Text

Cycle 2 Core Performance Rept
	ML20069K367
Person / Time
Site:	North Anna
Issue date:	04/30/1983
From:	Mann B; VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	;
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ML20069K360	List: ML20069K356; ML20069K367;
References
	VEP-NOS-3, NUDOCS 8304260320
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CORE PERFORMANCEL 2: DtEPORILE F

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,u NUCLEAR OPERATIONS DEPARTMENT s.

Virginia; Electric and Power Company

VEP-NOS-3 NORTH ANNA UNIT 2, CYCLE 2 CORE PERFORMANCE REPORT by Brian D. Mann Reviewed: Approved:

C. A L C. T. Snow, Supervisor

[/rdvh E/ J . Lopff/, Director 1

L Nuclear Fuel Operation clear Ftter Operation

( Nuclear Fuel Operation Subsection Nuclear Operations Department Virginia Electric f, Power Company Richmond, Virginia Ap ril, 1983

i .

CLASSIFICATION / DISCLAIMER The data, techniques, information, and conclusions in this report have been prepared solely for use by the Virginia Electric and Power Company (the Company), and they may not be appropriate 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 accu racy, 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, with respect to this report or any of the data, techniques, information, or conclusions in it. By making this report available, the Company does not authorize its use by others, and any such use is express'ly forbidden except with the prior 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 damage resulting from or arising out of the use, authorized or unauthorized, of this report or the data, techniques, information, or conclusions in it.

i

ACKNOWLEDGEMENTS The author would like to acknowledge the cooperation of the North Anna Power Station personnel in supplying the basic data for this report.

Also, the author would like to express his gratitude to Mr. C. T. Snow and Dr. E. J. Lozito for their aid and guidance in preparing this report.

x-x ii '

9 TABLE OF CONTENTS SECTION TITII PAGE NO.

l Classification / Disclaimer . . . . . . . . . . . .i Acknowledgements . . . . . . . . . . . . . . . 11 List of Tables .... . . . . . . . . . . . . . iv List of Figures ..... . . . . . . . . . . . .v 1 Introduction and Summary. . . . . . . . . . . . . 1 2 Burnup Follow . ............ . . . .7 3 Reactivity Depletion Follow . . . . . . . . . . 14 4 Power Distribution Follow . . . . . . . . . . . 16 5 Primary Coolant Activity Follow . . . . . . . . . 38 6 Conclusions .......... . . . . . . . . . 42 7 References. ............ . . . . . . . 43 e

iii

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.P LIST OF TABLES TABLE TITLE PAGE NO.

4.1 Summary of Flux Maps for Routine Operation . . . . . . . . . 20 S

iv

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LIST OF FIGURES FIGURE TITLE PAGE NO.

1.1 Core Loading Map . . . ................... 4 l

1.2 Movable Detector and Thermocouple Locations. . . . . . . . .5 1.3 Control Rod Locations. . . . . . . . . ........... 6 2.1 Core Burnup History . . . . . . . . . . . . . . . . . . . . .9 2.2 Monthly Average Load Factor. . . . . . . . . . . . . . . . . . 10 2.3 Assemblywise Accumulated Burnup: Measured and Predicted . . . 11 2.4 Assemblywise Accumulated Burnup: Comparison of Measured and Predicted . . . . . . . . . . . . . . . . . . . . 12 2.5 Sub-Batch Burnup Sharing . . . . . . . . . . . . . . . . . . 13 3.1 Critical Baron Concentration versus Burnup - HFP-ARO . . . . . 15 4.1 Assemblywise Power Distribution - N2-2-16 . . . . . . . . 22 4.2 Assemblywise Power Distribution - N2-2-21 . . . . . . . . . . 23 4.3 Assemblywise Power Distribution - N2-2-30 . . . . . . . . . . 24 4.4 Hot Channel Factor Normalized Operating Envelope for a Fq(Z) Limit of 2.14. . . . . . . . . . . . . . . 25 4.5 Hot Channel Factor Normalized Operating Envelope for a Fq(Z) Limit of 2.20. . . . . . . . . . . . . . . . . . 26 4.6 Heat Flux Hot Channel Factor, F (Z) - N2-2-16. . . . . . . 27 4.7 Heat Flux Hot Channel Factor, F (Z) - N2-2-21. . . . . . . . . 28 4.8 Heat Flux Hot Channel Factor, F (Z) - N2-2-30. . . . . . . . . 29 4.9 Maximum Heat Flux Hot Channel Factor, F q*P, vs.

Axial Position . .................. . . . . 30 4.10 Maximum Heat Flux Hot Channel Factor versus Burnup . . . 31 4.11 Enthalpy Rise Hot Channel Factor versus Burnup . . . . . 32 4.12 Target Delta Flux versus Burnup . . . . . . . . . . . . . . 33 v

LIST OF FIGURES CONT'D FIGURE TITLE PAGE NO.

4.13 Core Average Axial Power Distribution - N2-2-16 . . . . . . . 34 4.14 Core Average Axial Power Distribution - N2-2-21 . . . . . . . 35 4.15 Core Average Axial Power Distribution - N2-2-30 . . . . . . . 36 4.16 Core Average Axial Peaking Factor versus Burnup . . . . . . . 37 5.1 Dose Equivalent I'131 versus Time

. . . . . . . . . . . . . . 40 5.2 I-131/I-133 Activity Ratio versus Time . . . . . . . . . . . 41

{

vi

Section 1 l

1 INTRODUCTION AND

SUMMARY

On April 2,1983, North Anna Unit 2 completed Cycle 2. Since the initial criticality of Cycle 2 on July 2, 1982, the reactor core produced approximately 50 x 10' MBTU (8,436 Megawatt days per metric ton of contained uranium) which has resulted in the generation of approximately 4.8 x 10' KWHR gross (4.6 x 10' KWHR net) of electrical energy. The purpose of this report is to present an analysis of the core performance for routine operation du ring Cycle 2. The physics tests that were performed during the startup of this cycle were covered in the North Anna Unit 2, Cycle 2 Startup Physics Test Report and, 1 therefore, will not be included here.

The second cycle core consisted of five batches of fuel. The North Anna 2, Cycle 2 core loading map specifying the fuel batch identification, fuel assembly locations, burnable poison locations and source assembly locations is shown in Figu re 1.1. Movable detector locations and thermocouple locations are identified in Figure 1.2. Control rod locations are shown in Figure 1.3.

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 is followed to 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 1

monitored to detect 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 2

are within the Techr.ical Specifications limits thereby ensuring that adequate margins to linear power density and critical heat flux thermal limits are maintained. Lastly, as part of normal core follow, the primary coolant activity is monitored to verify that the dose equivalent iodine-131 concentration is within 'the limits specified by the North Anna Unit 2 Technical Specifications, and to assess the integrity of the fuel.

Each of the four performance indicators is discussed in detail for the

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North Anna 2, Cycle 2 core in the body of this report. The results are .

summarized below:

1. Burnup Follow - The burnup tilt (deviation from quadrant symmetry) on the core was no greater than 0.31% with the burnup accumulation in each batch deviating from design prediction by less than 3.2%.

2. Reactivity Depletion Follow -

The critical boron concentration, used to monitor reactivity depletion, was consistently within 20.47% AK/K of the design prediction which is well within the !1%

AK/K margin allowed by Section 4.1.1.1.2 of the Technical Specifications.

' 3. Power Distribution Follow - Incore flux maps taken each month indicated that the assemblywise radial power distributions deviated from the design predictions by an average difference of less than 4%.

The radial heat flux hot channel factor, F-XY, which violated its su rveillance limits during the first third of the cycle, is described in Section 4 of this report. All hot channel factors met their respective Technical Specifications limits.

2

4. Prima ry Coolant Activity Follow - The average dose equivalent iodine-131 activity level in the primary coolant during Cycle 2 was approximately 4.0 x 10-2 pCi/gm. This corresponds to 4*o of the operating limit for the concentration of radioiodine in the primary coolant.

In addition, the effects of fuel densification were monitored throughout the cycle. No densification effects were observed.

3

Figure 1.1 NORTH ANNA UNIT 2 - CYCLE 2 CORE LOADING MAP R P .M N L E J N 4 F E B C S A i se, ton ino i i i 1 I are I ase l,i 1 I I I as l use i ms1 ep i I a17 8 ma7 1 1 8 I er i I I e i I l 1 I I I i 1 als Ii met I net i _NMi eQ7 8 Mll l Mle i se3 8 att i 1 trP I l I as i 1 I lip I I 3 I I I I I I I I l i Ien I 1 IPts I was I lP I u 8,1P16 i 1F31 1PM i me $ Mu 1 714 8 aos 1 I i 1 I I I e i I I I I I I I l_t i I I1 au I lallItpi soa i i neoI 1 P17 i i Poe i i iese 41 Poe 1i ms I woe i use Ii m3e i ets I I i 1 I tap i l s 1 1 I I I I I I 1 a*7 Il me, I par 1 Poe i noe i Pse I use 1 Pts i Mar a rat i Ps1 i estI I als ii I I I i 1 1 i er I i er I i I I I I e I I i I I I I I I t I i l i II ase II asa a me ii M7 i Poe i Pte l wt, 1 Pos I ace 1 Pse i P33 i Pts i Mal 4 sea e als i i I er l I I I

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I i 4 al, I a., se, li i 1-> ASSEMBLY ro l I I I l--> ONE OF THE POLLOWINGt i l i is I I A. SS - SECDCART $O0PCI

B. XXp - St.pHASLE POISON ASSEteLY exx - eareta or aOoss i

SUB-BATCH 1A2 2A2 3A N1/3A3 4A INITIAL. D4IICHMENT (W/0 U235 8 2.110 2.600 3.100 3.102 3.414 ASSDSLY TYPg 17X17 17X17 17X17 17X17 17X17 lArsER OF ASSDSLIES 1 50 52 2 52 FUEL RODS PER ASSEISLY 264 264 264 264 264 ASSDSLY IDENTIFICATI0H L51 H01-H02, P01-PS2 C22 R01-R52 N04-H06, C31 H08-H52 4

Figure 1.2 NORTH ANNA UNIT 2 - CYCLE 2 MOVABLE DETECTOR AND THERMOCOUPLE LOCATIONS

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R P N M L K J H G F E D C 8 A 1 I I I te Tc 1 1 1 1 I i 1 1 1 1 TC 1 1 Tc MD l I a l l I I L I I to a a i m I i to i TC 1 l TC 1 te i Tc I Tc I Tc 3 1 1 1 I I I I I I I I I I I I i 1 i i i Tc I I te i i 1 te i I re 1 Tc I I i 4 1 1 l i I I I I I I I I i 1 I i l i i i m i I re I l I re I i re i Tc 1 te 1 TC 1 Tc 1 to Tc I I Tc I s i I I l I I I .I i 1 I l 1 I I re i i 8 i i i i l I I I Tc I Tc 1 1 I re l Tc I te 1 1 1 1 6 I I l I l I I I I I I I I i i 1 i 1 i i 1 1 - l' I I i 1 Tc I Tc I te I I i i re I i to 1- l Tc 11 te i I te I i 7 I I I I I I i i i I 11 I I I I I I re i i to 1 I i 11 1 1 1 I re I i i i to Tc I Tc 1 1 Tc I Tc 1 l Tc 11 TC 1 re i Tc I I Tc I te i Tc I e i l i l I I I I i l I I I I 1 I i 1 8 8 1 1 4 i i 1 i i l i Tc 1 te i 1 1 Tc , te I ic 1 1 1 1 to 9 I l i I I I I l I I I I I I I re i I I I re 1 1 I i i to i i 1 Tc 1 1 1 1 Tc 1 1 1 Tc re 1 l Tc i to i l I I I I I I I I i 1 1 I I I I I I m i im I I I 1 I 1 i i Tc I e9 1 Tc I I Tc I I Tc I re I 1 i i 11 1 l i I I I I I I l i I I I i 1 i 1 I m I i i i i i e 1 i re i 1 TC i 1 TC 1 I i 1 Tc I te i Tc I la 1 l ! I I I I I I I I I I i i i i m I i m I i i l 1 1 I I Tc I I Tc 1 1 1 13 1 'I I I i i I l I I I m i I i i i 1 1 I Tc 1 1 ,1 I re 1 I Tc I 14 1 l i I I I I I re - MovAsLE crTtcTom I i I i TC - TMsareCOUPLE I re l Tc 1 Tc 1 15 I l i I i

5

Figure 1.3 NORTH ANNA UNIT 2 - CYCLE 2 CONTROL ROD LOCATIONS R P N N L K J H G F E D C B A 180*

l LOOP C l l l l LOOP B 1 OUTLET l l l l INLET N-41 Ni l l l^!l SA l!" ll SA ll' ll SP l!/

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IC I I I Ie i I I I I I l. I I l lB I lC l l 4 I I I I I I I I I I I I I I I I SB l i SP l l l l Se l I l l 5 I I l i I I I I I I I I I I lA l lB l lD l lC I lD l lB l lA l 6 LOOP C I I I I I I I I I I I I I I LOOP B INLET l l l SA l l l l SB i l SB l l SP l l SA l l l LET 7

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l I I I I l l I I I I I I I I 90 W lD l l l lC l l l lC l l l lD l l 270 8 I I l i I I I I I I I l i I I I I I I SA i 1 SP l l SB l l SB l l l l SA l I l 9 I I I I I I I I I I I I I I I I lA l lB l lD l lC l lD l lB l lA i 10 l i I I I I I I I I I I I I I I I I SB 1 1 I I SP l l SB l l SP l l 11 I l l I I I I I I I I I I I I IC I IB i l i iB i iC i 1 12 I l I l I l i I I I I I I I SP l l SA l l ~* '

l l l 13 H-44 l l l l l l l l l l N-42 l lA 1 lD l lA l l 14 I I I I I I I I I i 15 LOO l l l l L PA ABSORBER CUTLET INLET MATERIAL l AG-IN-CD 0".

FUNCTION NUMBER OF CLUSTERS b CONTROL BANK D 8 CONTROL BATE C 8 CONTROL BANK B 6 CONTROL BANK A 8 SHUTDOWN BANK SB 8 SHUTDC'.04 BANK SA 8 SP (SPARE RCD LOCATIONS) 8 6

Section 2 BURNUP FOLLOW The burnup history for the North Anna Unit 2, Cycle 2 core is graphically depicted in Figure 2.1. The unit remained shut down from July 8,1982 until August 30, 1982 for the removal of thermal sleeves and the replacement of a main station service transformer. The North Anna 2, Cycle 2 core achieved a burnup of 8,436 MWD /MTU. As shown in Figure 2.2, the average load factor for Cycle 2 was 72% when referenced to rated thermal power (2775 MW(t)).

Radial (X-Y) burnup distribution maps show how the core burnup is shared among the various fuel assemblies, and thereby allow a detailed 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 2 operation is given. For comparison purposes, the design values are also given. Figu re 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 2 operation is also given. As can be seen from this figure, the accumulated assembly burnups were generally within 25% of the predicted values. In addition, deviation from quadrant symmetry in the core, as indicated by the burnup tilt factors, was no greater than 20.31%.

The burnup sharing on a batch basis is monitored to verify that the core is operating as designed and to enable accurate end-of-cycle batch burnup predictions to be made for use in reload fuel design studies.

Batch definitions are given in Figure 1.1. As seen in Figure 2.5, the 7

i batch burnup sharing for North Anna Unit 2, Cycle 2 followed design predictions closely with each batch deviating less than 3.2% from design.

Symmetric burnup in conjunction with agreement between actual and predicted assemblywise burnups and batch burnup sharing indicate that the Cycle 2 core did deplete as designed.

8

1 Figure 2.1 NORTH ANNA 2 - CYCLE 2 CORE BURNUP HISTORY 1 0 0 0 0 ,' ? !

9000 C 8000

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7000 #

B 6000 /

R N 5000-N 4000 #

0 3000 '

T 2000 1000 ,

0-0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 J J A S 0 N D J F M R H J U U U E C 0 E R E A P R U N L G P T V C N B R R Y N 8 8 8 8 8 8 8 8 8 8 8 8 8 l 2 2 2 2 2 2 2 3 3 3 3 3 3 TIME (MONTHS 1

--- CYCLE 2 DESIGN BURNUP WJNDOW - 7,000 TO 9.800 t1WD/MTU 9

l Figure 2.2 NORTH ANNA 2 - CYCLE 2 MONTHLY AVERAGE LOAD FACTOR 90 -

80

,0 6 0 --

50 40 -

30 2 0 --

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i Figure 2.3 NORTH ANNA 2 - CYCLE 2 .

ASSEMBLYWISE ACCUMULATED BURNUP MEASURED AND PREDICTED (1000 MWD /MTU)

R P M M L K J M a F D E C a A 1

1 6.091 7.451 6.051 1 MEAsuntD 1 1 I s.901 7.261 5.901 1 PREo1CTED l 2

l 6.161 a.531 9.661 24.991 9.701 a.521 6.181 I 5.961 a.441 9.5s1 24.941 9.5a1 a.441 5.94 3

1 6.521 9.241 25.261 2s.31I 23.361 25.111 25.051 9.201 6.711 3 1 6.361 9.051 25 171 25.431 23.471 25.431 25.171 9.csl 6.361 6

I 6.461 16.961 24.a71 1a.55] 23.501 29.251 23.431 la.4al 24.721 16.a61 6.631 4 1 6.361 16.691 24.a11 1a.6tl 23.654 20.3s8 23.651 la.621 24.821 16.691 6.361 5

I s.941 9.o2124.aol 23.60121.961 23.tal 23.5 1 23.571 21.741 23.661 24.901 9.311 6.201 5 1 5.961 9.051 24.e31 23.641 22 061 23.aol 23.791 23.801 22.061 23.641 14.a31 9.051 5.961 o

I a.431 25.091 la.32l 22. cal 24.371 1a.351 25.171 18.531 24.771 21.791 18.791 25.391 a.6el 6 I a.441 25.171 18.671 22.c31 24.411 14.aol 25.321 18.801 24.411 22.031 la.671 25.171 a.441 7

1 6.131 9.571 25.401 23.461 23.571 1a.281 23.221 17.931 23.201 18.501 23.211 23.401 25.441 9.721 6.058 7 1 5.901 9.5al 25.461 23.661 23.771 1a.811 13.561 la.411 23.561 la.all 23.771 23.661 25.461 9. sal 5.901 a

l 7.501 24.951 24.911 19.931 23.311 31.261 17.901 20.701 17.921 30.a11 23.541 20.1s 1 23.641 25.231 7.591 a l 7.261 24.t51 24.291 20.211 23.e41 31.461 la.361 20.961 la.361 30.921 as.aal 30.211 24.291 14.951 7.261 9

il 6.128 5.9c19.671 25.641 23.4al 23.121 1a.471 23.191 14.131 23.091 la.451 23.251 23.691 25.491 9.981 6.261

9. sal 25.46123.661 23.771 la.all 23.561 1a.41123.561 la.all 23.7'l 23.661 25.461 9. sal s.901 9

le I a.641 25.351 1a.541 21.661 24.451 1a.511 24.a61 18.611 24.511 21.721 18.641 25.181 a.sti lo I a.44l 25.171 14.671 22.e31 24.411 18.a01 25.321 1a.401 24.all 22.031 1a.671 25.171 a.441 11 1 6.201 9.331 24.911 23.431 21.9al 23.611 23.411 23.4a1 21.771 23.541 24.971 9.301 6.211 11 1 5.961 9.c51 24.a31 23.641 22.o61 23. sol 23.791 as.aol 22.061 23.641 24.e31 9.e51 5.961 lt 1 6.641 16.691 24.a61 la.55l 23.164 20.111 23.781 1a.591 24.991 17.001 6.661 12 I 6.341 16,691 24. sal la.6tl 23.651 20.351 23.651 18.621 24.a21 16.696 6.361 13 1 6.731 9.711 25.591 25.571 23.541 25.761 25.428 9.361 6.621 13 1 6.361 9.051 25.171 25.431 23.471 25.43l 25.171 9.051 6.361 14 1 6.411 9.091 9.931 25.201 9.751 a.728 6.261 14 1 5.961 a.441 9.5a1 24.941 9. sal s.441 s.961 85 l 6.411 7.571 6.031 15 1 5.901 7.261 5.901

. R P M M L K J. M G F E D C a A 11

Figure 2.4 NORTH ANNA 2 - CYCLE 2 ASSEMBLYWISE ACCUMULATED BURNUP COMPARISON OF MEASURED AND PREDICTED (1000 MWD /MTU) a P H M L K J H S P t 0 C 5 A 1

1 6.091 7.451 6.051 1 NtasJero l 1 1 3.181 a.6el 2.53I I n/P x 01FF I 2

1 6.161 s.531 9.66I 24.991 9.7sl a.stl 4.tal e i 3.351 1.071 s.all s.241 toast o.901 3.711 3

1 6.stl 9.t41 25.261 25.311 23.361 25.111 25.051 9.201 6.711 3 1 2.391 t.o61 0.331 -o.461 .o.441 1.231 .o.4al 1.611 s.351 4

1 6.461 16.961 24.a71 1s.ssi 23. sol to.tsi 23.631 18.4s1 24.721 16.661 6.631 4 1 1.451 1.6el s.211 .o.401 .o.641 .o.est .o.111 .o.731 .o.401 1.001 4.091 5

I s.9al 9.021 24.601 23.601 21.961 23.tal 23.521 23.571 21.741 23.661 24.901 9.311 6.201 s I o.3sl .o.361 o.iti .o.141 .o.431 .t.211 1.131 .o.9el .1.421 c.121 e. sol . ell 3.941 6

1 8.431 25.091 18.32l 22.o81 24.371 14.35 8 25.171 18.53l 24.771 21.791 la.791 25.391 a.6cl 6 1 .o.191 .o.3ci .1.sel o.tel .1.7a1 .t.3al .a.611 1.451 .o.141 1. cal s.661 o.a91 1.s91 7

1 6.131 9.571 25.401 23.461 23.571 1s.tal 23.ttl 17.93t 23.201 18.501 23.211 23.401 25.441 9.721 4.051 7 1 3.961.o.151.o.ast .o.e61.o.asi .t.asi .1.471.t.621 -1.541 1.6a1 3.371 1.o91.o. cal 1.411 2.601 8 1

7. sol 24.951 24.911 19.931 23.311 31.261 17.901 2o.701 17.921 30.611 23.541 20.101 23.641 25.231 7.591 a 1 3.411 .o.011 2.561 -1.371 .t.371 .o.641 .t.501 1.241 .t.391 .o.351 1.43 .o. set .t.6sl 1.111 4.421 9

............. ..... . ..... . ........ ...... ...............1 ............... ...........

l 6.121 9.471 25.641 23.4a1 23.321 18.471 23.191 la.131 23.091 la.4st 23.251 23.691 25.491 9.981 6.tel 9 1 3.691 c.951 c.721 .o.761 1.a91 1.e41 1.57I .1.551 .t.031 1.941 -2.191 c.121 c.131 4.o91 6.151 10 t a.641 25.351 1a.54l 21.668 24.451 18.511 24.861 1a.611 24.511 21.721 la. eel 25.1a1 a.821 10 1 2.271 0.741.o.661 1.671 1.451 1.551 1.atl .o.991 1.191 1.431.o.161 s.es 11

........ ........ ..... ..... . .. . .. ............. .... . t 4.441 1' 6.201 9.331 24.911 23.431 21.981 23.611 23.411 23.481 21.771 23.54l 24.971 9.301 6.211 11 l 4.001 3.091 0.351 -0.891 -o.361 -o.aol .1.611 1.331 1.301 .o.431 c. sal 2.701 4.211 la i 6.641 16.691 24.861 16.551 23.161 20.111 23.781 18.591 24.991 17.001 6.661 It 1 4.311 0.051 0.171 -0.391 -t.071 1.151 c.54l .o.181 o.711 1.e31 4.671 13 I 6.731 9.711 25.591 25.57I 23.541 25.761 25.421 9.361 6.621 .--.--.----.- 13 1 5.701 7.281 1.661 c.561. .c.331 1.291 c.991 3.411 4.091 l ARITHNETIC AVG I 14 IPCT c1rF = o.66l 1 6.411 9.o91 9.931 ts. col 9.758 a.7tl 6. 61 .-..-. -..-..... 14 1 7.511 7.631 3.541 1.ost 1.761 3.321 4.901 15 l STANDARD etV l l 6.411 7.571 6.031 l AVG A8s PCT I 15 1 = 1.66 l' I a.661 4.321 r.211 l DIFF = 1.7a I R P N N L K J H G F t D C B A Burnup Sharing

( 102 MWD /MTU ) Burnup Tilt Batch Cycle 1 Cycle 2 Total hv = -0.31 NE = -0.14 1A2 12.78 7.92 20.70 2A2 16.47 8.13 24.60 SW = 0.25 3A 11.06 9.44 20.50 4A ---

7.76 7.76 SE = 0.19 N1/3A3 ---

8.02 31.04 Core Average 8.44 12

Figure 2.5 NORTH ANNA 2 - CYCLE 2 SUB-BRTCH BURNUP SHARING SYMBOLIC POINTS ARE MERSURED DATR SUB-BRTCH : IR2 2R2 3R 4R 3R3 SYMBOL : 01RMOND SQURRE TRIANGLE STAR X 36000. .

32000, -

j r- .

/

28000 S -

Y-u d B '

/ \

/

B 24000 p '#

" m #"

T

> # s C : f f 20000 ' "

V 'V B

u R

7 2 r' // -

, jef 16000 #

P J'/T p , f

> f 12000 0

/

i_#- '

M -

U 8000' 7

- Y 7

4000' "

s Y

y 03 0 2000 4000 6000 B000 10000 CYCLE BURNUP (MHD/MTU) 13 ,

l Section 3 REACTIVITY DEPLETION FOLLOW The primary coolant critical boron concentration is monitored for the purposes of following core reactivity and to identify any anomalous reactivity behavior. The FOLLOW" computer code was used to normalize

" actual" critical boron concentration measurements to design conditions taking into consideration control rod position, xenon and samarium concentrations, moderator temperature, and power level. The normalized critical boron concentration versus burnup curve for the North Anna 2, Cycle 2 core is shown in Figure 3.1. It can be seen that the measured data typically compare to within 40 pom of the design prediction. This corresponds to less than 0.47% AK/K which is well within the 21% 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 2 core depleted as expected without any reactivity anomalies.

14

Figure 3.1 NORTH RNNA UNIT 2-CYCLE 2 CRJTJCAL BORON CONCENTRAT]CN VS BURNUP HFP-ARD X MERSURED PRE 0JCTED 1200 1000-C R

f i

! x\

R L 800

h\U B

x N X X_ , \

0 N %gh, 600 Nx

w 4

400 i

l W\ \

k\

\

200 g%,

N\

' *Xh N s 0,

0 2000 4000 6000 6000 10000 CYCLE BURNUP (MHD/HTV) 15

Section 4 POWER DISTRIBUTION FOLLOW 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 distributions are 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 2 is given in Table 4.1. Power distribution maps were generally taken at monthly intervals with additional maps taken as needed.

Radial (X-Y) core power distributions for a representative series of incore flux maps are given in Figures 4.1 through 4.3. Figure 4.1 shows a power distribution map that was taken early in cycle life. There are large differences ( up to 11.7%) between measured and predicted relative assembly powers and this map also evidenced a violation of the radial peaking factor, F-XY. The average percent difference between measured and predicted assembly powers for this map was 3.3%. The magnitude of the F-XY violation (compared to the RTP surveillance limit) was less than 3%. These differenco. are due to the asymmetric core loading and quadrant power tilt that existed for Cycle 2. Following an evaluation of the heat flux hot channel factor, Fg(Z), in accordance with Technical Specification 4.2.2.29, it was determined that sufficent margin existed in the design to a!!ow full power operation without restriction. This violation persisted until approximately 3,000 MWD /MTU. Figure 4.2 shows 16

a power distribution map that was taken near mid-cycle burnup. Note that the relative assembly powers are much closer to prediction with the measured assembly powers generally 5.6% from predicted, coincident with an average percent difference of 2.4%. Figure 4.3 shows a map that was taken at the end of Cycle 2 life. The measured relative assembly powers were generally within 4.6% and the average percent difference was equal to 2.0%. Similar improvement was apparent in the measured quadrant power tilt ratio values for Cycle 2. The full-power tilt ratio (approxim.itely 1.3%) that was reported in the Sta rtup Physics Test Report i rapidly diminished with burnup accumulation to a value of approximately 0.6% at the end of Cycle 2. The radial power distributions were ta ken under equilibrium operating conditions with the unit at approximately full power.

An important aspect of core power distribution follow is the monitoring of nuclear hot channel factors. Verification that these factors are within Technical Specifications ' limits ensu res that ljnear power density and critical heat flux limits wilt not be violated, thereby providing adequate thermal margins and maintaining f uel cladding integrity. The Cycle 2 Technical Specifications limit on the axially dependent heat flux hot channel factor, Fg(Z), began as 2.14 x K(Z), where K(Z) is the hot channel factor normalized operating envelope. Figure 4.4 is a plot of the K(Z) curve associated with the 2.14 Fg(Z) limit. On February 9,1983, which corresponds to a Cycle 2 burnup of 6,559 MWD /MTU, the Technical Specifications F9(Z) limit was changed to 2.20 (North Anna Unit 2 Technical Specifications Change No. 37'). Figure 4.5 is a plot of the K(Z) curve associated with the 2.20 Fg(Z) limit. The axially dependent heat flux hot channel factors, Fn(Z), for a representative set of flux maps are given in Figures 4.6 through 4.8. Throughout Cycle 2, the measured values of Fn(Z) were within the Technical Specifications limit. A summary of the maxim Jm values of axially-dependent heat flux hot channel 17

factors measured during Cycle 2 is given in Figure 4.9. Figure 4.10 shows the maximum values for the Heat Flux Hot Channel Factor measured during Cycle 2. As can be seen from the figure, there was an 18% margin to the limit at the beginning of the cycle, with the margin generally increasing throughout cycle operation.

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 critical heat flux (DNB) limit will not be violated. Additionally, the F-delta H limit ensures that the value of this parameter used in the LOCA-ECCS analysis is not exceeded during normal operation. The Cycle 2 limit on the enthalpy rise hot channel factor was set at 1.55 x (1+0.2(1-P)) x (1-RBP(BU)), where P is the fractional power level, and RBP(BU) is the rod bow penalty. A summary of the maximum values for the Enthalpy Rise Hot Channel Factor measured, during Cycle 2 is given in Figure 4.11. As can be seen from this figure, there was a 8% margin to the limit at the beginning of the cycle, with the ma rgin generally increasing throughout cycle operation.

The Technical Specifications require that target delta flux

values be determined periodically. The target delta flux is the delta flux which ~,

would occur at conditions of full power, all rods out, and equilibrium xenon. Therefore, 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. Operational delta flux limits are then Pt-Pb

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

2775 Pb = power in bottom of core (MW(t))

18

established about this target value. By maintaining the value of delta flux relatively constant, adverse axial power shapes due to xenon redistribution are avoided. The plot of the target delta flux versus burnup, given in Figure 4.12, shows the value of this parameter to have been approximately 6% at the beginning of Cycle 2. After approximately one-third of the cycle, delta flux values had shifted to 0% and then moved to -4% by the end of Cycle 2. This power shift can also be observed in the corresponding core average axial power- distribution for a representative series of maps given in Figures 4.13 through 4.15. In Map N2-2-16 (Figure 4.13), taken at approximately 1300 MWD /MTU, the axial power distribution had a shape peaked toward the top of the core with a peaking factor of 1.16. In Map N2-2-21 (Figu re 4.14), taken at approximately 4,000 MWD /MTU, the axial power distribution had shifted towa rd the bottom of the core with an axial peaking factor of 1.12.

Finally, in Map N2-2-30 (Figu re 4.15), taken at approximately 8,000 MWD /MTU, the axial peaking factor was 1.14. The history of F-Z during the cycle can be scen mo,re clearly in a plot of F-Z versus burnup given in Figure 4.16.

In conclusion, the North Anna 2, Cycle 2 core performed satisfactorily with power distribution analyses verifying that design predictions were accu rate and that the values of the Fg(Z) and F-delta H hot channel factors were within the limits of the Technical Specifications.

19

TABLE 4.1 s'

NORTH A W A UNIT 2 - CTCLE 2 SUP9 TART OF INCORE FLUX MAPS FOR ROUTINE OPERATION I l i l l 1 1 1 2 l l l l l l l l l BURNl l l F-OtT) HOT l F-DHINI HOT l CORE FtZ) I i l l l UP I IBA>GC l CHA W EL FACTOR 4l l 1 I CHNL. FACTOR I MAX l 31 GPTR l AXIAll HD.I I MAP l OATE I Mie/IPNRl D l l l IFIXT)l l HO. l l MTU lt%)lSTEPSI l lAXIAll l l l l OFF l 0F l

.l I l l l lAXIAll l MAX l l l SET ITHIMI I I i l_ I ilASSTlPINIPOIHil 1_._ l l F-QtTilASSTlPIHlF-DHINilPOINTl FtZil I l_ _I I I I l MAX lLOCl 'tXI IBLESl I I i 1 _.1 I I I I I I I I I l__ I I I l 10 I I I I I I I I Il 6-22-821 I 25111003I I 228 l Hitl I IMol ItI l 1.742I i K148 I P941 l 1.409 l 12 11.19711.60511.0131 SEl 5.291 45 I 1

l I I I I I I I '

Il lt (5); 6-23-821 t 3001 i 941 I

228 l tt141 1941 36 l 1.734 4 K1413941 1.433 l It 11.18911.64311.0141 SEl 4.471 40 l I I l l I I I I I I I I I i 13 I I I l l1 6-24-821 t 3071 i I991 222I l IK141 I 1941 I 37 l I1.714 l K141 i 1941 1.407 l It 11.16411.60011.0131 SEl 3.191 43 l l 14 I I I i 1 1 I I I l l1 6-25-821 l 32511001218 l I l K1411941 I I I 45 l 1.733 i l K14l MN1 1.411 1 13 11.14611.60211.0131 SEl 1.811 45 l

$ 1 1 l I I I I I I I I Il 16 tellI 9-14-821 I 12951981220 I I I l K1419941 I I I 37 l 1.737 I I l K141 1941 1.429 l It 11.16211.61811.0121 SEl 3.401 49 I I I I I I i l 17 1 I l' i lI 9-27-821 I 170011001 I I 223 I l I K141 I 1941 I

38 l I 1.745 I l K14l I

itil 1.432 l It 11.12911.61711.0101 SEl 1.411 50 l i 18 I I I I I I I I l 1110- 4-821 I 199511001 I I I 216 Ii K141 I 8941 46 1I 1.779 iI K141 t941 1.430 1 47 11.11011.60911.0091 SEI -0.771 50 l I I I I I l 19 1 1 I i 1 1 I110-15-821 I 242711001 I I I 222l i K141 l feel I

46 l 1.745 I I I K1417941 I

1.417 8 12 11.11111.60111.0091 SEl 0.061 49 l I tt I I I I I I I I 111- 5-821 322511001 224 l K141 1941 46 1 1.739 I K141 1941 1.416 l .47 11.10411.58511.0071 SEl -0.601 50 l HDTES HOT SPOT LOCATIONS ARE SPECIFIED BT GIVING ASSET 2LT LOCATIONS (E.G. H-8 IS THE CENTER-OF-CORE ASSEfBLT),

FOLLOWED BT THE PIN LOCATION (DENOTED BT THE "T" COORDINATE NITH THE SEVENTEEN ROWS OF FUEL RODS LETTERED A THROUGH R Ate THE "X" COORDINATE DESIGNATED IN A SIMILAR MAWER).

IN THE "Z" DIRECTION THE CORE IS DIVIDED INTO 61 AXIAL POINTS STARTING FROM THE TOP OF THE CORE.

1. F-QtTI INCLUDES A TOTAL IMCERTAINTT OF 1.05 X 1.03

2. F-DHtH) INCLUDES A MEASURENENT (MCERTAINTT OF 1.04

3. FtXTl INCLUDES A TOTAL UNCERTAINTT OF 1.05 X 1.03.

~

4. QPTR - QUADRANT POWER TILT RATIO.

5. MAP 11 NAS A QUARTER-CORE MAP TAKEN FOR INCORE/EXCORE DETECTOR CALIBRATION.

6. HAP 15 NAS A QUARTER-CORE HAP TAKEN FOR INCORE/EXCORE DETECTOR CALIBRATION.

o TABLE 4.1 (CONT.)

I l l BURHi l l F-QtT) HOT l F-OHIN) HOT l CORE FtZI l I I UP I l 4 I I I lBAlt( l CHAl#4EL FACTOR I CHNL. FACTOR I MAX l !

1 MAP l DATE I MWO/lPlatl D 1 GPTR l AXIALI NO.1 I l l NO. l l MTU ltXIlSTEPSI i IFIXTil I 0FF l OF l I lAXIAll l I l lAXIAll l MAX l l l SET ITHIMI '

l l 1 I l I i l_ ,_I IASSYlPINIPOINTl F-4tTilASSTlPINIF-DHINilPOINTl FtZil l MAX ILOCl IX) IBLESI 1 i 1 I I l _,,_ l l I I I i l i I I I I._.1I I l_I I I I 21 1 1 1 1 1 I i 1 I I I I I111-29-821 I 411011001 i 1 228 i1 K141 1 l t941 l

46 l 1.735 t i i Kiel I

t941 1.4021 4711.12111.55611.0061 SE1 -2.12150 I I I I I I I I I l 24 (73112-13-821459911001224 1 1 I I l I ll K14l i 7941 I 47 l 1.723 I I l K141 I

Ital 1.397 I 4711.11911.55111.006l SEl -2.20147 l I 25 I I I I I I l i i II 1-It-831556411001227 I I I I i K14l I HNI I 47I l 1.728I l K14l I

11NI I

1.382 1 53 11.14911.52311.0051 SWI -3.931 50 l I I I I I I I I l Il 17 (8ill 2-15-831675011001218 l l l l l K141 l l t941l 44 1 1.683 t i l K141 tell 1.369 l 53 11.14511.49611.006l SW1 -3.951 58 l

}

I I I I l i I I i I 30 89)l 3-17-831784411001218 l K141 1941 46 l 1.647 l K14l ital 1.355 1 53 11.14211.46411.0061 SWI -3.951 58 8

7. MAPS 22 afb 23 NERE IIUARTER-CORE MAPS TAKEN FOR INCORE/EXCORE DETECTDR CALIBRATION.

8. MAP 26 NAS A GUARTER-CORE MAP TAKEN TO DETERMINE AN APPROXIttATE VALUE OF INCORE AXIAL OFFSET.

9. MAPS 28 AIG 19 INERE IlUARTER-CORE MAPS TAKEN FOR INCORE/EXCORE DETECTOR CALIBRATION.

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1 Figure 4.4 HOT CHANNEL FACTOR NORMALIZED OPERATING ENVELOPE FOR A F9(Z) LIMIT OF 2.14 107 (6.0. 1.0)-

(10.98, 0.94)

O e

f 0.8-[

o -

w -

,N,_ :

M O.6-s :

tr :

O -

Z :

I 0.4 (12.0, 0.47)

Q v

M O.2-'

O.0-'. . .

BOTTOM TOP 25

l l

Figurc 4.5 HOT CHANNEL FACTOR NORMALIZED OPERATING ENVELOPE FOR A Fn(Z) LIMIT OF .2.20 7-

(6.0, 1.0) 1.0-

(10.92, 0.94) m v

N .

O :

1 0.8-LL :

O -

La N :

k s O.6 :

tt -

O :

Z :

I 0.4 (12.0, 0.45) m v

N :

sc :

0.2i t :

0.0- v- - - -- - . . . .

BOTTOM TOP ,

4 26

Figure 4.6 1 NORTH ANNA UNIT 2 - bYCLE 2 HEAT FLUX HOT CHANNEL FACTOR, F (Z)

N2 16 2.5 .*

2.0 .

.y .

zum unsun suamz suan um a a a a a a a e a 1.5 *-

a :

a a asum a a a su a m

=

3

- a NE

- 5 N

=

a 5 5

1.0 *

= N

. 5 e N

-u s S

S 0.5

h .'

O O

h o

O O

0.0

s.....s....n....

.... .... .... ....:.... .... ....:....a...:

61 50 40 30 20 10 1 BOTTOM AXIAL POSITION (NODES) TOP 27

l Figure 4.7 NORTH ANNA UNIT 2 - CYCLE 2 i

HEAT FLUX HOT CHANNEL FACTOR, F (Z)

N2-2-21 2.5 *

2.0

a sa

=

as as seus

. s as su

a m a a as sans 1.5

a as a am a

=

E a

a massa

. m su a E

a

= a

= a a

- E

. a 1.0 e.

.s e a

. m 0.5 e f .

0. 0 '

3.... 8... 8... 8....I... 3... 5... 8....B... 3... 3....B...I 61 50 40 30 20 10 1 BOTTOM AXIAL POSITION (NODES) TOP 28

Figure 4.8 NORTH ANNA UNIT 2 - CYCLE 2 HEAT FLUX HOT CHANNEL FACTOR, F (Z) l l N2-2-30 2.5 *.

2.0 *

x aux a un unmana an a assas 1.5 *. a

8 88888 a a a

. m a a usan

. a am er .R a

. R

. x

- a R 1.0 7 .a

. u

. x

. h

~

I up 0.0

s..... .... .... .... .... .... .... ... :.... .... .... ...:

61 50 40 30 20 10 1 BOTTOM AXIAL POSITION (NODES) TOP 29

. Figuro 4.9 NORTH ANNR UNIT 2 - CYCLE 2 NRXINUM HERT FLU.X HOT CHANNEL FACTOR, FQ s P VS RXJAL P00!T10N F0 m P LIMIT a MAXINUM FQ s P 2.4 .

2.2-l .

N

\

m 2.0 '

. ) ,

1.8 -

i t

3 4**"** 2*** ,

1 4*it* , **** u 1.6 . a6 4

. 4

,e J ~

\

.. . \

i .2

.\

1.0 x

0.8 N

0.6 0.4

\ .

0.2 .

0.0-61 55 50 45 Ab 35 30 25 2b 15 10 5 1

. AXJAL POSITION INODE)

@TTOM OF CORE TOP OF CORE 30

Figuro 4.10 NORTH RNNR UNIT 2 - CYCLE 2 l MAXIMUM HERT FLUX HDT CHANNEL FRCIOR, F-Q VS. BURNUP

- TECH SPEC LINJT X NERSURED VRLUE 2.4 .

2.3 .

R 2.2-X J :

H .

U 2.1 -

M H :

E 2 0-R T :

F 1.9 L '

U X

1.8 H

K ^

x x 1.1 C ^ X H

R .

a N 1.6-N E :

L .

1.5 F -

R :

'C T 1.4 0 -

R :

1.3 9

1.2-0 2000 4000 6000 6000 10000 CYCLE BURNUP (NWD/MTU) 31

Figura 4.11 NORTH RNNA UNji 2 - CYCLE 2 ENTHRLPY RJ SE NOT CH):NNEL FRCTOR. F-DHIN) VS. BURNUP

- TECH SPEC LlHJT X HERSURED VALUE 1.60, i.55:

E 1.50' N

T :

H .

R : .

L .1 . 4 5

P Y -

x ,

X x

.R .

x

! 1 40' ^

S .

E : -

H O 1.35 x T : * , .

' ^

Y g .

H R 1.30 N -

N E .

L :

1.25' F

R :

C s T :

0 1.20' "

R l l i . i S-:

e 1.10-D 2000 4000 6000 8000 10000 CYCLE BURNUP IMH0/MTU) 32

Figuro 4.12 l

NORTH RNNR UNIT 2 - CYCLE 2 l

l .*

TRRGET DELTR FLUX VS. BURNUP -

10 I

D' 6

A 4'

. 1 2'

0 : ,

A

-2' ;

-4 :. :. :.

-6~

-Bl

-10 ,

0 2000 4000 6000 8000 10000 -

. CYCLE BURNUP (NH0/MTUI 33

Figure 4.13 l

l I

NORTH ANNA UNIT 2 - CYCLE 2 CORE AVERAGE AXlAL POWER DISTRIBUTION N2-2-16 1.5 rz - 1.162

~

A. C. = 3.4 1.2.-

xx

=== n xx

=

ERXII n=x x x

=

NRRENN ENEN R

= N N R 22M N MN 2 xx N 3

=

2

- R 0.9e x R zu

. x

= X

'. 3

. x

0. 6. n N

- R

- N x

.x

( 0. 3 .

I

0. 0.

1.....I....I....t....t....I,....I....I....I... 3... 3...

61 3...I 50 40 30 20 10 1 BOTTOM AXIAL POSITION (NODES) TOP 34

_ _ _ _, _ _ _ _ - - - - - - - - - - - - " - - ~ - - - - - - ' ' - - - ' -__-_-_ __- _-_ _

l Figure 4.14 -

NORTH ANNA UNIT 2 - CYCLE 2

. CORE AVERAGE AXIAL POWER DISTRIBUTION N2-2 21 1.5 F2 = 1.121

A. O. - -2.1 1.2*.

zua mauxxx

. a x x xxxxxx xxxxxxx -xxx

- a m a a xxxxxxx x

. u 's m u

. a x x

. x x 0.9.

. x

. x x x

. m

. .x

. x 0.6*

.a

. x x

.x

0. 3 .

1 .

0.0 8.... 3... 3... 3... 3....I,... 3... 3....I....I....!... 3...I 61 50 40 30 20 10 1 BOTTOM AXIAL POSITION (N0 DES) TOP

Figure 4.15 NORTH ANNA UNIT 2 - CYCLE 2 CORE AVERAGE AXIAL POWER DISTRIBUTION N2-2-30

1. 5 .

FZ = 1.142

-A. O. = -3.9 s

1. 2 .*

aux xx a x xxx

- .x x x xxxxxx xxx x x xxx

- x = x xxxxxx xxxx x x x x m -

x A . a su M 0.9 +-

x *

x s

- x o -

x m .

0. 6 ' x 9.

-u x

0. 3 '

0. 0 .

t.....t... 3...

' 3,,,,3,,,,g,,,,g,,,,3,,,,g,,,,g,,,,g,,,,g ,,,g 61 50 40 30 20 10 1 BOTTOM AXIAL POSITION (NODES) TOP 36

Figuro 4.16 NORTH RNNR UNJT 2 - CYCLE 2 CORE RVERAGE RXJRL PERKING FACTOR. F-Z VS. BURNUP . .

1.4

-i I

q 1.3

1. 2- 3 a

A 3

A a

1.1 6 1.0-0 2000 4000 6000 8000 10000 CYCLE BURNUP (MWD /NTul 37

Section 5 PRIMARY COOLANT ACTIVITY FOLLOW 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 also important with respect to the offsite dose calculation values associated with accident analyses. Both I-131 and 1-133 can leak into the primary coolant system th rought a breach in the cladding. As indicated in the North Anna 2 Technical Specifications, the dose equivalent 1-131 concentration in the primary coolant was limited to 1.0 pCi/gm for normal steady state operation. Figure 5.1 shows the dose equivalent 1-131 activity level history for the North Anna 2, Cycle 2 core. The demineralizer flow rate averaged 75 gpm during power operation. The data shows that during Cycle 2, the core operated substantially below the 1.0 pCi/gm limit during steady state operation (the spike data is associated with power transients and unit s h utdown ) . Specifically, the average dose equivalent 1-131 concentration of 4.0 x 10-2 pCi/gm is equal to 40 of the Technical Specifications limit.

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 1-133 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 th rough the defect is on the order of days, the I-133 38

decays out leaving the 1-131 dominant in activity, thereby causing the ratio to be 0.5 or more. In the case of large leaks, uranium particles in the coolant, and " tramp" uranium *, where the diffusion mechanism is negligible, the I-131/l-133 ratio will generally be less than 0.1. Figu re ,

5.2 shows the 1-131/l-133 ratio data for the North Anna 2, Cycle 1 core.

These data generally indicate there were probably a few relatively large defects in the fuel used during Cycle 2.

]

" Tramp" uranium consists of small particles of uranium which adhere to the outside of the fuel during the manufacturing process.

39

. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _____________________________i

Figure 5.1 NORTH ANNA UNIT 2 -

CYCLE 2 DOSE EQUIVALENT I-131 vs. TIME TECHNICRL SPECIFICATIONS lit 11T s-D-

n-t- O

"- Ct

@ O O ()

y- O O e O 00 O e C '

3 0 e

n. O o- e O

@ gg @ O (9 C O

O O

O o

E O e

3- O O 1- O r- O O 7-0 4- 0 ,

l O

3

0 r-

~ "

M @ j r y - ., 100

.50 g

?

i JUL i

RUG i i i i i , ,

o!

SEP OCT 40 NOV DEC JRN FEB t1RR RPR 1982 1983 - - - - - - - - - - - - - - - - - - - -

Figuro 5.2 NORTH ANNA UNIT 2 -

CYCLE 2 I-131/I-133 ACTIVITY RATIO

vS. TIME :

i l

S O

O i 8

= ,

O 0

o 8 m

N O 3 0

- u O

O O o

O i3 0 0 ^

3 00 ' e g O o g a3 5

O cc O 8n _ n

@ - c ;

3 Pr ; P v - !

100

)

h5 e E

i i i i i i 0

i i i JUL AUG SEP OCT 41NOV DEC JAN FEB MAR APR IS02 1983

Section 6 CONCLUSIONS The North Anna 2, Cycle 2 core has completed creration. Throughout this cycle, all core performance indicators compared favorably with the design predictions and the core related Technical Specifications limits were met with significant ma rgin . The minor violations of the F-XY surveillance limits existed only at the beginning of the cycle. No significant abnormalities in reactivity or burnup accumulation were detected. In addition, the mechanical integrity of the fuel has not changed significantly throughout Cycle 2 as indicated by the radioiodine analysis.

(

i 42

Section 7 .

REFERENCES

1) B. D. Mann, " North Anna Unit 2, Cycle 2 Startup Physics Test -

Report," VEP-FRD-49, July,1982.

2) North Anna Power Station Unit 2 Technical Specifications, .

Sections 3/4.1 and 3/4.2. (;

3) T. K. Ross, "NEWTOTE Code", NFO-CCR-6 Vepco, March,1981.

4)

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

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

5) W. D. Leggett, 111 and L. D. Eisenhart, "INCORE Code,"

WCAP-7149, December,1967.

6) NRC Letter, Leon B. Engle to W. L. Stewart, Amendment Nos. 45 and 28 to Facility Operating License Nos. NPF-4 and NPF-7, January 27, 1983.

i

)

r J

l

}.

43

_ _ _ _ _ _ _ _ _ _ _ _ _ _

ML20069K367

Text

SUMMARY

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