ML050420462

Relief Request B-5: Relief from the ASME Boiler and Pressure Vessel Code,Section III, Requirements for Use of Code Case N-698 for the Fabrication of a Replacement Reactor Vessel Head

ML050420462
Person / Time
Site:	Comanche Peak
Issue date:	04/04/2005
From:	Howe A NRC/NRR/DLPM/LPD4
To:	Blevins M TXU Energy
Thadani M, NRR/DLPM, 415-1476
References
TAC MC4909
Download: ML050420462 (7)

Text

April 4, 2005 Mr. Michael R. Blevins Senior Vice President &

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

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 1 - RELIEF REQUEST B-5: RELIEF FROM THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS BOILER AND PRESSURE VESSEL CODE, SECTION III, REQUIREMENTS FOR USE OF CODE CASE N-698 FOR THE FABRICATION OF A REPLACEMENT REACTOR VESSEL HEAD (TAC NO. MC4909)

Dear Mr. Blevins:

By letter dated September 29, 2004, TXU Generation Company LP (the licensee) submitted relief request B-5, pursuant to 50.55a(a)(3)(i) of Title 10 of the Code of Federal Regulations (10 CFR), seeking relief from American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code),Section III, requirements for the fabrication of a replacement reactor vessel head for Comanche Peak Steam Electric Station (CPSES), Unit 1. Specifically, the licensee proposed the use of the design stress intensity values of Code Case N-698, Design Stress Intensities and Yield Strength Values for UNS N06690 [nickel-chromium-iron alloy] With a Minimum Specified Yield Strength of 35 ksi [kilo-pounds per square inch] (240 Mpa), Class 1 Components,Section III, Division 1." The use of Code Case N-698 is currently pending endorsement by the Nuclear Regulatory Commission (NRC).

The NRC staff has evaluated the licensees request. Based on its evaluation, the NRC staff concludes that the licensees proposed alternative, as discussed in the licensees Relief Request B-5, provides an acceptable level of quality and safety; and that the proposed alternative satisfies the requirements of 10 CFR 50.55(a)(3)(i).

Therefore, the proposed alternative to use ASME Code Case N-698 is authorized by law for the CPSES, Unit 1 for the second 10-year inservice inspection interval or until Code Case N-698 is approved for general use by reference in Regulatory Guide 1.84. After that time, if the licensee wishes to continue to use Code Case N-698, the licensee must follow the conditions, if any, specified in the regulatory guide.

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.

Michael R. Blevins The NRC staffs evaluation and conclusions are contained in the enclosed safety evaluation. If there are any questions regarding this evaluation, please contact Mr. Mohan C. Thadani at (301) 415-1476.

Sincerely,

/RA/

Allen G Howe, Chief, Section 1 Project Directorate IV Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-445

Enclosure:

Safety Evaluation cc w/encl: See next page

ML050420462 *No significant change from input NRR-028 OFFICE PDIV-1/PM PDIV-1/LA EMCB/SC OGC PDIV-1/SC NAME MThadani DBaxley TChan* MWoods(NLO) AHowe DATE 3/30/05 3/30/05 02/01/05 3/22/05 4/4/05 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST B-5 FOR SECOND 10-YEAR INSERVICE INSPECTION INTERVAL TXU GENERATION COMPANY, LP COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 1 DOCKET NO. 50-445

1.0 INTRODUCTION

By letter dated September 29, 2004, (ML042800255), TXU Generation Company LP (the licensee) submitted, pursuant to 50.55a(a)(3)(i) of Title 10 of the Code of Federal Regulations (10 CFR), Relief Request B-5 from American Society of Mechanical Engineers (ASME) Boiler and pressure vessel code (Code)Section III requirements for the fabrication of a replacement reactor vessel head for Comanche Peak Steam Electric Station (CPES) Unit 1. Specifically, the licensee proposed the use of the design stress intensity values of Code Case N-698, Design Stress Intensities and Yield Strength Values for UNS N06690 [nickel-chromium-iron alloy] With a Minimum Specified Yield Strength of 35 ksi [kilo-pounds per square inch] (240 Mpa), Class 1 ComponentsSection III, Division 1." Use of Code Case N-698 is currently pending endorsement by the Nuclear Regulatory Commission (NRC).

2.0 REGULATORY EVALUATION

The regulation at 10 CFR 50.55a(a)(3) states that alternatives to the requirements of 10 CFR 50.55a(g) may be used, when authorized by the NRC, 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

ASME System/Component(s) for Which Relief is Requested (As Stated):

Relief is requested for Reactor Pressure Vessel (RPV) closure head manufactured to the requirements of Section III of 1989 Edition of the ASME Boiler and Pressure Vessel Code.

ENCLOSURE

Code Requirements for Which Relief is Requested (As Stated):

The replacement reactor vessel head manufactured to the requirements of Section III of the 1989 Edition of the ASME Code, Section NB-3112.4 requires the use of design stress intensity values for materials listed in the tables of Section II, Part D, Subpart 1.

Table 2B of Section II, Part D contains the design stress intensity values for Type Designation UNS N06690 for the SB-167 specification for Class 1 components.

Licensees Proposed Alternative The licensee stated that the ASME developed and approved ASME Code Case N-698, Design Stress Intensities and Yield Strength Values for UNS N06690 with a Minimum Specified Yield Strength of 35 ksi, Class 1 ComponentsSection III, Division 1, permitting the use of higher stress intensities associated with 35 ksi minimum yield strength, hot-worked UNS N06690 SB-167. The licensee is requesting that the design stress intensity values of Code Case N-698 be approved for use pursuant to 10 CFR 50.55a(a)(3)(i).

Licensees Basis for Relief Section II, Part B, Table 3 of the SB-167 specification provides an UNS N06690 yield strength that is dependent on manufactured condition. For seamless pipe and tube that are less than or equal to 5.0 inch outside diameter, Table 3 specifies a minimum yield strength of 30 ksi for hot-worked or hot-worked annealed and 35 ksi for cold-worked annealed.

The licensee stated that the UNS N06690 penetration tubes in the replacement reactor vessel closure head are manufactured using a hot-working process. Evaluation of the hot-worked UNS N06690 tubing has shown that a minimum yield strength of 35 ksi is inherent to the material. Because of the large margin in the minimum yield strength in ASME Section II, Table 3, an ASME Code Case was needed to permit the use of higher design stress intensity values (23.3 ksi in lieu of 20 ksi) when the minimum yield strength is specified as 35 ksi for hot-worked UNS N06690 Class 1 components.

NRC STAFF EVALUATION The licensee requested the use of UNS N06690 penetration tubes in the replacement reactor vessel closure head which are manufactured using a hot-working process. Evaluation of the hot-worked UNS N06690 tubing has shown that a minimum yield strength of 35 ksi is inherent to the material. Therefore, a design stress intensity value of 23.2 ksi that corresponds to a yield strength of 35 ksi as permitted by Code Case N-698 is justified. Further, the use of UNS N06690 in the SB-167 specification has been previously approved by the ASME as Code Case N-474-2, Design Stress Intensities and Yield Strength Values for UNS N06690 with a Minimum Specified Yield Strength of 35 ksi, Class I ComponentsSection III, Division 1, and accepted by the NRC in Regulatory Guide 1.85, Revision 31, dated March 1999. The design stress intensities and yield strengths of Code Case N-474-2 were incorporated into the 1999 Addenda for the annealed condition, however, the addenda did not specify the type of anneal. Based on the evaluation of hot-worked UNS N06690 SB-167, Code Case N-698 adjusts the yield strength values for hot-worked UNS N06690 to the evaluated value of 35 ksi minimum and provides

associated design stress intensity values that coincide with those of Section II, Part D, Subpart 1, of the 1999 Addenda. Therefore, the staff finds that the proposed use of the design stress intensity value of 23.3 ksi, as stated in Code Case N-698, is acceptable.

4.0 CONCLUSION

S Based on the above evaluation, the NRC staff concludes that the proposed alternative as discussed in the licensees request for relief provides an acceptable level of quality and safety.

Therefore, the proposed alternative to use Code Case N-698 is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for CPSES, Unit 1 for the second 10-year ISI interval or until Code Case N-698 is approved for general use by reference in Regulatory Guide 1.84. After that time, if the licensee wishes to continue to use Code Case N-698, the licensee must follow the conditions, if any, specified in the regulatory guide. 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: E. Reichelt Date: April 4, 2005

Comanche Peak Steam Electric Station cc:

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