PNO-II-97-023B, on 970422,extended Shutdown for Oconee Units 2 & 3,update Made.Currently,Licensee Developing Justification for Continued Operation of Unit 1 Based on Different Designed Thermal Sleeves Installed in Unit 1
| ML18040A002 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/02/1997 |
| From: | Carroll R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| References | |
| FACA, PNO-II-97-023B, PNO-II-97-23B, NUDOCS 9705020294 | |
| Download: ML18040A002 (6) | |
CATEGORY j.
REGULATO INFORMATION,DISTRIBUTION TEM (RIDS)
ACCESSION NBR:9705020294
"'OC.DATE: 97/05/02 NOTARIZED:
NO DOCKET FACIL 50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 50-270 Oconee Nuclear Station, Unit 2, Duke Power Co.
05000270 50-287 Oconee Nuclear Station, Unit 3, Duke Power Co.
05000287 AUTH.NAME AUTHOR AFFILIATION CARROLL,R.
Region 2 (Post 820201)
RECZP.NAME RECIPIENT AFFZLIATION
SUBJECT:
PNO-II-97-023B:on 970422,extended shutdown for Oconee Units 2
& 3,update made. Currently, licensee developing justification for continued operation of Unit 1 based on different designed thermal sleeves installed in Unit l.
'DISTRIBUTION CODE:
ZE34F COPIES RECEIVED:LTR ENCL SIZE:
TITLE: 50 Docket
& Vendors PNO/Non-Routine Event/Safeguards Event (PN)
NOTES:
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NRC PDR NOAC NOTE TO ALL "RIDS" RECIPIENTS:
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PRELZMX PNO-II-97-023B
@This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance.
The information is as initially received without verification or evaluation, and is basically all that is known by Region II staff in Atlanta, Georgia on this date.
~Facilit Duke Power Co.
Oconee 2
Seneca, South Carolina Dockets:
50-270 Licensee Emer enc Classification Notification of Unusual Event Alert Site Area Emergency General Emergency X Not Applicable
Subject:
EXTENDED SHUTDOWN -
OCONEE UNITS 2 AND 3 (UPDATE)
This is the second update to the April 22,
- 1997, Oconee Unit 2 shutdown due to an unisolable reactor coolant system (RCS) leak from a cracked weld on the.pipe end in the transition piece (safe-end) between the high pressure injection (HPI) line and the 2A1 reactor coolant loop nozzle.
1ndependent laboratory analysis has indicated that thermal stress caused the weld crack, which was nearly 270 degrees and 30 percent through wall except at the top 30 degrees where the leak emanated.
This failure has been attributed to a gap which developed between the safe-end and the rolled area of the nozzle thermal sleeve.
The licensee believes that the safe-end was subjected to thermal fatigue cracking as it was alternately heated (by hot reactor coolant randomly flowing around the thermal sleeve up through the gap) and cooled (by the cooler normal makeup flow through the associated HPI line).
This phenomenon was identified as the probable cause for similar safe-end cracking observed at B6W plants (including Oconee) in the early 1980's, prompting augmented non-destructive examination (NDE) to detect cracking in the area of the safe-end, as well as.to identify the development of a gap in the rolled area of the nozzle thermal sleeve.
Review of radiographs made in April 1996 of the 2A1 safe-end revealed that the licensee failed to identify the gap which developed in the rolled area of the thermal sleeve.
Accordingly, the licensee reviewed radiographs made in November 1996 of the 3A1 safe-end in Unit 3, since it too contained an originally installed nozzle thermal sleeve like 2Al.
The review indicated that a gap also existed in the rolled area of the 3Al thermal sleeve.
As a result, Unit 3 was shutdown at:7:28 a.m.,
on May 2, 1997.
Currently, the licensee is developing a justification for continued operation of Unit 1 based on the different designed thermal sleeves installed in Unit 1, higher makeup flows through the sleeves, and increased sensitivity to RCS leakage.
Replacement of the 2Al safe-end and thermal sleeve are being performed by Framatome.
NDE recently performed in the areas of the other three Unit 2 HPI safe-ends did not reveal problems similar to 2A1.
The licensee plans to continue the cooldown of Unit 3 in order to conduct NDE of the areas of concern.
NRC resident inspectors, in conjunction with a Region II NDE inspector, have been monitoring the licensee's recovery activities since the Unit 2 event.
To assist in the continued followup of these activities, they 9705020294 970502 PDR ISE PNQ-K I-97-023B PDR
0
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~
VC Swill be, supplemented with another inspector from Crystal River.
In the generic aspects of the Oconee Group.
Region II NDE inspector and a resident
- addition, the NRC staff has discussed Unit 2 failure with the BRW Owners The State of South Carolina has been notified.
The licensee is prepared to respond to any media inquiries, but no press release is planned.
This information is current as of 11:00 a.m.,
on 'May 2, 1997.
Contact:
CARROLL (404)331-5543
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