05000206/LER-1981-008, Forwards LER 81-008/03X-0.Detailed Event Analysis Also Submitted

Forwards LER 81-008/03X-0.Detailed Event Analysis Also Submitted

ML20009A208
Person / Time
Site:	San Onofre
Issue date:	06/23/1981
From:	Haynes J SOUTHERN CALIFORNIA EDISON CO.
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20009A209	List: 05000206/LER-1981-008, Forwards LER 81-008/03X-0.Detailed Event Analysis Also Submitted 05000206/LER-1981-008-03, /03X-0:on 810504,insp of Thermal Sleeve & Feedring Assembly on Steam Generator B Found Thermal Sleeve Deformation in Feed Nozzle Area,Radial Indications at Several Feedring Distribution Holes & Other Defects
References
NUDOCS 8107090236
Download: ML20009A208 (2)

LER-1981-008, Forwards LER 81-008/03X-0.Detailed Event Analysis Also Submitted

Event date:
Report date:
2061981008R00 - NRC Website

text

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MJ U. S. !!uclear Pegulatory Comission

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Mr. P. H. Engelken, Director

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Dear Sir:

This letter describes an occurrence involvino the discovery of defects in the themal sleeve and feedring assembly in the "B" Stean Cenerator. A License Event Peport Fo.81-008 is nnclosed.

In accordance with Festingt ouse l'uclear Service Division Radar Response SCEJ0-52, Steen Cenerator Themel Sleeve Defomation, an inspection was perfomed on the themal sleeve and feedring assemblies in the A, B, and C steam cenerators in April and l'ay nf 1981.

Mo defects were observed in the themal sleeve and feedring asserbly in the A and C s; am generators.

In the B stean generator, the following conditions were observed:

Padial linear indications at several feedrina distribution holes.

Themal sleeve defomation in area of the feed nozzle.

Linear indications on each side of the sleeve tee to feedring weld.

Feedrinn "U" support defomation and linear indications at the "U"

support weld to bracket.

Cebris (two retal gaskets, one nut and retal frarents) in the feedrina.

Uestinghouse has cerforred a fatigue life analysis on the stean cenerator feed nozzle.

It bas been deterrined that there is sufficient fatigue life remaining to pemit safe operation throuah the next refueling cycle. Additional analyses are nianned to detemine if continued use of the nozzle throuch the remaining plant life is acceptable.

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l l 8107090236 810623

'"PDR ADOCK 05000206 Jf MT PDR

1. 1 U. S. Nuclear Regulatory Commission Pa ge i 2 s

Fracture mechanics analysis was performed on the distribution holes.

Any propagation due to a water hammer event would be longitudinal and not radial indicating that failure of the feedring would not occur from these cracks. Repair was deemed unnecessary.

Corrective action for the remaining defects was completed May 25, 1981 and consisted of the following:

Linear indication on the west side of the sleeve tee to feedring was removed and the joint weld repaired. Approximately 90% of the linear indication on the east sioe of the sleeve tee was removed and the joint weld repai red. Neither indication was through wall. A fracture mechanics analysis was performed to verify the integrity of the weld repairs for steam bubble collapse water hammer and service conditions.

New "u" supports were installed.

The debris were removed from the feedring except for the nut, which was tack welded in place.

The cause of the thermal sleeve deformation is attributed to water hammer. The water hanner caused the sleeve to expand reducing the radial gap between the sleeve and generator wall. Radial indications at the feecring distribution holes are attributed to a stripping phenomenon caused by localized thermal cycling. The indications at sleeve tee to feedring are attributed to flow induced vibration. Deformation of the "U" supports has been identified as a potential factor in the vibration mechanism.

It is suspected that the debris found in the feedring was f rom a deteriorated flow straightener replaced last year.

Information concerning our corrective measures designed to minimize the possibility of future water hammer events has been previously transmitted to you.

"1 sed upon the above repairs and analysis, there will be no effect upon public health or safety in returning the unit to service. Prior to completion of the next refueling outage, long term corrective measures (if necessary) for the feedwater nozzle thermal sleeve will be established.

Sincerely, i

J. G. Haynes Manager of Nuclear Operations MJS : dh : 69'J cc:

L. F. Miller (NRC Site Inspector - San Onof re Unit 1)