ML12024A018
| ML12024A018 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 01/23/2012 |
| From: | V Sreenivas Plant Licensing Branch II |
| To: | Heacock D Dominion Energy Co |
| References | |
| TAC ME7180 | |
| Download: ML12024A018 (3) | |
Text
1 NRR-PMDAPEm Resource From:
Sreenivas, V Sent:
Monday, January 23, 2012 3:05 PM To:
'david.heacock@dom.com' Cc:
'Tom Shaub'; Salgado, Nancy
Subject:
North Anna Unit 2: Request for Addititional Information relief request (RR) N2-I3-PRT-002 (TAC ME7180)
By a letter dated September 21, 2011 (Agencywide Documents Access & Management System (ADAMS) ML11270A122),
the Virginia Electric And Power Company (the licensee) submitted Relief Request (RR) N2-I3-PRT-002 requesting relief from the weld examination coverage requirements specified in American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, 1995 Edition of Section XI up to the 1996 Addenda, as amended by Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a (b)(2)(xv)(A)(2). This RR covers North Anna Power Station, Unit 2 on its third inspection interval that ended on December 13, 2010.
The U.S. Nuclear Regulatory Commission (NRC) staff requests that the licensee provide additional information to support the relief from ASME Code Section XI required volumetric examination of essentially 100% of the seven full-penetration welds.
RAI 1
For Examination Category B-A and B-D items, Requests A1-A5, please address the following questions: Describe the inspection history for these welds including the inspection procedures used and the % coverage obtained in the previous inspections. Where flaw indications were found in the most recent inspections, none of the recordable indications were recorded in the previous examinations and they were all described as subsurface weld flaws indicative of fabrication.
Explain in detail why these recordable indications were not detected by previous examinations and how it was concluded that these indications are fabrication flaws.
RAI 2 -- Sections B2, B3, B4, B5, B6, and R1 To determine the level of safety significance for each weld and/or attachment, NRC staff needs to know which system would be impacted by a leak or failure of the weld or welded attachment in question. This information is provided in the enclosures for some, but not all welds. To assist the NRC staff in assessing each weld and welded attachment, please provide a table for all welds and welded attachment in Request Numbers B2, B3, B4, B5, B6, and R1 that describes the locations of each weld or welded attachment, the components joined by each weld, and the systems to which each welds or welded attachment belongs.
An example where enough information was given was in section R1 Weld 9 (R1-9). The enclosure described weld R1-9 as a reactor coolant pump discharge to cold leg pipe weld. This identifies the system, location, and the components joined by the weld.
RAI 3 -- Section B4 To demonstrate impracticality, the reason for the reduced inspection coverage is required. While the coverage maps are effective at showing where the welds were not inspected, nothing in the submittal explains why these regions were not inspected. Explain in detail the causes of the lack of access to these areas.
RAI 4 -- Section B5 While the data sheets provided in the enclosures partially described the ultrasonic techniques used to inspect the welds, the refracted ultrasonic angles, wave modes (shear or longitudinal), and frequencies used for both axial and circumferential scans were not always clear. Please provide a table describing the weld, the angles, modes, and frequencies used for axial scans and the angles, modes, and frequencies used for circumferential scans.
2 Coverage of some piping welds has been improved by removing weld crowns. For several welds in Section B5 the coverage maps show that the transducers appear to stop at the edge of the weld crown. For each weld, discuss if greater coverage can be obtained by grinding or machining the weld crowns flush with the pipe.
The overall size of a weld, commonly described by the weld diameter, is needed to help determine the safety significance of a weld and the possible consequences of a leak or failure in the weld. Please provide the outer diameters of welds B5-5, B5-6, and B5-8. For dissimilar metal welds, the cracking rates are influenced by the weld alloys and the temperatures at the welds. For welds B5-5 and B5-6, the welds are listed as dissimilar metal welds, but the weld metal is not specified. What are the weld metal alloys for these welds and what are the operating temperatures of these welds?
RAI 5 -- Section B6 While the data sheets provided in the enclosures partially described the ultrasonic techniques used to inspect the welds, the refracted ultrasonic angles, wave modes (shear or longitudinal), and frequencies used for both axial and circumferential scans were not always clear. Please provide a table describing the weld, the angles, modes, and frequencies used for axial scans and the angles, modes, and frequencies used for circumferential scans.
The overall size of a weld, commonly described by the weld diameter, is needed to help determine the safety significance of a weld and the possible consequences of a leak or failure in the weld. Please provide the diameters of welds B6-2 and B6-8.
RAI 6 -- Section R1 While the data sheets provided in the enclosures partially described the ultrasonic techniques used to inspect the welds, the refracted ultrasonic angles, wave modes (shear or longitudinal), and frequencies used for both axial and circumferential scans were not always clear. Please provide a table describing the weld, the angles, modes, and frequencies used for axial scans and the angles, modes, and frequencies used for circumferential scans.
The overall size of a weld, commonly described by the weld diameter, is needed to help determine the safety significance of a weld and the possible consequences of a leak or failure in the weld. Please provide the diameters of welds R1-10, R1-15, R1-16, R1-17, and R1-18.
Please submit your docketed response by February 27th, 2012.
V. Sreenivas, PH.D., C.P.M.,
Project Manager, Rm.#O8F6, LPL2-1 North Anna Power Reactors, Units 1 and 2 Division of Operating Reactor Licensing-NRR (301) 415-2597, v.sreenivas@nrc.gov
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Hearing Identifier:
NRR_PMDA Email Number:
244 Mail Envelope Properties (V.Sreenivas@nrc.gov20120123150400)
Subject:
North Anna Unit 2: Request for Addititional Information relief request (RR)
N2-I3-PRT-002 (TAC ME7180)
Sent Date:
1/23/2012 3:04:48 PM Received Date:
1/23/2012 3:04:00 PM From:
Sreenivas, V Created By:
V.Sreenivas@nrc.gov Recipients:
"'Tom Shaub'" <tom.shaub@dom.com>
Tracking Status: None "Salgado, Nancy" <Nancy.Salgado@nrc.gov>
Tracking Status: None
"'david.heacock@dom.com'" <david.heacock@dom.com>
Tracking Status: None Post Office:
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