NLS2005003, Response to Request for Additional Information Regarding Relief Request RI-35 Cooper Nuclear Station

Response to Request for Additional Information Regarding Relief Request RI-35 Cooper Nuclear Station

ML050110236
Person / Time
Site:	Cooper
Issue date:	01/05/2005
From:	Edington R Nebraska Public Power District (NPPD)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NLS2005003, TAC MC4954
Download: ML050110236 (8)

Text

N Nebraska Public Power District NLS2005 003 Always there when you need us5 January 5, 2005 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001

Reference:

Response to Request for Additional Information Regarding Relief Request RI-35 Cooper Nuclear Station, NRC Docket No. 50-298, DPR-46

1. Letter to R. Edington (Nebraska Public Power District) from U.S. Nuclear Regulatory Commission dated December 3, 2004, "Request for Additional Information On Relief Request RI-35, Repair of Reactor Pressure Vessel Control Rod Drive Nozzle-To-Cap Weld (TAC No. MC4954)."

2. Letter to U. S. Nuclear Regulatory Commission from R. Edington (Nebraska Public Power District) dated October 25, 2004, "Inservice Inspection Relief Request RI-35" (NLS2004125).

The purpose of this letter is for the Nebraska Public Power District (NPPD) to respond to the Request for Additional Information provided in Reference 1 by the Nuclear Regulatory Commission (NRC) regarding the previously submitted Relief Request of Reference 2.

Question I

Response

Question 2:

Response

The October 25, 2004, submittal states that the welder and ivelding procedures will be qualified to use the shielded metal arc iwelding process. However, the deposition of the Alloy 52 requires the uise of the gas tungsten arc welding (GTA ad) process. Is the licensee planning to use welder and welding procedures qualified to uise the GTA Reprocess? If so, explain the difference.

Shielded Metal Arc Welding will be used for a seal weld or any local repairs, if required, before applying the weld overlay. The overlay itself will be deposited using GTAW. Welding procedures and personnel qualifications will be in accordance with the applicable ASME Section XI and Section IX requirements and any additional requirements of the cited code cases.

Provide a diagram/sketch showing the control rod drive return nozzle-to-cap wveld and the proposed weld overlay configuration. provides a conceptual drawing of the proposed repair. The following additional information is provided per the Staff's request:

1. Cap material & dimension - SB-166, NI-CR-FE, 5.25 inches minimum Outer Diameter, 3.948 +/- 0.010 inches Inner Diameter.

COOPER NUCLEAR STATION P.O. Box 98/ Brownville. NE 6832140098 Telephone: (402) 825-3811 / Fax: (402) 825.5211 www.nppd.com

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NLS2005003 Page 2 of 4

2. The nozzle material, wall thickness and outside diameter - SA508 Class 2, 1.353 inches Wall Thickness (excludes 0.22 inches stainless steel clad), 5.25 inches Outer Diameter.

3. The operating pressure - nominal 1005 psig, 1275 psig design

4. The operating temperature - nominal 5470F, 5750F design Question 3:

Section (g)(2) of Code Case N-504-2 specifies that the evaluation of the repaired weld consider residual stresses produced by the weld overlay with the other applied loads on the system. The effects of water backing on the repair weld shall be considered. Section (g)(3) of Code Case N-504-2 specifies that the welds and components meet the applicable stress limits of the constnrctionz code.

a. Wiat is the constnrction code that was utsed to satisfy the evaluation requirements in Sections (g)(2) and (g)(3) of the Code Case?

b. Provide a description of the methodology used to determine residual stresses and shrinkage effects.

c. Provide a list and a description of the calculations utsedfor determining the length and thickness of the weld overlay.

d. Provide a table comparing the current licensing basis primnary and primary-pluts-secondary stresses, and the primnary and prinmary-plus-secondary stresses at the location of the highest stress regions resultingfrom the installation of the weld overlay. Show that the conponent and the weld meet the applicable stress limnits of the Cooper constnrction code, as required by the Code Case.

e. Provide the largest ASME Section Illfatigue cumitulative usage factor and its location in the region with and without the weld overlay, considering all applicable thermal and mechanical transients.

Response

3a. The Reactor Pressure Vessel was designed and constructed to ASME Section III, 1965 Edition, 1966 Addenda. The piping was designed to ANSI/ASME B31.1-1967 and installed to B31.7-1969. The Control Rod Drive (CRD) Cap was designed and installed to ASME Section M, 1974 through Winter 1975 Addenda.

3b. The end cap at Cooper is a free end, with no attached piping. Consequently, shrinkage of the weld overlay material upon cooling will have no effect on any other component, and so it is not necessary to perform a shrinkage analysis following repair application. Residual stresses at the weld overlay location have no effect on other components in the system, and, being steady state, secondary stresses do not affect Code acceptability of the repaired location.

NLS2005003 Page 3 of 4 Residual stresses would potentially affect Inter-Granular Stress Cracking Corrosion growth in a susceptible material, but the Alloy 52 weld material is not considered to be susceptible, and no credit is taken for the underlying base materials. Residual stresses, being steady state stresses, would only act as mean stresses for consideration of fatigue crack growth. Therefore, it was not necessary to separately evaluate weld residual stresses for this repair.

3c. The weld overlay reinforcement thickness was calculated using Structural Integrity (SI) proprietary software, pc-CRACK, SI calculation COOP-17Q-301: "Weld Overlay Design for CRD Return Line Nozzle Cap Weld". The methodology is consistent with ASME Section XI, IWB-3640 and Code Case N-504.

3d. The Cooper CRD end cap stress report (GE 22A5561, Rev. 0, 9/30/77) lists the maximum primary stress intensity as 5.8 ksi, compared to an allowable Sm of 23.3 ksi. This is entirely due to pressure. No other mechanical loads apply to the end cap, since it is not connected to any other mechanical components.

The axial stress due to pressure is reported as 2.3 ksi. Design of the weld overlay using the methods of ASME Section XI, IWB-3640 and Appendix C consider all primary stresses in meeting the design criteria.

3e. The cumulative usage factor for the original design for the nozzle is 0.022.

Since the capping of the nozzle eliminated the weight of the CRD return piping and most thermal stresses, this was considered a bounding limit for the cap. Application of the weld overlay repair will not adversely affect this value.

Should you have any questions concerning this matter, please contact Mr. Paul Fleming at (402) 825-2774.

Sincerely, Randall K. dington Vice President - Nuclear and

/

Chief Nuclear Officer Awrv Enclosure

NLS2005003 Page 4 of 4 cc: Regional Administrator w/enclosure USNRC -Region IV Senior Project Manager Nv/enclosure USNRC - NRR Project Directorate IV-1 Senior Resident Inspector w/enclosure USNRC NPG Distribution w/o enclosure Records xv/enclosure

NLS2005003 Page 1 of3 ENCLOSURE 1 Drawing of Weld Overlay Design From Structural Integrity Report SIR-04-106

A-508 Class 2 1

450MIN TYP A

- I1, B

I III Recommended Additional LengthI Alloy 600

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X14...

{

J I

/

INil A

CRD/

Cap

/

Alloy 52 Overlay I

II I

II

\\

Cl Alloy 182/82 Butter RD Nozzle qWELD 03.28 WELD NUMBER FLAW DesignDimensions COMMENTS l CHARACTERIZATION t

A B

CRD Hydraulic Assumed 3600 Circ.

0.25" 1.0" 1.0" Recommend Return Cap Weld 100% throughwall flaw see MIN MIN Blend Into Note Nozzle 4

0 HLG /9/7/04 AJG / 9/7/04 HLG /9/7/04 Revision Prepared by/Date Checked By/Date Approved by/Date COMMENTS Job No: COOP-17Q Plant/Unit:

STRUCTURAL File No: COOP-17Q-301 Cooper Nuclear INTEGRITY Power Station ASSOCIATES, INC.

Drawing No: COOP-17Q-01

Title:

Standard Vld Overlav Design lShect I of 2

NOTES

1. Component surface is to be examined by dye penetrant method and accepted as clean prior to overlay application.

2. In the event that the original component surface does not pass the note I requirements, the final deposited temper bead weld layer is to be examined by dye penetrant method and accepted as clean before proceeding with subsequent layers.

3. Weld overlay wire shall be ERNiCrFe-7 (Alloy 52).

4. The design thickness (0.25 inch) is the minimum thickness beyond the first PT clean surface. (Typo corrected by 1/5/05)

5. Apply as many layers as required to achieve the design overlay thickness 't".

6. Design thickness includes no allowance for surface conditioning operations to facilitate UT inspection.

7. Design length is that required for structural reinforcement; greater length may be required for effective UT inspection. This is to be determined in the field.

~...~:I:.-I I

'-1 I.

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Job No: COOP-17Q Plant/Unit:

STRUCTURAL File No: COOP-17Q-301 Cooper Nuclear INTEGRITY Power Station ASSOCIATES, INC.

Drawing No: COOP-17Q-01

Title:

Standard Weld Overlay Design Sheet 2 of 2 File No.:

COOP-17Q-301 I

Page A3 of A3

I ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS(

Correspondence Number: NLS2005003 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 & Regulatory Affairs Manager at Cooper Nuclear Station of any questions regarding this document or any associated regulatory commitments.

COMMITTED DATE COMMITMENT OR OUTAGE None 4

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