05000409/LER-1981-002, Forwards LER 81-002/02L-0.Detailed Event Analysis Submitted

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Forwards LER 81-002/02L-0.Detailed Event Analysis Submitted
ML20004F040
Person / Time
Site: La Crosse File:Dairyland Power Cooperative icon.png
Issue date: 02/25/1981
From: Linder F
DAIRYLAND POWER COOPERATIVE
To: James Keppler
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20004F041 List:
References
LAC-7382, NUDOCS 8106160433
Download: ML20004F040 (4)
v • d • e


LER-1981-002, Forwards LER 81-002/02L-0.Detailed Event Analysis Submitted
Event date:
Report date:
4091981002R00 - NRC Website
v • d • e

text

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E wisconsis s4so, 1608, 786 4 000 February 25, 1981 In reply, please refer to LAC-7382 DOCKET NO. 50-409 Mr. James G. Keppler Regional Director

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U. S. Nuclear Regulatory Commission 7'

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Directorate of Regulatory Operations

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Region III N

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SUBJECT:

DAIRYLAND POWER COOPERATIVE h,,

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LA CROSSE BOILING WATER REACTOR (LACBWR) o',

- Id PROVISIONAL OPERATING LICENSE NO. DPR-45

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REPORTABLE OCCURRENCE NO. 81-02 M[*.0 M

References:

(1)

LACBWR Technical e ifications, Section 3. 9.2.b. (2)

(2)

LACBWR Technical Specifications, Section 4.2.3.1.1 (3)

LACBWR Technical Specifications, Section 4.2.3.2.1 Dear Mr. Kepp.*

In accordance with Reference 1, this report is notification of operation in a degraded mode permitted by a limiting condition l

for operation.

Reference (2) requires that the physically independent circuit between the off-site transmission network and the onsite power distribution system and the electrical feeds from 2400V bus lA l

and 1B be operable during Operating Condition 1.

Reference (3) requires that specified AC electrical buses be operable and energized from sources of power othr:r than a diesel generator, but aligned to an operable diesel generator.

On February 1, 1981, at 1134, at 28% Reactor Rated Thermal Power, the physically independent circuit between the off-site transmis-sion network and the onsite power distribution system was interrupted when the switchyard operator opened manual Disconnect Switch 25NA.t, which disconnected the reserve auxiliary transformer from the 69KV 0y transmission line.

(See attached sketch).

The emergency diesel i(0 l

generators started automatically and supplied the essential buses gjI l

The reactor shut down automatically.

All systems functioned prop-g erly.

Off-site power was restored within 14 minutes.

l W 2M 810 G 16 0 p

Mr. James G. Keppler, Regional Director LAC-7382 U. S. Nuclear Regulatory Commission February 25, 1981 The circumstances surrounding the incident are as follows:

At 1125 on February 1, the turbine operator closed switch 25NB1 to close oil circuit breaker (OCB) 25NB1 to synchronize the generator output with the DPC electrical grid.

In closing the switch, he used too much force, breaking the switch internal spring pin.

The switch was then reopened.

In reaching across the switch, a super-visor's shirt sleeve brushed against the switch handle.

Due to the broken spring pin, the slight pressure was enough to cause the 4

switch contacts to close, thus initiating a momentary closing action on OCB 25NB1, with the generator electrically out of phase with the DPC grid.

Therefore, it was decided to open the airbreak disconnect switch for 25NB1 as a precaution, to prevent inadvertent or self-closure of OCB 25NB1 and to allow repair.

The switchyard operator was given a switching order to open 25NA1, the air break disconneet to the main transformer.

Though the dis-

.. 3d correctly and the operator had performed connect switch is labe a visual check of the.abel and order, he incorrectly 'pened 25NA4, o

the air break disconnect to the reserve auxiliary transformer, which was supplying station power.

All subsequent automatic actions functioned and the Control Room Operators carried out the loss of off-site power procedure properly.

Disconnect awitch 25NA4 was re-closed after the oil circuit breaker 25NB4 was opened and the correct disconnect switch, 25NA1, was opened.

The actions of the switchyard operator were reviewed by plant ranage-l ment.

The operator was interviewed to determine the reason for the mis-switching.

The problems entountered with the Control Roor switch for OCB 25NB3 caused concern for that event and may have interfered with his concentration.

Whenever possible, outside switching orders will be executed in the presence of a second person to provide a double check.

Also, additignal practical training on the switchyard will be provided for all operators.

A Licensee Event Report (Reference:

Regulatory Guide 1.16, Revision 4) is enclosed.

If you have any questions, please centact us.

Very truly yours, DAIRYLAND POWE COOPERATIVE i

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Frank Linder, General Manager FL:LSG:af Enclosures !

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Mr. James G. Keppler, Regional Director LAC-7382 l

U. S. Nuclear Regulatory Comission February 25, 1981 cc:

Director, Office of Inspection and Enforcement (30)

U. S. Nuclear Regulatory Commission Washington, D. C.

20555 Director, Office of Management Information and (3)

Program Control U. S. Nuclear Regulatory Commission Washington, D. C.

20555 NRC Resident Inspectors l

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