ML20138N332

Responds to 851023 Confirmatory Action Ltr Re Improper Response of Reactor Protective Sys.Investigation Discussed & Startup Testing Performed Under Cognizance of NRC Representatives

ML20138N332
Person / Time
Site:	La Crosse File:Dairyland Power Cooperative icon.png
Issue date:	10/23/1985
From:	Taylor J DAIRYLAND POWER COOPERATIVE
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
CAL, LAC-11211, NUDOCS 8511050153
Download: ML20138N332 (3)

Text

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_/ h [k COOPERA 7NE . e.o box 817 2615 EAST AV SOUTH . LA CROSSE. WISCONSIN _54601 (608) 788-4000

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October 23, 1985 In reply, please refer to LAC-ll211 DOCKET No. 50-409 Mr.~ James G. Keppler Regional Administrator U. S. Nuclear Regulatory Commission Region III 799 Hoosevelt Road Glen Ellyn, IL 60137

SUBJECT:

DAIRYLAND POWER COOPERATIVE LA CROSSE BOILING WATER REACTOR (LACBWR)

PROVISIONAL OPERATING LICENSE NO. DPR-45 RFSPONSE TO CONFIRMATORY ACTION LETTER

Reference:

(1) Letter, Keppler to Taylor, dated October 23, 1985

Dear Mr. Keppler:

You sent us a Confirmatory Action Letter regarding an apparent improper response of the reactor protective system (Reference 1). We have reviewed the items listed and our response follows.

NkC IM 1 Conduct a flwrough revicw to determine if a trip signal actually was received by the Reactor Protection Systen (RPS).

DPC RESPONSE A thorough review has been conducted. It has been concluded that a scram signal was not received. An alarm signal was received which gave one visual indication of a possible trip condition.

NRC IM 2 If such a signal was received, determine why the control rods failed to automatically insert.

DPC RESPONSE N/A PC4-4 NU$Nk S

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OCT 30 T85-

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Mr. James G. Keppler October 23, 1985 U. S. Nuclear Regulatory Commission LAC-Il211 Region III page 2 NIC JM 3 If such a trip signal was not received, deiermine why the annuncintor uns activated.

DpC RESPONSE Due to an apparent failure of an oscillator circuit on the trip stage of NI-6 that should have ensured that both the alcrm and trip relays actuated at the same time, the annunciator came in approx. 2% power before the trip signal actuated. A very slow increase in power to approx. 110% indicated on the 150 x 10-5% scale, in conjunction with a possible noise spike of a few percent activated the annunciator but not the trip. We were able to duplicate the separation between the annunciator und the trip relays many times, with the same results. This has been observed by the NRC Resident Inspector and the personnel sent from Region III.

Nhc IM 4 Determine what caused the signni that nuclear instrumentation observed and why nuclear instrument channel number 5 was not affected.

DPC RESPONSE At this power level (10-5%) there was a spread of 5%-10% between NI-5 and NI-6. The 0500 readings on 10/23/85 showed NI-5 to be at 56% and NI-6 to be 62% on the 150 x 10-5% scale. This spread would allow NI-6 to reach an actuation condition without NI-5 reaching an actuation point.

NIC JM S Msintain all affected equimt related to the Reactor Protection Systen in such a manner that ii can easily be kept or placed in the "as found" condition. Therefore, take no action which would destroy or cause to be last, (other than necessary to protect the health and safety of the public) any evidence which uvuld be needed to investigate or reconstruct this event.

DPC RESPONSE Although some minor adjustment was done on NI-6, it can be placed in the as-found condition. No further action will be taken on the drawer, pending NRC concurrence of the course of action deemed necessary.

NIC IM G Review operator octians tuken innediately foi1owing his recognition of ihe failure to trip and determine if these actions were in accordance with your procedurcs and policies (specifically, determine why the control rods were manually inserted rather than by inserting a manual trip signal.)

PC4-4 L

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Mr. James G. Keppler October 23, 1985 U. S.. Nuclear Regulatory Commission LAC-ll211 Region III page 3 DPC RESPONSE The operator's indication of. an npparent trip condition was annunciator D5-4, his power level indication was at 110%, which is well below the nominal scram point of 115%. He immediately reduced power to sub-critical by inserting #1 control rod. The A'IWS procedure allows either a manual scram or control rod insertion. (Ref: LACBWR Op. Manual Vol. I, Sec. 4.12.) This was accomplished.

-AQilC ITD( 7 A fonnul report of your findings und conclusiew= :;lil be submitted to the hgion III office within 30 dayn 7 DrG nssPON55 t

This letter constitutes the requested response.

M I71lipf B

.Ne further understand that startup will not occur until authorization to restart is obtained from the &gional Achrinistrator or his designee.

DPC RESPONSE

, The investigation has been discussed with and testing performed under the

.. cognizance of NRC representatives. Restart will await authorization by the Regional Administrator or his designee.

Very truly yours, DAIRYLAND POWER COOPERATIVE-James W. Taylor, General Manager FL:JDP:LWK:dh cc - Document Control-Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20555 NRC Resident Inspector '

J. Stang, NRC Project Manager PC4-4

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