ML070650651

Request for Relief No. C-1 for Second 10-Year Inservice Inspection Interval Class 2 Excess Letdown Heat Exchanger Head-to-Flange Weld

ML070650651
Person / Time
Site:	Comanche Peak
Issue date:	03/15/2007
From:	Terao D NRC/NRR/ADRO/DORL/LPLIV
To:	Blevins M TXU Power
Thadani, M C, NRR/DORL/LP4, 415-1476
References
TAC MC9185
Download: ML070650651 (8)

Text

March 15, 2007 Mr. M. R. Blevins Senior Vice President &

Chief Nuclear Officer TXU Power Attn: Regulatory Affairs Department P. O. Box 1002 Glen Rose, TX 76043

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION UNIT 2 - RELIEF REQUEST NO. C-1 FOR THE SECOND 10-YEAR INSERVICE INSPECTION INTERVAL RE: CLASS 2 EXCESS LETDOWN HEAT EXCHANGER HEAD-TO-FLANGE WELD (TAC NO. MC9185)

Dear Mr. Blevins:

By letter dated December 2, 2005, TXU Generation Company LP (TXU, the licensee) submitted Relief Request C-1 for Comanche Peak Steam Electric Station (CPSES), Unit 2. Pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a(g)(6)(i), the licensee requested relief from certain examination requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, on the basis of the impracticality of complying with those requirements. The licensee requested relief for the second 10-year inservice inspection (ISI) interval for CPSES, Unit 2, which began on August 3, 2004, and ends on August 2, 2014. The licensee proposed a reduced examination volume for the volumetric examination of the specified excess letdown heat exchanger (HX) head-to-flange weld as required by the ASME Code,Section XI, Article IWC-2500.

The Nuclear Regulatory Commission (NRC) staff has reviewed and evaluated the licensees relief request for CPSES, Unit 2, pursuant to the provisions of 10 CFR 50.55a(g)(6)(i).

Paragraph (g) of 10 CFR, Section 50.55a, requires that ISI of ASME Code Class 1, 2, and 3 components be performed in accordance with the applicable edition of Section XI of the ASME Code and applicable addenda, except where specific relief has been granted by NRC pursuant to 10 CFR 50.55(g)(6)(i).

Based on its review, the NRC staff concludes that the ASME Code,Section XI, requirement to perform the volumetric examination of the specified excess letdown HX head-to-flange weld, with essentially 100 percent volumetric coverage of the examination volume specified in Figure IWC-2500-1 of the ASME Code,Section XI, is impractical for CPSES, Unit 2.

Furthermore, the staff concludes that the licensee's alternative examination provides reasonable assurance of structural integrity for the subject component. Therefore, the licensee's request for relief is granted pursuant to 10 CFR 50.55a(g)(6)(i) for the second 10-year ISI interval for CPSES, Unit 2. Granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property or the common defence and security ,

and is otherwise in the public interest, giving due consideration to the burden upon the licensee that would result if the requirements were imposed on the facility.

M. R. Blevins All other requirements of the ASME Code,Section XI, for which relief has not been specifically requested and approved, remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

Sincerely,

/RA/

David Terao, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-446

Enclosure:

Safety Evaluation cc: See next page

ML070650651 *No significant change to SE input OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/CVIB/BC OGC - NLO NRR/LPL4/BC NAME MThadani LFeizollahi MMitchell* PMoulding DTerao DATE 3/13/07 3/12/07 2/28/07 3/14/07 3/15/07 Comanche Peak Steam Electric Station cc:

Senior Resident Inspector Mr. Richard A. Ratliff, Chief U.S. Nuclear Regulatory Commission Bureau of Radiation Control P.O. Box 2159 Texas Department of Health Glen Rose, TX 76403-2159 1100 West 49th Street Austin, TX 78756-3189 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Mr. Brian Almon 611 Ryan Plaza Drive, Suite 400 Public Utility Commission Arlington, TX 76011 William B. Travis Building P.O. Box 13326 Mr. Fred W. Madden, Director 1701 North Congress Avenue Regulatory Affairs Austin, TX 78701-3326 TXU Generation Company LP P.O. Box 1002 Ms. Susan M. Jablonski Glen Rose, TX 76043 Office of Permitting, Remediation and Registration George L. Edgar, Esq. Texas Commission on Environmental Morgan Lewis Quality 1111 Pennsylvania Avenue, NW MC-122 Washington, DC 20004 P.O. Box 13087 Austin, TX 78711-3087 County Judge P.O. Box 851 Terry Parks, Chief Inspector Glen Rose, TX 76043 Texas Department of Licensing and Regulation Environmental and Natural Boiler Program Resources Policy Director P.O. Box 12157 Office of the Governor Austin, TX 78711 P.O. Box 12428 Austin, TX 78711-3189 December 2004

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST C-1 COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 2 TXU POWER DOCKET NO. 50-446

1.0 INTRODUCTION

By letter dated December 2, 2005, TXU Generation Company LP (the licensee) submitted Relief Request C-1 for Comanche Peak Steam Electric Station (CPSES), Unit 2. The licensee requested relief from certain examination requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, on the basis of impracticality. The licensee requested relief for the second 10-year inservice inspection (ISI) interval of CPSES, Unit 2, which began on August 3, 2004, and ends on August 3, 2014. The licensee proposed a reduced examination volume for the volumetric examination of the specified excess letdown heat exchanger (HX) head-to-flange weld required by the ASME Code,Section XI, Article IWC-2500 for CPSES, Unit 2. The Nuclear Regulatory Commission (NRC) staff has reviewed and evaluated the licensees relief request pursuant to the provisions of Title 10 of Code of Federal Regulations (10 CFR) 50.55a(g)(6)(i).

2.0 REGULATORY EVALUATION

Paragraph (g) of 10 CFR, Section 50.55a, requires that inservice inspection (ISI) of ASME Code Class 1, 2, and 3 components be performed in accordance with the applicable edition of Section XI of the ASME Code and applicable addenda, except where specific relief has been granted by the NRC pursuant to 10 CFR 50.55a(g)(6)(i). Paragraph 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if the applicant 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.

Pursuant 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 the ASME Code,Section XI, Rules for lnservice 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 ISI of components and system pressure tests conducted during the first 10-year ISI interval and subsequent intervals comply with the requirements in the latest edition and addenda of the ASME Code,Section XI, incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 10-year interval, subject to the limitations and modifications listed therein. The applicable Code of record for the CPSES, Unit 2 ISI program is the 1998

Edition through the 2000 Addenda of the ASME Code,Section XI. The licensee requested relief for the second 10-year ISI interval for CPSES, Unit 2, which began on August 3, 2004, and ends on August 2, 2014.

3.0 TECHNICAL EVALUATION

ASME Code,Section XI Requirement The 1998 Edition through 2000 Addenda of ASME Code,Section XI, Article IWC-2500 requires that components be examined and tested as specified in Table IWC-2500-1 of the ASME Code,Section XI. Table IWC-2500-1, Examination Category C-A, Item Number C1.20 requires a volumetric examination of the excess letdown HX head-to-flange weld once during each 10-year ISI interval, with essentially 100 percent volumetric coverage of the examination volume specified in Figure IWC-2500-1 of the ASME Code,Section XI.

Component for which Relief is Requested Category Item Description C-A C1.20 Excess Letdown HX Head-to-Flange Weld The licensee has specifically requested relief for Head-to-Flange Weld TCX-2-1110-1 for the excess letdown HX at CPSES, Unit 2.

Licensee's Basis for Relief Request (As stated)

Interferences from the heat exchanger inlet and outlet nozzles and from the flange taper precluded ultrasonic examination of the volume required by Figure IWC-2500-1 [of the ASME Code, Section XI]. Approximately 25 [percent] of the required weld volume did not receive the full [Code-required] examination volume

[coverage]. The examination included axial and circumferential scans in both directions. Examination coverage was 100 [percent] circumferentially in both directions and approximately 50 [percent] in both axial directions.

There were no reportable indications identified by the volumetric examination performed on the accessible portion of the weld volume.

The examination coverage is limited by physical interferences from the heat exchanger inlet and outlet nozzles and from the flange taper as indicated in the attached pages [of the submittal]. These conditions make 100 [percent]

examination coverage impractical for this weld. In order to gain access to this weld for [full] examination [coverage] purposes, the heat exchanger would require a design modification. Imposition of this requirement would be a significant burden to TXU Power.

Licensee's Alternative Examination (As stated)

TXU Power has examined a significant portion of the weld, obtaining approximately 75 [percent overall] coverage of the weld.

Based on the high percentage of the examination volume completed and the lack of any reportable indications, there is a high level of confidence in the continued structural integrity of the weld. There is no anticipated impact upon the overall plant quality and safety, and the granting of the relief should not jeopardize the health and safety of the public.

Staff Evaluation The 1998 Edition through 2000 Addenda of the ASME Code,Section XI, Article IWC-2500, requires that components be examined and tested as specified in Table IWC-2500-1 of the ASME Code,Section XI. Table IWC-2500-1 requires a volumetric examination of the excess letdown HX head-to-flange weld for CPSES, Unit 2, with essentially 100 percent volumetric coverage of the examination volume as specified in Figure IWC-2500-1 of the ASME Code,Section XI. The requirement for essentially 100 percent coverage is defined in 10 CFR 50.55a(g)(6)(ii)(a) as greater than 90-percent coverage of the ASME Code, Section XI-required examination volume. Figure IWC-2500-1 of the ASME Code,Section XI, specifies that the total examination volume include the weld and the adjacent reactor vessel base metal material extending to a distance of one-half inch from the extremities of the weld crown at the outside surface of the HX shell.

The licensee conducted a volumetric examination of Head-to-Flange Weld TCX-2-1110-1 for the excess letdown HX specified in its relief request by conducting ultrasonic scans of the accessible regions using procedures and personnel qualified in accordance with the ASME Code,Section XI, Appendix III. The licensee conducted these examinations using two qualified ultrasonic transducers, scanning in four directions to the extent practical. By using these techniques, the licensee was able to obtain a coverage of approximately 75 percent of the ASME Code,Section XI, required examination volume. The 75-percent overall examination volume coverage is the mean volumetric coverage based on 100-percent coverage of the required examination volume in both circumferential directions and 50-percent coverage of the required examination volume in both axial directions. The licensee provided a detailed description of the conditions, that limited examination coverage. The limitation in examination coverage was attributed to interferences associated with the HX inlet and outlet nozzles and flange taper, which restricted access for scanning. The licensee indicated that the limited scope volumetric examination of the subject weld did not provide any indication of the presence of unacceptable flaws or other relevant conditions. The licensee concluded that, based on the overall coverage of 75 percent of the required examination volume and the lack of any reportable indications, there is a high level of confidence in the continued structural integrity of the weld.

Based on its own review the NRC staff agrees that, due to the interferences discussed above, it would be impractical for the licensee to satisfy the ASME Code,Section XI, requirements for essentially 100 percent coverage of this weld. In order to comply with the ASME Code,Section XI requirements, a design modification of the HX would have to be performed. This would impose a significant burden on the licensee. The NRC staff agrees that the weld examinations were conducted to the extent practical and provide reasonable assurance of structural integrity since approximately 75 percent overall examination volumr coverage was obtained, any significant pattern of degradation should have been detected during examination of the accessible weld volume.

Based on the above considerations, the NRC staff concludes that the ASME Code,Section XI, requirement to perform the volumetric examination of the specified excess letdown HX head-to-flange weld, with essentially 100-percent volumetric coverage of the examination volume specified in Figure IWC-2500-1 of the ASME Code,Section XI, is impractical for CPSES, Unit 2. Furthermore, the licensee's proposed alternative examination volume coverage provides reasonable assurance of structural integrity for the excess letdown HX head-to-flange weld.

4.0 CONCLUSION

The NRC staff concludes that the ASME Code,Section XI, requirement to perform the volumetric examination of the specified excess letdown HX head-to-flange weld, with essentially 100-percent volumetric coverage of the examination volume specified in Figure IWC-2500-1 of the ASME Code,Section XI, is impractical for CPSES, Unit 2. Furthermore, the staff concludes that the licensee's alternative examination provides reasonable assurance of structural integrity of the excess letdown HX.

Therefore, the licensee's request for relief is granted pursuant to 10 CFR 50.55a(g)(6)(i) for the second 10-year ISI interval at CPSES, Unit 2. Granting relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property or the common defence and security , and is otherwise in the public interest, giving due consideration to the burden upon the licensee that would result if the requirements were imposed on the facility. All other requirements of the ASME Code,Section XI, for which relief has not been specifically requested and approved, remain applicable including third-party review by the Authorized Nuclear Inservice Inspector.

Principal Contributor: C. Sydnor Date: March 15, 2007