ML102240573

E-mail Regarding Request for Additional Information RR N1-I4-RI-001 and N2-I4-RI-001

ML102240573
Person / Time
Site:	North Anna
Issue date:	08/12/2010
From:	V Sreenivas Plant Licensing Branch II
To:	Heacock D Virginia Electric & Power Co (VEPCO)
Sreenivas V.NRR/DORL/LPL2-1 415-2597
References
TAC ME3449, TAC ME3450
Download: ML102240573 (2)

Text

From: Sreenivas, V Sent: Thursday, August 12, 2010 3:21 PM To: 'david.heacock@dom.com' Cc: 'Tom Shaub'; 'david.sommers@dom.com'; 'Ginger L Alligood'; Kulesa, Gloria; Patel, Jigar; Hoffman, Keith

Subject:

Request for Additional Information for North Anna RR N1-I4-RI-001 and N2-I4-RI-001(TAC NOS. 3449 and 3450)

Importance: High By letter dated February 23, 2010, Virginia Electric and Power Company (VEPCO), submitted for staff review and approval ISI Program Relief Requests N1-I4-RI-001 and N2-I4-RI-001, which requests an alternative risk-informed inservice inspection (RI-ISI) selection and examination criteria for Category B-F, B-J, C-F-1 and C-F-2 pressure retaining piping welds for the North Anna Power Station (NAPS) Units 1 & 2. The U.S Nuclear Regulatory Commission (NRC) has reviewed the risk informed evaluation submitted by VEPCO, in support of its request for approval of fourth ten-year interval inservice inspection program plan. The NRC has identified areas where additional information is needed to complete its review. The request for additional information is listed as follows:

1. NRC has not endorsed Electric Power Research Institute (EPRI) Topical Report 1018427. The questions listed below address the quality of North Anna probabilistic risk assessment (PRA) model.

A. A self assessment performed on the North Anna PRA model in August 2007 identified PRA modeling and documentation supporting requirements (SRs) where the PRA model did not meet Capability Category (CC) II of the ASME (American Society of Mechanical Engineers) PRA standard. In December 2009, a model update was performed to meet Category II of the ASME PRA standard and Regulatory Guide 1.200 Rev 1. Please identify and disposition any remaining differences with CC II requirements (i.e., open items) that may affect this application.

B. The supporting requirement (SR), IF-C6 and IF-C8, permits screening out of flood areas based on, in part, the success of human actions to isolate and terminate the flood. The endorsed RI-ISI methods require determination of the flood scenario with and without human intervention which corresponds to the capability category III, i.e. scenarios are not screened out based on human actions. Therefore a category III analysis would be acceptable. To provide confidence that scenarios that might exceed the quantitative CDF and LERF guideline are identified, please describe how credit is given to human actions if the current application analysis does not meet Capability Category III for these supporting requirements.

2. Table IWB-2500-1 of ASME,Section XI, 2001 Edition with 2003 Addenda requires volumetric and/or surface examination of all Category B-F or B-J Pressure Retaining Dissimilar Metal Welds greater than NPS 1. Based on recent findings of primary water stress corrosion cracking in Alloy 82/182 dissimilar metal welds the staff would like more information on your inspection plans for these welds in the 4th Interval ISI Plan for NAPS Units 1 & 2.

3. Describe the inspection plan of Alloy 82/182 dissimilar metal welds greater than NPS 1 in the 4th Interval ISI Plan for NAPS Units 1 & 2 (e.g., are these welds included in the number of welds selected for examination in the RI-ISI program, how many of these welds are selected for examination, what examination method(s) are being employed, what is the frequency of examination, how is disposition of limited coverage (<90%)

examinations handled, etc.).

4. Section 3.3 of the February 23, 2010 submittal states that, In contrast to a number of RI-ISI Program applications where percentage of Class 1 piping locations selected for examination has fallen substantially below 10%, Code Case N-716 mandates that 10%

be chosen. Immediately below this paragraph a brief summary is provided showing the number of welds in Class 1, 2 and non-class systems along with the number of welds selected for examination for NAPS Units 1 & 2. According to this summary the number of Class 1 welds selected for examination on Unit 2 is significantly less than 10% of the total number of Class 1 welds. Please explain this discrepancy. Also the total number of welds shown in the summary in Section 3.3 for Unit 2 does not agree with the Weld Count column total value shown in Table 3.1b of the February 23, 2010 submittal.

Please explain this discrepancy.

Please submit the responses by September 13, 2010. If you have any questions, please contact me.

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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