ML20078Q576
| ML20078Q576 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 12/13/1994 |
| From: | Schrage J COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9412220251 | |
| Download: ML20078Q576 (4) | |
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O Commonwealth Edison
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1400 Opus Place j-O Down:;rs Grova. Illinois 60515 a
December 13,1994 t
Office of Nuclear Reactor Regulation U. S. Nuclear bactor Commission Washington, D. C. 20555 Attn: Document Control Desk i
Subject:
Quad Cities Station Units 1 and 2 Individual Plant Examination (IPE);
NRC hquest for Additional Information (RAI)
NRC Docket Nos. 50-254 and 50-265
References:
(1) M. Vonk to T.E. Murley letter dated December 13,1993.
(2) C.P. Patel to D. L. Farrar letter dated June 9,1994.
j (3) J. L. Schrage to W. T. Russell letters dated August 8,1994 i
October 3,1994.
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l In hference (1), Commonwealth Edison Company (Comed) submitted the Individual Plant Examination (IPE) for Quad Cities Station Units 1 and 2. In the Reference (2) hquest for Additional Information (RAI), the NRC Staffidentified additional information which would be required in order to review and approve the IPE for Quad Cities Station.
Comed provided the required information in the Reference (3) letters. This letter transmits a minor revision to Comed's original response to Question 4 of Reference (2). This is provided as an Enclosure, and replaces the original response to Question 4. The changes to the original response are noted with either a strikeout line (deletion) or highlighted text (addition).
Comed sincerely apologizes for any inconvenience that this may have caused.
If there are any questions, please contact John L. Schrage at 708-663-7283.
Very truly yours, i
ohn L. Schrage Nuclear Licensing Administrator
' Enclosure cc:
J. Martin, Regional Administrator - Region III C. Miller, Senior Resident Inspector - Quad Cities Station R. Pulsifer, Project Manager - NRR E. Lois, RES/SAIB Oflice of Nuclear Facility Safety - IDNS PDR ADOCK 05000254 1-Iy I 9412220251 941213 1
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Enclosure Quad Cities Station IPE - Request for Additional Information Revision to Question 4
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I OUESTION 4 4.
~ The success criteria for a large LOCA indicates that 1 LPCI pump can be used for mitigation and that 1 RHRSW pump is adequate for containment cooling.
Please explain whether (a) the success criteria for LPCI accounted for leakage at the jet pumps' slip and bolted joints, and (b) the analysis supporting 1 RHRSW pump considered the potential fouling conditions in the RHR heat exchanger (s).
RESPONSE TO QUESTION 4 (a)
The Large LOCA success criterion for preventing core damage of using one LPCI pump in injection mode was based on an analysis performed using a Comed-specific version of the MAAP code. The Quad Cities plant model used in conjunction with Comed-MAAP assumed a LPCI pump head flow behavior that was obtained from the NSSS vendor's process flow diagram for the system.
The Comed MAAP code does not modelleakage out of the jet pumps, either via the slip joints (as a result of the low pressure difference across the joints) or via the bolted joins (as a result of differential thermal expansion between the bolts and rams-head). The success criterion analysis performed accounted for the long term, maximum possible slip joint leakage rate of 225 gpm by not crediting CRD hydraulic system inflow, which would be about 165 gpm under depressurized RPV conditions. The success criterion calculation did not account for bolted joint leakage which should be a short term phenomenon (i.e., until the temperatures of the bolts and rams-head equilibrate and the joint tightens),
j More detailed analyses, documented in the latest version of the Quad Cities UFSAR (Table 6.3-449), provide support for the IPE success criterion of one LPCI pump to provide adequate core cooling during a large LOCA. These analyses, which account for the maximum possible LPCI leakage under large LOCA conditions, indicate that two LPCI pumps ihdyhe?f6&spfs9Mupi5l injecting in response to a large break event will limit peak clad temperatures substantially below the licensing criterion of 2200 F: using Appendix K assumptions the margin is-742 520 F, while assuming nominal conditions leads to a margin of 4486 @74"F. These results strongly suggest that reducing vessel injection to one LPCI pump would provide adequate core cooling, as indicated by the Comed-MAAP results, as well as prevent the peak clad temperature from exceeding 2200 F.
(b)
The analysis supporting the Large LOCA success criterion for containment heat removal of one RHRSW pump was performed using a Comed specific version of the MAAP code. The Quad Cities plant model used in conjunction with
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Comed-MAAP assumed a default RHR Service Water (RHRSW) configuration of ons RHRSW pump available to direct cooling water flow to'one RHRSW heat exchanger for all Large LOCA success criteria calculations. The plant model.
used with Comed-MAAP also assumed a value of 0.0025 ft -hr *F/ Btu for the overall fouling factor of the RHRSW heat exchanger. This value was obtained from a drawing of heat exchanger details supplied by the plant vendor and does not account for fouling due to aquatic organisms.
Growth of aquatic organisms within the RHRSW system was modeled in the RHRSW system fault tree. Proliferation of living organisms within the..RHRSW j
system would impede system flowrates as well as foul heat transfer surfaces.
This type of fouling was assumed to cause a complete loss of heat removal function in an RHRSW loop affected by growth of such organisms. As a result of this modeling approach, the plant model used with Comed-MAAP did not account for aquatic growth in the value of the fouling factor used for the l
RHRSW heat exchanger. Rather, sequences in which aquatic fouling was -
4 assumed to occur in the RHRSW system resulted in not taking credit for' RHRSW heat removal in any associated Comed MAAP analysis.
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