ML11161A156
| ML11161A156 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/09/2011 |
| From: | St.Onge R Southern California Edison Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML11161A156 (6) | |
Text
SOUTHERN CALIFORNIA An EDISON INTERNATIONAL0 Company Richard I. St. Onge Director Nuclear Regulatory Affairs 1 OCFR50.55a June 9, 2011 ATTN: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Docket Nos. 50-361 and 50-362 Third Ten-Year Inservice Inspection (ISI) Interval 10CFR50.55a Requests ISI-3-32, ISI-3-33, and ISI-3-34 San Onofre Nuclear Generating Station, Units 2 and 3
References:
Letter from R. St Onge (SCE) to the U.S. Nuclear Regulatory Commission (NRC) dated January 7, 2011;
Subject:
Docket Nos.
50-361 and 50-362, Third Ten-Year Inservice Inspection (ISI)
Interval, 10CFR50.55a Relief Requests ISI-3-32, ISI-3-33, and ISI-3-34, San Onofre Nuclear Generating Station, Units 2 and 3.
Dear Sir or Madam,
By letter dated January 7, 2011 (Reference) Southern California Edison submitted Third Ten-Year Inservice Inspection (ISI) Interval Relief Requests ISI-3-32, ISI-3-33, in accordance with 10 CFR 50.55a(a)(3)(i), and ISI-3-34 in accordance with 10 CFR 50.55a(a)(3)(ii). The purpose of the referenced relief requests is to allow use of alternatives to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), Section Xl inservice inspection (ISI) requirements regarding examination of certain reactor pressure vessel welds for San Onofre Nuclear Generating Station (SONGS), Unit 2 and Unit 3.
By e-mail dated May 3, 2011, the NRC requested additional information in support of review of Relief Requests ISI-3-32, ISI-3-33, and ISI-3-34. Responses to the NRC request for additional information are provided in the Enclosure to this letter.
This letter and the enclosure contain no new commitments.
P\\O007?
P.O. Box 128 San Clemente, CA 92674
Document Control Desk June 9, 2011 Should you have any questions, please contact Ms. Linda T. Conklin at (949) 368-9443.
Sincerely,
Enclosure:
as stated cc:
E. E. Collins, Regional Administrator, NRC Region IV R. Hall, NRC Project Manager, San Onofre Units 2 and 3 G. G. Warnick, NRC Senior Resident Inspector, San Onofre Units 2 and 3
Enclosure Response to Request for Additional Information Regarding 10 CFR 50.55a Relief Requests ISI-3-32, ISI-3-33, ISI-3-34 Third Ten-Year Inservice Inspection (ISI) Interval
RESPONSES TO NRC RAIs REGARDING SCE RELIEF REQUESTS ISI-3-32, ISI-3-33, and ISI-3-34 Third Ten-Year Inservice Inspection (ISI) Interval The NRC staff provided questions regarding SCE's proposed Third Ten-Year Inservice Inspection Interval Relief Requests ISI-3-32, ISI-3-33, and ISI-3-34 by e-mail dated May 3, 2011.
NRC RAI 1:
Regarding the details of the through-wall cracking frequency (TWCF) calculation at SONGS Unit 3, as documented in Table 3 of Proposed Alternative, Enclosure 2, please verify what Chemistry Factor (CF) should be used for the limiting material, region no. 8, intermediate-shell plate, heat no. C-6802-1. If the CF changes for region no. 8, please provide updated outputs in Table 3.
SCE Response:
The CF that should be used for the limiting material, region no. 8, intermediate-shell plate, heat no. C-6802-1 is 72 0F. This value was calculated using credible surveillance data per Regulatory Guide 1.99, Position 2.1. This value was used to calculate adjusted reference temperatures for SONGS Unit 3 in WCAP-16167, Rev. 02. In Table 3 of the SONGS Unit 3 relief request, the Regulatory Guide 1.99 Position was incorrectly written as 1.1. The correct Regulatory Guide 1.99 Position is 2.1 for material no. 8. The CF for this material is not changing; therefore there are no updated outputs in Table 3. A revised Table 3 is attached and reflects the corrected value for the Regulatory Guide Position 2.1 for material region no. 8.
NRC RAI 2:
Regarding observed indications from the most recent inservice inspection (ISI) interval examinations at SONGS Unit 3, as documented in Table 2 of Proposed Alternative,, clearly state the location and size of the one indication that was found in the weld material of the reactor pressure vessel beltline area. Was this indication observed in the 1st and/or 2 nd ISI interval inspections? Did the size of the indication change during the course of the subsequent ISI inspections? If there was a change in the size of the indication, can that change be attributed to improved inspection procedures?
SCE Response:
This indication is 1.1" in length, 0.18" in through-wall extent (2a dimension), and is embedded with an 'S' dimension of 0.57" (as measured from the cladding-to-base-metal interface). Cladding thickness is 0.22" which provides a total embedded depth of 0.79".
This indication was observed in the 2nd ISI interval inspection only, though the Page 1 of 3
characteristics of the flaw do not support concluding the indication to be service-induced. It is likely that the indication was present but not recorded during the 1st ISI interval inspection. The 2nd ISI interval examination was an Appendix VIII (PDI) examination with a much higher sensitivity than the 1st ISI interval Section XI/Regulatory Guide 1.150 examinations. For the 1st ISI interval examination, calibration was performed with the responses from 0.125" diameter side drilled holes normalized to 80%
full screen (DAC). Recording criteria was, for the vessel inner 25% thickness, at 20%
DAC or 16% full screen height (FSH). For the 2nd ISI interval PDI examination, calibration was performed with the responses from 0.063" diameter side drilled holes set to 80% full screen and then increased by 12dB. The recording criteria was to record all valid flaws. The relative gain difference between the two examinations, considering both the difference in calibration reflector size and the addition of 12dB, was approximately 18 dB or 8:1. Since the recorded amplitude of the indication in question was a maximum of 37% FSH, for the 2nd ISI interval examination, it would have resulted in a response of approximately 5% FSH, far below the recording threshold, for the 1st ISI interval examination.
Page 2 of 3
Table 3 summarizes the inputs and outputs for the calculation of through-wall cracking frequency (TWCF).
Table 3:
Details of TWCF Calculation - SONGS Unit 3 at 54 Effective Full Power Years (EFPY)
Inputs Reactor Coolant System Temperature, TRCS[°F]:
N/A Twa11 [inches]:
8.84375
.Region/Component Material Heat C
- 1)
Nii R.G.
CF(2)
Fluence [1019 No.
Cu N
1.99 RTNDT(u) 1) [OF]
Neutron/cm2, Description No.
[wt%]
[wt%]
pos.
[°F]
E > 1.0 MeV]
1 Inter. Shell Long. Weld 83650 0.04 0.17 1.1 40
-40 6.73 2-203 A 2
Inter. Shell Long. Weld 83650 0.05 0.21 1.1 50
-40 6.73 2-203 B 3
Inter. Shell Long. Weld 83650 0.04 0.08 1.1 32
-40 6.73 2-203 C 4
Lower Shell Long. Weld 88114 0.04 0.21 1.1 44
-70 6.52 3-203 A 5
Lower Shell Long. Weld 88114 0.04 0.19 1.1 42
-70 6.52 3-203 B 6
Lower Shell Long. Weld 88114 0.04 0.21 1.1 44
-70 6.52 3-203 C 7
Lower-Inter. Shell Girth 90069 and 0.05 0.04 1.1 34(3)
-50(3) 6.73 Weld 9-203 90144 8
Intermediate Shell SA-533B CI.1 0.06 0.58 2.1 72 40 6.73 C-6802-1 9
Intermediate Shell SA-533B CI.1 0.04 0.57 1.1 26 10 6.73 C-6802-2 10 Intermediate Shell SA-533B CI.1 0.06 0.58 1.1 37 20 6.73 C-6802-3 11 Lower Shell C-6802-4 SA-533B C1.1 0.05 0.56 1.1 31 10 6.52 12 Lower Shell C-6802-5 SA-533B CI.1 0.04 0.55 1.1 26 10 6.52 13 Lower Shell C-6802-6 SA-533B CI.1 0.06 0.62 1.1 37 20 6.52 Outputs Methodology Used to Calculate AT 30:
Regulatory Guide 1.99, Revision 2(4)
Controlling Material Fluence [1019 FF Region No.
RTmxx Neutron/cm2, (Fluence AT30 TWCF9S-xx (From
[OR]
E > 1.0 MeV]
Factor)
[OF]
Above)
Limiting Axial Weld - AW 8
604.5 6.73 1.457 104.87 0.OOE+00 Limiting Plate - PL 8
604.5 6.73 1.457 104.87 2.71 E-12 Circumferential Weld - CW 8
604.5 6.73 1.457 104.87 0.OOE+00 TWCF95.TOTAL(aAwTWCF95-AW + aPLTWCF 95-PL + acwTWCF 95-cw):
6.78E-12 (1) Reference 10 (2) Reference 11 (3) Maximum value for two heats of material (4) Reference 12 Page 3 of 3