CNL-15-205, Response to Additional Question Regarding Request for Relief WBN-2/PSI-3 for Inaccessible Steam Generator Lower Shell-to-Cone Weld SG-4B-5-2

Response to Additional Question Regarding Request for Relief WBN-2/PSI-3 for Inaccessible Steam Generator Lower Shell-to-Cone Weld SG-4B-5-2

ML15266A457
Person / Time
Site:	Watts Bar
Issue date:	09/23/2015
From:	James Shea Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-15-205, TAC MF6474
Download: ML15266A457 (2)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-15-205 September 23, 2015 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-001 Watts Bar Nuclear Plant, Unit 2 Construction Permit No. CPPR-92 NRC Docket No. 50-391

Subject:

WATTS BAR NUCLEAR PLANT (WBN) UNIT 2 - RESPONSE TO ADDITIONAL QUESTION REGARDING REQUEST FOR RELIEF WBN-2/PSl-3 FOR INACCESSIBLE STEAM GENERATOR LOWER SHELL-TO-CONE WELD SG-4B-5-2 (TAC No. MF6474)

References:

1. TVA Letter to NRC, CNL-15-119, Watts Bar Nuclear Plant (WBN) Unit 2 -

Request For Relief WBN-2/PSI-3 For Inaccessible Steam Generator Lower Shell-To-Cone Weld SG-4B-5-2, dated July 10, 2015 (ML15196A455)

2. TVA Letter to NRC, CNL-15-179, Watts Bar Nuclear Plant (WBN) Unit 2 -

Response to Request for Additional Information Regarding Request for Relief WBN-2/PSI-3 for Inaccessible Steam Generator Lower Shell-to-Cone Weld SG-4B-5-2 (TAC No. MF6474), dated September 4, 2015 (ML15247A565)

3. Email from NRC to TVA, SG Weld RAI, dated September 22, 2015 On July 10, 2015, Tennessee Valley Authority (TVA) submitted to the Nuclear Regulatory Commission (NRC) the Watts Bar Nuclear Plant (WBN), Unit 2, Request for Relief WBN-2/PSI-3 for inaccessible steam generator (SG) lower shell-to-cone weld SG-4B-5-2 (Reference 1). TVA responded on September 4, 2015 (Reference 2) to an NRC request for additional information (RAI) concerning the Request for Relief submitted in Reference 1. On September 22, 2015, the NRC submitted a clarification question by electronic mail (Reference 3) regarding TVAs response to the RAI provided in Reference 2. The purpose of this letter is to provide TVAs response to the clarification question received in Reference 3.

U.S. Nuclear Regulatory Commission CNL-15-205 Page 2 September 23, 2015 By Reference 3, the NRC requested the following clarification :

"Please provide industry operating experience on steam generators of the same vintage as the WBN, Unit 2 (up to the year of their replacements) to support that there were no inservice safety issues caused by detected flaws in the subject welds."

In response , TVA's Inspection Services Organization , Non-Destructive Examination (NOE)

Level Ill examiner (ultrasonic examination) , was consulted . Based on the Level Ill examiner's 40 plus years of NOE experience, there have been no known inservice failures of the SG weld joint in question. The WBN Unit 2 SGs are Westinghouse Model 03 SGs.

Based on discussion with TVA's WBN Nuclear Steam Supply System vendor, the WBN Unit 2 SGs are the only Model 03 SGs remaining in the industry that have not been replaced based on the reduced longevity of the SG tubes . Due to SG replacements , there is no longer industry operating experience related to these types of SGs.

There are no new regulatory commitments made in this letter. Should you have questions regarding this submittal , please contact Gordon Arent at (423) 365-2004.

Vi e President, Nuclear Licensing cc:

NRC Regional Administrator, Region II NRC Project Manager - Watts Bar Nuclear Plant, Unit 2 NRC Senior Resident Inspector - Watts Bar Nuclear Plant, Unit 2