Review of industry efforts to manage pressurized water reactor feedwater nozzle, piping, and feedring cracking and wall thinning
This report presents a review of nuclear industry efforts to manage thermal fatigue, flow-accelerated corrosion, and water hammer damage to pressurized water reactor (PWR) feedwater nozzles, piping, and feedrings. The review includes an evaluation of design modifications, operating procedure changes, augmented inspection and monitoring programs, and mitigation, repair and replacement activities. Four actions were taken: (a) review of field experience to identify trends of operating events, (b) review of technical literature, (c) visits to PWR plants and a PWR vendor, and (d) solicitation of information from 8 other countries. Assessment of field experience is that licensees have apparently taken sufficient action to minimize feedwater nozzle cracking caused by thermal fatigue and wall thinning of J-tubes and feedwater piping. Specific industry actions to minimize the wall-thinning in feedrings and thermal sleeves were not found, but visual inspection and necessary repairs are being performed. Assessment of field experience indicates that licensees have taken sufficient action to minimize steam generator water hammer in both top-feed and preheat steam generators. Industry efforts to minimize multiple check valve failures that have allowed backflow of steam from a steam generator and have played a major role in several steam generator water hammer events were not evaluated. A major finding of this review is that analysis, inspection, monitoring, mitigation, and replacement techniques have been developed for managing thermal fatigue and flow-accelerated corrosion damage to feedwater nozzles, piping, and feedrings. Adequate training and appropriate applications of these techniques would ensure effective management of this damage.
- Research Organization:
- Nuclear Regulatory Commission, Washington, DC (United States). Div. of Safety Programs; Idaho National Engineering Lab., Idaho Falls, ID (United States)
- Sponsoring Organization:
- Nuclear Regulatory Commission, Washington, DC (United States)
- OSTI ID:
- 464151
- Report Number(s):
- NUREG/CR--6456; INEL--96/0089; AEOD/E--97-01; ON: TI97005111
- Country of Publication:
- United States
- Language:
- English
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