ML20217K701

Provides Response to Questions Related to Request for License Amend,Per 10CFR50.90, Credit for Containment Overpressure. Supporting Calculations Encl

ML20217K701
Person / Time
Site:	Quad Cities
Issue date:	10/13/1999
From:	Krich R COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20217K705	List: ML20217K701 ML20217K744 ML20217K764
References
NUDOCS 9910260224
Download: ML20217K701 (15)

Text

{{#Wiki_filter:Commonwealth Edison Comlyny We0 Opus Place Downen crove, it 60515-5701 }: October 13,1999 l i U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 I -Quad Cities Nuclear Power Station, Units 1 and 2 i Facility Operating License Nos. DPR-29 and DPR-30 NRC Docket Nos. 50-254 and 50-265

Subject:

Response to Questions Related to Request for License Amendment Pursuant to 10 CFR 50.90,

• Credit for Containment Overpressure"

Reference:

Letter from J. P. Dimmette, Jr. (Comed) to U.S. NRC, " Request for License Amendment Pursuant to 10 CFR 50.90, Credit for Containment Overpressure " dated January 29,1999. The purpose of this letter is to provide information requested by the NRC during teleconferences held on August 18,1999, and September 13,1999. in the referenced submittal, we requested an amendment to the license to allow use of containment overpressure to support the Net Positive Suction Head (NPSH) available for the Emergency Core Cooling Systems (ECCS) at Quad Cities Nuclear Power Station, Units 1 and 2. During teleconferences held with the NRC on August 18,1999 and September 13,1999, the NRC requested a copy of the calculations for determining the debris bed head loss for the strainers and the deration that Containment Overpressure (COP) is required. in addition, the NRC requeste i that the amount of COP be limited to a small amount above that required for NPSH. The request for licensing amendment described threa. COP values. .. Available COP - the minimurn available pressure a t determined by containment lI analysis. Credited COP - the requested licensing amendmen ' value. Required COP - the value required to meet requireo NPSH. 9910260224 991013 \\ ADOCKOS00g24 gx PDR P 4 A Unicom Company wic -

u r I ' October 13,1999 -{ U.S. Nuclear Regulatory Commission

Page 3

~ bec:.. Project Manager-NRR ' Office of Nuclear Facility Safety - IDNS Senior Reactor Analyst -IDNS. Manager of Energy Practice - Winston and Strawn 4 E Director, Licensing and Compliance - Comed Vice President, Regulatory Services - Comed Comed Document Control Desk Licensing (Hard Copy) j 3 ' Comed Document Control Desk Licensing (Electronic Copy) W. eech, MidAmerican Energy Company. L D. Tubbs, Mid American Energy. Company j ( Regulatory Assurance Manager - Dresden Nuclear Power Station Regulatory Assurance Manager-Quad Cities Nuclear Power Station NRC Coordinator - Quad Cities Nuclear Power Station NSRB Site Coordinator - Quad Cities Nuclear Power Station j INPO Records Center j SVP Letter File i l l I

g.

.(- i STATE OF ILLINOIS Docket Nos. 50-254' 50-265 IN THE MATTER OF:

COMMONWEALTH EDISON (COMED) COMPANY QUAD CITIES NUCLEAR POWER STATION ' UNITS 1 AND 2 AFFIDAVIT I affirm that the content of this transmittalis true and correct to the best of my knowledge, information and belief.

4 g la ervices Subscribed and sworn to before me, a Notary Public in and for the State above named, this /b day of 4- _,19 i P# " 0FFICIAL SEAL

• Joseph V. Sipok j

Notary Public, Stam of Minois ll My Commission E9tes 11/24/2001 j l _ y i 1 i i

4 !L o, e

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"f October 13,1999 U.S.LNuclear Regulatory Commission ' Page 2 m. iO l 3._ F-7 As discussed with the NRC on September 13,1999, we propose to reduce the amount of .z credited COP during the initial stage of a LOCA. Attachment A provides corrected pages to the Referenced letter. . calculations and a copy lol Attachment B provides copies of the requested f a calculation addendum that determines the time that COP is s. required to ensure NPSH.; Based on the COP requested the total time required for COP is - about 40 hours.The revised information, provided in Attachment A, does not change the Leonclusions provided in the No Significant Hazards Consideration, contained in the L 1 January 29,1999, submittal. Should you have any questions conceming this letter, please contact Mr. C.C. Peterson at (309) 654-2241, extension 3609. { . Respectfully,. ( ./ \\ O ' R. M.' ' chl Vice President - Regulatory Servic' s e ~ Attachments: A. Corrected Pages .B. Supporting Calculations . Regional Administrator-NRC Region Ill cc: NRC Senior Resident Inspector - Quad Cities Nuclear Power Station l ]. I h y. nr l[ t

t Attachment A Corrected Pages (Page1of1) In Attachment A to our letter dated January 29,1999, Comed provided a description and safety analysis for proposed changes specified in the requested license amendment. As a result of discussions held with the NRC on August 18,1999, and September 13,1999, a revision to the information provided in the January 29,1999, submittal is required. The proposed change from "8.0 psig for the first 210 seconds" to "5.7 psig for the first 240 seconds" has resulted in a revision to pages 5,11 and 12 of - Attachment A. The revised revisions are highlighted in italic font in the attached pages. This revision also affects Tables F-1, F-2 and F-3 and Figures F-1 and F-2. Revised tables and figures are also attached. We have also noted that some text was inadvertently omitted from the last paragraph on page 13. The omitted text is attached as page 13A. i

ATTACHMENT A DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES SVP-99-012 Page 5 of 18 As part of this change, Comed requests NRC approval of a larger value of credited COP,5.7 psig in the first 240 seconds of the accident, to provide a margin between l available and required ECCS flow. Comed has performed the required analyses to ensure that this larger amount of COP would be available following the accident [6,7]. i The larger COP value for the first 240 seconds is requested to increase the margin over l the NPSH requirements of the pumps. Utilizing this credited COP would permit us to not be required to assume pump cavitation during the initial stages of the accident, during the occurrence of PCT. This is consistent with the analyses performed for Dresden Nuclear Power Station [20]. 1 E. DESCRIPTION OF THE PROPOSED CHANGES Based upon the results of the revised analyses, Comed requests approval for the following amount of COP following a design basis LOCA: j Time Credited Containment (seconds) Pressure (psic) 0 - 240

5. 7 240- 600 2.5 600 - 10000 3.0 10000 - accident end 3.5 l

The proposed amount of containment pressure is less than 90 percent of the minimum available pressure response predicted by the revised GE containment analyses using the engineering computer program SHEX-04. These analyses are described in more detail in Section F. The maximum long-term suppression pool temperature from these revised analyses is 182 F [6]. In addition to the COP table listed above, UFSAR changes in support of the revised NPSH analyses have been included for information in Attachment B. F. SAFETY ANALYSIS OF THE PROPOSED CHANGES In order to identify containment response to a LOCA, conservative analyses were performed. These analyses evaluated the containment pressure and temperature response during the short-term and long-term following the Design Basis Accident - Loss of Coolant Accident (DBA-LOCA). Short-term is defined as the time period from 7 Revised Submittal October 13,1999 l l

a ATTACHMENT A DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES SVP-99-012 Page 11 of 18

4. Containment conditions that minimize the available NPSH used in the analysis (See Section F.1.).

~ 5. Initial suppression pool temperature is 95 F, which is the maximum pool temperature allowed by TS under normal operating conditions. This value is used as the initial pool temperature to maximize pool peak temperature, and is used as the minimum temperature during the post-LOCA NPSH analyses to maximize piping friction losses (maximum viscosity).

6. The minimum suppression pool level elevation is used assuming a maximum water level drawdown of 2.1 ft.

7. NPSH Required values at various RHR/CS pump flow rates are taken from the vendor certified pump curves.

The minimum suppression pool pressure required to meet RHR/CS pump NPSH requirements was determined for both the SF-LSL and SF-DG single failure cases. The minimum pool pressure required was compared to the minimum pool pressure available post-LOCA. If the pressure available is greater than the pressure required, then adequate NPSH exists. If the available pressure is less than the pressure required, then the potential exists for the pumps to cavitate, resulting in reduced flows. For the SF-LSL case, no cavitation is expected to occur for the first 240 seconds post-l 3 LOCA. During this time, the RHR and CS pumps will be operating at maximum flow. Since PCT occurs at about 180 seconds, the CS pumps will deliver adequate flow to ensure no impact on PCT. With the credited 5.7 psig COP up to 240 seconds post-LOCA, the CS pumps will have about 1 psi of NPSH allowance at flow rates as high as approximately 6,200 gpm, which is sufficiently greater than the 5,650 gpm per pump assumed in the PCT analyses. With the credited 2.5 psig COP after 240 seconds, the l RHR and CS pumps may cavitate, resulting in reduced flows. The CS pump NPSH deficit reaches a maximum of 6.6 feet at 600 seconds. Under these conditions for NPSH, CS pump flow will be reduced from approximately 12,400 gpm (~6,200 gpm per pump) at 240 seconds'to about 11,500 gpm (5,750 gpm per pump) at 600 seconds. This represents the. minimum expected flow from the CS pump for the 240 to 600 l second interval. A flow rate of 9,000 gpm is assumed into the vessel in the reflood calculations. The minimum calculated flow rate of 11,500 gpm provides sufficient margin above the required 9,000 gpm. Figure F-1 gives pool pressure, temperature, and RHR/CS pump required pressure for several pump combinations over the short-term period for the SF-LSL case. As stated above, a potential exists for the RHR and CS pumps to cavitate after the first 240 seconds post-LOCA. However, the pump vendor performed a cavitation test on an l Revised Submittal October 13,1999

4 ATTACHMENT A DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES SVP-99-012 Page 12 of 18 RHR pump. The Cavitation Test Report for Bingham 12x14x14-1/2 CVDS Pump ) demonstrated no evidence of any damage to the pump components from cavitation with i up to one hour of operation at the cavitating condition (10). This analysis was reviewed with respect to the CS pump and the results were determined to be applicable. This conclusion is based on the fact that the RHR and CS pumps are the same make and model and utilize the same impeller pattern. All RHR l and CS pumps have tested NSPH required curves that are essentially identical; i.e., results are within 1%. For the SF-DG case, no cavitation is expected to occur for the first 240 seconds post-l LOCA. During this time, the RHR and CS pumps will be operating at maximum flow. ( The results of the SF-DG case support the conclusion that the SF-LSL case is the limiting single failure from an RHR/CS pump NPSH perspective. RHR/CS pump flow requirements are as follows:

1. For the SF-LSL and SF-LPCI cases, a two-pump CS flow of at least 11,300 gpm up to 240 seconds ensures that PCT will be maintained.

l

2. For the SF-DG case, a two-pump RHR flow of at least 9,000 gpm and a single CS pump flow of at least 5,650 gpm are required for PCT to be maintained.

j i

3. Only a constant total pump flow of 9,000 gpm is required to achieve 2/3 core I

reflood in less than six minutes from the time ofinjection. Therefore, under the most limiting single failures, the ECCS will still perform its function in the short-term with no credit for operator action. F.4 RHR/CS Post-LOCA Lone-Term NPSH Evaluation The evaluation examined the net positive suction head (NPSH) available to the Quad Cities Nuclear Power Station RHR and CS pumps after the first 600 seconds following a DBA-LOCA for several pump combinations. If the suppression pool pressure available is greater than the pressure required for adequate NPSH to the RHR and CS pumps, then these pumps have adequate NPSH for operation. If the suppression pool pressure available is less than the pressure required for the pumps, then there is inadequate NPSH for operation and potential pump cavitation. In these situations, RHR pump flows were reduced below nominal values and Revised Submittal October 13,1999

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ATTACHMENT A - DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES Page 13A of18 scenarios. For these cases, throttling of the RHR pump flows to below rated flows is required, but the total flow remains above the minimum requirements for containment cooling. Table F-4 provides the required COP for the various cases. Figures F-4 and F-5 gives the pool pressure and RHR pump pressure requirements for several pump combinations over the long-term period. 1 I Revised Submittal ) October 13,1999

Attachmeet B Supporting Calculations t ("r.ge1of1) The following calculations were performed in support of NRC Bulletin 96-03 and are attached for information. Calculation Number Title QDC-0010-M-0396, Rev.1 Quad Cities Station Unit ' : ECCS Strainer Head 2 Loss Estimates QDC-1600-M-0545, Rev. 2 Quad Cities Station Unit 1: ECCS Strainer Head Loss Estimates The following calculation addendum was performed in support of this request for license amendment and is attached for information. DCR 990247, Rev. O Containment Overpressure Duration Requirement (Addendum to Calculation QDC-1000-M-0781) Note: The above calculation addendum is the source document for information contained in the cover letter. Calculation number QDC-1000-M-0781, RHR/CS Pump NPSH Analysis - Design Basis LOCA (Long Term) was previously transmitted by the referenced letter. t I i i l i l i}}