05000287/LER-1984-001, :on 840105,discovered 3TE Switchgear Load Shed Source B Fuse Block Not Installed.Cause Unknown.Fuse Block Reinstalled & Station Mod to Install Fuse Blocks & Add Computer Alarms Will Be Completed
| ML20080N818 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 02/06/1984 |
| From: | Petty J, Tucker H DUKE POWER CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| LER-84-001, LER-84-1, NUDOCS 8402220352 | |
| Download: ML20080N818 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(1) |
| 2871984001R00 - NRC Website | |
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LICENSEE EVENT REPORT (LER) i
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., nei On January 5. 1984 at 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> with Unit 3 at 100% FP, the 3TE Switengear Load Shed Source B fuse block was discovered to not be installed.
This source B fuse block provides power to only load shed relay 3ELS2. This relay is one of the two relays that can trip eight non-essential components during a load shed actuation. Technical Specification 3.7.2(b) states that "the circuits or channels of any single functional unit of the EPSL (Emergency Power Switching Logic) may be inoperable for test of maintenance for periods not exceeding 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />" (provided that certain conditions are met).
Part of channel B was not operative causing it to be degraded for an undetermined amount of time.
This was a violation of Technical Specification 3.7.2(b),
and is reportable to the NRC per the requirements of 10 CFR 50.73(a)(2)(1). The fuse block was reinstalled at 1540. A station modification to be completed will add computer alarms for loss of load shed control power.
It appears the fuse block was manually pulled by an unknown person at some time since October 1983 when it was last verified to be in, place. This is the basis for classifying this incident as unknown.
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.a M,Nac s.,-assaw nn Description of Occurrence: On January 5, 1984 at 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> with Unit 3 at 100% FP, while examining breaker 3TE #13 in conjunction with a non-associated station modifica-tion, it was discovered that the 3TE switchgear load shed source B fuse block was disengaged. The appropriate personnel were notified and the fuse block was reinstalled at 1540.
The other Unit 3 load shed fuse blocks were checked and no other fuse blocks were found to be disengaged. The 3TE load shed source B fuse block is located inside breaker cabinet 3TE #13. The 3TE switchgear is comprised of fifteen 4160V breakers and is located on the ground floor of the turbine building.
Since breaker 3TE #13 is a spare, there is no load requirement for a component associated with it.
This source B fuse block provides power to only load shed relay 3ELS2. This relay is one of the two relays that can trip eight non-essential components during a load shed actuation.
A load shed situation causes non-essential loads on the 4160V switchgear to be tripped so that the transformer supplying power to the 4160V Main Feeder Buses will not be overloaded.
Cause of Occurrence:
The length of time that the breaker 3TE #13 load shed source B fuse block was not installed is indeterminable since there is no alarm associated with the disengaging of it.
However, there is a plastic red tag permanently mounted beside the fuse block stating "3TE Load Shed Source B - DO NOT REMOVE".
This tag and other similar tags were permanently mounted beside this fuse block and all other load shed fuse blocks to inform personnel of their importance. These tags were installed July 15, 1983 as a result of an incident on Unit 1.
In late June 1983 while performing a PM on breaker ITC #2, load shed source A fuse block had been inadvertently pulled. Waen the importance of the fuse block was discovered, it was replaced and temporary white tags were installed on all similar fuse blocks on all three units until permanent red tags could be made and installed. As the tags were installed, all fuse blocks were checked to verify installation. A follow-up inspection performed in October, 1983 verified the tags and fuse blocks were installed. A station modification had been issued earlier to install dedicated fuse blocks for each local load shed trip relay and add computer alarms for loss of load shed control power. Technical Specification 3.7.2(b) states that "the circuits or channels of any single functional unit of the EPSL may be inoperable for test or maintenance for periods not exceeding 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> provided that:
1.
The conditions of Table 3.7-1 for degraded operation are satisfied for that specific functional unic; and 2.
The conditions of Table 3.7-1 for normal operation are satisfied for all other functional units."
Table 3.7-1 allows only 1 of the 2 channels to be degraded for a period of up to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Part of channel B was not operative causing it to be degraded for an undetermined amount of time. Had this station modification been installed before this breaker 3TE
- 13 source B fuse block was disengaged, a notification of the removed fuse block would have prevented a Technical Specification 3.7.2(b) violation.
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Cause of Occurrence (cont'd):
It has not been determined when the fuse block was pulled. The last time installation was verified was October, 1983. There has been no work request issued for the breaker in the last two years.
Since the cabinet is not locked and the breaker is a spare, how and when the fuse block was removed is undeterminable at this time. This is the basis for classifying this incident an unknown.
Analysis of Occurrence: During the time the fuse block was out, Unit 3 did not experi-ence any electrical problem with either the auxiliary or startup transformers which would have required CT4 to be energized.
Therefore, Unit 3 never experienced a load shed situation requiring i:he non-essential components to trip. Also Load Shed Source C of the 3TE breakers had power available and would have energized the redundant ELS1 relay, thereby tripping the associated non-essential components. A load shed actuation and simultaneous failure of ELS1 relay would be necessary before ELS2 would be needed to trip the 3TE non-essential components.
Even if all these failures had occurred simultaneously, the amount of power the non-essential components plus the essential components would require is approximately 16 MVA. This power requirement is less than the capacity of CT3 or CT4 and would not create an overload situation.
Since CT4 could handle the essential loads as well as the affected non-essential loads of Unit 3, the health and safety of the public were not affected.
Corrective Action
The 3TE load shed source 3 fuse block was reinstalled at 1540 hours0.0178 days <br />0.428 hours <br />0.00255 weeks <br />5.8597e-4 months <br />.
The other Unit 3 load shed fuse blocks for sources A and B were checked to verify proper installation.
All personnel whose jobs involve working with the 4160V switchgear were questioned about the incident. The station modification to install dedicated fuse blocks for each local load shed trip relay and add computer alarms for loss of load shed control power will be completed. The load shed periedic tests will be reviewed and modified as necessary to ensure the load shed circuitry is adequately tested.
This report shall be reviewed with all personnel in the Transmission Department, Station Support Division - E1cetrical, Station Maintenance Support - Electrical, and Instrument and Electrical sections.
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February 6, 1984 Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region II
.101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30303 Re: Cconee Nuclear Station Docket No. 50-287
Dear Mr. O'Reilly:
Please find attached Reportable Occurrence Report R0-287/84-01. This report is submitted pursuant to 10 CFR 50.73(a)(2)(1), and describes an incident which is considered to be of no significance with respect to its effect on the health and safety of the public.
Very truly yours, fT
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Hal B. Tucker JCP/php-Attachment cc: Document Control Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20555 INPO Records Center Suite 1500 1100 Circle 75 Parkway Atlanta, Georgia 30339 Mr. J. C. Bryant NRC Resident Inspector Oconee Nuclear Station Mr. John F. Suermann Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 OFFICIAL COPY SUb 1 I