ML20023A529
| ML20023A529 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Point Beach |
| Issue date: | 07/13/1978 |
| From: | Office of Nuclear Reactor Regulation |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19302F297 | List:
|
| References | |
| FOIA-82-309 NUDOCS 8210070208 | |
| Download: ML20023A529 (3) | |
Text
.,
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p g,13 HEMOPJdOUM FOR:
A. Schwen:er, Chief, Operating Reaetors Branch 1 DiYision of Operating Reactors FROM:
Acting Chief, Engineering Branch Division of Operating Reactors
SUBJECT:
POINT BEACH UNIT NO.1 - STEAM GENERATOR T1JBE LEAK Licensee Event Report No. 78-010/0lT-0 describes the discovery, on May 24,1978, of a steam generator tube leak at (145 GPD when plant was shutdown on May 25, 1978) in generator "A" of Point Beach Unit 1.
This LER is attached for information. The LER does not clearly indicate the exact elevation of the leak and states that the cause of the leakage has not been conclusively determined.
The location of the leaking tube (R44C58) indicates the possibility of a denting related crack.
Point Beach Unit 2 has experienced a denting related leak and ECT Probe restriction in this same wedge region. Additionally, operating experience at Turkey Point Units 3 and 4, which have similar steam generators, indicates that tubes in "hardspots" including uedged regions are susceptible to severe denting and it appears that the Point Beach units are following ';his same pattern.
Point Beach 1 has already had approximately 7% of the steam generator tubes plugged including some for denting related problems.
The unit has.also been forced to shutdown three times during the last 12 rnonths because of leaking steam generator tubes.
For the reasons discussed above, we feel it is necessary to request additional infomation of the licensee, as indicated in the enclosure.
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Or ital signed by:
Acting Cranch Chief
'N 821oo7o20e e2001o Engineering Branch
$NO9 Division of Operating Reactors PDR
Enclosure:
As stated
Contact:
R. LaGrange
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REQUEST FOR ADDITIONAL INFORMATION STEAM GENERATOR TUBE LEAK / DENTING W
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ENGINEERING BRANCH DIVISION OF OPERATING REACTORS 1.
With reference to the attachment to LER No. 78-010/0lT-0, the leak location in tube R44C58 is stated to be slightly above the level of the tube plate.
Clarify whether this means tubesheet or specify the exact elevation of the leak location.
2.
Tube location R44C58 appears to be in the eleven o' clock wedge region of the Model 44 steam generator.
The 1977 Annual Operating Report shows that two tubes in the eleven o' clock wedge region, locations R44C55 and R44C56, in "A" steam generator of unit 2 are plugged because of probe restriction and that R44C56 had been a leaker.
Experience at other operating units with similar Westinghouse steam generators (44 Series) indicate that severe tube denting is the cause of tube ID cracking in hardspots that in-clude wedge regions.
Because of the continuing concern over this issue, we request that you submit for comment your proposed steam generator inspection plan for the upcoming refueling outage of unit 1 and specifically address how the magnitude and extent of tube denting and support plate distortion (hourglassing, in-plane deformation) will be assessed.
Include your proposed plugging criteria for dented tubes and the basis for the establishment of the criteria.
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