ML18114A105

End of Cycle 18 Steam Generator Tube Inspection Report

ML18114A105
Person / Time
Site:	Millstone
Issue date:	04/19/2018
From:	Daugherty J Dominion Energy Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
18-116
Download: ML18114A105 (18)

Text

Dominion Energy Nuclear Connecticut, Inc.

Rt 156, Rope Ferry Road, Waterford, CT 06385 ~ Dominion Dominion Energy.com ~ Energy APR .1 9 2018 U.S. Nuclear Regulatory Commission Serial No.18-116 Attention: Document Control Desk NSSL/MLC RO Washington, DC 20555 Docket No. 50-423 License No. NPF-49 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3 END OF CYCLE 18 STEAM GENERATOR TUBE INSPECTION REPORT In accordance with the Millstone Power Station Unit 3 Technical Specification (TS)

Section 6.9.1.7, Dominion Energy Nuclear Connecticut, Inc. hereby submits the End of Cycle 18 (EOC18) Steam Generator (SG) Tube Inspection report. The report is submitted within 180 days after initial entry into MODE 4 following completion of the fall 2017 SG inspections performed in accordance with TS 6.8.4.g, "Steam Generator (SG)

Program." Initial entry into Mode 4 occurred on November 11, 2017. contains the EOC18 SG Tube Inspection report. Attachment 2 contains a list of acronyms.

The report addresses the following reporting requirements:

a. The scope of inspections performed on each SG,

b. Degradation mechanisms found,

c. Nondestructive examination techniques utilized for each degradation mechanism,

d. Location, orientation (if linear), and measured sizes (if available) of service induced indications,

e. Number of tubes plugged during the inspection outage for each degradation mechanism,

f. The number and percentage of tubes plugged to date and the effective plugging percentage in each steam generator,

g. The results of condition monitoring, including the results of tube pulls and in-situ testing,

h. The primary to secondary LEAKAGE rate observed in each SG (if it is not practical to assign the LEAKAGE to an individual SG, the entire primary to secondary LEAKAGE should be conservatively assumed to be from one SG) during the cycle preceding the inspection which is the subject of the report,

i. The calculated accident induced leakage rate from the portion of the tubes below 15.2 inches from the top of the tubesheet for the most limiting accident in the most limiting SG. In addition, if the calculated accident induced leakage rate from the most limiting accident is less than 2.49 times the maximum operational primary to /

secondary leakage rate, the report should describe how it was determined; and J,_,,tD

,Jf_((

Serial No.18-116 Docket No. 50-423 Page 2 of 2

j. The results of monitoring for tube axial* displacement (slippage). If slippage is discovered, the implications of the discovery and corrective action shall be provided.

If you have any questions or require additional information, please contact Mr. Jeffry A.

Langan at (860) 444-5544.

Sincerely, J/7~

~-ife"Jice President - Millstone Attachments:

1) Millstone Power Station Unit 3, End of Cycle 18 Steam Generator Tube Inspection Report

2) Acronyms Commitments made in this letter: None cc: U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia,,PA 19406-2713 R. V. Guzman Senior Project Manager - Millstone Power Station U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08 C2 11555 Rockville Pike Rockville, MD 20852-2738 NRG Senior Resident Inspector Millstone Power Station

Serial No.18-116 Docket No. 50-423 Attachment 1 Millstone Power Station Unit 3 End of Cycle 18 Steam Generator Tube Inspection Report MILLSTONE POWER STATION UNIT 3 DOMINION ENERGY NUCLEAR CONNECTICUT, INC. (DNC)

Serial No.18-116 Docket No. 50-423 Attachment 1, Page 1 of 13 End of Cycle 18 Steam Generator Tube Inspection Report Transmittal of this report satisfies Millstone Power Station Unit 3 (MPS3) Technical Specification (TS) 6.9.1. 7 which specifies that a report shall be submitted within 180 days after the initial entry into MODE 4 following completion of an inspection performed in accordance with TS 6.8.4.g, Steam Generator (SG) Program. During MPS3's fall 2017 refueling outage (3R18), steam generator inspections were completed in accordance with TS 6.8.4.g. Initial entry into Mode 4 occurred on November 11, 2017; therefore, this report is required to be submitted to the NRC by May 10, 2018.

This attachment provides a summary of the MPS3 steam generator inspection results and specific responses to each of the TS 6.9.1. 7 reporting requirements. Attachment 2 contains a list of acronyms.

Introduction MPS3 is a four loop Westinghouse pressurized water reactor with Westinghouse Model F SGs. Each SG was fabricated with 5626 U-bend thermally treated lnconel 600 tubes. The tubing is nominally 0.688 inches outside diameter with a 0.040 inch nominal wall thickness.

During SG fabrication, the tubes were hydraulically expanded over the full depth of the 21.23-inch thick tubesheet. The tubesheet was drilled on a square pitch with 0.98 inch spacing. There are 59 rows and 122 columns in each SG. The radius of row 1 Li-bends is 2.20 inches. Li-bends in rows 1 through 10 were stress relieved after being formed.

Secondary side tube support structures include a flow distribution baffle, seven plate supports with broached holes on the vertical section of the tubes, and six anti-vibration bars (AVBs) on the U-bend section of the tubes.

The SGs have accrued 24.76 Effective Full Power Years (EFPY) of operation as of the End of Cycle (EOC) 18 (October 2017).

TS 6.9.1. 7 Reporting Requirements This section provides responses to each of the reporting requirements specified in MPS3 TS 6.9.1.7. Bold wording represents TS verbiage. The required information is provided immediately following the restatement of each reporting requirement.

A report shall be submitted within 180 days after the initial entry into MODE 4 following completion of an inspection performed in accordance with TS 6.8.4.g, Steam Generator (SG) Program. The report shall include:

a. The scope of inspections performed on each SG, One hundred percent of the operational tubes in SG A and SG C, a total of 11,181 tubes, were inspected full length using eddy current examination techniques. The majority of the tubing length was examined with bobbin probes. The Li-bends of rows 1 and 2 (475 in-service tubes) were examined with a Motorized Rotating Probe Coil (MRPC) technique in addition to the bobbin probe examination of the straight legs of the tubes. An additional augmented sample of 608 tube locations was examined with a MRPC probe. The augmented sample inspections were performed in areas of special interest including hot leg

Serial No.18-116 Docket No. 50-423 Attachment 1, Page 2 of 13 expansion transitions, tube overexpansion locations within the hot leg tubesheet, dents, as well as locations where the bobbin probe response was ambiguous. An additional augmented sample of 12,721 tube locations was inspected with an array coil probe. The array coil probe sample included 100% *of the hot leg top-of-tubesheet (TTS) locations (11,181 tubes), and approximately 13% of the cold leg TTS locations (1,540 tubes). The extent of the TTS examinations was from the first support structure detected above the secondary face of the tubesheet to 15.2 inches below the secondary face of the tubesheet; except for the tubes categorized as high residual stress tubes. For the high residual stress tubes, the extent included the entire straight length of the tubes on the hot leg.

Table 1 3R18 ECT Examination Summary

~ *-- .

***- SGA * .* SG B* 5(:i C sGb . iotai Number of Installed Tubes 5626 5626 5626 5626 22504 Number of Tubes In-service at start of 3Rl8 5577 5601 5604 5535 22317 Number of Tubes Inspected w/Bobbin Probe 5577 N/A 5604 N/A 11181 Number of Tube Locations Inspected w/Array Probe 6363 N/A 6358 N/A 12721 Number of Exams Performed w/MRPC 542 N/A 541 N/A 1083 Previously Plugged Tubes 49 25 22 91 187 Tubes Plugged During 3R18 2 0 0 0 2 During 3R18, secondary side activities were performed in SGs A, B, C, and D and included the following:

• High pressure sludge lancing.

• Post-sludge lancing visual examination of the TTS annulus and no-tube lane to assess as-left material condition and cleanliness, and to identify and remove any retrievable foreign objects.

• Visual investigation of accessible locations having eddy current indications potentially related to foreign objects, and if present, removal of those retrievable foreign objects.

• Secondary side upper internal examinations within SG D as follows:

o Steam drum visual inspections to evaluate the material condition and cleanliness of key components such as moisture separators, drain systems, and interior surfaces.

o Drop down examinations (through the primary separators) of the upper tube bundle and AVB supports.

o Visual inspections of feed ring internal interface for flow accelerated corrosion o Visual inspections of upper tube support plate (TSP) to assess material conditions and cleanliness.

Serial No.18-116 Docket No. 50-423 Attachment 1, Page 3 of 13 The results of all secondary-side visual examinations performed were satisfactory, with no degradation detected.

b. Degradation mechanisms found, Degradation mechanisms found during 3R18 included AVB wear, TSP wear, volumetric indications from fabrication and volumetric degradation from foreign object wear.

c. Nondestructive examination techniques utilized for each degradation mechanism, Table 2 identifies the examination techniques used for evaluating degradation mechanisms applicable to the MPS3 SGs.

Table 2 Degradation Mechanisms and Inspection Techniques Degradation Classification Location Probe Type Mechanism Existing Tube Wear Anti-Vibration Bars Bobbin - Detection and Sizing Bobbin - Detection Existing Tube Wear Tube Support Plate

+Point' - Sizing Bobbin, Array and +Point' -

Tube Wear Existing Freespan and TIS Detection (foreign objects)

+Point' - Sizing Existing IGA/SCC Tube Ends N/A*

Feed Ring and J Tube to Feed Existing FAC Visual Inspection Ring Interface Bobbin - Detection Existing Tube Wear Flow Distribution Baffle

+Point'- Sizing ODSCC Hot Leg Top-of-Tubesheet Array - Detection Potential PWSCC And Sludge Region +Point'- Detection and Sizing Bulges, Dents, Manufacturing ODSCC Anomalies, and Above- Array - Detection Potential PWSCC Tubesheet Overexpansions +Point'- Detection and Sizing (OVR)

Tubesheet Array - Detection Potential PWSCC Overexpansions (OXP) +Point'- Detection and Sizing ODSCC Array - Detection Potential Row 1 and 2 U-bends PWSCC +Point' - Detection and Sizing Potential FAC Moisture Separators Visual Inspection Plug Installation Potential Plugs Visual Inspection Problems Potential Tube Slippage Within Tubesheet Bobbin Detection

• Inspection for this mechanism was not necessary under the existing alternate repair criteria.

Serial No.18-116 Docket No. 50-423 Attachment 1, Page 4 of 13

d. Location, orientation (if linear), and measured sizes (if available) of service induced indications, Tables 3 through 8 identify the AVB wear and non-AVB wear volumetric indications reported during 3R18.

Table 3 3R18 Volumetric Degradation Summary SG A (Excludes AVB Wear)

Foreign Max Plugged &

SG Row Col Location Cause Object Depth Stabilized?

Remaining SGA 2 17 05H -0.95 12 Tube Support Wear NA No SGA 3 112 06C -1.05 32 Foreign Object Wear NA No SGA 6 122 TSH +3.87 15 Foreign Object Wear No No SGA 7 3 TSC-0.04 25 Foreign Object Wear No No SGA 15 68 07C -0.98 31 Foreign Object Wear No No SGA 15 74 07(-0.76 37 Foreign Object Wear No No SGA 18 94 03H -0.09 9 Tube Support Wear NA No SGA 20 97 08C -1.02 21 Foreign Object Wear No No SGA 23 76 03C +0.11 17 Tube Support Wear NA No SGA 24 7 04H +3.51 24 Foreign Object Wear No No SGA 24 11 TSH +0.01 25 Foreign Object Wear No No SGA 28 112 OlH +0.3 36 Foreign Object Wear No No SGA 29 109 TSC-0.05 20 Foreign Object Wear No No 01H +0.31 14 Foreign Object Wear No No SGA 29 110 TSC+O 19 Foreign Object Wear No No SGA 35 71 08C -1.09 30 Foreign Object Wear No No SGA 36 76 01H +0.27 10 Tube Support Wear NA No SGA 43 103 TSC +0.6 17 Foreign Object Wear No No SGA 45 100 OlH -0.15 11 Tube Support Wear NA No OlC +0.74 28 Foreign Object Wear No No SGA 47 24 OlC +1.01 18 Foreign Object Wear No No OlC +0.78 24 Foreign Object Wear No No SGA 47 25 OlC +0.95 30 Foreign Object Wear No No SGA 58 47 TSC +0.45 19 Sled NA No SGA 58 55 08H -1.77 46 Foreign Object Wear No Yes SGA 58 76 TSC +0.39 18 Sled NA No SGA 59 60 08H -1.79 25 Foreign Object Wear No No

SerialNo.18-116 Docket No. 50-423 Attachment 1, Page 5 of 13 Table 4 3R18 Volumetric Degradation Summary SG C (Excludes AVB Wear)

Max Foreign Object Plugged &

SG Row Col Location Cause Depth Remaining Stabilized?

SGC 1 5 TSC +2.67 13 Foreign Object Wear No No SGC 1 73 TSC +19.43 15 Foreign Object Wear No No SGC 1 102 01C +4.46 17 Foreign Object Wear No No SGC 2 103 02(-6.86 16 Foreign Object Wear No No SGC 3 3 04C +16.08 9 Fabrication NA No SGC 8 61 TSH +0.38 25 Foreign Object Wear No No SGC 13 120 08C-0.8 29 Foreign Object Wear No No SGC 20 72 02H +5.43 21 Fabrication NA No SGC 35 78 08(-0.94 28 Foreign Object Wear No No SGC 35 110 06C -1.25 24 Foreign Object Wear No No TSC +0.29 19 Sled NA No TSC +0.46 15 Sled NA No SGC 36 13 TSC +0.46 19 Sled NA No TSC +0.46 16 Sled NA No SGC 36 51 08(-0.88 28 Foreign Object Wear No No SGC 36 75 08C -1.01 24 Foreign Object Wear No No SGC 38 15 TSC +0.46 19 Sled NA No SGC 44 102 TSC +0.47 16 Sled NA No SGC 46 34 TSH +0.28 17 Foreign Object Wear No No SGC 46 52 05C-0.46 15 Tube Support Wear NA No SGC 47 34 TSH +0.29 17 Foreign Object Wear No No SGC 47 61 06C -0.68 24 Foreign Object Wear No No SGC 48 25 TSH +0.36 16 Foreign Object Wear No No SGC 48 88 07(-0.81 27 Tube Support Wear NA No SGC 54 64 TSH +0.07 26 Foreign Object Wear No No SGC 55 68 TSH +0.53 21 Foreign Object Wear No No SGC 56 41 TSH +0.4 21 Foreign Object Wear No

• No SGC 56 65 06H +13.45 26 Foreign Object Wear No No SGC 56 69 TSH -0.05 27 Foreign Object Wear No No TSC +0.62 16 Sled NA No SGC 56 82 TSC +0.62 18 Sled NA No SGC 57 44 TSH +0.36 17 Sled NA No TSC +0.42 20 Sled NA No SGC 58 48 TSH +0.38 17 Sled NA No TSC +0.43 17 Sled NA No SGC 58 49 TSH +0.38 17 Sled NA No TSC +0.43 19 Sled NA No SGC 58 76 TSH +0.3 18 Sled NA No SGC 59 55 TSC +0.4 17 Sled NA No SGC 59 59 TSC +0.44 17 Foreign Object Wear No No SGC 59 68 TSH +0.45 18 Sled NA No

Serial No.18-116 Docket No. 50-423 Attachment 1, Page 6 of 13 Table 5 3R18 AVB Wear Listings, SG A- Repeat Indications SG Row Col Location %TW SG Row Col Location %TW SGA 12 121 AV6 10 SGA 34 41 AV4 12 SGA 21 118 AV6 10 SGA 34 44 AV3 8 SGA 22 78 AV1 13 SGA 34 46 AV3 20 SGA 22 78 AV5 17 SGA 34 46 AV4 17 SGA 22 78 AV6 14 SGA 34 46 AV5 30 SGA 24 116 AV6 14 SGA 34 46 AV6 34 SGA 26 44 AV2 15 SGA 34 48 AV1 18 SGA 26 44 AV5 18 SGA 34 48 AV2 19 SGA 26 115 AV1 26 SGA 34 48 AV3 28 SGA 27 8 AV1 11 SGA 34 73 AV3 16 SGA 27 8 AV6 8 SGA 34 73 AV4 31 SGA 27 9 AV3 12 SGA 34 73 AV5 35 SGA 27 115 AV1 18 SGA 34 73 AV6 13 SGA 28 36 AV5 13 SGA 34 85 AV5 17 SGA 28 113 AV5 10 SGA 34 91 AV2 12 SGA 28 115 AV1 33 SGA 34 91 AV4 12 SGA 29 40 AV2 11 SGA 34 97 AV3 11 SGA 29 67 AV1 12 SGA 34 98 AV4 15 SGA 29 67 AV2 17 SGA 34 107 AV4 8 SGA 29 67 AV5 12 SGA 34 109 AV4 25 SGA 29 79 AV5 14 SGA 35 49 AV2 10 SGA 29 114 AV2 13 SGA 35 49 AV5 16 SGA 29 114 AV5 10 SGA 35 59 AV2 30 SGA 30 9 AV5 31 SGA 35 59 AV3 14 SGA 30 10 AV5 15 SGA 35 59 AV4 14 SGA 30 11 AV5 10 SGA 35 59 AV6 19 SGA 30 40 AV2 12 SGA 35 60 AV4 30 SGA 30 113 AV5 22 SGA 35 60 AV5 27 SGA 30 113 AV6 12 SGA 35 60 AV6 13 SGA 30 114 AV1 11 SGA 35 61 AV2 15 SGA 31 61 AV5 13 SGA 35 61 AV4 15 SGA 31 109 AV2 11 SGA 35 65 AV2 14 SGA 32 111 AV4 20 SGA 35 65 AV3 13 SGA 32 111 AV5 19 SGA 35 65 AV4 18 SGA 33 111 AV6 10 SGA 35 65 AV5 17 SGA 34 15 AV6 13 SGA 35 71 AV3 12 SGA 34 29 AV3 11 SGA 35 71 AV4 25 SGA 34 29 AV6 13 SGA 35 71 AV5 12 SGA 34 41 AV3 18 SGA 35 71 AV6 11

SerialNo.18-116 Docket No. 50-423 Attachment 1, Page 7 of 13 SG Row Col Location %TW SG Row Col Location %TW SGA 35 77 AV1 9 SGA 38 106 AV3 18 SGA 35 77 AV2 13 SGA 38 106 AV4 16 SGA 35 77 AV3 19 SGA 38 106 AV5 16 SGA 35 77 AV4 15 SGA 39 51 AV3 16 SGA 35 77 AV5 10 SGA 39 51 AV4 14 SGA 35 80 AV3 9 SGA 39 57 AV1 16 SGA 35 90 AV2 11 SGA 39 57 AV2 32 SGA 35 100 AV3 8 SGA 39 57 AV3 23 SGA 35 108 AV2 10 SGA 39 57 AV4 25 SGA 35 108 AV3 10 SGA 39 57 AV5 12 SGA 35 108 AV6 10 SGA 39 60 AV4 26 SGA 37 34 AV1 12 SGA 39 62 AV5 14 SGA 37 45 AV2 35 SGA 39 62 AV6 13 SGA 37 45 AV3 24 SGA 39 70 AV2 8 SGA 37 45 AV4 19 SGA 39 70 AV3 14 SGA 37 45 AV5 18 SGA 39 70 AV4 11 SGA 37 56 AV3 14 SGA 39 71 AV2 9 SGA 37 56 AV4 20 SGA 39 71 AV4 17 SGA 37 69 AV5 22 SGA 39 71 AV5 20 SGA 37 69 AV6 25 SGA 39 71 AV6 15 SGA 37 72 AV3 17 SGA 39 74 AV3 10 SGA 37 89 AV3 9 SGA 39 75 AV3 13 SGA 37 90 AV3 25 SGA 39 75 AV4 11 SGA 37 90 AV4 15 SGA 39 75 AV5 15 SGA 37 90 AV5 16 SGA 39 75 AV6 16 SGA 37 91 AV3 20 SGA 39 78 AV3 11 SGA 37 91 AV4 15 SGA 40 45 AV3 16 SGA 37 91 AV5 27 SGA 40 45 AV4 31 SGA 37 91 AV6 21 SGA 40 45 AV5 17 SGA 37 92 AV5 17 SGA 40 51 AV4 30 SGA 37 99 AV3 15 SGA

• 40 51 AV5 40 SGA 37 100 AV3 14 SGA 40 58 AV2 17 SGA 37 100 AV4 12 SGA 40 58 AV3 18 SGA 37 100 AV5 12 SGA 40 58 AV5 17 SGA 37 102 AV4 11 SGA 40 64 AV4 17 SGA 37 106 AV4 15 SGA 40 67 AV2 11 SGA 37 106 AV5 12 SGA 40 67 AV3 11 SGA 38 52 AV2 18 SGA 40 71 AV2 19 SGA 38 52 AV3 26 SGA 40 71 AV3 22 SGA 38 79 AV6 11 SGA 40 71 AV4 26 SGA 38 86 AV5 13 SGA 40 86 AV2 12

Serial No.18-116 Docket No. 50-423 Attachment 1, Page 8 of 13 SG Row Col Location %TW SG Row Col Location %TW SGA 40 94 AV5 16 SGA 42 98 AV3 30 SGA 40 100 AV3 11 SGA 42 98 AV4 32 SGA 40 102 AV4 11 SGA 42 101 AV2 17 SGA 41 61 AV3 22 SGA 42 101 AV3 23 SGA 41 61 AV4 26 SGA 42 101 AV4 28 SGA 41 74 AV5 8 SGA 42 101 AV5 25 SGA 41 87 AV4 18 SGA 42 102 AV3 34 SGA 41 91 AV3 10 SGA 42 102 AV4 31 SGA 41 100 AV3 8 SGA 42 102 AV5 24 SGA 41 101 AV4 12 SGA 42 103 AV3 11 SGA 41 101 AV5 11 SGA 42 103 AV4 11 SGA 41 102 AV4 31 SGA 43 20 AV6 7 SGA 41 102 AV5 14 SGA 43 36 AV1 12 SGA 42 20 AV6 8 SGA 43 49 AV2 17 SGA 42 33 AV3 19 SGA 43 49 AV3 12 SGA 42 33 AV4 14 SGA 43 64 AV3 11 SGA 42 37 AV2 13 SGA 43 64 AV4 13 SGA 42 37 AV3 10 SGA 43 64 AV5 17 SGA 42 37 AV6 13 SGA 43 76 AV4 12 SGA 42 43 AV2 20 SGA 43 80 AV3 16 SGA 42 43 AV3 17 SGA 43 80 AV4 18 SGA 42 53 AV2 12 SGA 43 80 AV5 11 SGA 42 53 AV3 17 SGA 43 80 AV6 16 SGA 42 53 AV4 24 SGA 43 85 AV3 7 SGA 42 53 AV5 31 SGA 43 87 AV2 19 SGA 42 63 AV2 10 SGA 43 87 AV4 23 SGA 42 63 AV3 23 SGA 43 87 AV5 23 SGA 42 63 AV4 16 SGA 43 95 AV6 9 SGA 42 63 AV5 14 SGA 43 96 AV5 9 SGA 42 77 AV2 7 SGA 43 98 AV4 16 SGA 42 77 AV3 11 SGA 43 98 AV5 14 SGA 42 77 AV4 24 SGA 43 99 AV4 19 SGA 42 80 AV4 9 SGA 43 101 AV3 10 SGA 42 85 AV2 11 SGA 43 101 AV4 19 SGA 42 85 AV4 12 SGA 43 101 AV5 17 SGA 42 86 AV3 9 SGA 43 102 AV4 21 SGA 42 86 AV4 13 SGA 43 102 AV5 20 SGA 42 93 AV3 13 SGA 43 103 AV5 11 SGA 42 93 AV4 19 SGA 44 64 AV2 29 SGA 42 93 AV5 22 SGA 44 64 AV3 19 SGA 42 98 AV1 9 SGA 44 74 AV4 20

Serial No.18-116 Docket No. 50-423 Attachment 1, Page 9 of 13 SG Row Col Location, %TW SG Row Col Location %TW SGA 44 74 AV5 27 SGA 50 50 AV4 18 SGA 44 74 AV6 21 SGA 50 76 AV2 23 SGA 44 75 AV3 16 SGA 50 76 AV3 18 SGA 44 96 AV2 12 SGA 50 76 AV4 18 SGA 44 96 AV4 14 SGA 50 82 AV2 16 SGA 44 96 AV5 10 SGA 50 82 AV3 24 SGA 44 98 AV1 14 SGA 50 82 AV4 21 SGA 44 98 AV2 23 SGA 50 86 AV2 13 SGA 44 98 AV4 17 SGA 50 87 AV2 27 SGA 45 45 AV3 10 SGA 50 87 AV3 18 SGA 45 71 AV2 16 SGA 50 87 AV4 12 SGA 45 96 AV5 10 SGA 50 87 AV5 12 SGA 45 98 AV4 19 SGA 51 31 AV2 14 SGA 45 98 AV5 10 SGA 51 64 AV3 15 SGA 45 98 AV6 14 SGA 51 64 AV4 7 SGA 45 99 AV4 17 SGA 51 65 AV3 15 SGA 45 99 AV5 13 SGA 51 65 AV4 14 SGA 45 101 AV6 9 SGA 51 65 AV5 19 SGA 46 97 AV5 11 SGA 51 66 AV2 10 SGA 46 98 AV5 8 SGA 51 66 AV3 10 SGA 46 99 AV2 12 SGA 51 79 AV3 11 SGA 46 99 AV4 15 SGA 52 66 AV4 27 SGA 46 99 AV5 19 SGA 52 90 AV3 14 SGA 47 85 AV1 10 SGA 52 90 AV4 14 SGA 47 98 AV3 19 SGA 53 81 AV1 12 SGA 47 99 AV6 16 SGA 53 81 AV3 26 SGA 48 25 AV3 9 SGA 53 81 AV5 9 SGA 48 26 AV2 10 SGA 54 35 AV4 16 SGA 48 26 AV6 11 SGA 54 35 AV5 23 SGA 48 96 AV6 12 SGA 54 49 AV2 16 SGA 49 95 AV2 14 SGA 54 49 AV3 12 SGA 49 95 AV4 12 SGA 56 41 AV2 14 SGA 50 29 AV4 11 SGA 58 54 AV1 12 SGA 50 29 AV5 13 SGA 59 64 AV6 12 SGA 50 44 AV3 12 SGA 50 44 AV4 19 SGA 50 44 AV5 34 SGA 50 44 AV6 13

Serial No.18-116 Docket No. 50-423 Attachment 1, Page 10 of 13 Table 6 3R18 AVB Wear Listings, SG A - New Indications SG Row Col Location %TW SGA 18 72 AV1 11 SGA 34 73 AV1 12 SGA 34 73 AV2 10 SGA 34 91 AV3 11 SGA 35 59 AV5 12 SGA 35 60 AV3 14 SGA 35 90 AV3 15 SGA 35 108 AV4 10 SGA 37 90 AV2 12 SGA 37 102 AV5 10 SGA 37 106 AV3 10 SGA 38 52 AV4 19 SGA 39 60 AV5 13 SGA 39 71 AV3 11 SGA 40 51 AV2 19 SGA 40 84 AV6 12 SGA 41 72 AV2 16 SGA 41 72 AV3 14 SGA 41 74 AV4 13 SGA 41 95 AV3 10 SGA 41 104 AV6 12 SGA 41 105 AV6 13 SGA 42 53 AV6 16 SGA 43 89 AV3 12 SGA 43 99 AV5 11 SGA 45 68 AV1 11 SGA 45 71 AV1 13 SGA 46 99 AV6 10 SGA 47 71 AV2 11 SGA 51 65 AV1 16 SGA 51 65 AV2 19 SGA 51 65 AV6 14 SGA 52 90 AV2 14 SGA 54 35 AV6 19 SGA 58 73 AV6 11

Serial No.18-116 Docket No. 50-423 Attachment 1, Page 11 of 13 Table 7 3R18 AVB Wear Listings, SG C - Repeat Indications SG Row Col Location %TW SG Row Col Location %TW SGC 15 66 AV1 14 SGC 42 20 AV4 21 SGC 25 8 AV1 8 SGC 42 20 AV5 23 SGC 25 116 AV6 17 SGC 42 20 AV6 15 SGC 34 14 AV2 9 SGC 42 23 AV3 16 SGC 34 14 AV5 11 SGC 42 23 AV4 28 SGC 36 15 AV5 12 SGC 42 23 AV5 26 SGC 36 15 AV6 12 SGC 42 103 AV3 10 SGC 37 15 AV2 17 SGC 45 57 AV2 13 SGC 37 15 AV3 11 SGC 45 100 AV5 7 SGC 37 15 AV4 10 SGC 45 100 AV6 10 SGC 37 15 AV5 25 SGC 46 33 AV6 10 SGC 37 15 AV6 14 SGC 46 97 AV1 10 SGC 37 88 AV3 10 SGC 46 97 AV3 10 SGC 38 65 AV6 10 SGC 47 99 AV6 13 SGC 39 17 AV2 14 SGC 48 26 AV4 10 SGC 39 17 AV3 11 SGC 48 98 AV3 12 SGC 39 17 AV4 16 SGC 48 98 AV4 9 SGC 39 17 AV5 18 SGC 48 98 AV6 11 SGC 39 17 AV6 14 SGC 49 96 AV5 25 SGC 39 79 AV3 13 SGC 49 96 AV6 27 SGC 39 107 AV6 10 SGC 50 28 AV2 11 SGC 41 42 AV3 23 SGC 50 28 AV5 19 SGC 41 54 AV1 13 SGC 50 93 AV5 12 SGC 41 54 AV3 21 SGC 50 93 AV6 27 SGC 41 54 AV4 19 SGC 50 95 AV6 11 SGC 41 54 AV5 26 SGC 51 92 AV6 11 SGC 41 62 AV2 22 SGC 54 35 AV5 13 SGC 41 62 AV3 19 SGC 54 36 AV4 17 SGC 41 62 AV3 27 SGC 54 36 AV5 9 SGC 41 62 AV4 21 SGC 54 85 AV6 13 SGC 41 62 AV4 29 SGC 54 86 AV1 9 SGC 41 62 AV5 31 SGC 56 41 AV2 11 SGC 41 62 AV6 13 SGC 56 41 AV4 17 SGC 41 65 AV4 15 SGC 56 41 AV5 25 SGC 41 65 AV5 17 SGC 56 41 AV6 15 SGC 41 105 AV6 11 SGC 56 44 AV4 7 SGC 42 20 AV2 12 SGC 57 69 AV1 13 SGC 42 20 AV3 20 SGC 58 49 AV5 10

Serial No.18-116 Docket No. 50-423 Attachment 1, Page 12 of 13 Table 8 3R18 AVB Wear Listings, SG C- New lndicatio ns SG Row Col Location %TW SGC 25 115 AV1 15 SGC 27 44 AV2 12 SGC 41 42 AV4 14

e. Number of tubes plugged during the inspection ou tage for each degradation mechanism, Based on inspection results, two tubes were plugged during 3R18 as shown in Table 9 below.

Table 9 Tubes Plugged During 3R18 SG Row *col f{ea,son Hot Leg Cold.Leg SGA 40 51 40% TW Wear @AV5 Rolled Plug/L ong Stabilizer Rolled Plug SGA 58 55 46% TW Foreign Object Wear Rolled Plug Rolled Plug

f. The number and percentage of tubes plugged to date and the effective plugging percentage in each steam generator.

Table 10 provides the total number of tubes plugged to date and the effective plugging percentage in each SG.

Table 10 Number Tubes Plugged To Date SGA SG B sGC SG D Prior to 3R18 49 25 22 91 During 3R18 2 0 0 0 Total After 3R18 51 25 22 91 Percentage 0.906 0.444 0. 391 1.617 Overall Percentage 0.84 Since no sleeving has been performed in the MPS3 stea m generators, the effective plugging percentage is the same as the actual plugging percen tage.

g. The results of condition monitoring, including the resu Its of tube pulls and in-situ

testing, No tubes were pulled and no in-situ pressure tests were performed. The condition monitoring assessment concluded that the structural integri ty, operational leakage, and

Serial No.18-116 Docket No. 50-423 Attachment 1, Page 13 of 13 accident induced leakage performance criteria were not exceeded during the operating interval prec~ding 3R18.

h. The primary to secondary LEAKAGE rate observed in each SG (if it is not practical to assign the LEAKAGE to an individual SG, the entire primary to secondary LEAKAGE should be conservatively assumed to be from one SG) during the cycle preceding the inspection which is the subject of the report, No primary to secondary SG leakage was reported during Cycle 18.

i. The calculated accident induced 'leakage rate from the portion of the tubes below 15.2 inches from the top of the tubesheet for the most limiting accident in the most limiting SG. In addition, if the calculated accident induced leakage rate from the most limiting accident is less than 2.49 times the maximum operational primary to secondary leakage rate, the report should describe how it was determined; For the purposes of the condition monitoring assessment, and in accordance with the permanent alternate repair criteria, the accident leakage attributed to degradation within the tubesheet below the H* dimension must be estimated by applying a factor of 2.49 to the operational leakage. There was no recordable operational leakage during Cycle 18; hence, the leakage from this degradation during a limiting accident would have been zero (i.e., 2.49 X 0).

j. The results of monitoring for tube axial displacement (slippage). If slippage is discovered, the implications of the discovery and corrective action shall be provided.

Tube slippage monitoring was performed on SG A and SG C using the bobbin coil data during 3R18. There was no detection of slippage during the 3R18 examination.

Serial No.18-116 Docket No. 50-423 Attachment 2 Acronyms MILLSTONE POWER STATION UNIT 3 DOMINION ENERGY NUCLEAR CONNECTICUT, INC. (DNC)

Serial No.18-116 Docket No. 50-423 Attachment 2, Page 1 of 1 Acronyms AVB Anti-Vibration Bar OVR Above Tubesheet Over Expansion BET Bottom of the Expansion Transition OXP Over Expansion BLG Bulge PIO Positive Identification C Column PLG Tube is plugged CL Cold Leg PLP Possible Loose Part DOH Ding or Dent Signal - Reviewed in PTE Partial Tubesheet Expansion History PWR Pressurized Water Reactor DOI Distorted Dent or Ding Indication PWSCC Primary Water Stress Corrosion DDS Ding or Dent Signal - Non- Cracking Confirming w/RPC R Row ONG Ding RAD Retest Analyst Discretion ONT Dent Indication RBD Retest - Bad Data ECT Eddy Current Test RIC Retest - Incomplete EFPY Effective Full Power Years RRT Retest - Restricted Tube EPRI Electric Power Research Institute S/N Signal-to-Noise Ratio ETSS Examination Technique SAi Single Axial Indication Specification Sheet sec Stress Corrosion Cracking F/L Full Length SCI Single Circumferential Indication FAC Flow Accelerated Corrosion SG Steam Generator FOB Flow Distribution Baffle SLG Sludge FO Foreign Object SSI Secondary Side Inspection FOTS Foreign Object Tracking System SVI Single Volumetric Indication HL Hot Leg TEC Tube End Cold Leg IGA lntergranular Attack TEH Tube End Hot Leg INF Indication Not Found TFH Tangential Flaw-Like Signal - Reviewed INR Indication Not Reportable in History LPI Loose Part Indication TFS Tangential Flaw-Like Signal - Non-LPR Loose Part Removed Confirming w/RPC LPS Loose Part Signal TSC Top of Tubesheet Cold Leg MRPC Motorized Rotating Pancake Coil TSH Top of Tubesheet Hot Leg NOD No Detectable Degradation TSP Tube Support Plate NOE Nondestructive Examination TTS Top of Tubesheet NDF No Degradation Found TWO Through-Wall Depth NEI Nuclear Energy Institute %TW Percent Through-Wall NQH Non-quantifiable Indication - VOL Volumetric Indication Reviewed in History NQI Non-quantifiable Indication OA Operational Assessment ODSCC Outer Diameter Stress Corrosion Cracking