Text

Rev 0 to North Anna Unit 2 Cycle 6 Core Performance Rept
	ML20245L093
Person / Time
Site:	North Anna
Issue date:	04/30/1989
From:	Dziadosz D, Pierce N, Trace D; VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	;
Shared Package
ML20245L092	List: ML20245L086; ML20245L093;
References
	NE-692, NE-692-R, NE-692-R00, NUDOCS 8908210267
	Download: ML20245L093 (50)
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Unit 2 Cycle 6 Core Per ormance Report

-Nuclear Analysis and Fuel Power Engineering Services

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7 TECHNICAL REPORT NE-692 - Rev. 0 I

NORTH ANNA UNIT 2, CYCLE 6

+

CORE PERFORMANCE REPORT I

NUCLEAR ANALYSIS AND FUEL POWER ENGINEERING SERVICES VIRGINIA POWER APRIL, 1989 I

NI3Id I

PREPARED BY:

41 REVIEWED BY:

D. A. Trace Date R. H. Garve*r Date REVIEWED BY: #7N Vg,v/i!?

REVIEWED BY: II 4'

ai N. S. Pierce

'Date T. A. Brookmire D&te Y'7/f/ APPE0VED BY:

U*

@lb 4!7!Ti APPROVED BY:

D. Dziadosz &

Ifate K. L. Basehore Date QA Category: Nuclear Safety Related l

xe,..rds, N2ce. c.re Pe.,.r.a.ce I

J

I CLASSIFICATION / DISCLAIMER I

The data, information, analytical techniques, and cone *csions in this report have been prepared solely for use by the Virginia Electric and Power Company (the Company), and they may not be ap?ropriate for use in situations other than those for which they were specifically prepared.

The Company therefore makes no claim'or warranty whatsoever, express or

implied, as to their accuracy, usefulness, or applicability.

In particular, THE COMPANY MAKES NO WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, NOR SHALL ANY WARRANTY BE DEEMED TO ARISE FROM COURSE OF DEALING OR USAGE OF TRADE, v.ith respect to this report or any of the data, information, analytical techniques, or conclusions in it.

By making this report available, the Company does not authorize its use by others, and any such use is expressly forbidden except with the prwr written approval of the Company. Any such written approval shall itself be deemed to incorporate the disclaimers of liability and disclaimers of warranties provided herein. In no event shall the Company be liable, under any legal theory whatsoever (whether contract, tort, warranty, or strict or absolute liability), for any property damage, mental or physical injury or death, loss of use of property, or other damare iesulting from or arising out of the use, authorized or unauthorized, of this report or the data, information, and analytical techniques, or conclusions in it.

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TABLE OF CONTENTS PAGE 1

Classification / Disclaimer.

1 Table of Contents 2

List of Tables.

3 List of Figures.

4 Section 1 Introduction and Summary.

6 Section 2 Burnup.

12 Section 3 Reactivity Depletien.

. 20 Section 4 Power Distribution.

. 22 Section 5 Primary Coolant Activity.

. 43

. 47 Section 6 Conclusions.

Section 7 References.

48 B

I I

^

NE-692 N2C6 Core Performance Report Page 2 of 48

i LIST OF TABLES I

I TABLE TITLE PAGE I

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LIST OF FIGURES 1

I FIGURE TITLE PAGE

. I 1.1 Core Loading Map.

9 1.2 Movable Detector and Thermocouple Locations.

10 l

1.3 Control Rod Locations.

. 11 I

2.1 Core Burnup History 14 2.2 Monthly Average Load Factors.

. 15 2.3 Assemblywise Accumulated Burnup: Measured and Predicted.

. 16 2.4.Assemblywise Accumulated Burnup: Comparison of Measured and Predicted.

17

'2.5A Sub-Batch Burnup Sharing.

. 18 2.5B Sub-Batch Burnup Sharing.

. 19 3.1 Critical Boron Concentration versus Burnup - HFP-ARO.

. 21 4.1 Assembly *ise Power Distribution - N2-6-04

. 28 1

4.2 assemblywire Power Distribution - N2-6-16

. 29 4.3 Assemblywise Power Distribution - N2-6-24

. 30 4.4 Hot Channel Factor Normalized Ope u ting Envelope.

. 31 4.5 Heat Flux Hot Channel Factor, F (Z) - N2-6-04

. 32 g

4.6 Heat Flux Hot Channel Factor, F (2) - N2-6-16

. 33 q

4.7 Heat Flux Hot Channel Factor, F (Z) - N2-6-24

. 34 q

4.8 Maximum Heat Flux Hot Channel Factor, F (Z)*P, vs.

g Axial Position.

35 4.9 Maximum Heat Flux Hot Channel Factor, F (2), vs. Burnup

. 36 q

4.10 Maximum Enthalpy Rise Hot Channel Factor, F-delta-H vs.

Burnup.

...........37 I

NE-692 N2C6 Core Performance Report Page 4 of 48

I LIST OF FIGURES CONT'D FIGURE TITLE PAGE I

4.11 Target Delta Flux versus Burnup 38 4.12 Core Average Axial Power Distribution - N2-6-04 39 4.15 Core Average Axial Power Distribution - N2-6-16 40 4.14 Core Average Axial Power Distribution - N2-6-24 41 4.15 Core Average Axial Peaking Factor vs. Burnup.

. 42 5.1 Dose Equivalent I-131 vs. Time.

. 45 5.2 2 131/I-133 Activity Ratio vs. Time 46 I

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i NE-692 N2C6 Core Performance Report Page 5 of 48

i

)

I Section 1 INTRODUCTION AND

SUMMARY

I On February 20, 1969, North Anna Unit 2 completed Cycle 6.

Since the initial criticality of Cycle 6 on November 3, 1987, the reactor core 8

produced approximately 1.06 x 10 MBTU (17,844 Megawatt days per metric ton of contained uranium), which has resulted in the generation of 10 9

approximately 1.03 x 10 KWHR gross (9.8 x 10 KWHR net) of electrical energy. The purpose of this report is to present an analysis of the core performance for routine operatien during Cycle 6.

The physics tests that were performed during the startup of this cycle were covered in the North 2

Anna Unit 2, Cycle 6 Startup ehysics Test Report and, therefore, will not be included here.

I North Anna Unit 2 was in coastdown from December 12, 1988, at which time the burnup was approximately 15,616 MWD /MTU. The coastdown accounted for an additional core burnup of roughly 2,228 MWD /MTU from the end of full power reactivity.

The Cycle 6 core consisted

of eight sub-batthes of fuel:

three once-burned sub-batches, one from North Anna Unit 1 Cycle 4 and two from North Anna Unit 2 Cycle 5 (sub-batches N1/6, 7A and 7B, respectively);

two twice-burned batches from North Anna Unit 1 Cycles 3 and 4 and North Anna Unit 2 Cycles 4 and 5, (sub-batches N1/5 and 6); one thrice burned g

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I' sub-batch from North Anna Unit 2 Cycles 3, 4, and 5 (sub-batch SA); and two fresh sub-hotches (sub-batches BA and BB).

The North Anna 2, Cycle 6 core loading map specifying the fuel batch identification, fuel assembly B

locations, burnable poison locations and source assembly' locations is shown in Figure 1.1.

Movable detector locations and thermocouple locations are shown in Figure 1.2.

Control rod locations are shown in Figure 1.3.

Note that movable detector locations G7, J7 and G9 have become inoperable due to thinning in the thimble tubes.

Routine core follow involves the analysis of four principal performance indicators.

These are burnup distribution,, reactivity depletion, power distribution, and primary coolant activity.

The core burnup distribution ia followed te verify both burnup symmetry and proper batch burnup sharing, thereby ensuring that the fuel held over for the next cycle will be compatible with the new fuel that is inserted.

Reactivity depletion is monitored to dete.:t the existence of any abnormal reactivity behavior, to determine if the core is depleting as designed, and to indicate at what burnup level refueling will be required.

Core power distribution follow includes the monitoring of nuclear hot channel factors to verify that they are within the Technicel Specifications

limits, thereby ensuring that adequate margins for linear power density and critical heat flux thermal limits are maintained.

Lastly, as part of normal core follow, the primary coolant a'ctivity is monitored to verify that the dose equivalent iodine-131 concentration is within the limits r

specified by the North Anna Unit 2 Technical Specifications.

A radiciodine analysis based on the iodine-131 concentration in the coolant is performed to assess the integrity of the fuel.

NE-692 N2C6 Core Performance Report Page 7 of 48 1

c Each of the four performance indicators is discussed in detail for the North Anna Unit' 2, Cycle 6 core in the body of this report. The results are summarized below:

1. Burnup - The burnup tilt (deviation from quadrant symmetry) on the core was no greater than 10.36% with the burnup accuriulation in

. each batch deviating from design prediction by no more than 1.53%.

2. ' Reactivity Depletion The critical boron concentration, used to monitor reactivity depletion, was consistently within 10.25% AK/K of the design prediction which is within the 11% AK/K margin allowed by Section 4.1.1.1.2 of the Technical Specifications.

3.

Power Distribution ' - Incore flux maps taken each month indicated that the assemblywise radial power distributions deviated from the design predictions by a maximum average difference of 2.0%.

All hot

-channel factors met their respective Technical Specifications limits.

4.. Primary Coolant Activity The average dess equivalent iodine-131 ' activity level in the primary coolant during Cycle 6 was approximately 6.2 x 10~3 pCi/gm. This corresponds to less than 1% of the operating limit for the concentration of radiciodine in the primary-coolant. Radiciodine analysis indicate. no fuel rod defects.

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Hate,tal l

8 Aa-In-Cd C

Function Number of Clusters Control Bank D 8

Control Bank C 8

I-Control Bank B 8

Control Bank A 8

Shutdown Bank SB 8

Shutdown Bank SA 8

SP (Spare Rod Locations) 8 lI

< l-I II

{

l

e I.

I Section 2 I

BURNUP I

The burnup history for the North Anna Unit 2,

Cycle 6 core is graphically depicted in Figure 2.1.

The North Anna 2, Cycle 6 core I

achieved a burnup of 17,844 MWD /MTU. As shown in Figure 2.2, the average load factor for Cycle 6 was 94.4% when referenced to rated thermal power (2893 MW(t)). Unit 2 performed a temperature / power coastdown starting on December 12, 1988 until shut down for refueling on February 20, 1989.

I Radial (X-Y) burnup distribution maps show how the core burnup is shared among the various fuel assemblies, and thereby allow a detailed 8

burnup distribution analysis.

The NEWTOTE computer code is used to calculate these assemblywise burnups.

Figure 2.3 is a radial burnup distribution map in which the assemblywise burnup accumulation of the core at the end of Cycle 6 operation is given.

For comparison purposes, the design values are also given. Figure 2.4 is a radial burnup distribution map in which the percentage difference comparison of measured and predicted assemblywise burnup accumulation at the end of Cycle 6 operation is also given. As can be seen from this figure, the accumulated assembly burnups were generally within 13.14% of the predicted values.

In addition, deviation from quadrant symmetry in the core throughout the I

i cycle was no greater than 0.36%.

j The burnup sharing on a batch basis is monitored to verify that the I

core is operating as designed and to e.nable accurate end-of-cycle batch NE-692 N2C6 Core Performance Report Page 12 of 48 1

I.

5 burnup predictions to be made for use in reload fuel design studies.

Batch definitions are given in Figure 1.1.

As seen in Figures 2.5A and 2.5B, the. hatch burnup sharing for North Anna 2, Cycle 6 followed design predictions closely with no batch deviating from prediction by more than -

1.53%. Symmetric burnup in conjunction with agreement between actual and predicted assemblywise burnuns and batch burnup sharing indicate that the Cycle 6 core did deplete as designed.

I I

'I I

I I

g ss.e,2 x2ce core eertor.ance,eport rage 13 or e

g Figure 2.1 NORTH ANNA UNIT 2 - CYCLE 6 I

CORE BURNUP HISTORY i

18000

/

17000 16000

/

E

/

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/

r

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L E 12000 f

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NE-692 N2c6 Core performance Report Page 14 of 48

1 4

c.

l Figure 2.2

-l NORTH ANNA UNIT 2 - CYCLE 6 MONTHLY AVERAGE LOAD FACTORS-64

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Pigure 2.3 NORTH ANNA UNIT 2 - CYCLE 6 ASSEMBLYWISE ACCUMULATED BURNU, MEASURED AND,REDICTED (2000 MWD /MTU)

R P

M M

L E

J H

G F

E D

C 8

A I

I l 38.656 30.971 38.431 1 MtesuRED 1 1

1 38.301 29.671 38.30) i PREDICito i 2

1 38.118 32.181 18.741 34.111 18.971 33.021 38.381 2

1 18.111 32.458 19.001 34.Mi 19.601 32.451 38.111 E

........=_

3 1 41.471 18.851 21.511 38.861 22.631 39.031 22.381 19.291 41.55l 3

1 40.991 18.858 22.121 39.141 23.141 39.141 22.121 18.851 40.991 4

1 41.23 8 36.191 22.831 41.Mi 2:J.811 42.711 23.76 8 42.191 22.69 8 %.681 41.68) 4

.......i 40.998 % 881 22.678 41.631 24.101 42.881 24.108 41.631 22.678 36.081 48.991 I

5 l 38.621 18.691 22.168 42.401 23.321 42.411 38.361 42.371 23.968 42.831 22.30! 18.711 38.171 5

l 38.251 18.871 22.691 42.791 23.841 42.15l 38.098 42.151 23.841 42.791 22.694 18.871 38.251

=.

6 1 32.944 22.081 41.561 23.351 43.598 24.111 42.701 24.171 43.821 23.451 41.096 21.721 32.821 6

5 1 32.431 22.131 41.69) 23.851 43.451 24.081 42.601 24.081 43.451 23.85) 41.691 22.131 32.431 7

l 38.29 8 18.971 38.43 l 23.47 6 42.101 23.531 43.601 23.601 43.781 24.161 41.601 23.07 8 38.69 4 18.401 38.681 7

1 38.174 19.001 39.131 24.108 42.161 24.884 43.411 13.481 43.418 24.081 42.161 24.101 39.131 19.00'.38.171 8

1 29.764 32.151 22.551 42.751 38.111 42.658 23.371 38.04l 23.181 42.681 37.851 41.848 22.451 34.231 29.778 8

I l 29.401 33.161 23.151 42.831 38.261 42.761 23.461 37.74 8 23.46 6 42.7(1 34.26 8 42.831 23.151 33.161 29.40 6

=,-

9 1 38.351 18.621 38.481 23.431 42.081 23.638 42.831 22.861 43.091 23.66) 42.04l 23.691 39.221 19.151 38.401 9

1 38.171 19.001 39.131 24.101 42.161 24.881 43.411 23.484 43.418 24.081 42.161 24.101 39.138 19.001 38.178

.......................... = --

10 1 31.901 21.251 41.231 23.871 43.281 23.581 42.351 23.521 62.871 23.631 42.281 22.574 32.641 10 I

1 32.438 22.131 41.691 23.851 43.451 24.s88 42.601 24.081 43.451 23.851 41.691 22.131 32.438 Il l 38.831 18.781 22.791 43.231 23.281 41.538 37.581 41.721 23.451 42.55l 23.161 19.321 38.318 11 l 38.251 18.871 22.691 42.191 23.841 4I.151 38.098 42.151 23.841 42.791 22.698 18.871 38.251 12 1 40.951 36.410 22.701 41.371 23.328 42.30i 23.421 40.841 22.351 36.768 41.541 12 1 49.991 36.081 22.678 41.631 24.108 47.888 24.101 41.631 22.678 %.081 40.991

=.-

13 8 41.461 19.378 22.05l 38.498 22.211 38.078 21.161 18.548 40.961 13 1 40.994 18.851 22.121 39.148 23.144 39.148 22.128 18.851 40.991 I

14 1 38.691 33.051 18.851 34.341 18.371 32.361 38.251 14 8 38.111 32.451 19.001 34. % ! 19.001 32.45! 18.111 15 1 34.931 29.f;01 38.051 15 1 38.301 29.678 38.301 I

R P

N M

L E

J H

G F

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C 8

8 I

I I

g Ns.e,2 N2ce c...

1e., e

I.

l I

l Figure 2.4 NORTH ANNA UNIT 2 - CYCLE 6 ASSEMBLYWISE ACCUMULATED BURNUP I

COMPARISON OF MEASURED AND PREDICTED (1000 MWD /MTU) 4 P

N M

1 K

J H

G F

E D

C 8

A

.8 1

1 34.651 30.071 Sa.4st I ntasun[D 1 1

t 0.921 1.381 0.33l l M/P 2 DIFF I 2

1 38.111 32.101 18.741 34.111 14.971 33.021 3a.381 2

I l -0.001 -1.091 -1.M1 -0.751 -0.161 1.761 0.711 3

1 41.471 18.851 21.511 38.861 22.631 39.03l 22.381 19.291 41.551 3

1 1.171 +0.021 -2.778 -0.701 -2.241 -0.291 1.161 2.321 1.38)

...................................... =

4 1 41.23 3 M.191 22.431 41.36l 23.811 42.711 23.761 42.191 22.69 8 34.641 41.681 4

8 1 0.574 0.298 8.711 -0.641 -1,211 -0.391 -1.411 1.368 0.071 1.101 1.ul 5

1 34.621 18.691 22.161 42.401 23.321 42.411 38.368 42.378 23.961 42.83! 22.301 18.711 38.171 5

i f.961 -0.9f.1 -2.331 -0.891 -2.181 0.628 0.721 0.521 0.508 0.111 -1.741 -0.831 -0.228 6

1 32.941 22.08 t 41.56l 23.351 43.591 24.111 42.70i 24.171 43.821 23.451 41.091 21.72 8 32.421 6

.I I 1.601 -0.295 -0.311 -2.101 0.345 0.131 0.251 0.39i 8.861 -1.708 -1.431 -1.861 1.221

...................................e.

7 1 38.291 18.971 34.431 23.471 42.101 23.531 43.601 23.601 43.781 24.161 41.601 23.071 38.691 18.401 38.64l 7

1 0.331 -0.16) 1.F91 -2.651 -0.141 -2.281 8.421 0.541 0.4hl 0.361 -1.341 4.271 -1.141 -3.181 3.351 8

1 29.761 32.151 22.551 42.751 34.111 42.651 23.371 %8.041 23.181 42.681 37.451 41.841 22.451 34.231 29.771 8

I 4 1.261 ~3.061 -2.541 -0.191 -0.418 +0.271 -0.428 8.781 -1.201 -0.181 *1.074 -2.311 -3.031 3.221 1.271 9

1 34.351 M.62l 38.48i 23.431 42.081 23.631 42.431 27.861 45.091 23.661 42.04l 23.691 39.221 19.158 38.401 9

1 0.478 -2.031 -1.668 2.801 0.181 1.861 -1.338 -2.651 -0.741 -1.731 -0.308 -1.731 0.234 0.778 0.621 I

le 1 31.901 21.25i 41.238 23.471 43.24l 23.581 42.351 23.528 42.471 23.638 42.281 22.571 32.641 le

! -1.631 -3.991 -1.111 0.068 -0.341 2.061 -0.571 -2.328 -1.131 -0.941 1.401 1.981 0.661 Il 1 38.831 18.781 22.791 43.231 23.284 41.531 37.544 41.72l 23.458 42.551 23.161 19.321 38.311 11 1 1.501 -0.441 0.454 1.051 -2.351 1.461 -1.331 -1.021 *1.661 -0.551 2.071 2.410 0.151 I

12 1 40.95 8 36.41 f 22.701 41.371 23.321 42.301 23.44 4 40.841 22.35 8 36.761 41.54 l 12 l -0.101 0.911 0.131 -0.611 3.241 -1.541 -2.821 -1.891 -1.444 1.471 1.338 13 1 41.461 19.371 22.05) 34.493 22.211 36.078 21.361 19.54l 40.961 13 1 1.141 2.751

................- 0.311 -1.64 8 -4. 031 - 2. 741 3.461 -1.651 - 0.081 1 ARITHMETIC AVG I l PCT DIFF = -0.44l I

14 i 38.691 33.051 18.851 34.341 18.371 32.361 38.251 14 l 1.511 1.868 -0.421 -0.061 -3.348 -0.271 0.361 15 i $IANDARD DEW l 1 38.938 29.80f 38.051 l evs ASS PCT 1 15 I

= 0.95 t

i 1.634 0.661

................-0.654 1 Dirr. 1.24 I I.

R P

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L K

J H

G F

[

D C

8 A

I BATCH $ HARING utwu/nlut I

BATCl?

CYCLE 3 CYCLE 4 CYCLE 5 CYCLE 6 TOTALS N1/SA5 7540 29852 BURNUP TILT N1/6A7 19423 55081 SA2 18586 8154 6680

6515

'39915 NW 8 -0.01 NE = +0.36 I

20247 11460 6712 56419 6A2 7A 22291 18115 40406 OW s -0.17 SE * -0.18 78 19542 19036 58578 BA 22258 22258 21770 21770 88 CORE AVERACE a 17C44 I

NE-692 "2C6 Core Performance Report Page 17 of 48

I Figure 2.5A NORTH ANNA UNIT 2 - CYCLE 6 SUE-BATCH BURNUP SHARING I

SUB-BATCH g.

44 i

i i

l N1/5A 40 l

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m i

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8 10 12 14 16 18 CYCLE BURNUP (GWd/MtU)

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Figure 2.5B l

NORTH ANNA UNIT 2 - CYCLE 6 I

SUB-BATCH BURNUP SHARING I

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NE-692 N2C6 Core Performance Report Page 19 of 48

l Section 3 1

I REACTIVITY DE,LETIONL

)

The primary coolant critical boron concentration is soaitored for the i

purposes of following core reactivity. and to identify any anomalous j

reactivity behavior. The FOLLOW' computer code was used to normalize

" actual"' critical boron concentration measurements to design conditions itaking into consideration control rod position, xenon concentration,

-l moderator temperature, and power level.

The normalized critical boron concentration'versus'burnup curve for the North Anna 2, Cycle 6 core is shown in Figure 3.1.

It can be seen that the measured data typically compare to within 37 ppm of the design prediction. This : corresponds to -

10.25%. AK/K which is within the 11% AK/K. criterion for reactivity.

anomalies set forth in Section 4.1.1.1.2 of the Technical Specifications.

In conclusion, the trend indicated by the critical boron concentration verifies that the Cycle 6 core depleted as expected without any reactivity anomalies.

[

}

)-

se.,2 x2ce core,er,ormance.. port ra,e 2e of.e

I.

I Figure 3.1 NORTH ANNA UNIT 2 - CYCLE 6 CRITICAL BORON CONCENTRATION vs. BURNUP (HFP,ARO)

I 1800 i

PREDICTED 1700 h 1600 MEASURED 1500 I

1400

=

wl I

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i Section 4 POWER DISTRIBUTION r

t Analysis of core power distribution data on a routine basis is necessary to verify that the hot channel factors are within the Technical Specifications limits and to ensure that the reactor is operating without any abnormal conditions which could cause an

" uneven" burnup distribution. Three-dimensional core power distribution is determined from movable detector flux map measurements using the INCORE' computer program. A summary of all full core flux maps taken since the completion of startup physics testing for North Anna 2, Cycle 6 is given in Table 4.1.

Power distribution maps were generally taken at monthly intervals with additional maps taken as needed.

I Radial (X-Y) core power distribution for e representative series of incore flux maps are given in Figures 4.1, 4.2, and 4.3.

Figure 4.1 shows a power distribution map that was taken early in cycle life. Figure 4.2 shows a power distribution map that was taken near mid cycle burnup.

Figure 4.3 shows a map that was taken near the end of Cycle 6.

The measured relative assembly powers were generally within 4.P. and the maximum average percent difference was equal to 2.0*..

In addition, as indicated by the INCORE tilt. factors, 'the power distribution was essentially symmetric for all cases.

I An important aspect of core power distribution follow is the monitoring of nuclear hot channel factors.

Verification that these factors are NE-692 N2C6 Core Performance Report Page 22 of 48

. 49 I:

I within Technical Specifications limits ensures that linear power density and critical heat flux limits are not violated, thereby providing adequate thermal margin and maintaining fuel cladding integrity.

North Anna 2 Technical Specification 3.2.2 limited the axially dependent heat flux hot channel factor, F (Z), to 2.15 x K(Z), where K(Z) is the hot channel q

factor normalized operating envelope.

Figure 4.4 is a plot of the K(Z) curve associated with the 2.15 F (Z) limit. Near the end of Cycle 6, this q

limit was increased to 2.19 x K(Z), but was administrative 1y maintained at the 2.15 x K(Z) limit throughout the cycle. The axially dependent heat flux hot channel factors, F (Z), for a representative set of flux maps q

are given in Figures 4.5, 4.6, and 4.7.

Throughout Cycle 6, the measured values of F (Z) were within the Technical Specifications limit. A summary q

of the maximum values of axially-dependent heat flux hot channel factors measured during Cycle 6 is given in Figure 4.8.

This figure indicates that the minimum margin to the Fq limit in the axial region covered by Technical Specification 4.2.2.2 is 13.27%. (Technical Specification 4.2.2.2.g states that Fq surveillance is not applicable in the lower core region from 0% to 15% inclusive, and the upper core region from 85% to

.l W

100% inclusive.)

I Figure 4.9 shows the maximum values for the heat flux hot channel factor measured during Cycle 6.

As can be seen from the figure, there was an approximate 13.6% margin 4from the ma'ximum F (Z) to the 2.15 limit q

.I at the beginning of the cycle, with the margin generally increasing throughout cycle operation.

The F (Z) increases seen at EOC in Figure 9

4.9 are a result of the coastdown.

The reduced power level at the time of the measurement of those points would result in an F limit that is q

3 st.,2 x2ce core Ferfo,mance,e, ort Fage 23 of 4e

g a

greater than 2.15.

This F limit increase would offset the F (Z) increase q

g at EOC, therefore, the BOC margin would still be the minimum.

During flux map analysis the measured F (Z) is increased by an N(Z) q function to verify compliance with Technical Specification 4.2.2.2. The N(Z) function covers all possible power distributions within the delta flux limits.

Maps 9, 10, 11 and 12 showed F (Z) exceeded the F limit q

q after the N(Z) function was applied, which resulted in minor redu:tions I

in the axial flux difference band.

Map 9 also showed an increase in F (Z)/K(Z) over the previous month's F (Z)/K(Z), which resulted in an q

q additional flux map having been taken within 7 EFPD in order to show a reduction in F (Z)/K(Z). Map 15 showed an increase in F (Z)/K(Z) which 9

9 resulted in a minor reduction in the axial flux difference band.

Maps 25 and 26 also showed an increase in F (Z)/K(Z), but were resolved by q

increasing F (Z) by 2%.

g I

The value of the enthalpy rise hot channel factor, F-delta-H, which is the ratio of the integral of the power along the rod with the highest integrated power to that of the average rod, is routinely followed. The Technical Specifications limit for this parameter is set such that the departure from nucleate boiling ratio (DNBR) limit will not be violated.

Additionally, the F-delta-H limi,t ensures that the value of this parameter used in the LOCA-ECCS analysis is not exceeded during normal operation.

North Anna Technical Specification 3.2.3 limited the enthalpy rise hot I-channel factor to 1. 9(1+0.3(1-P))'for Cycle 6.

A summary of the maximum values for the enthalpy rise hot channel factor measured during Cycle 6 g

Ns.e92 N2ce core performance,e,o,t ease 2.

o, e

?.

4-is given in Figure 4.10.

As can be seen from this figure, the average margin to the limit was approximately 3.6%.

The target delta flux

is the delta flux which would occur at conditions of full power, all rods out, and equillorium xenon. The delta flux is measured with the core at or near these conditions and the target delta flux is established at this measured point. Since the target delta flux varies as a function of burnup, the target value is updated monthly.

By maintaining the value of delta flun relatively constant, adverse axial power shapes due to xenon redistribution are avoided.

The plot of the target delta flux versus burnup, given in Figure 4.11, shows the value of this parameter to have been approximately -2.6% at the beginning of Cycle 6.

Delta flux values decreased steadily to -5.2% near the middle of the cycle, then gradually increased to -3.6% before the coastdown. At the end of Cycle 6, the target delta flux increased to +11.6 due to the coastdown. This axial power shift can also be observed in the corresponding core average' axial power distribution for a representative i

series of maps given in Figures 4.12 through 4.14.

In Map N2-6-04 (Figure 4.12), taken at 222 MWD /MTU, the axial power distributicr. had a shape peaked toward the middle of the core with a peaking factor of 1.223.

In e

Map N2-6-16 (Figure 4.13), taken at approximately 8,586 MWD /MTU, the axial 1

power distribution peaked slightly toward the bottom of the core with an I

axial peaking factor of 1.164.

Finally, in Map N2-6-24 (Figure 4.14),

taken at 15,516 MWD /MTU, the axial peaking factor was 1.153, with axial Pt-Pb

Delta Flux = ----- X 100 where Pt = power in top of core (MW(t))

2893 Pb = power in bottom of core (MW(t))

NE-692 N2C6 Core Performance Report Page 25 of 48

2 -

i g,

vi,(

>i

.3 -

power' distribution shifted slightly back toward the top. The history of F-Z during the cycle can be seen more clearly in a plot of F-Z versus i

burnup given in Figure 4.15.

in conclusion, the North' Anna 2, Cycle 6 core performed satisfactorily with power distribution. analyses verifying that design predictions were accurate and that the. values of the F (Z) and F-delta-H hot ~ channel q

factors were within the-limits'of the Technical Specifications.

~.

l.

p' NE-692-N2C6 Core Performance Report Page 26 of 48 rii iiFi iii

'rg

-r

Table 4.1 NORTH ANNA UNIT 2 - CYCLE 6

SUMMARY

OF FLUX MAPS FOR ROUTINE OPERATION I

i i

i i i

)

i i

l 8

l l SURNI. 4 i. CHANNEL FACTOR l CHNL. FACTOR l

MAX l

21 OPTR 1 AX1All NO.1 F-0(T) HDT l F-BH(M) NOT ICORE F(F1 I l

3I i

l l MAP l

l UP l 18ANK i IMD.

I DATE l MWD /IPWRI D l l

l IF(NY)1 1 0FF l DF i l

i 1 MTU l(2)lSTEP$1AssylPINlAA1ALl l AS$VlPintf.-DH(M)l AX1At t f(211 1 MAK ILOCl SET lTHIMI I

l l

l 8

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l 1POINil

' i l

l

( (El ISLESI I

I l

II l

l

_l i

1.,,_

l I I

i i

i I,,_l 1

_t i e4 111-16-871 22211001 2r8 i L831 MCI 36 1 1.857 i t83 NCl 1.396 4 37 11.t:311.414 t a.009 4 MWl-2.5591 47 1 1 95 111-23-871 50281004 Z28 i Dill IPl 37 l 1.843 i C108 811 1.397 8 37 11.21411.40781.0101 Nul-2.5338 47 8 1 09( 41112-16-871 142581001 TF8 i D118 IPl 38 l 1.849 i C101 Bil 1.403 1 37 11.21481.41211.0071 MWl-3.r811 46 8 1 10 112-18-871 15e011004 FF8 i Dill 3Pl 38 l 1.843 1 0119 IPl 1.401 1 3711.20911.40981.0081 MWi-2.893147 l l Il 101-15-881 259911001 l'8 i D111 IPl 38 9 1.822 1 J061 eel 1.410 1 3711.19281.41611.0061 NWi-2.975146 l l

l 12 102-19-881 387011001 228 i F071 EMI. 38 l 1.814 1 Joel eel 1.428 6 38 11.17981.43411.0058 W l-3.5798 4 l 8 13 103-17-886 493011004 ZF8 1 CD61 NEl 45 1 1.818 i G061 NEl 1.434 1 45 11.16711.44281.0061 NEl-3.8711 46 l l 14 104-18-888 620111001 228 i G06l MEl 45 1 1.786 i G061 IEl 1.434 1 46 11.14911.44281.0041 MWl-3.1871 % 1 1 15 105-17-881 731381001 228 1 G061 MEl 471 1.811 l Go6l MEl 1.4381 47 11.16311.45011.0061 NEl-4.6038 45 1 4 16 106-17-881858611001 !?8 i Cc61 MEl 47 l 1.804 l C068 MEl 1.4321 47 11.164 t !.43911.0051 NE l-4.7671 46 1 1 17 107-18-881 983011001 228 i C061 MEl 48 l 1.791 1 Mc71 IH] 1.427 4 ' 48 !!.15811.438 61.0051 NEl-4.7441 45 l l 18 10811-8811075311001228 i F051 H21 48 8 1.790 i H071 IH1 1.421 1 48 11.15911.42911.008l NEl-4.9271 45 l l 218 41109-09-8811192611001 7281 H071 IHi 53 1 1.779 i H071 INI 1.411 1 53 11.15711.42511.0068 NEl-5.0798 43 l l 22 110-11-8811317511001 (28 4 H071 IH1 53 4 1.779 i H078 1HI 1.396 1 53 11.16881.41011.0031 NEl-5.2401 45 i 1 23 111-14-8811453511001228 i H078 IH1 53 l 1.728 l H07) IH1 1.377 1 53 11.15881.39281.0034 NEl-4.2811 45 l l F4 112-09-88l1551611001 228 1 D098 IHf 54 l 1.712 i H071 IHi 1.369 I 53 11.15311.38411.0041 NEl-3.5701 46 l 1 25 101-11-891167201 821 228 i Clet DMI 11 1 1.792 l C101 DMI 1.376 8 11 11.19581.38411.0094 NEl 5.9381 42 1 1 26 102-06-89117t871 704 228 l J084 JIl le i 1.912 i Fell EDI 1.369 8 11 11.285tl.14811.0011 SW1 11.57141 l

'I i

1 l_l lll I

l,,,,,,_1_ l l

l I

I l_1 f,,,. !

NOTE $1 HOT $ POT LOCATIONS ARE SPECIFIED BY CIVING A$$EMBLY LOCATIONS (E.C. H-8 IS THE CENTER-OF-CORE ASSEMBLV),

FOLLONED BY THE PIN LOCATION (DENOTED BY THE "Y" CDDRDINATE WITH THE $EVENTEEN ROWS OF FUEL RODS LETTERED A TNPOUGH R AND THE *** COORDINATE DESIGMATED IN A SIMIL AR MANNER).

IN THE *2" DIRECTION THE CORE IS DIVIDED INTO 61 AMIAL POINTS $7ARijMG FROM THE TOP OF THE CORE.

1. F-Oti) INCLUDES A TOTAL UNCERTAINTY OF 1.05 N 1.03.

3. F(XVI IS EVALUATED AT THE MIDPLANE OF THE CORE.

3. OPTR - GUADRANT POWER TILT RATIO.

4. MAPS 6, 7, 8,19 AND 20 WERE DUARTER-CDRE FLUM 44APS TAKEN FOR INCORE/EXCORE CALIBRATION. (I/E CALIBRATION) l l

i NE-692 N2C6 Core Perfortnarice Report Page 27 of 48 l

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l NE-692 N2C6 Core Performance Report Page 31 of 48 l

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Figure 4.5 NORTH ANNA UNIT 2 - CYCLE 6 HEAT TLUX HOT. CHANNEL FACTOR, F (Z) n N2-6-04 t

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'I Figure 4.6 NORTH ANNA UNIT 2 - CYCLE 6

. HEAT FLUX HOT CHANNEL FACTOR, F (Z) q N2-6-16 2.50--

ll::::

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NE-692 N2C6 Core Performance Report Page 33 of 48

,a rigure 4.7

.g-NORTH ANNA UNIT 2 - CYCLE 6 E

"IAT rtux nor.CniNNtt rtCroR, r <z:

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Nt-692 N2C6 Core Performance Report Page 34 of 48

a Figure 4.8 NORTH ANNA UNIT 2 - CYCLE 6 I

MAXIMUM HEAT FLUX HOT CHANNEL FACTOR, F (2)*P, vs. AXIAL POSITION q

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RnTTng nr ener Tnp or enpr NE-692 N2C6 Core Performance Report Page 35 of 48

.;l I

risure 4.9 NORTH ANNA UNIT 2 - CYCLE 6 MAXIMUM HEAT FLUX HOT CHANNEL FACTOR, F (Z), vs. BURNUP q

I g 2.2

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l NE-692 N2C6 Core Performance Report Page 36 of 48

Figure 4.10 I'

NORTH ANNA UNIT 2 - CYCLE 6 MAXIMUM ENTHALPY RISE HOT CHANNEL FACTOR, F-delta-H, vs. BURNUP I

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60 55 50 45 40 35 BOTTOW AX1AL POSITION (NODES)

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p

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NE-692 N2C6 Core Performance Report Page 41 of 48

Figure 4.15 g

NORTH ANNA UNIT 2 - CYCLE 6 g

CORE AVERAGE AXIAL PEAKING FACTOR vs. BURNUP 14 j

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I NE-692 N2C6 Core Performance Report Page 42 of 48

3 Section S

{

L PRIMARY COOLANT ACTIVITY 1.

Activity levels of iodine-131 and 133 in the primary coolant are important in core performance follow analysis because they are used as indicators of defective fuel.

Additionally, they are important with respect to the offsite dose calculation values associated with accident analyses.

Both I-131 and I-133 can diffuse into the primary coolant I.

system through a breach in the cladding.

As indicated in North Anna 2 Technical Specification 3.4.8, the dose equivalent I-131 concentration in the primary coolant is limited to 1.0 pCi/gm for normal steady state operation.

Figure 5.1 shows the dose equivalent I-131 activity level history _for the North Anna 2, Cycle 6 core. The demineralized flow rate averaged 88.3 gpm during power operation.

These data show that during Cycle 6, the core operated substantially below the 1.0 pC1/gm Technical Specifications limit during steady state operation.

Specifically, the average dose equivalent I-131 concentration was 6.2 x 10~3 pCi/gm which corresponds to less than 1*. of the Technical Specifications limit.

I The ratio of the specific activities of I-131 to I-133 is used to characterize the type of fuel failure which may have occurred in the reactor core. Use of the ratio for this determination is feasible because i

I-133 has a short half-life (approximately 21 hours2.430556e-4 days <br />0.00583 hours <br />3.472222e-5 weeks <br />7.9905e-6 months <br />) compared to that of I-131 (approximately eight days).

For pinhole defects, where the diffusion time through the defect is on the order of days, the I-133 decays leaving the I-131 dominant in activity, thereby causing the ratio NE-692 N2C6 Core Performance Report Page 43 of 48

to be 0.5 or more. In the case of large leaks and " tramp"* material, where the diffusion mechanism is negligible, the I-131/I-133 ratio will generally be less than 0.1.

Figure 5.2 shows the I-131/I-133 ratio data for the North Anna 2, Cycle 6 core at a general average value of 0.09.

However, due to the very low radioiodine concentration in the coolant, an lodine ratio of 0.09 is' not indicative of fuel defects. Tramp iodine analysis resulted in a corrected iodine-131 concentration of 9.86 x 10-5 pCi/gm.

This value indicates no defective fuel rods in the core.

1 i

l

" Tramp" consists of fissionable material as an impurity in the reactor core materials or fissionable material which has adhered to the surface of reactor core components.

NE-692 N2C6 Core Performance Report Page 44 of 48 b

I.

Figure 5.1 NORTH ANNA UNIT 2 - CYCLE 6 DOSE EQUIVALENT I-131 vs. TIME i

1.00E+00.

1.00E-01.

O I

5

.00E-02.

g 1 ee g

i e.

e 1.00E-00.

X

(

8 I

1.00E-04.

r

=

e i

i l

e

" # ae O

"N

=

r w

.g I*

~~

p.

27AUG87 05DEC87 14MAE88 222UN88 30EE?88 08JJN89 18 APE 89 I

I "t-69 "2c' c r r -r -

rt e-

's "8

Figure 5.2 NORTH ANNA UNIT 2 - CYCLE 6 I-131 / I-133 ACTIVITY RATIO vs. TIME 0.7 k

e 0.s l

0.5 e

o h 0.4 a

E T

5 r2 70.s 0.2 e

e e

e s

e e e

e e,e El e e

,g e

e 0.0 '

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a i

i i

27AUG87 05DEC87 14MAE88 222UN88 30EEP88 082AN89 18/1PB89 DATE 1

NE-692 N2C6 Core Performance Report Page 46 of 48

Section 6 I

CONCLUSIONS The North Anna 2, Cycle 6 core tias completed oparation.

Throughout this cycle, all core performance indicators compared favorably with the design predictions and the core related Technical Specifications lir.its were met with significant margin.

No significant abnormalities in reactivity or burnup accumulation were detected.

Radiciodine analysis indicated that there were no fuel rod defects during Cycle 6.

NE-692 N2C6 Core Performance Report Page 47 of 48

{

i.

).

Section 7 REFERENCES 1)

M. K. Farley, " North Anna Unit 2, Cycle 6 Startup Physics Test Report," VEP-NOS-38, January, 1988.

2) North Anna Power Station Unit 2 Technical Specifications, Sections 3/4.1, 3/4.2 and 3/4.4.8.

3)

T. K. Ross, "NEWTOTE Code", VEPCO NFO-CCR-6, Rev. 9, April, 1984.

4)

R. D. Klatt, W. D. Leggett, III, and L. D. Eisenhart,

" FOLLOW Code," WCAP-7482, February, 1970.

5)

W. D. Leggett, III and L. D. Eisenhart, "INCORE Code,"

WCAP-7149, December, 1967.

6)' D. A. Trace, " North Anna 2 Cycle 6 Core Performance Calculations",

NAF Calculational Report PM-254, Rev. O March, 1989.

l l

i l

t.

1 NE-692 N2C6 Core Performance Report Page 48 of 48

- _ _ - - _ _ _ _ _

ML20245L093

Text

SUMMARY

==

SUMMARY

="

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