ML20083Q064

Rev 1 to Licensing Rept on Spent Fuel Storage Racks

ML20083Q064
Person / Time
Site:	Summer
Issue date:	04/09/1984
From:	SOUTH CAROLINA ELECTRIC & GAS CO.
To:
Shared Package
ML20083Q051	List: ML20083Q049 ML20083Q064
References
NUDOCS 8404200314
Download: ML20083Q064 (28)

Text

..

1

~

l 2

i LICENSING REPORT ON SPENT FUEL STORAGE RACKS FOR THE VIRGIL C.

SUMMER NUCLEAR STATION 4

i NRC DOCKET NO. 50-395 i

l SOUTH CAROLINA ELECTRIC AND GAS COMPANY COLUMBIA, SOUTH CAROLINA 29218 DECEMBER 1983

+

4 REVISION I APRIL 9, 1984 1

1 l

i k0 5

PDR p

3..

' *~

t Rev. 1 (4/9/84) 5.

THERMAL-HYDRAULIC CONSIDERATIONS s

A central objective in the design of the high-density fuel rack is to ensure adequate cooling of the fuel assembly cladding.

In the following, a brief synopsis of the design basis, the method of analysis, and computed results are given.

Similar analysis has been used in previous licensing reports on high density spent fuel racks for Fermi II (Docket 50-341), Quad Cities I and II (Dockets 50-254 and 50-265), Rancho Seco (Docket 50-312), Grand Gulf Unit 1 ( Docket 50-416), and Oyster Creek (Docket 50-219).

5.1 Decay Heat Calculations for the Spent Fuel This report section covers requirement III.l.5(2) of the NRC "OT Position for Review and Acceptance of Spent Fuel Storage and Handling Applications" issued on April 14, 1978.

This requirement states that calculations for the amount of thermal energy removed by the spent fuel cooling system shall be made in accordance with Branch Technical Position APCSB 9-2 " Residual Decay Energy for Light Water Reactors for Long Term Cooling"1 The calculations contained herein have been made in accordance with this requirement.

5.1.1 Basis The V.C.

Summer Nuclear Station reactor is rated at 2775 Megawatt-Thermal (MWT).

The core contains 157 fuel assemblies.

Thus, the average operating power per fuel assembly, P

is o,

17.675 MW.

The fuel assemblies are assumed to be removed from the reactor af ter a maximum of 4.5 years of cumulative operating l time. The fuel discharge can be made in one of the following t o modes:

(i)

Normal discharge - Mode (i)

(ii) Full Core discharge - Mode (ii) j 5-1 l'

\\

R2v. 1(4/9/84)

As shown in Table 1.1, the anticipated fuel batch size for normal discharge may vary from 68 to 72.

Therefore, for analysis purposes, we assume the batch size to be 72 fuel assemblies.

The fuel transfer begins after 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br /> of cool-off time in the reactor (time after shut down).

It is assumed that the time period of discharge of this batch is 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

(One assembly transferred to the pool per hour). The cooling system consists of two seismic category I spent fuel cooling circuits.

The bulk temperature analysis assumes that one cooling train (out of two) is unavailable for cooling the pool water.

Mode (ii) corresponds to a full core discharge (157 assemblies).

Full core off-load condition implies that the reactor core has no remaining fuel. It is assumed that the total time period for the discharge of one full core is 52 hours6.018519e-4 days <br />0.0144 hours <br />8.597884e-5 weeks <br />1.9786e-5 months <br /> (after 144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br /> of shut down time in the reactor).

The discharge rate to the pool is assumed to be continuous and uniform. The bulk

, temperature analysis assumes two spent fuel pool coolers working in parallel.

Since the decay heat load is a monotonically increasing function of the cumulative reactor operating time,to, we assume that every fuel assembly discharged has had the maximum postulated to of 4.5 years.

The water inventory in the reactor cavity cooled by the RHR heat exchanger exchanges heat with the fuel pool water mass through the refueling canal.

This important source of heat removal is also neglected in the analysis.

Thus, the results obtained for both modes (i) and (ii) are highly conservative.

4 5-2

r e l-g I

In the following, all relevant performance data for the spent fuel pool heat exchangers is given.

a.

Spent Fuel Pool Heat Exchanger:

Type Tube and shell Quantity 2

Performance data o Heat transferred 14.02 x 106 Btu /hr Tube Side o Fluid flow 1,800 gpm o Pool water inlet temperature 135'F o Outlet temperature 119.2*F Shell side a

o Fluid flow 1800 gpm o Coolant inlet temperature 105*F o Outlet temperature 120.8'F o Fouling factor 0.0005 The above data enables complete characterization of the thermal performance of the fuel pool heat exchanger.

5.1.2 Model Description Reference (l) is utilized to compute the heat dissipation requirements in the pool.

The total decay power consists of " fission products decay" and " heavy element decay".

Total decay power P for a fuel assembly is given as a linear function of Po and an. exponential function of to and ts-i.e.: P = Po f(to,ts) where P=

linear function of Po 5-3 J

I T

o g

Po= average operating power per fuel assembly to= cumulative exposure time of the fuel assembly l

in the reactor ts= Time elapsed since reactor shutdown l

The uncertainty factor K,

which occurs in the functional relationship f

(to,ts) is set equal to 0.1 for ts >

107 sec in the interest of conservatism.

Furthermore, the operating power Po is taken equal to the rated power, even though the reactor may be operating at less than its rated power during most of the period of exposure of the batch of fuel assemblies. Finally, the computations and results reported here are based on the discharge taking place when the inventory of fuel in the pool will be at its maximum resulting in an upper bound on the computed decay heat rate.

Having determined the heat dissipation rate, the next task is to evaluate the time-temperature history of the' pool water.

Table 5.1.1 identifies the loading cases examined.

The pool bulk temperature time history is-determined using the first law of thermodynamics (conservation of energy).

A number of simplifying assumptions are made which render the analysis conservative.

The principal ones are:

1.

The cooling water temperature in the fuel pool cooler is based on the maximum postulated values given in the FSAR.2 2.

The heat exchangers are assumed to have maximum fouling.

Thus, the temperature effectiveness, s,

for the heat exchangers utilized in the analysis are the lowest ' postulated values:

S=

0.526 for-5-4

t e'

Rev. 1 (4/9/84) fuel pool

coolers, S

is calculated from heat exchanger technical data sheets.No heat loss is assumed to take place through the concrete floor.

4.

No credit is taken for the improvement in the film coefficients of the heat exchangers as the operating temperature rises.

Thus, the film coefficient used in the computations are lower bounds.

5.

No credit is taken for evaporation of the pool water.

6.

No credit is taken for heat loss to pool walls and pool floor slab.

The basic energy conservation relationship for the pool heat exchanger system yields:

C

= Q 03 (5.1.2) 1 t

di where C:

Thermal capacitance of stored water in the t

pool.

t:

Temperature of pool water at time, t 01:

Heat generation rate due to stored fuel assemblies in the pool.

01 is a known function of time, i from the preceding section.

Q2:

Heat removed. in the fuel pool cooler.

0:

Heat removed in the RHR heat exchanger 3

(Q3=0 if RHR is not used).

5-5

I,

,t Rev. 1 (4/9/84) 1 The pool has total water inventory of 38162 cubic feet when all -racks are in place in the pool and every storage location is occupied.

f 5.1.3 Decay Heat Calculation Results:

The calculations were performed for the pool disregarding the additional thermal capacity and cooling system available in the transfer channel, and the reactor cavity.

For a specified coolant inlet temperature and flow 1

rate, the quantities 02 and Q3 are shown to be linear function of t in a recent paper by Singh (3).

As stated earlier, Q1, is an exponential function of T.

Thus Equation (5.1.2) can be integrated to determine t directly as a function of T.

The results are plotted in Figures (5.1.1) to (5.1.2). l The results show that the pool water never approaches the boiling point under the most adverse conditions.

These figures also give 01 as a function of T.

Four plots are generated for 'each case.

The first and third plots for each. case shows temperature and power generation respectively for a period extending' from T=

I 0 + T = 2Tn where Tn is the total time of fuel transfer.

The second and fourth plots show the same quantities (i.e.

temperature and power generation respectively)- over a

long period.

The long-term plots are produced to indicate the required operating time for the heat exchangers.

Summarized results are given _ in Table 5.1.2.

It is noted that the maximum l

the normal mode discharge; pool bulk temperature corresponds, to

~than the this value.is 140*F.

This is significantly lower.

initial plant design basis of 150*F.

4 Finally, computations are made to determine the time interval tq i

lost.- Computations boiling af ter all heat dissipation paths are are made for-each case under the following two assumptions:

(i)

All cooling sources lost at the instant' pool bulk temperature reaches the maximum value.

5-6

i Rev. 1 (4/9/84)

TABLE 5.1.1 LIST OF CASES ANALYZED Case No.

Condition No. of No. of No. of Total Time Cool off time fuel spent fuel RHR's to transfer before transfer assemblies pool HXS in-service fuel into begins, hrs.

discharged the pool N

th, hrs.

1 Normal discharge 72 1

0 72 144 T

'd 2

Full core 157 2

0 52 144 discharge a

s Rev. 1 (4/9/84)

TABLE 5.1.2 MAXIMUM POOL BULK TEMPERATURE t,

COINCIDENT TOTAL POWER Q1 and COINCIDENT SPECIFIC POWER FOR THE ilOTTEST ASSEMBLY Ccse No. of Time Maximum Coincident Coincident Q1x10-6 Notes No.

Assemblies to transfer pool bulk time (since specific BTU / hour fuel into temp.*F initiation power q, pool, hrs.

of fuel BTU /sec.

transfer, hrs.

l 72 72 140 83 45.055 16.383 Normal condition 2

157

-52 139 58 47.111 31.332 Full core offload 4

c.

Rev. 1 (4/9/84)

TABLE 5.1.3 TIME (Hrs) TO BOILING AND BOILING VAPORIZATION RATE FROM THE INSTANT ALL COOLING IS LOST Case No.

CdNDITI6N 1 CON 6ITIdN 2

~

Loss of Cooling at maximum Loss of Cooling at maximum pool bulk temperature power discharge rate Time (Hrs)

Vap. Rate Time (Hrs)

Vap. Rate Ib./hr.

Ib./hr.

1 10 16885 10 16691 T

2 5

32291 5

32033 t-t 0

p 6

Rsv. 1 (4/9/84) 1 (ii) All cooling paths lost at the instant the heat dissipation power reaches its maximum value in the pool.

Results are summarized in Table 5.1.3.

Table 5.1.3 gives the bulk boiling vaporization rate for both cases at the instant the boiling commences.

This rate will decrease with time due to reduced heat generation in the fuel.

The make-up water supply to the spent fuel pool is available from three discrete sources; namely the Demineralized Water Starage Tank (DWST) in the normal mode and the Refueling Water Supply Tank (RWST) or the Reactor Make-up Water Storage Tank (RMST) in the event of an emergency.

The DWST pump is rated at 120 gpm and the RWST and RMST pumps are rated at 150 gpm (ref. Section 9.1.3.3 of the FSAR).

These make-up rates are substantially in excess of the evaporation rates reported in the foregoing.

5.2 Thermal-Hydraulics Analyses for Spent Fuel Cooling This report section covers requirement III.l.5(3) of the NRC "OT Position for Review and Acceptance of ' Spent Fuel Storage and Handling Applications" issued on April 14, 1978.

Conservative methods have been used to calculate the maximum fuel cladding temperature as required therein.

Also, it has been determined that nucleate boiling or voiding-of coolant on the surface of the fuel rods does not occur.

5.2.1 Basic

In order - to. determine an upper bound on the maximum

-fuel cladding temperature, a series of conservative assumptions are made.

The most important assumptions are listed below:-

t 5-10 I

l

,3 Rev. 1 (4/9/84) a.

As stated above, the fuel pool will contain spent fuel with varying

" time-after-shutdown" (ts)-

Since the heat emission falls off rapidly with increasing t

it is obviously conservative to s,

assume that all fuel assemblies are fresh (ts

=

144 hours0.00167 days <br />0.04 hours <br />2.380952e-4 weeks <br />5.4792e-5 months <br />) and they all have had 4.5 years of operating time in the reactor.

The heat emission rate of each fuel assembly is assumed to be equal.2 b.

As shown in Figures 2.1 in Section 2, the modules occupy an irregular floor space in the pool.

For purposes of the hydrothermal analysis, a circle circumscribing the actual rack floor space is drawn.

It is further assumed that the cylinder with this circle as its base is packed with fuel assemblies at the nominal pitch of 10.405 inches (see Figure 5.2.1).

c.

The downcomer space around the rack module group varies, as shown in Figure 5.2.1.

The nominal downcomer gap available in the pool is assumed to be the total gap available around the idealized cylindrical rack; thus, the maximum resistance to downward flow is incorporated into the analysis, d.

No downcomer flow is assumed to exist between the rack modules.

5.2.2 Model Description In this manner, a conservative idealized model for the rack assemblage is devised.

The water flow is axisymmetric about the vertical axis of the circular rack assemblage, and thus, the I

5-11

=

= -. - _, -

. - -. - ~.

Rev. 1 (4/9/84) i flow is two-dimensional (axisymmetric three-dimensional).

Fig.

1 5.2.2 shows a typical " flow chimney" rendering of the thermal l

hydraulics model. The governing equation to characterize the flow field in the pool can now be written.

The resulting integral equation can be solved for the lower plenum velocity field (in the radial direction) and axial velocity (in-cell velocity i

field), by using the method of collocation.

It should be added that the hydrodynamic loss coefficients which enter into the formulation of the integral equation are also taken from well-recognized sources 4 and wherever discrepancies in reported

{

values exist, the conservative values are consistently used.

j Reference [5] gives the details of mathematical analysis used in i

2 this solution process.

After the axial velocity field is evaluated, it is a straight-forward matter to compute the fuel assembly cladding temperature.

The knowledge of the overall flow field enables pinpointing the storage location with the minimum axial flow

]

-(i.e. maximum water outlet temperature).

This is called the most 1

" choked" location.

It is recognized that some storage locations, f

where rack module supports are located, have some additional hydraulic resis'

' encountered in other cells.

In order to y

find an upper the temperature in. such a cell, it is j

{

assumed that 2

ated at the most

" choked" location.

j Knowing the gl velocity field, the revised axial flow j

through this can be calculated by solving the Bernoulli's eqt.

an i.

the flow circuit through this cell.

l 1

l Thus, an absolut. upper oound on the water exit temperature and maximum fuel cladding temperature is obtained.

It' is believed that in view of the aforementioned assumptions, the temperatures calculated in this manner overestimate the temperature rise that will actually occur in the pool.

1 The maximum pool bulk temperature t is. computed in Section 5.1.3 5 12 m

R:v. 1 (4/9/84) and reported in Table 5.1. 2.,

The corresponding average power output from the hottest fuel assembly, q is also reported in that table.

The maximum radial peaking factor is 1.55 for the V.C.

Summer installation.

Thus, it is conservative to assume that the maximum specific power of a fuel assembly is given by 9A = q ar where ar = 1.55 The maximum temperature rise of pool water in the most disadvantageously placed fuel assembly is given in Table 5.2.1 for all loading cases.

Having determined the maximum " local" water temperature in the pool, it is now possible to determine the maximum fuel cladding temperature.

It is conservatively assumed that the total peaking factor aT is 2.32.

Thus, a fuel rod can produce 2.32 times the average heat emission rate over a j

small length.

The axial heat dissipation in a rod is known to reach a maximum in the central region, and taper off at its two extremities.

For the sake of added conservatism it is assumed that the peak heat emission occurs at the top where the local water temperature also reaches its maximum.

Furthermore, no credit is taken for axial conduction of heat along the rod.

The highly conservative model thus cons,tructed leads to simple algebraic equations which directly give the maximum local cladding temperature, tc.

5.2.3 Results__

Table 5.2.1 gives the maximum local cladding temperature, t at the instant the pool bulk temperature ha's c,

attained its maximum value.

It is quite possible, however, that the peak cladding temperature occurs at the instant of maximum value of qg, i.e.,

at the instant when the fuel assembly is i

first placed in a storage location.

Table 5.2.2 gives the 5-13

/

R3v. 1 (4/9/84) maximum local cladding temperature at t = 0.

It is to be noted that there are wide margins to local boiling in all cases.

The local boiling temperature near the top of the fuel cladding is 240*F.

Furthermore, the cladding temperature must be somewhat higher than the boiling temperature to initiate and sustain nucleate boiling.

The above considerations indicate that a comfortable margin against the initiation of localized boiling exists in all cases.

• w._

W*

JdP y

s.

/

/g'

• s V

5-14

~

s

?

4 s

. f m

l l

~

P Rev. 1 (4/9/84)

TABLE 5.2.1 MAXIMUM LOCAL POOL WATER TEMPERATURE AND LOCAL FUEL CLADDING TEMPERATURE AT INSTANCE OF MAXIMUM POOL BULK TEMPERATURE Case No.

Max. Incal Pool Maximum Coincident Local Case Water Temperature *F Cladding Temperature *F Identified l

1 170 196 72 Assemblies Cooling Mode B 2

170 197 157 Assemblies Cooling Mode A m

.L

• Cooling Mode A means 2 spent fuel pool coolers (SFPHX).

+

l Cooling Mode B means only 1 SFPHX in operation.

e e

s s.

Rev. 1 (4/9/84)

TABLE 5.2.2 POOL AND MAXIMUM CLADDING TEMPERATURE AT THE INSTANCE FUEL' ASSEMBLY TRANSFER BEGINS Case No.

Cladding Coincident Pool

__ Temp,

'F Temp.

'F

_ Bulk Local I

1 180 115 149 2

175 110 144 t

i

\\

\\

i 5-16

[

N g

REFERENCES TO SECTION_5_

^'

l f

Standard NUREG 0800 U.S. Nuclear Regulatory Commission, b

1.

Review Plan, Branch Technical Position, ASB 9-2, Rev. 2, s

-,, July 1981.

2, FSAR, V.C. Summer Nuclear Station.

Journal of Heat Transfer, Transactions of the ASME 3.

August,1981, Vol. 103, "Some Fundmental Relationships for K.P. Singh.

Tubular Heat Exchanger Thermal Performance,"

" Heat Transfer General Electric Corporation, R&D Data Books, 4.

and Fluid Flow, " 1974 and updates.

4th National Congress of the ASME, "A Method for Computing 5.

the Maximum Water Temperature in a Fuel Pool Containing(June Spent Nuclear Fuel",. paper 83-NE-7, Portland, Oregon 1983).

1

. ~

)

'n.

,.,V e

m k

i l.

A' s,-

5-17

+

w h

4 5

4

\\

w.

Rev. 1 (4/9/84)

PEAK VALUE = 140 F AT 83 HRS.

oo e

o mm.

w CASE 1 E",

w CD m.

Number of Assemblies

= 72 LLI 72 hrs, c3 Time of Discharge

=

w 1

Spent Fuel Pool Heat Exchangers

=

a R.H.R. Heat Exchanger 0

=

3 ni.

E*

4 CE LLlo CLo E'm wn.

F-

• oo ch M

i oo e

w 1.00 ab.co 4b.co sb.co sb.oo abo.co 60.00 TIME (HOURS)

FIG. 5.1.I(a)

POOL BULK TEMPERATURE; NORMAL DISCHARGE 5-18

Rev. 1 (4/9/84)

PEAK VALUE = 140 F AT 83 HRS.

i o*

Om.

w oo Inm.

-8

u..

w C.D m.

CASE 1 w

Q w

o Number of Assemblies 72

=

tilo*

Ep Time of Discharge 72 hrs.

=

D N.

ge Spent Fuel Pool Heat Exchangers 1

=

h R.H.R. Heat Exchanger 0

=

LLlo (Lo K'm wN.

H*

oo m.

w9 oo ifh 1.00 4'.00 8'.00 l'2.00 l'6.00 2'0.00 2'4.00 TIME (DAYS)

FIG. 5.1.l(b) POOL BULK TEMPERATURE; NORMAL DISCHARGE

\\

l 5-19

Rev. 1 (4/9/84) l 6

PEAK VALUE = 16.605 x 10 BTU /HR.

o AT 72 HRS.

S.

t e

oo k.

Ow

• o CASE 1 no C*o Inn.

N" Number of Assemblies 72

=

".)

H Time of Discharge 72 hrs.

=

El S.F.P. Heat Exchangers 1

=

ag'"

R.H.R. Heat Exchangers 0

=

Ww OK 4

Z o Oo (J)

MS" O

W WR$

o.

Q.g-o o.

%.00 2'0.00 4'0.00 6'0.00 8'0.00 1'00.00 l'20.00 TIME (HOURS)

FIG. 5.1.1 (c) POWER DISCHARGE; NORMAL DISCHARGE 5-20 e---,-

e w

e-s-

e

,e-we--e r

-,-e

--n,e-e-m-n e-m

-w-~

~-,w

~--

-v--~e-

l.

Rev. 1 (4/9/84) 6 PEAK VALUE = 16,605 x 10 BTU /HR. AT 72 HRS.

9 8.

=

8 e

• O

• oo n

i E*18.

N 1

Na CASE 1 3

P--

1 El Number of Assemblies 72 o

=

o Time of Discharge 72 hrs.

=

CO O

W."

5.F.P. Heat Exchangers 1

=

R.H.R. Heat Exchangers 0

=

<Zo C3o U3

• H$-

O EW38 i

C.

k

=

8

~

o

'0.00 4'.00 8'.00 th.00 th.00 2'0.00 2'4.00 1.

TIME (DAYS)

FIG. 5.1.1 (d) POWER DISCHARGE; NORMAL DISCHARGE i

I 5-21

f Rev. 1 (4/9/84) o PEAK VALUE = 139 F at 58 HRS.

o v2 M.

w

-8 LLo CDM.

w Q

w o

wo gf Number of Assemblies 157

=

D' Time of Discharge 52 brs.

=

Spent Fuel Pooli Heat Exchangers 2

=

g R.H.R. Heat Exchanger 0

=

xd ww.

H*

o o

o, h

1.00 ab.co 4b.co sb.co eb.co ibo.co tho.co TIME (HOURS)

FIG. 5.1.2 (a) POOL BULK TEMPERATURE; FULL CORE DISCHARGE 5-22

• ,..y Rev. 1 (4/9/84) l l

i o

o.

o*-

PEAK VALUE = 139 F AT 58 HRS.

l oo mm.

^$

u..

i o

CD m.

w Q

oO LLI,

Em CASE 2 3 cu.

F*

4:

g Number of Assemblies 157

=

Time of Discharge 52 hrs.

=

Z*o SFP Heat Exchanger 2

=

LLicu.

j F- "

R.H.R. Heat Exchanger 0

=

o o.

W o

o.o w

1.00 4'.00 8'.00 l'2.00 1'6.00 2'0.00 2'4.00 TIME (DAYS)

FIG. 5.1.2 (b) POOL BULK TEMPERATURE; FULL CORE DISCHARGE l

i 5-23

-,o.

m

..=_.,,-.,.3_,.

y -

• m** '.'

j l

Rev. 1 (4/3/84) i o

o m-6 m

PEAK VALUE = 31.647 x 10 BTd/HR.

AT 52 HRS.

o E'

-o

.4*oo C*o Im_

Nm

~3 F-8o O.

i OO WS-Number of Assemblies 157

=

C.D g

Time of Discharge 52 hrs.

47g S.F.P. Heat Exchangers 2

=

R.H.R. Heat Exchangers 0

=

sS-Q GWo 3 *.

Oo Q.0,-

o o,

.00 2'0.00

/0.00 6'0.00 8'0.00 1'00.00 l'20.00 TIME (HOURS)

FIG. 5.I.2 (c) POWER DISCHARGE; FULL CORE DISCHARGE i

5-24 L.-

Rev. 1 (4/9/84) 9 l

4 oo oc.

m 6

PEAK VALUE = 31.647 X 10 BTU /HR. AT 52 HRS.

o

.oo.

e m Ow*oo E*

i o

Im.

Nm

~3 P--bo*

OS.

wm CD G

4 Number of Assemblies 157

=

7u 52 hrs.

gjo Time of Discharge

=

m m *.

S.F.P. Heat Exchangers 2

=

o i

R.H.R. Heat Exchangers 0

=

g i

W *O l

3.

oo l

m o

0, l

00 4'.00 8'.00 i2.00 i6.00 2'0.00 2'4.00 TIME (DAYS)

FIG. 5.1.2 (d)

POWER DISCHARGE; FULL CORE DISCHARGE I

5-25 y

w--

r

---.y

+. -

p y

y--a w

. ~--

.-.,,-.p-w

,-m-

--w++

.3 Actual

~

i d e a liz e d O u tlin e Outline of O f Ra c k. A's s e m b l y Rack Assembly M

T 2

i RACK ASSEMBLY

/

/

kmf-Actual Outline idealized Outline Assumed Added Fuel Assemblies FIG. 5.2.1 IDEALIZATION OF RACK ASSEMIllLY

',...e Water Assumed At The Pool Bulk Temperature

,r-+-

J L n

I l

/~]

/

_/

TouTA"

/

/

C'7 o\\O INT

@1 3o 2

C b'

N f

J

+-Q Heat Addition v

3' aZ U

/

C7

/

6i o

, w=

(OO/

/

~.

_/_,

/

(

l FIG. 5.2.2 THERMAL CHIMNEY FLOW MODEL 5-27

-~

.-