ML19339C994
| ML19339C994 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 02/09/1981 |
| From: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8102130064 | |
| Download: ML19339C994 (4) | |
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c-SOUTH CAROLINA ELECTRIC a gas COMPANY pose emcc som is.
COLUMBIA, SOUTH CAROLINA 29218 T b?hcwots.JR.
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February 9, 1931
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Mr. Ilarold R.
Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Conmission Washington, D. C.
20555 l
Subj ec t : Virgil C. Summer Nuclear Station Docket No. 50/395 FSAR Question 211.86 (Cold Shutdown)
Dear Mr. Denton:
In the response to FSAR Question 211.86 information regarding the comparison of the four loop Diablo Canyon plant and the three loop Virgil C. Summer Nuclear, several comparison numbers were missing.
The attached marked up pages of that response provides those numbers.
This information will be included in the next FSAR amendment.
If you have any questions, please let us know.
Very truly yours,
- 1( L
- A.4.b T. C. Nichols, Jr.
RBC:TCS:glb Attachment ec:
V. C. Summer w/o enclosure G
- 11. Fischer w/o enclosure T. C. Nichols, Jr. w/o enclosure E. H. Crews, Jr.
O. W. Dixon, Jr.
C. A. Price D. A. Nauman W. A. Williams, Jr.
R. B. Clary A.
R. Koon ghl A. A. Smith
- 11. N. Cyrus J. B. Knotts, Jr.
J. L. Skolds B. A. Bursey f/
O. S. Bradham ISEG NPCF/Whitaker File 1
8102Isoogy
s st ch a cmparison between a t hree loop and a four loop plant.
j.- rr:i t The hy&.iulic resi stance coef ficicats a ppl i c abl e to normal ficw con-
[
ditions are as follows:
Vi r gi l C.
Summer Diablo Canvon Unit 1 Nuclear Station
-M
[
Feactor Core & Internal s 7.6 x 10-10 f o,;, y f p f t/(loop gyn)2
(;.
a 9., v r a r ' a r. 21 e s 36.8 al1 F.cs piping 2 '. 0 2, 9. 7 Steam Generator 114.4
,jp g 27 152.8 s
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)
1/2 Flcw Ratio Virgil C.
Suru.e r =
182.8.= (% ter) /,, Oyl Diablo Canyon (L 1.tec) i'7 //7 The general arrangement of the reactor core and internals is the saae in the Virgil C.
Suc:aer Nuclear Station and Diablo Canyon.
The coeffi-23 cients indicated represent the resistance seen by the flow in one loop.
As exhibited, the difference between the interals of a three loop and a b
Cour loop plant results in a hi gher coef ficient for the Virgil C. Sunner Nuclear Station.
The reactor vessel outlet nozzel configuration for both plants is the saae.
The radius of curvature between the vessel inlet nozzle and down-comer section of the vessel on the two plants is dif ferent.
Based on 1/7 scale model testing performed by Westinghouse and other literature, the radius on the vessel nozzle / vessel downconer juncture influences the hydraulic resistance of the flow t urning f rcm the nozzle ta the down-(
comer.
The Diablo Canyon vessel inlet noz zl e radius is significantly smaller than that of the Virgil C.
Suraner Nuc lea r St ation, as reflected by the higher coefficient for Diablo Canyon.
The resistance (coetficient) for the RCS pi ping for both plants is the
- 1me.
x.la
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211.86-21 AMEND > TNT.23
~
J AN**.Wt, 1981
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For typical 3-Inop and 4 -loop plant s (including the Virgil C.
Su:ner Nuc l e a r S t a t i c,n I Diablo Canyon) there are two potential flow paths by
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)
which flow crosses the upper head region boundary in a reactor.
These the head cooling spray nozzl es and the guide tubes.
The head paths are cooling spray nozzles co stitute a flow path between the downcener region and the upper head region.
The temperature of the flow which
(
enters the head via this path corresponda to the cold leg value (i.e.
Tcold).
Fluid may al so be exchanged between the upper plenum region (i.e., the portien of the reactor between the upper core plate and the upper support plate) and the upper head region via the guide tubes.
'T Guide tubes are dispersed in the upper plenan region fran the center to j
the periphery.
Because of the nonuniform pressure distribution at the plate elevatica and the flow distribution in the upper plenum upper core region, the pressure in the guide tube varies from location to location.
These guide tube pressure variations create the potential for flow to either enter or exit the upper head region via the guide tubes.
23 To ascertain any difference between the upper head cooling capabilities between Diablo Canyon and the Virgil C.
Sucmer Nuclear Station, a com-
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_ j parison of the hydraulic resistance of the upper. head regions were made.
These flow paths were considered in parallel to obtain the following results.
Diablo Canyon Virgil C.
Summer Unit 1 Nuclear Station Flow Area (ft2) o,77
,63 Less Coefficient 1.51
/,y 7 Oserall Hydrau1*c Resistance 2.57 q'
(ft-4) f Relative Head Region Flowrate 1.00 (l a t c c )-
/, j ]
(.
(Based on Hydraulic Resistance)
Head Region Flow Rate Relative 1.00 f,5'j to Loop Flow
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1.0 211.86-23 AMENDMENT 73 gAwkAw%, 1981
As indicated above the ef f ec ti ve hydraul ic resistance to flow in the 79 Virgil C. Summer Nuclear Stat ion i s 4*) t ir.es greater than Di e.bl o
,y c.
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Canyen.
Assuming that the same pressure differential existed in both 18
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plants the Virgil C.
Summer head flow rat e would be 40 percent of the Diablo Canyon flow.
Virgil C.
Summer is a 3-loop plant and Diablo Canyon is 4-loop; therefore, in terms of relative portions of loop flow s
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'l c ermunica ti ng with the head region, theVirgil C. Surner head flow as a 50
- > u fraction of loop flow i s fyrb percent greater than the correspending
/
Diablo Canyon fraction.
In addition the overall mass of metal acsociated with the Virgil C. Summer Nuclear Station upper head is T
l significantly less than for Diablo Canyon due to the smaller physical s
size.
Th us the upper head cooling capability at the Virgil C.
Summer 23 Nuclear Station would be no worse and would likely be better than demonstrated by the Diablo Canyon natural ci rculation cooldown tes t.
It can, therefore, be concluded that the results of the natural circu-lation cooldown tests performed at Diablo Canyon will be representative of the natural circulation and baron mixing capability of the Virgil C.
Sumner Nuclear Station.
The results of these tests will be reviewed for
(
)
applicability.
A natural circulation cooldown test will be performed at the Virgil C.
Summer Nuclear Station if the Diablo Canyon prototype test, or similar test at another nuclear plant, is not cempleted or does not pr ovi de satisfactory results during the first fuel cycle at the Virgil C. Summer Nuclear Station.
s (f
j;24 at,
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zu 211.86-24 AMENDMENT 21
/
9my, 1981 4