubes

By: Terry Totemeier

News & View, Volume 46 | Metallurgical Lab Case Study- Cracking of Grade 23 Steel Furnace Wall TubesGrade 23 is a creep strength enhanced ferritic (CSEF) steel that was designed to offer similar creep strength to Grade 91 but with lower Cr content and, in the original concept, fabrication without pre- and post-weld heat treatment making the material attractive for the furnace wall tubes of ultra-supercritical coal plants where T12 has insufficient strength and T91 would be too complex to fabricate. Experience gained with T23 has shown that pre-heat is necessary and that post-weld heat treatment should also be performed when the material is employed in “high restraint” applications such as furnace wall tubes. Like other CSEF steels, T23 is very sensitive to heat treatment, and care must be taken to ensure that hard, brittle microstructures do not enter service – particularly in high restraint applications such as furnace wall tubes.

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News & View, Volume 46 | TRU Compliance Achieves Accreditation as a Product Certification Body

News & Views, Volume 46 | TRU Compliance Achieves Accreditation as a Product Certification Body

By: Andy Coughlin

News & View, Volume 46 | TRU Compliance Achieves Accreditation as a Product Certification BodyTRU Compliance, a division of Structural Integrity Associates, announced in March the achievement of accreditation from the International Accreditation Service (IAS) as a product certification body for seismic, wind, and blast/physical security performance of nonstructural components. According to the International Accreditation Service, TRU Compliance is the second company to be certified for Seismic performance of non-structural components and the first company to be certified for Wind and Blast/Physical Security performance.

“This is a significant milestone for Structural Integrity and our certification agency, TRU Compliance,” Chris Larsen, Vice President of Critical Structures at Structural Integrity comments. “The accreditation further validates our robust program as well as our comprehensive approach, which not only meets the stringent guidelines of the ISO standards but offers our customers a full scope solution for product certification”.

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News & View, Volume 46 | Metallurgical Lab Featured Damage Mechanism- Waterwall Fireside Corrosion (WFSC) in Conventional Boilers

News & Views, Volume 46 | Metallurgical Lab Featured Damage Mechanism: Waterwall Fireside Corrosion (WFSC) in Conventional Boilers

By: Wendy Weiss

News & View, Volume 46 | Metallurgical Lab Featured Damage Mechanism- Waterwall Fireside Corrosion (WFSC) in Conventional BoilersIndustry experience shows that waterwall tubing in conventional boilers can be susceptible to fireside corrosion, depending on fuel type, firing practice, etc. In boilers where fireside corrosion has been identified as a maintenance issue, wastage rates of 5 to 25 mils/year are not uncommon. Since the mid 1990s, the installation of low NOx burner systems designed to lower NOx emissions has significantly increased the wastage rates in some boilers. Operators of subcritical boilers have reported wastage rates as high as 30 mils/year, while those operating supercritical boilers have reported rates exceeding 100 mils/year in the worst cases. These higher damage rates have resulted in an increase in tube failures, and operators have struggled to accurately define the extent of the damage and install the appropriate mitigating technologies.

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News & View, Volume 46 | Delivering Value- Modernization of Plant Automation Controls

News & Views, Volume 46 | Delivering Value: Modernization of Plant Automation Controls

By: Gerry Davina

News & View, Volume 46 | Delivering Value- Modernization of Plant Automation Controls

The modernization of plant automation controls represents a step change in performance that optimizes Operations and Maintenance resources, shifting their focus to performance maintenance and plant monitoring and away from inefficient corrective maintenance and troubleshooting.

According to the U.S. Energy Information Administration, the average age of the U.S.-based nuclear power plant is approximately 38 years old. Three of the “youngest” plants (Watts Bar, Nine Mile Point 2 and River Bend) all began construction in the mid-1970’s with their designs approved years earlier. In terms of industrial control systems, this means that most, if not all, of the plants in the U.S. nuclear fleet, continue to operate with 1970s in automation equipment and technology. Although it can be argued that the equipment and technology have proven to stand the test of time, the reality of the digital age, with low cost and high-powered processors, is that relay-based control systems are long-obsolete and no longer practical for any automation system that requires more than a handful of relays and switches. In an industry that has publicly advocated a commitment to improved reliability and efficiency, ironically, the most evident impact for any plant with the continued use of 40-year-old automation equipment and technology is poor system reliability and inefficiency burdening both Operations and Maintenance resources.

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