ML17329A603
| ML17329A603 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 09/04/1992 |
| From: | Fitzpatrick E INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| AEP:NRC:1059D, NUDOCS 9209150040 | |
| Download: ML17329A603 (9) | |
Text
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DOCKET 5 05000315 05000316 ACCESSION NBR: 92091500OO DOC. DATE: 92/09/oe NOTARIZED:
NO FAOIL"':50-315 Donald C.
Cook Nuclear Poeer Plant> Unit 1> Indiana M
50-316 Donald C.
Cook Nuclear Poeer Plant> Unit 2>
Indiana M
AUTH. NAME AUTHOR AFFILIATION FITZPATRICK> E.
(formerly Indiana 5 Michigan Ele REC IP. NAME RECIPIENT AFFILlATION MURLEY> T. E.
Document Control Branch (Document Control Desk)
SUBJECT:
ForUJards results of eear insps of bottom-mounted instrumentation thimble tubes performed during 19'92 refueling outages. Total of 15 thimble tubes UJi1 1 be replaced during current Unit 1 refueling outage.
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1 NOTE TO ALL"RIDS" RECIPIENTS PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK.
ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!
TOTAL NUMBER OF COPIES REQUIRED:
LTTR 16 ENCL 13
Indiana hlichigan Power Company P.O. Box 16631 Columbus, OH 43216 AEP:NRC:1059D Donald C.
Cook Nuclear Plant Units 1 and 2
License Nos.
50-315 and 50-316 BOTTOM MOUNTED INSTRUMENTATION THIMBLE TUBE
'WEAR INSPECTION RESULTS U.
ST Nuclear Regulatory Commission Document Control Desk Washington, D.
C.
20555 Attn:
T, E. Murley September 4,
1992
Dear Dr. Murley:
This letter is to inform the NRC staff of the results of wear inspections of the bottom mounted instrumentation thimble tubes that were performed during the 1992 refueling outages at Donald C.
Cook Nuclear Plant Units 1 and 2.
Thimble tube wear was initiallyidentified as a problem at the Cook Nuclear Plant during the Unit 2
Cycle 6-7 refueling outage.
Subsequently, the NRC staff has been kept informed of developments in this area through meetings with the NRC staff in Rockville, Maryland and through the following letters:
AEP:NRC:1059, dated October 26, 1988; AEP:NRC:1059A, dated October 19, 1990; AEP:NRC:1059B, dated November 27, 1990; and AEP:NRC:1059C, dated July 15, 1991
'ncluded with this letter are summaries of the wear results from eddy current inspections of all thimble tubes that were examined during each unit's refueling outage in 1992.
Attachment 1 contains the wear summary from the eddy current inspection of the Unit 1 thimble tubes.
The Unit 1
inspection was performed on July 4, 1992.
Attachment 2 contains the wear summary from the eddy current inspection of the Unit 2 thimble tubes.
The Unit 2
inspection was performed on March 7, 1992.
As a result of the inspections, a total of 15 thimble tubes willbe replaced during the current Unit 1 refueling outage and a total of 22 thimble tubes were replaced during the recent Unit 2 refueling outage.
As committed to in letter AEP:NRC:1059C, these thimble tubes were or will be replaced with thimble tubes with a chrome plated coating at axial locations corresponding to the lower core 92091 50040, 920904 PDR 'DQCK )050003i 5 8
{
Dr. T. E. Murley AEP:NRC'1059D plate and fuel assembly lower nozzle area.
This area of the thimble tube typically receives the largest amount of wear.
The number of thimble tubes to be replaced was determined based on two criteria.
-First, all thimble tubes with active wear greater than or equal to 40t through-wall wear were replaced.
Second, all previously repositioned thimble tubes with active wear greater than or equal to 30% through-wall were replaced.
Active wear is defined as wear in an axial location that has changed since the last inspection, Repositioned thimble tubes after at least one operating cycle may contain active and inactive wear.
Inactive wear is identified as a wear scar that has been repositioned away from a-wear surface.
These criteria were chosen in order to allow significant conservative margin to wear based on previous analyses
- and, secondly, to place a reasonable amount of chrome plated thimble tubes in each unit to evaluate chrome plating effectiveness against wear.
Concerns about significantly degraded thimble tubes were balanced with concerns regarding installation of a previously proven product in a new application.
Specifically, although mock-up testing of the installed chrome plated thimble tube configuration indicated that thimble tube wear should be mitigated without introducing potential hot particles from the chrome plating, this application has yet to be proven in practice.
In response to these
- concerns, the full complement of thimble tubes (58 each unit) is not being replaced during the 1992 refueling outages.
Replacing only 15 thimble tubes in Unit 1 and 22 thimble tubes in Unit 2 with chrome plated thimble tubes results in a
limited number of thimble tubes being installed to in turn reduce the potential for chrome particles being introduced into the coolant.
However, this number of thimble tubes also represents a
reasonable number of thimble tubes to evaluate the effectiveness of the chrome plated thimble tube product in its intended application to mitigate wear.
Evidence of the success of a chrome plating application to mitigate wear has been witnessed at Cook Nuclear Plant Unit 1 on rod cluster control assemblies (RCCAs).
During the current Unit 1 refueling
- outage, a wear inspection was performed on all 53 Unit 1 RCCAs.
Eleven of these RCCAs are chrome plated and were installed for the first time during the previous refueling outage.
Preliminary results from the wear inspection showed no indications of wear after one cycle of operation, There is also no indication of increased concentrations of chrome particles in the reactor coolant.
Dr. T. E. Murley AEP:NRC:1059D After one cycle of operation, during the 1994 refueling outages, we will eddy current inspect each thimble tube in each
- unit, including the chrome plated tubes, to quantify the benefit of the chrome plating and to determine if additional hardware changes to further mitigate thimble tube wear are required.
As we have in the
- past, we plan to keep the NRC staff informed of any developments in this area.
Sincerely, E.
E. Fitz atrick Vice President dag Attachments CC>>
D. H. Williams, Jr.
A. A. Blind - Bridgman J.
R, Padgett G. Charnoff NFEM Section Chief A. B. Davis - Region III NRC Resident Inspector
- Bridgman
ATTACHMENT 1 TO AEP:NRC:1059D COOK NUCLEAR PLANT UNIT 1 CYCLE 12 THIMBLE TUBE WEAR
SUMMARY
Donald C. Cook Nuclear Plant Unit 1 C cte 12 Thimble Tube Wear Summ Maximum Previousl Re laced Thimble Core Active Wear C desof Re sitioned for Tube No.
21 28 45 43 46 49 34 55 53 20 54 52 50 35 39 36 17 27 14 10 33 26 47 48 29 56 16 30 37 22 24 57 31 18 19 12 58 13 41 38 40 32 25 15 42 44 51 Location J-7 E-11 N-13 K-6 H-15 D-14 J-8 H.2 N-14 R-11 E-5 H-6 J-10 F-7 A-11 L-15 R.6 B.8 G-5 J-14 G-12 L-8 H-3 A-9 P-4 F-8 N-6 N-2 M-7 F-3 P-9 K-12 H-13 G-9 D-12 H-11 L-5 E-9 B-13 L-10 D-10 N-4 K-2 F-14 L-13 D.S D-3 R-8 F-1
'/o Thru-Wall 84 45 38 38 36 35 34 33 32 31 30 27 26 24 24 23 22 22 20 18 18 17 12 10
<5
<5 88 53 48 44 35 35 34 34 30 29 29 28 28 27 26 26 25 24 23 22 19 19 19 12
<5
<5
<5 ration Thimbles Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No No No No No No No No No No No No No Ca ed C cfe13?
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No No No No No No No No No No No Yes Yes Yes Yes No No No No No No No No No No No No No No No No No No No No No No No
ATTACHMENT 2 TO AEP:NRC:1059D COOK NUCLEAR PLANT UNIT 2. CYCLE 8 THIMBLE TUBE WEAR
SUMMARY
A J
~
~
Donald C. Cook Nuclear Plant Unit 2 C cfe 8 Thimble Tube Wear Summ Maximum Previousl Re laced Thimble Core Active Wear C cfesof Re sitioned for Tube No.
Location H-2 34
% Thru-Wall 69 ration Thimble?
C cfe 9?
Yes Yes 21 35 20 25 54 42 30 51 18 44 15 40 23 22 12 48 45 24 26 49 46 39 36 52 57 53 58 43 13 56 17 27 55 29 41 16 32 37 50 19 14 10 33 28 31 47 38 E-11 E-5 N-8 A-11 D-3 F-3 F-1 F-7 G-9 R.8 D.8 F-14 D-10 K-12 E-9 P-4 N-13 H-13 H.3 D-14 K-6 J-10 J-14 L-15 G.5 H-11 R-11 B-13 H-15 L-10 N-2 G-12 N-14 N-6 N-4 M-7 L-13 P-9 R-6 L-5 H-4 L-8 J-7 D-12 A-9 K-2 J-8 63 61 61 53 53 52 43 39 32 31 28 18
<<5 67 55 51 47 45 44 42 42 41 39 33 32 32 27 24 24 24 21 20 18 16 16
<<5 42 27 16 13 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No No No No No No No No No No No No No No N/A N/A N/A N/A N/A Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No No No No No No No No No No No No Yes No No No No No No No No