ML20086R728

Responds to Request for Addl Info Re Proposed Amend to Limiting Condition for Operation 4.1.9 Re Average Core Temp During Shutdown

ML20086R728
Person / Time
Site:	Fort Saint Vrain
Issue date:	02/24/1984
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Johnson E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
P-84062, TAC-52634, NUDOCS 8403010101
Download: ML20086R728 (3)

Text

,M9 Public Service Company E' Cdcuda g

Q fII 16805 WCR 19 1/2, Platteville, Colorado 80651 V

February 24, 1984 Fort St. Vrain Unit #1 P-84062 Mr. E. H. Johnson, Chief S@S0W2 %

Reactor Project Branch 1 i

U.S. Nuclear Regulatory Commission Region IV FEB 2 71984 611 Ryan Plaza Drive, Suite 1000

'p Arlington, TX 76011 DOCKET NO.:

E0-267

SUBJECT:

Additional Information on Proposed Amendment LCO 4.

1.9 REFERENCES

(1) PSC Letter, Loe to Collins, Dated December 15, 1983 (P-83403)

(2) NRC Letter, Johnson to Lee, Dated January 20, 1984 (G-84028)

Dear Mr. Johnson:

'This letter is in response to your request for further information (G-84028) regard'.1g our proposed amendment to LC0 4.1.9 (P-83403).

1.a.

"How is the average core temperature measured to ensure that, during shutdown, the limit of 760F is not exceeded?"

PSC performs an explicit calculation prior to initiation of a planned terminatic., of forced circulation to conservatively estimate the time available before the fuel temperature would exceed 760 F.

This calculation is performed by conservatively assuming that (1) decay heat generated after shutdown is retained by the active core (i.e.,

no convective, conductive, or radiative heat loss to reflector blocks or PCRV internals occurs),

(2) the specific heat capacity of the active core remains constant with increasing temperature-(the specific heat capacity increases with increasing temperature), and (3) the core

/

heat ger.eration rate remains constant during the period of no circulation (heat generation rate decreases as time D

elapses). u\\{)l i ' 8403010'101 840224 ( PDR ADOCK 05000267 \\ P PDR 1-

f.a. *. 1.b. "How 'does the 760F limit on average core temperature relate to the 760F helium inlet temperature limit required to prevent damage to reactor internals?" It is conservatively. assumed that by limiting the fuel temperature to 760 F, that the core inlet temperature will not be' in excess of the design core inlet temperature of .762 F. It should be noted that operation for extended time periods at the design core inlet temperatere does not ' imply the. onset of damage to plant internals. 1.c. " Explain 'the possible damage which could occur to the reactor internals if the 760F inlet temperature is exceeded." ' As noted above, 762 F is the design core inlet temperature for rated load conditions. Reactor internals are designed and seleci.ed for continuous operation at temperature. No damage is anticipated from short. term operation at temperatures in excess of 760 F following restart of -forced circulation. -2. "The analyses are based on orifice valve positioning of betweer. 20% and 8% open (for seven column regions) while LCO 4.1.9 is based on either equal orifice valve settiags or a limitir:g region temperature rise. How are the analyses and the limit tion correlated?" As specified in tha proposed amer.dment to LC0 4.1.9, Figure 4.1.9-1~ is applicable to situations where the orifice valves ai e set for equal

flows, not equal positions. As. described on page 5 of Attachment 2 of the PSC submittal. of proposed amendments to LCO 4.1.9 (P-83403), the GA Technologies analysis for Figure 4.1.9-1 was performed over a range of conceivnble equal flow orifice positions. The purpose of stating a 7 column orifice position of 8% to'20% is to provide a baseline for determination of the 5 column orifice position. The means for determination of equal flow valve settings is described in Systein Operating Procedures.

It was determined by GA Technolqies that the setting of 20%.(for - a 7 column region) was the limiting case for this range of values. Tnis setting is considerably more open than the " routine" orifice valve position of 13% (7 column region, 10% on a 5 column region) generally utilized at FSV. k

}l:,. 1*

The analysis utilized in generati.,g of LC0 4.1.9-2 limits determined the maximum temperature rise allowable without

-specific reference to orifice valve positions. The analysis assumed that region orifice valves were adjusted per the region power distribution to produce approximately equal regios. exit temperatures. The temperature rise determined was that which precluded flow stagnation for the most' critical coolant channel (highest power channel in the lowest power region). This analysis is described in detail on page 10 of Attachment 2 to P-83403. If you have further questions regarding this matter, please contact - Frank Novachek at (303)785-2223. Very truly yours, a

0.., W. - Js m. L. n,

92 ya Don W. Warembourg Manager, Nuclear Production DWW/dkh 1 4 4 L .}}