ML19259C039
| ML19259C039 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/30/1979 |
| From: | Taylor J BABCOCK & WILCOX CO. |
| To: | Israel S Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7906120246 | |
| Download: ML19259C039 (3) | |
Text
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Babcock &Wilcox Po.e, cene,,,,cn c,,,,
P.o. Box 1260, Lynchburg, Va. 24505 Telephone: (804) 384-5111 5 fay 30, 1979 Mr. Sanford Israel Reactor Systems Branch Division of System Safety Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, DC 20555
Dear Mr. Israel:
The attached information is in response to your request for verification that the auxiliary feedwater system will be adequate in the event of total loss of main feedwater. This information was requested during a conference phone call between the NRC staff, Sacramento !!unicipal Utility, and BSW on 5/23/79.
If you have any further questions, please contact bir. J. T. Willse (Ext. 2208) of my staff.
Very truly yours fhJ k &
J. H. Taylor
>f ana ge r, Licensing JHT/fw 2284 195 cc:
R. B.
Borsum (BSW - Bethesda Office)
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The SMUD auxiliary feedwater system (AFW) has been studied to verify that adequate AFW will be provided if total loss of main feedwater occurs during these accidents:
- 1) Loma of feedwater
- 2) Steam line break
- 3) Feedwater line break.
In all cases, it was determined that the AFW flow will be initiated auto-matically and that the flow provided by one AFW pump is sufficient to maintain the plant in a safe condition. The following is a su= mary of the analysis assumptions and the AFW initiation signal which would be available during each of these accident scenarios:
- 1) Loss of feedwater.
A generic analysis (
has been performed applicable to B&W 177 plants which has shown that following the loss of the main feedwater pumps, AFW flow from one AFW pump within 40 seconds will be adequate to maintain the system pressure below the FORV setpoint. AFW vill be initiated automatically based on a low feedwater pump discharge pressure signal. Full AFW flow will be established within the 40 seconds assumed in the above mentioned analysis.
2)
Stea= line break. This accident was analyzed in the SMUD FSAR.
By referring to Figure 14.2-1, it can be seen that the priuary system pressure will drop below 1600 PSIG at about 20 seconds. At this pressure, the Safety Features Actuation System (SFAS) will provide a signal to start one of the auxiliary feedwater pumps. Flow from that pump will be fully established within 40 seconds (60 seconds after initiation of the transient).
Inasmuch as the pressures and primary temperatures following a steam line break (a cooldown accident) are considerably below those of the loss of feedwater discussed above, it is clear that flow from one AFW pump will also be adequate in this case to remove decay heat and maintain the system pressure below the PORV setpoint.
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- 3) Yeedwater line break. This accident was not analyzed in the SMUD FSAR; however, it has been analyzed on other B&W 177 plants assuming
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AFW flow within 40 seconds and found to yield acceptable results For SMUD, the AFW initiation signal (low main feedwater pump disch rge pressure) aill be received almost instantanenusly following the double inded rupture of a feedwater line.
Based on previous B&W analyses of 177 plant feed rater line breaks and the generic loss of feedwater analysis discusse.d in (..) above, it is concluded that adequate AFW flow will be provided following the double ended rupture of a main feedwater line.
REFERENCES 1) 7 etter, J. H. Taylor to R. J. Matteson, " Auxiliary Feedwater Flow Rate Sensitivity Study", May 31, 1979.
- 2) Docket No. 50-320, Section 15.1.8.
- 3) Docket No. 50-329/330, Sec; ion ?.5.2.8.
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