ML20058K618

Ro:On 740405,cracked Studs on Recirculation Pumps Discovered & Ultrasonic Exam Revealed Internal Defects in All Remaining Studs on Recirculation Pump 12 & Nine of Ten Studs in Pump 11

ML20058K618
Person / Time
Site:	Monticello
Issue date:	04/15/1974
From:	Mayer L NORTHERN STATES POWER CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 9102120672
Download: ML20058K618 (2)

Text

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NORTHERN STATES POWER COMPANY M I N N E A F* O L.I S . M I N N E S CTA S5401 m" ~u April 15, 1974 .

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Mr. J F O' Leary . .

Directorate of Licensing  ; '$ d. i Office of Regulation  ;

U S Atomic Energy Com:nission A ',

Washington, DC 20545 I

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Dear Mr. O' Leary:

MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License .;o. DPR-22 Cracked Studs on Recirculation Pumps A condition occurred at the Monticello Nuclear Generating Plant wnich we are reporting to your office in accordance with Section u.7.3.1. Abnoreci Occurrence Reports, of Appendix A, Technical Specifications, of Provisional Operatinz License DPR-22.

On April 5, 1974, it was discovered that one of the ten stuffing box holddown cover studs on No. 12 recirculation pump had f ailed (see attached ficure ) .

Subsequent ultrasonic examination revealed significant internal defects in all of the remaining studs on No. 12 recirculation pump and in nine of the ten studs on Co. 11 recirculation pump.

Complete failure of all the studs on a recirculation pump could result in primary coolant leakage past the pump shaft seal into the drywell. It is noted that the pumn is capable of being shutdown and isolated in the event of significant leakage. This is the first time that failure ot' any recirc-ulation pump stuffing box holddown cover studs has been detected.

Investigation into the cause of the stud failures and possible correctice actions is continuing. Following completion of this investinction, a report on the final resolution of the problem vill be submitted.

Very truh yours, L 0 Mayer. PE Director of Muclear Support Services LCM /lh 9102120672 740415 CF ADOCK 05000263 .

ec: J G Keppler CF '

G Charnoff Minnesota Pollution Control Agency ,

Attn. E A Pryzina Attachment f

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