NG-94-1150, Part 21 Rept Re Defect Identified W/ C RHR Pump Motor from Daec.Pump Performance Degraded.Installed New Shaft Rotating Element,Wear Ring & Hydrostatic Bearing & Replaced Pump Mechanical Seal & Motor Thrust

Part 21 Rept Re Defect Identified W/ C RHR Pump Motor from Daec.Pump Performance Degraded.Installed New Shaft Rotating Element,Wear Ring & Hydrostatic Bearing & Replaced Pump Mechanical Seal & Motor Thrust

ML20065D279
Person / Time
Site:	Duane Arnold
Issue date:	03/28/1994
From:	Franz J AFFILIATION NOT ASSIGNED
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-PT21-94 NG-94-1150, NUDOCS 9404070029
Download: ML20065D279 (2)

Text

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4

, A UTILITIES INC.

March 28,1994 NG-94-1150 Document Contrul Desk U.S. Nuclear Regulatory Commission Washington, D. C. 20555

Subject:

Written Notification of 10 CFR Part 21 Report Referenec: NG#4-0877 dated March 1,1994

Dear Sir:

This letter provides additional information concerning a defect in accordance with 10 CFR Part 21.

This is our report pursuant to Section 21.21(i)(3)(ii) of a defect that was identified with the "C" residual heat removal (R11R) pump motor and is a follow-up to the initial notification faxed to you on March 1,1994 (reference).

In 1988, General Electric Nuclear Energy (GE-NE) overhauled four RHR pump motors and two core spmy pump motors from the Duane Arnold Energy Center (DAEC). The applicable purchase order specified that 10 CFR Part 21 applied. On December 15,1993, the "C" RHR pump failed to meet its reo uired discharge pressure during the performance of a quarterly surveillance test. It was subsequent y discovered on or about January 7,1994, that the "C" RHR pump motor shaft nut washer tab was not bent to engage the nut. This allowed the nut to loosen with pump vibration and eventually permitted the shaft to lower until the pump impeller was running between 0.002 and 0.004 inches atxwe the pump case versus a normal clearance of about 0.160 inches. This resulted in a degradation of pump performance by about 5'7c as compared to the pre-operational testing curves. Consequently, a new shaft rotating element, wear ring and hydrostatic bearing were installed due to excessive pump wear and a bent shaft. In addition, the pump mechanical scal and motor thrust and lower radial bearings were replaced.

The pump motors were overhauled at GE's Memphis, Tennessee facility in 1988. It is believed that Genem! Electric failed to bend the k)cking washer at that time as was required by shop procedures. We have verified that the kicking washer tabs are bent on the remaining RIIR and core spray pump motors. Also, other checks were performed to verify that pump clearances are within specifications.

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U'.S. Nuclear Regulatory Commission NG-94-1150 -

March 28,1994 Page Two Our March 1, lW4 notification stated the potential significant safety hazard associated with this defect (h>cking tab not being bent) was the possible inability of the pump to function as described -

in the Plant Safety Analysis. The DAEC has since been informed by GE that it performed a plant unique analysis which shows the limiting condition created by this defect is the failure of Division _-

11 of the plant 125 VDC System in combination with the failure of the "C" RHR pump, which would result in a peak cladding temperature (PCT) as bounded by the existing Licensmg PCF of 1,570 degrees F. Therefore, the DAEC no longer considers this issue reportable under 10 CFR Part 21.

On the basis of this information, the DAEC has also concluded that no significant safety hamrd exists and by this letter, is notifying you of our closure. If you have further questions regarding this matter, please contact me or either of the following individuals.

George Carr -- (319) 851-7444 ' ,

Jeffrey Thorsteinson - (319) 851-7215 Sincerely, Il John F. Frane.

Vice President- Nuclear .

JFF/LS/ch i