05000409/LER-1981-010, Forwards LER 81-010/01T-0.Detailed Event Analysis Submitted

Forwards LER 81-010/01T-0.Detailed Event Analysis Submitted

ML20031F116
Person / Time
Site:	La Crosse File:Dairyland Power Cooperative icon.png
Issue date:	10/07/1981
From:	Linder F DAIRYLAND POWER COOPERATIVE
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20031F118	List: 05000409/LER-1981-010, Forwards LER 81-010/01T-0.Detailed Event Analysis Submitted 05000409/LER-1981-010-01, /01T-0:on 810923,during Normal Operation Mechanical Interlock Preventing Simultaneous Opening of Both Doors of Containment Bldg Personnel Airlock Failed.Caused by Worn or Misadjusted Actuating Mechanism.Drawings Encl
References
LAC-7851, NUDOCS 8110190206
Download: ML20031F116 (3)

LER-1981-010, Forwards LER 81-010/01T-0.Detailed Event Analysis Submitted

Event date:
Report date:
4091981010R00 - NRC Website

text

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O DA/RYLAND h

[k COOPERA7/VE PO BOX 817 2615 EAST AV SOUTH LA CROSSE, WISCONSN 54601 (608) 788 4 000 October 7, 1981 l

In reply, please refer to LAC-7851 DOCKET 9

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Mr. James G.

Keppler, Director p

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S. Nuclear Regulatory Commission j

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Directorate of Regulatory Operations g_

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Glen Ellyn, Illinois 60137 l

SUBJECT:

DAIRYLAND POWER COOPERATIVE U

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LA CROSSE BOILING WATER REACTOR (LACBWR) xg']-]}

f PROVISIONAL OPERATING LICENSE NO. DPR-45 l

REPORTABLE OCCURRENCE NO. 81-10

References:

(1)

LACBWR Technical Specifications, Section 6.9.1.8.c (2)

DPC Letter, Linder to Keppler, LAC-7826, dated September 24, 1981.

Dear Mr. Keppler:

In accordance with Reference 1, this report constitutes the required followup report to the event originally described in Reference 2 which occurred September 23, 1981.

The subject event concerned a malfunction of the Containment Building personnel airlock interlock mechanisms which permitted both the inner and outer doors to be in the open position for a period of time estimated to be less than half a minute, while the plant was in Operating Condition 1.

An extensive investigation o'. the circumstances surrounding this event was conducted.

The investigation determined there was defin-itely no intentional misoreration or misadjustment of the airlock interlock.

Please refer to the following drawings for the dis-cussion of circumstances.

t CB&I - General Mechanic, Drawing No. 35, Revision 1 Arrangement 7 x 5-1/2 Personnel Lock Reactor Containment Vessel gp($lfq La Crosse, Wisconsin s

CB&I - Door Actuating Assembly Details, Drawing No. 41, Revision 2 p l 7 x 5-1/2 Personnel Lock Reactor Containment Vessel La Crosse, Wisconsin 8110190206 811007

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00 1 '5 W PDR ADOCK 05000409 IS PDR

Mr. James G.

Keppler, Director LAC-7851 U. S. Nuclear Regulatory Commission October 7, 1981 The door actuating mechanism parts shown on Drawing No. 35, are for the exterior door, but the interior door actuating mechanism parts are identical.

When the door is in the open position, a cam roller on Part No. 43-5 is in the depression in Part No. 43-3.

When the door is in the closed and sealed position, the roller is on the outer rim of Part No. 43-3.

When the index wheel has completed its travel to the sealed position during the closing cycle, the mechanical interlock assumes that the door is in the sealed position and so permits the other door to be opened.

Troubleshooting determined that if steady hand pressure was applied to turn the handwheel while the interior door was being closed and at a position approximately one foot from the frame, the roller could skip to the outer rim of Part No. 43-3, thus allowing continued handwheel operation that positioned the locking bars and simultaneously neutralized (as designed) the mechanical interlock though the door was actually outside of the locking bars and open.

Following the initial investigation, mechanical adjustments were made to the adjustable door link subassembly- (41-11) which governs the angular rotation and the relative engagement position of the roller to the index plate at the end of the swing for the door.

Subsequent testing indicated the incident could not be duplicated and the system's mechanisms were determined to be operable at approximately 1345 the same day.

From the investigation, it was determined both personnel airlock doors were opened simultaneously once or possibly twice, depending on whether the failure occurred as a result of an individual entering or exiting the Containment Building.

It cannot be definitely concluded whether a second event actually occurred.

Further investigation of the mechanical problem determined that it was due to either wear, adjustment of the gears or link during previous maintenance, or a combination of all three.

The interlock is tested after maintenance is performed on.the airlock, but since this particular phenomena had never been envisioned, previous tests did not consider the potential for an occurrence of this nature.

Past adjustments and tests have been performed based on the best knowledge derived from experience and the manufacturer's manual.

Mr. James G. Keppler, Director LAC-7851 U. S. Nuclear Regulatory Commission October 7, 1981 A semi-annual surveillance program and a formal post-maintenance test procedure will be developed to incorporate the information gained from this event.

The procedure for operation of the airlock doors is being revised to specify the best method of operating the doors without applying abnormal force to the actuating mechanism in order to minimize wear.

A copy of the revised procedure will be distributed to all departments.

The application of indicating lights for door status is being considered.

In addition, the airlock door manufacturer, Chicago Bridge and Iron, has been contacted and technical assistance is being arranged in order to check that the operating mechanisms are in proper alignment, and to better ensure that there is not a reoccurrence of this breach of containment event.

If further problems are discovered by the manufacturer's representative, a supplemental report will be submitted.

A Licensee Event Report (Reference:

Appendix A, Regulatory Guide 1.16, Revision 4) is enclosed.

An extension until October 12 was granted to L. S. Goodman by M. Branch, NRC Resident Inspector, on October 7, 1981.

If you have any questions, pleast contact us.

Very truly yours, DAIRYLAND POWER COOPERATIVE

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Frank Linder, General Manager FL:LSG:af Enclosure Director, Office of Inspection and Enforcement (30) cc:

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 \\ ~.