ML17332A448
| ML17332A448 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 11/23/1994 |
| From: | Fitzpatrick E INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | Russell W NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| AEP:NRC:1059E, NUDOCS 9412020244 | |
| Download: ML17332A448 (3) | |
Text
PRIC)RI EY (ACCELERATED RIDS PROCI'.SSIi REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION NBR:9412020244 DOC.DATE: 94/11/23 NOTARIZED: NO DOCKET I FACIL:50-315 Donald C.
Cook Nuclear Power Plant, Unit 1, Indiana M
05000315 50-316 Donald C.
Cook Nuclear Power Plant, Unit 2, Indiana M
05000316 AUTH.NAME AUTHOR AFFILIATION P
FITZPATRICK,E.
(formerly Indiana
& Michigan Ele RECIP.NAME RECIPIENT AFFILIATION RUSSELL,W.T.
Document Control Branch (Document Control Desk)
R
SUBJECT:
Updates NRC on mitigation of flow-induced vibrational wear of bottom mounted instrumentation thimble tubes in facilities, including bottom mounted instrumentation thimble tube 1994 insp results.
DISTRIBUTION CODE:
AOOID COPIES RECEIVED:LTR I ENCL g SIZE:
TITLE: OR Submittal:
General Distribution NOTES:
RECIPIENT ID CODE/NAME PD3-1 LA HICKMAN,J INTERN~FICE CENTE~R 03.
NRR/DRCH/HICB NRR/DSSA/SPLB NUDOCS-ABSTRACT EXTERNAL: NOAC COPIES LTTR ENCL RECIPIENT ID CODE/NAME PD3-1 PD NRR/DE/EELB NRR/DRPW NRR/DSSA/SRXB OGC/HDS2 NRC PDR COPIES LTTR ENCL D
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N NOTE TO ALL"RIDS" RECIPIENTS:
PLEASE HELP US TO REDUCE KV'1STE! CONTACTTHE DOCL'WIENTCONTROL DESK, ROOM PI -37
< EXT 504-0083 ) TO I;LIXII.4 KTE YOI'R. iAIILFROTI DISTRIBUTIONLIS'I'S I:OR DOCL'h,!EN'I'S YOI.'ON"I'L'ED!
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Indiana Michigan Power Company ~
P.O. Box 16631 Coiumbus, OH 43216 AEP:NRC:1059E Donald C. Cook Nuclear Plant Units 1 and 2
Docket Nos.
50-315 and 50-316 License Nos.
DPR-58 and DPR-74 BOTTOM MOUNTED INSTRUMENTATION THIMBLE TUBE 1994 WEAR INSPECTION RESULTS U. S. Nuclear Regulatory Commission Document Control Desk Washington, D.
C.
20555 Attn:
W. T. Russell November 23, 1994
Dear Mr. Russell:
In our letter AEP:NRC:1059D, dated September 4,
1992, the NRC staff was informed of the status and plans with regard to the mitigation of flow-induced vibrational wear of the bottom mounted instrumentation thimble tubes in both units at Donald C. Cook Nuclear Plant.
The purpose of this letter is to update the NRC staff on this subject.
During the 1992 refueling outages, 15 thimble tubes were replaced in Unit 1 and 22 thimble tubes were replaced in Unit 2.
The replacement thimble tubes were chrome plated at axial locations corresponding to the lower core plate and fuel assembly lower nozzle area.
During the 1994 refueling outages, an eddy current inspection was performed on all thimble tubes.
After one cycle of operation, the chrome plated thimble tubes showed no indications of wear on the plated portions of the tubes.
Active indications of wear continued to be observed on the other thimble tubes.
Based on these results, we believe that the chrome plating is an effective engineered solution to vibration-induced thimble tube wear.
We now intend to implement a
design change to replace all present-design thimble tubes with chrome plated tubes.
Although less severe, wear indications have also been observed at axial tube locations corresponding to the lower core support dome and diffuser plate in the lower internals.
The new tubes will be chrome plated over a
longer length to impede wear from occurring at these additional locations.
It is anticipated that this design change will be implemented on both units during the refueling outages scheduled to occur in 1997.
9+1202024y 9g1123 7j 0 $ 8 PDR ADOCK 050003i5 P
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Mr. W. T. Russell AEP'NRC:1059E In the interim, we will continue to monitor thimble tube wear.
Eddy current inspections will be performed on every thimble tube during each refueling outage to continue to evaluate the effectiveness of the chrome plating and to continue to monitor the wear rates of the non-chrome plated tubes.
Until the present-design thimble tubes are
- replaced, wear indications on worn thimble tubes will be evaluated each refueling outage to determine if interim corrective actions (e.g., shortening of the tube to reposition the wear scar or capping of the tube to contain a potential through-wall leak) are necessary to minimize the probability or consequences of a through-wall leak.
We will continue to keep the NRC staff informed of developments in this area.
Sincerely, E.
E. Fitzpatrick Vice President eh CC:
A. A. Blind G. Charnoff J.
B. Martin - Region III NFEM Section Chief NRC Resident Inspector
- Bridgman J.
R. Padgett