ML081290185

Cycle 15 (U1C15) - 180-Day - Steam Generator (SG) Inspection Report

ML081290185
Person / Time
Site:	Sequoyah
Issue date:	04/23/2008
From:	Smith J D Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML081290185 (8)

Text

U.S. Nuclear Regulatory Commission Page 2 April 23, 2008

cc (Enclosure):

Mr. Thomas H. Boyce, Senior Project Manager

U.S. Nuclear Regulatory Commission

Mail Stop 08G-9a

One White Flint North

11555 Rockville Pike

Rockville, Maryland 20852-2739

SQN Unit 1 Cycle 15 180-Day Report In accordance with Technical Specification 6.8.4.k, Steam Generator Program and Technical

Specification 6.9.1.16, "Steam Generator Tube Inspection Report," this report documents the results of the Unit 1 Cycle 15 (U1C15) steam generator (SG) tube inservice inspection. The

following list is the required scope of the 180-day report.

1. The scope of inspections performed on each SG.

EDDY CURRENT EXAM TYPE (Exams) RSG 1 RSG 2 RSG 3 RSG 4 TotalFull Length Bobbin (.610 coil) 247724812479 24809917Full Length Bobbin (.590 coil) 424242 42168 Partial Length Bobbin (.570 coil HTE-VS3) 123122123 123491 Expansion Full Length Bobbin (.610 coil) 479286116 0881 Predetermined Diagnostic Plus Point 2329 135 Diagnostic/PID Plus Point 011 13

______________________

__________________ ____________Total Exams Completed 312329352790 264711495

Total Tubes Examined 312129332775 264511474 In accordance with the U1C15 Degradation Assessment, expansion sample examinations were performed in SGs 1, 2, and 3. No expansion sample was required in SG 4.

2. Active Degradation Mechanisms found.

INDICATIONS (Tubes) RSG 1 RSG 2 RSG 3 RSG 4 Total U-Bend Support Wear 32211 247

______________________

__________________ ____________Total 32211 247

3. Nondestructive examination technique utilized for each degradation mechanism.

Bobbin coil examinations were utilized for the detection of U-bend Support Wear.

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

Refer to Table 1

SQN Unit 1 Cycle 15 180-Day Report

5. Number of tubes plugged during the inspection outage for each active degradation mechanism.

PLUGGING STATUS RSG 1 RSG 2 RSG 3 RSG 4 TOTALPreviously Plugged Tubes 14665 31 Tubes Plugged by Damage Mechanism U-Bend Support Wear 0000 0 Total Plugged Cycle 15 0 0 0 0 0 Total Tubes Plugged 14 6 6 5 31 Plugged Tube Percentage 0.28%0.12%0.12%0.10% 0.16%

6. Total number and percentage of tubes plugged to date.

Refer to the response to Number 5 above. The U-bend Support Wear indications

were tapered along the tube axially.

7. The results of condition monitoring, including the results of tubes pulls and in-situ testing.

No tube pulls or in-situ pressure tests were performed.

U-BEND SUPPORT WEAR Structural Integrity The SQN U1C15 degradation assessment predicted, based on past indications and growth rate data, that 25 tubes could be preventively plugged. A total of 51

indications in 47 tubes were detected. None exceeded the plugging limit of 40

percent. The U-bend Support Wear was assumed to have grown from 0 percent

through wall over the last 2 fuel cycles. Using these growth rates, a repair limit of 30

percent was calculated which would ensure that a safety factor of 3 would be

maintained (with a 95 percent probability) until the next planned inspection during the

U1C18 refueling outage. Condition monitoring assumed the axial length of the U-

bend Support Wear indication to be the width of the U-bend Support (i.e., 2 inches).

All indications were a fraction of this length. The limiting indications were 16 percent

maximum depth. The limiting tubes were in SG1, Row 76, Col 100 at VS2-0.97, Row

85, Col 67 at VS4+0.91, and Row 87, Col 73 at VS2+1.28. The EPRI, "Steam

Generator Degradation Specific Management Flaw Handbook," Section 5.3.3, "Axial

Thinning with Limited Circumferential Extent," equations were utilized to calculate the

burst pressure. The calculated 95th percentile lower limit burst pressure was 6958

psig (3P is 4114 psig).

The largest amplitude U-bend Support Wear indication was 0.58 volts, and therefore did not exceed the in-situ pressure testing leakage screening criteria of 7.9 volts. All U-bend Support Wear indications met condition

monitoring performance criteria. Zero indications exceeded the 40 percent plugging

limit and zero indications exceeded the 30 percent repair limit.

SQN Unit 1 Cycle 15 180-Day Report Leakage Integrity During the previous two fuel cycles, the Unit 1 operational primary to secondary leakage was below detection. The majority of the indications detected during U1C15

were less than 0.5 volts which in accordance with EPRI Steam Generator In-Situ

Pressure Test Guidelines Revision 2 (TR-1007904), dated August 2003, Section

B.3.4 is a quick screen for structural and leakage integrity, and therefore provides a

95 percent probability that none of the indications would leak should a postulated

main steam line break have occurred. The greatest through wall was 16 percent.

The associated 95th percentile lower limit burst pressure was 6958 psig. The

equations utilized for burst pressure determine the ligament tearing pressure or the

pressure at which a partial through-wall indication goes through-wall (i.e., pop-

through). If an indication has a 95 percent probability of not going through wall at

6958 psig, then it should not go through wall at the Main Steam Line Break pressure

of 2405 psig. This provides additional confidence that no leakage would occur

should a postulated main steam line break occur.

8. The effective plugging percentage of all plugging in each SG.

Refer to the response to Number 5 above.

SQN Unit 1 Cycle 15 180 Day Report Table 1 List of Indications 1 The indications below were characterized as U-bend Support Wear. They were detected by bobbin coil. The associated maximum depth and voltage are included. The

plugging limit at SQN Unit 1 is 40 percent through wall (TW).

SG ROW COL LOCATION %TW VOLTS CHARACTERIZATION RESOLUTION 1 68 76 VS2-.26 7 0.21 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 75 73 VS3+.80 9 0.28 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 78 78 VS2+.91 8 0.23 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 83 77 VS2+.91 10 0.32 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 87 73 VS2+1.28 16 0.58 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 87 73 VS3+1.00 15 0.51 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 87 75 VS2+1.14 13 0.4 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 87 81 VS4-1.11 15 0.53 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 88 70 VS4-1.11 13 0.39 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 90 70 VS4-1.00 13 0.37 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 92 70 VS2-.91 9 0.24 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 92 70 VS4+1.00 15 0.45 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 95 77 VS4-1.11 9 0.27 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 96 76 VS3+1.28 11 0.35 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 55 115 VS3-.91 15 0.47 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 61 85 VS2-1.09 8 0.21 U-BEND SUPPORT WEAR In service <30% Repair Limit 3 67 87 VS3-.92 6 0.19 U-BEND SUPPORT WEAR In service <30% Repair Limit 3 76 90 VS2+.86 9 0.26 U-BEND SUPPORT WEAR In service <30% Repair Limit 4 68 64 VS3-.83 10 0.37 U-BEND SUPPORT WEAR In service <30% Repair Limit 4 97 55 VS4-.83 8 0.29 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 69 59 VS3+.77 10 0.31 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 70 66 VS4-1.03 15 0.53 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 74 48 VS3-.88 6 0.17 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 83 45 VS4-.91 6 0.15 U-BEND SUPPORT WEAR In service <30% Repair Limit 2 20 80 VS3-.06 14 0.45 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 83 49 VS2+.77 7 0.2 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 84 64 VS4+1.03 11 0.31 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 85 65 VS4+.80 11 0.33 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 85 67 VS4+.91 16 0.54 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 88 52 VS4-.91 8 0.22 U-BEND SUPPORT WEAR In service <30% Repair SQN Unit 1 Cycle 15 180 Day Report Table 1 List of Indications SG ROW COL LOCATION %TW VOLTS CHARACTERIZATION RESOLUTION Limit 1 92 52 VS3+.83 6 0.17 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 92 68 VS4+.62 14 0.41 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 93 65 VS2+.85 9 0.25 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 95 63 VS3-.63 13 0.42 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 95 63 VS4-1.14 11 0.33 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 98 66 VS3+.82 8 0.24 U-BEND SUPPORT WEAR In service <30% Repair Limit 2 92 42 VS2-.74 8 0.23 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 62 112 VS3+.77 13 0.41 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 66 110 VS3+.80 11 0.34 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 76 100 VS2-.97 16 0.56 U-BEND SUPPORT WEAR In service <30% Repair Limit 1 92 88 VS4-.85 11 0.33 U-BEND SUPPORT WEAR In service <30% Repair Limit 3 73 75 VS3+.74 7 0.23 U-BEND SUPPORT WEAR In service <30% Repair Limit 3 79 79 VS2-.86 7 0.23 U-BEND SUPPORT WEAR In service <30% Repair Limit 3 79 79 VS3+.86 8 0.27 U-BEND SUPPORT WEAR In service <30% Repair Limit 3 80 72 VS4-.83 9 0.31 U-BEND SUPPORT WEAR In service <30% Repair Limit 3 85 69 VS4+.83 10 0.35 U-BEND SUPPORT WEAR In service <30% Repair Limit 3 87 63 VS2+1.07 9 0.28 U-BEND SUPPORT WEAR In service <30% Repair Limit 3 87 65 VS3+.95 12 0.4 U-BEND SUPPORT WEAR In service <30% Repair Limit 3 89 71 VS4+1.01 8 0.26 U-BEND SUPPORT WEAR In service <30% Repair Limit 3 97 71 VS3+.74 8 0.26 U-BEND SUPPORT WEAR In service <30% Repair Limit 3 98 56 VS4-1.06 12 0.39 U-BEND SUPPORT WEAR In service <30% Repair Limit