ML20151A290
| ML20151A290 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/04/1988 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| TAC-R00335, TAC-R00336, TAC-R335, TAC-R336, NUDOCS 8804060427 | |
| Download: ML20151A290 (5) | |
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TENNESSEE VALLEY AUTHORITY l
CHATTANOOGA, TENNESSEE 37401 5N 157B Lookout Place APR 041988 a
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U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555 Gentlemen:
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In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) UNITS 1 AND 2 - REQUEST FOR RELIEF FROM THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) SECTION XI CODE AS IT RELATES 10 SQN'S MICR0 BIOLOGICALLY INDUCED CORROSION (MIC) PROGRAM
Reference:
TVA letter to NRC dated January 20, 1988, "Sequoyah Nuclear Plant
[
(SQN) Units 1 and 2 - Microbiologically Induced Corrosion (MIC)
Program" During a March 18, 1988 telephone conference call between R. Herman of NRC and TVA management, NRC requested that TVA provide additional information to clarify a previous submittal regarding SQN's MIC Program.(referenced letter).
The additional information given in the enclosure is in the form of a relief request to the inspection requirement (IWA-5250) contained in the ASME Section XI Code, 1977 Edition, Summer 1978 Addenda.
This '.Jbmittal addresses NRC's concern for TVA's evaluation of Essential Raw Cooling Water (ERCW) piping following Identlft:ation of leakage caused by MIC.
TVA's MIC Program will ensure that structural integrity of SQN's ERCW piping is maintained and that compliance with the requirements of the SQN technical specifications is retained.
If you have any questions concerning this issue, please telephone M. R, Harding at (615) 870-6422.
1 Very truly yours, i
TENNESSEE VALLEY AUTHORITY
\\qv @
2 R. Grl ) y, Dire r
Nuclear Licensing and t
Regulatory Affairs Enclosure cc: See page 2 090 kl i
8804060427 880404 PDR ADOCK 05000327 An Equal opportunity Employer i
. DCD R
U.S. Nuclear Regulatory Commission J4PR 041988 j
cc (Enclosure):
j Mr. K. P. Eirr, Acting Assistant Director for Inspection Programs TVA Projects Division U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. G. G. Zech, Assistant Olrector for Projects l
TVA Projects Olvision U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike
-2 Rockville, Maryland 20852 I
Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road i
Soddy Daisy, Tennessee 37379 i
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o ENCLOSURE RELIEF REQUEST--ESSENTIAL RAW COOLING WATER (ERCW)
MICR0 BIOLOGICALLY INDUCE 0 CORROSION (MIC)
COMPONENT:
ERCW piping, SQN units 1 and 2 4
CLASS:
ASME Code Class 3 (equivalent), TVA Safety Class C FUNCTION:
Provide cooling water to a variety of components required for safe shutdown of the unit.
INSPECTION REQUIREMENT:
IWA-5250(a)(2):
"The source of leakage detected during the conduct of a system pressure test shall be located and evaluated by the owner for corrective measures as follows:
repairs or r
l replacements of components shall be performed in accordance with IWA-4000 or IWA-7000, respectively." (ASME Section XI, 1977 Edition, Summer 1978 Addenda)
BASIS i
FOR RELIEF:
Relief is requested from above inspection requirement for immediate repair or replacement of ERCH piping following identification of MIC-induced throughwall piping leakage.
The MIC Program provides for an analytical evaluation process to determine the structural integrity of the ERCH piping system. A satisfactory structural evaluation of welds with MIC-induced leakage allows continued operation of the affected unit and defers repair and replacement until the next available outage.
This will allow TVA to perform repair or replacement of ERCH piping in an orderly manner by providing adequate preplanning and reducing anticipated personnel exposure.
l The basis for this relief 1s taken from TVA's submittal to NRC on the MIC Program dated January 27 1988.
"1.
The ERCH piping can tolerate extensive damage without l
compromising its ability to retain structural integrity throughout a seismic event.
To date, the damage associated with these welds has not been found to encroach on 4
structural integrity.
This has been substantiated by radiographic (RT) evaluation and structural analysis of 61 welds which determined that significant structural margin j
existed based on original design allowables.
The critical j
flaw size used to evaluate new leaking welds is a conservative value determined for worst case stresses.
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The low leakage rates associated with this damage are readily tolerated by the system w'thout affecting operability. Leakage identified by inspection must be corrected in a timely manner but does not affect the status of the operating unit (s).
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3.
Although calculattors have demonstrated that the effects of water leakage resulting from this damage during a seismic event are insignificant, electrical equipment required to shut down the unit (s) during a seismic event has been protected by booting the welds in the established leakage zone.
In summary, the identification of a leak does not require l
that the system (or loop) which has experienced the leakage event be considered inoperable or that a limiting condition for operation (LCO) be declared until the weld joint can be fully analyzed."
TVA will continue to comply with its ASME Section XI repair and replacement program when performing repairs or replacements to the ERCH piping system resulting from TVA's MIC Program.
ALTERNATE EXAMINATION:
The alternate criteria are taken from TVA's submittal to NRC on the MIC Program dated January 20, 1988.
"PMS 2220, 2221, 2222, and 2223 and TI-109 will be revised to state that, when a leak is discovered, the following actions will be taken:
l During Modes 5 and 6, a work request will be written to i
repair the damaged area, and that repair work will be a j
restart requirement.
During Modes 1, 2, 3, and 4, Technical Ir.struction (TI) 109, 'Non-Destructive Testing of Stain'ess Steel Butt-Welds to Assess Damage Resulting From Microbiological 1y Induced
. Corrosion (MIC),' will be used to evaluate the corrosion damage.
This instructior will t.o revised to specify that RT will be completed within seven days after leak discovery.
The RT data will be compared against a preestablished screening criteria.
If a weld is found with MIC damage that exceeds the screening criteria, that weld will receive further detailed seismic analysis within an additional seven days.
If the detailed seismic analysis determines a weld to be structurally inadequate.
l appropriate ERCW Technical Specification (TS) actions will l
be taken.
Sequoyah experience indicates that all welds will be within the screening criteria and, therefore, TS actions should not be required.
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... ' If the weld is considered to be structurally sound, the leakage t
from the weld is insignificant (i.e., 'haracterized as a weeper or does not pose a personnel hazard), and does not have the potential for leaking on safe shutdown equipment.
The leak will be scheduled for repair 4t the next available nutage. The weld will be entered into a monitoring program under PH 2240 and 2241 to monitor any type of MIC growth.
This process will be implemented in the revision to TI-109.
The plant management may, at their discretion, elect to put the system into an outage and repair the leaking joint rather than perform radiography."
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