SVP-98-172, Informs of Licensee Review of Documents Re Use of Containment Overpressure to Assure ECCS Pumps Have Adequate Npsh,In Response to NRC Questions Re Design Insp Repts 50-254/98-201 & 50-265/98-201

Informs of Licensee Review of Documents Re Use of Containment Overpressure to Assure ECCS Pumps Have Adequate Npsh,In Response to NRC Questions Re Design Insp Repts 50-254/98-201 & 50-265/98-201

ML20247M098
Person / Time
Site:	Quad Cities
Issue date:	05/12/1998
From:	Dimmette J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
50-254-98-201, 50-265-98-201, SVP-98-172, NUDOCS 9805260170
Download: ML20247M098 (3)

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[ ()uad ( aut* &act.ning Mahon 22'lO 2O(dh Attunc North Cordin A 11.01242 "'40 h t .kOM i ll s i SVP-98-172 May 12,1998 U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Document Control Desk

Subject:

Quad Cities Nuclear Power Station Units 1 and 2 Response to Questions Raised During NRC Design Inspection on Containment Overpressure NRC Docket Numbers 50-254 and 50-265 The purpose of this letter is to infort you of our review of documents related to the use of containment overpressure (COP) to assure emergency core cooling system (ECCS) pumps have adequate net positive suction head (NPSil). Various questions have been raised during the recent NRC Design Inspection (Report No. 50-254/98-201 and 50-265/98-201) relating to the amount of COP currently being used in design bases NPSil calculations and whether this is consistent with our licensing bases. We have reviewed those questions and it is our conclusion that our current NPSII design basis remains in agreement with, the original questions and our responses raised during the licensing of Quad Cities Units 1 & 2, the original NRC Safety Evaluation Report (SER) j supporting issuance of the operating license and all subsequent SERs, cur Updated Final Safety Analysis Report (UFSAR) and,in ourjudgement, that no Unreviewed Safety Question (USQ) exists. The following summarizes our review.

During the original licensing of the Quad Cities Station, a question arose with regard to the crediting of COP. FSAR Amendment 13, Question 6.2 states," Discuss the extent to which containment pressure is relied upon to assure the availability of adequate NPSil at all suction temperatures for the various engineered safety features." The response to this question and follow up questions in Amendments 16 and 17 are inputs used by the Atomic Energy Commission (AEC) for the August 25,1971, SER. That SER stated, "Our review of the residual heat removal system LPCI mode and the core spray emergency cooling mode indicates that a containment overpressure of a few psi is needed for about 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> following a design basis loss of coolant accident to assure adequate net positive suction head (NPSil) to the RIIR pump in the LPCI mode."

Also, in response to NRC requests for information on the potential for Low Pressure Coolant Injection (LPCI) pump damage due to operation in excess of design flow j .U during a postulated Loss of Coolant Accident (LOCA) (loop select logic failure), the January 4,1977 SER on this issue agreed that the LPCI pump damage due to cavitation would not occur.

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USNRC

. 'SVP-98-172 2 May 12,1998 in December 1996, Comed discovered that the head loss across the ECCS suction strainers for the Quad Cities and Dresden Stations was greater than that stated in the UFS AR. Operability evaluations were performed for both stations to address the effect on the LPCI and Core Spray pumps. The Quad Cities operability analysis was based on a Dresden hydraulic piping model, a short term 1996 Dresden COP analysis and 1993 Quad Cities COP analysis. Comed determined that the pumps were operable.

A 10CFR50.59 safety evaluation was performed for a UFSAR change following the operability determination to credit the 1993 COP analysis. The 10CFR50.59 safety evaluation determined that no Unreviewed Safety Question (USQ) existed based on the above Quad Cities SERs which, unlike Dresden, credited containment overpressure and, in ourjudgement, that the 1993 COP analysis results fell within the bounds of the licensing basis of the Quad Cities Station. In addition, the analysis relied upon a containment analysis method previously approved by the NRC staff.

The current Quad Cities NPSil calculations are based on a Quad Cities hydraulic piping j model, the short term 1997 Dresden COP analysis, the 1993 Quad Cities COP analysis

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and assumptions / methodology used for the Dresden licensing amendment. The Dresden a COP containment analysis is applicable to Quad Cities based on the similarity between the stations. The credited COP was approved for Dresden Units 2 and 3 via Amendments 157 and 152.

The response to Generic Letter (GL) 97-04," Assurance of Sufficient Net Positive Suction llead for Emergency Core Cooling and Containment Ileat Removal Pumps" indicated 9.5 psig COP was available which is consistent with the Dresden short-term analysis. The required COP in the short term as stated in the GL 97-04 response is based on the pressure required to prevent cavitation at 240 seconds and conservatively using the peak pool temperature at 10 minutes.110 wever, since short-term pump cavitation is acceptable, the R11R pumps do not require any COP in order to provide the required flow and the cose spray pumps require less than 3 psig at the concurrent pool temperature (i.e., an overpressure of a few psi as stated in the SER) to maintain required flow to the core to ensure diat the postulated peak cladding temperature is not affected.

Therefore, the current NPSH design bases including the required COP is in agreement with the 1971 and 1977 SERs.

Quad Cities has contracted with General Electric to perform a Quad Cities specific COP analysis. In addition, to resolve a question raised during the NRC Design Inspection with regard to the RiiR heat exchanger capacity, we have requested the heat exchanger manufacturer either to retrieve the original design calculations or reconstitute the thermal analysis.

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USNRC

. 'SVP-98-172 3 May 12,1998 The following commitment is being made by this letter:

After receipt of the original design calculations and the reconstituted thermal l analysis, our calculations and UFSAR will be updated and a 10CFR50.59 Safety l Evaluation will be completed. This work will be completed by September 30, 1998. If a USQ is identified we will notify the NRC and a request for a license amendment will be submitted within 60 days of that date. (NTS 2541239804501) i If there are any questions or comments concerning this letter, please refer them to Mr. l Charles Peterson, Regulaf.ory Affairs Manager, at (309) 654-2241, ext. 3609. I Srncerely, e . __ b'

$0&W' oel P. Dimmette, Jr.

Site Vice President j Quad Cities Station I i

cc: A. B. Beach, Regional Administrator, Region 111 l R. M. Pulsifer, Project Manager, NRR C. G. Miller, Senior Resident Inspector, Quad Cities W. D. Leech, MidAmerican Energy Company D. C. Tubbs, MidAmerican Energy Company F. A. Spangenberg, Regulatory Affairs Manager, Dresden INPO Records Center Office of Nuclear Facility Safety, IDNS DCD License (both electronic and hard copies)

M. E. Wagner, Licensing, Comed SVP Letter l

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