ML20212J631

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SER Accepting Request for Relief from ASME Boiler & Pressure Vessel Code,Section Xi,Requirements for Certain Inservice Insp at Plant,Unit 1
ML20212J631
Person / Time
Site: Sequoyah Tennessee Valley Authority icon.png
Issue date: 10/01/1999
From:
NRC (Affiliation Not Assigned)
To:
Shared Package
ML20212J604 List:
References
NUDOCS 9910050223
Download: ML20212J631 (5)


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NUCLEAR REGULATORY COMMISSION K

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE RELIEF FROM CERTAIN WELD INSPECTIONS SEQUOYAH NUCLEAR PLANT. UNIT 1 TENNESSEE VALLEY AUTHORITY DOCKET NO. 50-327 1,0 INTRODUCTION Inservice inspection (ISI) of the American Society of Mechanical Engineers (ASME) Code l

Class 1,2, and 3 components shall be performed in accordance with Section XI of the A,SME Boiler and Pressure Vessel Code (ASME Code) and applicable addenda as required by Title 10,

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l Code of Federal Reaulations, Part 50,10 CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).

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' 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 pre-

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service examination requirements, set forth in the ASME Code,Section XI, " Rules for Inservice j

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 inservice examination of components and system pressure tests conducted during the first ISI 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of the Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) l 12 months prior to the start of the 120-month ISI interval, subject to the limitations and l

modifications listed therein subject to Commission approval.

Pursuant to 10 CFR 50.55a(g)(5)(iii), if the licensee determines that conformance with an l

examination requirement of Section XI of the ASME Code is not practical for its facility, information shall be submitted to the Commission in support of that determination and a request

- made for relief from the ASME Code requirement. After evaluation of the determination, pursuant to 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose requirements that are determined to be authorized by law, will not endanger life, property, or the j-common defense and security, and are otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed. The

' applicable edition of the Code for the Sequoyah Nuclear Plant, Unit 1 (SON Unit 1), second r

10-year ISI interval, which began December 16,1995, is the 1989 Edition of ASMC %

Section XI.

ENCLOSURE 9910050223 991001 PDR ADOCK 05000327 P

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' o By letter dated June 8,1999, the licensee for SON Unit 1, the Tennessee Valley Authority (TVA), submitted Request for Relief 1-ISI-14, seeking relief from the ASME Code,Section XI, requirements to perform 100 percent volumetric examination of two ASME Code Class 2 full-penetration fillet-reinforced welds (CSHXW-6-B and CSHXW-7-B) ut the inlet and outlet nozzle-to-shell connections of the SON Unit 1 containment spray heat exchanger. These two welds were examined for preservice following replacement of the exchanger during the SON Unit 1 Cycle 9 refueling outage, which was at the end of the first period of the second 10-year ISI interval.

This request for relief is pursuant to 10 CFR 50.55a(g)(5)(iii) for the second 10-year ISI interval.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed and evaluated TVA's proposed relief request pursuant to 10 CFR 50.55a(g)(6)(i). The staff's evaluation of the subject request for relief is in the following section.

2.0 EVALUATION The information provided by the licensee in support of the Request for Relief 1 ISI-14, Examination Category C-8, item C2.21, pertaining to two nozzle-to-shell welds of containment spray heat exchanger 18, has been evaluated, and the bases for disposition are documented below.

4 2.1 Code Reauirement:

ASME Code,Section XI, Table IWC-2500-1, Examination Category C-8, item C2.21 requires 100 percent surface and volumetric examinations of nozzle-to-shell weld per Figure IWC-2600-4 for each 10-year ISI interval.

2.2 Licensee's Code Relief Reauest:

j Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the Code-required 100 percent volumetric examination coverage for inlet nozzle-to-shell weld (CSHXW-6-B) and outlet l

nozzle-to-shell weld (CSHXW-7-8) of SON Unit 1 containment spray heat exchanger 18.

Welds CSHXW-6-B and CSHXW-7-B were examined for preservice following containment sprg l

heat sxchanger replacement during the SON Unit 1 Cycle 9 refueling outage (end of the first

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j period of the second 10-year inspection interval). The licensee requested that relief be granteti for the pteservice examination and the inservice examination to be performed during the second l

10-year inspection interval.

l 2.3 Licensee's Basis for Relief Reauest (as stated):

"The design configuration of the containment spray heat exchanger nozzle precludes an ultrason?c examination of the required volume for the following nozzle-to-shell welds:

CSHXW-6-B and CSHXW-7-B. The design configuration limits ultrasonic examination to approximately 64 percent of the required examination volume on each weld.

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"The ultrasonic volumetric examination is limited due to design configuration of a set-on type nozzle, which is welded to the shell with full penetration fillet reinforced weld. Scanning from the vessel side of the weld is not practical due to the asymmetrical inside surface of the vessel wall relative to the nozzle.

" Scans for flaws located transverse to the weld were limited due *o the weld joint configuration which limited search unit contact and movement. Approximately 50 percent of the required coverage was achieved for detection of tran= verse oriented flaws. The axial scans were limited due to the fillet weld size which was equal to the nozzle wall thickness. Each weld received 78 percent of the required coverage for detection of parallel oriented flaws w;tn the axial scans from the nozzle side utilizing both 45-degrees shear waves and 60-degrees refracted longitudinal waves.

" Performance of an ultrasonic volumetric examination of essentially 100 percent of the required volume of the full penetration fillet reinforced welds CSHXW-6-8 and CSHXW-7-8 would be impractical. The surface examination on 100 percent of the weld and adjacent metal [and] the maximum extent practical ultrasonic examination of the subject welds provide [] reasonable assurance of an acceptable level of quality and safety. Significant degradation, if present, would have been detected during the surface examination and ultrasonic examination that was performed on the subject welds. As a result, assurance of structural integrity for these welds is provided by the alternative examinations that were performed.

"Therefore, pursuant to 10CFR50 55a(g)(5)(iii), it is requested that relief be granted for the preservice examination that was performed during the Unit 1 Cycle 9 refueling outage of the first period of the second 10-year inspection interval and the inservice examination to be performed during the second 10-year inspection interval."

2.4 Licensee's Procosed Alternative Examination (as stated):

"In lieu of the code requiring 100 percent ultrasonic examination, an ultrasonic examination was i

l performed on accessible areas of each weld to the maximum extent practical, given the physical limitations of the set-on type nozzle-to-shell weld."

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2.5 Staff Evaluation:

The NRC staff has reviewed the information concerning the ISI program request for relief submitted in the letter dated June 8,1999, for the second 10-year ISI interval and for the preservice examination conducted during replacement of SQN Unit 1 containment spray heat exchanger 1B and for the second ISI interval inservice examination. The current Code requires that the subject nozzle-to-shell welds be 100 percent surface and volumetric examination during the preservice inspection and during the subsequent ISIinterval. As noted above, the present ISI interval started in 1995 and adopted the 1989 Edition of the Code. (The staff notes that the Code of record for the 1" ISI interval did not require 100 percent volumetric examination of these welds. Therefore, an ISI ultrasonic inspection was not required, and therefore not attempted, prior to October 1998 during heat exchanger replacement.) As reported by the licensee, volumetric examination coverage is limited to 64 percent due to design configuration of set-on type nozzle, which had caused scanning difficulty from the vessel side of the weld due to the asymmetrical inside surface of the vessel wall relative to the nozzle. Based on the information

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provided in this request for relief, the staff has determined that it is impractical to volumetrically examine the subject welds to the extent required by the Code. For complete examination coverage, redesign and modification of the configuration of containment spray piping and heat exchanger nozzle would be necessary. Imposition of this requirement would cause a 1

' considerable burden on the licensee.-

4.0 CONCLUSION

The licensee proposed in its request for relief performance of ultrasonic examination on the accessible areas of each subject weld to the maximum extent practical. A complete surface -

i examination can be performed in addition, preservice examination of the subject welds was

< completed during the SQN Unit 1 Cycle 9 refueling outage and no unacceptable indications were detected. Based on the significant portion of the volumetric examinations completed and the complete surface examination performed, the staff believes that it is reasonable to conclude that a pattern of degradation, if present, would have been detected. As a result, reasonable assurance of continued structuralintegrity has been provided. Therefore, the NRC hereby i

grants the requated relief pursuant to 10 CFR 50.55a(g)(6)(i). Granting the relief is authorized

. by law, will not endanger life, property, or the common defense and security, and is otherwise in i

the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.

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Principal Contributor: S. Hou, NRR l

Date: October 1, 1999 1

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a Mr. J. A. Scalic-SEQUOYAH NUCLEAR PLANT Tennessee Valk y Authority cc:

- Mr. Karl W. Singer, enior Vice President Mr. Pedro Salas, Manager Nuclear Operations Licensing and Industry Affairs Tennesseo Valley At"nority Sequoyah Nuclear Plant 6A Lookout Place Tennessee Valley Authority 1101 Market Street P.O. Box 2000

. Chattanooga, TN 37402-2801' Soddy Daisy, TN 37379 Mr. Jack A. Bailey Mr. D. L. Koehl, Plant Manager

- Vice President

' Sequoyah Nuclear Plant Engineering & Technical Services Tennessee Valley Authority Tennessee Valley Authority P.O. Box 2000 6A Lookout Place Soddy Daisy, TN 37379 1101 Market Street Chattanooga, TN.37402-2801 Mr. Melvin C. Shannon Senior Resident inspector Mr. Masoud Bajestani Sequoyah Nuclear Plant l

Site Vice President U.S. Nuclea Regulatory Commission l

Sequoyah Nuclear Plant 2600 Igou Ferry Road Tennessee Valley Authority Soddy Daisy, TN 37379 l

P.O. Box 2000 l

Soddy Daisy, TN 37379 Mr. Michael H. Mobley, Director l

TN Dept. of Environment & Conservation l

General Counsel Division of Radiological Health Tennessee Valley Authority 3rd Floor, L and C Annex ET 10H 401 Church Street 400 West Summit Hill Drive Nashville, TN 37243-1532 Knoxville, TN 37902 County Executive Mr. N. C. Kazanas, General Manager Hamilton County Courthouse Nuclear Assurance Chattanooga, TN 37402-2801 Tennessee Valley Authoritv SM Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. Mark J. Burzynski, Manager Nuclear Licensing Tennessee Valley Authority 4X Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801