ML20062E506

Ro:On 820720,reactor Recirculation Jet Pumps Appeared Not to Meet Tech Spec Flow Balance Requirements.Event Determined Not Reportable,Since Event Constitutes Erroneous Test Criteria,Not Equipment Failure

ML20062E506
Person / Time
Site:	Duane Arnold
Issue date:	08/02/1982
From:	Mineck D IES UTILITIES INC., (FORMERLY IOWA ELECTRIC LIGHT
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
DAEC-82-513, NUDOCS 8208100128
Download: ML20062E506 (2)

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Iowa Electric Light and Power Company August 2, 1982 DAEC 513 Mr. James G. Keppler Regional Administrator Region III U. S. Nuclear Regulatory Conunission 799 Roosevelt Road Glen Ellyn, IL 60137

Subject:

Change in Reportability Status of July 20, 1982 Prompt Notification

Reference:

DAEC 82-499 D. Mineck to J. Keppler Prompt Notification of a Reportable Occurrence, dtd July 20, 1982 File: A-118a, TE-2, TE-3

Dear Mr. Keppler:

On July 20, 1982, the enclosed prompt notification letter was telecopied '

to your office. During startup surveillance testing, the reactor '

recirculation jet pumps appeared not to meet Technical Specification flow balance requirements. Conservatively, the jet pumps were declared inoperable and a 24-hour limiting condition for operation (LCO) was entered in accordance with Technical Specification 3.6.E.1. Upon further investigation, it was found that the limit switch for the "A" M/G set (1G-201A) had drifted low enough to cause a 15 percent flow imbalance when compared to the "B" M/G set (1G-201B) running at the correct minimum speed. The "A" limit switch was adjusted and the jet pumps met flow balance requirements. The LCO was cancelled after 2.25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />. This event was then determined to be not reportable. This letter contains the justification for that determination.

During startup from a cold shutdown condition, surveillance testing indicated that the reactor recirculation jet pumps did not meet Technical Specification flow balance requirements. Technical Specification 4.6.E.1.a requires that during operation or startup from a cold shutdown condition the two recirculation loops have a flow imbalance of less than 15 percent with the recirculation pumps operated at identical speeds. The surveillance procedure is used to identify leakage in the recirculation system. The test ensures that the jet pump integrity is not compromised and therefore water level would be maintained to two-thirds core height during and after a loss-of-coolant accident.

Due to the zero power level of the reactor at the time of the test, the pumps were being operated at the?r minimum speed. The minimum recirculation pump speed is set be the minimon speed of the recirculation motor-generator (M/G) set. The minimum M/G set speed is controlled by the 20 percent runback limit switch on the M/G set duel limiter, and cannot be adjusted when 8200100128 820802 PDR ADOCK 05000331 Y bg S PDR i center in Ikm ass cedar Itapids, somu 52406

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4 bguk ( k98{eppler Page 2 feedwater flow is less than or equal to 20 percent and the M/G set is running. The minimum speed set by the adjustment of the limit switch is the running speed of the M/G set whenever the feedwater flow is less than 20 percent. Below this level of flow, the water in the downcomer region of the reactor is at saturation conditions and the pressure changes associated with jet pump operation can theoretically cause the water travelling through the jet pump to change to steam. This steam formation can result in jet pump cavitation. Feedwater flow of greater than 20 percent provides a subcooling margin sufficient to avoid jet pump cavitation. In order to avoid cavitation at low power, the recirculation pumps are required to operate no faster than the minimum speed when feedwater flow is less than 20 percent.

At the time of the surveillance test, the limit switch for the "A" M/G set (1G-201A) had drifted low enou when compared to the "B" M/G set (gh to cause a 15 percent flow imbalance 1G-201B) runnin speed. The plant was brought to a condition where the minimum M/G set speed for 1G-201A could be adjusted. The minimum speed of 1G-201A was set to match that of 1G-201B, and subsequent surveillance testing indicated that the jet pumps were and had been operable. The LCO was cancelled 2.25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> after its initiation.

With the jet pump flow balance proven for identical recirculation pump speeds, the requirements of Technical Specification 4.6.E.1.a were met. The drif ting of the limit switch was in the conservative direction. The lower Jet pump flow would decrease the magnitude of the pressure changes of the water going through the jet pump and therefore provide an additional margin of protection from jet pump cavitation. This event is not one of the tested equipment failing, but one of the test criteria not being met. For these reasons, it has been determined that this event is not reportable.

If there are any questions concerning this event or the interpretation thereof, please advise.

Very truly yours,

h. M L' Daniel L. Mineck Plant Superintendent - Nuclear DLM/KLH/pl cc: B. York t

J. Vinquist D. Wilson R. Hannen S. Brown NRC Resident inspector

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