ML20042F359

Provides Suppl Response to NRC Bulletin 88-004, Potential Safety-Related Pump Loss. Precaution Added to Operating Procedures Which Allows ECCS Pump to Be Secured & Restarted as Necessary to Preclude Running Pumps at Min Flow

ML20042F359
Person / Time
Site:	LaSalle
Issue date:	04/29/1990
From:	Morgan W COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-88-004, IEB-88-4, NUDOCS 9005080226
Download: ML20042F359 (3)

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April 29, 1990 U.S. Nuclear Regulatory Commission j

ATTN: Document Control Desk Washington, DC 20555 1

Subject:

LaSalle County Station Units 1 L 2 Supplemental' Response to NRC Bulletin 88-04

" Potential Sa#ety-Related Pump Loss" NRC Docket Nc n. 50-373 and-50-374

References:

(a) NRC Bulletin No. 88-04 dated May 5, 1988 (b) W.E.. Morgan letter to.U.S. NRC dated July _11, 1988.

Dear Sir:

Reference (a) requested that licensees inw atigate and correct as applicable two miniflow design concerns. The first concern involves the potential for the dead-heading of one or more pumps in safety-related systems that have a miniflow line common to two or more pumps or_other piping i

configurations that do not preclude pump-to-pump interaction during miniflow operation. A second concern is whether or not the-installed miniflow capacity is adequate for even a single. pump in operation.

In Reference (b), when addressing the adequacy of the minimum flow bypass lines for safety-related centrifugal pumps at LaSalle County Station, Commonwealth Edison. indicated that further vendor-input and engineering evaluation would be necessary to verify that-current miniflow rates are i

- sufficient to ensure that there will be no pump damage from low flow operation.

Ingersoll-Rand (IR) the pump manufacturer of the High Pressure Core l-Spray (HPOS), Low Pressure Core Spray (LPCS), and Residual Heat Removal (RHR) l pumps at LaSalle Station, developed and provided Commonwealth Ediaon-(CECO) l with an equation to predict remaining pump life as a function of previous pump operating history. Within this equation there were five " constants" with values assigned by IR for the LaSalle HPCS, LPCS, and RHR pumps.- Using this information, Conconwealth Edisons Engineering Department estimated the equivalent annual service hours for each pump.

It is CECO's opinion that the IR equation represents a very simplified model and that the estimated service f

hours from the equation are conservative.

Ingersoll-Rand concluded that-predicting remaining pump life is not an exact criteria, and that the actual service interval must be established from actual running experience.versus accumulated operating hours, and should depend primarily on the performance characteristics (vibration, temperatures, leakage rates) being monitored.

It is. Edison's prartice to perform service on pumps based upon detected degradation from nurveillance testing and not upon accumulated pump run time.

9005080226 900429

{DR ADOCK 05000373

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l U.S..Nhclear Regulatory Commission April 29, 1990 LaSalle Station conducts quarterly surveillance tests on its HPCS, LPCS, and RHR pumps to satisfy ASME Section XI pump performance requirements and to ensure the operational readiness of the pumps.. Test data is trended and evaluated to detect any pump degradation and to determine if pump maintenance is needed.

To this date, no noticeable pump degradation has-occurred and no adverse trends have been identified.

Ingersoll-Rand additionally recommended that LaSalle continue to use the minimum flow values originally supplied by General Electric Company.

Those values being HPCS-1000 gpm, LPCS-635 gpm, and RHR-550 gpm, which-LaSa11e's minimum flow lines are designed to provide.

IR based their acceptance of the GE specified minimum flow rates on the assumption that the pumps operate for only short durations at the minimum. flow rates.

IR considers short period operation to be pump operation of 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> or less.

Ingersoll-Rand provided CECO with recommended minimum continuous duty flow rates (MCF) oft HPCS-1500 gpm, LPCS-2150 gpm, and RHR-2150 gpm.

Ingersoll-Rand considers continuous operation.to be any pump operation i

exceeding a 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> duration in a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period.

At LaSalle Station each pump utilizes a minimum flow and a full flow recirculation line.

LaSalle tests each pump by running it on recirculation using the' full flow recirculation line.

The minimum flow line is used only during pump start-up, between the time the pump is started and until it reaches normal operating speed and discharge pressure.. After the pump speed and discharge pressure have stabilized, a valve in the full flow line is opened to allow full flow thru the pump.

The estimated time the pump spends on minimum flow is less than one minute during each test.. Therefore, the Ingersoll-Rand specified MCF flow rates for LaSalle are only useful as input into IR's service life equation.

A precaution has been added, as a result of the Bulletin, to LaSalle Station's operating procedures which allows an ECCS pump to be secured and restarted as necessary to preclude running the pumps unnecessarily long at minimum flow.

CECO believes that 14Salle's current operating practices and performance monitoring surveillances meet the intent of Ingersoll-Rand's recommendations and assures the acceptable perfonnance of the HPCS, LPCS, and RHR pumps.

Based upon the responses from the pump suppliers coupled with the review of pump vibration data previously ' discussed in Reference (b) assurance is provided that operation of the LaSalle County pumps at low flow conditions will not cause pump damage.

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U.S. Nuc1= r Rcgulstery Conunission April 29, 1990 i

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i Please address any questions that-you or your staff may have concerning this response to this office.

.i Respectfully, Ol@Q 1

W B. Morgan-Nuclear Licedsing Administrator r

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A.B. Davis - RIII Robert.Pulsifer - Project Manager - NRR-Senior Resident Inspector - LaSalle i

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