ML20100F716

Submits 120-day Response to NRC Bulletin 95-002, Unexpected Clogging of RHR Pump Strainer While Operating in Suppression Pool Cooling Mode, as Committed in 951116 Response

ML20100F716
Person / Time
Site:	Monticello
Issue date:	02/14/1996
From:	Hill W NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-95-002, IEB-95-2, NUDOCS 9602220058
Download: ML20100F716 (2)

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Northem States Power Company Monticello Nuclear Generating Plant 2807 West Hwy 75 Monticello, Minnesota 55362 9637 February 14,1996 Bulletin 95-02 US Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Response to Bulletin 95-02 Commitment To Run ECCS Pumps For Six Hours And Observe inlet Pressure For indication of ECCS Strainer Pluaalna in our November 16,1995 response to the 30 day report request of Bulletin 95-02, " Unexpected Clogging Of A Residual Heat Removal (RHR) Pump Strainer While Operating in Suppression Pool Cooling Mode" we made the folluwing commitment:

" Prior to February 14,1996 (i.e. within 120 days of the Bulletin date) one or more ECCS pumps, as deemed appropriate, will be run for approximately 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and pump inlet pressure will be observed to see if there is any drop due to strainer plugging. Final results will be reported within 10 days of completion of all confirmatory testing.

• The purpose of this letter is to provide the results for this commitment.

On February 9,1996, four RHR pumps were run for six hours in a suppression pool cooling mode configuration (recirculation of suppresolon pool water with no cooling). The inlet pressure taps to two RHR pumps were provided i

with more accurate instruments and pressures recorded at regular intervals throughout the test. Additionally, since a common ring header provides suction for all the ECCS pumps, the inlet pressures to the Core Spray pumps were also recorded at regular intervals to provide additional data. The results of this test showed no degradation of inlet pressure to either of the RHR pumps (see attached plot) or the Core Spray pumps which indicates that no plugging of the ECCS suction strainers occurred. Adequate cleanliness of the suppression chamber was demonstrated and operability of all pumps which draw suction from the suppression pool when performing their safety functions was confirmed.

This letter serves to fulfill the above commitment and no additional commitments are made by this letter.

Please contact Mel Opstad, Sr Licensing Engineer, at (612) 295-1653 if you require further information.

flbN William J Hill Plant Manager Monticello Nuclear Generating Plant cc:

Regional Administrator-lli, NRC NRR Project Manager, NRC Sr Resident inspector, NRC State d Minnesota, Attn: Kris Sanda Attachment 9602220058 960214 PDR ADOCK 05000263 G

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