ML092230647

Fourth 10-Year Inservice Inspection Plan-Nondestructive Examination

ML092230647
Person / Time
Site:	North Anna  (NPF-004)
Issue date:	08/13/2009
From:	Undine Shoop Plant Licensing Branch II
To:	Heacock D Virginia Electric & Power Co (VEPCO)
Sreenivas V.NRR/DORL/LPL2-1 415-2597
References
TAC MD9955, TAC ME0266, TAC ME0267, TAC ME0270
Download: ML092230647 (11)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 August 13, 2009 Mr. David A. Heacock President and Chief Nuclear Officer Virginia Electric and Power Company Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711

SUBJECT:

NORTH ANNA POWER STATION, UNIT NO.1, FOURTH 10-YEAR INSERVICE INSPECTION PLAN - NONDESTRUCTIVE EXAMINATION (TAC NOS. MD9955, ME0266, ME0270 AND ME0267)

Dear Mr. Heacock:

By letter dated October 7,2008, Virginia Electric and Power Company (the licensee) requested relief from certain requirements of Section XI of the American Society of Mechanical Engineers, Boiler and Pressure Vessel Code (ASME Code), under the provisions of Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Section 50.55a for the fourth 10-year inservice inspection (lSI) interval for North Anna Power Station, Unit NO.1. This letter specifically addresses requests NDE-001 through NDE-003 and NDE-006 on nondestructive examination for Class 1 components. By letter dated July 30, 2009, the licensee withdrew NDE-003.

For Relief Request (RR) Nos. NDE-001 and NDE-006, the NRC staff finds that the ASME Code requirements would impose a hardship without a compensating increase in quality and safety.

The licensee's proposed alternative provides reasonable assurance of leak-tight integrity and structural integrity of the subject components. Therefore, the NRC staff authorizes the requested reliefs pursuant to 10 CFR 50.55a(a)(3)(ii) for the fourth 10-year lSI interval.

The NRC staff finds that the proposed alternative to continue to use the automated reactor pressure vessel inspection tool will provide an acceptable level of quality and safety. Therefore, the NRC staff authorizes the alternative in RR NDE-002 pursuant to 10 CFR 50.55a(a)(3)(i) for the fourth 10-year lSI interval.

The fourth 10-year lSI program for components and component supports is scheduled to commence on May 1, 2009, and to be completed by April 30, 2019.

D. Heacock

- 2 All other requirements of ASME Code,Section XI for which relief has not been specifically requested remain applicable, including a third-party review by the Authorized Nuclear Inservice Inspector. If you have any questions concerning this matter, please contact Dr. V. Sreenivas at (301) 415-2597.

Sincerely, Ut1/{C~\\),J{1eCy}

Undine Shoop, Acting Branch Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-338

Enclosure:

Safety Evaluation cc w/encl: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL PROGRAM RELIEF NDE-001, NDE-002 and NDE-006 FOR COMPONENT AND COMPONENT SUPPORTS WELD EXAMINATIONS NORTH ANNA POWER STATION, UNIT NO.1 VIRGINIA ELECTRIC AND POWER COMPANY DOCKET NO. 50-338

1.0 INTRODUCTION

By letter dated October 7,2008, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML082880160) Virginia Electric and Power Company (the licensee) submitted Relief Requests NDE-001, NDE-002, NDE-003, and NDE-006 for its fourth 10-year inservice inspection (lSI) interval for component and component support weld examinations at North Anna Power Station, Unit NO.1 (NAPS 1). The licensee requested relief from certain lSI and examination requirements of the American Society of Mechanical Engineers, Boiler and Pressure Vessel Code (ASME Code),Section XI, lSI program. NDE-003 was later withdrawn by a letter from the licensee to the NRC dated July 30, 2009.

The NRC staff has evaluated the licensee's Relief Requests and determined that the proposed alternatives provide an acceptable level of quality and safety for NDE-002 and complying with the specified requirement would result in hardship without a compensating increase in the level of quality and safety for NDE-001 and NDE-006, pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Section 50.55a(a)(3)(i) and Section 50-55a(a)(3)(ii) for the fourth 10-year lSI interval scheduled to commence on May 1, 2009, and to be completed by April 30, 2019.

2.0 REGULATORY REQUIREMENTS According to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in ASME Code,Section XI, "Rules for In-service Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that in-service examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by Enclosure

- 2 reference in 10 CFR 50.55a(b) twelve months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein and subject to Commission approval.

The applicable edition of the Code for NAPS-1, fourth 10-year lSI interval, which began May 1, 2009, is the 2004 Edition of ASME Code,Section XI with no addenda.

As stated in 10 CFR 50.55a(a)(3), the Nuclear Regulatory Commission (NRC) may allow for alternatives to the requirements from paragraph (g)(4) of the regulations that are stated above if (i) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

3.0 TECHNICAL EVALUATION

3.1 Requests for Relief NDE-1, Pertaining to Class 1 and 2 Piping, Vessel, and Component Welds 3.1.1 ASME Code Requirement The 2004 Edition of ASME Code,Section XI, requires that a reference system as delineated in IWA-2600 shall be established for all welds subject to surface or vOlumetric examination. The system shall permit identification and location of each weld.

3.1.2 Licensee's ASME Code Relief Request Pursuant to 10 CFR 50.55a(a)(3)(ii), the licensee has requested relief from establishing a new reference system in compliance with requirements delineated in IWA-2600 of the 2004 Edition of ASME Code,Section XI, for Class 1 and 2 piping, vessel, and component welds. The licensee requested that relief be granted for the inservice examination to be performed during the fourth 1O-year lSI interval.

3.1.3 Licensee's Basis for Relief Request NAPS-1 was designed and built before the requirement that a weld reference system be established. The implementation of this ASME Code, Section XI-required weld reference system was considered to be impractical because it could not be attained within the scope and schedule of existing outages. An alternative weld reference system was established for the second lSI interval within the plant on the Class 1 and 2 piping, vessel, and component welds and its use was approved by the NRC for the second and third lSI intervals. The provisions proposed in this alternative are consistent with those proposed and accepted previously by the NRC. The licensee states that:

Continued use of the alternative reference system is reasonable because it provides an acceptable level of quality and safety. To reject the alternative reference system already in use would require the plant to establish either the system required by Section XI of the ASME Code in IWA-2600 or some other alternative system yet to be developed. In either case, significant effort would be expended to achieve compliance with the requirements of IWA-2600 without any justifiable gain in quality or safety.

- 3 3.1.4 Licensee's Proposed Alternative For the fourth interval, the licensee intends to continue to use the markings that were made for the second interval, which were subsequently used for the third interval as well. Welds that contain recordable indications shall be appropriately marked to ensure identification and location for future examinations. The reference system and marks will be permanently fixed on the weld.

3.1.5 Staff's Evaluation The NRC staff has reviewed the information concerning lSI Program Request for Relief NOE-001 for the fourth 10-year lSI interval of NAPS-1 pertaining to Class 1 and 2 piping, vessel and component welds. The licensee proposed to continue to use the existing markings made in the second (also used for the third) lSI interval in its updated weld isometrics, and the existing markings and weld isometrics had been reviewed and approved by the NRC. As further explained in the request, these isometrics provide a detailed identification of weld location, zero point and direction of examination. Therefore, the markings and isometrics provide a sound basis for future examinations and serve the purpose and intent of IWA-2600 of the 2004 ASME Code,Section XI, although not totally in conformance with the ASME Code in details for a weld reference system. In addition, continued use of the existing markings and isometrics will allow consistent comparison of future examination results with the previous examination results.

Based on the information provided in this Request for Relief, the NRC staff has determined that it would be a considerable hardship for the licensee to meet the conditions to the extent required by the ASME Code. To completely meet the scope of 2004 ASME Code-specified requirements for a weld reference system, changes in schedule and extensions in duration of the next plant refueling outage would be necessary. Imposition of this requirement would cause a considerable hardship on the licensee without a compensating increase in the level of quality and safety. The licensee's proposed alternative reference approach provides reasonable assurance of acceptable examinations. Therefore, the alternative in Request for Relief NOE-001 is authorized pursuant to 10 CFR 50.55a(a)(3)(ii) for the fourth lSI interval at NAPS-1.

3.2 Request for Relief NOE-002, lSI of Categories B-A, B-O, and B-F Welds 3.2.1 Identification of Components The components in the reactor pressure vessel (RPV) that are the subject of this request are the pressure retaining welds (Examination Category B-A), the RPV nozzle area (Examination Category B-O), and the dissimilar metal welds joining the RPV nozzles to the reactor coolant loop piping (Examination Category B-F) that are examined by the automated RPV examination tool.

3.2.2 ASME Code Requirement The 2004 Edition of the ASME Code,Section XI requires a reference system, described in IWA-2600, be established for RPV welds subject to surface or volumetric examination. The system shall permit identification, location, and placing reference points on the center line of each weld to ensure repeatability of examination.

- 4 3.2.3 Licensee's ASME Code Relief Request Pursuant to 10 CFR 50.55a(a)(3)(ii), the licensee requested relief from establishing a new reference system in compliance with requirements delineated in IWA-2600 of the 2004 Edition of the ASME Code,Section XI, for Categories B-A, B-O and B-F welds that are examined by the automated RPV examination tool. The licensee requested that relief be granted for the examinations to be performed during the fourth 10-year lSI interval.

3.2.4 Licensee's Basis for Relief Request The licensee states in the relief request that, "the original construction requirements of NAPS-1 did not require the establishment of a weld reference system on the inside of the RPV for subsequent lSI of the RPV and associated RPV nozzle-to-piping dissimilar metal welds as now required by IWA-2600. An automated examination tool has been used in the past to perform these examinations. The automated examination tool establishes its reference point using a known reference point on the RPV. This point allows the device to repeat examination locations without the necessity of any other reference systems. The tool determines its location on the inside of the RPV by the use of an electronic encoder system, which provides for sufficient repeatability".

Establishing the reference system required by IWA-2600 on the inside of an operational RPV is a significant hardship that will provide no increase in quality or safety. Therefore, the licensee is requesting approval of this proposed alternative reference system under the provisions of 10 CFR 50.55a(a)(3)(ii).

3.2.5 Licensee's Proposed Alternative Examination The licensee proposed to conduct the subject examinations with the automated RPV examination tool that will continue to establish its reference system based upon the existing reference points and the electronic encoding system. This is the same alternative that was proposed and accepted for use in the previous interval.

3.2.6 Staffs Evaluation The NRC staff has reviewed the information concerning the lSI Program Request for Relief NOE-002 for the fourth 10-year lSI interval of NAPS-1 pertaining to the Categories B-A, B-O, and B-F welds. The 2004 ASME Code,Section XI requirements for a weld reference system as found in section IWA-2600 are meant to ensure repeatability of examinations for each successive interval. However, these requirements did not exist during the early period after construction of the NAPS-1 RPV, and as a result; NAPS-1 did not establish a weld reference system as required by the 2004 Edition of the ASME Code.

The licensee has proposed in this requested alternative to continue to use the automated RPV inspection tool for establishing the reference system based upon the existing zero reference point in the RPV. The staff concurs with the licensee that the alternative proposed here will provide sufficient repeatability for the planned fourth lSI interval and does meet the purpose and intent of IWA-2600 of the 2004 ASME Code. In addition, the proposed alternative will provide a direct comparison for all future examination results with the previous examination results.

Therefore, the staff finds that the licensee's proposed alternative will provide an acceptable level

- 5 of quality and safety and the staff can authorize the alternative in Request for Relief NDE-002 pursuant to 10 CFR 50.55a(a)(3)(i) for the fourth lSI interval at NAPS-1.

3.3 Request for Relief NDE-006, lSI for Specific Welds on Heat Exchangers 3.3.1 Identification of Components Specific welds on the residual heat removal (1-RH-E-1A and 18) and regenerative heat exchangers (1-CH-E-3) are identified below:

1-RH-E-1A and 18 Welds Description Category/Item Class 1

Head Circumferential Weld C-AlC1.20 2

Shell Circumferential Weld C-AlC1.10 3A,38,4A,48 Reinforcing Plate Welds to C-8/C2.31 Nozzle and Vessel 1-CH-E-3 2

2 2

Welds Description Category/Item Class 3,7, 11 2,6,10 1,4,5,8,9,12 13,14,15, 16, 17, 18 23,24,25,26,27,28 13NIR, 14NIR, 15NIR, Tubesheet-to-head Tubesheet-to-shell Circumferential head Nozzle-to-vessel Nozzle-to-vessel Nozzle inside radius 8-8/82.60 8-8/82.80 8-8/82.51 8-0/83.150 8-0/83.150 8-0/83.160 1

1 1

1 1

1 16NIR, 17NIR, 18NIR Nozzle inside radius 8-0/83.160 1

23NIR, 24NIR, 25NIR Nozzle inside radius 8-0/83.160 26NIR, 27NIR, 28NIR Nozzle inside radius 8-0/83.160 3.3.2 ASME Code Requirements 1

1 The 2004 Edition of ASME Code,Section XI requires an lSI program that includes vOlumetric examinations for items identified in Categories 8-8, 8-0, and C-A referenced above.

For Category C-8, Item C2.31, the 2004 Edition requires a surface examination of the identified weld surface and associated material.

3.3.3 Licensee's ASME Code Relief Request Pursuant to 10 CFR 50.55a(a)(3)(ii), the licensee requested relief from the ASME Code-required volumetric examination of the subject components found in the residual heat removal (1-RH-E-1A and 18) and regenerative (1-CH-E-3) heat exchangers. The licensee also requested relief from the ASME Code-required surface examination of the subject C2.31 welds found in the residual heat removal heat exchangers (1-RH-E-1A and 18).

- 6 3.3.4 Licensee's Basis for Relief:

The regenerative heat exchanger (1-CH-E-3) provides preheat for the normal charging water flowing into the reactor coolant system (RCS). The residual heat removal heat exchangers (1-RH-E-1A and 1B) are designed to cool the RCS during plant shutdown operations. These heat exchangers were designed, constructed, and inspected to ASME Code rules prior to being put into service. Since the ASME Code-required preservice exams, visual VT-2 examinations have been performed in accordance with NRC-approved relief requests as part of the system pressure test program that is conducted before restarting the reactor after a refueling outage.

In terms of fabrication, geometric design, inspection requirements and geometric restrictions, the heat exchanger components at NAPS-1 are typical of the heat exchangers described in the report prepared by Westinghouse Owner's group (WOG) project MUHP 5093, Working Group Inservice Inspection Optimization Action 97-01 (Boiler Code Item BC03-338), "Technical Basis for Revision of Inspection Requirements for Regenerative and Residual Heat Exchangers,"

August 2004.

As stated in the WOG report, these components were designed and installed before the development of the lSI requirements by ASME and are not designed for performance of ultrasonic examination. The small diameter of the vessel and nozzles of the regenerative heat exchanger makes a meaningful ultrasonic examination very time consuming. The physical limitations would substantially diminish the ability to discriminate flaw indications from geometric indications. Referring to the residual heat removal heat exchangers, interference with the lower support and interference with inlet and outlet piping leads to only partial coverage for examination of the head and shell circumferential welds.

Two other factors (flaw tolerance and risk assessment) presented in the Westinghouse report for these components were considered by the ASME committee to support Code Case N-706-1.

This case code expanded and clarified the requirements of N-706 to include the surface examinations of the saddle welds (Item B2.31) and the nozzle inside radius volumetric examinations (Item C3.160). The WOG report concluded that the heat exchangers have a large flaw tolerance and that significant leakage would be expected long before any failure occurred.

Fatigue crack growth was determined to be extremely slow even in the most highly stressed region. Plus, these heat exchangers do not have a severe duty cycle. Thus, detailed inspections are not required to ensure their integrity.

The WOG report performed a risk evaluation using the accepted methodology applied for risk-informed lSI piping inspection programs. The following conclusions were drawn:

1) Safety equipment required to respond to a potential event is unaffected.

2) Potential for loss of pressure boundary integrity is negligible.

3) No safety analysis margins are changed.

4) Leak-before-break conditions are expected (Le., there are no core damage consequences associated with leakage).

Thus, elimination of the subject inspections would not be expected to result in a significant increase in risk.

Industry experience with these components has been good. There have been no through-wall leaks on these components or components of similar design as reported in the industry and as

- 7 discussed in the WOG report. The only related leak in the United States occurred in January 2004 at San Onofre, Unit 3 on the letdown line exiting the regenerative heat exchanger. In that case, the failure was caused by excessive vibration on the piping line and is not an indication of failure on the actual heat exchanger.

Furthermore, these components are located in high radiation fields. The estimated personnel dose to perform the ASME Code-required ultrasonic and surface examinations on the regenerative heat exchanger is 13 man-rem, and it is estimated that 4.5 man-rem would be required to meet the examination requirements per interval for the residual heat removal heat exchangers. In view of the significant dose expenditure and limited examination results, the benefit derived from performing the ASME Code-required examinations is not commensurate with the cost and hardship.

3.3.5 Licensee's Proposed Alternative In accordance with the provisions of 10 CFR 50.55a(a)(3)(ii), approval is requested to use the requirements of Code Case N-706-1, "Alternative Examination Requirements of Table IWB-2500-1 and IWC-2500-1 for PWR Stainless Steel Residual and Regenerative Heat Exchangers,Section XI, Division 1," as an alternative to the ASME Code requirements listed above in Section 3.3.2; Code Case N-706-1 requires VT-2 examinations to be performed as acceptable alternatives. The VT-2 examination would be performed as part of the system leakage test that is required by Categories B-P and C-H.

Additionally, the Improved Technical Specifications (ITSs) establish limits on RCS leakage to one gallon per minute of unidentified leakage and no identified leakage in the pressure boundary. To monitor for leakage, the ITSs also require that (a) one containment sump (level or discharge flow) monitor, and (b) one containment atmosphere radioactivity monitor (gaseous or particulate) be operable during modes 1,2,3, and 4. In addition, the plant must verify RCS operational leakage is within limits by performance of an RCS inventory balance at a frequency not exceeding 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The ITSs also require that a channel check of the required containment atmosphere radioactivity monitor be performed at a frequency not exceeding 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

Based on the issues discussed above, the licensee believes that compliance with the ASME Code-required examinations would result in a hardship due to excessive personnel radiation exposure and the geometric examination difficulties without a compensation increase in quality and safety.

3.3.6 Staffs Evaluation The NRC staff has reviewed the information concerning the lSI Program Request for Relief NDE-006 for the fourth 10-year lSI interval of NAPS-1 pertaining to specific components on the residual heat removal (1-RH-E-1A) and regenerative (1-CH-E-3) heat exchangers. As stated by the licensee, these heat exchangers were not designed for meaningful ultrasonic examination.

The workers would receive approximately 17.5 man-rem of radiation exposure if the lSI examinations were performed as required by the ASME Code. In addition, the WOG report demonstrates with a flaw tolerance and a risk assessment that eliminating the inspections would not result in a significant increase in risk. Thus, the licensee has requested relief from the volumetric examinations associated with Categories B-B, B-D and C-A components for the

- 8 residual heat removal and regenerative heat exchangers and from the surface examinations of the weld surface associated with the Category C-B item identified in Section 3.3.1 in this SE.

The licensee has proposed an alternative that requires them to perform the RCS leak rate surveillance and the containment atmosphere particulate radioactivity monitoring as required by the ITSs, and to perform a system leakage test and VT-2 visual examination prior to start up after each refueling outage. The staff finds that the VT-2 visual examination and the ITSs requirements for leakage and radiation monitoring will provide reasonable assurance that continued in-service structural integrity will be maintained. Therefore, the Request for Relief NDE-006 is granted pursuant to 10 CFR 50.55a(a)(3)(ii) for the fourth10-year lSI interval.

4.0 CONCLUSION

The NRC staff has completed its review of the information provided by the licensee. The staff concludes that the information provided by the licensee supports the granting of alternatives NDE-001 and NDE-006 pursuant to 10 CFR 50.55a(a)(3)(ii) as requested because the inspections required by Section XI of the ASME Code would result in hardship without a compensating increase in the level of quality and safety. For NDE-002, the staff concludes that the alternative can be granted according to the provisions of 10 CFR 50.55a(a)(3)(i) rather than the provisions of 10 CFR 50.55a(a)(3)(ii), as requested, because the alternative provides an acceptable level of quality and safety.

All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

Principal Contributor: Patrick 1. Purtscher, DCI/CVIB Date: August 13, 2009

D. Heacock

- 2 All other requirements of ASME Code,Section XI for which relief has not been specifically requested remain applicable, including a third-party review by the Authorized Nuclear Inservice Inspector. If you have any questions concerning this matter, please contact Dr. V. Sreenivas at (301) 415-2597.

Sincerely, IRA!

Undine Shoop, Acting Branch Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-338

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UShoop DATE 08/12/09 08/12/09 8103109 08/13/09 OFFICIAL RECORD COpy