ML19317F158

Irradiation of Two 17x17 Demonstration Assemblies in Oconee Cycle 2.Reload Rept

ML19317F158
Person / Time
Site:	Oconee
Issue date:	01/31/1976
From:	BABCOCK & WILCOX CO.
To:
References
BAW-1424, NUDOCS 8001080879
Download: ML19317F158 (16)

Text

g BAW-1424 January 1976 og R Elili $ l a.s b u E 'l, d...,,,,,

I

-m 1

R003 BtB 1

1 IRRADIATION OF TWO 17x17 DEMONSTRATION ASSMSI.IES IN OCONEE 2. CYCLE 2 l

l

- n.1o.4 a. gore -

I I

I I

I i

I y

I

~

l

~

3ETl!M 70 flEG!llAT03Y CE&d. "US I

i:003GLS-

~

I Babcock &Wilcox h,

. ~. -

..... J 8001080 [ [

M

y-T BAW-1424 January 1976 I

s.

i*

L

• IRRADIATION OF TWO 17x17 DDt0!ISTRATION ASSDtBI.IES IN OCONEE 2. CYCLE 2 j

- Reload Report -

a by P. C. Childress

{i 14 J. J. Woods T. N. Ake

~

I l

l BABCOCK & WILC01 i

Power Generation Group Nuclear Power Generatir:n Division P. O. Box 1260 Lynchburg, Virginia 24505 Babcock &Wilcox U

4 4

m.

L CotrrENTS Page 1

1 1.

INTRODUCTICN...........................

2 2.

MECHANICAL DESIGN 7

3.

NUCLEAR DESIGN..........................

10 4

THERMAL-)IYDRAtJLIC DESIGN.

1 12 5.

EVALUATION OF DIFFERENCES 13 DISTRIBUTION.

J List of Figures Figure 5

1.

Fuel Assembly Comparison 6

2.

End Fitting Designs..

8 3.

Fuel loading Pattern for Oconee 2, Cycle 2 4.

deletive Power Densities for Oconee 2 - Beginning of Cycle 9

2. Transient Rods In i

i

\\

'J i

i.

E

'I s

i I

s a

hM & MOX E

. gg _

t l

l t

T f,

t.

L 1.

INTRODUCTION lL.

Duke Power Company will irradiate two 17x17 fuel rod assemblies in the Oconee Unit 2 reactor during fuel cycles 2, 3, and 4.

This irradiation will be a demonstration of the in-reactor performance of the 17x17 Mark-C fuel assembly.

This report identifies the differences to be espected between a core operating with 17715x15 fuel assemblies and one operating with 175 15=15 fuel assemblies a

and two demonstration 17x17 assemblies. An evaluation of these differences ll Indicates that reactor safety and performance are not adversely af fected by I

the presence of the two demonstration assemblies.

1',

i e

O m.

1 i

Iic l

t t

l wb t Babcock &Wilcox

{

[

L

T l

w 2.

MECHANICAL DgSIGN s.

The two 17x17 demonstration assemblies to be irradiated in Oconee 2 are struc-t turally identical, to the extent possible, to the generic Mark-C design. h

' end fittings and spacer grid elevations were modified to be compatible with j

the 15x15 fuel assembly (Mark-B) interface constraints.

I L' :

The Mark-C demonstration assembly is a 17x17 array of fuel rods with the a w external envelope as the Mark-B.

Table 1 is a dimensional comparison of ts.

};

Mark-B and Mark-C de=anatratian assemblies. The h rk-C d==anstration assen-L blies are mechanically compatissle and interchangeable with Mark-B assemblies with the exception of the control component interface.

~

& demonstration assemblies have Mark-B upper end fitting plenues to ensure compatibility with core internals and Oconee handling equipment (see Figures L;

i 1 and 2).

The design of the demonstration assembly, upper end fitting necessi-

)

l tated the use of a single helical holddown spring instead of the four used in i

the standard Mark-C design. The demonstration assembly holddown spring is sized to generate a compressive force greater than that of the single Mark-B

]

spring and similar to that of the four Mark-C springs.

h spacer grid elevations in the demonstration assemblies are identical to those of the Mark-B assemblies. This is required to provide lateral interface support from grid to grid or grid to baffle. The standard Mark-C fuel assen-blies will have slightly different spacer grid elevations than the demonstra-j tion assemblies to make assembly insertion and withdrawal easier.

l Standard Mark-C fuel rods are used in the two demonstration assemblies. The i

$~

pellets and cladding have been eummined extensively and their properties cataloged for subsequent reference. Two lengths of fuel pellets have been j

J manufactured for the demonstration assemblies. All other pellet parameters f-are identical. Utilization of diff rent fe.1 pellet length-to-diamecer ratios i

.I allows different fabrication and Icading techut.cses to be investigated. The

)

i larger pellet L/D ratio in similar to the: L/D successfully used in the Mark-B i

[ <-

4 l

. hheaek s,Wilcox t

i

• l

T fuel assembly. The smaller L/D is espected to improve the performance of the 17 = 17 demonstration furt assembly.

The demonstration assemblies are compatible with the Oconee incore detectors.

Thete is a minimme diametral clearance of 0.096 inch between the instrument tube and instrument probe. This clearance is more than adequate to allow free movement of the instrument probe in the insert - t tube.

c The Mark-B control tod assemblies at Oconee are not coespatible with the Mark-C L.

demonstration fuel assemblies. This dictates that the demonstration assemblies be located in non-control rod positions. Design limitations also preclude the There-use of a Mark-C orifice plug asscably in the demonstration fuel assembly.

fore, the nuts that attach the demonstration assembly guide tubes to the upper t

end fitting have bcen or t.ced to provide the same 1ypass flow as a standard C

Mark-C guide tube with orifice plugs inserted.

The two assemblies have been extensively precharacterized and will be examined

)J' after every cycle. Observation windows have been cut into the end spacer grids to allow measurement of fuel rod growth without removing the rods from the fuel k

assembly.

The static and dynamic structural characteristics of the demonstrati

- assen-blies are compatible with the Mark-B assemblies. The demonstration assemblies p

i have been designed to maintain their mechanical integrity through three cycles f

of operation and successfully withstand all seismic and IACA loads postulated

{

for the Oconee 2 reactor.

t 6

h

'.,3 1

4 d

t e

J i

l<t

.i

-i n J [

_3_

i l

g Table 1.

Oconee 2. Cycle 2 Fuel Assembly Comparison Mark-C Mark-B demo assembly assembly Total No. of assemblies 175 2

No. of fuel rods / assembly 208 264 i t 16 24 b

No. of guide tubes No. of instrument tubes 1

1 Fuel rod OD, in.

0.430 0.379

,l Cladding-pellet dias. gap, in.

0.007 0.008 1

I Fuel rod cladding thickness, in.

0.0265 0.0235 Fuel pellet diameter, in.

0.370 0.324 0.600(b), 0.375(b)

Fuel pellet length, in.

0.700 i

I Fuel pellet density, Z TD 92.5, 93.5

• 94.0 0.568 0.502 iI Fuel rod pitch, in.

1 Fuel assembly pitch, in.

8.587 8.587 1

I 144.0, 142.5 ")

143.0 i

Nominal active fuel length, in.

i Bot flow area, in.2 40.39 40.35 Avg linear heat rate, kW/ft 5.81 4.61 2

281.5 312.7 Heat transfer area / bundle (hot), f t

• Batch 4, Oconee 2.

(b)one assembly with 0.375-tr.ch pellets only. One assembly has 11 'uel rods with 0.375-inch pellets while the remaining rods have 0.600-inch pellets.

, i

, 6 ffi

(

Babcock aWilcox

}[

4

T Fleure 1.

Tuct Assenbly Cowarison f

My:

s I

_ 11 II \\

II YY Y

I

'II I

.s 21 r,_j.

~

r~-

g i.

+

1 I

0g %N'I d0,f 0! 'l I<

g

='

7 I

%(y hf }.Rbf.f e -,

2n!- _.eacet; e mee a(a'l-1

.N-i f

tie 7

j T

i p_

f3 x1 ee_

'l

~

I A

.e D _

2

f t.;

L

%d I

L I

I I

1 I

1 f

5

~

j 15 d,-5-b,-i5,-5-b,,-$-I J

H-H-M i+H H-i M 3 (

?.

.1 i

i t

1 sl l

l MARK-B3 FUEL MARK-C DEMONSTRATION ASSEMBLY FUEL A5SEMBLY

[

Babcock &Wilcos 3_

J

_J o

T l

Figure 2.

End Fitting Designs b,

l

~

)

Q

}')

C:

6 N

/.

s y

t

- _a

[

ev s

I 08 9

s-J.

EP

'yai-q g

e.. m m

3)r[

s F#Manst-r#MsWIa3 j

]Gu(.

Is d

0 I

9 i;

. L

,Fj l

L W I N M I ! E w1.1 f k'.1 ! E 1 4 i T s4 l i

e i

l MARK C DEPO UPPER END FITTING MARK-B UPPER END FITTING

)..

N I

f DDD%W l{MMDTl

??

$f"?)1 f_!

f 7y pt=N -

i il l,

d1 iril %

n c w

.II<

c-h b

FEE 0

[

(m i-i i

!(

MARK-C DEMO LOWER END FITTING MARK-B LOWER END FITTlHG I

c e

lo I

Babcock & Wilcox

,[.. - -

\\

i

t.,

i u

lt L

3.

NUCLEAR DESIGN

'J

< I The 17x17 demon-

'j The Oconee 2, Cycle 2 loading pattern is shown in Figure 3.

stration assemblies will be loaded 'n symmetric core locations A-6 and R-10.

NU, as the other batch 4 fuel They will have the same enrichment,

.64 wt Z Figure 4 shows the core,Swer distribution at the beginning of

~

assemblies, Cycle 2 calculated for a core loaded entirely with 15x15 assemblies, i

The nuclear characteristics of the 17x17 and 15x15 assemblies are nearly iden-u Initially, the average relative power densities in the 17=17 assemblies i

l f

tical.

The reac-will be slightly less than those in the symmetric 15-:15 assemblies.

~

tivity of a 17x17 assembly is approximately 0.2% lese than that of a 15x15 l5'l this is a result of differences in fuel load-assembly of the same enrichment; The 17x17 and 15x15 assemblies contain 456.1 and 463.6 kg of urarium, Ing.

respectively. The slightly lower relative power density in the 17x17 assemblies results in a slightly lower burnup, which tends to reduce the reactivity dif-l 'l

~

t ferential and increase the relative power density. The relative power density j

in the 17x17 assemblies approaches that of the symmetric 15x15 assemblies as

~

u the cycle progresses.

,i The peak pin-to-average assembly power in a 17x17 fuel assembly is approxi-mately 1.0 to 1.3% lower than that in a 15x15 assembly of the same enrichment i!

j in a similar core location. T1.e reduction is primarily due to the larger

[

n' umber of water holes (control rod guide tubes and instrument channel), which f 'J i

1

{ '

are arranged more uniformly over the assembly.

f There are no significant differences between the Doppler and moderator teripera-There-g

ture coefficients for 17x17 and 15x15 assemblies of the same enrichment.

f fore, the presence of the 17x17 fuel assemblies will not discernably affect overall core reactivity coefficients or performance.

n 1 r

i e fP ha fM s.bcock s.wiscox -

... _ _.g w,

1 Figure 3.

Fuel Icading Pattern for Oconee 2. Cycle 2 k

9.

i

\\

s 8

l

-. - n.

-.- q l!

b

,V I

\\

• 9 i

s A.

A.

.i J

\\

10 4

i@s.iij'ffy..

I

/

2ic.;: ijiifR8i tiiisii:8Ejiij$.,iji:

' 3ss:p,:..

i L

.::$$p4.::53:;j

//

i@?355?:i8@it s$iii5?4i :!!*'

.,.>:2 w j

\\

I

(.'

\\

11

$!$!$.5$j$

[

Ring!;f:s ii:g!!

h.

M

/

?ii:S s.. p Batch 3, 3.05 wt I

//

SM:is::

N I

12

. s,

, p i

.;..,g.wJ:i^ji:

/

/

w~..%..,

g i

..:.3>;g;fgiilirc-

"'R!R :i!!;giq*g::

a sp2::54i.9.ss:!

.s.:

5. 5..!,I. ggi:9w'..$iS -

sg:. si?

Batch 2 e

N 5gg8i

2.75 vt I g: :r : g8s f,

s agi9

/,

s issi giy. :*$

y g

t g

N 13 i

h.!!hb til$!k:isi8i 5 !!!!($

55!h! !h!i$

iljij:.

.... !!MiMjjN!!j $ sis

'iss!!!

j:iigir;::~

/

h;;j:gj!s

.ffjf!!!!['

i

.ifi ii![ifE !N

$!$i!!!fj.ff.f.3 A

7 t i)

I;$!!.w. Sij5.!h

w<

eg:-

Batch 4

>l p

..:sy.g w:

.!!$ijf S50!$si

/

2.64 we Z

~

..J.a. l53}i:. 5..;E..

f/,

.: 8]

I

)

I R

4 17x17 Demonstration Assembly

)

t 1-g I i i.

i o.

Babcock &Wilcox h

a-

T_

9

[

Figure 4.

Relative Power Dens.ities for Oconee 2 -

Beginnf ag of Cycle 2 Transient kods In k

g s

8 l

L"

.- H-1.34

-* ~ (

7

-g l2 i

L E

1.22 1.37 l'

s s

10 d

s 4

L 1.19 1.33 1.16 i

a g

i sN 11 j,-

u M

1.15 1.21 1.12 1.35 1?

I I

N

'N 17 N

1.20 1.25 1.12 1.30 3.11

!1 I

f 13

• s i;

t 0

0.82 0.56 0.%

1.21 1.12 0.75 IJ l

j w(

N I

c i.

5 P

0.75 0.68 0.98 0.96 0.68 e

l l

i I

( ii i

R 0.59 0.59 0.53 1

p I

l-I..

g I <d 98bCOCk & WilCOX

'L [..

l LL I

i

f 4

I s_.

fL I

4.

TlERNAL-BYDRAUI.1C DF. SIGN l.

b.

Analytical results show good thermal-hydraulic compatibility between the demon-stration assemblies and the remainder of the core. The similarity in flow areas and hydraulic resistance of the 15x15 and 17x17 assemblies will allow s.

both to operate safely in the same environment.

n e pressure drop loss coefficients for the demonstration asscablies were exper-inentally determined in a heated-water test facility that simulated reactor

('

conditions. The test results s.. owed that the overall hydraulic resistance of the test assemblies is greater than that of a Mark-B assembly. Because of l

this difference in resistance, the Mark-B assemblies vill receive slightly more flow than they would in an all-Mark-B core, whereas the Mark-C test assemblies will recieve slightly less flow than would Mark-B assemblies in the same core L

locations. The effect of this extra resistance on the total core pressure drop is negligible.

A lift analysis was performed to demorstrate that the Mark-C test assemblies will not lift during any expected reactm conditions. n e results for the Mark-0 demonstration fuel assembly shoud a substantial margin in holddown force even at reactor system flow rate: 20% greatcr than expected. This anal-ysis used several conservative assumptions concerning fuel assembly resistance,

}

flow, and h31ddown spring tension. The 17x17 assemblies will have a negligible f

effect on the lift margin of the Mark-B assemblies.

The thermal performance of the Mark-B fuel assemblies in the presence of the two demonstration assemblies will be equivalent to or better than their per-formance in a core composed entirely of Mark-B fuel assemblies because of the slightly increased Mark-B fuel assembly flow. Thus, the Mark-B fuel assembly minimum DNBR will be somewhat improved over the reference value reported in j

the FSAR. In addition, a DNBR analyeis was performed for the Mark-C demon-

)

i stration assembly using the BAW-2 correlation with conservatisms and w

I

?

Babcock &Wilcox,

i

uncertainties associated with the reference "asximum design case" as noted in the FSAR.I These results showed that the minissna DNBR, 3.25, was well above the 1.55 design minimum.

Analyses have been performed to determine tbs==Maum linear heat rate that will cause centerline fuel melt in 17x17 and 15x15 assemblies. These results show that centerline melt would occur at approximately the same linear heat rate for f

both assembly types, assuming densification and using NRC-imposed restrictions on the TAFY-3 computer code.2 The average linear heat rate for the 17x17 fuel assembly is reduced approximately 25% due to the extra fuel length; therefore, 17x17 demonstration fuel assemblies will operate at a lower temperature than l

the 15x15 assemblies, and the demonstration fuel assemblies will not be limit-

~

ing with regard to the centerline fuel melting criterion.

1 l

1 f

1 i

b i

1 1

IFinal Safety Analysis Report, Duke Power Company, Oconee Nuclear Station,

,j Docket No. 50-270.

2TAFY - Fuel Pin Temperature and Gas Pressure Analysis, Brd-10044, Babcock &

Wilcox, April 1972.

g 1

[

11 -

Babcock s.Wilcox m____.

7

_y_v

..-,,v-

T i

5'.

EVALUATION OF DIFFERENCES l

The two'17x17 fuel assemblies have a substantial additional operating margin

.J beyond that of the 15=15 fuel assemblies with respect to fuel temperature lin-

.l itations. Together with the lower average linear heat rate, the placement of the demonstration assemblies in the core further guarantees that the 17x17 lg d

assembly will not restrict the operation of the core.

As described in section 3, the core power distribution remains very nearly un-l Minor local E

affected by the presence of the two demonstration assemblies.

reactivity perturbations do occur, but their effect is negligible because there are only two 17x17 assemblies out of a total of 177 t'uel assemblies in the L:

core.

'l The total fission product inventory of each 17x17 assembly is expected to be J

nearly identical to that of a 15x15 assembly in the same core location; how-3 ever, because the 17x17 assembly operates at a significantly lower average j

linear heat rate, the fraction of the activity available to the fuel pin gap and plenum is conservatively lower than that expected with the 15x15 fuel design.

Therefore, the loading of two 17x17 Mark-C demonstration assemblies in Oconae

}

2, cycle 2 will not discernably affect the nuclear, mechanical, or thermal-

{

hydraulic character of the reactor, nor will it adversely affect the existing safety analysis.

3 J

fa J

lm Babcock &Wilcox

=

T f;

-......,s-.

2...-

Distribution I

Duke Power Company (75)

{

Babcock & Wilcox Ij Ake, TN Andrews, JB f

Brunson, WT

.1 Childress, DC l

Croft, Mi DeMars, RV Dideon, CG

}

.2 Duerson, SH Bellman, SP y

Keyworth, WJ Klink, PH

.-i Library (2)

J Robertson, JD o..

Spaziani, JC Stultz, WL Suhrke, KE Travis, CC/TRG Tulenko, JS ij W111se, JT Woods, JJ

~

l J

o O

L c-f g

.....,_ /

Babcock &Wilcox c

._ 13 _ -

m-p

~

-,"^

d

. - - ~