ML102300174

Response to Request for Clarification of Response to Request for Additional Information Regarding the 90-Day and 180-Day Steam Generator Tube Inspection Reports for Cycle 16 Refueling Outage, Dated July 16, 2010

ML102300174
Person / Time
Site:	Sequoyah
Issue date:	08/13/2010
From:	Krich R Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC ME3400, TAC ME3971
Download: ML102300174 (5)

Text

Tennessee Valley Authority 1101 Market Street, LP 3R Chattanooga, Tennessee 37402-2801 R. M. Krich Vice President Nuclear Licensing August 13, 2010 10 CFR 50.4 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Sequoyah Nuclear Plant, Unit 2 Facility License No. DPR-79 NRC Docket No. 50-328

Subject:

Response to Request for Clarification of "Response to Request for Additional Information Regarding the 90-Day and 180-Day Steam Generator Tube Inspection Reports for Cycle 16 Refueling Outage (TAC Nos. ME3400 and ME3971)," dated July 16, 2010

References:

1. E-mail from NRC (Siva Lingam) to TVA (Rod Cook), "Sequoyah, Unit 2-Steam Generator Tube Inspection Report (TAC Nos. ME3400 and ME3971)," dated August 2, 2010

2. Letter from TVA to NRC, "Response to Request for Additional Information Regarding the 90-Day and 180-Day Steam Generator Tube Inspection Reports for Cycle 16 Refueling Outage (TAC Nos. ME3400 and ME3971)," dated July 16, 2010 By e-mail dated August 2, 2010 (Reference 1), the NRC requested that the Tennessee Valley Authority provide clarification of several responses as contained in Reference 2.

The Enclosure to this letter provides that clarification.

There are no regulatory commitments contained in this letter.

printed on recycled paper

U.S. Nuclear Regulatory Commission Page 2 August 13, 2010 If you have any questions concerning this matter, please contact Rod Cook at (423) 751-2834.

Respectfully, R. M. Krich

Enclosure:

Response to Request for Clarification of "Response to Request for Additional Information Regarding the 90-Day and 180-Day Steam Generator Tube Inspection Reports for Cycle 16 Refueling Outage (TAC Nos. ME3400 and ME3971)," dated July 16, 2010 cc (Enclosure):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Sequoyah Nuclear Plant

ENCLOSURE Tennessee Valley Authority Sequoyah Nuclear Plant, Unit 2 Response to Request for Clarification of "Response to Request for Additional Information Regarding the 90-Day and 180-Day Steam Generator Tube Inspection Reports for Cycle 16 Refueling Outage (TAC Nos.

ME3400 and ME3971)," dated July 16, 2010 E-1

NRC Requested Clarification Number 1:

In your response to RAI I you indicated there were no "unacceptableor abnormal"conditions discovered. From the rest of the response, we would assume you detected erosion of the feedwater inlet distribution tee. Did you detect any other degradationof the secondary side internals?

TVA Response:

The original response statement referred to, "... ultrasonic testing thickness measurements of the feedwater inlet distribution tee were obtained to assess erosion for information," does not indicate erosion was found but rather information was gathered for erosion assessment. As stated in the second sentence of the response, "No unacceptable or abnormal conditions were discovered," remains a valid statement for the inspections.

NRC Requested Clarification Number 2:

In your response to RAI 5, the last part of the response seems to have been truncated.

What is the remainderof this response?

TVA Response:

The response was inadvertently truncated during editing. The entire response is provided below with the inadvertently truncated portion bolded:

[Response to RAI 5 from "Response to Request for Additional Information Regarding the 90-Day and 180-Day Steam Generator Tube Inspection Reports for Cycle 16 Refueling Outage (TAC Nos. ME3400 and ME3971)," dated July 16, 2010]

"The appropriate information from Tables 4-6 through 4-10 is summarized in Table 5.1.

Table 5.1: Ratios taken from Tables 4-6 throu 4-10 ISGI I SG21 SG3 G4 Toa Ratio of new indications in tubes tested with worn probe to number of tubes 0.028 0.048 0.068 0.046 0.048 tested with a worn probe (HL only)

Ratio of new indications in tubes tested with good probe to number of tubes 0.042 0.028 0.046 0.060 0.044 tested with a good probe (HL only) I_ I I I_ I The ratios of new indications previously tested with a worn probe are higher for SG [steam generator] Nos. 2 and 3, but lower for SG Nos. 1 and 4.

In addition to the information in Table 5.1, the percentage of new indications greater than 0.5 V will help assess if the population of new indications is significantly different.

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Table 5.2: Percentages taken from Tables 4-6 through 4-10 I SG1 SG2 I SG3] SG4 Total Percentage of new indications equal to or greater than 0.5 V in tubes tested with worn 60.0 54.5 64.4 52.4 57.6 probe Percentage of new indications equal to or greater than 0.5 V in tubes tested with good 52.0 64.4 64.0 45.5 54.9 probe I III Table 5.1 shows a variation from SG to SG. In some cases the ratio of new indications in tubes previously tested with a worn probe is greater than the ratio of new indications in tubes previously tested with a good probe, and in some cases it is smaller. Since the SGs experience essentially the same conditions, there is no known cause for a greater ratio in one SG than another. The ratios for the SGs combined are almost the same. Therefore, the differences are suspected to be a result of random variations in the detectability of these indications.

Table 5.2 shows the variation of the percent of new indications equal to or greater than 0.5 V.

These percentages also show some variation but do not show a trend that would indicate that there is a difference in the nature of the population of indications. It is reasonable to presume based on these ratios and percentages that the new indications detected that were previously tested with a worn probe and the new indications detected that were previously tested with a good probe are members of the same population. Therefore, no corrective action is necessary."

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