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AUG 171977 1
L:_.:y MEMORANDUM FOR:
L. C. Shao, Chief. Engineering Branch Division of Operating Reactors FROM:
B. D. Liaw, Engineering Branch Division of Operating Reactors THRU:
R. J. Stuart, Section Leader, Engineering Branch Division of Operating Reactors
SUBJECT:
CRITERIA FOR DEFINING DEGREE OF STEAM GENERATOR TUBE DENTING In response'to your request, I have reviewed information on hand in the context of descriptive words used by Westinghouse,.and have discussed them with Dr. Dan Van Rooyen to come up with a set of criteria which can be used to classify the degree and extent of tube denting in PWR's.
In order to avoid any confusion, I suggest that we continue to use the three descriptive words; i.e., " extensive",'" moderate", and " minor" in Westinghouse's original submittal, and define them in accordance with actual occurrences in the steam generators. The following definitions are proposed to fit those descriptive words for the plant classification:
1.
Extensive Denting Presence of tube denting is widespread throughout whole steam a.
generator, and the average total reduction in tube diameter
. equals or exceeds twice the tube wall thickness.
b.
Measurable support plate in-plane deformation; such as hour-glassing of flow slots in Westinghouse plants.
c.
Has experienced leaky dents.
2.
Moderate Denting Presence of tube denting is widespread throughout whole generator.
a.
and the average total reduction in tube diameter exceeds 20% of the tube wall thickness.
1 b.
No measurable support plate it-plane deformation.
c.
Has not experienced leaky dent.
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3.
Minor Denting
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a.
Presence of tube denting is spotty to widespread, but the
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average total reduction in tube diameter is less than 20% of the tube wall thickness, b.
No visible support plate deformation.
c.
Has not experienced leaky dent.
4.
Plant Classification Based in above criteria, the fourtcen (14) operating plants anong 37 operating PWR's that have been confirmed to have tube denting are grouped as follows:
a.
Extensive (5 units):
- Surry Units 1 and 2 Turkey Point Units 3 and 4 San 0nofre Unit 1*
b.
Moderate (5 units): Millstone Unit 2 R. E. Ginna Unit 1 Point Beach Units 1 and 2 Indian Point Unit 2 c.
Minor (4 units):
- Maine Yankee Palisades Connecticut Yankee H. B. Robinson Unit 2
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O, O,f B. D. Liaw Engineering Branch Division of Operating Reactors cc:
D. Eisenhut (R. Stuart
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J. C. Guibert F. M. Almeter
- There is a question whether the leaking is. caused by denting or wastage.
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