Overview of Steam Generator Tube Degradation and Integrity Issues

Course Summary:

The degradation of steam generator tubes in pressurized water nuclear reactors, particularly by stress corrosion cracking mechanisms, continues to be a serious problem. Primary water stress corrosion cracking is commonly observed at the roll transition zone at U-bends, at tube denting locations, and occasionally in plugs and sleeves. Outer-diameter stress corrosion cracking and inter granular attack commonly occur near the tube support plate crevice, near the tube sheet in crevices or under sludge piles, and occasionally in the free span. A particularly troubling recent trend has been the increasing occurrence of circumferential cracking at the RTZ on both the primary and secondary sides.

This course summarizes on the principal-corrosion-related degradation processes observed in steam generator tubing and provides the basis for the philosophy behind the new steam generator rule and Regulatory Guide.

Learning Objective:

• Introduction
• Corrosion Problems in Steam Generator Tubing
  • Primary Water Stress Corrosion Cracking
  • Outer Diameter Stress Corrosion Cracking
  • Circumferential Cracking at the RTZ and Dented TSPs
• Reliability of Detection and Sizing of Flaws
• Performance-Based Steam Generator Rule and Regulatory Guide
• Summary of Research Needs

Review the quiz before studying the course.

Course Content

Course Author: USNRC