ML20095G198
| ML20095G198 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 12/16/1995 |
| From: | Mueller J NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20095G199 | List: |
| References | |
| NLS950240, TAC-M82258, NUDOCS 9512200071 | |
| Download: ML20095G198 (4) | |
Text
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- =fM" NLS950240 December 16,1995 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Report of Feedwater Nozzle Examination Results and Relief Request Cooper Nuclear Station, NRC Docket No. 50-298, License No. DPR-46
References:
1.
Letter to G. R. Hom (NPPD) from R. B. Bevan (US NRC), dated February 13,1992, " Cooper Nuclear Station - Staff Acceptance of Fracture Mechanics Evaluation of Flaw Indications (TAC No. M82258) 2.
Letter (No. NLS950157) to USNRC Document Control Desk from J. IL Mueller (NPPD), dated October 18,1995, " Third Ten-Year Interval Inservice Inspection Program" Gentlemen:
In accordance with Reference 1, the Nebraska Public Power District (District) has reexamined feedwater nozzle flaw indications in Code Category B-D welds N4A, N4C, and N4D found during the Fall 1991 refueling outage at Cooper Nuclear Station (CNS). This reexamination was completed during the 1995 refueling outage using improved examination and sizing techniques.
These techniques are detailed in the attached report.
Many of the indications correlate to fabrication welding defects, which were determined to be acceptable under the Construction Code. Based c,n this, and the nature of the ultrasonic reflectors from the underlying flaws, the District has determined that the flaws are most likely fabrication artifacts which have been present in the welds since construction. The underlying flaws have remained essentially unchanged from the 1991 outage to the 1995 outage, are inactive and benign, and are acceptable per Subarticle IWB-3600 of the ASME Section XI Code (Code).
The fracture mechanics analysis supports the continued validity of the evaluation documented in Reference 1 and, therefore, the indications are acceptable for the remaining life of the plant.
Because the recent inspection results have confirmed the 1991 conclusion that these indications are acceptable for the remaining life of the plant, the District believes that successive examinations required by Paragraph IWB-2420(b) of the ASME Code are not warranted and plans to return to a normal Code inspection frequency for welds N4A, N4C, and N4D.
Accordingly, the District requests NRC approval of relief from this ASME Code requirement which is detailed in Attachment 3. Approval is requested prior to the next inspection interval due date for the subject weld indications, which is prior to Refueling Outage 18 expected to commence F911 1998, dCC030 9512200071 951216 e
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NLS950240 December 16,1995 Page 2 0f 2 The results of these reexaminations are addressed in more detail in the attached reports.
Attachment I provides the fracture mechanics evaluation of UT indications found during the 1995 reexamination of the Feedwater Nozzle-to-Vessel welds at CNS. Attachment 2 provides the comparative analysis of UT indications for the Feedwater Nozzle-to-Vessel welds N4A, N4C, and N4D. Attachment 3 to this letter contains Relief Request RI-19, which is an addition to the relief requests previously submitted per Reference 2 (Third Ten-Year Interval Inservice Inspection program submittal). The list of relief requests contained in Section 7 of the Third Ten-Year Interval Inservice Inspection program has been updated to reflect the submittal of Relief Request RI-19, and is also included in Attachment 3. Please update your program document with this information.
If you have any questions or require any additional information regarding the attached reports, or the relief request, please contact me.
Sincerely,
/
dA ohn H. Mueller Site Manager
/dnm Attachments cc:
Senior Project Manager USNRC - NRR Project Directorate IV-1 Senior Resident Inspector USNRC - Cooper Nuclear Station Regional Administrator USNRC - Region IV NPG Distribution l
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LIST OF NRC COMMITMENTS l ATTACHMENT 3 1
. Correspondence No: NLS950240 The following table identifies those act. ions committed to by the District in this document. Any other actions discussed in the submittal represent intended or planned actions by the District. They are described to the NRC for the'NRC's information and are not regulatory commitments.
Please notify the Licensing Manager at Cooper Nuclear Station of any questions regarding this document or any associated regulatory commitments.
COMMITTED DATE COMMITMENT OR OUTAGE N/A-1 None 1
4 4
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PROCEDURE 1, LUMBER 0.42 l
REVISION NUMBER 0.2 l
PAGE 10 OF 16 l
Attechment 1 to NLS950240 General Electric Fracture Mechanics Evaluation of UT Indications found during 1995 reexamination of the Feedwater Nozzle to Shell Welds at CNS - 9 Pages Total J