ML113110092

Relief Request No. C-9, Reactor Pressure Vessel Flange Leak-off Piping Configuration, Second 10-Year Inservice Inspection Interval

ML113110092
Person / Time
Site:	Comanche Peak
Issue date:	12/19/2011
From:	Markley M Plant Licensing Branch IV
To:	Flores R Luminant Generation Co
Singal, Balwant, 415-3016, NRR/DORL/LPL4
References
TAC ME5214
Download: ML113110092 (8)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 19, 2011 Mr. Rafael Flores Senior Vice President and Chief Nuclear Officer Attention: Regulatory Affairs Luminant Generation Company LLC P.O. Box 1002 Glen Rose, TX 76043

SUBJECT:

COMANCHE PEAK NUCLEAR POWER PLANT, UNIT 1 - APPROVAL OF RELIEF REQUEST NO. C-9 FOR THE SECOND 10-YEAR INSERVICE INSPECTION INTERVAL (TAC NO. ME5214)

Dear Mr. Flores:

By letter dated December 15, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML103560595), as supplemented by letter dated October 13, 2011 (ADAMS Accession No. ML11292A052), Luminant Generation Company LLC (the licensee) submitted request for relief (RR) C-9 from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, inspection requirements pursuant to paragraph 50.55a(a)(3)(ii) of Title 10 of the Code of Federal Regulations (10 CFR) for Comanche Peak Nuclear Power Plant (CPNPP), Unit 1.

The Reactor Pressure Vessel (RPV) flange leak-off piping configuration precludes system pressure testing when the reactor vessel head is removed. The configuration also precludes pressurizing the line externally when the head is installed. The licensee stated that compliance with system pressure test requirements of ASME Code,Section XI, paragraph IWC-5222(a) would result in unnecessary hardship without a sufficient compensating increase in the level of quality and safety. In RR C-9, the licensee proposed to perform a visual examination (VT-2) of the accessible areas on the piping subjected to the static pressure head when reactor cavity is filled.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the licensee provided sufficient technical basis to find that compliance with the ASME Code requirements with respect to the RPV flange leak-off piping system pressure test. The alternative visual examination proposed by the licensee will detect boric acid accumulation resulting from any significant leakage.

Further, the licensee has proposed to monitor any signs of o-ring leakage through the leak-off line temperature. Hence, there is reasonable assurance that any leakage through the subject piping will be detected by use of the proposed alternative visual examination. Compliance with the requirements of ASME Code,Section XI, paragraph IWC-5222(a) results in unnecessary hardship without a sufficient compensating increase in the level of quality and safety.

RR C-9 is applicable to CPNPP, Unit 1's second 10-year inservice inspection interval, which began on August 13, 2000, and ended on August 12, 2010. The request was submitted on December 15, 2010. Alternative methods of examination are to be authorized by the NRC staff

R. Flores - 2 prior to the application of the alternative. Hence, the NRC staff is unable to grant authorization to use this alternative for the second 10-year interval. In its letter dated October 13, 2011, the licensee stated that examination of the RPV leak-off piping by use of the proposed alternative method was performed during refueling outage 1RF14 on April 26, 2010. CPNPP, Unit 1, was in Mode 6, the RPV head was removed, and the reactor cavity was filled. The associated ASME Code, Class 2 piping system was subject to the static pressure head when the reactor cavity was filled. VT-2 examination of the accessible areas of the piping systems was performed and no evidence of leakage was identified. Based on the results of the visual examination, the NRC staff does not see the need for the licensee to repeat the VT-2 examination.

The NRC's Region IV staff has been informed for any necessary follow-up or enforcement actions due to non-compliance with the NRC regulations.

All other ASME Code,Section XI, requirements 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, please contact Balwant K. Singal at 301-415-3016 or bye-mail at Balwant. Singal@nrc.gov.

Sincerely, Michael T. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-445

Enclosure:

As stated 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 REQUEST FOR RELIEF NO. C-9 SECOND 10-YEAR INSERVICE INSPECTION INTERVAL PROGRAM LUMINANT GENERATION COMPANY LLC COMANCHE PEAK NUCLEAR POWER PLANT, UNIT 1 DOCKET NO. 50-445

1.0 INTRODUCTION

By letter dated December 15, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML103560595), as supplemented by letter dated October 13, 2011 (ADAMS Accession No. ML11292A052), Luminant Generation Company LLC (the licensee) submitted request for relief (RR) C-9 from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, inspection requirements pursuant to paragraph 50.55a(a)(3)(ii) of Title 10 of the Code of Federal Regulations (10 CFR) for Comanche Peak Nuclear Power Plant (CPNPP), Unit 1.

The Reactor Pressure Vessel (RPV) flange leak-off piping configuration precludes system pressure testing when the reactor vessel head is removed. The configuration also precludes pressurizing the line externally when the head is installed. The licensee stated that compliance with system pressure test requirements of ASME Code,Section XI, paragraph IWC-5222(a) would result in unnecessary hardship without a sufficient compensating increase in the level of quality and safety. In RR C-9, the licensee proposed to perform a visual examination (VT-2) of the accessible areas on the piping subjected to the static pressure head when reactor cavity is filled.

RR C-9 is for the second 10-year inservice inspection (lSI) interval at CPNPP, Unit 1, which began on August 13, 2000, and ended on August 12, 2010. The RR is for use of an alternative method to comply with ASME Code,Section XI, pressure test requirements and was submitted on December 15, 2010.

2.0 REGULATORY EVALUATION

lSI of the ASME Code Class 1, 2, and 3 components is to be performed in accordance with Section XI of the ASME Code, and applicable addenda, as required by 10 CFR 50.55a(g),

except where specific relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). The regulations in 10 CFR 50.55a(a)(3) state that alternatives to the Enclosure

- 2 requirements of paragraph (g) may be used, when authorized by the U.S. Nuclear Regulatory Commission (NRC), if the licensee demonstrates that (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. The regulations in 10 CFR 50.55a(g)(5)(iii) state that if the licensee has determined that conformance with certain code requirements is impractical for its facility, the licensee shall notify the Commission and submit, as specified in 10 CFR 50.4, "Written communications," information to support the determinations.

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 120-month inspection interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code, which was incorporated by reference in 10 CFR 50.55a(b), 12 months prior to the start of the 120-month interval, subject to the conditions listed therein. The ASME Code of record for CPNPP, Unit 1 is the 1998 Edition through the 2000 Addenda, of the ASME Code,Section XI.

In addition, ASME Code,Section XI, 1995 Edition, 1996 Addenda is used for Appendix VIII, "Performance Demonstration for Ultrasonic Examination System."

3.0 TECHNICAL EVALUATION

The information provided by the licensee in support of the request for relief from, or alternatives to, ASME Code requirements has been evaluated and the bases for disposition are documented below.

RR C-9. ASME Code.Section XI. Alternative Pressure Testinq Requirements for the RPV Flange Leak-off Piping ASME Code Requirement ASME Code,Section XI, paragraph IWC-2500, Table IWC-2500-1. Code Category C-H, Item Number C7.1 0 requires that all Class 2 pressure-retaining components be subject to a system leakage test per IWC-5220 with a Visual, VT-2 examination each inspection period. The system leakage test is performed at the pressure obtained while the subject portion of the system is performing its normal operating function or at the system pressure developed during a test conducted to verify system operability.

In accordance with IWC-5222(a), the pressure-retaining boundary includes the portion of the system required to operate or support the safety function up to and including the first normally closed valve (including a safety or relief valve) or a valve capable of automatic closure when the safety function is required.

- 3 Licensee's ASME Code Relief Request In accordance with 10 CFR 50.55a(a)(3)(ii), the licensee requested relieffrom pressure testing requirements for nominal pipe size (NPS) 1/3-inch RPV Flange Seal Leak-Off piping, line numbers BRP-RC-1-RB-038, BRP-RC-1-RB-039, BRP-RC-1-RB-040, BRP-RC-1-RB-041, and M1-0250.

Licensee's Basis for Relief Request and Proposed Alternatives (as stated by the licensee)

The Reactor Pressure Vessel (RPV) head flange seal leak detection piping is separated from the reactor coolant pressure boundary by one passive membrane, which is an O-ring located on the inner vessel flange shown in Attachment [2 to the licensee's letter dated December 15, 2010]. A second O-ring is located on the outside of the tap in the vessel flange. Failure of the inner o-ring is the only condition under which this line is pressurized. Therefore, the line is not expected to be pressurized during the system pressure test following a refueling outage. The configuration of this piping precludes system pressure testing while the vessel head is removed because the time required by personnel for the installation and removal of a threaded plug in the flange face to act as a pressure boundary for the test would incur significant dose (estimated 20-40 mR [millirem]/min), which would be an ALARA [as low as reasonably achievable] concern. This activity would also present a Foreign Material Exclusion issue for the 1/8" plug that would be required to be installed to complete a leakage test at pressure.

The configuration also precludes pressurizing the line externally with the head installed. The top head of the vessel contains two grooves that hold the o-rings.

The o-rings are held in place by a series of retainer clips that are housed in recessed cavities in the flange face. If a pressure test were to be performed with the head on, the inner o-ring would be pressurized in a direction opposite to its design function. This test pressure would result in a net inward force on the inner o-ring that would tend to push it into the recessed cavity that houses the retainer clips. The thin o-ring material would likely be damaged by the inward force.

In lieu of the requirements of [ASME Code,Section XI,] IWC-5222(b), a VT-2 visual examination of the accessible areas will be performed each period on the piping subjected to the static pressure head when the reactor cavity is filled. This test will be part of the reactor coolant Class 2 leakage test.

If the inner o-ring should leak during the operating cycle it will be identified by an increase in temperature of the leak-off line above ambient temperature. This high temperature would actuate an alarm in the Control Room, which would be closely monitored by procedurally controlled operator actions allowing identification of any further compensatory actions required. This leakage would be collected in the Reactor Coolant Drain Tank.

Additionally, the flange seal leak-off line is essentially a leakage collection/detection system and the line would only function as a Class 2

-4 pressure boundary if the inner o-ring fails, thereby pressurizing the line. If any significant leakage does occur in the leak-off line piping itself during this time of pressurization then it would clearly exhibit boric acid accumulation and be discernable during the proposed VT-2 visual examination that will be performed unpressurized as proposed in this request

NRC Staff Evaluation

In order to perform the required test, the licensee would need to install and remove a threaded plug in the flange face to act as a pressure boundary. This would result in a significant dose to personnel. Alternatively, the licensee could pressurize between the reactor vessel head o-rings, but this could possibly damage the inner o-ring. If the inner o-ring were damaged, the licensee would need to replace the o-ring set. The time and radiation exposure to remove and reinstall the RPV head to replace the o-rings would be a significant burden on the licensee, with no obvious benefit. The licensee has proposed performing a VT-2 visual examination of the accessible areas each period on the piping subjected to the static pressure head when the reactor cavity is filled. If any significant leakage does occur, boric acid accumulation should be detected in the VT-2 visual examination. Further, the licensee will monitor for any signs of o-ring leakage through the leak-off line temperature. There is reasonable assurance that any problems in the subject piping would be detected through these measures. The proposed alternative provides reasonable assurance of structural integrity. Requiring compliance with the IWC-5222(a) system pressure test requirements results in an unnecessary hardship without a sufficient compensating increase in the level of quality and safety.

4.0 CONCLUSION

As set forth above, the NRC staff determined that the licensee has implemented an appropriate alternative to the ASME Code,Section XI pressure testing requirements and that complying with the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. However, the request is for CPNPP, Unit 1's second 10-year lSI interval, which ended on August 12, 2010. RR C-9 was submitted on December 15, 2010. Alternative methods of examination are to be authorized by the NRC staff prior to the application of the alternative. As such, the NRC staff is unable to authorize use of this alternative for the second 1O-year interval.

In its letter dated October 13, 2011, the licensee stated that examination of the RPV leak-off piping by use of the proposed alternative method was performed during refueling outage 1RF14 on April 26, 2010. CPNPP, Unit 1, was in Mode 6, the RPV head was removed, and the reactor cavity was filled. The associated ASME Code, Class 2 piping system was subject to the static pressure head when the reactor cavity was filled. VT-2 examination of the accessible areas of the piping systems was performed and no evidence of leakage was identified. As the alternative provides reasonable assurance of structural integrity, the NRC staff does not see the need for the licensee to repeat the VT-2 examination previously implemented.

- 5 For any future lSI 10-yesr intervals, for which the relief from the ASME Code,Section XI pressure testing requirements is desired, the licensee will need to request relief, and obtain NRC staff approval prior to implementation.

The NRC's Region IV staff has been informed for any necessary follow up or enforcement actions due to non-compliance with the NRC regulations.

Principal Contributor: M. Audrain Date: December 19. 2011

R. Flores - 2 prior to the application of the alternative. Hence, the NRC staff is unable to grant authorization to use this alternative for the second 10-year interval. In its letter dated October 13, 2011, the licensee stated that examination of the RPV leak-off piping by use of the proposed altemative method was performed during refueling outage 1RF14 on April 26, 2010. CPNPP, Unit 1, was in Mode 6, the RPV head was removed, and the reactor cavity was filled. The associated ASME Code, Class 2 piping system was subject to the static pressure head when the reactor cavity was filled. VT-2 examination of the accessible areas of the piping systems was performed and no evidence of leakage was identified. Based on the results of the visual examination, the NRC staff does not see the need for the licensee to repeat the VT-2 examination.

The NRC's Region IV staff has been informed for any necessary follow-up or enforcement actions due to non-compliance with the NRC regulations.

All other ASME Code,Section XI, requirements 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, please contact Balwant K. Singal at 301-415-3016 or bye-mail at Balwant.Singal@nrc.gov. ..

Sincerely.

IRN Michael T. Markley. Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-445

Enclosure:

As stated cc w/encl: Distribution via Listserv DISTRIBUTION:

PUBLIC RidsNrrPMCoinanchePeak Resource LPLIV Reading RidsNrrLAJBurkhardt Resource RidsAcrsAcnw_MailCTR Resource RidsOgcRp Resource RidsNrrDeEpnb Resource RidsRgn4MailCenter Resource, R~sNrrDo~DprResouree MAudrain, NRR/DE/EPNB RidsNrrDorlLpl4 Resource MFranke, EDO RIV ADAMS Accession No ML113110092 *SE email dated 11/2/2011 OFFICE NRR/LPL4/PM NRR/LPL4/LA NRRlDE/EPNB/BC NRR/LPL4/BC NAME BSingal JBurkhardt TLupold" MMarkley DATE 1211/11 11130/11 1212111 12119/11 OFFICIAL AGENCY RECORD