IR 05000269/1979037
| ML19309F655 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 01/18/1980 |
| From: | Martin R, Quick D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML19309F629 | List: |
| References | |
| 50-269-79-37, 50-270-79-34, 50-287-79-37, NUDOCS 8004300260 | |
| Download: ML19309F655 (6) | |
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NUCLEAR REGULATORY COMMISSION g-
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101 MARIETTA ST., N.W.. SulTE 3100
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ATLAN1 A, G EORGIA 30303 i
Report Nos. 50-269/79-37, 50-270/79-34 and 50-287/79-37
- Licensee: Duke Power Company 422 South Church Street Charlotte, North Carolina 28242 Facility: Oconee Nuclear Station Docket Nos. 50-269, 50-270 and 50-287 License Nos. DPR-38, DPR-47 and DPR-55
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Inspection at: Oconee Nuclear Station near Seneca, South Carolina Inspector:
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D. R. Quick
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Date' Signed Approved by:
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///8/' f0 R. Martin, Section Chief, RONS Branch Dste signed SUMMARY Inspection on November 11, 15, and 16, 1979 Areas Inspected This special, announced inspection involved 36 inspector-hours onsite in the areas of transient analysis and reportability requirements.
Results Of the two areas inspected, two items of noncompliance were found in one area (Infraction - Inadequate procedures to correct specific and foreseen potential f
malfunctions - Paragraph 5.C.2, and Infraction - Excessive Reactor Coolant System
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cooldown rate - Paragraph 5.a.); one apparent deviation was found in one area (Failure to notify NRC within one hour when Uni + 3 was in an unexpected operating condition - Paragraph 5.d.).
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DETAILS 1.
Persons Contacted
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Licensee Employees
- T. D. Curtis, Reactor Engineer
- R. T. Bond, Licensing and Projects Engineer
- T. B. Owen, Acting Station Manager
- R. A. Knoerr, I&E Support Engineer
- T. C. Matthers, Technical Specialist
- H.
S. Alexander, Clerk
- B. C. Moore, Unit 3 Operating Engineer
- R. J. Brackett, Senior QA Engineer J. N. Pope, Superintendent of Operations R. Gillespie, Electrical Engineer R. T. Scott, Assistant Shift Supervisor
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i Other licensee employees contacted included two technicians, six operators, and two office personnel.
NRC Resident Inspector
- F. Jape
- Attended exit interview
2.
Exit Interview
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The inspection scope and findings were summarized on November 16, 1979 with those persons indicated in Paragraph 1 above as follows:
i a.
An item of noncompliance was cited for the violation of cooldown rate 100*F/hr.) per Technical Specification, Infraction - Paragraph Sa.
l b.
Another item of noncompliance was cited for the failure to have an
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emergency procedure relative to loss of 3KI bus per Tech. Spec.
6.4.lc, Infraction-Paragraph 5.c.2.
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A deviation was cited for the failure to notify the NRC within one (1)
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hour pursuant to Station Directive 3.8.5, VII.A.3.
This was also a j
deviation from a commitment made relative to OIE Bulletin 79-05B -
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Pr.ragraph 5.d.
The da-nector also discussed the. sequence of events associated with the incideat, and the meeting held on November 15, 1979 between himself, representatives of DPC and Messrs. Israel, Thatcher, and Anderson.
Relative to this meeting, the inspector discussed the following licensee commitments:
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a.
Duke had modified the power transfer capability on the Unit 3 3KI bus to increase the probability of maintaining power to non-nuclear instru-mentation, b.
Duke had designated operators on Unit 1 & 2 to manually transfer power if the 3KI bus loses power and the static switch fails to transfer.
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c.
Duke will write an emergency procedure (with list of items on 3KI Panel Board) to cover loss of the 3KI bus prior to restarting Unit 3.
The licensee acknowledged the inspector's comments.
3.
Licensee Action on Previous Inspection Findings Not inspected.
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4.
Unresolved Items Unresolved items were not identified during this inspection.
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5.
Loss of Nonsafety-Related Reactor Coolant System Instrumentation During Operation The inspector investigated the cause and effects of this event to determine whether:
the licensee had properly identified the cause and implemented adequate corrective action to prevent recurrence; operators reacted properly during the event; administrative controls were adequate to place the unit in a safe shutdown condition; and finally to assure that there was no danger to the health and safety of the public during or following the event. The inspector accomplished this through:
discussions with licensee management, engineering, technical, and operating personnel; review of operating logs and records; review of transient monitor and computer printout data; review of applicable operating procedures; review of adequacy of equipment design; and finally review of procedure revision and equipment modification plans.
a.
Transient Sequence of Events At 3:15 p.m.
on November 10 with the reactor at 100 percent power, the main condensate pumps tripped, apparently as a result of a technician performing maintenance on the hotwell level control system.
This led to reduced feedwater flow to the steam generators, which resulted in a high reactor coolant system (RCS) pressure reactor trip and simultaneous turbine trip at 3:16:57 p.m.
At 3:17:15 p.m.,
the inverter power supply, nonsafety-related, feeding all power to the integrated control system (ICS) failed to transfer-automatica1,1y from the DC power source to the regulated AC power source. The inverter had tripped due to blown fus'es, resulting in loss of RCS indicators and recorders in the control room, except one widerange RCS pressure recorder.
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This condition existed for approximately three minutes, until an operator could reach the equipment room and switch the inverter manually. As a result of the power failure to the ICS, all valves controlled by that system assumed their respective fail positions.
This resulted in a cool down of the RCS to 1635 psi. and 530*F.
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operator, expecting this condition, started all makeup pumps and opened the associated high pressure injection valves to the RCS which limited the rate of RCS pressure reduction and associated reduction in pressurizer level. At 3:20:42 p.m., power was restored to the ICS.
However, due to the lack of adequate procedures to guide the operator, apparently steam bypass and/or feedwater valves were left in their respective fail (midway) positions and the RCS continued to cooldown tp approximately 420*F ov>r the next thirty minutes. This violated the maximum allowable Te rsical Specification cooldown rate of 100*F per hour. This is an I traction (287/79-37-01). However, the pres-surizer and steam generators did not go dry, and at least 79*F subcooling was maintained during this event. Normal, hot shutdown conditions were restored in the RCS at approximately 6:15p.m.
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b.
Cause of the event The cause of this event must be broken into two categories-personnel error and equipment malfunction, since each contributed in the following manner to the progression of the event:
(1) Personnel Error
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The licensee found the cause of the initiation of the transient itself to be due to a maintenance technician disturbing hotwell pump trip circuitry while performing maintenance on the hotwell level control system.
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(2) Equipment Malfunction The licenroe determined that the static switch associated with the KI inverter failed to transfer from the DC to the AC power y
source due to blown fuses within the KI inverter. However, the cause of the blown fuses, or the reason for the KI inverter attempting to switch to the alternate power source could not be determined. The licensee believes the cause to be a power surge on the power supply as a result of load switching or load demand changes associated with the reactor trip.
Inverter testing following fuse replacement.showed the inverter to be functioning normally and the switching problem could not be reproduced.
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c.
Identified Event Associated Problems t,.
(1) Inadequate Inverter Switching Desigd The NRC determined that, since the KI inverter supplies all power to the integrated control system as well as the majority of the
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control board instrumentation, it was necessary to upgrade the reliability of this inverter. As a result of this concern the licensee installed a redundant automatic transfer switch in parallel with the static transfer switch associated with che KI inverter. The licensee also relocated some key instrumentation
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onto another power supply to insure that adequate instrumentation
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would be available to allow the operator to place the plant in a
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safe shutdown condition if a similar event should occur. The licensee has committed a dedicated man to manus 11y transfer the KI inverter to the alternate power sources if necessary, on units one and two until the same modifications can be made on those units during their next scheduled shutdown. This is identified as a followup item (269/79-37-01 and IFI 270/79-34-01).
e (2) Inadequate Procedures The inspector determined that adequate emergency procedures did not exist to properly guide the operator through this event.
Alarm procedures did exist for loss of power to the ICS, however, there were errors in these procedures related to effect on equip-ment and they did not provide guidance to place the plant in a safe shutdown condition. The licensee committed to development of adequate emergency procedures for all three units, for loss of the KI power supply. This is an Infraction (287/79-37-02).
(3) Control and Instrumentation Availability The NRC determined that an inadequate amount of equipment control and instrumentation was available to the operator during this event. The licensee took action to relocate some key instrumenta-
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tion onto other power supplies and committed to evaluate the possibility of relocation of other control and instrumentation functions in the future. This is designated as a followup item (269/79-37-02, 270/79-34-02, and 287/79-37-03).
d.
Reportability Item 6 of IE Bulletin 79-05B, dated April 21, 1979, required that the licensee review prompt reporting procedures for NRC notification to assure that NRC is notified within one hour of the time the reactor is not in a controlled or expected condition of operation. Further, at that time an open continuous communication channel shall be established and maintained with NRC.
The licensee response to IE Bulletin 79-05B indicated that the following actions were taken to assure compliance with the Bulletin requirements:
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The Oconee Nuclear Station Emergency Plad (Station Directive 3.8.5)
includes prompt reporting procedures for NRC notification of serious events. The section of the Emergency Plan pertaining to reports and notifications has been revised to include the following statement
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under those events requiring immediate cotification of the Nuclear Regulatory Commission, Office of Inspection and Enforcement, Region II:
"Any situation whereby the reactor is not in a controlled or expected condition of operation. A situation such as this could be defined as
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any unscheduled event involving the reactor which can not be controlled or stabilized by use of normal operating procedures.
Note:
In a situation whereby the reactor is not in a controlled or expected condition, the NRC shall be notified no later than one (1)
hour following determination of the uncontrolled or unexpected condition. Upon notification, an open, continuous communications channel shall be establisned and maintained from the station to the NRC."
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To provide additional assurance that the NRC is promptly notified, Station Directive 3.1.5 Notification of Station Management) has been revised to include the following event which will require prompt
notification of the Station Manager:
Unscheduled event involving the reactor which cannot be controlled or stabilized by use of normal operating procedures.
Contrary to the above, at 3:15 p.m.
on November 10, 1979, Oconee Unit 3 experienced a transient during which, the loss of the KI Inverter
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resulted in the unit being in an unexpected condition of operation, and the NRC was not notified until app: )ximately 8:30 p.m.
on the
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same date.
This is a Deviation (287/79-37-04).
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