ML20249C748
| ML20249C748 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 06/24/1998 |
| From: | Dennis Morey SOUTHERN NUCLEAR OPERATING CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-97-04, GL-97-4, NUDOCS 9807010148 | |
| Download: ML20249C748 (4) | |
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Dave Morey Southrrn Nuclear Vice President Opsrating Company Iarley Project P.O. Box 1295 Birmingham, Alabama 35201 Tel 205.992.5131 SOUTHERN A.
l-June 24,1998 COMPANY Enery toServe Ysur%rld" Docket Nos.: 50-348 10 CFR 50.54 50-364 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington,DC 20555 Joseph M. Farley Nuclear Plant Response to Request For Additional Information Regarding Generic Letter 97-04,
" Assurance of Suflicient Net Positive Suction Head For Emergency Core Cooling and Containment Heat Removal Pumps" Ladies and Gentlemen:
By letter dated June 1,1998, Southern Nuclear Operating Company (SNC) revised the response to Generic Letter 97-04. During a telephone conference call on June 11,1998, the NRC Staff requested responses to additional questions. The Attachment provides the SNC responses to these questions.
Ifyou have any questions, please advise.
Respectfully submitted, fll, );ggs Dave Morey o
EWC/ cit:GL9704tc. doc Attachment cc: Mr. L. A. Reyes, Region II Administrator l
Mr. J. I. Zimmerman, NRR Project Manager l
s Mr. T. M. Ross, Plant Sr. Resident Inspector b
9807010148 990624 PDR ADOCK 05000348 P
t ATTACHMENT Joseph M. Farley Nuclear Plant NRC/SNC Conference Call of June 11.1998 Regardine NRC Generic Letter 97-04
.c-ATTACHMENT Response to Request for AdditionalInformation Regarding NR.C Generic Letter 97-04,
" Assurance of Sufficient Net Positive Suction Head for Emergency Core Cooling and Containment Heat Removal Pumps" The following questions and answen are in regard to the June 1,1998 letter revising the response to GL 97-04.
1.
Please explain why the increased containment spray now and decreased RHR Sow are not accounted for in the table on page 2 which shows the calculated screen headloss for Unit 1.
As historical test data, the table is not affected by the increased CS and decreased RHR flow values reported elsewhere in SNC's letter. Updated flows were used in conjunction with the worst-case measured head loss from the table to calculate an updated bounding screen head loss.
2.
Were Rows used in the headioss calculations just recently updated (i.e., before the GL was the screen test data headioss used in the NPSH calculations)?
A bounding screen head loss was recently cal::ulated using the updated CS and RHR flows,
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as discussed in response to question #1 above. This bounding screen head loss term has been applied in the updated NPSH calculations.
I With regard to use of screen head losses in the original NPSH calculations, as stated on page 2 of SNC's June 1,1998 letter, "These measured head losses are small when compared to the overall friction losses used in calculating the NPSH available, and in some cases were neglected in the original calculations."
l 3.
Please explair; the decrease in RHR Row discussed in note I. Please explain l
the decrease from 5900 gpm as described in the table on page 2 to 4400 and l
4415 gpm discussed in questions 2 and 3 of your GL response.
Postulated post-LOCA RHR (and CS) flows were used in the model testing program to maximize the intake screen head losses. Startup testing intiicated that RHR pump flows approached mnout conditions, and the flows were reduced by adding flow restricting orifices and mechanical valve stops to yield the 4400/4415 gpm values reported.
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4.
Please explain what is meant by revised pump elevations in note 2.
The original calculations used the pump suction pipe centerline or flange face elevation when computing the static head term in the NPSH available equation. The updated calculations use the pump impeller elevation.
5.
Please explain note 5. How can the containment spray pump flowrate increase while the NPSH required remain constant? What is meant by more conservative sump level assumptions, and how do these assumptions, together with increased containment spray flow, result in a reduction of NPSH available.
The Containment Spray pump curves provided by the vendor included only " typical" NPSH required curves. Subsequent testing of duplicate pumps yielded the NPSH required data now applied to Farley. This test data reduced NPSH required relative to the " typical" NPSH required curves originally provided for Farley. Although the flow increased, the NPSH required remained constant.
The Farley reactor cavity is considered a " dry" design in that it incorporates features to prevent the cavity from filling quickly in the post-LOCA environment. The original calculations ofNPSH available did not consider reduction of containment sump level due to fdling of the reactor cavity. The recently updated calculations conservatively assume a 1
lower sump level corresponding to immediate fill of the cavity, and therefore a decrease in NPSH available.
6.
Please provide the maximum sump temperature assumed in the NPSH i
l analyses.
The pressure drop calculations used to Jetermine the pipe friction losses conservatively use a containment sump water temperature of 100*F, thus maximizing the calculated frictior.
losses.
1 For the calculation establishing available NPSH, the water in the sump is considered a saturated liquid. Therefore, no credit is taken in the NPSH analyses for pressure above the saturation pressure.
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