NLS2009006, 10 CFR 50.55a Request Number RI-21, Revision 0, and Request Number RI-22, Revision 0

10 CFR 50.55a Request Number RI-21, Revision 0, and Request Number RI-22, Revision 0

ML090540420
Person / Time
Site:	Cooper
Issue date:	02/16/2009
From:	O'Grady B Nebraska Public Power District (NPPD)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NLS2009006
Download: ML090540420 (9)

Text

N Nebraska Public Power District "Always there when you need us" 10 CFR 50.55a NLS2009006 February 16, 2009 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001

Subject:

10 CFR 50.55a Request Number RI-2 1, Revision 0, and Request Number RI-22, Revision 0 Cooper Nuclear Station, Docket No. 50-298, DPR-46

Dear Sir or Madam:

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

10 CFR 50.55a Request Number RI-21, Revision 0, and Request Number RI-22, Revision 0, are applicable to the fourth ten-year ISI interval, which began March 1, 2006. NPPD requests NRC approval of the attached requests by February 28, 2010, which represents a standard twelve-month review period following submittal. Approval of these requests is not needed to support future work at CNS.

RI-21 is contained in Attachment 1 to this letter. NPPD has determined that compliance with the code requirements of achieving essentially 100% coverage of the welds listed in this attachment is impractical for CNS. Therefore, relief is required due to not achieving essentially 100% coverage. CNS performed the examinations using the alternative examination volume defined in Code Case N-613-1, Figure 1, as approved in Regulatory Guide 1.147, Revision 15. The proposed alternative and basis for use is provided in to this letter.

RI-22 is contained in Attachment 2 to this letter. Similar to RI-21, NPPD has determined that compliance with the code requirements of achieving essentially 100% coverage of welds listed in this attachment is impractical for CNS. The proposed alternative and basis for use is provided in Attachment 2 to this letter.

The examinations associated with both requests were performed in accordance with Appendix VIII of American Society of Mechanical EngineersSection XI using qualified personnel, procedures and equipment with the applicable limitations Set forth in 10 CFR 50.55a.

COOPER NUCLEAR STATION 4 )q0 7 P.O, Box 98 / Brownville, NE 68321-0098 Telephone: (402) 825-3817 / Fax: (402) 825-5211 www'nppd.com

NLS2009006 Page 2 of 2 Should you have any questions concerning this matter, please contact David Van Der Kamp, Licensing Manager, at (402) 825-2904.

Brian J. O'Grady Site Vice President

/dm Attachments cc: Regional Administrator w/attachments USNRC - Region IV Cooper Project Manager w/attachments USNRC - NRR Project Directorate IV-1 Senior Resident Inspector w/attachments USNRC - CNS NPG Distribution w/attachments CNS Records w/attachments

NLS2009006 Page 1 of 3 10 CFR 50.55a Request.Number RI-21, Revision 0 Relief Request in Accordance with 10 CFR 50.55a(g)(5)(iii)

--Inservice Inspection Impracticality--

ASME Code Components Affected Code Class: 1

References:

IWB-2500, Table IWB-2500-1 Examination Category: B-D - Full Penetration Welded Nozzles in Vessels Item Number: B3.90

==

Description:==

Reactor Pressure Vessel Nozzle-to-Vessel Welds Component Numbers: NVE-BD-N1A, NVE-BD-N2E, NVE-BD-N2H, NVE-BD-N2K, NVE-BD-N3A, NVE-BD-N5A

Applicable Code Edition and Addenda

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

Applicable Code Requirement

Table IWB-2500-1, Examination Category B-D, Item B3.90, requires 100% volumetric examination of the reactor vessel nozzle-to-vessel welds as defined by Figure IWB-2500-7(a). However, Cooper Nuclear Station (CNS) performed the examinations using the alternative examination volume defined in Code Case N-613-1, Figure 1, as approved in Regulatory Guide 1.147, Revision 15.

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 in Table RI-21-1 is impractical for CNS. The CNS construction permit was issued before the effective date of implementation for ASME Section XI, thus the plant was not designed to meet the requirements of inservice inspection. The configuration of the nozzles, the design of the vessel insulation support rings and the nozzle access hatches, and interferences from thermocouple pads, instrument lines, etc., prevent 100 % examination of the required weld volumes.

Burden Caused by Compliance A major modification to the reactor vessel nozzles and access hatches would be required in order to improve overall examination coverage. Therefore, obtaining essentially 100%

coverage is not feasible or practical.

NLS2009006 Page 2 of 3 10 CFR 50.55a Request Number RI-21, Revision 0 Proposed Alternative and Basis for Use In lieu of performing the code-required examinations, CNS proposes to examine the accessible portions of reactor vessel nozzle-to-vessel welds to the extent practical.

The examinations were performed in accordance with Appendix VIII of ASME Section XI using qualified personnel, procedures and equipment with the applicable limitations set forth in 10 CFR 50.55a. The extent of the nozzle restrictions and the total volume accessible for examination, based on the examinations performed in the fourth interval are compared to examinations performed in the previous third interval. In all cases, the coverage achieved in the fourth interval exceeded the coverage achieved in the previous interval.

Duration of Proposed Alternative Relief is requested for the fourth ten-year interval of the Inservice Inspection Program for CNS.

Precedents

1. Relief Request RI-21, Revision 2, was approved by the Nuclear Regulatory Commission on February 24, 2006, (TAC No. MC8512) for the third ten-year interval of the Inservice Inspection Program.

Relief Request Table RI-21-1 Nozzle Nozzle Access Restrictions  % Examined  % Examined Number Description 3 rd Interval 4 th Interval N1A Recirculation Nozzle configuration, and 32% 46%

Inlet insulation support frame N2E, H Recirculation Nozzle configuration, and 40% 55%

&K Outlet insulation support frame N3A Main Steam Nozzle configuration 35 % 49%

N5A Core Spray Nozzle configuration, 31% 51%

insulation support frame, and thermocouple pads

NLS2009006 Page 3 of 3 10 CFR 50.55a Request Number RI-21, Revision 0 The figure below shows the examination volume limitations to the applicable examination zones as required per ASME Section XI, Figure IWB-2500-7(a):

Shell!

FIGURE RI-21-1 (Typical) 8?RL Ext Pau 1L06, S Nozzle

NLS2009006 Page 1 of 3 10 CFR 50.55a Request Number RI-22, Revision 0 Relief Request in Accordance with 10 CFR 50.55a(g)(5)(iii)

--Inservice Inspection Impracticality--

ASME Code Components Affected Code Class: 1

References:

IWB-2500, Table IWB-2500-1 Examination Category: B-F - Pressure Retaining Dissimilar Metal Welds in Vessel Nozzles (R-A)

Item Number: B5.10

==

Description:==

Nozzle-to-Safe End Butt Welds Component Numbers: CSA-BF-lx, RRH-BF-1, RRK-BF-1, RRE-BF-1

Applicable Code Edition and Addenda

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

Applicable Code Requirement

Table IWB-2500-1, Examination Category B-F, Item B5. 10, requires 100 % volumetric examination of the pressure retaining dissimilar metal welds in vessel nozzles as defined by Figure IWB-2500-8.

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 welds listed in Table RI-22-1 is impractical for Cooper Nuclear Station (CNS).

CNS replaced the Class 1 stainless steel piping in the mid- 1980's. The best techniques available to mitigate intergranular stress corrosion cracking (IGSCC) were used:

IGSCC resistant material, corrosion resistant cladding on the internal diameter of the nozzle buttering, and Induction Heat Stress Improvement (IHSI). These activities provided welds that are Generic Letter 88-01 IGSCC Category "A." The resultant welds were examined using the standard industry techniques for IGSCC at that time.

Typical volumetric examination coverage was previously reported to be greater than 90 %. The radial shrinkage caused by the IHSI in the heat affected zone areas during the construction of the welds prevents full contact of the ultrasonic testing (UT) probes.

NLS2009006 Page 2 of 3 10 CFR 50.55a Request Number RI-22, Revision 0 Burden Caused by Compliance Removal of the nozzle base metal by grinding or machining would be required to obtain a surface conducive for examination. Therefore, obtaining essentially 100% coverage is not feasible or practical.

Proposed Alternative and Basis for Use In lieu of performing the code-required examinations, CNS proposes to examine the accessible portions of reactor vessel nozzle-to-safe-end welds to the extent practical.

The examinations were performed in accordance with Appendix VIII of ASME Section XI using qualified personnel, procedures and equipment with the applicable limitations set forth in 10 CFR 50.55a. The current Performance Demonstration Initiative (PDI) techniques that implement Appendix VIII of ASME Section XI are more restrictive on the requirements for weld profiles. The current examinations are considered more reliable than previously performed volumetric examinations.

The weld profile shown in Figure RI-22-1, indicates that the shrinkage in the heat affected zone on the nozzle side caused a greater than 1/32" gap between the UT search unit and examination surface. Both axial UT scans obtained 100% coverage necessary to detect circumferential flaws. However, the circumferential scans necessary to detect axial flaws could not be fully obtained. The circumferential scan on the safe-end was obtained but the circumferential scan on the nozzle side could not be obtained thus resulting in the combined volumetric coverage estimates provided in Table RI-22-1.

The examination coverage achieved for the required examination volume of ASME Section XI Figure IWB-2500-8 and the CNS Risk-Informed Program was obtained as follows:

0 50% Code volume based on achieving 100% coverage of the two required axial scans for the detection of circumferentially oriented flaws

• 25 % Code volume based on achieving 100 % coverage of one the two required circumferential scans for the detection of axially oriented flaws The coverage calculation is based on obtaining full coverage on three of the four scans:

• Axial scan coverage (50%) + Circumferential scan coverage (50% /2=25 %)

75%

NLS2009006 Page 3 of 3 10 CFR 50.55a Request Number RI-22, Revision 0 Duration of Proposed Alternative Relief is requested for the fourth ten-year interval of the Inservice Inspection Program for CNS.

Relief Request Table RI-22-1 Weld System Access Restrictions  %

Number Examined CS-BF-lx Core Spray Weld Contour 75 RRE-BF-1 Recirculation Weld Contour 75 Outlet RRH-BF-1 Recirculation Weld Contour 75 Outlet RRK-BF-1 Recirculation Weld Contour 75 Outlet The figure below shows the examination volume limitations to the applicable examination zones as required per ASME Section XI, Figure IWB-2500-8:

FIGURE RI-22-1 (Typical)

Radial Shrink Area Limitation Safe End 316 L Stainless Stainless Steel Clad

4 ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS© 4

ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS© Correspondence Number: NLS2009006 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 N/A N/A 1- 4

4. 4 4- 4

• 1 4

• 1 4 I t I PROCEDURE 0.42 REVISION 23 PAGE 18 OF 25 1