LIC-10-0004, Response to Request for Additional Information Re Use of Alternate Depth Sizing Qualification

Response to Request for Additional Information Re Use of Alternate Depth Sizing Qualification

ML100480308
Person / Time
Site:	Fort Calhoun
Issue date:	02/16/2010
From:	Reinhart J Omaha Public Power District
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LIC-10-0004
Download: ML100480308 (8)

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ii;;;;ii Omaha Public Power District Fort Calhoun Station 9610 Power Lane Blair, NE 68008 February 16, 2010 LlC-10-0004 u.s. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555

References:

1. Docket No. 50-285

2. Letter from OPPD (R. P. Clemens) to NRC (Document Control Desk), "Request for Use of an Alternate Depth Sizing Qualification,"

dated October 30,2009 (LlC-09-0088) (ML093030358)

3. Email from NRC (Lynnea Wilkins) to OPPD (M. L. Edwards),

"Request for Additional Information Regarding Relief Request for Use of an Alternate Depth Sizing Qualification" dated January 15, 2010 (ML100150845)

SUBJECT:

Response to Request for Additional Information Regarding Use of an Alternate Depth Sizing Qualification In Reference 2, pursuant to 10 CFR 50.55a(g)(5)(iii), the Omaha Public Power District (OPPD) requested approval for use of an alternate depth sizing qualification on the Fort Calhoun Station (FCS), Unit No. 1 reactor pressure vessel (RPV) nozzle-to-safe end dissimilar metal (DM) welds from the inside surface. The request was submitted for the fourth 1O-year in-service inspection interval.

In Reference 3, the NRC requested that OPPD provide additional information in order to complete its review. In addition, the NRC requested that OPPD revise the Section titled, Proposed Alternative and Basis for Use to clarify that relief is requested due to impracticality pursuant to 10 CFR 50.55a(g)(6)(i) rather than as an alternative that provides acceptable levels of quality and safety.

Accordingly, Attachment 1 provides the requested information. Attachment 2 provides the revised relief request. As requested, the Section titled "Proposed Alternative and Basis for Use" was revised to clarify that relief pursuant to 10 CFR 50.55a(g)(6)(i) is requested due to impracticality. The relief request was also revised to note that the RPV nozzles were successfully inspected during the 2009 Refueling Outage (when initially submitted, the RPV nozzle inspection was yet to be performed). No flaws were found.

Employment with Equal Opportunity 4171

U. S. Nuclear Regulatory Commission LIC-10-0004 Page 2 Please note that Section numbering was removed from the relief request to correct a numbering discrepancy. Revision bars in the right margin denote the location of revised information.

If you have any questions regarding this submittal, please contact Mr. Bill Hansher at (402) 533-6894.

rey A. Reinhart Site Vice President JAR/BL/mle Attachments:

1. Response to NRC Request for Additional Information

2. Relief Request in Accordance with 10 CFR 50.55a(g)(5)(iii) c: E. E. Collins, NRC Regional Administrator, Region IV L. E. Wilkins, NRC Project Manager J. C. Kirkland, NRC Senior Resident Inspector

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UC~10-0004 Page 1 OPPD Response to NRC Request for Additional Information

LlC-10-0004 Page 2 REQUEST FOR ADDITIONAL INFORMATION Please provide the following information:

1. The beginning and end dates for the Fourth Inservice Inspection interval.

2. The component materials for each weld.

3. The Code item numbers for each weld.

Answers:

1. Beginning of Fourth Inservice Inspection Interval: 10/31/2003 End of Fourth Inservice Inspection Interval: 09/25/2013

2. Each of the subject nozzle to safe end dissimilar metal welds are Alloy 82/182.

3. The welds listed in Table 1 are all Category B-F, Item Number 5.10.

LIC-1 0-0004 Page 1 RELIEF REQUEST IN ACCORDANCE WITH 10 CFR 50.55a(g)(5)(iii)

ALTERNATIVE TO THE DEPTH SIZING QUALIFICATION REQUIREMENT OF ASME SECTION XI, SUPPLEMENT 10 FOR PIPING EXAMINATIONS PERFORMED FROM THE INSIDE SURFACE FOR FORT CALHOUN STATION, UNIT NO.1

LI C-1 0-0004 Attachment 2 Page 2 ASME Code Components Affected Code class: 1 System: RC Examination Categories: B-F, Inservice Inspection Program TABLE 1 WELD NUMBERS BY lSI DESIGNATION Nozzle-to-Safe End Weld Item Location Weld Type 1 N1A Outlet Nozzle (0°) MRC-1/01 Shop 2 N2A Inlet Nozzle (60°) MRC-1/18 Shop 3 N2B Inlet Nozzle (120°) MRC-1/30 Shop 4 N1B Outlet Nozzle (180°) MRC-2101 Shop 5 N2C Inlet Nozzle (240°) MRC-2/18 Shop 6 N2D Inlet Nozzle (300°) MRC-2/30 Shop

Applicable Code Edition and Addenda

Fort Calhoun Station (FCS) is currently in the fourth 10-year Inservice Inspection (lSI) interval ending in 2013. The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) of record for the current 10-year lSI interval isSection XI, 1998 Edition, including Addenda through 2000 (Reference 1).

Applicable Code Requirement

The examination of Class 1 piping welds are required to be performed using procedures, personnel and equipment qualified to the criteria of the applicable ASME Code,Section XI, Appendix VIII, Supplements. The applicable supplement to this relief is 10, "QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS."

Paragraph 3.2, "Sizing Acceptance Criteria," Subparagraph (b) of Supplement 10, states that the "examination procedures, equipment, and personnel are qualified for depth-sizing when the RMS [root mean square] error of the flaw depth measurements, as compared to the true flaw depths, is less than or equal to O.125-inch (3.2mm)."

LI C-1 0-0004 Attachment 2 Page 3 Code Case N-695, "Qualification Requirements for Dissimilar Metal Piping Welds,Section XI, Division 1," provides alternative requirements to Appendix VIII, Supplement 10. Paragraph 3.3(c) of Code Case N-695 states, "Examination procedures, equipment, and personnel are qualified for depth-sizing when the RMS error of the flaw depth measurements, as compared to the true flaw depths, do not exceed 0.125-in. (3 mm)." Code Case N-695 is unconditionally approved for use through Regulatory Guide 1.147, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1," Revision 15.

Impracticality of Compliance OPPD successfully completed volumetric examinations of the FCS reactor pressure vessel (RPV) nozzle-to-safe end dissimilar metal (DM) welds from the inside surface for a Materials Reliability Program (MRP-139) inspection during the Fall 2009 refueling outage that began November 1, 2009. No flaws were found. These examinations are scheduled to be performed again for a 1O-year reactor vessel inservice inspection at the end of the current interval. OPPD will implement the NRC approved alternative requirements of Code Case N-695 for the qualification of procedures and personnel for examinations performed during these inspections.

This relief is submitted due to the impracticality of meeting the required 0.125- inch RMS value required by Code Case N-695. Code Case N-695 requires that qualified procedures and personnel shall demonstrate a flaw depth sizing error less than or equal to 0.125-inch RMS.

The nuclear power industry has attempted to qualify personnel and procedures for depth sizing examinations performed from the inside surface of dissimilar metal welds (Supplement 10, Code Case N-695) since November 2002. To date, no personnel or procedure has achieved less than or equal to the ASME Code required 0.125-inch RMS error (Reference 2).

The inability of examination procedures to achieve the required RMS value is primarily due to a combination of factors such as surface condition, scan access, base materials and the dendritic structure in the welds themselves. The combination of these factors has proven too difficult for procedures and personnel to achieve an RMS value that meet current Code requirements or Code Case N-695.

Burden Caused by Compliance The most recent attempt at achieving 0.125-inch RMS was in early 2008. This attempt, as well as previous attempts, did not achieve the required RMS values for personnel or procedures.

The qualification attempts have been substantia/. The attempts have involved multiple vendors, ultrasonic instruments, personnel and flaw depth sizing methodologies, all of which have been incapable of achieving the 0.125-inch RMS value.

The process of qualification for this type of flaw sizing is well established. The cost and effort involved to perform a successful demonstration is quantifiable when a capable technique is available. However, when a capable technique is not available, the costs and effort required for a successful demonstration cannot be easily quantified.

LI C-1 0-0004 Page 4 Proposed Alternative And Basis for Use Fort Calhoun proposes using an alternative depth-sizing RMS error value greater than the 0.125-inch RMS error value stated in Code Case N-695 for the examination of welds listed in Table 1 of this relief request. Pursuant to 10 CFR 50.55a(g)(6)(i), relief is requested to use an alternative depth-sizing RMS error value due to the impracticality of achieving the value stated in Code Case N-695.

As an alternative to the required RMS error stated in Code Case N-695 for procedure and personnel depth sizing, Fort Calhoun will add the difference between the required RMS value of 0.125-inch and the actual RMS value achieved by our inspection vendor to the flaw depth as determined during flaw sizing. The inspection vendor chosen has achieved an RMS of 0.189" for Supplement 10 welds.

Applying the difference between the required RMS error and the achieved RMS error to the actual flaw size, will ensure a conservative flaw bounding approach and provide an acceptable level of quality and safety.

Duration of Proposed Alternative The alternative requirements of this request will be applied for the duration of the Fourth 10-year lSI interval.

Precedents Similar relief requests have been granted to the following plants:

1. Seabrook Station, "Seabrook Station Unit No.1 Relief Request For Use Of An Alternate Flaw Sizing Methodology for the Second Inservice Inspection Interval (TAC No. M09785)," dated May 19,2009 (ML090850504)

2. Exelon Generating Company, LLC, "Braidwood Station, Units 1 and 2 - Relief Request (12R-49) Regarding Inservice Inspection Program Alternative Method (TAC Nos. MD5996 and M05997)," dated November 8, 2007 (ML072760048)

3. Southern Nuclear Operating Company Inc., "Joseph M. Farley Nuclear Plant Unit 1, and VogUe Electric Generating Plant, Units 1 and 2 - Evaluation of Relief Request ISI-GEN-ALT-06-02," (TAC Nos. MD 2482, MD2483 and MD2484), dated September 29, 2006 (ML062770359)

References

1. ASME Code,Section XI, 1998 Edition, including Addenda through 2000

2. Letter from EPRI (C. Latiolais) to OPPD (B. Lisowyj), "Summary of WESDYNE International, LLC Supplements 2 & 10.0epth Sizing Results Obtained from the Inside Surface," dated October 27, 2009