Nuclear Asset Integrity Archives

News & Views, Volume 44 | A First-of-a-Kind NDE Innovation from SI – The first PDI qualified manually-encoded DM weld procedure

April 27, 2018/in Jason Van Velsor, LATITUDE, News and Views, Non-Destructive Evaluation, Nuclear Asset Integrity/by Structural Integrity

By: Jason Van Velsor, Joe Agnew, and Owen Malinowski

Determining a course of action once in-service damage is discovered often requires applying a multi-disciplinary approach that utilizes Nondestructive Examination (NDE), analytical techniques such as stress analysis, and metallurgical lab examination. Such was the case recently for a combined cycle plant where indications were found through NDE on the inlet sides of two identical main steam stop/control valves but were not seen on the outlet side. In this case, Structural Integrity (SI) did not perform the field NDE but was requested to perform analytical and metallurgical assessments of the welds. The welds in question joined the 1Cr-1Mo-1/2V (SA-356 Grade 9) main stop/control valve body castings to Grade 91 piping, so the welds represent a ferritic-to-ferritic dissimilar metal weld (DMW). See the Dissimilar Metal Welds in Grade 91 Steel, (page 15) for further information. The welds were made using a 1Cr-1/2Mo (AWS type B2) filler metal, which matches the chromium content of the valve body, but is significantly undermatching in strength to both the valve body material and the Grade 91 piping.

The course of action taken was to perform local stress analysis and remaining life estimates for the downstream (outlet) connections of the valves to assess likelihood of future damage and establish an appropriate re-inspection interval. Detailed metallurgical analysis was also performed on a ring (entire circumference) section removed from one of the upstream welds (which exhibited both surface and volumetric indications in the weld metal) in order to provide insight into the damage mechanism and inform the stress analysis and remaining life estimates.

News & Views, Volume 44 | Planned and Emergent Outage Support – Structural Integrity is on Your Team

April 27, 2018/in News and Views, Nuclear Asset Integrity, Nuclear Energy, Nuclear Outage, Terry Herrmann/by Structural Integrity

By: Terry Herrmann

News & View, Volume 44 | Planned and Emergent Outage Support Structural Integrity is on Your Team While the 2018 Spring outage season is mostly behind us, we all know a key element in being able to provide safe, reliable, clean and economic power to energy consumers is how successfully plant outages are accomplished. I know from personal experience how good planning, including contingency planning, has significantly reduced outage durations (see Figure 1). I worked my first outage in 1981. It ran 110 days and was punctuated by rework, surprise discoveries and last-minute procurement of materials and services. By the late 1990s the industry had established outage milestones for design changes, significantly improved the level of detail in schedules, performed more work with the plant on line and implemented focused outage control organizations. Except for major activities like condenser retubing, power uprates and emergent issues that impact the scheduled critical path, outage durations today are almost exclusively associated with refueling activities.

News & Views, Volume 43 | Delivering the Nuclear Promise: 10 CFR 50.69 Alternative Treatments for Low Safety-Significant Components

October 5, 2017/in News and Views, Nuclear Asset Integrity, Nuclear Energy, Terry Herrmann/by Structural Integrity

By: Terry Herrmann

As all of us who work with nuclear energy know the US nuclear industry is engaged in a multi-year effort to generate power more efficiently, economically and safely. A key goal includes a significant reduction in operating expenses. This initiative is termed “Delivering the Nuclear Promise” (DNP) and is supported by nuclear utilities, vendors such as Structural Integrity, the Nuclear Energy Institute (NEI), Institute of Nuclear Power Operations (INPO), and the Electric Power Research Institute (EPRI).

10CFR50.69’ Risk Informed Engineering Programs (RIEP) is a regulation that enhances safety and provides the potential for large cost savings. This regulation allows plant owners to place systems, structures and components (SSCs) into one of the four risk-informed safety class (RISC) categories as indicated in the graphic to the right.

Industry experience to date suggests that 75 percent of safety-related SSCs can be categorized as RISC-3, low safety-significant (LSS), based on low risk. This is important because (a) it provides a focus on safety significance and (b) RISC-3 SSCs are exempted from “special treatment” requirements imposed by 10CFR50 Appendix B and other regulatory requirements (shown in the boxes at the bottom of page).