ML20134A902
| ML20134A902 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 01/24/1997 |
| From: | Hall J NRC (Affiliation Not Assigned) |
| To: | Horn G NEBRASKA PUBLIC POWER DISTRICT |
| References | |
| TAC-M96954, NUDOCS 9701290163 | |
| Download: ML20134A902 (4) | |
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' January 24, 1997 Mr. G. R. Horn Sr. Vice President of Energy Supply Nebraska Public Power District 1414 15th Street Columbus, NE 68601
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SUBJECT:
REQUEST FOR DEFERRAL OF SECOND CORE SHROUD INSPECTION FOR COOPER NUCLEAR STATION'(TAC NO. M96954)
Dear Mr. Horn:
By letter dated October 22, 1996, the Nebraska Public Power District '(NPPD) requested Nuclear Regulatory Commission (NRC) staff approval for deferral of the second series of planned inspections of the core shroud at the Cooper
- Nuclear Station (CNS). NPPD performed initial inspections of the core shrouc in accordance with NRC Generic Letter 94-03, "Intergranular Stress Corrosion Cracking of Core Shrouds in Boiling Water Reactors (BWR)," during Refueling Outage (RFO) 16 in late 1995. Based on our review of the results of those i
inspections, in our letter of June 27, 1996, the NRC staff concluded that tie i
plant could be safely operated for the duration of the current 18-month operating cycle without the need to implement repairs to the shroud.
In your October 22, 1996, request, you stated that the BWR Vessel and Internals Project (BWRVIP) had developed revised inspection guidance for core i
shrouds, and that application of that guidance would indicate that the CNS l
core shroud need not be reinspected for 8 years. However, recognizing that the NRC staff has not yet completed its review of that guidance, your specific
. request was to defer the next core shroud inspections until RF0 18, currently scheduled for the Fall of 1998.
The core shroud inspection during the 1995 refueling outage found cracking in four welds. The H3 weld was cracked the worst with 79.9% of the H3 weld inspected and the total length of the indications 66 inches (14.9% of the inspectedlength). The remaining three welds were cracked considerably less (4.4% of the inspected length or less).
Your evaluation showed that all of the welds met the applicable limit load and/or linear elastic fracture mechanics (LEFN) screening criteria and no further evaluation or non-destructive examination characterization was deemed necessary.
In your limit load analysis, you determined the allowable through-wall circumferential flaw length for each of the eight core shroud welds. These lengths ranged from 323 inches to 423 inches. For the H3 weld, the weld with the longest indications, the tilowable crack length was 393 inches.
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Mr. G. R. Horn On the basis of the large margin available between the actual and allowab,le crack lengths and allowing for crack growth at a bounding rate of 5 X 10' inch / hour, the staff finds that the structural integrity of the shroud is capable of being maintained for at least another fuel cycle. Therefore, the staff finds your request for deferral of the core shroud inspection for another fuel cycle acceptable.
Sincerely, t 1,tfjL s R. Hall, Senior Project Manager oject Directorate IV-1 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket No. 50-298 cc:
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1 Mr. G. R. Horn,
On the basis of the large margin available between the actual and allowab,le crack lengths and allowing for crack growth at a bounding rate of 5 X 10'
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. inch / hour, the staff finds that the structural integrity of the shroud is capable of being maintained for at least another fuel cycle. Therefore, the staff finds your request for deferral of the core shroud inspection for another fuel cycle acceptable.
Sincerely, ORIGINAL SIGNED BY:-
James R. Hall, Senior Project Manager i
Project Directorate IV-1 i
Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation 4
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Docket No. 50-298 cc: See next page
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DISTRIBUTION:
Docket File PUBLIC PD4-1 r/f J. Roe C. Hawes ACRS J. Hall OGC (15B18)
J. Dyer, RIV _
3 E. Adensam (EGA1)
Document Name: C0096954.LTR 0FC~
PM/PD4-1 (A)LA/PD4-1 NAME JHall N CHawes W DATE l /24/9N l M~d 97
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COPY YES/NO YES/NO 0FFICIAL RECORD COPY.
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i Mr. G. R. Horn l
Nebraska Public Power Company Cooper Nuclear Station i
cc:
Mr. John R McPhail, General Counsel Lincoln Electric System Nebraska Public Power District
~ ATTN: Mr. Ron Stoddard i
P. O. Box 499 lith & 0 Streets I
Columbus, NE 68602-0499 Lincoln, NE 68508 Nebraska Public Power District Midwest Power ATTN: Mr. P. D. Graham ATTN: Richard J. Singer, Manager-Nuclear Vice President of Nuclear Energy 907 Walnut Street P. O. Box 98 P. O. Box 657 Brownville, NE 68321 Des Moines, IA 50303
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Randolph Wood, Director Nebraska Department of Environmental Nebraska Public Power District Control ATTN: Mr. B. L. Houston, Nuclear P. O. Box 98922 Licensing & Safety Manager Lincoln, NE 68509-8922 P. O. Box 98 Brownville, NE 68321 Mr. Larry Bohlken, Chairman Nemaha County Board of Commissioners Nemaha County Courthouse i
1824 N Street l
Auburn, NE 68305
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Senior Resident Inspector i
U.S. Nuclear Regulatory Commission P. O. Box 218 Brownville, NE 68321 4
l Re'gional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 5
Ms. Cheryl Rogers, LLRW Program Manager j
Division of Radiological Health Nebraska Department of Health 301 Centennial Mall, South P. O. Box 95007 I
Lincoln, NE 68509-5007 1
Mr. Ronald A. Kucera, Department Director of Intergovernmental Cooperation i
Department of Natural Resources
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P.O. Box 176 i
Jefferson City, MO 65102 i
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