ML16278A601
| ML16278A601 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 09/28/2016 |
| From: | Lawrence D Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 16-196A | |
| Download: ML16278A601 (7) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 September 28, 2016 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT 2 Serial No.
SPS LIC/CGL Docket No.
License No.
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION 2015 STEAM GENERATOR INSERVICE INSPECTION REPORT 16-196A R1 50-281 DPR-37 By letter dated May 10, 2016 (Serial No.16-196), Virginia Electric and Power Company (Dominion) submitted information summarizing the results of steam generator (SG) tube inspections performed at Surry Power Station Unit 2 during the Fall 2015 refueling outage. On August 29, 2016, the NRC requested additional information related to the SG inspections. The NRC's questions and Dominion's responses are provided in the attachment to this letter.
If you have any questions or require additional information, please contact Ms. Candee Lovett at (757) 365-2178.
Doug as Lawrence Director S ation Safety & Licensing Surry Power Station Attachment - Response to NRC Request for Additional Information Regarding Fall 2015 Steam Generator lnservice Inspection Report - Surry Power Station Unit 2 Commitments made in this letter: None
cc:
U.S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303 Ms. K. R. Cotton-Gross - Surry NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 0 8G-9A 11555 Rockville Pike Rockville, Maryland 20852 Dr. V. Sreenivas - North Anna NRC Project Manager U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 0 8G-9A 11555 Rockville Pike Rockville, Maryland 20852 NRC Senior Resident Inspector Surry Power Station Mr. R. A. Smith Authorized Nuclear Inspector Surry Power Station Serial No.: 16-196A Docket No.: 50-281 Page 2 of 2
ATTACHMENT Serial No.: 16-196A Docket No.: 50-281 Response to*NRC Request for Additional Information Regarding Fall 2015 Steam Generator lnservice Inspection Report Surry Power Station Unit 2 Virginia Electric and Power Company (Dominion)
Serial No.: 16-196A Docket No.: 50-281 Attachment RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING SURRY UNIT 2 FALL 2015 STEAM GENERATOR TUBE INSPECTIONS By letter dated May 10, 2016 (Agencywide Documents Access and Management Systems (ADAMS) Accession No. ML16141A117), Virginia Electric and Power Company (Dominion) submitted steam generator tube inspection results from the Fall 2015 inspections at Surry Power Station, Unit 2. In order to complete its review, the NRC staff requests the following additional information. The Dominion responses.are provided below.
- 1. For the bobbin coil exams in rows 1 ~ 5 in Table 1, it appears that there is one less exam reported for the cold-leg than for the hot-leg in SG C (463 versus 464). Please confirm these numbers and clarify the reason, if correct.
Response
Four hundred sixty-four (464) tubes in Rows 1 to 5 were inspected with bobbin probes from the cold leg in SG C. These tubes included 463 that were inspected from 07C to TEC with a 0.720 inch diameter bobbin probe and one tube (SG C R1C58) that was inspected from 07C to TEC with a 0.700 inch diameter probe.
Tube R1 C58 was included in the original Table 1 under the "C/L Straight Restricted" category. This tube has a relatively large historical dent at the top of the tubesheet on the cold leg.
The dent prevents passage of the 0.720 inch diameter bobbin probe, but allows passage of the 0.700 inch diameter bobbin probe. The cold leg straight section of this tube was inspected with. a 0.700 inch diameter probe. *To ensure effective examination of the tube, the entire cold leg and u-bend of this tube were also examined with a 0.680 inch diameter +Point' probe. The hot leg was examined with a 0.720 inch diameter bobbin probe.
During review of Table 1 while preparing this response, it was discovered that one inspection in SG C R20C62 was included in the "C/L Straight Restricted" category, but should have been included in the "H/L Straight Restricted" category. Following is a revised Table 1 which reclassifies this inspection and also includes additional clarifying information on the restricted tubes.
Altogether, there were three restricted tubes (SG A R3C9, SG C R1C58, and SG C R20C62) that required inspections of different extents and/or inspections with 0.700 inch diameter bobbin probes. The restrictions in these three tubes have been present in previous examinations.
No degradation was detected in any of these tubes.
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Serial No.: 16-196A Docket No.: 50-281 Attachment Table 1 - Eddy Current Testing Examination Scope Scope Description Extent SIG A SIG B SIG C Bobbin Coil Exams Full Length TEHTEC 2849 2831 H/L CandyCane (Row 3-5) 07CTEH 278 282 H/L Straight (R 1-2) 07HTEH 185 182 H/L Straiqht Restricted (SG C R20C62) 02HTEH 1
H/L Straight Restricted (SG C R20C62*)
07HTEH 1
C/L CandyCane Restricted (SG C R20C62) 03HTEC 1
C/L Straight Restricted 07CTEC 1
C/L Straight (R 1-5) 07CTEC 462 463 Array Exams H/L TSH Array (Non-Baffle Plate)
TSH01H 834 444 843 H/L TSH Array (Baffle Plate)
TSHBPH 2478 1260 2453 C/L TSC Array (Non-Baffle Plate)
TSC01C 834 842**
C/L TSC Array (Baffle Plate)
TSCBPC 2478 2453 MRPC Exams Ubend +PT (Row 1-2) 07H07C 185 182 MRPC Special Interest H/L Previous Indications Various 120 172 H/L Previous Restricted 02H03H 1
C/L Previous Restricted Various 8
H/L Current Indications Various 97 7
92 Ubend Current Indications Various 2
1 C/L Previous Indications Various 8
7 C/L Current Indications Various 36 20 Indications For MaqBias Probe Various 1
2 Additional RPC TEHTSH 2
Total 10848 1713 10838
- 0. 700 inch diameter bobbin probes. All other bobbin inspections were performed with 0.720 inch diameter probes.
- The cold leg tubesheet region of SG C R 1 C58 was inspected with a downsized
+Point' probe in lieu of array due to a restriction at the top of the tubesheet. Hence, the number of cold leg array inspections is one less than the number of hot leg array inspections.
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Serial No.: 16-196A Docket No.: 50-281 Attachment
- 2. For the array exams in Table 1, it appears that there is one less array exam reported for the cold-leg tubesheet than for the hot-leg tubesheet in SG C (842 versus 843).
Please confirm these numbers and clarify the reason, if correct.
Response
This discrepancy in the number of tubes is also related to tube R1C58 in SG C. As noted in the Response to Question 1, the dent at the top of the cold leg tubesheet prevents passage of the 0.720" diameter array probe.
Therefore, the cold leg tubesheet region of this tube was examined with a 0.680 inch diameter +Point' probe in lieu of an array probe. The +Point' examination of the cold leg tubesheet region of this tube is counted in the "Special Interest" section of Table 1.
No degradation was identified.
- 3. According to Table 5, two foreign object wear indications in SG A, and three foreign object wear indications in SG C, were initially reported in 2015 that were present in prior outages.
Table 5 shows that these indications had maximum depths ranging from 19 - 27 percent through-wall and had not changed since they were initially detected in the previous outages. Please confirm and* discuss why these indications were not reported previously, or clarify the information in the table (since volumetric indications of these depths would normally be readily detectible with a high probability of detection).
Response
The five indications in question were not reported in previous outages due to either re-characterization of the flaws from previous outages or reduced probability of detection (POD) for these low voltage signals. The depths provided by Examination Technique Specification Sheet (ETSS) 27901.1 are believed to be conservative, as discussed below. Newly reported foreign object wear indications in this depth range have been common at Surry since implementation of ETSS 27901.1.
The two indications in tube SG A R4C37 have been present and reported as either local geometry variation (LGV) or manufacturing burnish mark (MBM) for the last several inspections.
Upon closer review of the eddy current signals, these two indications were re-characterized as foreign object wear during the 2015 outage.
The indications in SG C (R30C48, R36C32, and R45C42) were all low voltage signals that had not been previously reported with +Point'. Two of the indications (R36C32 and R45C42) were included with the array results during the previous inspection (and were not specifically reported because there was no degradation found (NDF) with +Point'). EPRI ETSS 27901.1 was used for depth sizing these Page 3 of 4
Serial No.: 16-196A Docket No.: 50-281 Attachment flaws. Relative to other available techniques, this technique can give relatively deep measurements for low voltage signals. The deepest of these indications in SG C had a maximum +Point' voltage of 0.13 volts and a corresponding measured depth of 21 % TW. Signals of this small amplitude are subject to analyst discretion, as well as signal interference from support structures, tubesheet interfaces, and/or sludge buildup on the outer diameter of the tube.
The sizing obtained for low voltage signals using ETSS 27901.1 is believed to be overestimated for signals below approximately 0.2 volts. This is based on a review of the calibration setpoints relative to the calibration curve built with the setpoints.
The setpoint for a 0.1 volt flaw in ETSS 27901.1 is 13% TW. However, when the calibration curve is built, a 0.1 volt flaw has a measured depth of 19% TW. Hence, the depths of flaws in this* voltage range are believed to be overestimated by approximately 6% TW.
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