DCL-05-096, Reply to Request for Additional Information for Special Report 05-01 - Results of Steam Generator Tube Inspections for Diablo Canyon Power Unit 2 Twelfth Refueling Outage

Reply to Request for Additional Information for Special Report 05-01 - Results of Steam Generator Tube Inspections for Diablo Canyon Power Unit 2 Twelfth Refueling Outage

ML052440285
Person / Time
Site:	Diablo Canyon
Issue date:	08/25/2005
From:	Jacobs D Pacific Gas & Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
DCL-05-096, OL-DPR-82
Download: ML052440285 (4)

Text

I Pacific Gas and ElectricCompanye Donna Jacobs Diablo Canyon Power Plant Vice President P.0. Box 56 Nuclear Services Avila Beach, CA 93424 805.545.4600 August 25, 2005 Fax: 805.545.4234 PG&E Letter DCL-05-096 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Docket No. 50-323, OL-DPR-82 Diablo Canyon Unit 2 Reply to Request for Additional Information for Special Report 05 Results of Steam Generator Tube Inspections for Diablo Canyon Power Plant Unit 2 Twelfth Refueling Outage

Dear Commissioners and Staff:

By Pacific Gas and Electric (PG&E) Letters DCL 04-165, "Special Report 04-02:

Steam Generator Tube Plugging During Unit 2 Twelfth Refueling Outage," dated November 30, 2004 (ML043430465), and DCL-05-024, "Special Report 05 Results of Steam Generator (SG) Tube Inspection for Diablo Canyon Power Plant Unit 2 Twelfth Refueling Outage," dated March 16, 2005 (ML050820052), PG&E submitted reports summarizing the SG tube inspections performed at Diablo Canyon Unit 2 during the twelfth refueling outage (2R12).

On July 5, 2005, the NRC requested additional information needed for the staff to complete its review of these submittals. PG&E's response to the request for additional information is provided in the enclosure. If you have any questions or require additional information, please contact John Arhar at (805) 545-4629.

Sincerely, 2

ddml/469 Enclosure cc: Terry W. Jackson Bruce S. Mallett Diablo Distribution cc/enc: Girija S. Shukla State of California, Pressure Vessel Unit AOof

PG&E Letter DCL-05-096 Enclosure Reply to Request for Additional Information for Special Report 05 Results of Steam Generator (SG) Tube Inspections for Diablo Canjon Power Plant Unit 2 Twelfth Refueling Outage NRC Request By letters dated November 30, 2004 (ML043430465), and March 16, 2005 (ML050820052), Pacific Gas and Electric Company, the licensee for Diablo Canyon Unit 2, submitted reports summarizing the steam generator (SG) tube inspections performed at Diablo Canyon Unit 2 during their 2004 refueling outage (2R12).

Additional information concerning the 2004 SG tube inspections at Diablo Canyon Unit 2 was summarized by the NRC staff in a letter dated January 4, 2005 (ML043570323).

In order for the staff to complete its review of the licensee's submittals, responses to the following questions are requested:

NRC Request 1:

In Table 3-4 of Enclosure 3 to your March 16, 2005 letter, the voltage change per effective fullpoweryear (EFPY) is provided. The largest growth rates were reported as 1.434 and 1.020 volts per EFPY. These values do not match those listed in Table 3-5 where the maximum voltage change per EFPY was listed as 1.35. Please clarify this apparent discrepancy. If any calculations were performed using incorrect growth values, please correct these calculations and provide the results to the NRC.

PG&E Response 1:

Table 3-5 was prepared using an incorrect cycle length of 1.61 EFPY when calculating the growth rates. The correct cycle length is 1.52 EFPY. Enclosed is a revised Table 3-5 with corrected growth rates. Other than Table 3-5, no calculations were performed using incorrect growth values.

NRC Request 2:

• Figure 3-45 of Enclosure 3 to your March 16, 2005 letter illustrates preventive plugging performed to limit the possibility of extreme voltage changes during a cycle. Six tubes in steam generator 4were preventively plugged since the

+PointTm amplitude exceeded 1.4 volts. Please discuss why one tube in steam generator 4 with a bobbin voltage of approximately 1.9 volts and a

+PointU' amplitude of approximately 1.8 volts was not preventively plugged.

I

PG&E Letter DCL-05-096 Enclosure PG&E Response 2:

On Figure 3-45, the tube in steam generator 4 with a bobbin voltage of approximately 1.9 volts and a +PointTm amplitude of approximately 1.8 volts was plugged due to its location in the wedge region exclusion zone, so this tube was not categorized as being preventively plugged. Page 11 of the report states that "a seventh indication in SG 2-4 in this category was already required to be plugged due to its location in the wedge exclusion region."

NRC Request 3:

Figure 3-42 of Enclosure 3 to your March 16, 2005 letter indicates that there were 7 indications greater than 2 volts in steam generator 1. However, Table 3-3 indicates that there were only 5 indications that had voltages greaterthan 2 volts in steam generator 1. Similarly, Figure 3-45 indicates that there were 7 indicationsgreaterthan 2 volts in steam generator4 while Table 3-3 indicates that there were only 4 indicationsthat had voltages greaterthan 2 volts in this steam generator. Please clarify this apparent discrepancy.

PG&E Response 3:

The data is correct in Table 3-3 and in Figures 3-42 to 3-45. Figures 3-42 to 3-45 plot all +PointTM single axial indication (SAl) voltages against the corresponding bobbin distorted outside diameter signal (DOS) voltage. Outside diameter stress corrosion cracking (ODSCC) indications may have multiple SAls. In SG 2-1 R25C42 1H bobbin indication of 2.1 volts; there are 3 SAls. Therefore, Figure 3-42 shows seven SAls associated with five greater than 2 volt DOS indications. In SG 2-4 R27C43 2H bobbin indication of 2.43 volts, there are 3 SAls. In SG 2-4 R33C50 2H bobbin indication of 2.62 volts, there are 3 SAIs. Therefore, Figure 3-45 shows eight SAls associated with four greater than 2 volt DOS indications. Two of the Figure 3-45 SAI voltages are very close together (0.01 -volts apart), so the points are indistinguishable in the figure.

2

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PG&E Letter DCL-05-096 Enclosure Revised Table 3-5 DOS/AONDB Voltage and Growth Distribution by TSP T SG 2-1 SG2-2 Tube Tube Support No. of Max Average Max Average Support No so Max Average Max Average Plae ndcaios olag Vltge Growth! Growth! Plate Indications Voltage Voltage Growth EFPYth Paendatos Vlae Vlae EFPY EFPY EFProth Growth 1H 294 2.14 0.59 0.95 0.12 1H 138 1.96 0.59 0.59 0.11 2H1 102 2.38 0.53 1.02 0.11 2H 156 2.03 0.57 0.78 0.09 3H1 31 1.84 0.53 0.83 0.09 3H 58 1.79 0.50 0.61 0.07 4H 5 0.89 0.50 0.36 0.14 4H 18 1.16 0.50 0.15 0.03 5H 18 0.93 0.51 0.17 0.01 5H 3 0.98 0.57 0.34 0.14 6H 3 0.90 0.65 0.39 0.13 6 1 0.35 0.35 0.09 0.09 7H _H 0.51 0.51 0.17 0.08 CL 19 0.91 0.47 0.07 0.01 CL 21 0.83 0.40 0.24 0.03 AllInds 472 2.38 0.57 1.02 0.11 All Inds 397 2.03 0.55 0.78 0.09 Tube Support No. of Max I

SG 2-3 Average Max

- l 1

Tube IAverage ISupport il No. of J -

Max T

SG 2-4 fAverage*

M Max Average Plate Indications Voltage Voltagel Growth/ Growth Plate Indications Voltagel VoltagelGrowth Growth/

1Hl 148 1.60 0.53 0.36 0.05 1H 371 1.99 0.66 0.63 0.12 2H1 83 1.49 0.55 0.57 0.07 2H1 436 2.87 0.76 1.43 0.16 3H1 23 1.18 0.46 0.16 0.03 3H 148 1.92 0.57 070 0.11 4H1 1 0.30 0.30 l 0.01 -001 4H1 47 1.19 0151 0.36 0.11 5H1 4 0.86 .0.44 0.15 0.03 5H1 7 0.71 0.39 0.13 0.05 6H 2 0.32 0.30 0705 0.03 6H1 1 0.20 0.20 -0.03 -0.03 711 1 0.21102 0.04 0.04 7H11_ r _ _

CL 10 0.42 0.30 0.09 0.00 'CL 10 1 0.75 1 0.39 1 0.20 0.04 272 1.60 0.57 0.05 All Inds l 1 0_14 II Comoosite of All Four SGs T Tube Support Max Average No. of Max Average Growth/

Plate I Growth/

Indications I Voltage Voltage EFPY EFPY EFPY EFlPY 1Hl 951 2.14 0.61 0.95 0.11 2H1 777 2.87 0.67 1.43 0.13 3H1 260 1.92 0.54 0.83 0.09 4H 71 1.19 0.51 0.36 0.09 5H 32 0.98 0.48 0.34 0.03 6H1 7 0.90 0.44 0.39 0.07 7H 3 0.51 0.41 0.17 0.07 CL 60 0.91 0.40 0.24 0.02 AlInds 2161 2.87 0.61 1.43 0.11 3