NL-18-1130, Units 1 and 2 - Relief Request VEGP-ISI-RR-03: SNC Response to NRC Request for Additional Information
| ML18269A094 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 09/26/2018 |
| From: | Gayheart C Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-18-1130 | |
| Download: ML18269A094 (4) | |
Text
~ Southern Nuclear SEP 2 6 2018 Docket Nos.: 50-424 50-425 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Cheryl A. Gayheart Regulatory Affatrs Director Vogtle Electric Generating Plant-Units 1 and 2 Relief Request VEGP-ISI-RR-03 SNC Response to NRC Request for Additional Information Ladies and Gentlemen:
3535 Colonnade Parkway Birmingham, AL 35243 205 992 5316 tel 205 992 7601 tax cagayhea@ southernco.com NL-18-1130 By letter dated May 24, 2018 (Agencywide Documents Access and Management System Accession Number ML18144B012), Southern Nuclear Operating Company (SNC) requested relief from certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI. This relief request, VEGP-ISI-RR-03, pertains to examination coverage of some pressurizer and steam generator welds achieved during the third inservice inspection interval at the Vogtle Electric Generating Plant, Units 1 and 2.
By email dated August 13, 2018, the NRC staff notified SNC that additional information is needed for the staff to complete their review. Enclosure 1 to this letter provides the SNC response to the NRC request for additional information (RAI).
This letter contains no NRC commitments. If you have any questions, please contact Jamie Coleman at 205.992.6611.
Respectfully submitted, Cheryl A.
a eart Director, Regulatory Affairs Southern Nuclear Operating Company CAG/kgl/sm
Enclosure:
Regional Administrator, Region II NRR Project Manager-Vogtle 1 & 2 Senior Resident Inspector-Vogtle 1 & 2 RType: CVC7000
Vogtle Electric Generating Plant-Unit 1 and 2 Relief Request VEGP-ISI-RR-03 SNC Response to NRC Request for Additional Information SNC Response to NRC Request for Additional Information (RAI) to NL-18-113a SNC Response to NRC Request for Additional Information (RAI)
NRC RAI1 For the components associated with this relief request, please provide the following information:
- a. A confirmation that the peak stress in the ultrasonic testing (UT) missed region is likely to be similar to or less than the peak stress in the UT covered region, which demonstrates that the UT results with the reported coverage are representative of the entire component weld. This confirmation should be based on stress reports for each pressurizer nozzle-to-vessel weld (Category 8-D, Item No. 83.11 a with coverage from 15 percent to 55.9 percent).
- b. Past plant-specific and fleet operating experience, if available, regarding leakage and UT indications detected from all affected pressurizer and steam generator welds (Category 8-8, Item Nos. 82.11 and 82.4a; and Category 8-D, Item No. 83.11 a) that required flaw evaluations or repairs.
- a. The areas for credited limited coverage for the 4" Upper Head Spray Nozzles and the S" Safety and Relief Valve Nozzles start at the center line of the nozzle weld and continues towards the nozzle. Figure 1 below shows a typical representation of scan limitations. The area between the lines show the credited coverage with the axial scans (pink-ao, red-45°, blue-sao). The grey area shows the Code coverage required and the cross-hatched area indicates where Code coverage could not be obtained.
Typical NozzJe
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Figure 1 - 4" and S" Nozzle Coverage The areas for credited limited coverage for the 14" surge nozzles are shown in Figure 2 below. Due to the heater coupling penetrations, there are limitations on the vessel head side of the weld also. Although credit was only taken for the scans starting at the heater coupling penetrations going toward the nozzle, UT scanning is performed where accessible between the penetrations. The area between the lines show the credited coverage with the axial scans (pink-ao, red-45°, blue-sao). The grey area shows the Code coverage required and the cross-hatched area indicates where Code coverage could not be obtained.
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Surge Nozzle Vessel Head Figure 2 - 14" Nozzle Coverage For the 4" Spray Nozzles and 14" Surge Nozzles, the stress report shows a lower stress ratio going toward the nozzle. The peak stress in the ultrasonic testing (UT) missed region is likely to be similar to or less than the peak stress in the UT covered region. For the 6" Safety and Relief Valve Nozzles, the design stress ratio is slightly higher in the area of limited scanning.
However, the ratios are of similar magnitude and the representative of the entire component in the inspection region of interest.
To give added confidence, these nozzles receive an Inside Radius Section examination required by 1 OCFR50.55a and a supplemental surface (magnetic particle) examination. Both examinations have 100% coverage for the areas inspected. No recordable indications were found with these examinations.
- b. In reviewing the SNC fleet operating experience, (Vogtle Units 1 and 2 and Farley Units 1 and 2) no leakage or indications that require flaw evaluations or repairs have been found from the Category B-8, Item Nos. 82.11 and 82.40; and Category 8-0, Item No. 83.110.
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