IR 05000213/1993080
| ML20024H829 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 08/16/1993 |
| From: | Hodges M NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Opeka J CONNECTICUT YANKEE ATOMIC POWER CO. |
| References | |
| NUDOCS 9308190253 | |
| Download: ML20024H829 (4) | |
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AUG 161393 Docket No. 50-213 i
Mr. John '
Executive Vice President - Nuclear Connecticut Yankee Atomic Power Company P. O. Box 270
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Hartford, Connecticut 06141-0270
Dear Mr. Opeka:
SUBJECT:
NRC AUGMENTED INSPECTION TEAM (AIT) REGARDING TWO LOSS l
OF OFFSITE POWER EVENTS AND THE LOSS OF MOTOR-CONTROle
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CENTER-5 NRC REPORT NO. 50-213/93-80
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The enclosed report refers to the NRC Augmented Inspection Team (AIT), led by Mr. James Trapp of this office, on June 30 through July 9,1993, at the Haddam Neck Plant in Haddam, Connecticut. The purpose of this inspection was to review the circumstances
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regarding two separate loss of offsite power events, and a loss of motor-control-center-5 i
(MCC-5) that occurred during the conduct of test activities. At the conclusion of the
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inspection, the team findings were discussed with Mr. Stetz and members of your staff at an exit meeting that was open for public observation on July 27,1993.
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The scope of the inspection included developing a detailed event description, evaluating the root causes for the events, assessing the effectiveness of corrective actions, and evaluating l
the safety significance of each event. The inspection consisted of selective examination of procedures and representative records, abservations of testing and inspections, and interviews with personnel, i
The loss of offsite power events were significant because they caused a temporary loss of shutdown cooling and the loss of offsite power is a precursor to station blackout. The reliable operation of MCC-5 is vital to plant safety because both trains of emergency core cooling system injection valves are powered from this motor-control-center. Based on the significance of these events, all of which occurred in a short time period, the NRC dispatched an AIT.
OFFICIAL RECORD COPY A:HN9380. INS 190077 fI 8 508 M 0z53 ) g &
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AUG i s 1993
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Mr. John f (
i The root causes for the Jr.ne 22 and June 26,1993, loss of offsite power events were
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positively identified as a wiring error and a blown fuse, respectively. For both events, the j
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, operator actions to mitigate the consequences of the events were appropriate. The corrective l
actions taken in response to these events were reviewed by the AIT and determined to be l
acceptable. The NRC team concluded that these events were the result of defective
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nonsafety-related equipment and were not the result of recent performance deficiencies by
.j plant staff or procedures.
The root cause for the June 27,1993, failure of the MCC-5 automatic bus transfer scheme
was not positively identi5ed. Although the root cause was not identified, two highly suspect components were identified and replaced. Your corrective actions and compensatory measures taken to ensure the reliability of MCC-5 were outlined in your letter to the NRC, dated July 15,1993, " Commitments to Test Motor-Control-Center-5." We have reviewed l
these commitments and determined that the proposed actions and compensatory measures are
appropriate. While trouble-shooting the automatic bus transfer (ABT) failure, your staff l
identified a potential generic problem with the Westinghouse DB 25 breaker,52X relays. At j
the conclusion of this inspection, this potentially generic breaker failure concern was still
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under review by your staff and the breaker vendor. We expect that this issue will be
resolved and appropriate actions will be taken in an expeditious manner. In addition, your
letter states that you plan to conduct a review of potential design changes to the ABT which.
could improve the reliability of this scheme. We request that you provide the results of this
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design review and the schedule for implementing any design changes identified to the j
Region I Regional Administrator.
j The NRC team also noted two issues regarding the licensing basis of MCC-5. The updated
UFSAR, Section 8.3, states, in part, that "The Class lE system has the redundancy,
capacity, capability, and reliability to supply power to all safety-related loads. This system
ensures a safe plant shutdown to mitigate accident effects, even in the event of a single
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failure." This statement does not appear to be accurate as related to single failures and l
MCC-5. In addition, the team questioned the applicability of 10 CFR 50.46(d), which
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explicitly states that the performance of the emergency core cooling system (ECCS) system l
must include in particular Criterion 35 of Appendix A, which requires that the ECCS safety
function be accomplished assuming a single failure. The current design of the ECCS system l
does not satisfy the requirement of Criterion 35 due to the single failure vulnerabilities of
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MCC-5. While the team noted that an exemption had been granted by the NRC for the MCC-5 single failure vulnerability during original plant licensing, an explicit exemption from l
the 50.46 requirement was not apparent to the team. Both of these issues are currently being reviewed by the NRC.
In accordance with 10 CFR 2.790 of the Commission's regulations, a copy of this letter and
the enclosed inspection report will be placed in the NRC Public Document Room.
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i OFFICIAL RECORD COPY A:HN9380. INS
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Mr. John We will gladly diruss any questions you have concerning this inspection.
Sincerely, Q'
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W Marvin W. Hodges, Director Division of Reactor Safety Enclosure: NRC Region I Inspection Report No. 50-213/93-80 cc w/ encl:
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W. D. Romberg, Vice President, Nuclear, Operations Services J. P. Stetz, Vice President, Haddam Neck Station
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G. H. Bouchard, Director, Nuclear Quality Services D. J. Ray, Unit Director R. M. Kacich, Director, Nuclear Licensing Gerald Garfield, Esquire Nicholas Reynolds, Esquire K. Abraham, PAO (2)
Public Document Room (PDR)
Local Public Document Room (LPDR)
Nuclear Safety Information Center (NSIC)
NRC Resident Inspector State of Connecticut SLO OFFICIAL RECORD COPY A:HN9380. INS
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AUG 161993 Mr. John