ML20137S741

Forwards Addl Calculations,Clarifying Util Re Predicted Fuel/Pcrv Liner Temps Resulting from Design Basis Event from 8% Power & Subsequent Reactor Cooling Utilizing Liner Cooling Sys.Calculations Confirm Original Position

ML20137S741
Person / Time
Site:	Fort Saint Vrain
Issue date:	09/23/1985
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Hunter D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
P-85333, TAC-42527, NUDOCS 8509300491
Download: ML20137S741 (3)

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.T Public Service ..n. ..,*.

Company of Colorado f

P.O. Box B40 Denver, CO 80201-0840 (303)571- 7511 2420 W. 26th Avenue, Suite 1000, Denver, Colorado 80211 l! September 23, 1985 t SFp 2 5 885 1h Fort St. vrain p

~') Unit No. 1

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P-85333 Regional Administrator Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 Attn: Mr. Dorwin Hunter Docket No. 50-267

SUBJECT:

Low Power Operation of FSV

REFERENCE:

1) PSC Letter Warembourg to Hunter dated August 30, 1985 (P-85302)

2) PSC Letter Warembourg to Hunter dated September 10, 1985 (P-85312)

, 3) PSC Letter Warembourg to Hunter dated September 11, 1985 (P-85317)'

Dear Mr. Hunter:

In the follow-up low power operation letter of September 10, 1985, (Reference 2) PSC provided predicted fuel /PCRV liner temperatures as a result of a design basis event from 8% power and subsequent reactor cooling utilizing the liner cooling system (see response to Question 4, Attachment 1, P-85312). The information presented was based on leaving the PCRV at pressure (340 psig) as this represented the worst ,%

case condition for heat flux to the PCRV liner.

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"* As a. supplement to these calculations, and recognizing that PSC would depressurize the PCRV following an LOFC, additional calculations with the PCRV depressurized have been performed. The'results of these 1 calculations, as shown in Table ~1, confirm our original position that i leaving the PCRV pressurized represents the worst case for the PCRV liner.

The peak and. average fuel temperatures increased for ~the i i

depressurized versus pressurized conditions,-as ~would be expected,

but remain well below the fuel damage threshold of 2900 degrees

! Fahrenheit.

1 The controlling liner temperature parameter is improved in the depressurized case versus the. pressurized case (approximately 35

! hours to reach 400 degrees Fahrenheit liner temperature depressurized j versus approximately 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> to reach 400 degrees Fahrenheit liner i temperature pressurized).

1 The . follow-on calculations confirm our original contention that the q pressurized condition represents the worst case scenario. There are no changes to our previous conclusions that adequate time is I available to manually establish PCRV liner cooling including depressurization.

Operating procedures' have been developed on the basis of depress rizing the PCRV.

4 This information is being submitted to clarify the temperatures for j both the pressurized and depressurized conditions. If you have any j question or require any ~ additional information please contact M. H. Holmes at (303) 571-8409.

Very truly yours,

{

D.m irm D. W.'Warembourg, Manager Nuclear Engineering Division DWW:pa 4

Attachment i ,

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. Attachment to-

'. P-85333

's TABLE 1 FORT ST. VRAIN STATION TEMPERATURES OF FUEL / LINER FOLLOWING AN LOFC DESIGN BASIS EVENT FROM 8% POWER UTILIZING LINER COOLING PARAMETER PCRV PRESSURIZED PCRV DEPRESSURIZED ONE LINER COOLING LOOP ONE LINER C0OLING LOOP Peak Fuel Temperature 938 degrees Fahrenheit 1281 degrees Fahrenheit at 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> decreasing at 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> (still thereafter ,

increasing at 0.26 de Fahrenheit per hour) grees Core Average Temperature 726 degrees Fahrenheit 836 degrees Fahrenheit at 55 hours6.365741e-4 days <br />0.0153 hours <br />9.093915e-5 weeks <br />2.09275e-5 months <br /> at 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> (still increasing at 0.5 degrees Fahrenheit per hour)

Liner Temperature 140 degrees Fahrenheit 129 degrees Fahrenheit PARAMETER PCRV PRESSURIZED PCRV DEPRESSURIZED-NO LINER COOLING NO LINER COOLING Fuel Temperature 1034 degrees Fahrenheit 1332 degrees Fahrenheit at 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> (still at 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> (still i increasing at 0.5 de increasing at I degree Fahrenheitperhour)grees Fahrenheit per hour) l Core Average Temperature 850 degrees Fahrenheit 963 degrees Fahrenheit at 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> at 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> (still increasing at 1.75 de

, Fahrenheit per hour) grees Liner Temperature _400 degrees Fahrenheit 400 degrees Fahrenheit at 20 hour2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />s- at 35 hours4.050926e-4 days <br />0.00972 hours <br />5.787037e-5 weeks <br />1.33175e-5 months <br /> l

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