05000409/LER-1981-008, Forwards LER 81-008/01T-0.Detailed Event Analysis Submitted

Forwards LER 81-008/01T-0.Detailed Event Analysis Submitted

ML20010D035
Person / Time
Site:	La Crosse File:Dairyland Power Cooperative icon.png
Issue date:	08/11/1981
From:	Linder F DAIRYLAND POWER COOPERATIVE
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20010D037	List: 05000409/LER-1981-008, Forwards LER 81-008/01T-0.Detailed Event Analysis Submitted 05000409/LER-1981-008-01, /01T-0:on 810729,main Steam Bypass Valve Did Not Open During Momentary Pressure Spikes Approx 20 Psi Above Nominal Reactor Pressure.Caused by Decrease in Pressure Prior to Valve Opening Due to Short Duration & Spikes
References
LAC-7741, NUDOCS 8108210394
Download: ML20010D035 (2)

LER-1981-008, Forwards LER 81-008/01T-0.Detailed Event Analysis Submitted

Event date:
Report date:
4091981008R00 - NRC Website

text

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[k COOPERAT/VE Po BOX 817

• 2615 EAST AV SOUTH. LA CROSSE. WISCONSIN 54601 1608) 768 4 000 August 11, 1981 In reply, please refer to LAC-7741 DCCKET NO. 50-409 Mr. James G.

Kcppler, Regional Director

% '9N U. S. Nuclear Regulatory Commission

$1 Directorate of Regulatory Operations Region III p

799 Roosevelt Road

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Glen Ellyn, Illinois 60137 4 l,/ ; ? 01981 r.

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SUBJECT:

DAIRYLAND POWER COOPERATIVE (DPC) t7J N[g* rom.en

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LA CROSSE BOILING WATER REACTOR (LACBWR)

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PROVISIONAL OPEPATING LICENSE NO. DPR-45 REPORTABLE OCCURRENCE NO. 81-08 s

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REFERENCES:

(1)

DPC Letter, Linder to Keppler, LAC-7694, dated July 30, 1981.

(2)

LACBWR Technical Specifications, Section 4.2.5.7.

(3)

DPC Letter, LAC-4523, Supplement No.

3, Part II of DPC's Reload Application Operation with Exxon Fuel, dated February 25, 1977.

Dear Mr. Keppler:

This letter constitutes the written follow-up to the event initially reported to you in Reference 1.

Reference 2 requires that the main steam bypass valve control be set to begin opening the bypass valve at an indicated pressure correspond-ing to a turbine inlet pressure not more than 15 psi above its nominal value, except during plant startup and shutdown.

During operation on July 29, 1981, it was noticed the main steam bypass valve did not open during momentary pressure spikes approximately 20 psi above nominal reactor pressure.

The wide range bypass valve controller set-point was. lowered to approximately 20 psi above nominal pressure.

The narrow range bypass valve controller set-point was lowered until the bypass valve opened.

It was determined the narrow range bypass valve controller was opening the bypass valve.approximately 4 psi higher than l

normal.

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8108210394 810811 PDR ADOCK 05000409' PDR-AUG j 4 m 1

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Mr. James G.

Keppler, Regional Director LAC-7741 U.

S. Nuclear Regulatory Commission August 11, 1981 Plant management promptly directed that the narrow range bypass valve controller set-point be set at 10 psi above nominal reactor pressure to compensate for the 4 psi overshoot.

Administrative controls were instituted to maintain the set-point at no greater than 10 psi above nominal reactor pressure.

The wide range bypass valve controller set-point was left at 20 psi above nominal reacter pressure to serve as backup to the narrow range controller.

On August 3, 1981, during a plant shutdown, the narrow range main steam bypass valve narrow range controller was tested and calibrated.

The controller was found to be operating properly.

On August 4,

1981, a functional test was conducted which demonstrated the controller opened the bypass valve at the correct pressure.

The controller set-point was returned to its normal value of not greater than 15 psi above nominal system pressure.

It is postulated that due to the short duratlon of the pressure spikes on July 29, 1981, that the spikes were only slightly above the 15 psi se t-poin t, and that the reset time of the controller actually exceeded the small spikes' durations, the controller was receiving the decreas-ing pressure signal prior to valve opening.

Therefore, the valve did not open at the correct indicated deviation on the controller.

Accident analyses (Reference 3) do exist which assume the bypass valve does not open during a transient which requires its operation.

The minimum critical power ratio for a turbine trip without the bypass valve opening was calculated to be 1.49, which is greater than the 1.32 minimum allowable.

This scenario is much more conservative.

If there are any questions concerning this report, please contact us.

Very truly yours, DAIRYLAND POWER COOPERATIVE haa:lb 2th G

Frank Linder, General Manager FL:LSG:eme cc:

Director, Office of Inspection and Enforcemer.t (30)

U.

S.

Nuclear Regulatory Commission Washington, D.

C.

20555 Director, Office of Management Information and Program Control (3)

U.

S.

Nuclear Regulatory Commission Washington, D.

C.

20555 NRC Resident Inspectors