ML20137X219

Issue 2 to CMG-4, Decay Heat Calculations

ML20137X219
Person / Time
Site:	Fort Saint Vrain
Issue date:	04/16/1985
From:	PUBLIC SERVICE CO. OF COLORADO
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ML20137X216	List: ML20137X211 ML20137X219
References
CMG-4, NUDOCS 8603050290
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~-

PUBLIC SERVICE COMPANY CF COLCRAD'S CMG-4 I

FORT ST. VRAIN NUCLEAR GENERATING STATION TITLE: DECAY HEAT CALCULATIONS ISSUANCE AUTHORIZED REV EW PORC 616 APR 9 :1985 EATE 4- l[o-tS-1.0 PURPOSE The purpose of this procedure is to perform temperature and time l calculations for various decay heat conditions. Due to the l absence of in-core temperature detectors when forced primary l coolant flow is lost core temperatures must be calculated.

2.0 APPLICABILITY l This procedure is applicable whenever forced primary coolant I flow is lost and core temperatures cannot be determined from l region outlet temperatures.

This procedure is used to calculate the following:

2.1 The increase in fuel temperature due to decay heat knowing how long forced primary coolant flow has been, or will be off.

2.2 The number of hours forced cooling may be suspended knowing maximum fuel temperature to be allowed.

2.3 The time after shutdown when forced cooling can be suspended knowing how long the flow will be off and the maximum fuel temperature to be allowed.

l 86030%$h POR p

P annu sn.n. sus .

1

CMG-4 Issue 2

. Public FORT ST. VRAIN NUCLEAR GENERATING STATION Page 2 of 8 0 Service

• PUBUC SERVICE COMPANY OF COLORADO 3.0 GENERAL REQUIREMENTS l The procedure addresses two types of calculations, a theoretical l calculation based on data provided by the NSSS and an empirical l calculation based on empirical data collected during a previous

-l loss of forced primary coolant flow during the same reactor l shutdown. These calculations are based on the following l parameters and theory.

3.1 Heat Transfer l The theoretical procedure assumes that decay heat generated after shutdown is retained in the active core, i.e., no convective, conductive, or radiative heat transfer to reflector or PCRV internals.

l The empirical calculation does not use this assumption as l it collects actual data and there is heat transfer inside l the reactor.

3.2 Specific Heat Capacity. C p

l The theoretical procedure assumes the specific heat capacity of the active core, C, p remains constant with increasing temperature. In reality, C, increases with increasing temperature. Thus, assuming C remains p

constant yields calculated temperatures that are higher than the actual temperatures.

l The empirical calculation does not use this assumption as l it collects actual data and the specific heat capacity of l the core does increase with temperature.

3.3 Heatup Rate l The theoretical procedure assumes the heatup rate is constant. Actually, the heatup rate decreases with time l due to the increase in specific heat capacity and heat l transfers as temperatures increase.

l The empirical procedure makes the same assumption to l provide for conservatism in the calculation.

I FORMtCl372 22 3843 I

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CMG-4 Issue 2

. Public FORT ST VRAIN NUCLEAR GENERATING STATION Page 3 of 8 0 $9fVIC9' PusuC ssRVICs COMPANY OF COLORADO 3.4 Active Core Volume and Density l The theoretical procedure assumes the active core volume and density remain constant as the temperature changes.

- l The empirical procedure does not use this assumption as it l collects actual data and therefore accounts for any change l in volume or density.

3.5 Theory l The theoretical heatup rate of the core can be determined by considering the shutdown core power density and the core heat capacity. The volumetric heat capacity of the core is pCp (in BTU /ft' *F) per Figure 1.

p = active core density = 90 lb/ft' C, = core specific heat (in BTU /lb *F) per Figure 1 Knowing the shutdown core power density (P/V) and the volumetric heat capacity, the heatup rate, R, can be determined.

R = k(P/V) = 3.414 x 10' BTU (P/P ]Q g pC MW-Hr pC p p where:

P = decay heat generation rate (in MW)

P, = average power level before shutdown (in MW)

V = active core volume (4,694 ft )8 P/P, = normalized decay heat P,/V = core thermal power density prior to shutdown (MW/ft')

K = conversion factor for BTU's and MW-hrs R = heatup rate (*F/hr)

FORMICl372 22 3M3

c.

Cl%-4 Issue 2 FORT ST VRAIN NUCLEAR GENERATING STATION .oa ge & of 8 0PubHe Service ~ eunuc suavica comeAc w caonano -

Sr.;bstitt.te known values:

R = 3.414 x 108 (P/Po l(P /4694) = 8.08(G/P,)(P /Cp )

90 C P

~{ The erpirical Seatup rate can be detemined by considering

( the t.ure temperature rise and the time interval of a j previcus loss of forced primary coolant flow during the i sue reactor shutcwn.

l Tv - T1 i R4- ~

l At l Where:

l R = = Heattg rate (*F/HR.)

l Ti = Average core outlet tecperaturg prior i to LOFC. -

l Te -e Avarage core region outbt t.emperature l after resumptio' of forcea coo 11ns.

I At , d;tration o.f wh LoFC. d 4.0 PROCEDURE l 4.1 FUEL TEM?ERATURE GIVEN_DURATICg i

Calculating the fuwd temperature knoning how long forced cooling flow has been, or will be, of f. Use Data %eet 1.

4.1.1 rrom Figure 1, detemine .cp cring the fuel temperature et the time foremi coolhg flow was ,

shut off. If the flow will be shut of tr the '

futoe, use the projected fuel temperatu.e, 4.1.2 From the ther<.41 gwer history 2nd the titre af ter int.tdown, determine P/P, (from Figure 2), and P, 't ,

MW.

4.1.3 Using P,, P/P,, and C , determire the heat 0 rate:

p 4.1.4 The heatup rate, R, multipligd by the tic.e that -

rate is in effEct, t, yields tf.t i.amperature ritt.  ;

T 7 ,3,

= Rt l

(

FORM (C)P2 M 3043

CMG-4 Issue 2 FORT ST. VRAW NUCLEAR GENERATING E7ATION Page 5 of 8 0Public$9tVIC9' Pusuc senvma CCMPANY OF COLORADO 4.1.5 Fuel tempe.ature -

is equal to the initial fuel temperature (used in 4.1.1 above) .plus the tercerature rise.

T fuel " initial + T793, 4.1.6 Attachment CMG-4B problems 1 and 2 cent.tta sample calculations.

l 4.2 OURATION GIVEN FUEL TEMofRATUAE _

Calculat,ing the hours forced cooling may be shut off knowing the maximun fuel temperature to be allowed. Use Data Sheet 2.

4.2.1 Deterrnine R as in 4.1.1 through 4.1.2 above.

4.2.2 Determine the temperature rise by subtracting the initial fuel temperature from the maximum fuel temperature to be allowed.

rise = t,,, - Tinitial 4.2.3 Divice T rise by R to determine the time.

t=Trise/N 4.2.4 Attachment CMG-48 problem 3 contains a sample calculation.

4.2.5 Cocplete Attachaerst CMG-40 if information fs requested by Operations. Transmit completed Attachrent CMG-40 and a copy of the completed data sheets to . Operations, t 4.3 TIME AFTER SHUTCOWN COOLING MAY PE SHUT 0FF _GIVEN DURATION Calculatirg the time after shutdown that forced cooling nay be shut off. Use Data Sheet 3.

NOTE: This calculation assumes that forced cooling will be restorad after t hours.

4.3.1 Estimate the fuel temperature at the time forced cooling will be shut off, T gn$tg,j, l

l L

l 1

(

W utes m .n 3mc

CMCr4 Issue Z FORT ST, VRAtti NUCLEAR GENERATINC STATION ptge 6 of 8 0Public Service ~ pusue sanvma comeAny or cotoriano 4.3.2 Estimate Cp using the fuel temperature from 4.3.1 above.  :

4.3.3 Determine the maximum fuel temperature that wf11 be allowed, T,,,,

4.3.4 Calculate the temperature rise, Trise, rise n&t initial 4.3.5 Using the tenperature rf se and the number of hcurs that cooling flow will be off, celeolate the average heatup rate, R.

R=Trise/t 4.3.6 Using the average power level prior to shutdown, P,, calculate P/P,,

P/P, = .124RCp /P, .

4.3.7 Using P/P 9 and the nours at constant power, find the-time after shutdown that cooling flow may be shut off from Figure 2.

4.3.8 ettachment CMG-48 problem 4 contains a sample calculation.

l 4.4 _ DURATION GIVEN EMPIRICAL WEAT Up RATE I Calculating the hours that forced cooling may be I terminated knowing the maximum fuel temperature to be j allowed utilizing an empirically determined Heatup l Rate (R).

1 4.4.1 From a recent termination of forced circulation I during the current plant outage for which this

{ oecay heat calculation is being performed collect i data upon circulator restart WITHOUT SECCNBARY FLOW l as follows (see Data Sheet 4):

l 4.4.1.1 Duration of the LOFC (hours) that will be l utilized to determine heatup rate R; At I (hours).

l 4.4.1.2 Average core region outlet t eperature 1 (*F) immediately prior to the onset of l the LOFC to be used to evaluate R; Ti.

FoAwc)m 22.M*3

CMG-4 Issue 2 PubHe FORT ST. VRAIN NUCLEAM CENERATiNG STATION page 7 of a 0 Service ~eveuc seawce comraw or cotoneo l 4.4.1.3 Equiliertue aversga region outlet j temperature (

• F) estabi t shed followinn

[ the resumption of active cera cooling l following the LOFC to be ased to evaluate j R; Te.

l 4.4.1.4 Evaluate the empirically detercioed core l heatup rate (R) as shown;

( R = Te - Ti (*F/hr) l At l 4.4.2 De termir.e the temperature rise to be allowed I

J (T rise) based upon the initial temperature for the j anset of the LOFC for which this calculaticn is l being performed (T initial) and the maximum fuel I temperature to be allowed (T max).

4.4.2.1 from plant operating data, determine the l average region outlet temperature

-) ectresponding to that at the ceset of the '

l LDFC for which this calculation is being 1 l performed (T initial).

l 4.4.2.2 Determine the maximun feel temperature to l be alicwed (7 max). If fuel temperautre l (T max) is restricted to s400*F, then ths l ceder in which primary and secondary flow l are restarted is not restricted (see l sectico 1.2.! and 1.2.3 of Attachment j CMG-40 of this procedure). The second l threshold limit applied to the maximum

( fuel temperature is 750'F, corresponding l to the design core inist tecperature (see i section J.2.2 of Attachment CMG-40 of l this procedure).

l 4.4.2.3 T rise = T max - T initfal i

l 4.4.3 Divide T rise by R to determine the allowable i duration of the planned LOFC.

I t = T rise /R 1

$ M h M 'M .N

CMG-4 Issue 2 Public romT sT. VRAIN NUCLEAR GENERATING STATION Page 8 of 8 0 Service ~ rueuc senvma compan or cotonAno l 4.4.4 Complete Attachment CMG-4D if this calculation is l being provided to Operations in support of a 1 olanned LOFC. Transmit the completed Attachment j CHG-40 and retain a ecpy in the Technical Services l Engineering files, as approprfate.

5.0 REFERENCES

. 5.1 FSAR Appendix D 5.2 FSVA 327:77 6.0 ATTACHMENTS 6.1 CMG-4A Figures I sad 2 6.2 CMG-48 Sanole Problems t 6.3 CMG-4C Data sheets 1, 2, 3, and 4 i 6.4 CMG-40 Instructions to Operators 4

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FOAM (C)372 2[ 3H3

Attach. CMG- O Iss o 2 FoaT sr. VRAiN NUCLEAR GENEATING STATION page 1 of 6 OPublic ServlCW" Putsuc senVICE COMPANY OF COLORADO SMPLE PROSLEM SCENMIO s

Sample Freblem 1 (Data Sheet 1) '

Twenty hours af ter shutdown from operaticg at 50% power for favr

_ days, coolant flow was lost. At that time, the fuel temperature was 300*F. What is the present fuel temperature, if coolant flow has been off for four hours?

Sample Problem 2 (Data Sheet 1)

The reactor har been operating at 68% power for 17 days. Two i hours after shutdown, primary coolant ficw is lost. If the fuel '

temperature at that tire 1s SSO'F. what will the fuel temperature be after 30 minutes without flow?

Sample Problem (Data Sheet 2)

The reactor was shutdown from a 40%/400 power run at 10:00 am.

Maintenance requires coolant flow be shut off at 8:00 the following morning. How long can the maintenance taAe if ths -

naximum fuel temperature to be allowed is 760'F? 3 Sample Problem 4 (Data Sheet 3)

How many hours after shutdown may ecoling flow be shut off, if maintenance requiring 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> to complete is to be performed, The reactor had been operating at 50% power for four days. The maximum fuel temperature to be allowed is 760'F.

Sample Problem 5 (Data Sheet 4) l The reactor is shutdown. On a previous LOFC (occurring during

) this shutdown), the average region outlet temperature prior to j the LOFC was 94*F. At the end of the 134.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> LCFC, the

) 6verage core outlet temperature was 232*F. How long can forced l cooling be off if the average region outlet temperature prior to l this LOFC is 185'F and the maximum temperature to be allowed is l 400*F?

l FOAM !Cs Jf2. U 3e43 l

Attach. CMG-48 Issue 2 FORT ST. VRAIN NUCLEAR GENERATING STATION Page 2 of 6 0Public Service ~ rusue senvice comeAm or cotonApo DATA SHEET 1 CALCULATING THE FUEL TEMPERATURE (KNOWING HOW LONG FLOW IS OFF)

1. Initial Conditions a) Date/ Time of reactor shutdown 2-1-79/1000 b) Average Power before reactor shutdown, P,, P, = 421 MW c) Hours at constant power. - 100 Hrs.

d) Hours after reactor shutdown when flow was/will be shut off, At. At = 20 Hrs.

e) Fuel temperature at time of flow shut off, Tinitial. 300*F f) Cp from Figure 1 using T inttial Cp = 0.21

[ BTU /lb.*F g) P/P, from Figure 2 using At and c. P/P, = 0.0021

2. Calculate the heatup rate, R:

R = 8.08(P/P,)(P,/Cp )

= 8.08(0.0021) (421)

= 34*F/hr.

(0.21)

3. Calculate the fuel temperature, T fuel.

Forced cooling flow has been, or will be, off for At = 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

Trise = Rat = (34)(4) = 136*F Tfuel = Tinitial + Trise

= 300 + 136

= 436*F Calculation by:

Reviewed by:

Date/ Time:

muscom n see

Attach, CMG-4B Issue 2 Public FORT ST. VRAIN NUCLEAR GENERATING STATION Page 3 of 6 OServ!ce~ pusuc sanvoca comeAny or cotonaoo DATA SHEE~T 1 CALCULATING THE FUEL TEMPERATURE (KNOWING HOW LONG FLOW IS OFF)

1. Initial Conditions

a) Date/ Time of reactor shutdown. 1-23-78/1100 b) Average Power before reactor shutdown, P,, P, = 573 MW c) Hours at constant power. 408 Hrs.

d) Hours after reactor shutdown when flow was/will be shut off, At. At = 2 Hrs.

e) Fuel temperature at time of flow shut off, Tinitial. 550'F f) Cp from Hgure 1 using T initial Cp = 0.27 BTU /lb.*F g) P/P, from Figure 2 using at and c. P/P, = 0.0095

2. Calculate the he.atup rate, R:

R = 8.08(P/P )(P,/Cp )

= 8.03(0.0095) (573)

= 163"F/hr.

(0.27)

3. Calculate the fuel temperature, T fuel.

Forced cooling flow has been, or will be, off for at = 0.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.

Tg 3, = Rat = (163)(0.5) = 82*F Tfuel = Tinitial + Trise = e +T rise

= 550 + 82

= 632*F Calculation by:

Reviewed by:

Date/ Time:

romicim-22.aso

Attach. CMG-48 Issue 2 Public FORT ST. VRAIN NUCLEAR GENERATIN3 STATION Page 4 of 6 0 Service ~ pusuc senvice couramy or cotonaoo 0ATA SHEET 2 CALCULATING THE HOURS FORCEO COOLING MAY BE OFF (KNOWING MAXIMUM FUEL TEMPERATURE TO BE ALLOWEO)

- 1. Initial Conditions a) Date/ Time of reactor shutdown. 12-12-78/1000 b) Average Power before reactor shutdown, P,, P, = 337MW c) Hours at constant pcwer. ~400 Hrs.

d) Hours after reactor shutdown when flow was/will be shut off. At = 22 Hrs.

e) Fuel temperature at time of flow shut off, Tinitial. 250'F f) Cp from Figure 1 using T initial Cp = 0.19 BTU /lb.'F g) P/P, from Figure 2 using at and c. 0.0037 -

2. Calculate the heatup rate, R:

R = 8.08(P/P,)(P,/Cp )

= 8.08(0.0037) (337)

= 53'F/hr.

(0.19)

3. Calculate the hours forced cooling may be o'ff.

The maximum fuel temperature to be allowed, T,,,, is 760'F.

T793, = T,,x - Tinitial = 760 - Tinitial = 510'F t=Trise/R = (510)/R = 9.6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> Calculation by:

Reviewed by:

Date/ Time:

FORMtCl372 22 3843

Attach. CMG-4B Issue 2 Public FORT ST. VRAIN NUCLEAR GENERATING STATION Page 5 of 6 OService~ rusuc senvice couramy or cotonaoo 0ATA SHEET 3 CALCULATING THE TIME AFTER SHUTDOWN THAT '

COOLING FLOW MAY BE SHUT OFF

1. Assumotions a) Projected initial fuel temperature.

Tinitial = 200 F b) Estimated Cp from Figure 1 using T initial Cp = 0.175 BTU /lb'F c) Average power pr1or to shutdown, P,. P, = 421 MW d) Hours at constant power. -100 Hrs.

e) Maximum fuel temperature to be allowed. T,,, = 760 F f) Estimated hours flow will be off, At. At = 30 Hrs.

2. Calculate the temperature rise, T rise

• Trise = T,,, - Tinttial

= 760 - 200 = 560*F

3. Calculate the allowed heatup rate, R.

R=Trise/at

= (560) / (30) = 18.7'F/hr.

4. Calculate P/P, P/P, = .124 RCp /P,

= (.124)(18.7)(0.175)

= 0.0010 (421)

5. Using P/P, and d, find the time after shutdown that flow may be shut off from Figure 2.

Time after shutdown = 70 Hours.

Calculation by:

Reviewed by:

Date/ Time:

l l

FORM (C1372 22.JS43 j

Attach. CMG-48 Issue 2 Public FORT ST. VRAIN NUCLEAR GENERATING STATION Page 6 of 6 0 Service ~ punuC SERVICE COMPANY OF COLORADO DATA SHEET 4 I CALCULATING THE dOURS FORCED COOLING MAY BE OFF (KNOWING THE MAXIMUM l FUEL TEMPERATURE TO BE ALLOWED) AND UTILIZING AN EMPIRICALLY l DETERMINED CORE HEATUP RATE (R).

- l NOTE: This shall be data collected for a case where equilibrium l region octlet temperature was established prior to resumotion l of secondary coolant flow.

l 1. Preliminary Information l a) Date/ Time of reactor shutdown. 6-23-84/0031 l b) Date/ Time of previous LOFC data that is to be utilized to l determine heatup rate (R). 1-21-85/1930 l c) Duration of previous LOFC (hours) that is to be utilized l to determine heatup rate (R); At = 134.5 HOURS.

l d) Average region outlet temperature (*F) immediately prior l to onset of the previous LOFC that is to be utilized to l determine heatup rate (R); T, = 94*F.

l e) Equilibrium region outlet temperature (*F) established l after the resumption of active core cooling following the .

I previous LOFC that is to be used to determine heatup rate l R; T, = 232*F.

l f) Average region outlet temperature at the start of the l current or projected LOFC for which this calculation is l being performed; T9nggg,) = 185"F.

I g) Maximum fuel temperature to be utilized in this I calculation of LOFC time duration; T,,, = 400*F.

l 2. Calculate the heatup rate (R):

l R = (Te - T1) = (232 - 94) = 1.03*F/HR l At ( 134.5 )

l 3. Calculate the hours forced cooling may be off, t: i l T rise = T max - T initial = 400 - 185 = 215 F l t = T rise /R = 215/1.03 = 209 (Hours) l Calculation by:

l Reviewed by:

l Date/ Time:

l l

l l

FoRMtC1372 22 3843

Attach. CMG-4C Issue 2 Public FORT ST. VRAIN NUCLEAR GENERATING STATION Page 1 of 4 0 Service ~ pusuc sanwes compam or cotonAno DATA SHEET 1 CALCULATING THE FUEL TEMPERATURE (KNOWING HOW LONG FLOW IS OFF)

1. Initial Conditions a) Date/ Time of reactor shutdown l b) Average Power before reactor shutdown, P,, P,= MW c) Hours at constant power. Hrs.

d) Hours after reactor shutdown when flow was/will be shut off, At. At= Hrs.

e) Fuel temperature at time of flow shut off, T F initial.

l f) Cp from Figure 1 using T initial P*

BTV/l b.* F l g) P/P, from Figure 2 using At and c. P/P,=

2. Calculate the heatup rate, R:

R = 8.08(P/P,)(P,/Cp )

= 8.08( )( )

=

• F/hr.

( )

3. Calculate the fuel temperature, T fuel.

Forced cooling flow has been, or will be, off for At = hours.

T rise = Rat = ( )( )= *F Tfuel = Tinitial + Trise

= +

= *F Calculation by:

Reviewed by:

Date/ Time:

rowicim.22.ase

1 I

l Attach. CMG-4C Issue 2 Public FORT ST. VRAIN NUCLEAR GENERATING STATION Page 2 of 4 O service

• Pusuc SERVICE COMPANY OF COLORADO DATA SHEET 2  !

CALCULATING THE HOURS FORCED COOLING MAY BE OFF (KNOWING MAXIMUM FUEL TEMPERATURE TO BE ALLOWED)

1. Initial Conditions a) Date/ Time of reactor shutdown l b) Average Power before reactor shutdown, P,, P,= MW c) Hours at constant power. Hrs.

d) Hours after reactor shutdown when flow was/will be shut off. At= Hrs.

e) Fuel temperature at time of flow shut off, T F initial.

l f) C, from Figure 1 using Tinitial C=p BTU /lb. F g) P/P, from Figure 2 using At and c.

2. Calculate the heatup rate, R:

R = 8.08(P/P,)(P,/Cp )

= 8.08( )( )

= F/hr.

( )

3. Calculate the hours forced cooling may be off.

The maximum fuel temperature to be allowed, T,,,, is

• F.

Trise = T,,x - Tinitial = -

T initial = F t=Trise/R = ( )/R = hours Calculation by:

Reviewed by:

Date/ Time:

FonMICl372 22-384 r- g--

Attach. CMG-4C Issuo 2 Pucilc FORT ST. VRAIN NUCLEAR GENERATING STATION Page 3 of 4 0 Service ~ rusuc sanvics comramy or cotonApo DATA SHEET 3 CALCULATING THE TIME AFTER SHUTDOWN THAT COOLING FLOW MAY BE SHUT OFF

1. Assumotions I a) Projected initial fuel temperature T F initial =

l b) Estimated C p from Figure 1 using T C=

initial p BTU /lb F l c) Average power prior to shutdown, P,. P,= MW d) Hours at constant power. Hrs.

l e) Maximum fuel temperature to be allowed. T,,,= F l f) Estimated hours flow will be off, At. At= Hrs.

2. Calculate the temperature rise, T rise' I

rise = T,,, - Tinitial

= - = 'F

3. Calculate the allowed heatup rate, R.

l R=Trise/at

=( )/( )= "F/hr.

4. Calculate P/P, l

P/P, = .124 RCp /P, l

= (.124)( )( ) l

= '

( )

5. Using P/P, and d , find the time after shutdown that flow may be shut off from Figure 2.

Time after shutdown = Hours, l

Calculation by:

Reviewed by:

Date/ Time:

FORMiCi372 22 36G

Attach. CMG-4C Issue 2 Public FORT ST. VRAIN NUCLEAR GENERATING STATION page 4 of 4 0SerVIC9"' PusuC SERVICE COMPANY OF COLORAN DATA SHEET 4 l CALCULATING THE HOURS FORCED COOLING MAY BE OFF (KNOWING THE MAXIMUM l FUEL TEMPERATURE TO BE ALLOWED) AND UTILIZING AN EMPIRICALLY

_ l DETERMINED CORE HEATUP RATE (R).

l NOTE: This shall be data collected _ for a case where equilibrium l reoion outlet temperature was established prior to resumDtion l of secondary coolant flow.

l 1. Preliminary Information l a) Date/ Time of reactor shutdown.

l b) Date/ Time of previous LOFC data that is to be utilized to l determine heatup rate (R).

l c) Duration of previous LOFC (hours) that is to be utilized i to determine heatup rate (R); At = HOURS.

I d) Average region outlet temperature (*F) immediately prior I to onset of the previous LOFC that is to be utilized to l determine heatup rate (R); Tg= *F.

I e) E:uilibrium region outlet temperature (*F) established l after the resumption of active core cooling following the l previous LOFC that is to be used to determine heatup rate l (R); T, = *F.

l f) Average region outlet temperature at the start of the I current or projected LOFC for which this calculation is l being performed; T F.

initial =

l g) Maximum fuel temperature to be utilized in this I calculation of LOFC time duration; T = F.

max l 2. Calculate the heatup rate (R):

l R = (Te - Ti) = ( -

)= *F/HR l At ( )

l 3. Calculate the hours forced cooling may be off, t:

l T rise = T max - T initial = - = *F l t = T rise /R = / =

(hours) l Calculation by:

l Reviewed by:

l Date/ Time:

FORMICI272 22 3M3

Attach. CMG-40 Issue 2 o Public FORT ST. VRAIN NUCLEAR GENERATING STATION Page 1 of 2 0 $9tVlCO* PUBUC SERVICE COMPANY OF COLORADO INSTRUCTIONS TO OPERATORS 1.0 OISCUSSION DATE: / / CORE INLET TEMP: BY:

Reviewed by:

1.1 When primary flow is shut off, region outlet temperature readings are not a reliable indication of the fuel temperatures. Therefore, decay heat calculations that are based on the most restrictive recent power history are performed.

1.2 Usually, calculations are performed for the two different maximum fuel temperatures that are allowed. Those two fuel temperatures are 400*F and 760*F.

1.3 400*F fuel temperature -

Secondary flow is not to be restarted to the steam generators if the steam generator

~

tube temperatures are greater than 400*F. The steam generator tube temperatures cannot exceed 400*F if the maximum fuel temperature allowed is less than or equal to 400*F. Therefore, if primary coolant flow is off for less than the time required to reach 400*F, the order in which primary and secondary flow is restarted is unimportant.

1.4 760*F fuel temperature -

The design maximum core inlet temperature is 760*F, if the maximum fuel temperature allowed is less than or equal to 760*F, the design core inlet condition cannot be exceeded.

1.5 Note that if primary flow is off more than the amount of time determined by the 400*F fuel temperature limit, then secondary flow must be restarted before primary flow. This will prevent damaging the steam generator tubes.

2.0 TIME LIMITS AND ACTIONS 2.1 Limit based on maximum fuel temperature of (5400*F). If primary flow is off for less than hours, then the order in which primary and secondary flow is restarted is unimportant. If primary flow is off for more than hours, then secondary flow must be restarted before primary flow. hours equals days and hours.

FORMIC 1372 22 3883

Attach. CMG-4D Issue 2 FORT ST. VRAIN NUCLEAR GENERATING STATION Page 2 of 2 0Public Service ~ pusuC SERVICE COMPANY OF COLORADO 2.2 Limit based on maximum fuel temperature of (s760'F). Primary flow MUST be restarted within hours from the time it is first shut off.

hours equals days and hours.

UNDER NO CIRCUMSTANCES SHOULD THIS TIME LIMIT BE EXCEEDED.

2.3 If more time is required, proceed as follows:

l 2.3.1 Return to original conditions.

a) Retstart secondary flow, b) Restart primary flow.

c) Decrease fuel temperature until (T in + T out)/2 is less than 'F.

d) Primary and secondary flow may then again be shut off and the " clock" is reset, i.e., the 400'F and 760*F time limits above nay be used again. ,

l 2.3.3 Recalculate decay heat.

l a) Request Technical Services to reevaluate decay I heat using current conditions.

. 1 roamacis72 22 ano

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