ML14128A512

Summary of Regulatory Conference to Discuss Safety Significance of Arkansas Nuclear One Unit 1 Dropped Stator

ML14128A512
Person / Time
Site:	Arkansas Nuclear
Issue date:	05/09/2014
From:	Greg Werner NRC/RGN-IV/DRP/RPB-E
To:	Jeremy G. Browning Entergy Operations
Werner G
References
EA-14-008
Download: ML14128A512 (111)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION REGION IV 1600 E LAMAR BLVD ARLINGTON, TX 76011-4511 May 9, 2014 EA 14-008 Jeremy Browning, Site Vice President Arkansas Nuclear One Entergy Operations, Inc.

1448 SR 333 Russellville, AR 72802-0967

SUMMARY

OF REGULATORY CONFERENCE TO DISCUSS SAFETY SIGNIFICANCE OF ARKANSAS NUCLEAR ONE UNIT 1 DROPPED STATOR

Dear Mr. Browning:

On May 1, 2014, members of the U.S. Nuclear Regulatory Commission (NRC) staff met with representatives of the Arkansas Nuclear One facility to discuss the apparent violation affecting both units related to the drop of the Unit 1 main generator stator as documented in NRC Inspection Report 05000313;368/2013012, issued on March 24, 2014 (ML14083A409). The focus of the regulatory conference was a discussion on the safety significance of the finding.

The discussion included Unit 1 mitigating actions focusing on the use of temporary power to recover the electrical buses and Unit 2 procedural electrical power recovery actions.

For Unit 1, three non-proceduralized and non-engineered success paths associated with recovery of electrical power were discussed, with the variation of Success Path 1 being actually used, after the event, to restore power to the vital buses within 6 days. Your staff indicated that this power was available for use within 4.4 days and could have been used in an emergency.

The delay on re-energizing the vital buses with offsite power was based on completing and approving the engineering, installation, and operating procedures documentation. The three success paths all had estimated times to being available to re-energize the electrical buses of 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br /> or less. This information was discussed during your presentation on Slides 15 - 35. Your staff also discussed other recovery actions. Based on credit for the recovery options, your staff estimated the conditional core damage probability of 5.5E-6.

For Unit 2, the focus was on procedurally directed electrical power recovery strategies. This information was discussed during your presentation on Slides 81 - 86. Based on these recovery options, your staff estimated the conditional core damage probability of 1.8E-6.

The NRC staff asked questions during the Regulatory Conference, with some questions requiring additional information that you indicated you would supply to us by Friday, May 9. The NRC will continue to review the information that you provided during the Regulatory Conference and the

subsequent information that was requested in order to reach a final significance determination.

We are developing our final risk significance and will issue a final significance determination letter in June.

A copy of your presentation slides is included as Enclosure 1. Copies of the NRC slides (Enclosure 2) and meeting attendance (Enclosures 3 and 4) are included.

This regulatory conference was transcribed, and a copy of the transcription will be made available and placed into the NRCs Agencywide Documents Access and Management System (ADAMS). This Category 1 public meeting was attended by 52 members of the public, both telephonically and in the Region IV office.

In accordance with 10 CFR 2.390 of the NRCs Rules of Practice, a copy of this letter and its enclosures will be available electronically for public inspection in the NRCs Public Document Room or from the Publicly Available Records (PARS) component of the NRCs ADAMS. ADAMS is accessible from the NRC web site at http://www.nrc.gov/reading-rm/adams.html (The Public Electronic Reading Room).

Sincerely,

/RA/

Gregory E. Werner, Chief Project Branch E Division of Reactor Projects Docket Nos.: 50-313, 50-368 License Nos.: DPR-51, NPF-6

Enclosures:

1. ANO Presentation Slides

2. NRC Slides

3. Meeting Attendance at Region IV

4. Meeting Attendance by Phone

Arkansas Nuclear One Regulatory Conference Nuclear Regulatory Commission - Region IV Arlington, TX May 1, 2014 1

Enclosure 2

Agenda

• Introduction of Participants

• NRC Opening Remarks

• Licensee Presentation

• NRC Caucus

• Final Questions

• Closing Remarks

• Conference Adjournment

• Questions and Comments from Members of the Public 2

Enclosure 2