ML102770411

Draft RAI Questions on the 4th 10-Year-Interval Inservice Inspection Program

ML102770411
Person / Time
Site:	Cook
Issue date:	10/04/2010
From:	Tam P S Plant Licensing Branch III
To:	Etheridge H L, Scarpello M K, Waters J R American Electric Power Co
Tam P S
References
TAC ME4495, TAC ME4496
Download: ML102770411 (3)

Text

Accession No. ML102770411

From: Tam, Peter Sent: Monday, October 04, 2010 9:21 AM To: hletheridge@aep.com; 'jrwaters@aep.com'; mkscarpello@aep.com Cc: Patel, Jigar; Patnaik, Prakash

Subject:

D.C. Cook Units 1 and 2 - Draft RAI on the 3/12/10 submittal re. the 4th 10-year interval ISI program (TAC ME4495 and ME4496)

Helen:

The NRC staff is continuing its review of your 3/12/10 submittal regarding inservice inspection for the 4 th 10-year interval (Accession No. ML100750680). In the probabilistic risk assessment (PRA) aspect the NRC staff came up with the following draft RAI questions. We would like to hold a conference call with you to discuss these questions and how they may be dispositioned. However, with or without the proposed conference call, I plan to issue these questions in a formal RAI by 10/19/10.

1. Supporting requirement (SR) IF-C3 in American Society of Mechanical Engineers (ASME) Probabilistic Risk Assessment ( PRA) Standard RA-Sb-2005 identifies the failure mechanisms that shall be evaluated to determine the susceptibility of each safety-related structure, system, and component (SSC) in a flood area to flood-induced failures. Capability category II identifies failure by submergence and spray as requiring detailed analysis. Capability category III includes jet impingement, pipe whip, and humidity, condensation, and temperature concerns. Risk informed inservice inspection (RI-ISI) requires that all SSC failures induced by a pipe break be considered. Please demonstrate that all SSC failures that are induced by a pipe break are adequately addressed in your analysis.

2. SR IF-C6 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 is needed. To provide confidence that scenarios that might exceed the quantitative core damage frequency and larger early release frequency guideline are identified, please describe how credit is given to human actions.

3. SR IF-D5a addresses the development of flood initiating (pipe rupture) frequencies for use during the scenario development. The risk-informed inservice Inspection program is premised on inspecting locations with the highest risk, driven mostly by failure frequency. The plant-specific information collected and used should include experience related to degradation mechanisms that could indicate increased likelihood of pipe failure at particular locations.

Please describe how plant-specific operating experience was used to identify experience related to degradation mechanisms and how this experience was incorporated into the development of pipe failure frequencies.

4. Code Case N-716 has a minimum requirement of high safety significant inspections and relies on the PRA flooding analysis to identify additional inspection areas. Please verify that a flooding analysis was performed for the fourth ten-year interval inspection and state whether any high consequence segments (lower bound conditional core damage probability and conditional large early release probability of 1E-4 and 1E-5, respectively) were found for low safety significant piping. The sole intent of this e-mail is to prepare you and others for the proposed conference call. This e-mail does not formally request for additional information, and does not convey a formal NRC staff position.

Peter S. Tam , Senior Project Manager (for D.C. Cook and Monticello) Plant Licensing Branch III-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Tel. 301-415-1451

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Subject:

D.C. Cook Units 1 and 2 - Draft RAI on the 3/12/10 submittal re. the 4th 10-year interval ISI program (TAC ME4495 and ME4496)

Sent Date: 10/4/2010 9:21:29 AM Received Date: 10/4/2010 9:21:00 AM From: Tam, Peter

Created By: Peter.Tam@nrc.gov

Recipients:

hletheridge@aep.com (hletheridge@aep.com) Tracking Status: None jrwaters@aep.com ('jrwaters@aep.com') Tracking Status: None mkscarpello@aep.com (mkscarpello@aep.com)

Tracking Status: None Jigar.Patel@nrc.gov (Patel, Jigar)

Tracking Status: None Prakash.Patnaik@nrc.gov (Patnaik, Prakash)

Tracking Status: None

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HQCLSTR02.nrc.gov

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