DCL-07-032, Response to NRC Request for Additional Information Regarding ASME Section XI Inservice Inspection Program Relief Requests NDE-SLH U2 and NDE-LSL U2
| ML070880743 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 03/23/2007 |
| From: | Becker J Pacific Gas & Electric Co |
| To: | Document Control Desk, NRC/NRR/ADRO |
| References | |
| DCL-07-032 | |
| Download: ML070880743 (4) | |
Text
Pacific Gas and Electric Company James R. Becker Vice President Diablo Canyon Operations and Station Director Diablo Canyon Power Plant P. 0. Box 56 Avila Beach, CA 93424 805.545.3462 Fax: 805.545.4234 March 23, 2007 PG&E Letter DCL-07-032 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 and 2 Response to NRC Request for Additional Information Regardinq ASME Section XI Inservice Inspection Proqram Relief Requests NDE-SLH U2 and NDE-LSL U2
Dear Commissioners and Staff:
PG&E Letter DCL-06-099, "ASME Section Xl Inservice Inspection Program Relief Requests NDE-SLH U2 and NDE-LSL U2," dated August 24, 2006, submitted requests for relief associated with the reactor vessel lower shell-to-bottom head circumferential weld and lower shell longitudinal weld examinations performed during Diablo Canyon Power Plant (DCPP) Unit 2 Refueling Outage 13.
On January 30, 2007, the NRC staff requested additional information required to complete the review of these relief requests. PG&E's responses to the staff's questions are provided in Enclosure 1.
This information does not affect the results of the technical evaluation previously transmitted in PG&E Letter DCL-06-099.
PG&E makes no regulatory commitments (as defined by NEI 99-04) in this letter.
This letter includes no revisions to existing regulatory commitments.
If you have any questions, or require additional information, please contact Stan Ketelsen at (805) 545-4720.
A member of the STARS (Strategic Teaming and Resource Sharing)
Altiance Callaway
- Comanche Peak e Diablo Canyon
- Palo Verde
- South Texas Project
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Document Control Desk March 23, 2007 Page 2 PG&E Letter DCL-07-032 whyl/4279 Enclosure cc:
Edgar Bailey, DHS Terry W. Jackson Bruce S. Mallett Diablo Distribution cc/enc: Alan B. Wang A
member of the STARS (Strategic Teaming and Resource Sharing)
Alliance Callaway o Comanche Peak o Diablo Canyon o Palo Verde o South Texas Project
- Wolf Creek PG&E Letter DCL-07-032 ENCLOSURE 1 Response to NRC Request for Additional Information Regarding ASME Section XI Inservice Inspection Program Relief Requests NDE-SLH U2 and NDE-LSL U2 The licensee requested relief from performing ultrasonic testing of less than essentially 100 percent of the weld volume as required by the Section X1 of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for some of the reactor vessels welds at the Diablo Canyon Power Plant, Unit 2. To determine whether the ultrasonic test inspection coverage of 75.36 percent and 80. 01 percent of the Diablo canyon Power Plant, Unit 2 reactor vessel lower shell-to-bottom head circumferential weld and reactor vessel lower shell longitudinal weld, respectively, provides reasonable assurance of the structural integrity of these welds, the NRC staff requests the following:
NRC Question 1:
Provide details on other inspections that were performed on these welds (i.e., visual inspection, pressure test, etc) for the Unit 2 2R13 refueling outage in April 2006.
Include the type of inspection (i.e., VT-1, VT-2, etc.), the applicable ASME Code requirements used, and the extent of these inspections performed.
PG&E Response:
In addition to the ultrasonic examinations of the lower shell-to-bottom head weld and the three lower shell longitudinal welds performed in 2R13, VT-3 visual examinations by certified personnel were performed on the core support lugs and surrounding vessel surface including the area of the subject welds, from inside the reactor vessel using remote underwater cameras. These visual examinations were performed in accordance with Table IWB-2500-1, Category B-N-i, Item B13.10, and Category B-N-2, Item B13.60 in the 1989 Edition of Section XI. Due to the vessel cladding and core support lugs themselves, the vessel shell welds are not directly visible during these examinations, although the complete area of the welds was examined. No recordable indications were identified.
Also, a system leakage test at full system temperature and pressure was conducted at the end of the 2R1 3 outage, during which the full system pressure of 2235 psig was held for a minimum of four hours prior to the examination, in accordance with Table IWB-2500-1, Category B-P, Item B15.10 in the 1989 edition of Section XI.
During the pressure test, a VT-2 visual examination by certified examiners was conducted of the area under the reactor vessel including all accessible surfaces of vessel insulation and the bottom mounted instrument tubes. No indications or evidence of leakage was detected.
1 PG&E Letter DCL-07-032 NRC Question 2:
Provide information on whether any indications (and their extent) were found for these welds during the ultrasonic test inspections, or the other inspections identified in response to Question 1, during the Unit 2 2R13 refueling outage in April 2006.
PG&E Response:
No indications were found during the VT-3 visual examinations or the VT-2 visual examination during the pressure test as discussed in the response to NRC question 1 above.
No indications were found during the ultrasonic examination of the portion of the lower shell-to-bottom head weld accessible for inspection (75.3 percent).
Of the three (3) lower shell course longitudinal welds, two (2) had no ultrasonic indications in the portion of each weld accessible for inspection (80.01 percent each).
The remaining lower shell course longitudinal weld, weld number 3-201A at 60 degrees, had three (3) recordable indications in the portion accessible for inspection (80.01 percent).
The first indication had a minimum depth of 0.64 inches and maximum depth of 0.77 inches and was 2.1 inches long. The second indication had a minimum depth of 1.0 inches and maximum depth of 1.13 inches and was 2.1 inches long. The third indication had a minimum depth of 3.09 inches and a maximum depth of 3.22 inches and was 0.75 inches long. The three indications were all evaluated to be subsurface planar indications and found to be acceptable per ASME Section XI, 1989 Edition, Table IWB-3510-1.
The ultrasonic examinations met the requirements of ASME Section XI, Appendix VIII, Supplements 4, 6, and 7 in the 1995 Edition with 1996 Addenda as modified by 10 CFR 50.55a and implemented by the Performance Demonstration Initiative. The complete examination record is on file at the plant site.
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