ML20244E408
| ML20244E408 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 06/12/1989 |
| From: | Michael Ray TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-89-001, IEB-89-1, NUDOCS 8906200321 | |
| Download: ML20244E408 (7) | |
Text
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TENNESSEE VALLEY AUTHORITY -
,7 5N 157B Lookout Place JUN 121889 U.S. Nuclear. Regulatory Commission ATTN: Document Control Desk
' Washington, D.C.
20555 1
Gentlemen:
]
In the Matter of.
)
Docket Nos. 50-327 Tennessee Valley Authority
)
50-328 j
i SEQUOYAH NUCLEAR PLANT (SQN) - NRC BULLETIN'89-01: FAILURE OF WESTINGHOUSE l
STEAM GENERATOR TUBE MECHANICAL PLUGS i.
Thik letter provides the TVA response to the subject bulletin. As identified in the bulletin', the " actions requested" apply to four heat. numbers of material that have been determined to be susceptible to primary water stress corrosion cracking. Of the 126 plugs installed in SQN Unit 1, 100 are from l
one' susceptible heat of material (heat No. 4523).
SQN. Unit 2 does not have l
any of the affected heat numbers in service.
t Enclosures 1 and 2 provide a detailed response to each action requested by the bulletin. A list of commitments for each unit (Enclosures.3 and 4) is also included.
i If there are any questions concerning this issue, please telephone l
W. C. Ludwig at (615) 751-8087.
Very truly yours, TENNESSEE VALLEY AUTHORITY t
n 0
% -}q Maneg.,NuclearLIcensing l
l and Regulatory Affairs Enclosures cc: See page 2 i
fg p
C C
00 An Equal Opportunity Employer
,U.S. Nuclear Regulatory Commission i
l cc (Enclosures):
Ms. S. C. Black, Assistant Director for Projects TVA Projects Division U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. B. A. Wilson, Assistant Director for Inspection Programs TVA Projects Division U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy Tennessee 37379 1
l Eaclosure 1 SQN Unit 1 Response SQN Unit 1 presently has 126 Westinghouse Electric Corporation mechanical tube plugs installed as detailed in Table 1.
As noted from Table 1, 100 of the 126 plugs are from a susceptible heat of material (heat No. 4523). The following is a direct response to each action requested in Bulletin 89-01 for the 100 susceptible plugs from heat No. 4523:
Action 1:
TVA has reviewed the information for SQN contained in References 1 and 2 of the bulletin. Corrections to this information have been verbally transmitted to Westinghouse. Table 1 reflects corrected l
information.
Action 2a: The expected life of the susceptible plugs has been calculated based on bulletin References 1 and 2 using the Millstone Nuclear Plant Unit 2 growth rate, and this information is contained in Table 1.
As shown in Table 1,.SQN Unit 1 plugs have a minimum margin of 52 days from the next refueling outage.
Action 2b: TVA will replace and/or repair the 100 Westinghouse plugs before the calculated end of life as illustrated in Table 1.
TVA also conservatively plans to remove all Westinghouse Inconel 600 plugs regardless of heat number at the next refueling outage (Cycle 4).
However, unforeseen factors such as equipment problems, as low as reasonably achievable (ALARA) concerns, schedule constraints, and/or Row 1 divider plate equipment interference may render this conservative plan unfeasible.
Action 2c: TVA is firmly committed to the ALARA concept, particularly in regard to steam generator maintenance. TVA makes every effort to perform all steam generator maintenance activities without personnel entry into the steam generator plenums, as evidenced by the successful completion of remote nozzle dam installation during the SQN Unit 2 Cycle 3 refueling outage. This effort was accomplished using equipment that was desi ned and developed by 6
TVA at a considerable man-rem dose savings.
In keeping with our ALARA philosophy, every attempt will be made to complete the remedial actions with a minimum of personnel radiation exposure.
Action 2d:
Installation of Westinghouse steam generator tube plugs made from the susceptible heats listed in the bulletin has been discontinued.
Procedures will be revised to preclude the installation of ste.am generator tace plegs nede from incone). 600 material.
Action 2e: A representative c. ample of Westinghouse Inconel 600 mechanical plugs removed frem service (regardless of heat number) will be exarined for primary water stress corrosion cracking, and the results will be submitted to Westinghouse.
Action 3:
Does not apply since tha SON tubes are ful.1-depth expanded into the tubesheet.
Action 4:
Does not apply since SQN does not have any sentinel plugs installed.
l.
~
SON Unit 2 Response SQN Unit 2 presently has two Westinghouse mechanical tube plugs installed as detailed in Table 1.
As noted from Table 1, neither of the plugs is from a heat of material identified as susceptible in the bulletin. Therefore, the bulletin requirements do not apply to SQN Unit 2, with the exception of Action 2e.
Action 2e: Although TVA is not required to remove the Unit 2 plugs, we conservatively plan to remove both of the Westinghouse mechanical plugs at the next refueling outage (Cycle 4) if feasible. These plugs will be examined for primary water stress corrosion cracking when removed, and the results will be submitted to Westinghouse.
l
+ '
SON Unit 1 List of Commitments 1.
TVA will replace and/or repair the 100 susceptible SQN Unit 1 Westinghouse mechanical plugs before the time at which the calculated lifetime of the plugs is exceeded. Before implementing any repair method (other than removal / replacement). NRC will be notified and justification provided.
2.
Procedures will be revised to preclude the installation of steam generator tube plugs made from Inconel 600 material.
3.
A representative sample of Westinghouse Inconel 600 mechanical plugs removed from service (regardless of heat number) will be examined for primary water stress corrosion cracking, and the results will be submitted to Westinghouse.
1 l
l l
SgN Unit 2 List of Commitments 1.
If'the two Westinghouse mechanical plugs are removed, they will be examir.ed for primary water stress corrosion cracking, and the results will
.be submitted to Westinghouse.
2.
Procedures will be revised to preclude the installation of steam generator tube plugs made from Inconel 600 material.
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