ML20064B606
| ML20064B606 | |
| Person / Time | |
|---|---|
| Site: | Mcguire |
| Issue date: | 10/09/1990 |
| From: | Tucker H DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-009, IEB-88-9, NUDOCS 9010180173 | |
| Download: ML20064B606 (3) | |
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- Duke har Compa:y :
HMRTune-PO Bu33198 nce President -
~ Charlotte. NC 28242 Nuclear Mduction -
(704)373 4531 DUKE POWER '
October 9, 1990 U. S. Nuclear Regulatory Commission A'ITN: Document Control Desk Washington, D.C.-
20555
Subject:
McGuire Nuclear Station, Unit 2 Docket Number 50-370 4
Change in Commitment to Perform Eddy-Current-Testing =
1 NRC Bu11etin'88-09 requested that Licensees establish and implement inspection programs to periodically confirm incore neutron monitoring-system thimble tube integrity.
Accordingly.-Duke performed oddy current testing (ECT) at McGuiro Unit 2 during the end-of-cycle _(EOC) 5 refueling outage.
(July, 1989), and committed (
Reference:
letter, September 7, 1989,-from
1990).
At that time Westinghouse, who performed the ECT, applied a-10%-
uncertainty on the ECT process. This uncertainty was a factor in the decision to raexamine the thimble tubes at E0C 6.
Westinghouse has been working on an-Owners Group Project which will_ yield more facts about the actual wear and its measurement.- Based!on'the preliminary results of this study,_ Westinghouse has determined.that the.
method they use to cddy current is always conservative.in-this particular application. This information allowed Duke Power to remove the 10%
uncertainty in its calculation for reexamination.,. Based on this information, Duke has recalculated the McGuire 2 wear prediction-(see attachment). Due.to the varying lengths-of a fuel cycle. this new prediction used days of reactor coolant pump operation (Modes 1-4) to estimate wear instead of>the number of-cycles of operation. This will be more accurate since the wear only occurs when the pumps are operating. The new predictionshows that the thimbles should be reexamined at the EOC-8 (first quarter of 1993) instead of at the EOC-6.
This prediction may be updated again once the Westinghouse Owners-Group Report is released. The number of days of operation at Mode 4 (or higher) will be verifled each cycle to be conservative with respect.to the estimated values in the attachment.
If there are any questions, please call Scott Gewehr at (704) 373-7581.
Very truly yours, W
Hal B. Tucker SAC /237/lcs 9010180173 901009
/
PDR-ADOCK 05000370 g/[.
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'Uc-S. Nuclear Rigulatcry Commis ion October 9,~1990:
Page-2 cci Mr. S. D. Ebneter, Regional Administrator-1 U. S. Nuclear Regulatory Commission - Region II' 101 Marietta Street ~,1NW - Suite 2900 i
Atlanta, Georgia. 30323 Mr.- Tim A. Reed,' Project Manager Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission.
One White-Flint North, Ma11 Code 9H3 Washington.,D.C.
20555-Mr. P. K..VanDoorn anior Resident; Inspector McCulte Nuclear' Station =
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ATTACHMENTL McGUIRE UNIT 2.
TIMING FOR NEXT ECT The first Eddy Current < Test (ECT) aas performed at.McGuire Unit 2 at EOC 5;'a total of.2128-days of' operation'in Modes 1-4"(reactor coolant pumps operating). The maximum wear accumulated:during that time was'33% through 1
wall wear. This results'in an-average wear rate'(WR).of '.01551%/ day..
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The table below relates the number of days-offoperation in Modes 1-4 to:the number of effective full power' days (EFPD)Lin each cycle.
No. of Days Cycle In Modes 1-4
- EFPD Ratio ~
-11 653-
~378 1.7 2'
.358-248 1.41 3
362 268 1.4
-4 368' 308 L1. 2 5
'387-
.322 1.2:
Cycle 1 can be discounted as having an abnormally.high ratio of days in Modes 1-4 to EFPD.- The average ratio of Cycles,2-5 is l.3.. Therefore, toa calculate the number of. days'of operation which may be. expected, for the-purpose'of estimating thimble tube wear. the des'ign cycleLlength'(EFPD)lis i
multiplied by the historically-derived ratio [(1.3).
Design ~-
^
Cycle EFPD*
EFPD x 1.3 Cumulative Days 6
340 442 442:
1 7
370~
-481 923' 8
402 523-
-1446'
+
9 402 523-
'1969
- Including + 10-Day Window.
1 To determine at what point the wear will exceed the' maximum' wall-loss acceptance criterion given in. Duke's response to Bulletin 88-09 (60% hrough-wall):
60% - 33%
= 1740.8 Days i
.01551 %/ Day
.,:r Comparing this number to the " Cumulative Days" column in the table ab'ove,;it can be determined that the next ECT shouldL be performed' during the EOC 8 p.
outage, unless the ratio of days of operation in Modes 1-4 to EFPD increases.
The number of actual days of Modes.1-4 operation will.be' verified after each
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cycle.
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