Fracture Mechanics Archives

News & Views, Volume 49 | Inspection Optimization: Probabilistic Fracture Mechanics

April 20, 2021/in Bob Grizzi, Company News, Fracture Mechanics, News, News and Views, Nuclear Asset Integrity, Nuclear Energy, Scott Chesworth/by Structural Integrity

By: Scott Chesworth (SI) and Bob Grizzi (EPRI)

The goal was to determine whether the frequency of current inspection requirements was justified or could be optimized (i.e., increase the interval of certain inspections to devote more attention to higher-value inspections and thereby maximize overall plant safety).

Executive Summary
Welds and similar components in nuclear power plants are subjected to periodic examination under ASME Code, Section XI. Typically, examinations are performed during every ten-year inspection interval using volumetric examination techniques, or a combination of volumetric and surface examination techniques. Nuclear plants worldwide have performed numerous such inspections over plant history with few service induced flaws identified.

News & Views, Volume 48 | Fatigue Adjustment Factors for Increased Cyclic Life

September 30, 2020/in Bill Weitze, Fracture Mechanics, News and Views, Nuclear Asset Integrity, Nuclear Energy/by Structural Integrity

By: Bill Weitze

100% of thermal stress was treated as nonlinear gradient stress and linear bending stress was about 12% of the moment stress. Structural Integrity’s (SI’s) review of the stress terms used in piping analysis show that pressure stress does create bending stress in components…

EPRI Report 3002014121 “Development of Fatigue Usage Life and Gradient Factors” has developed fatigue usage adjustment factors that account for: 1) increased cyclic life associated with the growth of potential engineering size fatigue cracks in thicker components (thickness factor, TF; also called life factor, LF), and 2) the presence of through-thickness stress gradients (gradient factor, GF). (TF is used in the issued Code Case.) These factors are applied to cumulative usage factor, U, in air.

News & Views, Volume 44 | Data Driven Solutions for the Most Difficult Problems

April 27, 2018/in Andrew Crompton, Fracture Mechanics, Mark Jaeger, News and Views, Nuclear Asset Integrity, Nuclear Energy, Vibration/by Structural Integrity

By: Andrew Crompton and Mark Jaeger

In recent years, SI has observed an increasing trend in the use of specialty instrumentation to solve “impossible” problems or answer “indecipherable” questions. This shift was particularly apparent within commercial nuclear, where data-driven solutions have long been perceived as challenging due to short outage windows, personnel dose concerns, and a significant paperwork burden, among other factors. Widespread adoption of instrumentation-based solutions creates new paths to tackling difficult/persistent problems, and shifts the industry focus for critical assets from reactionary to more of a predictive approach. In 2017, SI assisted numerous clients with deployment of specialty instrumentation in this fashion, comprising two general scenarios: 1) new designs/modifications, and 2) repeat failures. Each application requires different sensors and varying analytical methods, but the approach used to leverage the resultant data to solve the problem is generically applicable throughout the energy sector. The text below details important considerations for both scenarios and highlights a successful application of the underlying process for management of thermal fatigue in reactor coolant system branch piping.