NLS2012001, 10 CFR 50.55a Request Number RI-07, Revision 0

10 CFR 50.55a Request Number RI-07, Revision 0

ML12023A005
Person / Time
Site:	Cooper
Issue date:	01/16/2012
From:	O'Grady B Nebraska Public Power District (NPPD)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NLS2012001
Download: ML12023A005 (7)

Text

N Nebraska Public Power District Always there when you need us 10 CFR 50.55a NLS2012001 January 16, 2012 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001

Subject:

10 CFR 50.55a Request Number RI-07, Revision 0 Cooper Nuclear Station, Docket No. 50-298, DPR-46

Dear Sir or Madam:

The purpose of this letter is to request the Nuclear Regulatory Commission (NRC) grant Nebraska Public Power District (NPPD) relief from certain inservice inspection (ISI) code requirements for Cooper Nuclear Station (CNS) pursuant to 10 CFR 50.55a.

The attached 10 CFR 50.55a request is applicable to the fourth ten-year ISI interval, which began March 1, 2006. Approval of this request is not needed to support currently scheduled work at CNS. As such, NPPD requests NRC approval of the request by January 17, 2013, which allows a twelve-month review period.

If you have any questions, please contact David Van Der Kamp, Licensing Manager, at (402) 825-2904.

Sincerely, Brian J. O'Grady Vice President - Nuclear and Chief Nuclear Officer

/bk Attachment COOPER NUCLEAR STATION l P.0. Box 98 / Bro wn ville, NE 68321-0098 ~

Telephone: (402) 825-3811 / Fax: (402) 825-5211 wwvv nppd corn

NLS2012001 Page 2 of 2 cc: Regional Administrator w/ attachment USNRC - Region IV Cooper Project Manager w/ attachment USNRC - NRR Project Directorate IV-1 Senior Resident Inspector w/ attachment USNRC - CNS NPG Distribution w/ attachment CNS Records w/ attachment

"I NLS2012001 Attachment Page 1 of 4 10 CFR 50.55a Request Number RI-07, Revision 0 Inspection of RHR Shell Circumferential and Nozzle to Head Welds Relief Request in Accordance with 10 CFR 50.55a(g)(5)(iii)

ASME Code Components Affected Code Class: 2

References:

IWC-2500, Table IWC-2500-1 Examination Category: C-A - Pressure Retaining Welds in Pressure Vessels C-B - Pressure Retaining Nozzle Welds in Vessels Item Number: C1.10, C2.21

==

Description:==

Shell Circumferential Weld, Nozzle to Head Weld Component Numbers: RHR-CA-2A (Shell to Distributor Ring End Top)

RHR-CB-1A (Nozzle to Head Top)

Applicable Code Edition and Addenda

American Society of Mechanical Engineers (ASME) Code Section XI, 2001 Edition, 2003 Addenda.

Applicable Code Requirement

Table IWC-2500- 1, Examination Category C-A, Item C 1.10 requires 100% volumetric examination of pressure vessel welds as defined by Figure IWC-2500-1.

Table IWC-2500-1, Examination Category C-B, Item C2.21 requires 100% surface and volumetric examination of pressure retaining nozzle vessel head welds as defined by Figure IWC-2500-4(d).

Impracticality of Compliance Pursuant to 10 CFR 50.55a(g)(5)(iii), Nebraska Public Power District has determined that compliance with the code requirements of achieving essentially 100% coverage of the welds listed above is impractical for Cooper Nuclear Station (CNS). The CNS construction permit was issued before the effective date of implementation for ASME Section XI, thus the plant was not designed to fully meet the requirements of inservice inspection. The configuration of the 1A Residual Heat Removal (RHR) heat exchanger shell circumferential weld RHR-CA-2A (shell to distributer ring end top) and nozzle to shell weld RHR-CB-1A (nozzle to head top) prevents 100% examination of the required weld volumes. See attached Figures RI-07-1 and RI-07-2 for configuration details.

Burden Caused by Compliance A major modification to the RHR heat exchanger or replacement would be required in order to improve overall examination coverage. Therefore, obtaining essentially 100% coverage is not feasible or practical.

NLS2012001 Attachment Page 2 of 4 Proposed Alternative and Basis for Use In lieu of performing the code-required examinations, CNS proposes to examine the accessible portions of the RHR heat exchanger welds to the extent practical.

The examinations were performed prior to CNS' last refueling outage in March 2011, and in accordance with ASME Section XI using qualified personnel, procedures, and equipment. The magnetic particle examination performed on RHR-CB-1A achieved greater than 90% coverage, however, based on the configurations of these welds, the volumetric examination coverages achieved were 65.1% for RHR-CB-1A (See Figure RI-07-1) and 48.1% for RHR-CA-2A (See Figure RI-07-2). Volumetric examination coverages reported in the previous interval were both over 90% however, the reductions in coverages achieved this interval are attributed to more conservative examination techniques thus providing more reliable results. Using the provisions of this relief request as an alternative to the specific requirements of ASME Table IWC-2500- 1, identified above, will continue to provide reasonable assurance of structural integrity since the percent of examination coverage already obtained would have identified any pattern of service induced degradation that may have developed.

Duration of Proposed Alternative Relief is requested for the fourth ten-year interval of the CNS Inservice Inspection Program ending on February 29, 2016.

Precedents None.

NLS2012001 Attachment Page 3 of 4 Figure RI-07-1 Circ Scan Ax Scan A)dal Scan Coverage = 100%

Circ Scan Coverage = 30.28%

Ax and Circ Coverage Total Scan Coverage = 65.14%

60' and 70 angles worn also used to increae exam co*e*e Not to Scale

NLS2012001 Attachment Page 4 of 4 Figure RI-07-2 RHR-CA-2A Axial Scan Coverage Lwidearn Sife Aidl Coverage 69%

K/-X////,7One Directhon Scan Coverage

',Z/1/Z/-Two Direction Scan Coverage Axial Scan Coverage = 67,50%

r!5 7~ane Mn L-rla!te to 'Me* v%Mcw (ex ------ Net to Scale.

Vessel Circurrff ~rential Udream Sie COnCoverage 20%

mi

,,-. ~.

Distibulor Ring Downeaum Side Cki Coverage 37.5%

Z'//6///One Drection Scan Coverage

////// Two Di-eclon Scan Coverage Circ Scan Coverage = 28.70%

Not to Scale Total Axial and Circ Scan Coverage = 48.10%

ATTACHMENT 3 LIST OF REGULATORY COMMITMENTSC 4 ATTACHMENT3 LIST OF REGULATORY COMMITMENTSN4 Correspondence Number: NLS2012001 The following table identifies those actions committed to by Nebraska Public Power District (NPPD) in this document. Any other actions discussed in the submittal represent intended or planned actions by NPPD. They are described for information only 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.

COMMITMENT COMMITTED DATE COMMITMENT NUMBER OR OUTAGE None PROCEDURE 0.42 REVISION 27 PAGE 18 OF 25