ML20041D596

Second Interim Potential Significant Deficiency Rept Re Design of Min Charging Pump Flow Not Being Capable of Delivering Required Flow to Rcs.Adequate Flow Provided by safety-grade PORVs Used on Unit 2.Next Rept by 820415

ML20041D596
Person / Time
Site:	Millstone
Issue date:	02/18/1982
From:	Counsil W NORTHEAST UTILITIES
To:	Haynes R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
10CFR-050.55E, 10CFR-50.55E, AEC-MP3-267, B10421, NUDOCS 8203050447
Download: ML20041D596 (2)

Text

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O/ (i {p Mr. Ronald C. Ilaynes by '

s Region I Office of Inspection and Enforcement h 7~ ; Y 'g U. S. Nuclear Regulatory Commission ffj g gsb 631 Park Aven.se N -

King of Prussia, PA 10406

Reference:

(1) W. G. Counsil letter to B. H. Grier, Reporting of Potential Significant Deficiencies in Design and Construction, dated June 14, 1980.

Centlemen:

Millstone Nuc1 car Power Station, Unit No. 3, Second Interim Report in the Reporting of a Potential Significant Deficiency in Design; Minimum Charging Pump Flow As required by Title 10, Code of Federal Regulations Part 50, Foragraph 55(e), Northeast Nuclear Energy Company (NNECO) reported a potential significant deficiency in the design of Millstone Unit No. 3 in Reference (1). We stated that Westinghouse Electric Corporation reported to NNECO that following a secondary system high energy line rupture the cen-trifugal charging pumps may not be capable of delivering their minimum required flow to the reactor coolant system at pressurizer safety valve set point pressure. Thus, without minimum flow pump damage might occur due to overheating.

After detailed evaluations by Northeast Utilities Service Company (NUSCO) and Westinghouse, we have concluded that for the case of a steam line or feedwater line break, concurrent with a loss of offsite power, adequate charging pump flow will be provided by the safety grade PORV's used on Millstone Unit No. 3. The Westinghouse calculation of these transients is overly conservative in that they assume the Main Coolant Pumps to continue to run despite the loss of off-site power.

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, As a result of our detailed evaluation of this potential significant deficiency, additional concerns have been raised. We are presently confirming whether or not the pressure transient would occur if off-site-power is availabic and the auxiliary feedwater system functions as designed. Also, we are verifying whether or not the adverse environ-3 mental conditions present as a result of a high energy line break

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within primary containment would have an effect on the accuracy of the pressurizer pressure transmitters which provide the opening signal to the PORV's, and if so, does this have a detrimental effect on the overall

> transient. l We anticipate, because of our continuing evaluation, that our final i report on this potential significant deficiency will not be completc  ;

until approximately two more months. We therefore plan to submit our 3 final report to you by April 15, 1982.

We trust the above interim report adequately conveys the status of our efforts on this potentially significant deficiency in design. Your j Mr. E. J. Brunner was notified by our Mr. J. M. Powers that this report would be late and transmitted to you on or before February 17,

, 1982 as opposed to February 1, 1982.

Very truly yours, -

2 W. 'G. Counsil Senior Vice President cc: Mr. James H. Sniezek, Director Division of Resident and Regional Reactor Inspection Office of Inspection and Enforcement i U. S. Nucicar Regulatory Commission Washington, D.C. 20555 1

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