Sub-Critical Crack Growth and Structural Integrity of Light Water Reactor

High temperature water environments, typical of light water reactor primary coolant, are known to lead to significant environmental enhancement of fatigue crack growth of austenitic stainless steels. For PWR environments. these effects have recently been codified in ASME Code Case N-809. However, just as for the detrimental effect of these environments on fatigue endurance, plant experience indicates that crack growth rates must be significantly lower than predictions based on laboratory data using simple sawtooth waveforms. In order to explain this discrepancy, a significant amount of research has been conducted to quantify factors leading to crack growth rate retardation with sulfur content having been identified as significant in promoting crack growth rate retardation. However, the inherent conservatisms in current analysis techniques may be just as significant in generating the perceived over-conservatism of environmental fatigue crack growth laws such as Code Case N-809. The current work looks at the impact of waveform shape and spectrum loading on the level of environmental enhancement for a given stress intensity factor range and total rise time by considering simplified transients and loading spectra. The observations suggest that simplified definitions of total rise time used in fatigue assessments can lead to large over-estimation of actual fatigue damage. These data form the basis of an analytical methodology being developed by RollsRoyce (presented in a separate paper at this conference) aimed at partitioning damage across the loading cycle in order to remove over-conservatisms in current analytical methodologies.

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Light water reactor structural integrity

Annals of Nuclear Energy ◽

10.1016/0306-4549(85)90110-0 ◽

1985 ◽

Vol 12 (5) ◽

pp. 267

Author(s):

Y. Bangash

Keyword(s):

Structural Integrity ◽

Light Water Reactor ◽

Light Water ◽

Water Reactor

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Inspection and Evaluation Guidelines for Light Water Reactor Core Internals in Japan

Service Experience and Failure Assessment Applications ◽

10.1115/pvp2002-1174 ◽

2002 ◽

Cited By ~ 1

Author(s):

Kimihito Takeuchi ◽

Naoto Iizuka ◽

Masashi Kameyama ◽

Haruo Fujimori ◽

Yuichi Motora ◽

...

Keyword(s):

Nuclear Power ◽

Structural Integrity ◽

Reactor Core ◽

Light Water Reactor ◽

Light Water ◽

Water Reactor ◽

Integrity Assessment ◽

Engineering Society ◽

Safety Function ◽

Internal Component

There have been many cracking experiences of light water reactor (LWR) core internals worldwide in the past. Thermal and Nuclear Power Engineering Society in Japan (TENPES) has organized a committee to prepare technically reasonable and appropriate inspection and evaluation guidelines (I&E guidelines) for core internals. This committee consists of scholars and representatives from electric utilities and nuclear plant vendors in Japan. I&E guidelines, which cover a rational inspection plan, structural integrity assessment and repair methods, have been developed considering nuclear safety function and structural strength of each core internal component. For BWR reactors, the development of I&E guidelines cover major core internal components like shroud support, core shroud, top guide, core plate, ICM and CRD housing, core spray piping and sparger, jet pump etc. For PWR reactors, the development of I&E guidelines cover baffle former bolts, barrel former bolts, core barrel weld, bottom mounted instrumentation, etc. The I&E guidelines will be completed by the end of March 2002. The basic concept of the guidelines, and a guideline for shroud support of a BWR as an example, are shown in this paper.

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