ML20206H228
| ML20206H228 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 04/09/1987 |
| From: | Nauman D SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8704150295 | |
| Download: ML20206H228 (2) | |
Text
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10CFR50.90 Ygff7 Electric & Gas Company Den A.
u bi 29218 Nuclear Operations senaa
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April 9, 1987 t
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Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission J
Washington, D. C. 20555 1
Subject:
Virgil C. Summer Nuclear Station Docket No. 50/395 Operating License No. NPF-12 Engineered Safety Features Response Time
Dear Mr. Denton:
By letter dated December 12, 1986, South Carolina Electric & Gas Company requested a revision to Technical Specification 3/4.3.2, " Engineered Safety Feature Actuation System Instrumentation," and its associated Basis. Your Staff has requested clarification on certain aspects of this submittal, the responses to which are provided on the attached.
Should you have any further questions, please call at your convenience.
V y t g\\
y ours, 4 Nau n MDB/ DAN:bjh Attachment c:
- 0. W. Dixon, Jr./T. C. Nichols, Jr.
R. M. Campbell, Jr.
E. C. Roberts K. E. Nodland
- 0. S. Bradham R. A. Stough J. G. Connelly, Jr.
G. O. Percival D. R. Moore R. L. Prevatte W. A. Williams, Jr.
J. B. Knotts, Jr.
J. Nelson Grace M. D. Blue Group Managers NPCF C. A. Price PSRC C. L. Ligon (NSRC)
File 8704150295 870409
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PDR ADOCK 05000395 f
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,d' Attachment to H. R. D;nten Letter April 9, 1987
- Page 1 of 1 1-OUESTION:
' i What computer codes and revisions were used for the boron injection tank i
(BIT) removal analysis? What factors accounted for the reduction in calculated peak containment pressure and temperature from the original i
analysis?
ANSWER:
The mass and energy releases for the enveloping reactor coolant system accidents for BIT removal were calculated using the April 1984 revision of l
LOFTRAN. Unlike the original analysis which used MARVEL, the LOFTRAN code improves heat transfer modeling and also adds modeling of the reactor 4
protection system. The net effect of these improvements was to reduce the mass and energy releases into containment.
1 i
The BIT removal containment analysis utilized CONTEMPT LT/26 which, unlike LT/22 used in the original analysis, allows for superheat and condensation.
The reduced mass and energy releases into containment and the improved j
modeling of containment response reduced peak containment pressure from 47.1 psig to 45.8 psig and reduced peak containment temperature from 324*F to 321*F for the BIT removal analysis-.
OUESTION:
Concerning the reactor building cooling unit (RBCU) accident analysis as outlined in your December 12, 1986 letter, what are the bases for the j
following:
1)
No heat removal until 71.5 seconds.
2) 95% of full heat removal capability at 71.5 seconds.
I 3)
A linear ramp increase from 95% to 100% of full heat removal capability at 86.5 seconds.
1 ANSWER:
i 1)
No flow to the RBCUs is conservatively assumed until isolation of the service water (SW) system from the non-safety, non-seismic industrial i
cooling water (CI) system is complete by closure of valves 3110A,B-SW at 71.5 seconds.
i i
i 2)
Once the CI system has been isolated, the RBCU discharge valves 3107A, i
B-SW, would still be opening, which would restrict SW flow from the RBCUs. Based on calculations, the valves would be passing 3800 gallons 4
l perminute(gpm)pertrainwhichissufficientfor95%heatremoval capability at 71.5 seconds.
3)
Valves 3107A,8-SW open fully at 86.5 seconds. Although the flow increase from 3800 gpm to 4000 gpm would be exponential, the safety i
analysis conservatively assumes a linear increase.
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