ML20128H435
| ML20128H435 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 10/01/1996 |
| From: | Mcmeekin T DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9610090341 | |
| Download: ML20128H435 (5) | |
Text
l Il I
Dukeibwer Company T C McMrIrs 8
McGuire Nuclear Generatwn Department Vice President 12iOOHogeg FenyRoad(MG0lVP)
(704)8754800 1funtersville, NC28078h985 (704)8754809 Fax DUKEPOWER October 1, 1996 Document Control Desk U.S.
Nuclear Regulatory Commission Washington, D.C.
20555
Subject:
McGuire Nuclear Station Docket Nos: 50-369 and 370 IS 3/4.4.6.2, Operational Leakage Steam Generator Primary to Secondary Leakage Administrative Limit for Unit Shutdown The current McGuire Technical Specification limit on steam generator leakage is 500 gallons per day (GPD) per steam generator.
In 1992, McGuire implemented an administrative shutdown limit of 50 gallon per day (GPD) per steam generator for primary to secondary leakage for McGuire Unit 1 Cycel 8.
In subsequent discussions and meetings with NRC personnel, the 50 GPD administrative limit was extended and made applicable to both McGuire units.
Also, McGuire implemented enhanced monitoring procedures and installed N-16 detectors on each Main Steam line.
Current EPRI guidelines recommend a shutdown criteria of 150 GFD.
NRC Generic Letter 95-05 also suggests a Technical Specification limit of 150 GPD.
This letter serves as notification that the subject steam generator leakage administrative limit has been changed to 100 GPD per generator. The technical justification to support this NRC commitment change is attached.
In addition, the EPRI shutdown guideline of 60 GPD/hr rate of change has been implemented.
Old[iG7 I
9610090341 961001 PDR ADOCK 05000369 p
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US Nuclear Regulatory Commission October 1, 1996 Page 2 McGuire steam generator tube leakage history since 1992 is as follows:
Date Unit SG Leakage Shutdown required GPD
@ 50 GPD?
@ 100 GPD?
i 1/92 1
235 YES YES l
8/93 1
200 YES YES 1/94 1
126 YES YES The updated 100 GPD criteria, had it been in effect, would have also resulted in unit shutdown for all three cases listed above.
If you require further information, please contact James E.
Snyder at (704) 875-4447.
Very truly yours, 7(ADL u-T.
C. McMeekin l
l
~
i U.
S. Nuclear Regulatory Commission October 1, 1996 Page 3 l
Xc.
Mr.
S.
D.
Ebneter
)
Administrator, Region Il U.S.
Nuclear Regulatory Commission 101 Marietta St.,
NW, Suite 2900 Atlanta, Ga. 30323 Mr. Victor Nerses i
U.S.
Nuclear Regulatory Commission l
Office of Nuclear Reactor Regulation (14H25)
)
Washington, D.C.
20555 l
Mr. Peter S.
Tam U.S.
Nuclear Regulatory Commission Office of Nuclear Reactor Regulation l
Washington, D.C.
20555 l
Mr. Scott M.
Shaeffer NRC Senior Resident Inspector McGuire Nuclear Station Mr. Dayne Brown, Chief Division of Radiation Protection P.
O.
Box 27687
- Raleigh, N.
C.
27611-7687 1
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McGuire Nuclear Station Technical Justification for Increasing Administrative Limit for Primary to Secondary Leakage in Steam Generators As documented in the referenced correspondence, McGuire initially committed to a 50 gallon per day (GPD) shutdown criteria for steam generator (SG) primary to secondary leakage for the cycle 8 operation of McGuire Unit 1.
Steam generator leakage in excess of 50 GPD would result in unit shutdown.
In subsequent discussions and meetings with NRC personnel, the 50 GPD administrative limit was extended to a general commitment applicable to both McGuire units.
AJ a result of the adverse trend in SG tube reliability, McGuire committed to several SG tube inspection and monitoring enhancements which were implemented in 1992 and are now routine practice.
One of these enhancements included adding N-16 monitors to each Main Steam line.
The addition of these monitors provides an early warning indication of a SG tube leak.
These enhancements have been very successful in improving SG leakage detection.
An administrative shutdown limit of 100 GPD per steam generator or a step change of 60 GPD/ hour better addresses the current state of degradation in the steam generators. Such degradation l
includes hot leg tubesheet PWSCC and hot leg tube support ODSCC.
l Leak rates that exhibit step change of 60 GPD/ hour require unit shut down.
McGuire steam generator tube leakage history since 1992 is as follows:
Date Unit SG Leakage GPD Shutdown required
@ 50 GPD?
@ 100 GPD?
1/92 1
235 YES YES 8/93 1
200 YES YES 1/94 1
126 YES YES The updated 100 GPD criteria, had it been in effect, would have also resulted in unit shutdown for all three cases listed above.
1 1
McGuire Nuclear Station Technical Justification for Increasing Administrative Limit for Primary to Secondary Leakage in Steam Generators Page 2/2 The SG tube plugging philosophy utilized at McGuire during refueling outage inspections concentrates on repairing corrosion degradation upon detection.
Data obtained by rotating pancake coil techniques are subjected to extensive engineering review.
The intent of this comprehensive review is to identify and repair precursor type signals that may indicate possible degradation.
This more conservative repair approach decreases the probability that small indications may rapidly propagate into more serious defects.
As a result of this aggressive repair strategy, both McGuire units have operated through four complete fuel cycles without a forced outage due to steam generator tube leaks.
References:
2/7/92 Duke Letter - Description of 1/13/92 Unit 1 SGTR 5/8/92 Duke Letter - McGuire Eddy Current Insp.
Plans 4/13/92 Duke Letter - Response to NRC Violation 92-05-01 6/1/92 Duke Letter - Revised Response to Viol.
92-05-01 9/23/92 Duke /NRC Meeting on MNS SG Tube Inspection Current EPRI guidelines NRC Generic Letter 95-05 2