Transient and equilibrium cycle characteristics on Paks uprated power units with 2nd generation of Gadolinia fuel

Imre NemesPaks NPP Ltd.

Hungary

General status of Paks Units

Non-standard cycles because of incident on Unit 2 2003

Recovery works has finished on Unit 2, unit in operation since 1 January

All units in normal order

108 % ( 1485 MWth, 500 MWe ) evaluated on Unit 4 in 2006 on Unit 1 in 2007

Power uprate in rest of units in next year (2008 )

Actually used fuel

Fixed FA-s : 3.82 wt%, 12.3 mm pitch

Followers : 3.82 wt%, 12.2 mm pitch, 2 mm shroud, Hf layer

90 ( 78+12 ) on 1375 MW units ( 4-year application of fixed assemblies

102 (90+12 ) on 1485 MW units ( poorer fuel cycle economy )

More economic fuel and cycle required

New fuel and cycle - Paks specific requirements

• Economic fuel cycle • High enough reserve in limiting parameters

– Uprated power on units – 1485 MWth, 500 MWe

– Much less reserve in local limits – Limits are untouched :

• Max. assembly power 6.58 – 0.37 MW • Max. pin power 57 - 5.7 kW • Max. linear heat rate 325 – 39 W/cm• Max. subchanel outlet temp. 326 – 7.5 C

– Highly welcome, if parameter is monoton decreasing during cycle

• Moderate increase of max. burnup desired

Gd-2n fuel (for Paks)

Geometry :

Gd-2 fuel

Avg. enr. 4.2 %

Shroud : 1.5 mm

for followers

as well

Some features of this fuel

1.07

1.12

1.17

1.22

1.27

0 5000 10000 15000

Burnup (MWd/tU)

K-i

nf

Gd-3-3.35%

Prof-3.8

1.02

1.03

1.04

1.05

1.06

1.07

1.08

1.09

1.1

0 5000 10000 15000 20000 25000 30000 35000 40000

Burnup (MWd/tU)

kk

-ma

xK-inf vs. burnup curves for Gd-2n and

3.82 % enriched fuel

Max. normalised pin power as a function of burnup for Gd-2n fuel

Method to provide 60 degree core symmetry

SECTOR 1

SECTOR 2

Assembly with odd orientation

Assembly with even orientation

Equilibrium cycle features / 1

Max. calculated burnups :

Assembly 48.9 / 49.5 MWd/kgU

Pin 52.7 MWd/kgU

Pellet 60.1 / 60.6 MWd/kgU

FUEL DESCRIPTION 1ST C. 2ND C. 3RD C. 4TH C. 5TH C.  Cycle 31  P 4.20 W 78 12.19 72 25.13 78 37.05 72 44.77 12 46.23Q 4.20 F 6 14.62 12 26.90 6 38.08 12 47.40 0 0.00Y 1.60 F 1 9.39 0 0.00 0 0.00 0 0.00 0 0.00 

Cycle 32   P 4.20 W 72 11.98 78 25.32 72 36.93 78 45.03 12 46.64Q 4.20 F 12 14.37 6 26.62 12 38.79 6 44.62 0 0.00Y 1.60 F 0 0.00 1 17.87 0 0.00 0 0.00 0 0.00  

Present and expected burnups

Assembly Pin Pellet

Previous limit (MWd/kgU) 49.00 55 64

Actual limit (MWd/kgU) 50.50 56.70 66.00

4.2 % Gd-fuel ,

transient and equilibrium cycles

Max. burnup (MWd/kgU) Assembly Pin Pellet

Calculated maximum 49.5 52.7 60.6

Engineering factor 2.90 5.1 7

Calculated + eng. Factor 52.40 57.80 67.60

Calculated + eng. Factor+reserve 54.00 60 70

Related to previous 1.10 1.09 1.09

Related to new limit 1.07 1.06 1.06

Equilibrium cycle features / 2

1

19.177

2

335.46

3

225.94

4

447.67

5

226.96

6

224.43

7

226.01

8

226.28

9

113.38

10

444.82

11

227.00

12

338.87

13

337.98

14

224.30

15

446.16

16

336.04

17

224.54

18

111.09

19

442.47

20

338.56

21

114.11

22

338.78

23

335.83

24

114.32

25

447.09

26

112.90

27

443.78

28

446.21

29

336.33

30

337.15

31

446.89

32

336.57

33

114.26

34

110.28

35

224.77

36

337.55

37

446.79

38

224.62

39

223.59

40

111.60

41

546.02

42

447.37

43

114.29

44

335.35

45

223.38

46

111.86

47

442.53

48

337.91

49

336.43

50

226.48

51

111.20

52

441.63

53

225.78

54

112.61

55

19.842

56

546.44

57

110.99

58

443.67

59

442.67

Time= 325.00 eff.day

Power= 1485.000 MW

Tin.= 267.000 C

Mod.Flow= 29816.0 t/h

Cb= -0.112 g/kg

Reactivity= 0.0002 %

h6 pos.= 237.000 cm

2 -Ass.pos.

3 -AssAge 38.9 -AssBu[MWd/kgU]

AssAge:

4.78: 5.05

4.51: 4.78

4.24: 4.51

3.97: 4.24

3.70: 3.97

3.43: 3.70

3.16: 3.43

2.88: 3.16

2.61: 2.88

2.34: 2.61

2.07: 2.34

1.80: 2.07

1.53: 1.80

1.26: 1.53

0.99: 1.26

Results of C-PORCA Calculations

Unit=4 Cycle=31

code info:/4/31/GD23/rudas/eoc/-/-

parameters: value: sec: ass.pos: pinpos: layer:

Ass.Pow-max[MW]: 5.510 1 24

Ass.Bu-max[MWd/kgU]: 48.86 1 4

PinPow-max[kW]: 46.18 1 9 16

PinBu-max[MWd/kgU]: 52.71 1 41 35

Tsub-max[C]: 316.5 1 9 43

Nlin-max[W/cm]: 157.7 1 25 71 35

Nlin-limit[W/cm]: 195.2 1 25 71 35

LocPinBu-max[MWd/kgU]: 60.10 1 41 35 16

1

217.48

2

336.30

3

226.40

4

338.42

5

337.98

6

223.39

7

225.97

8

336.51

9

113.10

10

443.53

11

227.18

12

447.21

13

225.99

14

224.50

15

447.25

16

336.10

17

224.46

18

110.96

19

441.91

20

338.78

21

226.17

22

336.54

23

337.43

24

114.06

25

337.97

26

112.80

27

443.29

28

227.36

29

335.58

30

337.27

31

446.32

32

447.21

33

113.98

34

110.15

35

227.45

36

335.11

37

445.79

38

223.94

39

224.18

40

111.37

41

546.54

42

446.67

43

114.14

44

446.15

45

224.80

46

111.70

47

443.71

48

338.54

49

336.37

50

114.06

51

111.39

52

443.80

53

223.30

54

112.89

55

110.19

56

546.75

57

111.00

58

443.66

59

442.47

Time= 325.00 eff.day

Power= 1485.000 MW

Tin.= 267.000 C

Mod.Flow= 29816.0 t/h

Cb= -0.136 g/kg

Reactivity= 0.0002 %

h6 pos.= 237.000 cm

2 -Ass.pos.

4 -AssAge 47.2 -AssBu[MWd/kgU]

AssAge:

4.78: 5.05

4.51: 4.78

4.24: 4.51

3.97: 4.24

3.70: 3.97

3.43: 3.70

3.16: 3.43

2.88: 3.16

2.61: 2.88

2.34: 2.61

2.07: 2.34

1.80: 2.07

1.53: 1.80

1.26: 1.53

0.99: 1.26

Results of C-PORCA Calculations

Unit=4 Cycle=32

code info:/4/32/GD23/rudas/eoc/-/-

parameters: value: sec: ass.pos: pinpos: layer:

Ass.Pow-max[MW]: 5.469 1 43

Ass.Bu-max[MWd/kgU]: 47.25 1 15

PinPow-max[kW]: 45.79 1 43 23

PinBu-max[MWd/kgU]: 52.65 1 56 71

Tsub-max[C]: 316.2 1 43 57

Nlin-max[W/cm]: 155.9 1 15 71 35

Nlin-limit[W/cm]: 192.8 1 15 71 35

LocPinBu-max[MWd/kgU]: 59.84 1 56 71 17

Boron letdown during eq.

cycle

Cycle Data Calculated by C-PORCA Unit=4 Cycle=31

cb_c [g/kg]

teff [FPD]3103002902802702602502402302202102001901801701601501401301201101009080706050403020100

cb_c

[g/

kg]

6

5

4

3

2

1

0

Cycle Data Calculated by C-PORCA Unit=4 Cycle=32

Cycle Lenght= 315.0 eff. day

cb_c [g/kg]

teff [FPD]3103002902802702602502402302202102001901801701601501401301201101009080706050403020100

cb_c

[g/

kg]

6

5

4

3

2

1

0

Max. pin power

during eq. cycle

Cycle Data Calculated by C-PORCA Unit=4 Cycle=31

Pin.p_max [kW]

teff [FPD]3103002902802702602502402302202102001901801701601501401301201101009080706050403020100

Pin.

p_m

ax [

kW]

48

47

46

Cycle Data Calculated by C-PORCA Unit=4 Cycle=32

Cycle Lenght= 315.0 eff. day

Pin.p_max [kW]

teff [FPD]3103002902802702602502402302202102001901801701601501401301201101009080706050403020100

Pin.

p_m

ax [

kW]

48

47

46

Max. linear heat rate during eq.

cycle

Cycle Data Calculated by C-PORCA Unit=4 Cycle=31

Lhr_max [W/cm] Lhr_lim [W/cm]

teff [FPD]3103002902802702602502402302202102001901801701601501401301201101009080706050403020100

Lhr

_lim

[W

/cm

]

285

280

275

270

265

260

255

250

245

240

235

230

225

220

215

210

205

200

Cycle Data Calculated by C-PORCA Unit=4 Cycle=32

Cycle Lenght= 315.0 eff. day

Lhr_max [W/cm] Lhr_lim [W/cm]

teff [FPD]3103002902802702602502402302202102001901801701601501401301201101009080706050403020100

Lhr

_lim

[W

/cm

]

260

255

250

245

240

235

230

225

220

215

210

Max. subchanel

outlet temp. during eq.

cycle

Cycle Data Calculated by C-PORCA Unit=4 Cycle=31

t_sub_max [C]

teff [FPD]3103002902802702602502402302202102001901801701601501401301201101009080706050403020100

t_su

b_m

ax [

C]

321

320

319

318

317

316

315

314

Cycle Data Calculated by C-PORCA Unit=4 Cycle=32

Cycle Lenght= 315.0 eff. day

t_sub_max [C]

teff [FPD]3103002902802702602502402302202102001901801701601501401301201101009080706050403020100

t_su

b_m

ax [

C]

321

320

319

318

317

316

315

314

(quasy) LTA program

• Goal : test fuel assembly outlet temperature ( measured vs. predicted )

• Finalise the model of outlet temperature measurement taking into accout coolant mixing features in assembly head

• Measure importance of follower containing Gd burnable poisson, compare to predicted

• Tool : 18 quasy LTA to Unit 4 of Paks , 12 fixed, 6 follower assemblies

Core arraengement

for LTA program

Gd fuel on positions :

18, 55 ( fixed )

33 (followers )

1

10980.879

2

10111.214

3

10111.081

4

10131.138

5

10111.167

6

10110.994

7

10130.980

8

10111.021

9

10111.197

10

10130.592

11

10111.222

12

10111.202

13

10111.039

14

10111.007

15

10111.128

16

10111.131

17

10111.124

18

10141.033

19

10110.353

20

10111.079

21

10111.194

22

10111.127

23

10111.112

24

10111.291

25

10111.008

26

10111.176

27

10110.747

28

10111.200

29

10111.007

30

10130.979

31

10110.966

32

10110.993

33

10151.255

34

10110.913

35

10111.164

36

10111.125

37

10110.988

38

10110.988

39

10111.285

40

10110.902

41

10110.343

42

10111.131

43

10111.297

44

10111.019

45

10111.320

46

10111.063

47

10110.399

48

10111.038

49

10111.035

50

10131.243

51

10111.038

52

10110.424

53

10111.297

54

10111.172

55

10140.914

56

10110.346

57

10111.004

58

10110.487

59

10110.327

Time= 0.00 eff.day

Power= 1485.000 MW

Tin.= 267.000 C

Mod.Flow= 29816.0 t/h

Cb= 7.283 g/kg

Reactivity= 0.0008 %

h6 pos.= 212.000 cm

2 -Ass.pos.

1011 -AssType 1.2 -Kq

AssType:

2.4 %-tk-Zr-1.22-F

3.82%-tn-Zr-1.23-W

3.82%-tk-Zr-1.22-F-Hf

4.2 %-tn-Zr-1.23-W-HU-Gd

4.2 %-tk-Zr-1.23-F-Hf-HU_Gd

Results of C-PORCA Calculations

Unit=4 Cycle=23

code info:/4/23/GD23/boros/0&0/-/-

parameters: value: sec: ass.pos: pinpos: layer:

Ass.Pow-max[MW]: 5.616 1 45

Ass.Bu-max[MWd/kgU]: 39.10 1 56

PinPow-max[kW]: 48.20 1 33 3

PinBu-max[MWd/kgU]: 41.50 1 56 71

Tsub-max[C]: 317.4 1 45 245

Nlin-max[W/cm]: 253.1 1 33 3 19

Nlin-limit[W/cm]: 286.0 1 33 3 19

LocPinBu-max[MWd/kgU]: 48.23 1 56 104 17Cycle 23 FUEL DESCRIPTION 1ST C. 2ND C. 3RD C. 4TH C. 5TH C.   K 3.82 W 78 12.76 90 25.79 90 37.85 42 40.90 0 0.00 M 3.82 F 6 14.20 12 26.73 12 33.48 0 0.00 0 0.00 P 4.20 W 12 10.73 0 0.00 0 0.00 0 0.00 0 0.00 Q 4.20 F 6 14.33 0 0.00 0 0.00 0 0.00 0 0.00 X 2.40 F 0 0.00 1 22.49 0 0.00 0 0.00 0 0.00

Conclusions

• Gd – 2n fuel is seemed to satisfy Paks specific requirements

• Equilibrium cycle is determined • Limiting parameters show relatively low

value and monoton decreasing feature• Max burnup is 6-7 % higher then the

present one

• Reload for application of quasy LTA-s is prepared

Calculation codes

• Methodical calculations and CCS libraries : HELIOS 1.9

• Core calculations : C-PORCA 6.2– Number of axial layers : 41 for old 42

for new fuel