NOED-01-2-002 - McGuire Unit 1 (Duke Energy Corporation)


April 24, 2001

Duke Energy Corporation
ATTN: Mr. H. B. Barron
Vice President
McGuire Nuclear Station
12700 Hagers Ferry Road
Huntersville, NC 28078-8985


Dear Mr. Barron:

By letter dated April 23, 2001, you formally documented a verbal request made on April 21, 2001, for discretionary enforcement concerning McGuire Nuclear Station Unit 1 Technical Specification (TS) 3.8.7, Inverters-Operating. Your letter addressed the information previously discussed with the NRC in a telephone conference on April 21, 2001, at 8:00 p.m. EDT. The principal NRC staff members who participated in that telephone conference included: L. A. Reyes, Regional Administrator, Region II (RII); H. N. Berkow, Director, Project Directorate II (LPD2), Office of Nuclear Reactor Regulation (NRR); L. R. Plisco, Director, Division of Reactor Projects (DRP), RII; R. L. Emch, Section Chief, LPD2-1, NRR; R. C. Haag, Chief, Reactor Projects Branch 1, DRP, RII; C. P. Patel, Project Manager, LPD2-1, NRR; C. F. Holden, Section Chief, Electrical Instrumentation and Controls Branch (EEIB), Division of Engineering (DE), NRR; M. Chiramal, EEIB, DE, NRR; and E. W. Weiss, Section Chief, Plant Systems Branch, Division of Systems Safety and Analysis, NRR. Because of a failure of vital inverter 1EVIB, you stated that on April 22, 2001, at 6:00 a.m., McGuire Unit 1 would not be in compliance with TS 3.8.7, Limiting Condition for Operation (LCO), Action A.1, which requires restoration of a failed vital inverter to operable status within 24 hours. As such, per Action B.1, Unit 1 would be required to be in Mode 3 (Hot Standby) in 6 hours and, per Action B.2, be in Mode 5 (Cold Shutdown) in 36 hours. TS 3.8.7, Action A.1, was entered on April 21, 2001, at 6.00 a.m. You requested that a Notice of Enforcement Discretion (NOED) be issued pursuant to the NRC's policy regarding exercise of discretion for an operating facility, set out in Section VII.c, of the "General Statement of Policy and Procedures for NRC Enforcement Actions" (Enforcement Policy), NUREG-1600, and be effective for an additional 120 hours (144 hours total) to complete repairs, testing, and the restoration of vital inverter 1EVIB to operable status. This letter documents our subsequent telephone conversation on April 21, 2001, at approximately 9:00 p.m., when we verbally issued the NOED for an additional 36 hours (60 hours total). We understand that, as stated in your letter, the actual work was completed and vital inverter 1EVIB was declared operable at 5:18 a.m., on April 22, 2001, within the original required action completion time of 24 hours. Therefore, the subject NOED was not used.

McGuire Unit 1 was operating at 100 percent power when the feeder breaker to vital inverter 1EVIB opened for undetermined reasons. Abnormal Procedure recovery actions were completed by the control room operators and the vital bus which is powered by inverter 1EVIB was re-powered by an alternate regulated AC power source. Your safety significance evaluation and.DEC 2 qualitative risk assessment, derived from a probabilistic risk analysis, concluded that an additional 120 hours to effect repairs, testing, and restoration of vital inverter 1EVIB to an operable status, was non-risk-significant in that the calculated change in core damage frequency was 1.7E-7 per day. In addition, you concluded that no significant hazard consideration was involved. Your compensatory measures, to be taken until vital inverter 1EVIB was returned to service, included: (1) making each shift aware of the impact of the failed inverter on normal and emergency plant operations; (2) suspension of switchyard maintenance that could cause a loss-of-offsite power event; and (3) not intentionally removing the regulated alternate AC power source from service except for short periods of time to support troubleshooting and final restoration of inverter 1EVIB. It was understood, that had any unplanned adverse situation occurred which rendered another inverter inoperable, Unit 1 would have complied with the Required Action and Completion Time of TS LCO 3.0.3.

On the basis of the staff's evaluation of your request and the information provided in your letter dated April 23, 2001, we concluded that an NOED was warranted because we were clearly satisfied that this action involved minimal or no safety impact, was consistent with the enforcement policy and staff guidance, and had no adverse impact on public health and safety. Therefore, it was our intention to exercise discretion not to enforce compliance with TS 3.8.7 for the period from April 22, 2001, at 6:00 a.m. until April 23, 2001, at 6:00 p.m. However, as stated above, subsequent to our verbally granting this NOED on April 21, 2001, you exited TS 3.8.7 prior to the TS action completion time and the NOED was not used.

  Luis A. Reyes
Regional Administrator

Docket No.: 50-369
License No.: NPF-9

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