ML082560148

CT LAR Request for Additional Information

ML082560148
Person / Time
Site:	Diablo Canyon
Issue date:	08/20/2008
From:	Wang A Plant Licensing Branch IV
To:	Grozan T Pacific Gas & Electric Co
References
TAC MD7512, TAC MD7513
Download: ML082560148 (2)

Text

From:

Alan Wang Sent:

Wednesday, August 20, 2008 11:30 PM To:

Tom Grozan

Subject:

CT ECCS LAR RAIs Tom, here is the RAI. It came in while I was away. Let me know if you want a call before I issue. Alan

1. The submittal identified open review findings arising from a focused peer review conducted on the upgraded human reliability analysis (HRA) and from three limited scope peer reviews conducted on unspecified portions of the probabilistic risk assessment (PRA) model. The licensee stated that these findings will be dispositioned. In order to support this licensing action, these items must be either demonstrated not to significantly impact the risk-informed decision, or the items must be resolved, the PRA model updated, and the risk impacts re-evaluated using the updated model. For each open review finding, the licensee is requested to provide an appropriate summary of the deficiency identified, and a description of how the item has been resolved to support this licensing action, including the results of any sensitivity analyses. If revised risk results are necessary, update all sensitivity cases of the submittal.

2. The submittal states the expectation that annual unavailability of the affected components in the Emergency Core Cooling System (ECCS) and Containment Spray (CS) system will not change once the completion times (CT) associated with the Technical Specifications (TS) are extended. The basis for this assumption is the continued emphasis on timely completion of maintenance. A sensitivity analysis is provided showing the impact of doubling the current unavailabilities. However, the submittal also identifies an administrative control on work planning for using only 50% of the CT. Therefore, approval of this amendment would increase the administratively allowable time for maintenance from 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> to 7 days, which would provide additional opportunities to perform significant work activities online.

The licensee is requested to discuss its existing administrative controls governing timely completion of maintenance, and specifically how the TS CT is factored into the decision process for maintenance resources and scheduling. The licensee should also discuss if any of the affected equipment is subject to extended maintenance (greater than 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />) during plant outages, and if these activities could be performed during operation under the proposed TS extended CT. The licensee is also requested to provide a sensitivity analysis using a factor of 14/3 to reflect the requested CT extension, rather than a factor of two.

3. The submittal (Tables 4-2 and 4-3) shows that the CS system and Safety Injection (SI) subsystem of the ECCS play no role in mitigation of seismic events. This would mean there is no credible earthquake which could induce a loss of coolant accident, nor is feed-and-bleed cooling via the ECCS required for seismic event response. The licensee is requested to provide additional details regarding the role of these systems and of the Centrifugal Charging subsystem of the ECCS, in mitigating seismic events to justify the risk results presented.

4. Identify and justify the truncation level applied for this application.

5. Describe how the affected systems for this application (i.e., CS, high and low pressure SI, and centrifugal charging) are modeled in the PRA; specifically, address the following for each system:

Any portions of the system not modeled which are required for TS operability; Success criteria and basis, including if the success criteria differs from the licensing basis; Accident sequences and initiating events crediting the system, including any alternative success paths if the system is unavailable; Plant-specific data supporting the system; and Performance history of the system.

E-mail Properties Mail Envelope Properties (419623E8C7444444BF132DA3AE69EDA2105D7C3F63)

Subject:

CT ECCS LAR RAIs Sent Date: 8/20/2008 11:29:49 PM Received Date: 8/20/2008 11:29:00 PM From: Alan Wang Created By: Alan.Wang@nrc.gov Recipients:

TCG5@PGE.com (Tom Grozan)

Tracking Status: None Post Office:

HQCLSTR02.nrc.gov Files Size Date & Time MESSAGE 7948 8/20/2008 Options Expiration Date:

Priority: olImportanceNormal ReplyRequested: False Return Notification: False Sensitivity: olNormal Recipients received: