NUREG-1754

A New Comparative Analysis of 

LWR Fuel Designs 

U.S. Nuclear Regulatory Commission 

Office of Nuclear Regulatory Research 

Washington, DC 20555-0001
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NUREG-1754 

A New Comparative Analysis of 

LWR Fuel Designs 

Manuscript Completed: November 2001 

Date Published: December 2001 

Prepared by 

G. M. O'Donnell, H. H. Scott, R. 0. Meyer 

Division of Systems Analysis and Regulatory Effectiveness 

Office of Nuclear Regulatory Research 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555-0001
A NEW COMPARATIVE ANALYSIS OF LWR FUEL DESIGNS

G. M. O'Donnell, H. H. Scott, and R. 0. Meyer 

ABSTRACT 

In 1980, NRC published a comparative analysis of LWR fuel designs, and that report served as 

a handy reference for typical design and operating parameters for all types of fuel then in 

operation in U.S. power reactors. During the past twenty years, significant changes have been 

made in fuel designs, burnups, and analytical computer codes. The present report is an update 

of the earlier report. Typical fuel design parameters are tabulated for almost all fuel types in 

current operation, from BWR 8x8 bundles to PWR 17x17 assemblies. Cross-section diagrams 

are given for BWR fuel bundles and PWR fuel assemblies. Calculated values are plotted for 

thirteen operating parameters including fuel centerline temperature, cladding O.D. temperature, 

gap conductance, rod internal gas pressure, and cladding hoop stress. The calculated values 

are plotted as a function of fuel burnup to 65 GWd/t for a variety of power histories, covering a 

range from low to high linear heat ratings, which are constant early in life but decline later in a 

realistic manner.

iii
Contents 

A bstract ................................................................. iii

Forew ord ............................... .. xvii

1. Introduction ........................................................ 1-1

2. Input Parameters ..................................... 

2.1. Pitch ........................................... 

2.2. Cladding Outer Diameter ........................... 

2-3. Cladding Thickness, Gap Thickness, and Pellet Diameter .. 

2-4. Dish Dimensions ................................. 

2-5. Plenum Length and Helium Fill Gas Pressure ........... 

2-6. Plenum Spring Dimensions ......................... 

2.7. Coolant Flow Rates ............................... 

2.8 Other Parameters .................................

....... 2-1 

....... 2-1 

....... 2-9 

....... 2-9 

...... 2-12 

...... 2-12 

...... 2-13 

...... 2-13 

...... 2-13

3. FRAPCON-3 ........................ 

3.1. MATPRO ....................... 

3.2. Fission Gas Release .............. 

3.3. Oxide Thickness .................

4. Axial Power Profile and Power Histories 

4.1. Axial Power Profile ............. 

4.2. Power Histories ................ 

5. Calculations for BWR 8X8 Fuel ...... 

6. Calculations for BWR 9X9 Fuel ...... 

7. Calculations for BWR 1OX10 Fuel .... 

8. Calculations for PWR 14X14 Fuel .... 

9. Calculations for PWR 15X15 Fuel .... 

10. Calculations for PWR 16X16 Fuel .... 

11. Calculations for PWR 17X17 Fuel 

12. References .......................

3-1 

3-1 

3-1 

3-1 

4-1 

4-1 

4-1

.................................. 5-1

6-1

. .............. . . ... ....... ... . 7-1 

. .................... .......... .. 8-1 

............ .. .. 9-1 ............... 

... .............................. 10-1 

................................. 11-1 

................................. 12-1

V

. . . . . . . . . . .Q 

. . . . . . . . . . .1
Figures

2-1. Components of typical fuel rods ........................................ 2-2 

2-2. Cross sections of fuel bundles that are interchangeable in all BWRs ............ 2-3 

2-3. Cross sections of fuel assembles for Westinghouse and C-E 14x1 4 plants ....... 2-4 

2-4. Cross sections of fuel assemblies for Westinghouse and B&W 15x1 5 plants ..... 2-5 

2-5. Cross sections of fuel assemblies for C-E 16xl 6 and 

W estinghouse 17x1 7 plants ........................................... 2-6 

2.6. Relationship between outside dimension of fuel bundle, 

fuel rod pitch and cladding diameter .................................... 2-1 

2-7. Cladding thickness as a function of cladding outer diameter determined 

from non-proprietary information ...................................... 2-10 

2-8. Gap thickness as a function of cladding outer diameter determined 

from non-proprietary information ...................................... 2-11 

4-1. Axial power profile used for code input ................................... 4-2 

4-2. Power histories used for BWR 8x8 fuel design ............................ 4-3 

4-3. Power histories used for BWR 9x9 fuel design ............................ 4-4 

4-4. Power histories used for BWR 10x10 fuel design ........................... 4-5 

4-5. Power histories used for PWR 14x14 fuel design ........................... 4-6 

4-6. Power histories used for PWR 15x15 fuel design ........................... 4-7 

4-7. Power histories used for PWR 16x16 fuel design ........................... 4-8 

4-8. Power histories used for PWR 17x17 fuel design ........................... 4-9 

5-1. Fuel temperatures and stored energy for a BWR 8x8 

fuel rod with initial peak power of 7 kW/ft ................................ 5-2 

5-2. Cladding temperatures and fuel surface temperature for a BWR 8x8 

fuel rod with initial peak power of 7 kW/ft ................................ 5-3 

5-3. Gap thickness and gap conductance for a BWR 8x8 fuel rod 

with initial peak power of 7kW/ft . ....................................... 5-4 

5-4. Fission gas release and rod internal gas pressure for a BWR 8x8 fuel rod 

with initial peak power of 7kW/ft . ....................................... 5-5 

5-5. Oxide thickness at three axial locations for a BWR 8x8 fuel rod 

with initial peak power of 7 kW/ft ........................................ 5-6 

5-6 Cladding hoop stress and hoop strain for a BWR 8x8 fuel rod 

with initial peak power of 7kW /ft . ....................................... 5-7 

5-7. Fuel temperatures and stored energy for a BWR 8x8 fuel rod 

with initial peak power of 9 kW /ft ........................................ 5-8 

5-8. Cladding temperatures and fuel surface temperature for a BWR 8x8 fuel rod 

with initial peak power of 9 kW /ft . ....................................... 5-9 

5-9. Gap thickness and gap conductance for a BWR 8x8 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 5-10 

5-10. Fission gas release and rod internal gas pressure for a BWR 8x8 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 5-11 

5-11. Oxide thickness at three axial locations for a BWR 8x8 fuel rod 

with initial peak power of 9 kW /ft ....................................... 5-12 

5-12. Cladding hoop stress and hoop strain for a BWR 8x8 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 5-13 

5-13. Fuel temperatures and stored energy for a BWR 8x8 fuel rod 

with initial peak power of 11 kW /ft ..................................... 5-14

vii
Figures (cont.)

5-14. Cladding temperatures and fuel surface temperature for a BWR 8x8 fuel rod 

with initial peak power of 11 kW /ft ..................................... 5-15 

5-15 Gap thickness and gap conductance for a BWR 8x8 fuel rod 

with initial peak power of 11 kW /ft ...................................... 5-16 

5-16. Fission gas release and rod internal gas pressure for a BWR 8x8 fuel rod 

with initial peak power of 11 kW/ft ...................................... 5-17 

5-17. Oxide thickness at three axial locations for a BWR 8x8 fuel rod 

with initial peak power of 11 kW /ft ...................................... 5-18 

5-18. Cladding hoop stress and hoop strain for a BWR 8x8 fuel rod 

with initial peak power of 11 kW /ft ...................................... 5-19 

5-19. Fuel temperatures and stored energy for a BWR 8x8 fuel rod 

with initial peak power of 13 kW/ft ...................................... 5-20 

5-20. Cladding temperatures and fuel surface temperature for a BWR 8x8 fuel rod 

with initial peak power of 13 kW/ft ...................................... 5-21 

5-21. Gap thickness and gap conductance for a BWR 8x8 fuel rod 

with initial peak power of 13 kW /ft ...................................... 5-22 

5-22. Fission gas release and rod internal gas pressure for a BWR 8x8 fuel rod 

with initial peak power of 13 kW /ft ...................................... 5-23 

5-23. Oxide thickness at three axial locations for a BWR 8x8 fuel rod 

with initial peak power of 13 kW/ft ...................................... 5-24 

5-24. Cladding hoop stress and hoop strain for a BWR 8x8 fuel rod 

with initial peak power of 13 kW /ft ...................................... 5-25 

6-1. Fuel temperatures and stored energy for a BWR 9x9fuel rod 

with initial peak power of 7 kW /ft . ....................................... 6-2 

6-2. Cladding temperatures and fuel surface temperature for a BWR 9x9 fuel rod 

with initial peak power of 7 kW/ft . ...................................... 6-3 

6-3. Gap thickness and gap conductance for a BWR 9x9 fuel rod 

with initial peak power of 7 kW /ft ........................................ 6-4 

6-4. Fission gas release and rod internal gas pressure for a BWR 9x9 fuel rod 

with initial peak power of 7 kW /ft . ....................................... 6-5 

6-5. Oxide thickness at three axial locations for a BWR 9x9 fuel rod 

with initial peak power of 7 kW /ft . ....................................... 6-6 

6-6. Cladding hoop stress and hoop strain for a BWR 9x9 fuel rod 

with initial peak power of 7 kW /ft . ....................................... 6-7 

6-7. Fuel temperatures and stored energy for a BWR 9x9fuel rod 

with initial peak power of 9 kW/ft..... ................................. 6-8 

6-8. Cladding temperatures and fuel surface temperature for a BWR 9x9 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 6-9 

6-9. Gap thickness and gap conductance for a BWR 9x9 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 6-10 

6-10. Fission gas release and rod internal gas pressure for a BWR 9x9 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 6-11 

6-11. Oxide thickness at three axial locations for a BWR 9x9 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 6-12 

6-12. Cladding hoop stress and hoop strain for a BWR 9x9 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 6-13

viii
Figures (cont.)

6-13. Fuel temperatures and stored energy for a BWR 9x9fuel rod 

with initial peak power of 11 kW /ft . ..................................... 6-14 

6-14. Cladding temperatures and fuel surface temperature for a BWR 9x9 fuel rod 

with initial peak power of 11 kW /ft ..................................... 6-15 

6-15. Gap thickness and gap conductance for a BWR 9x9 fuel rod 

with initial peak power of 11 kW /ft ...................................... 6-16 

6-16. Fission gas release and rod internal gas pressure for a BWR 9x9 fuel rod 

with initial peak power of 11 kW /ft ...................................... 6-17 

6-17. Oxide thickness at three axial locations for a BWR 9x9 fuel rod 

with initial peak power of 11 kW /ft ...................................... 6-18 

6-18. Cladding hoop stress and hoop strain for a BWR 9x9 fuel rod 

with initial peak power of 11 kW /ft ...................................... 6-19 

6-19. Fuel temperatures and stored energy for a BWR 9x9fuel rod 

with initial peak power of 12 kW/ft . ..................................... 6-20 

6-20. Cladding temperatures and fuel surface temperature for a BWR 9x9 fuel rod 

with initial peak power of 12 kW/ft ..................................... 6-21 

6-21. Gap thickness and gap conductance for a BWR 9x9 fuel rod 

with initial peak power of 12 kW /ft . ..................................... 6-22 

6-22. Fission gas release and rod internal gas pressure for a BWR 9x9 fuel rod 

with initial peak power of 12 kW /ft ...................................... 6-23 

6-23. Oxide thickness at three axial locations for a BWR 9x9 fuel rod 

with initial peak power of 12 kW /ft ...................................... 6-24 

6-24. Cladding hoop stress and hoop strain for a BWR 9x9 fuel rod 

with initial peak power of 12 kW /ft ...................................... 6-25 

7-1. Fuel temperatures and stored energy for a BWR 1 0x1 0 fuel rod 

with initial peak power of 5 kW /ft . ....................................... 7-2 

7-2. Cladding temperatures and fuel surface temperature for a BWR 1 0x1 0 fuel rod 

with initial peak power of 5 kW /ft . ....................................... 7-3 

7-3. Gap thickness and gap conductance for a BWR 10x1 0 fuel rod 

with initial peak power of 5 kW /ft . ....................................... 7-4 

7-4. Fission gas release and rod internal gas pressure for a BWR 1 0x1 0 fuel rod 

with initial peak power of 5 kW /ft . ....................................... 7-5 

7-5. Oxide thickness at three axial locations for a BWR 1 0x1 0 fuel rod 

with initial peak power of 5 kW /ft . ....................................... 7-6 

7-6. Cladding hoop stress and hoop strain for a BWR 10x10 fuel rod 

with initial peak power of 5 kW /ft . ....................................... 7-7 

7-7. Fuel temperatures and stored energy for a BWR 1 0x1 0 fuel rod 

with initial peak power of 7 kW /ft . ....................................... 7-8 

7-8. Cladding temperatures and fuel surface temperature for a BWR 10x10 fuel rod 

with initial peak power of 7 kW /ft . ...................................... 7-9 

7-9. Gap thickness and gap conductance for a BWR 10x10 fuel rod 

with initial peak power of 7 kW /ft . ...................................... 7-10 

7-10. Fission gas release and rod internal gas pressure for a BWR 10x10 fuel rod 

with initial peak power of 7 kW /ft . ...................................... 7-11 

7-11. Oxide thickness at three axial locations for a BWR 1 0x1 0 fuel rod 

with initial peak power of 7 kW /ft . ...................................... 7-12

ix
Figures (cont.)

7-12. Cladding hoop stress and hoop strain for a BWR 10x10 fuel rod 

with initial peak power of 7 kW /ft ....................................... 7-13 

7-13. Fuel temperatures and stored energy for a BWR 10x10 fuel rod 

with initial peak power of 9 kW /ft ....................................... 7-14 

7-14. Cladding temperatures and fuel surface temperature for a BWR 10x10 fuel rod 

with initial peak power of 9 kW/ft ...................................... 7-15 

7-15. Gap thickness and gap conductance for a BWR 10x10 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 7-16 7-16. Fission gas release and rod internal gas pressure for a BWR 1 0x1 0 fuel rod 

with initial peak power of 9 kW /ft ....................................... 7-17 7-17. Oxide thickness at three axial locations for a BWR 10x10 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 7-18 

7-18. Cladding hoop stress and hoop strain for a BWR 1 0x1 0 fuel rod 

with initial peak power of 9 kW /ft ....................................... 7-19 

7-19. Fuel temperatures and stored energy for a BWR 10x10 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 7-20 

7-20. Cladding temperatures and fuel surface temperature for a BWR 10x10 fuel rod 

with initial peak power of 11 kW /ft ..................................... 7-21 

7-21. Gap thickness and gap conductance for a BWR 1 0x1 0 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 7-22 

7-22. Fission gas release and rod internal gas pressure for a BWR 10x10 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 7-23 

7-23. Oxide thickness at three axial locations for a BWR 1 0x1 0 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 7-24 

7-24. Cladding hoop stress and hoop strain for a BWR 10x10 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 7-25 

8-1. Fuel temperatures and stored energy for a PWR 14x14 fuel rod 

with initial peak power of 9 kW /ft . ....................................... 8-2 

8-2. Cladding temperatures and fuel surface temperature for a PWR 14x14 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 8-3 

8-3. Gap thickness and gap conductance for a PWR 14x14 fuel rod 

with initial peak power of 9 kW /ft . ....................................... 8-4 

8-4. Fission gas release and rod internal gas pressure for a PWR 14x14 fuel rod with initial peak power of 9 kW /ft . ....................................... 8-5 

8-5. Oxide thickness at three axial locations for a PWR 14x14 fuel rod 

with initial peak power of 9 kW /ft . ....................................... 8-6 

8-6. Cladding hoop stress and hoop strain for a PWR 14x14 fuel rod 

with initial peak power of 9 kW /ft . ....................................... 8-7 

8-7. Fuel temperatures and stored energy for a PWR 14x1 4 fuel rod 

with initial peak power of 11 kW /ft . ...................................... 8-8 

8-8. Cladding temperatures and fuel surface temperature for a PWR 14x14 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 8-9 

8-9. Gap thickness and gap conductance for a PWR 14x14 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 8-10 

8-10. Fission gas release and rod internal gas pressure for a PWR 14x14 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 8-11

x
Figures (cont.)

8-11. Oxide thickness at three axial locations for a PWR 14x14 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 8-12 

8-12. Cladding hoop stress and hoop strain for a PWR 14x14 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 8-13 

8-13. Fuel temperatures and stored energy for a PWR 14x14 fuel rod 

with initial peak power of 13 kW /ft ...................................... 8-14 

8-14. Cladding temperatures and fuel surface temperature for a PWR 14x14 fuel rod 

with initial peak power of 13 kW /ft . .................................... 8-15 

8-15. Gap thickness and gap conductance for a PWR 14x1 4 fuel rod 

with initial peak power of 13 kW /ft . ..................................... 8-16 

8-16. Fission gas release and rod internal gas pressure for a PWR 14x14 fuel rod 

with initial peak power of 13 kW/ft.................................... 8-17 

8-17. Oxide thickness at three axial locations for a PWR 14x14 fuel rod 

with initial peak power of 13 kW /ft ...................................... 8-18 

8-18. Cladding hoop stress and hoop strain for a PWR 14x14 fuel rod 

with initial peak power of 13 kW /ft ...................................... 8-19 

8-19. Fuel temperatures and stored energy for a PWR 14x14 fuel rod 

with initial peak power of 15 kW /ft . ..................................... 8-20 

8-20. Cladding temperatures and fuel surface temperature for a PWR 14x14 fuel rod 

with initial peak power of 15 kW /ft . .................................... 8-21 

8-21. Gap thickness and gap conductance for a PWR 14x1 4 fuel rod 

with initial peak power of 15 kW/ft ...................................... 8-22 

8-22. Fission gas release and rod internal gas pressure for a PWR 14x1 4 fuel rod 

with initial peak power of 15 kW /ft . ..................................... 8-23 

8-23. Oxide thickness at three axial locations for a PWR 14x1 4 fuel rod 

with initial peak power of 15 kW /ft . ..................................... 8-24 

8-24. Cladding hoop stress and hoop strain for a PWR 14x14 fuel rod 

with initial peak power of 15 kW /ft ...................................... 8-25 

8-25. Fuel temperatures and stored energy for a PWR 14x1 4 fuel rod 

with initial peak power of 16 kW /ft ...................................... 8-26 

8-26. Cladding temperatures and fuel surface temperature for a PWR 14x14 fuel rod 

with initial peak power of 16 kW/ft ..................................... 8-27 

8-27. Gap thickness and gap conductance for a PWR 14x14 fuel rod 

with initial peak power of 16 kW /ft ...................................... 8-28 

8-28. Fission gas release and rod internal gas pressure for a PWR 14x14 fuel rod 

with initial peak power of 16 kW /ft ...................................... 8-29 

8-29. Oxide thickness at three axial locations for a PWR 14x1 4 fuel rod 

with initial peak power of 16 kW/ft ...................................... 8-30 

8-30. Cladding hoop stress and hoop strain for a PWR 14x14 fuel rod 

with initial peak power of 16 kW /ft . ..................................... 8-31 

9-1. Fuel temperatures and stored energy for a PWR 15x15 fuel rod 

with initial peak power of 9 kW /ft ........................................ 9-2 

9-2. Cladding temperatures and fuel surface temperature for a PWR 15x15 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 9-3 

9-3. Gap thickness and gap conductance for a PWR 15x15 fuel rod 

with initial peak power of 9 kW /ft . ....................................... 9-4

xi
Figures (cont.)

9-4. Fission gas release and rod internal gas pressure for a PWR 15x15 fuel rod 

with initial peak power of 9 kW/ft ......................... ............... 9-5 

9-5. Oxide thickness at three axial locations for a PWR 15x15 fuel rod 

with initial peak power of 9 kW /ft . ....................................... 9-6 

9-6. Cladding hoop stress and hoop strain for a PWR 15x15 fuel rod 

with initial peak power of 9 kW /ft . ....................................... 9-7 

9-7. Fuel temperatures and stored energy for a PWR 15x15 fuel rod 

with initial peak power of 11 kW /ft . ...................................... 9-8 

9-8. Cladding temperatures and fuel surface temperature for a PWR 15x15 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 9-9 

9-9. Gap thickness and gap conductance for a PWR 15x15 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 9-10 

9-10. Fission gas release and rod internal gas pressure for a PWR 15x15 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 9-11 

9-11. Oxide thickness at three axial locations for a PWR 15x15 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 9-12 

9-12. Cladding hoop stress and hoop strain for a PWR 15x15 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 9-13 

9-13. Fuel temperatures and stored energy for a PWR 15x1 5 fuel rod 

with initial peak power of 13 kW /ft ...................................... 9-14 

9-14. Cladding temperatures and fuel surface temperature for a PWR 15x15 fuel rod 

with initial peak power of 13 kW /ft ..................................... 9-15 

9-15. Gap thickness and gap conductance for a PWR 15x15 fuel rod 

with initial peak power of 13 kW /ft . ..................................... 9-16 

9-16. Fission gas release and rod internal gas pressure for a PWR 15x15 fuel rod 

with initial peak power of 13 kW /ft . ..................................... 9-17 

9-17. Oxide thickness at three axial locations for a PWR 15x15 fuel rod 

with initial peak power of 13 kW /ft . ..................................... 9-18 

9-18. Cladding hoop stress and hoop strain for a PWR 15x15 fuel rod 

with initial peak power of 13 kW /ft . ..................................... 9-19 

9-19. Fuel temperatures and stored energy for a PWR 15x1 5 fuel rod 

with initial peak power of 15 kW /ft . ..................................... 9-20 

9-20. Cladding temperatures and fuel surface temperature for a PWR 15x15 fuel rod 

with initial peak power of 15 kW /ft . .................................... 9-21 

9-21. Gap thickness and gap conductance for a PWR 15x1 5 fuel rod 

with initial peak power of 15 kW /ft . ..................................... 9-22 

9-22. Fission gas release and rod internal gas pressure for a PWR 15x15 fuel rod 

with initial peak power of 15 kW /ft . ..................................... 9-23 

9-23. Oxide thickness at three axial locations for a PWR 15x15 fuel rod 

with initial peak power of 15 kW /ft . ..................................... 9-24 

9-24. Cladding hoop stress and hoop strain for a PWR 15x15 fuel rod 

with initial peak power of 15 kW /ft . ..................................... 9-25 

10-1. Fuel temperatures and stored energy for a PWR 16x1 6 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 10-2 

10-2. Cladding temperatures and fuel surface temperature for a PWR 16x16 fuel rod 

with initial peak power of 9 kW /ft . ..................................... 10-3

xii
Figures (cont.)

10-3. Gap thickness and gap conductance for a PWR 16x1 6 fuel rod 

with initial peak power of 9 kW/ft ................................... 10-4 

10-4. Fission gas release and rod internal gas pressure for a PWR 16x16 fuel rod -5 

with initial peak power of 9 kW/ft .................................... 10 

10-5. Oxide thickness at three axial locations for a PWR 16x1 6 fuel rod 

with initial peak power of 9 kW /ft . ...................................... 10-6 

10-6. Cladding hoop stress and hoop strain for a PWR 16x1 6 fuel rod 

with initial peak power of 9 kW /ft ....................................... 10-7 

10-7. Fuel temperatures and stored energy for a PWR 16x1 6 fuel rod 

with initial peak power of 11 kW /ft . ..................................... 10-8 

10-8. Cladding temperatures and fuel surface temperature for a PWR 16x16 fuel rod 

with initial peak power of 11 kW /ft . .................................... 10-9 

10-9. Gap thickness and gap conductance for a PWR 16x1 6 fuel rod 

with initial peak power of 11 kW/ft ..................................... 10-10 

10-10. Fission gas release and rod internal gas pressure for a PWR 16x16 fuel rod 

with initial peak power of 11 kW /ft . .................................... 10-11 

10-11. Oxide thickness at three axial locations for a PWR 16x1 6 fuel rod 

with initial peak power of 11 kW /ft ..................................... 10-12 

10-12. Cladding hoop stress and hoop strain for a PWR 16x16 fuel rod 

with initial peak power of 11 kW /ft . .................................... 10-13 

10-13. Fuel temperatures and stored energy for a PWR 16x1 6 fuel rod 

with initial peak power of 13 kW/ft ..................................... 10-14 

10-14. Cladding temperatures and fuel surface temperature for a PWR 16x16 fuel rod 

with initial peak power of 13 kW/ft .................................... 10-15 

10-15. Gap thickness and gap conductance for a PWR 16x16 fuel rod 

with initial peak power of 13 kW /ft . .................................... 10-16 

10-16. Fission gas release and rod internal gas pressure for a PWR 16x16 fuel rod 

with initial peak power of 13 kW /ft ..................................... 10-17 

10-17. Oxide thickness at three axial locations for a PWR 1 6x1 6 fuel rod 

with initial peak power of 13 kW /ft ..................................... 10-18 

10-18. Cladding hoop stress and hoop strain for a PWR 16x16 fuel rod 

with initial peak power of 13 kW /ft ..................................... 10-19 

10-19. Fuel temperatures and stored energy for a PWR 1 6x1 6 fuel rod 

with initial peak power of 14 kW/ft ................................... 10-20 

10-20. Cladding temperatures and fuel surface temperature for a PWR 1"6x1 6 fuel rod 

with initial peak power of 14 kW /ft . ................................... 10-21 

10-21. Gap thickness and gap conductance for a PWR 16x16 fuel rod 

with initial peak power of 14 kW/ft ..................................... 10-22 

10-22. Fission gas release and rod internal gas pressure for a PWR 16x16 fuel rod 

with initial peak power of 14 kW /ft . .................................... 10-23 

10-23. Oxide thickness at three axial locations for a PWR 16x1 6 fuel rod 

with initial peak power of 14 kW /ft . .................................... 10-24 

10-24. Cladding hoop stress and hoop strain for a PWR 1 6x1 6 fuel rod 

with initial peak power of 14 kW /ft . .................................... 10-25

xiii
Figures (cont.)

11-1. Fuel temperatures and stored energy for a PWR 17x1 7 fuel rod 

with initial peak power of 7 kW /ft ....................................... 11-2 

11-2. Cladding temperatures and fuel surface temperature for a PWR 17x17 fuel rod 

with initial peak power of 7 kW /ft ...................................... 11-3 

11-3. Gap thickness and gap conductance for a PWR 17x1 7 fuel rod 

with initial peak power of 7 kW /ft . ...................................... 11-4 

11-4. Fission gas release and rod internal gas pressure for a PWR 17x1 7 fuel rod 

with initial peak power of 7 kW /ft ....................................... 11-5 

11-5. Oxide thickness at three axial locations for a PWR 17x17 fuel rod 

with initial peak power of 7 kW /ft . ...................................... 11-6 

11-6. Cladding hoop stress and hoop strain for a PWR 17x1 7 fuel rod 

with initial peak power of 7 kW/ft ....................................... 11-7 

11-7. Fuel temperatures and stored energy for a PWR 17x17 fuel rod 

with initial peak power of 9 kW /ft ....................................... 11-8 

11-8. Cladding temperatures and fuel surface temperature for a PWR 17x1 7 fuel rod 

with initial peak power of 9 kW /ft ...................................... 11-9 

11-9. Gap thickness and gap conductance for a PWR 17x17 fuel rod 

with initial peak power of 9 kW /ft . ..................................... 11-10 

11-10. Fission gas release and rod internal gas pressure for a PWR 17x1 7 fuel rod 

with initial peak power of 9 kW /ft . ..................................... 11-11 

11-11. Oxide thickness at three axial locations for a PWR 17x17 fuel rod 

with initial peak power of 9 kW /ft ...................................... 11-12 

11-12. Cladding hoop stress and hoop strain for a PWR 17x1 7 fuel rod 

with initial peak power of 9 kW /ft . ..................................... 11-13 

11-13. Fuel temperatures and stored energy for a PWR 17x17 fuel rod 

with initial peak power of 11 kW /ft . .................................... 11-14 

11-14. Cladding temperatures and fuel surface temperature for a PWR 17x17 fuel rod 

with initial peak power of 11 kW /ft . ................................... 11-15 

11-15. Gap thickness and gap conductance for a PWR 17x1 7 fuel rod 

with initial peak power of 11 kW /ft . .................................... 11-16 

11-16. Fission gas release and rod internal gas pressure for a PWR 17x1 7 fuel rod 

with initial peak power of 11 kW /ft . .................................... 11-17 

11-17. Oxide thickness at three axial locations for a PWR 1 7x1 7 fuel rod 

with initial peak power of 11 kW /ft . .................................... 11-18 

11-18. Cladding hoop stress and hoop strain for a PWR 17x17 fuel rod 

with initial peak power of 11 kW /ft . .................................... 11-19 

11-19. Fuel temperatures and stored energy for a PWR 17x17 fuel rod 

with initial peak power of 13 kW /ft . .................................... 11-20 

11-20. Cladding temperatures and fuel surface temperature for a PWR 17x17 fuel rod 

with initial peak power of 13 kW /ft . ................................... 11-21 

11-21. Gap thickness and gap conductance for a PWR 17x1 7 fuel rod 

with initial peak power of 13 kW /ft . .................................... 11-22 

11-22. Fission gas release and rod internal gas pressure for a PWR 17x17 fuel rod 

with initial peak power of 13 kW /ft . .................................... 11-23 

11-23. Oxide thickness at three axial locations for a PWR 17x17 fuel rod 

with initial peak power of 13 kW /ft . .................................... 11-24

xiv
11-24. Cladding hoop stress and hoop strain for a PWR 17x17 fuel rod 

with initial peak power of 13 kW/ft ..................................... 11-25 

Tables 

2-1. Typical Fuel Design Parameters used for Code Input ........................ 2-7 

2-2. Consequence of variations in fill pressure for PWR 17x17 

at 11 kW /ft with 10-in. plenum ........................................ 2-12 

2-3. Consequence of variations in plenum length for PWR 17x17 

at 11 kW /ft with 350 psi fill pressure .................................... 2-12 

2-4. Consequence of variations in fill pressure for BWR 9x9 

at 11 kW /ft with 10-in. plenum ........................................ 2-12 

2-5 Consequence of variations in plenum length for BWR 9x9 

at 11 kW/ft with 100 psi fill pressure .................................... 2-13

Tables (Cont.)

Al 

A2

Non-proprietary BWR Fuel Design Parameters ............................ A-1 

Non-Proprietary PWR Fuel Design Parameters ............................ A-2

xv
FOREWORD

The USNRC is conducting an integrated fuel program consisting of experiments and analyses. 

The goal of the program is to ensure safety as new fuel designs, materials, and higher burnup 

levels are proposed. Realistic experiments and analyses are intended to help maintain safety, 

improve agency efficiency and effectiveness, and reduce unnecessary regulatory burdens. 

This comparative analysis of LWR fuel designs is part of that overall effort. 

Jack E. Rosenthal, Chief 

Safety Margins & Systems Analysis Branch 

Office of Nuclear Regulatory Research

xvii
A NEW COMPARATIVE ANALYSIS OF LWR FUEL DESIGNS

G. M. O'Donnell, H. H. Scott, and R. 0. Meyer 

1. Introduction 

In 1980, D. L. Acey and J. C. Voglewede published a comparative analysis of LWR fuel 

des•gns, and that report served as a handy reference for typical design and operating 

parameters for all types of fuel then in operation in U.S. power reactors.1 During the past 

twenty years, significant changes have been made in fuel designs, burnups have increased 

more than fifty percent, and computer codes to analyze fuel behavior have been improved. The 

present report, therefore, is an update of the earlier report and provides current fuel design 

information and newly calculated fuel performance parameters out to 65 GWd/t, just beyond the 

present NRC fuel burnup limit of 62 GWd/t. 

Changes in fuel rod design that affect performance calculations include smaller cladding 

diameters in BWRs corresponding to the introduction of 9x9 and 10x10 fuel bundles. Increases 

in plenum length and fill gas pressure in both BWRs and PWRs also affect the calculations. 

Several new cladding types and alloys have been introduced, but they have a minimal effect on 

calculated performance parameters except for corrosion (discussed later). These changes 

have been made to accommodate somewhat higher power levels and large burnup increases 

from around 40 GWd/t in 1980 up to 62 GWd/t (average for the peak rod) in 2000. 

The earlier study was done with a March 1980 version (Revision 1) of the GAPCON-THERMAL

2 computer code, which was representative of a number of similar codes used at that time by 

the nuclear industry for fuel thermal performance analysis.2

' 3 The present study has been done 

with FRAPCON-3, which is an updated version of a code that combined the best features of 

GAPCON-THERMAL-2 and another code called FRAP-S. FRAPCON-3 has been validated out 

to 65 GWd/t burnup, and this peer-reviewed code is the code currently being used by NRC for 

auditing licensee's analyses and for research applications.4-6

1-1
2. INPUT PARAMETERS

Figure 2-1 identifies the components of typical fuel rods, and typical fuel assembly cross 

sections are shown in Figs. 2-2 and 2-5. The shrouded fuel arrays in BWRs are usually called 

bundles whereas the open-lattice PWR fuel arrays are called assemblies. 

Typical fuel design parameters that were used as code input are shown in Table 2-1 for all 

major fuel types currently in use in the U.S. These parameters are all based on non-proprietary values that are available in the literature.7-

9 Available non-proprietary fuel design parameters for 

a number of different fuel types are shown in Tables Al and A2 in the Appendix, and two things 

are readily apparent from these tables. First, no information is available on the BWR 1Wx0 fuel 

design except the number of fuel rods in a bundle. Second, even within a given fuel type (e.g., 

BWR 8x8), there are variations in some of the parameters between different vintages and 

manufacturers. The second observation shows that single fixed design parameters do not exist 

for each fuel type, but rather there are ranges of values. 

For our calculations, therefore, we sought typical values that were within these ranges although 

not necessarily corresponding to any specific design variant. Because design parameters were 

not available for the BWR 10x1 0 fuel type, we deduced suitable values of all the parameters 

needed for code input. The methods of selecting typical values for Table 2-1 are described 

below. 

2.1. Pitch 

The pitch was known for all of the fuel types except the 1 0x1 0. The value used was determined 

from calculations involving fuels of other array sizes. Since the 8x8 and 9x9 fuel bundles can 

be replaced with the 1 0x1 0 fuel bundles it is necessary for the outer dimensions of the bundle 

to be the same. The outer dimensions of the 8x8 and 9x9 fuel bundles were determined by 

multiplying their respective pitches by their respective array sizes minus one. One rod diameter 

was added to that value to determine the outside dimensions of the bundle. Figure 2-6 

Outside Dimension boo§50 

I Pitch I Di•m 

Fig. 2-6. Relationship between outside dimension 

of fuel bundle, fuel rod pitch and cladding diameter 

illustrates the relationship of the outside dimension of the bundle to the pitch and cladding 

diameter. The values found for the 8x8 and 9x9 were averaged together for the value used. 

Using the rod diameter for the 10x10 (how that was determined is explained later), it is possible 

to determine the pitch. The equations are shown below. 

8x8: (8-1) x 0.640 + 0.483 = 4.963

2-1
Cladding 

Gap

End Plug

Ej 

CL

Fig. 2-1. Components of typical fuel rods

2-2

Plenum Spring 

_ BWR Fuel Pellets 

with Flat Ends 

PWR Fuel Pellets 

with Dished Ends
1 2 3 4 5 6 7 8

8x8 with 2 small water rods. Other 8x8s 

have 1 large water rod (4 array locations)

1 2 3 4 5 6 7 8 9 10 0000000000 

0000000000 

0000000000 

0000000000 

000000000 

000000000 0000000000@ 

0000000000 

00000000q®

1 0x1 0 with 2 large water rods (8 array locations)

1 2 3 4 5 6 7 8 9 

000000000 

000000000 

000000000 

000000000 

000000000 

000000000 

000000000 

000000000 

Sooooooooo

9x9 with 2 small water rods. Other 9x9s 

have 2 large water rods (7 array locations)

*\",- Channel Box 0 

0

Fuel Rod 

Water Rod

368 bundles in smallest U.S. BWR 

800 bundles in largest U.S. BWR 

1 -4 in. (details not to scale)

-10 cm

Fig. 2-2. Cross sections of fuel bundles that are interchangeable in all BWRs

2-3

QOoooooo 00000000ý 

00000000 

00000000 

00000000 

00000000 

00000000 

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I I
1 2 3 4 5 6 7 8 9 10 11 12 13 14 

00000000000000 

00000000000000 

0000000~000000 

00000000000000 0000o0o00e0000 

00000000000000 

00000000000000 

00000000000000 

00000000000~000 

00000000000000 

00000000000000 

0000o000000000 

00000000000000 

00000000000000 

Westinghouse-type 1 4x1 4 

1 2 3 4 5 6 7 8 9 10 111213 14 

00000000000000 

00000000000000 

00 0000000 

00000000000000 

00000000000000 

000000(H)000000 

000000 ~000000 

00000000000000 

00000000000000 

00000000000000 

00000000000000

121 assemblies in 2-loop plant 

O Fuel Rod 

( Control Rod Guide Tube

© Instrumentation Tube

133 or 217 assemblies per plant 

1 -4 in. (details not to scale) 

-10 cm

Combustion Engineering-type 14x14 

Fig. 2-3. Cross sections of fuel assemblies for Westinghouse and C-E 14x14 plants 

2-4
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 

oooooooooooo000 

ooooooooooooooo 

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000OOOOOOO00O 

ooooooooooooooo 000000000000000 

O®OOOOOOOOOQOOO ooooo@®ooo®oooo 

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o®ooooooooooooo 

Westinghouse-type 1 5x1 5 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 

OOOOOGOOOOOOOO0 

ooo@ooo®oo®@ooo oooooooooo@oooo oooooooo@ooooo0 

ooooooooooooooo 

00000000000®000 

00000000000O00 

00000000000@000 

00000000000@000 

00000000000@000 

00000000000O0000 

0000000000O®0000 

O000000000000000 

000000000000000o 00o0oo0ooo0oooo 000o0000000o000 ooooooooo0o0o0o 00o000000o00o00 00o0o0o00000oo0 oo0ooooooo0oooo 000000000o00000

157 assemblies in 3-loop plant 

193 assemblies in 4-loop plant 

O Fuel Rod

0 

Q

Control Rod Guide Tube 

Instrumentation Tube

177 assemblies per plant 

-4 in. (details not to scale) I 

-10 cm

Babcock & Wilcox-type 15x15 

Fig. 2-4. Cross sections of fuel assemblies for Westinghouse and B&W 15x1 5 plants

2-5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 

0000000000000000 

0000000000000000 

0000000000000000 

1000(0000000C(N000 

000 00000 0QQQ 0000000000000000 

0000000000000000 

0000000000000 

0000000 0o000000 

0000000000000000 

0000000000000000 

000 000000 000 

0000000000000000 

0000000000000000 

0000000000000000 

Combustion Engineering-type 1 6x1 6 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 

00000000000000000 

00000000000000000 

00000000000000000 

00000000000000000 

00000000000000000 

000000Q00Q000O00 

00000000000000000 

00000000000000000 

00000000000000000 

00000000000000000 

00000000000000000 

00000000000000000 

00000000000000000 

00000000000000000 

00000000000000000 

00000000000000000

177 or 217 assemblies per plant 

241 assemblies in System-80

0 

Q

Fuel Rod 

Control Rod Guide Tube 

Instrumentation Tube

157 assemblies in 3-loop plant 

193 assemblies in 4-loop plant 

1 -4 in. (details not to scale) 

-10 cm

Westinghouse-type 17x1 7 

Fig. 2-5. Cross sections of fuel assemblies for C-E 16x16 and Westinghouse 17x17 plants

2-6
Table 2-1. Typical Fuel Design Parameters used for Code Input 

Fuel Type BWR BWR BWR PWR PWR PWR PWR 

8x8 9x9 10x10 14x14 15x15 16x16 17x17 

Pitch (mm, in.) 16.3 14.5 13.0 14.7 14.3 12.9 12.6 

0.640 0.572 0.510 0.580 0.563 0.506 0.498 

Cladding OD (mm, in.) 12.3 10.8 10.0 11.2 10.7 9.7 9.4 

0.483 0.424 0.395 0.440 0.423 0.382 0.370 

Cladding Thickness (mm, in.) 0.813 0.711 0.660 0.737 0.711 0.635 0.610 

0.032 0.028 0.026 0.029 0.028 0.025 0.024 

Gap Thickness (mm, in.) 0.112 0.097 0.089 0.102 0.097 0.086 0.084 

0.0044 0.0038 0.0035 0.0040 0.0038 0.0034 0.0033 

Fuel Pellet and Plenum Spring Diameter (mm, in.) 10.4 9.1 8.5 9.5 9.1 8.3 8.0 

0.410 0.360 0.336 0.374 0.359 0.325 0.315 

Pellet Length (mm, in.) 11.4 

0.45 

Dish Diameter (mm, in.) 0 4.75 4.52 4.14 4.01 

0 0.187 0.178 0.163 0.158 

Dish Depth (mm, in.) 0 0.287 

0 0.0113 

Plenum Length (mm, in.) 254 

10 

Turns in the Plenum Spring 37 33 31 34 33 30 28 

Plenum Spring Wire Diameter (mm,in.) 1.27 

0.05 

Helium Fill Gas Pressure (MPa, psi) 0.69 2.41 

100 350 

Active Fuel Length (m, in.) 3.66 

144

(cont'd)

2-7
Table 2-1. (cont'd) Typical Fuel Design Parameters used for Code Input 

Fuel Type BWR BWR BWR PWR PWR PWR PWR 

8x8 9x9 10xOA 14x14 15x15 16x16 17x17 

System Pressure (MPa, psi) 7.14 15.5 

1035 2250 

Coolant Inlet Temperature (0C, OF) 277 __ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _530 

Coolant Flow Rate (xl 06 kg/m 2-hr, x10 6 Ib/ft2-hr) 5.57 5.38 5.13 13.00 12.76 12.57 12.47 

1.14 1.10 1.05 2.65 2.61 2.57 2.55 

Enrichment (atom %) 4.0 4.5 

Pellet density (% TD) 95 

Temperature at which pellets were sintered ýC,°F) 1599 

2911 

Limit on pellet density increase (% TD) 0.9 

Limit on pellet swelling (%) 5 

Fuel surface roughness (mm, in.) 7.6x1 04 

3x10-5 

Cladding surface roughness (mm, in.) 5.1x10-4 

2X10-5 

Initial crud thickness (mm, in.) 0 

0

2-8

k
9x9: (9-1) x 0.572 + 0.424 = 5.000

(4.963 + 5.000)/2 = 4.982 

(4.982 - 0.395)/(10-1) = 0.510 

The value determined for the pitch of the 10x10 fuel bundle is thus 0.510 inches. The pitch size 

for other fuel types was taken directly from Tables Al and A2. 

2.2. Cladding Outer Diameter 

The cladding dimensions were known for all fuel types except the 10x10. Using known 

dimensions from bundles with other array sizes, an approximation was made for the 1 0x1 0 

cladding dimensions. It was assumed that the fuel volume of the bundles would be same since 

each bundle should supply the same amount of power. Knowing the outer diameter of the 8x8 

and 9x9 fuel rods and how many rods are in a typical bundle for each array size, it was possible 

to determine an approximate diameter for the 10x10 rods. Although the number of fuel rods in 

8x8, 9x9, and 10x10 fuel bundles vary, the numbers we had available at the time this estimate 

was made were 62, 79, and 92 fuel rods, respectively, in each of the bundle types. Equations 

for the 10x10 cladding outer diameter are shown below. All "rr's cancel out and are not shown. 

The length of all the rods are the same and also cancel out. 

8x8: 62 x (0.483)2 = 14.46 

9x9: 79 x (0.424)2 = 14.20 

(14.46 + 14.20)/2 = 14.33 

(14.33/92)Y2 = 0.395 

The outer diameter for the 10x10 fuel was assumed to be 0.395 inches. The cladding outer 

diameters for other fuel types were taken from known values listed in Tables Al and A2. 

2.3. Cladding Thickness, Gap Thickness, and Pellet Diameter 

We noticed that the Siemens (SNP) cladding and fuel pellet dimensions were identical for their 

BWR 9x9 fuel and their PWR 15x15 fuel. This suggested that there was just a single 

population of dimensional design parameters for BWRs and PWRs rather than two different 

populations and that we could look for trends with the combined set of dimensional values. 

Therefore, we decided to look at cladding thickness and gap thickness as a function of cladding 

OD and we found very good correlations. These plots are shown in Figs. 2-7 and 2-8. From 

these plots, we selected typical cladding thickness and gap thickness values for all of the fuel 

types including the BWR 10x10 for which there was no available information. Fuel pellet 

diameter could be determined once the gap thickness was known as well as the cladding outer 

diameter and thickness. The gap thickness and cladding thickness were subtracted from half 

of the cladding outer diameter to give the fuel pellet radius. This value was doubled for the fuel 

pellet diameter.

2-9
0.036 

0.034 

0.032 

0.030 

0.028 

0.026 

0.024 

0.022 

0.020 

0 0.45 0.50 0.55

Cladding OD (in.) 

Fig. 2-7. Cladding thickness as a function of cladding outer diameter 

determined from non-proprietary information

2-10

G0 

(0 

0) 

C 

C., 

"C 

I

0, 

C

y = 0.0696x - 0.0017

.30 0.35 0.40
0.0050

0.0045 

d 0.0040 

CL 

S0.0035 

00" 

S0.0030 

0.0025 

0.0020 

0.30 0.35 0.40 0.45 0.50 0.55 

Cladding OD (in.) 

Fig. 2-8. Gap thickness as a function of cladding outer diameter 

determine from non-proprietary information

2-11
2.4. Dish Dimensions

Dish dimensions were only added if the fuel was known to be dished. None of the BWR cases 

were run with dished pellets. The dimensions of the dish were based on the size of the fuel 

pellet. The diameter of the dish was assumed to be 50% of the diameter of the fuel pellet. The 

dish depth was assumed to be 2.5% of the height of the fuel pellet. This was based on 

dimensions used in the assessment section of the FRAPCON-3 manual. 

2.5. Plenum Length and Helium Fill Gas Pressure 

Plenum length and helium fill gas pressure are used as variables by fuel designers to tailor a 

particular fuel load to target burnups and power levels. Mid-range values were used as code 

input although large variationsare made in manufacturing, and these variations produce 

significant changes in end-of-life (EOL) fission gas release (FGR), EOL rod pressure, and 

plastic strain due to creep deformation (creep down). Tables 2-2 and 2-3 show typical code 

output changes for a PWR, and Tables 2-4 and 2-5 show typical changes in code output for a 

BWR. No EOL gap opening due to creep out was observed in any of the calculations.

Table 2-2. Consequence of variations in fill pressure for 

PWR 17x1 7 at 11 kW/ft with 10-in. plenum 

Fill Pressure EOL FGR EOL Pressure Max. Plastic Strain 

250 psi 8.3% 1553 psi -0.87% 

350 psi 7.3% 1848 psi -0.79% 

450 psi 6.9% 2231 psi -0.69% 

Table 2-3. Consequence of variations in plenum length for 

PWR 17xl 7 at 11 kW/ft with 350 psi fill pressure 

Plenum EOL FGR EOL Pressure Max. Plastic Strain 

6 in. 6.0% 2556 psi -0.70% 

10 in. 7.3% 1848 psi -0.79% 

14 in. 8.0% 1541 psi -0.81% 

Table 2-4. Consequence of variations in fill pressure for 

BWR 9x9 at 11 kW/ft with 10-in, plenum 

Fill Pressure EOL FGR EOL Pressure Max. Plastic Strain 

50 psi 8.4% 879 psi -0.44% 

100 psi 7.2% 945 psi -0.39% 

150 psi 6.3% 1041 psi -0.33%

2-12
Table 2-5. Consequence of variations in plenum

BWR 9x9 at 11 kW/ft with 100 ps•i fill pressure 

Plenum EOL FGR EOL Pressure Max. Plastic Strain 

6 in. 5.4% 1279 psi -0.35% 

10 in. 7.2% 945 psi -0.39% 

14 in. 8.7% 801 psi -0.40%

Trends of EOL pressure and maximum plastic strain are as expected. The higher the fill 

pressure or the shorter the plenum, the higher will be the EOL rod pressure. Notice that the 

nominal fill pressure in combination with the shortest plenum resulted in EOL fuel rod pressures 

that are larger than the reactor system pressure. Plastic strain shows the same kind of trend. 

The cases that result in higher pressures experience less plastic strain (smaller pressure 

differential), which is negative in all cases (creep down). 

The trends in fission gas release are not so easy to explain, however. In the Massih gas 

release model, the saturation concentration, which must be attained at a grain boundary prior to 

release, depends on the rod internal gas pressure (this is called Pe' in equation A.7, page A.5, 

of Ref. 4). The higher the gas pressure, the higher the saturation concentration, and vice 

versa. Thus, the larger plenum volume provides the lower gas pressure, which provides the 

lower saturation concentration, which permits earlier and larger FGR. What is observed is thus 

a natural consequence of the Massih model and is believed to be real. 

2.6. Plenum Spring Dimensions 

The plenum spring dimensions used for input are based on dimensions used in the assessment 

section of the FRAPCON-3 manual. Three cases were listed in the manual for fuel rods that 

are about 12 feet long. The spring volumes in these cases were compared to the volumes of 

the plenum. The percentages of plenum volume taken by these springs were 9.95%, 4.72%, 

and 3.40%. The volume percentage used in this report is 6% (the average of the three). The 

diameter of the spring is equal to the fuel pellet diameter for this report. A constant wire 

diameter was used for all fuel types. The number of turns in the spring was used to adjust the 

volume of the spring. 

2.7. Coolant Flow Rates 

The coolant flow rates used as input were based on flow rates used in the assessment section 

of the FRAPCON-3 manual. The coolant flow rate was adjusted to give a reasonable 

temperature rise through the core at all power levels examined. The temperature rise for each 

case changes since the flow rate is constant for all power levels. 

2.8. Other Parameters 

Nominal values were used for other parameters in Table 2-1 and were kept constant for each 

reactor type (BWR and PWR) to avoid additional variability in the output.

2-13

length for
3. FRAPCON-3

FRAPCON-3 analyzes the thermal and mechanical performance of fuel rods during steady

state operation. Changes in power are possible but must occur slowly enough to be considered 

steady-state. FRAPCON-3 can calculate many properties such as temperatures, strain, 

swelling, densification, and fission gas release. 

FRAPCON-3 has some limitations. Some of the major limitations that apply to this study are 

1. The code has not been assessed to predict cladding strains resulting from pellet

cladding interaction. 

2. Very limited assessment has been performed for fuel rods containing gadolinia. 

3. It is not possible to model axially changing gadolinia concentrations which are common 

in modern fuel. 

4. FRAPCON-3 only models standard Zircaloy cladding and not low-tin cladding. 

3.1. MATPRO 

FRAPCON-3 uses the MATPRO materials package to enable it to calculate materials properties 

to high burnup (65 GWd/t). MATPRO calculates properties such as the thermal conductivity and thermal expansion of the various materials in the fuel rod at high burnup. 

3.2. Fission Gas Release 

The fission gas release models available in FRAPCON-3 are the ANS-5.4 model and the 

Massih model. The model to be used is determined from the input. For all cases in this study, the Massih model was used. The Massih model is new to the FRAPCON series and was 

chosen because it is the best model for grain-boundary gas release. The Massih model is used 

unless the low temperature fission gas release model predicts more of a release. 

3.3. Oxide Thickness 

The cladding oxidation model used in FRAPCON-3 is not the model used in MATPRO. 

MATPRO predictions for oxide thickness were found to be different from measured oxide 

thicknesses by a factor of four or five. The model used in FRAPCON-3 to predict oxide 

thickness is based on the EPRI-developed ESCORE model. This ESCORE model has been 

assessed against in-reactor data with reasonably accurate results. 

The oxide thickness is strongly dependent on the temperature of the metal-oxide interface. 

This temperature in turn is strongly affected by changing the mass flux of the coolant which is 

defined in the input. Therefore for an accurate oxide thickness calculation it is important to 

define a reasonable coolant mass flux. Oxide thickness is also greatly affected by the initial 

crud thickness.

3-1
4. AXIAL POWER PROFILE AND POWER HISTORIES

4.1. Axial Power Profile 

The axial power shape changes during the lifetime of the fuel. In PWRs the power shape 

typically peaks at a lower axial position at beginning of life (BOL) and gradually changes to 

peak at higher axial positions at end of life (EOL). The result of this change is an average axial 

profile that is flat in the middle. In BWRs the peak is located in a lower axial position due to 

increased voiding at the top. Pellets enriched with gadolinia are used to flatten the axial profile 

for BWRs. Modeling the changing axial power profile on FRAPCON-3 is possible; however, for 

this report, a constant axial power profile was assumed. The constant profile was necessary to 

obtain understandable plots of the peak power node parameters. For example, plotting the 

centerline temperature of the peak power node with a constant axial power profile may show 

that the temperature rose during a burnup interval. If a changing axial profile were used, the 

peak power node may change from one step to the next. The temperature of the new peak 

node may not be as high as the temperature from the previous peak node and the plot of the 

centerline temperature would show that the temperature decreased. Plotting the peak power 

node would not show the true trend of the parameters if a changing axial power profile were 

used. The axial power profile used was derived from a burnup profile taken at EOL and is 

shown in Fig. 4-1. The same axial power profile was used for both PWRs and BWRs. 

4.2. Power Histories 

Each fuel design, except the 14x14, was given four power histories for analysis. The 14x14 

was given five power histories so that one power (9 kW/ft) would be common in the calculations 

for all the fuel designs. The power histories used are simple and within reason. All power 

histories begin at their peak power, which is held constant for awhile, and end at 65 GWd/t with 

a power of 5 kW/ft. Figures 4-2 through 4-8 show the power histories used for each fuel type. 

From the highest power to lowest power, the ramp down to 5 kW/ft begins at 20, 30, 40, and 50 

GWd/t, respectively. The power histories used were designed to provide a full range of realistic 

cases. The figures also show the time it took each case to burn up to 65 GWd/t.

4-1
1.2

"-0.8 

0 

CL 

NO.6 

E 

ZO. "0 z 0.4

0.2 

0 

0 2 4 6 8 10 12 

Height (ft) 

Fig. 4-1. Axial power profile used for code input

4-2
14

12 

A,,, A,,• A A A--A A A A6.9 years 

101 m• 5.8 years 

0

*" %- 5.1 years 47years 

S 8-

0 IL 6 

4 

2 

0

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 4-2. Power histories used for BWR 8x8 fuel design

4-3
14 

12 12 A A--AA A 5.3 years 

10 4.5 years •' 10 •4.0 years 

3. years 

0 

0- 6 

0 -4 

2

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 4-3. Power histories used for BWR Mx fuel design

4-4
12

10 s--(.3 years a A. A A A m 4.8 years 

.--- 4.0 years 

8 -- 3.6 years 

0~ 

a 4 

2 

0 " I I I 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 4-4. Power histories used for BWR 10x10 fuel design

4-5
18 

16 

14 

S12 

*•-10 I

0 

a. 8 

C 6 

4 

2 

0

0 10 20 30 40 50 60 

Average Burnup (GWd/t)

Fig. 4-5. Power histories used for PWR 14x14 fuel design

4-6

70
16

14 

A A A A A 4 .2 y e a rs 

12 3.7 years 

-M---m M3.4 years 

" -• _-,-• __-*--3.3 years 

10 

0~ 

4 

2 

0, 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 4-6. Power histories used for PWR 15x15 fuel design

4-7
10 20 30 40 50 60o 

Average Burnup (GWd/t) 

Fig. 4-7. Power histories used for PWR 16x16 fuel design

4-8

H

16

14 

12

10 

8

6

0 

0.

4 

2 

0

0

70
A A A A A A A A

E~ ~ m 0 0 mz m

14 

12 

10

I I

0 10 20 30 40 50 60

Average Burnup (GWd/t) 

Fig. 4-8. Power histories used for PWR 17x17 fuel design

4-9

---• 4.0 years 

-U- 3.4 years 

A 3.0 years 

--- 2.8 years

8 1

6

a. 

0 

CL 

0.

4 

2 

0

70

--• •= i=L

0 0 * * 4 * * 0 4 * * 0 - * $ * 0 0 0 0 * *

5

I

I
5. Calculations for BWR Mx8 Fuel 

In the following figures, calculated values for BWR 8x8 fuel are plotted as a function of burnup 

for the parameters listed below: 

Fuel centerline temperature 

Average fuel temperature 

Stored energy 

Fuel O.D. temperature 

Cladding I.D. temperature 

Cladding O.D. temperature 

Gap thickness 

Gap conductance 

Fission gas release 

Rod internal gas pressure 

Oxide thickness 

Cladding hoop stress 

Cladding hoop strain 

Several general observations can be made about the calculated results: 

* Within the first few GWd/t of burnup, a temperature peak is observed that is the 

result of fuel densification. 

Gap closure results in (a) the coming together of temperatures for fuel O.D. and 

cladding I.D. and (b) a sharp increase in gap conductance. The gap 

conductance increases again after a few time steps when the interaction 

between the pellet and cladding affects the contact conductance calculated for a 

closed gap. At this point there is also a large increase in stress, and the 

permanent strain changes directions. 

* Some of the fission gas is released in spurts according to the Massih 

model in FRAPCON-3. This effect is apparent in many of the figures. 

Shorter time steps would produce slightly different looking curves, but the 

trend of gas release and the end-of-life gas release would be about the 

same. 

0 The bumup enhancement of fission gas release is readily seen in the 

lower power cases, but it is obscured in the highest power cases by the 

magnitude of prior gas release. 

0 Rod internal gas pressure increases with the accumulation of released fission 

gas. In the higher power PWR cases, as the power drops off near the end 

of life, the reduction in the plenum temperature offsets the increasing 

moles of fission gas.

5-1
1000 

56 

900 

5 

50 

S800 

44 

CL.( 

E 700 

38 ,,=, 

60032 I•Centerline Temperature -. 11 3 

-*-Average Fuel Temperature 

-h Stored Energy 

500 

0 10 20 30 26 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-1. Fuel temperatures and stored energy for a BWR 

8x8 fuel rod with initial peak power of 7 kW/ft. 

5-2
500 

450 S• Fuel O.D. 

•- • Cladding I.D. o400 • Cladding O.D. 

400 

30. CLm 

E 35 0 -------------

300 A AAA AAI IAAA 

250 q 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-2. Cladding temperatures and fuel surface temperature for a 

BWR 8x8 fuel rod with initial peak power of 7 kW/ft.

5-3
60 150 

50 -.- Gap Thickness 125 

0 

40100 C 

0 E 

E 

~30- 75 0 

(D 

E20 50~ 

0 

10- 25 

0. 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-3. Gap thickness and gap conductance for a BWR 

8x8 fuel rod with initial peak power of 7 kW/ft.

5-4
4- 700 

3 525 

0. aO) cc. 

2 350 

1 175 

E3- Rod internal gas pressure 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-4. Fission gas release and rod internal gas pressure for a BWR 

8x8 fuel rod with initial peak power of 7 kW/ft.

5-5
40

35 

-.-- at 9.5 feet 

30 -a at 6.5 feet 

C S-4-at 2.5 feet 

o 25 

C.9 

U) 2 0 

- 15 

I-a 

10 

5 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-5. Oxide thickness at three axial locations for a BWR 

8x8 fuel rod with initial peak power of 7 kW/ft.

5-6
25000 0.3 

20000 -0.2 

15000 0.1 

CL*100000 

" 5000 0.1 

0 -0.2 

-5000 -0.3 

-10000 -0.4 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-6. Cladding hoop stress and hoop strain for a BWR 

8x8 fuel rod with initial peak power of 7 kW/ft.

5-7
1300 80 

1100 65 

0 0 

900 -0 

I700- 35 

_.- Centerline Temperature 

Average Fuel Temperature 

Stored Energy 

500 - 20 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-7. Fuel temperatures and stored energy for a BWR 

8x8 fuel rod with initial peak power of 9 kW/ft.

5-8

AA
500

450 

450. + Fu el O.D. 

--*Cladding I.D. 

0 400-- ladding 0.D.] 

~400 

- I 

300 -A-A 

a1..... 

25 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWdIt) 

Fig. 5-8. Cladding temperatures and fuel surface temperature for a 

BWR 8x8 fuel rod with initial peak power of 9 kW/ft.

5-9
50 150 

40 120 

•"= _.•Gap ThicknessI 0 ° 

- - Gap Conductance E 

_o30 90 

EC 

. 20 60 

0 

10 30 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-9. Gap thickness and gap conductance for a BWR 

8x8 fuel rod with initial peak power of 9 kW/ft.

5-10
A

900 

800 

700 

6 600 

OAU 

0( 500 

S1400 

t•3 -300 h 

Fission gas release 200 

-- Rod internal gas pressure 

100 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-10. Fission gas release and rod internal gas pressure for a BWR 

8x8 fuel rod with initial peak power of 9 kW/ft.

5-11
40 

35 

-- at 9.5 feet 

30 -- at 6.5 feet 

•',_.Eo• 2.5 25--=at feet 

LO 25 1

10 

U 0 U, 0 

(I, 

15

10 

5

0 rf 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-11. Oxide thickness at three axial locations for a BWR 

8x8 fuel rod with initial peak power of 9 kW/ft.

5-12
25000 0.2 

20000 -0.1 

150001, 0 

10000 

S5000 -0.2 m 

0 - -0.3 

-- Stress -5000 .-- S -0.4 

-10000,r -0.5 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-12. Cladding hoop stress and hoop strain for a BWR 

8x8 fuel rod with initial peak power of 9 kW/ft.

5-13
1500 72 

1300 64 

& 56~ 

0- 1100-5 

S900 48 

700 Centerline Temperature 40 

-u*-Average Fuel Temperature 

-& Stored Energy 

500 1 I 32 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-13. Fuel temperatures and stored energy for a BWR 

8x8 fuel rod with initial peak power of 11 kW/ft.

5-14
500

450 \ -uei u.u. 

-- Cladding I.D. 

-*- Cladding O.D. 

•400 0 

E 350 _ 

a300. 

250 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-14. Cladding temperatures and fuel surface temperature for a 

BWR 8x8 fuel rod with initial peak power of 11 kW/ft.

5-15
36- 90 

30 1 75 -- Gap Thickness 

g24 _60 S-B-Gap Conductance cm 01 

0 E 

18 45 

(cc 

12 30*" 

0 

6 15 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-15. Gap thickness and gap conductance for a BWR 

8x8 fuel rod with initial peak power of 11 kW/ft.

5-16

AA
12 1050 

10 900 

8 750 Cu 

. 6 600 

04 450 

_.- Fission Gas Release 

2 -Rod internal gas pressure 

2- 300 

0 150 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-16. Fission gas release and rod internal gas pressure for a BWR 

8x8 fuel rod with initial peak power of 11 kW/ft.

5-17
40 

35 

Co• 1 at 9.5 feet 

J 

30 - -- at 6.5 feet Owlr".. 

E 

20 

5 15 

10

5 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-17. Oxide thickness at three axial locations for a BWR 

8x8 fuel rod with initial peak power of 11 kW/ft.

5-18
U S.

15000 

10000

20 30 40 50 60

0.2

70

Average Burnup (GWd/t) 

Fig. 5-18. Cladding hoop stress and hoop strain for a BWR 

8x8 fuel rod with initial peak power of 11 kW/ft.

5-19

20000

-.- Stress 

"-+-ýojjj 11111o- StrainF

CL 

0. 5000

0 

-5000 

-10000

0 10

0.1 

0 

-0.1 E 

-0.2 

-0.3 

-0.4
1700

1500 77 

1300 67 

( 1100 57 

900 4 7 

700~ Centerline Temperatue3 

7Average Fuel Temperature 

S-Stored Energy 

500 1 1 27 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-19. Fuel Temperatures and stored energy for a BWR 

8x8 fuel rod with initial peak power of 13 kW/ft.

5-20

87
500

450 -.- Fuel O.D. Q 4-u-Cladding A I.D. 

S3400 =lC la ding O.D. 

1

300 -" " " " ....... . . . . . . . 

2 0..... 

CL E 350

300 

2501 

0 10 20 30 40 50 60 

Average Burnup (GWd/t) 

Fig. 5-20. Cladding temperatures and fuel surface temperature for a 

BWR 8x8 fuel rod with initial peak power of 13 kW/ft.

5-21

70
30 90 

25 -__75 

--- Gap Thickness 

2Gap Conductance 40 

C2- lo60 N0 

0 E 

~15 45 4 

Rig 

:E 10 30 V 

I- 0 

5 15 

0 . 1 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-21. Gap thickness and gap conductance for a BWR 

8x8 fuel rod with initial peak power of 13 kW/ft.

5-22
18 1300 

15 1100 

S12 -900 

U) ~0. 

2 9 700 'D 

S6 500 

-oFission gas release 

SRod internal gas pressureI 

3 300 

0 100 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-22. Fission gas release and rod internal gas pressure for a 

BWR 8x8 fuel rod with initial peak power of 13 kW/ft.

5-23
40 

35 

30 -- at 9.5 feet 

--=-at 6.5 feet 

C. 

E 

S20 

:=2o 

S15 

I

10 

5 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 5-23. Oxide thickness at three axial locations for a BWR 

8x8 fuel rod with initial peak power of 13 kW/ft.

5-24
0 

-5000 

-10000

0

20000 

15000 

10000

50

0.2

0.1 

0 

-0.1 

-0.2 

-0.3 

-0.4

70

Average Burnup (GWd/t)

Fig. 5-24. Cladding hoop stress and hoop strain for a BWR 

8x8 fuel rod with initial peak power of 13 kW/ft.

5-25

-- Stress 

-E- Strain

CL 

co

5000

10 20 30 40 60

. A _
6. Calculations for BWR 9x9 Fuel

In the following figures, calculated values for BWR 9x9 fuel are plotted as a function of burnup 

for the parameters listed below: 

Fuel centerline temperature 

Average fuel temperature 

Stored energy 

Fuel O.D. temperature 

Cladding I.D. temperature 

Cladding O.D. temperature 

Gap thickness 

Gap conductance 

Fission gas release 

Rod internal gas pressure 

Oxide thickness 

Cladding hoop stress 

Cladding hoop strain 

Several general observations can be made about the calculated results: 

Within the first few GWd/t of burnup, a temperature peak is observed that is the 

result of fuel densification. 

Gap closure results in (a) the coming together of temperatures for fuel O.D. and 

cladding I.D. and (b) a sharp increase in gap conductance. The gap 

conductance increases again after a few time steps when the interaction 

between the pellet and cladding affects the contact conductance calculated for a 

closed gap. At this point there-is also a large increase in stress, and the 

permanent strain changes directions. 

* Some of the fission gas is released in spurts according to the Massih 

model in FRAPCON-3. This effect is apparent in many of the figures. 

Shorter time steps would produce slightly different looking curves, but the 

trend of gas release and the end-of-life gas release would be about the 

same. 

0 The bumup enhancement of fission gas release is readily seen in the 

lower power cases, but it is obscured in the highest power cases by the 

magnitude of prior gas release. 

0 Rod internal gas pressure increases with the accumulation of released fission 

gas. In the higher power PWR cases, as the power drops off near the end of 

life, the reduction in the plenum temperature offsets the increasing moles of 

fission gas.

6-1
1000 56 

900- 50 

0 0 

800 -44

CLu 

E 700 38 

600 Centerline Temperature 32 

-uAverage Fuel Temperature 

S-&-Stored Energy 500 ..... 26 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-1. Fuel temperatures and stored energy for a BWR 

9x9 fuel rod with initial peak power of 7 kW/ft.

6-2
500

450 

450 -o-Fuel 0. D. 

--*-Cladding I.D. 

o• I --k-Cladding O.D. 

0 400 

E 350 o Ao .:.....

250 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-2. Cladding temperatures and fuel surface temperature for a 

BWR 9x9 fuel rod with initial peak power of 7 kW/ft.

6-3
50 150 

---- Gap Thickness 

--- Gap Conductance 

40 120 

0 

0 E• 22 

o30 90 

r-, 20 60 ' 

0 

.o_ 

I

0 

10 30 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-3. Gap thickness and gap conductance for a BWR 

9x9 fuel rod with initial peak power of 7 kW/ft. 

6-4

F
4 700 

3 525 

0 . 

02 350 

1 

175 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-4. Fission gas release and rod internal gas pressure for a BWR 

9x9 fuel rod with initial peak power of 7 kW/ft.

6-5
10 20 30 40 50 60

Average Burnup (GWd/t)

Fig. 6-5. Oxide 

9x9 fuel

thickness at three axial locations for a BWR 

rod with initial peak power of 7 kW/ft.

6-6

35 

30 

25 

20 

15 

10

U, 

0 

I

0 

Co 

Co 

C 

C) 

"C 

I5 

0

0 70
0.1

15000 0 

10000 -0.1 

0. 

S 5000 -0.2 .E 

0 -0.3 

-5000 -0.4 

".- Stress 

-10000 20 , , Strain -0.5 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-6. Cladding hoop stress and hoop strain for a BWR 

9xW fuel rod with initial peak power of 7 kW/ft.

6-7

20000
1300

1100 60 

0 

S 900 50> 

C0) 

E C 

700-- 40 

-a-Stored Energy 

500 1 1 , 30 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-7. Fuel temperatures and stored energy for a BWR 

9x9 fuel rod with initial peak power of 9 kW/ft.

6-8

70
500

450 

--- Fuel O.D. 

-uCladding I.D. 

040• -Cladding O.D. 

CL 

250 1.. 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-8. Cladding temperatures and fuel surface temperature for a 

BWR 9x9 fuel rod with initial peak power of 9 kW/ft.

6-9
40 150 

32 120 

•" *-Gap Thickness of, Cm) 

0 •24 ~ Gap Conductance E o90 

5• 16 -60 

E:C 

0 

8 -30 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-9. Gap thickness and gap conductance for a BWR 

Mx fuel rod with initial peak power of 9 kW/ft.

6-10
900 

800 

700 

6600 _ 

U,500 

400 

03 300 C. 

Fission gas release 200 

-E3- Rod internal gas pressure 100 10 

0 10 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-10. Fission gas release and rod internal gas pressure for a BWR 

9x9 fuel rod with initial peak power of 9 kW/ft.

6-11
35

30 

-4at 9.5 feet 

25 -at 6.5 feet 

- A at2.5feet 

0 

*20 

~15 

10 

5 

0 PU 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-11. Oxide thickness at three axial locations for a BWR 

9x9 fuel rod with initial peak power of 9 kW/ft.

6-12
20000 

15000

60

0.1

0 

-0.1

-0.2

01 

Cl"

-- Stress 

-B- Strain

70

Average Burnup (GWd/t)

Fig. 6-12. Cladding hoop stress and hoop strain for a BWR 

9x9 fuel rod with initial peak power of 9 kW/ft.

6-13

I W

-0.3 

-0.4 

-0.5

10000

U, 

L_ 

co

5000

0 

-5000 

-10000

0 10 20 30 40 50
10 20 30 40 50 60

Average Burnup (GWd/t) 

Fig. 6-13. Fuel temperatures and stored energy for a BWR 

9x9 fuel rod with initial peak power of 11 kW/ft.

6-14

1500 

1300 

0 1100 

S 900 1

700 

500

0

C._enterline Temperature Average Fuel Temperature 

SStored Energy

70

72 

64 

56~ 

48 C 

40 

32
500

450 -4--Fuel O.D. 

-u-Cladding I.D. 

-- Cladding O.D. 

0 400 

I.

.......... 040 

0. 

E 350 

300 - .. 

250 I 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-14. Cladding temperatures and fuel surface temperature for a 

BWR 9x9 fuel rod with initial peak power of 11 kW/ft.

6-15
30 120 

25 __ _ _ _ _ _ _ _100 

S-Gap Thickness 

a Gap Conductance 80 

S80 e4 20- E 

0 20 

u) 15 60 

0 ,0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-15. Gap thickness and gap conductance for a BWR 

9x9 fuel rod with initial peak power of 11 kW/ft.

6-16
10 

8 

S4 

2 

0

0 10 20 30 40 50 60

Average Burnup (GWd/t)

Fig. 6-16. Fission gas release and rod internal gas pressure for a BWR 

9x9 fuel rod with initial peak power of 11 kW/ft.

6-17

1150 

950 

750 "rn 

550 

0,. 

350 

150

70
35

30 

-*-at 9.5 feet _ 25 --- at 6.5 feet 

C A- at 2.5 feet 0 

L

*020 1 

C'D15 

1>0 

5 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-17. Oxide thickness at three axial locations for a BWR 

9x9 fuel rod with initial peak power of 11 kW/ft.

6-18
20000 0.1 

15000-1 0 

10000- -0.1 

%.w 

" 5000 -0.2 

0 .-0.3 

-5000 -0.4 

-10000 -0.5 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-18. Cladding hoop stress and hoop strain for a BWR 

9x9 fuel rod with initial peak power of 11 kW/ft.

6-19
1500 72

N

I - (nforimna '- MomnorrnitI rp

1300 

0 1100 

1L 

E 900 

12 

700 

500

10 20 30 40 50 60

Average Burnup (GWd/t) 

Fig. 6-19. Fuel Temperatures and stored energy for a BWR 

9x9 fuel rod with initial peak power of 12 kW/ft.

6-20

--- Average Fuel Temperature 

S-Stored Energy

0 70

'A

1500 72

64 

56~ 

48 

(U 

40 

32
500

450 ---Fuel O.D. 

S•k -*--Cladding I.D. 

0 400 

E:: 350 =_ M, _ _ _. _ 

300 ...... A A A A A; 

25 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-20. Cladding temperatures and fuel surface temperature for a 

BWR 9x9 fuel rod with initial peak power of 12 kW/ft.

6-21
10 20 30 40 50 60

Average Burnup (GWd/t) 

Fig. 6-21. Gap thickness and gap conductance for a BWR 

9x9 fuel rod with initial peak power of 12 kW/ft.

6-22

25 

20

0 

1.. 

Um 

2-

15 

10

5 

0

0

120 

100

-- Gap Thickness 

---Gap Conductance

70

0 

80 c" 

E 

60 

40~ 

0 

20 

0
12

10

8 

6 

4

2 

0

0 10 20 30 40 50 60

Average Burnup (GWd/t) 

Fig. 6-22. Fission gas release and rod internal gas pressure for a BWR 

9x9 fuel rod with initial peak power of 12 kW/ft.

6-23

0IX 

CU

Fission gas release 

Rod internal gas pressure

70

1100 

950 

800 

CL 0,. 

650 -• 

a. 

500 

350 

200
35

30 

25 at 9.5 feet 

25 -. at 6.5 feet 

C 

2 -&-at 2.5 feet 

.20 

S15 

110 

5 

0II I 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 6-23. Oxide thickness at three axial locations for a BWR 

9x9 fuel rod with initial peak power of 12 kW/ft.

6-24
I U.

15000 

10000

20 30 40 50 60

0.15

70

Average Burnup (GWd/t) 

Fig. 6-24. Cladding hoop stress and hoop strain for a BWR 

9x9 fuel rod with initial peak power of 12 kW/ft.

6-25

20000

SStress 

-- Strain

CL 

a

Co. 5000

0 

-5000 

-10000

0 10

0.05 

-0.05 

-0.15 .E 

(I) 

-0.25 

-0.35 

-0.45
7. Calculations for BWR 10x10 Fuel

In the following figures, calculated values for BWR 1oxl 0 fuel are plotted as a function of 

burnup for the parameters listed below: 

Fuel centerline temperature 

Average fuel temperature 

Stored energy 

Fuel O.D. temperature 

Cladding I.D. temperature 

Cladding O.D. temperature 

Gap thickness 

Gap conductance 

Fission gas release 

Rod internal gas pressure 

Oxide thickness 

Cladding hoop stress 

Cladding hoop strain 

Several general observations can be made about the calculated results: 

* Within the first few GWd/t of burnup, a temperature peak is observed that is the 

result of fuel densification. 

0 Gap closure results in (a) the coming together of temperatures for fuel O.D. and 

cladding I.D. and (b) a sharp increase in gap conductance. The gap 

conductance increases again after a few time steps when the interaction 

between the pellet and cladding affects the contact conductance calculated for a 

closed gap. At this point there is also a large increase in stress, and the 

permanent strain changes directions. 

0 Some of the fission gas is released in spurts according to the Massih 

model in FRAPCON-3. This effect is apparent in many of the figures. 

Shorter time steps would produce slightly different looking curves, but the 

trend of gas release and the end-of-life gas release would be about the 

same. 

0 The bumup enhancement of fission gas release is readily seen in the 

lower power cases, but it is obscured in the highest power cases by the 

magnitude of prior gas release. 

* Rod internal gas pressure increases with the accumulation of released fission 

gas. In the higher power PWR cases, as the power drops off near the end of 

life, the reduction in the plenum temperature offsets the increasing moles of 

fission gas.

7-1
800 43

700 39 

00 

600 35 a) 0D 

EC 

I-I 

500 -. Centerline Temperature 3 

-i-Average Fuel Temperature 

400 Stored Energy 

400 ...... 27 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-1. Fuel temperatures and stored energy for a BWR 

1 OxI 0 fuel rod with initial peak power of 5 kW/ft.

7-2
500

450 

-- _ Fuel O.D. 

-u-Cladding I.D. 

0o S-*--Cladding "400 O.D. 

E" 350 

3 0 0 - -" -A A .. A . . . -- -- 

250 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-2. Cladding temperatures and fuel surface temperature for a 

BWR 1 Ox1 0 fuel rod with initial peak power of 5 kW/ft.

7-3
60 150 

50 Gap Thickness 12 

50 -s-- Gap Conductance 125 

cc40 100 Cm 

E 0 

(130 75 ) 

:E 20 5 

0 

10- 25 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-3. Gap thickness and gap conductance for a BWR 

10x10 fuel rod with initial peak power of 5 kW/ft. 

7-4
4 *700 

3- 525 

CuL 

S2 '3502 

a)O 

175 

-.- Fission gas release 

--• Rod internal gas pressure 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-4. Fission gas release and rod internal gas pressure for a BWR 

1 Ox1 0 fuel rod with initial peak power of 5 kW/ft.

7-5
35

30 

-.-- at 9.5 feet 

25 at 6.5 feet 25 -h-at 2.5 feet 

0 

220 

C 15 

~10 

5 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-5. Oxide thickness at three axial locations for a BWR 

10x10 fuel rod with initial peak power of 5 kW/ft.

7-6
25000

20000 -0.1 

15000 0 

• 10000 -0 ? 

50 -0.2 

0 -0.3c 

-5000 S -0.4 

-10000 

-0.5 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-6. Cladding hoop stress and hoop strain for a BWR 

10x10 fuel rod with initial peak power of 5 kW/ft.

7-7

0.2
1000 53

900- 48 

800 43a ' 

00 

800 ... E 700 380 0 W 

600 __CenterlineTemperature 33 

-U--Average Fuel Temperature 

-- Stored Energy 500 11128 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-7. Fuel temperatures and stored energy for a BWR 

1Oxl0 fuel rod with initial peak power of 7 kW/ft.

7-8
500

450 

-.-- Fuel O.D. 

-- Cladding I.D. 

0~ Cladding O.D. 400 

CL 

S350 

250 ... 

0 10 20 30 40 50 60 

Average Burnup (GWd/t) 

Fig. 7-8. Cladding temperatures and fuel surface temperature for a 

BWR 1 Ox1 0 fuel rod with initial peak power of 7 kW/ft.

7-9

70
175

40 -'-Gap Thickness 140 

--- Gap Conductance 

01 

30 105 

.• :E 20 70_ 7 

0 

10 J 35 t 

00 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-9. Gap thickness and gap conductance for a BWR 

1 Ox1 0 fuel rod with initial peak power of 7 kW/ft.

7-10

50
9 600 

-.-- Fission gas release -- 500 

6~s- Rod internal gas pressure40 

400 

0-. U)300a,

010 a, U)i 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-10. Fission gas release and rod internal gas pressure for a BWR 

1 Ox1 0 fuel rod with initial peak power of 7 kW/ft.

7-11
35

30 

-•at 9.5 feet 

25 at 6.5 feet 

Co 

•220 

ro15 

10 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-11. Oxide thickness at three axial locations for a BWR 

10x10 fuel rod with initial peak power of 7 kW/ft.

7-12
0.2

20000 0.1 

15000 0 

S10000 -0.1 

S 5000 

ouu -0.2 cla. 

0 -0.3 

-5000 -0.4 

-10000 1 . -0.5 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-12. Cladding hoop stress and hoop strain for a BWR 

1 Ox1 0 fuel rod with initial peak power of 7 kW/ft.

7-13

25000
1200 63 

1100 58 

1000 53 

a 0oo 

S 900 48 

L 800 43 EC 

700 38 

600 -uAverage Fuel Temperature 33 

-- Stored Energy 

500 1128 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-13. Fuel temperatures and stored energy for a BWR 

10x1O fuel rod with initial peak power of 9 kW/ft.

7-14
500 

450 ' / Fuel O.D. 

-uCladding I.D. 

-&- Cladding O.D. 

'0-400 

CL 

E 350 - " " ; - - : 1 ." 411 : 

300 

250 J 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-14. Cladding temperatures and fuel surface temperature for a 

BWR 1 Ox1 0 fuel rod with initial peak power of 9 kW/ft.

7-15
4n -v 150 

32 120 

."- Gap Thickness 

E3_ Gap Conductance 0 

2490 

1 60 

8 - 30 (. 

0 

0 10 20 30 0 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-15. Gap thickness and gap conductance for a BWR 

1 OxI 0 fuel rod with initial peak power of 9 kW/ft.

7-16
6 700

5 •600 

o4500. 

. 3 -400

0 300 

2'-.- Fission Gas Release 

-s--Rod internal gas pressure 

1 -200 

0 100 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-16. Fission gas release and rod internal gas pressure for a BWR 

1 Ox1 0 fuel rod with initial peak power of 9 kW/ft.

7-17
30

25

- -at 9.5 feet ,-, + a t 6 .5 fe e t 

r 20 -*-at 2.5 feet 

0 

E "" 15 L. 

10

5 

0 10 20 30 40 50 60 70 

0 

Average Burnup (GWd/t) 

Fig. 7-17. Oxide thickness at three axial locations for a BWR 

1 OxI 0 fuel rod with initial peak power of 9 kW/ft.

7-18
20000 

15000 

10000

5000

0 

-5000 

-10000

0 10 20 30 40 50 60

Average Burnup (GWd/t)

Fig. 7-18. Cladding hoop stress and hoop strain for a BWR 

10x1O fuel rod with initial peak power of 9 kW/ft.

7-19

CL 

0. 

co

0.05 

-0.05 

-0.15 

-0.25 .

(U 

-0.35 

-0.45 

-0.55

70
1400 74 

1250 66 

o) 1100 58 

cu 950 50o 

E0 

800 42 

650 SAverage Centerline Fuel Temperature Temperature 34 

SStored Energy 

500 1 1 1 26 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-19. Fuel Temperatures and stored energy for a BWR 

1 Ox1 0 fuel rod with initial peak power of 11 kW/ft.

7-20
500

450 \ 

450* Fuel O.D. 

S\ -u--Cladding I.D. 

0 400 

a) 

E: 3501 IF

300 ,A _, ... A A_ A 

250 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-20. Cladding temperatures and fuel surface temperature for a 

BWR 1 Ox1 0 fuel rod with initial peak power of 11 kW/ft.

7-21
30 150 

25 ,125 i--Gap Thickness 

Ga C onductance 

0 

•20 100 0 E 

015 75 0) 

(00 

10 5 0 25 0 ..... 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-21. Gap thickness and gap conductance for a BWR 

1 Ox1 0 fuel rod with initial peak power of 11 kW/ft.

7-22
10 780

8 660 

6O ,540 .2 

a) a. 

CoL 

cc) 

a) U/, 

cc 4 420 C t3 a. 

2 300 

S--Fission gas releaseI 

-- -Rod internal gas pressure 

0 180 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-22. Fission gas release and rod internal gas pressure for a BWR 

1 Ox1 0 fuel rod with initial peak power of 11 kW/ft.

7-23
30

25 

SIatg 9.eet 

S20 at 6.5 feet 

0 S~at 2.5 feet 

u 15 

C) 

C 

" 10 I

5 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 7-23. Oxide thickness at three axial locations for a BWR 

1 0x1 0 fuel rod with initial peak power of 11 kW/ft.

7-24
20000 U U. 0.15

15000 

10000

20 30 40 50 60

-WW,

70

Average Burnup (GWd/t) 

Fig. 7-24. Cladding hoop stress and hoop strain for a BWR 

1 Ox1 0 fuel rod with initial peak power of 11 kW/ft.

7-25

-Stress

-- Strain

CL 

0~ 

0) 

0

5000

0 

-5000 

-10000

0 10

20000 0.15

0.05 

-0.05 

0 

-0.15 .E 

ca (I) 

-0.25 

-0.35 

-0.45
8. Calculations for PWR 14X14 Fuel

In the following figures, calculated values for PWR 14X14 fuel are plotted as a function of 

burnup for the parameters listed below: 

Fuel centerline temperature 

Average fuel temperature 

Stored energy 

Fuel O.D. temperature 

Cladding I.D. temperature 

Cladding O.D. temperature 

Gap thickness 

Gap conductance 

Fission gas release 

Rod internal gas pressure 

Oxide thickness 

Cladding hoop stress 

Cladding hoop strain 

Several general observations can be made about the calculated results: 

* Within the first few GWd/t of burnup, a temperature peak is observed that is the 

result of fuel densification. 

* Gap closure results in (a) the coming together of temperatures for fuel O.D. and 

cladding I.D. and (b) a sharp increase in gap conductance. The gap 

conductance increases again after a few time steps when the interaction 

between the pellet and cladding affects the contact conductance calculated for a 

closed gap. At this point there is also a large increase in stress, and the 

permanent strain changes directions. 

0 Some of the fission gas is released in spurts according to the Massih 

model in FRAPCON-3. This effect is apparent in many of the figures. 

Shorter time steps would produce slightly different looking curves, but the 

trend of gas release and the end-of-life gas release would be about the 

same. 

* The burnup enhancement of fission gas release is readily seen in the 

lower power cases, but it is obscured in the highest power cases by the 

magnitude of prior gas release. 

* Rod internal gas pressure increases with the accumulation of released fission 

gas. In the higher power PWR cases, as the power drops off near the end of 

life, the reduction in the plenum temperature offsets the increasing moles of 

fission gas.

8-1
1300 68 

1200 "63 

1100 -58 

1000 5 _ 

900 48>•, 

0.

O. 800 C 43 i 

700 43 8 

-*-Centerline Temperature•' 38 

600 -*-Average Fuel Temperature 33 

- 7-Stored Energy 

500 ' . 28 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-1. Fuel temperatures and stored energy for a PWR 

14x14 fuel rod with initial peak power of 9 kW/ft.

8-2
550

500 -- Cladding ,.D. 

--*Cladding O.D. 

0 

40) 

CL 

E 4 0 0

350 

300 ... 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-2. Cladding temperatures and fuel surface temperature for a 

PWR 14x14 fuel rod with initial peak power of 9 kWlft.

8-3
40 240 

35 35 -*-Gap Thickness -210 

30 --- Gap Conductance 180 

en• __ 0 

225 O 25 150 E 

S20 120 (D 

o15 90 

00 

10- 60 

5 - 30 

0 0 

110 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-3. Gap thickness and gap conductance for a PWR 

14x14 fuel rod with initial peak power of 9 kW/ft.

8-4
8 2000 

7_ 1800 

6 1600 

°5 1400 

CD 

4 9 • = E--a-1200 

S3 1000

2- -800 

1 " -- Fission gas release sue-600 

-- Rod internal gas pressurre 

0 T ,400 1 1 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-4. Fission gas release and rod internal gas pressure for a 

PWR 14x14 fuel rod with initial peak power of 9 kW/ft.

8-5
90 

80 

70 -- at 9.5 feet 70 • ~at 6.5 feet ,,• 

.••,• 6050--•-at 2.5 feet . 

~60 0 

E 50 

40 

:E30 

F.

20 

10 

0 L = 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-5. Oxide thickness at three axial locations for a PWR 

14x14 fuel rod with initial peak power of 9 kW/ft.

8-6
15000 0.4 

10000 0.2 

5000 0 

U) a0. 0 -0.2 .E

-5000-z -0.4 

-10000 S -0.6 

-15000 1 ' , , -0.8 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-6. Cladding hoop stress and hoop strain for a PWR 

14x14 fuel rod with initial peak power of 9 kW/ft.

8-7
1700 

1500

10 20 30 40 50

Average Burnup (GWd/t) 

Fig. 8-7. Fuel temperatures and stored energy for a PWR 

14x14 fuel rod with initial peak power of 11 kW/ft.

8-8

-.- Centerline Temperature 

-uAverage Fuel Temperature 

S-Stored Energy 

I p

1300 

1100 

900

0 

a) 

I

(U 

I

a) 

0E 

a) 

I700 

500

0

81 

73 

65 0) 

57>N 

49 

41 

33

60 70
550

500 -rn-Cladding I.D. 

Cladding O.D. 

0 

-450 

E 400 

I,,, 

350 

300 ... 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-8. Cladding temperatures and fuel surface temperature for a 

PWR 14x1 4 fuel rod with initial peak power of 11 kW/ft.

8-9
30 - 240 

25 -- Gap Thickness 200 

-- Gap Conductance 

0 

~20 1600Cm 

2 E 

S 15 1200 

•10 80 Coo 

0 0.. 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-9. Gap thickness and gap conductance for a PWR 

14x14 fuel rod with initial peak power of 11 kW/ft.

8-10
10 20 30 40 50 60

U. 25

70

Average Burnup (GWd/t) 

Fig. 8-10. Fission gas release and rod internal gas pressure in a PWR 

14x14 fuel rod with initial peak power of 11 kW/ft.

8-11

20 

~15 

10

5 

0

0

U- II U.

Fission gas release 

J I-f+-Rod internal gas pressure 

S._ . • .•, A m• A

2500 

2100 

1700 Z5 

1300 • 

0. 

900 

500
160

140 

-.- at 9.5 feet 

120 = at 6.5 feet 

"----at 2.5 feet 

S100 

rn 80 

. 60 

I

40 

20 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-11. Oxide thickness at three axial locations for a PWR 

14x1 4 fuel rod with initial peak power of 11 kW/ft.

8-12
8000 0.25 

4000 0 

0 -0.250 

0.1

Co CO 

ca -4000 -0.5 

-8000 -0.75 

SI • Stressl --Strain 

-12000 1 -1 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-12. Cladding hoop stress and hoop strain for a PWR 

14x14 fuel rod with initial peak power of 11 kW/ft.

8-13
,#,,.

_uuu 108 

1750- 95 

o 1500 82 

- 1250 

L. ~69 > a)0 

E0 

1000 56 

- Centerline Temperature 

750 -u-Average Fuel Temperature 43 

--&-Stored Energy 

500 130 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-13. Fuel temperatures and stored energy for a PWR 

14x14 fuel rod with initial peak power of 13 kW/ft.

8-14
10 20 30 40 50

Average Burnup (GWd/t) 

Fig. 8-14. Cladding temperatures and fuel surface temperature for a 

PWR 14x14 fuel rod with initial peak power of 13 kW/ft.

8-15

-- Fuel O.D. 

= Cladding I.D. 

-Cladding O.D.

U _____________________________________________ -

0

.550

500 

450 

.L 

E 400 I350 

300

0 70

A

.............. . ...........

60
18 

15

10 20 30 40 50 60

Average Burnup (GWd/t) 

Fig. 8-15. Gap thickness and gap conductance for a PWR 

14x14 fuel rod with initial peak power of 13 kW/ft.

8-16

IGap Thickness 

-- a Coducanc Ga 

0 

E. 

U~ 

Co 

:E

12 

9 

6

3 

0

0

240 

200 

0 

160 2 

120 0 

80 

0 

40 

40

70
10 20 30 40 50 60

Average Burnup (GWd/t) 

Fig. 8-16. Fission gas release and rod internal gas pressure for a 

PWR 14x14 fuel rod with initial peak power of 13 kW/ft.

8-17

30

25

20 

15 

10

0) 

cc

5 

0

0

-*-Fission gas release 

Rod internal gas pressure

70

2800 

2500 

2200 _ 

CL 

%0. 

1900 

CL 

1600 

1300 

1000
160 

140 

--2 at 9.5 feet 

120 -u-at 6.5 feet 

"CA -at 2.5 feet 

2 100 

• 80 

C, 

60 

I40 

20 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-17. Oxide thickness at three axial locations for a PWR 

14x14 fuel rod with initial peak power of 13 kW/ft.

8-18
6000 

4000 

2000 

0 

-2000 

-4000 

-6000 

-8000 

-10000 

-12000

10 20 30 40 50 60 

Average Burnup (GWd/t) 

Fig. 8-18. Cladding hoop stress and hoop strain for a PWR 

14x14 fuel rod with initial peak power of 13 kW/ft. 

8-19

0) 

Co 

Co 

0 

L. 

cn E3 8 E38E E

0.39 

0.26 

0.13 

0 

-0.13 

-0.26 

-0.39 

-0.52 

-0.65 

-0.78

01

0 70
2000 

1750

30 40 

Average Burnup (GWd/t)

Fig. 8-19. Fuel temperatures and stored energy for a PWR 

14x14 fuel rod with initial peak power of 15 kW/ft.

8-20

ie erature 

Avrg Fue Tempeatur

C 

0) 

1

Cu L. 

0) 

E 

4) 

I1500 

1250 

1000

108 

95 

82 

Co 

69 

I-L 

56 

43 

30

70

750 

500

0 10 20 50 60
-- Fuel O.D. 

•-u-Cladding I.D. 

•--Cladding O.D.

550 

500 

0 450 

.O 

'a0) 

CL 

350 

300

__1...-'N

-,N

50 60

Fig. 8-20. Cladding temperatures and fuel surface temperature for a 

PWR 14x14 fuel rod with initial peak power of 15 kW/ft.

8-21

I

U

. . .

-- - -

0 10 20 30 40 

Average Burnup (GWd/t)

70

- - 0

- A

] I I I
9 

8 

7 

6 

5 

4 

3 

2 

1 

0 I 

50 i 

60

Average Burnup (GWd/t)

Fig. 8-21. Gap thickness and gap conductance for a PWR 

14x14 fuel rod with initial peak power of 15 kW/ft.

8-22

I.. 

0, 

Co 

I--

-.- Gap Thickness 

-a- Gap Conductance

225

200 

175 

0 150 E 

125 E 

100 

U 75~ 

0 

50 

25

0

70 0 10 20 30 40
30 2900

25 2600 

ý20 2300 

CL 

S15 

S 10 1700 I 

-- Fission Gas Release 

5~~a Rod internal gas pressure -10 5 1400 

0 1100 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-22. Fission gas release and rod internal gas pressure in a PWR 

14x14 fuel rod with initial peak power of 15 kW/ft.

8-23
140

120 

--+-at 9.5 feet 

_. 100 - uat 6.5 feet 

S--*--at 2.5 feet 

0 

. 80 

42 60 

C.) 

40 

20

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-23. Oxide thickness at three axial locations for a PWR 

14x14 fuel rod with initial peak power of 15 kW/ft.

8-24
8000 

6000 

4000 

2000 

0 

-2000 

-4000 

-6000 

-8000 

-10000

10 20 30 40 50 60 

Average Burnup (GWd/t) 

Fig. 8-24. Cladding hoop stress and hoop strain for a PWR 

14x14 fuel rod with initial peak power of 15 kW/ft. 

8-25

-Stress 

-.-Strain

CL 

0) 

I0.36 

0.24 

0.12 

0 

-0.12 . 

-0.24 b 

(0 

-0.36 

-0.48 

-0.6 

-0.72

0 70
2100 100

1900 91 

1700 82 

(3- 1500 73 _ 

S1300 64 >b 

C) 

E C S1100 5 '' 

900 Centerline Temperature 46 

70 Average Fuel Temperature 37-' 

700 -a--Stored Energy 

500 1 28 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-25. Fuel Temperatures and stored energy for a PWR 

14x14 fuel rod with initial peak power of 16 kW/ft.

8-26
550

5 0 0 -. -. -u e l (U . D . SCladding I.D. 

A :--A Cladding O.D. 

400 5 

350 

30 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-26. Cladding temperatures and fuel surface temperature for a 

PWR 14x14 fuel rod with initial peak power of 16 kW/ft.

8-27
5 200 

4 160Thickness 

03 120 

0E) 

2- 80 

0 

1 40 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-27. Gap thickness and gap conductance for a PWR 

14x14 fuel rod with initial peak power of 16 kW/ft.

8-28
30 1 I

24 

0 

S18 

a1

I I I I

20 30 40 50

Average Burnup (GWd/t) 

Fig. 8-28. Fission gas release and rod internal gas pressure for a 

PWR 14x14 fuel rod with initial peak power of 16 kW/ft.

8-29

-- Rod internal gas pressure

6 

0

30

70 0 10

I

3300 

2800 

CC 2300 "• 

C. 

aO) 

aO) 1800 

CL 

1300 

800

60
120 

100 

Sat 9.5 feet 

o 80 -- at 6.5 feet 

0 

0 

C 

~40 

20 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-29. Oxide thickness at three axial locations for a PWR 

14x14 fuel rod with initial peak power of 16 kW/ft.

8-30
6000 0.2 

4000 0. ........ --- -II0 .. loýjjjII- + --- .1 

2000 

0 

• 0 

-0.1 

S-2000 

-0.2*.

-4000 

-0.3 C, 

-6000 

-0.4 

-- Stress -8000 Strain -0.5 

-10000 -0.6 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 8-30. Cladding hoop stress and hoop strain for a PWR 

14x14 fuel rod with initial peak power of 16 kW/ft. 

8-31
9. Calculations for PWR 15X15 Fuel

In the following figures, calculated values for PWR 15X15 fuel are plotted as a function of 

burnup for the parameters listed below: 

Fuel centerline temperature 

Average fuel temperature 

Stored energy 

Fuel O.D. temperature 

Cladding I.D. temperature 

Cladding O.D. temperature 

Gap thickness 

Gap conductance 

Fission gas release 

Rod internal gas pressure 

Oxide thickness 

Cladding hoop stress 

Cladding hoop strain 

Several general observations can be made about the calculated results: 

Within the first few GWd/t of burnup, a temperature peak is observed that is the 

result of fuel densification. 

Gap closure results in (a) the coming together of temperatures for fuel O.D. and 

cladding I.D. and (b) a sharp increase in gap conductance. The gap 

conductance increases again after a few time steps when the interaction 

between the pellet and cladding affects the contact conductance calculated for a 

closed gap. At this point there is also a large increase in stress, and the 

permanent strain changes directions. 

* Some of the fission gas is released in spurts according to the Massih 

model in FRAPCON-3. This effect is apparent in many of the figures. 

Shorter time steps would produce slightly different looking curves, but the 

trend of gas release and the end-of-life gas release would be about the 

same. 

* The bumup enhancement of fission gas release is readily seen in the 

lower power cases, but it is obscured in the highest power cases by the 

magnitude of prior gas release. 

* Rod internal gas pressure increases with the accumulation of released fission 

gas. In the higher power PWR cases, as the power drops off near the end of 

life, the reduction in the plenum temperature offsets the increasing moles of 

fission gas.

9-1
1300 70 

1100 60 

0 

6"M 

900 50 . 

EC 

I700 _ 40 

-- Centerline Temperature 

-Average Fuel Temperature 

-&- Stored Energy 

500 1 1 30 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-1. Fuel temperatures and stored energy for a PWR 

15x15 fuel rod with initial peak power of 9 kW/ft.

9-2

mA
550

SFuel O.D. 

o1..•••Ee 40450m Cladding O.D. . 

S| -*- Cladding I.D. 

50 

~-450

0. 

350 

300 I 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-2. Cladding temperatures and fuel surface temperature for a 

PWR 15x1 5 fuel rod with initial peak power of 9 kW/ft.

9-3
40 240 

35 210 

30 Gap Thickness 180 -- i-G pConductance 0 

O 25 150 E 

120 120 t 

30 

0 .0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-3. Gap thickness and gap conductance for a PWR 

15x15 fuel rod with initial peak power of 9 kW/ft.

9-4
8 2200 

7 2000 

6 1800 

5 1600 ._ 

Cu 0 

4 1400 0 

u3 1200 

2 

1000 

1 --- Fission gas release 800 

Rod internal gas pressure 

0 600 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-4. Fission gas release and rod internal gas pressure for a PWR 

15x15 fuel rod with initial peak power of 9 kW/ft.

9-5
90 

80° 

70 - at 9.5 feet 

-uat 6.5 feet 

C 60 at 2.5 feet 

0 

10. 

~40

:E30

20

10

0 . I I.-b 

O 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-5. Oxide thickness at three axial locations for a PWR 

15x15 fuel rod with initial peak power of 9 kW/ft.

9-6
15000

10000 0.1 

5000 -0.1 

CL ~0

S0 -0.3 . 0 1. 

(I) 

-5000 -0.5 

-10000 -0.7 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-6. Cladding hoop stress and hoop strain for a PWR 

15x15 fuel rod with initial peak power of 9 kW/ft.

9-7

0.3
1500

1300 70 

°oo 0o 10 60' 

CU 0 

E900 50C. 

I.

700 -.- Centerline Temperature 40 - Average Fuel Temperature"

-*--Stored Energy 

500 , , , , 30 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-7. Fuel temperatures and stored energy for a PWR 

15x15 fuel rod with initial peak power of 11 kW/ft.

9-8

80
550 

500 Cladding I.D. 

Cladding O.D. 

0 S450 

E 4 0 0 

1

350 

300 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-8. Cladding temperatures and fuel surface temperature for a 

PWR 15x1 5 fuel rod with initial peak power of 11 kW/ft.

9-9
30 240 

25 _ _ _ _200 S-*- Gap Thickness . 

-- Gap Conductance 

160 EC 

S15 120 o 

I- 0 

C. 

5 40 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-9. Gap thickness and gap conductance for a PWR 

15x15 fuel rod with initial peak power of 11 kW/ft.

9-10
15

50 60

-- RFission gas release 

SB Rod internal gas pressureI

70

Average Burnup (GWd/t) 

Fig. 9-10. Fission gas release and rod internal gas pressure for a 

PWR 15x1 5 fuel rod with initial peak power of 11 kW/ft.

9-11

2500 

2100 

1700 "• 

C. 

0 

1300 2 

900 

500

12 

0-9 

0 

0 6 

3 

0

0 10 20 30 40
A

-at 9.5 feet 

I-a-at 6.5 feet 

L-a-at 2.5 feet

I 

10 20 30 40 

Average Burnup (GWd/t)

50 60 70

Fig. 9-11. Oxide thickness at three axial locations for a PWR 

15x1 5 fuel rod with initial peak power of 11 kW/ft.

9-12

140

120 

100 

80 

60 

40

C,, 

C 

0 

I

C.) E 

(A 

CA 

C 

C.) :2 

I20 

0

0
9000 0.4 

6000 . 0.2 

3000-r - 2 0 

0 -0.2 

S-3000 -0.4 

-6000 -0.6 

-- Stress 

%-i-Strain 

-9000 -0.8 

-12000 -1 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-12. Cladding hoop stress and hoop strain for a PWR 

15x15 fuel rod with initial peak power of 11 kW/ft.

9-13

A m
1900 

1700 

1500 

1300 

1100 

900 

700 

500

10 20 30 40 50 60

Average Burnup (GWd/t) 

Fig. 9-13. Fuel temperatures and stored energy for a PWR 

15x15 fuel rod with initial peak power of 13 kW/ft.

9-14

0 

E I-.

Centerline Temperatu re --*-Average Fuel Temperature 

-A Stored Energy

86 

78 

70 

62 

54 

46 

38 

30

0 70
550

5O00 500 Fuel O.D. 

-,-Cladding I.D. 

0 450 

CL 

E 400 

I

350 

300 , 

0 10 20 30 40 50 60 

Average Burnup (GWd/t) 

Fig. 9-14. Cladding temperatures and fuel surface temperature for a 

PWR 15x15 fuel rod with initial peak power of 13 kW/ft.

9-15

70
16 240 

14 210 

12 Gap Thickness 180 

1 Gap Conductance , 

1 150E 

2010 

S120 

Ca 

6 900 

4 60O 

2. 30 

0 ..... 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-15. Gap thickness and gap conductance for a PWR 

15x15 fuel rod with initial peak power of 13 kW/ft.

9-16
20 2400 

17.5 2200 

15 2000 

S 12.5 1800 .5. 

C. 

S 7.5 1400 , 

5 Fission Gas Release 1200 

2.5• -- Rod internal gas pressure 10 

2.15 16000 

0 800 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-16. Fission gas release and rod internal gas pressure for a 

PWR 15x15 fuel rod with initial peak power of 13 kW/ft.

9-17
120 

100 

Sat 9.5 feetI 

80,--e- at 6.5 feet MEM 

80 --*--at 2.5 feet 

E 06o 

": I-- 2, 40 ._ .

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-17. Oxide thickness at three axial locations for a PWR 

15x15 fuel rod with initial peak power of 13 kW/ft.

9-18
8000 0.2 

6000 0.1 

4000 0 o 

2000 -0.1 

0 -0.2 

-2000 -0.3 U) -4000 -0.4 i 

-6000 -0.5 

-8000 -.- Stress -0.6 

-a- Strain -10000 -0.7 

-12000 -0.8 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-18. Cladding hoop stress and hoop strain for a PWR 

15x15 fuel rod with initial peak power of 13 kW/ft. 

9-19
2100 110

1900 100 

1700 90 

1500 80 "j 

S1300 

70 >•0, 

E 1100 60,W 

900 50 

---Centerline Temperature ' ,,. 

700 - Average Fuel Temperature 40 

.--&- Stored Energy 

500 30 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-19. Fuel Temperatures and stored energy for a PWR 

15x15 fuel rod with initial peak power of 15 kW/ft,

9-20
550

500 

-'--Fuel O.D. 

-u--Cladding I.D. 

o• 450 -i--Cladding O.D. 

CL 

E 4 00 

I350 

300 . 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-20. Cladding temperatures and fuel surface temperature for a 

PWR 15x15 fuel rod with initial peak power of 15 kW/ft.

9-21
8 240 

7 210 

6 -4-- Gap Thickness 10 

6 -B-Gap Conductance 180 

0 

0 5.150 E 

E 

004 120 

3 F 90 

0 2 600 

1 30 

0 IIIII0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-21. Gap thickness and gap conductance for a PWR 

15x15 fuel rod with initial peak power of 15 kW/ft.

9-22
2 UI 

*--- Fission gas release 

-E- Rod internal gas pressure

I I

20 30 40 50 60

I

25

-600 

0

70

Average Burnup (GWd/t)

Fig. 9-22. Fission gas release and rod internal gas pressure for a 

PWR 15x15 fuel rod with initial peak power of 15 kW/ft.

9-23

UU

20 

S15 

010

5 

0

L 0I,

0 --

0 10

,i I

S

3000 

-2400 

Oa 1800 *0 

1200 0 

CIL
120 

100 

-4at 9.5 feet 

S 80 - at6.5 feet 

0 S-k-at 2.5 feet 

S60 

20 

" 40 

20 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-23. Oxide thickness at three axial locations for a PWR 

15x15 fuel rod with initial peak power of 15 kW/ft.

9-24
6000 0.45 

4000o -0.3 

2000 0.15 

0 0 

0 -2000 

-0.15 .E 

co -4000 -0.3 ca 

-6000 -0.45 

-8000 __ Stress -0.6 

Strain 

-10000 -0.75 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 9-24. Cladding hoop stress and hoop strain for a PWR 

15x15 fuel rod with initial peak power of 15 kW/ft. 

9-25
10. Calculations for PWR 16X16 Fuel

In the following figures, calculated values for PWR 16X16 fuel are plotted as a function of 

burnup for the parameters listed below: 

Fuel centerline temperature 

Average fuel temperature 

Stored energy 

Fuel O.D. temperature 

Cladding I.D. temperature 

Cladding O.D. temperature 

Gap thickness 

Gap conductance 

Fission gas release 

Rod internal gas pressure 

Oxide thickness 

Cladding hoop stress 

Cladding hoop strain 

Several general observations can be made about the calculated results: 

* Within the first few GWd/t of burnup, a temperature peak is observed that is the 

result of fuel densification. 

Gap closure results in (a) the coming together of temperatures for fuel O.D. and 

cladding I.D. and (b) a sharp increase in gap conductance. The gap 

conductance increases again after a few time steps when the interaction 

between the pellet and cladding affects the contact conductance calculated for a 

closed gap. At this point there is also a large increase in stress, and the 

permanent strain changes directions. 

Some of the fission gas is released in spurts according to the Massih 

model in FRAPCON-3. This effect is apparent in many of the figures. 

Shorter time steps would produce slightly different looking curves, but the 

trend of gas release and the end-of-life gas release would be about the 

same. 

0 The bumup enhancement of fission gas release is readily seen in the 

lower power cases, but it is obscured in the highest power cases by the 

magnitude of prior gas release. 

0 Rod internal gas pressure increases with the accumulation of released fission 

gas. In the higher power PWR cases, as the power drops off near the end of 

life, the reduction in the plenum temperature offsets the increasing moles of 

fission gas.

10-1
10 20 30 40 50 60

Average Burnup (GWd/t)

Fig. 10-1. Fuel temperatures and stored energy for a PWR 

16x1 6 fuel rod with initial peak power of 9 kW/ft.

10-2

1300 

1200 

1100 

1000 

900 

800

0 

CL 

E

700 

600 

500

0

64

- A e " 11111- .......... Ale ...........

70

SCenterline Temperature -- !-=-Average Fuel Temperature 

SStored Energy

60 

56 

52 

(U 

48>, I44 W 

40 

36 

32
550

SFuel O.D. 

+Cladding I.D. 

o•-*-Cladding 0. D. 

450 

E 400 

350 - A- -*777* "7"7'11'i" 300 300.... 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-2. Cladding temperatures and fuel surface temperature for a 

PWR 16x16 fuel rod with initial peak power of 9 kW/ft.

10-3
30 240 

25 __ _ _ _ __ _ _ _ _200 

5--- Gap Thickness 

--Gap Conductance 0 20 160 N1 0 E "E 

t 1512 

S120 0 

80 

5 - 40 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-3. Gap thickness and gap conductance for a PWR 

16x16 fuel rod with initial peak power of 9 kW/ft.

10-4
In

"* -1700 

8- 1500 

6- 1300 "Vi 

S4 1100 

Fission gas release 

El- Rod internal gas pressure 2 900 

0 

700 0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-4. Fission gas release and rod internal gas pressure for a 

PWR 16x16 fuel rod with initial peak power of 9 kW/ft.

10-5
160 

140 -- at 9.5 feet 

Sat 6.5 feet 

120- - at 2.5 feet 

2100 

"-"80

-60 

40 

20 

0

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-5. Oxide thickness at three axial locations for a PWR 

16x1 6 fuel rod with initial peak power of 9 kWlft.

10-6
10000

5000 

0 

n -5000 

-10000 

-15000

0 10 20 30 40 50 60

Average Burnup (GWd/t)

Fig. 10-6. Cladding hoop stress and hoop strain for a PWR 

16x16 fuel rod with initial peak power of 9 kW/ft.

10-7

0.6

0.3 

0 

01-1 

-0.3 cn 

-0.6 

-0.9

70
1700 9

1500 80 

o 1300 -70 

............ 

' 1100 60>, 2.. "0.. 

a) L 

E Cj 900 50 

70 Centerline Temperature "_• 40 

700 4 

-u-Average Fuel Temperature 

S-Stored Energy 

500 1 1 30 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-7. Fuel temperatures and stored energy for a PWR 

16x1 6 fuel rod with initial peak power of 11 kW/ft.

10-8

1700 90
550 

500 y• • Fuel O.D. 

.-u-Cladding I.D. 

450 Cladding O.D. 

E 400 

350 

4300 1 

350 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-8. Cladding temperatures and fuel surface temperature for a PWR 16x1 6 fuel rod with initial peak power of 11 kW/ft.

10-9
25 250 

20 __200 S (/•I +Gap Thickness, 

0 

0 E 

S 15 150 

C 

0E V 

(00 

5 50 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-9. Gap thickness and gap conductance for a PWR 

1 6x1 6 fuel rod with initial peak power of 11 kW/ft.

10-10
''~ 2400 

12 2100 

S1800 

U)L 

___6 1500 ---Fission gas release I L 

- Rod internal gas pressure 

3 1200 

0 - 900 0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-10. Fission gas release and rod internal gas pressure for a 

PWR 16x1 6 fuel rod with initial peak power of 11 kW/ft.

10-11

I r
120 

100 

-- at 9.5 feet 

" 80-- -u-at 6.5 feet 

0 _--at 2.5 feet 

0 

E 

c 60 

U) 

:E 40 

20 

0

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-11. Oxide thickness at three axial locations for a PWR 

16x1 6 fuel rod with initial peak power of 11 kW/ft.

10-12
6000 0.3

3000 0.1 

0 -0.1 

C. 

S-3000 -0.3 .0 

-6000 -0.5 

-9000 Stress-0.7 ---• Strain -. 

-12000 Stan-0.9 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-12. Cladding hoop stress and hoop strain for a PWR 

16x1 6 fuel rod with initial peak power of 11 kW/ft.

10-13
1700 80 

1500 72 

1300 64 

00 

""O 1100 56 

900 48 

7 Centerline - Temperature40 700 • ~Average Fuel Temperature 4 

-a-Stored Energy 

500 .. 32 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-13. Fuel temperatures and stored energy for a PWR 

16x16 fuel rod with initial peak power of 13 kW/ft.

10-14
-- Fuel O.D. 

-u-Cladding I.D. 

-*-Cladding O.D.

500 

°O• 450 

I.. 

E 400 

0) 

350 

300

N

30 40 

Average Burnup (GWd/t)

50 60

Fig. 10-14. Cladding temperatures and fuel surface temperature for a 

PWR 16x1 6 fuel rod with initial peak power of 13 kW/ft.

10-15

550

-1

N; SUJL ,

0 10 20 70

M -
.1 rle 240 

10 200 

4-Gap Thickness 

S8 160 

E 

6 120 o 

4 80 " 

0 

2 40 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-15. Gap thickness and gap conductance for a PWR 

16x16 fuel rod with initial peak power of 13 kW/ft.

10-16
20 2500

16 2100 

° 12 cc' 

11700 

oo 

08 m __ _ _ __ _ _ 13000 

*. Fission Gas Release 

4 , -a E3- Rod internal gas pressure 900 

0 

500 0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-16. Fission gas release and rod internal gas pressure for a 

PWR 16x16 fuel rod with initial peak power of 13 kW/ft.

10-17
100 

90 

80 

-'-at 9.5 feet 

70 -- at 6.5 feet C60 F at 2.5feet 

==. 50 (0 N

20 

10 

0 

0 10 20 30 40 50 60 

Average Burnup (GWd/t) 

Fig. 10-17. Oxide thickness at three axial locations for a PWR 

16x16 fuel rod with initial peak power of 13 kW/ft.

10-18

70
5000 0.4

2500 0.2 

0 0 

CL 1-0 

c -2500 -2 CO) -0.2 . 

-5000 -0.4 

-7500 Stress -0.6 

-1- Strain 

-10000 -0.8 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-18. Cladding hoop stress and hoop strain for a PWR 

16x16 fuel rod with initial peak power of 13 kW/ft.

10-19
1900 88 

1700 80 

1500 72 

0 0 

° 1300 64 

56~ 

a. 1100 

E wU 

1

900 48 

700 i Average Fuel Temperature 40 

SStored Energy 

500 L 32 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-19. Fuel Temperatures and stored energy for a PWR 

16x16 fuel rod with initial peak power of 14 kW/ft.

10-20
550

500 

--- Fuel O.D. 

-U- Cladding I.D. 

0450 -- Cladding O.D. - 450 

CL 

E 4 0 0 

350 

300 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-20. Cladding temperatures and fuel surface temperature for a 

PWR 16x16 fuel rod with initial peak power of 14 kW/ft.

10-21
8 240 

7 -210 

--- Gap Thickness18 

6 --a- Gap Conductance 180, 

S5 150 

u) 4 120 ) 

Co 

3 90 = 

2 600 

1 30 

0 .. 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-21. Gap thickness and gap conductance for a PWR 

16x16 fuel rod with initial peak power of 14 kW/ft.

10-22
18 

16 

14 

12 

10 

8 

6

4 

2 

0

0 10 20 30 40 50 60

Average Burnup (GWd/t)

Fig. 10-22. Fission gas release and rod internal gas pressure for a 

PWR 16x1 6 fuel rod with initial peak power of 14 kW/ft.

10-23

0 

a)

2400 

2200 

2000 

1800 

1600 . 

1400 

1200 

1000 

800 

600

70
90 

80 

70 

0-u-at 9.5 feet 

60 •at 6.5 feet 

(0 

(I) 

104 

0 -m=a-.

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 10-23. Oxide thickness at three axial locations for a PWR 

16x16 fuel rod with initial peak power of 14 kW/ft.

10-24
10 20 30 40 50 60 

Average Burnup (GWdIt) 

Fig. 10-24. Cladding hoop stress and hoop strain for a PWR 

16x16 fuel rod with initial peak power of 14 kW/ft. 

10-25

CI, 

CD

6000 

4000 

2000 

0 

-2000 

-4000 

-6000 

-8000 

-10000

SI--.-Stress 

/ •St rain

0.3 

0.15 

0 

-0.15 

-0.3 

-0.45 

-0.6 

-0.75 

-0.9

0 70

015-
11. Calculations for PWR 17X1 7 Fuel

In the following figures, calculated values for PWR 17X17 fuel are plotted as a function of 

burnup for the parameters listed below: 

Fuel centerline temperature 

Average fuel temperature 

Stored energy 

Fuel O.D. temperature 

Cladding I.D. temperature 

Cladding O.D. temperature 

Gap thickness 

Gap conductance 

Fission gas release 

Rod internal gas pressure 

Oxide thickness 

Cladding hoop stress 

Cladding hoop strain 

Several general observations can be made about the calculated results: 

* Within the first few GWd/t of burnup, a temperature peak is observed that is the 

result of fuel densification. 

* Gap closure results in (a) the coming together of temperatures for fuel O.D. and 

cladding I.D. and (b) a sharp increase in gap conductance. The gap 

conductance increases again after a few time steps when the interaction 

between the pellet and cladding affects the contact conductance calculated for a 

closed gap. At this point there is also a large increase in stress, and the 

permanent strain changes directions. 

"* Some of the fission gas is released in spurts according to the Massih 

model in FRAPCON-3. This effect is apparent in many of the figures. 

Shorter time steps would produce slightly different looking curves, but the 

trend of gas release and the end-of-life gas release would be about the 

same. 

"* The bumup enhancement of fission gas release is readily seen in the 

lower power cases, but it is obscured in the highest power cases by the 

magnitude of prior gas release. 

0 Rod internal gas pressure increases with the accumulation of released fission 

gas. In the higher power PWR cases, as the power drops off near the end of 

life, the reduction in the plenum temperature offsets the increasing moles of 

fission gas.

11-1
1200 68 

1100 

62 

1000 56 

0 900 50 

S 800 

4 

1., 44> 

oE70 

70 

38 

600 

32 I+Centerline Temperature 

500 - Average Fuel Temperature 26 

S-Stored Energy 

400 

20 0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-1. Fuel temperatures and stored energy for a PWR 

17x17 fuel rod with initial peak power of 7 kW/ft. 

11-2
550 

500 

--Fuel O.D. 

-u-Cladding I.D. 

*40 --*--Cladding O.D. 

E 4 0 0 

i-. 

350_ 

300 1 I , 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-2. Cladding temperatures and fuel surface temperature for a 

PWR 17x17 fuel rod with initial peak power of 7 kW/ft.

11-3
40 240 

35 35 p == a~a" _ -210 --•Gap Thickness21 

30 ~Gap Conductance -180 

S 25 150 

S 20 2120 

S15 -90 

10 60- 0 

5 -30 

0 , , , 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-3. Gap thickness and gap conductance for a PWR 

17x17 fuel rod with initial peak power of 7 kW/ft.

11-4
,4

"1400 

3 1225 

0)ý 

CL 

2 1050 2 

CO) 

1 875 

- Fission gas release 

-s---Rod internal gas pressure 0 700 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-4. Fission gas release and rod internal gas pressure for a 

PWR 17x17 fuel rod with initial peak power of 7 kW/ft.

11-5
10

70 

60 

40 

c30 

20 

10 

0

30 40

0 

50

I 

60

Average Burnup (GWd/t) 

Fig. 11-5. Oxide thickness at three axial locations for a PWR 

17x17 fuel rod with initial peak power of 7 kW/ft.

11-6

80

0 20 70

--at 9.5 feet 

............ .. ....... lilil ýý 
20000 

15000 

10000 

5000 

0 

-5000 

-10000 

-15000

10 20 30 40 50 60 70

Average Burnup (GWd/t)

Fig. 11-6. Cladding hoop stress and hoop strain for a PWR 

17x17 fuel rod with initial peak power of 7 kW/ft.

11-7

Ci,

0.15 

0 

-0.15 

-0.3 

-0.45 U) 

-0.6 

-0.75 

-0.9

0
1300 64 

1200 60 

110056 

°-- 1000 52 " 

......... 

'• 900 48>, ,.., 

800- 44 w 

1

700 - 40 

-.- Centerline Temperature 

600 - Average Fuel Temperature 36 

S-Stored Energy 

500 , , 1 , 32 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-7. Fuel temperatures and stored energy for a PWR 

17x17 fuel rod with initial peak power of 9 kW/ft.

11-8
550

500 

50- Fuel O.D. 

--*Cladding 1.D. 

40 i Cladding O.D. ~450 

C

0. 

E 4 00 

1

350 " A" A "- -- - - -

300 

300III 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-8. Cladding temperatures and fuel surface temperature for a 

PWR 17x17 fuel rod with initial peak power of 9 kW/ft.

11-9
30 

25

10 20 30 40 50 60

Average Burnup (GWd/t) 

Fig. 11-9. Gap thickness and gap conductance for a PWR 

17x17 fuel rod with initial peak power of 9 kW/ft.

11-10

'It/ 

G a p T h ic k n e s s --a-- Gap Conductance

0 

E

C)

20 

15 

10

5 

0

240 

200 

0 160 E 

120 C) 

m 

80 C 0 

40 

40

0 70
6 1500 

5 1400 -.- Fission gas release 

SRod internal gas pressure' 

A4 1300 

3- - 1200 

52- 1100 

1 - 1000 

0 900 0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-10. Fission gas release and rod internal gas pressure for a 

PWR 17x17 fuel rod with initial peak power of 9 kW/ft.

11-11
120 

100 

-.-•at 9.5 feet 

-,,-at 6.5 feet 

80 -- at 2.5 feet 

0 

Co 60 

Co) 

: 40 

20 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-11. Oxide thickness at three axial locations for a PWR 

17x1 7 fuel rod with initial peak power of 9 kW/ft.

11-12
15000 0.2 

10000 0 

5000 -0.2 

0 -0.4 S 

S-5000 -0.6 

-10000 -0.8 

-15000 -1 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-12. Cladding hoop stress and hoop strain for a PWR 

17x17 fuel rod with initial peak power of 9 kW/ft.

11-13
1500

1300 

0- 1100 

CL. 

E 900 

I700 1

500

--- Centerline Temperature 

-uAverage Fuel Temperatu 

--- Stored Energy

10 20 30 40 50 60 

Average Burnup (GWd/t) 

Fig. 11-13. Fuel temperatures and stored energy for a PWR 

17x17 fuel rod with initial peak power of 11 kW/ft.

11-14

................. ............. 

..................

7

1N

re

0

I 34

70

69 

62 

48 

41

MLý
550 

500 FuelO.D. 

-u-Cladding I.D. 

S-Cladding O.D. 

0°- 450 

E 400 _= 

a) 

1

350 

300 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-14. Cladding temperatures and fuel surface temperature for a 

PWR 17x17 fuel rod with initial peak power of 11 kW/ft.

11-15
-.- Gap Thickness 

-.- Gap Conductance

I - - I I

0 10 20 30 40 50

Average Burnup (GWd/t) 

Fig. 11-15. Gap thickness and gap conductance for a PWR 

17x1 7 fuel rod with initial peak power of 11 kW/ft.

11-16

20

16 

0 

~12 

8I

4 

0

250 

200 

0 

E 150 

0 

0, 

0

I

50 

0

60 70

11
10 1650 

9- 1575 

8- 1500 

7 1425 

•'• 6 •1350i 

5 12752 

4 1200 

3 -.- Fission Gas Release 1125 

-2- Rod internal gas pressure 2 1050 

1 975 

0 900 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-16. Fission gas release and rod internal gas pressure for a 

PWR 17x17 fuel rod with initial peak power of 11 kW/ft.

11-17
100 

90 

80 

at 9.5 feet 

70 -at 6.5 feet 

o 60 at2.5feet 

c• 50 

CI 

• 40 

•-30 

20 

10 

0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-17. Oxide thickness at three axial locations for a PWR 

17x1 7 fuel rod with initial peak power of 11 kW/ft.

11-18
0.2 15000

10000 0 

5000 -0.2 

-0.4 8E 

cc 0 cc 

(I) 

-5000 -0.6 

-100Stress -0.8 

-10000 --E- Strain 

-15000 1 -1 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-18. Cladding hoop stress and hoop strain for a PWR 

17x1 7 fuel rod with initial peak power of 11 kWlft.

11-19
1700 84 

1500 75 

1300 66 

S 1100 •. ~57 

CL 

900 48 

70 Centerline Temperatu re _•' 4 

700 -- Average Fuel Temperature 39 SStored Energy 

500 

0 10 20 30 40 50 60 7030 

Average Burnup (GWd/t) 

Fig. 11-19. Fuel Temperatures and stored energy for a PWR 

17x17 fuel rod with initial peak power of 13 kW/ft.

11-20
550

500 --*Cladding I.D. 

SCladding O.D. 

0 

450 

CL E. 400 

..... ....... 

30. 

34 00 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-20. Cladding temperatures and fuel surface temperature for a 

PWR 17x17 fuel rod with initial peak power of 13 kW/ft.

11-21
12 240 

10 _200 -__ 

-- Gap Thickness 

GapCoductance 0 

8 ~160 'Cm 

.C.8 

0- 0E 

6. 120 

:E 4! 8o0" 

0 

2 40 

0 0 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-21. Gap thickness and gap conductance for a PWR 

17x17 fuel rod with initial peak power of 13 kW/ft.

11-22
15 2000

12 

0-0 

,•6 

3. 

0 I I.

30 40 50

Average Burnup (GWd/t) 

Fig. 11-22. Fission gas release and rod internal gas pressure for a 

PWR 17x17 fuel rod with initial peak power of 13 kW/ft.

11-23

1 0

U 4;

-__- Fission gas release 

-a- Rod internal gas pressure

1800 

1600 "• 

1400 

1200 

1000

0 10 20

I.

60 70

• •ur A

15 2000

/,
90 

80 

70 

60 

50 

40 

30 

20 

10 

0

10 20 30 40 50 60

Average Burnup (GWdIt) 

Fig. 11-23. Oxide thickness at three axial locations for a PWR 

17x17 fuel rod with initial peak power of 13 kW/ft.

11-24

0,= 

I-

-- at 9.5 feet -r 

--- at 6.5 feet A-at 2.5 feet 

i1ý.11111d ........

0 70

-, e
9000

6000 0.4 

3000 0.2 

C o 

". -3000 -0.2 

-6000- -0.4 

-9000 -0.6 

-12000 , -0.8 

0 10 20 30 40 50 60 70 

Average Burnup (GWd/t) 

Fig. 11-24. Cladding hoop stress and hoop strain for a PWR 

17x17 fuel rod with initial peak power of 13 kW/ft.

11-25

0.6
12. REFERENCES

1. D. L. Acey and J. C. Voglewede, A Comparative Analysis of LWR Fuel Designs, 

NUREG-0559, July 1980. 

2. C. E. Beyer, C. R. Hann, D. D. Lanning, F. E. Panisko, L. J. Parchen, User's Guide for 

GAPCON-THERMAL-2: A Computer Program for Calculating the Thermal Behavior of 

an Oxide Fuel Rod, BNWL-1 897, November 1975. 

3. C. E. Beyer, C. R. Hann, D. D. Lanning, F. E. Panisko, L. J. Parchen, GAPCON

THERMAL-2; A Computer Program for Calculating the Thermal Behavior of an Oxide 

Fuel Rod, BNWL-1 898, November 1975. 

4. D. D. Lanning, C. E. Beyer, C. L. Painter, FRAPCON-3: Modifications to Fuel Rod 

Material Properties and Performance Models for High-Burnup Applications, Volume 1, 

NUREG/CR-6534, December 1997. 

5. G. A. Berna, C. E. Beyer, K. L. Davis, D. D. Lanning, FRAPCON-3: A Computer Code 

for the Calculation of Steady-State, Thermal-Mechanical Behavior of Oxide Fuel Rods 

for High Burnup, Volume 2, NUREG/CR-6534, December 1997. 

6. D. D. Lanning, C. E. Beyer, G. A. Berna, FRAPCON-3: Integral Assessment, Volume 3, 

NUREG/CR-6534, December 1997. 

7. C. L. Painter, J. M. Alvis, C. E. Beyer, A. L. Marion, G. A. Payne, E. D. Kendrick, Fuel 

Performance Annual Report for 1991, Volume 9, NUREG/CR-3950, August 1994. 

8. General Electric Fuel Bundle Designs, NEDE-31152P, Revision 8, Class Ill (only non

proprietary portions were utilized), April 2001. 

9. Characteristics of Potential Repository Wastes, Oak Ridge National Laboratory, 

DOE/RW-0184-Ri, Volume 1, July 1992.

12-1
Table Al. Non-proprietary BWR Fuel Design Parameters

Fuel Vendor GE GE SNP SNP SNP SNP GE 

Array 8x8 8x8 9x9 9x9 9x9 9x9 10x10 

Version Barrier GE-4a JP-3 JP-4,5 IX 9X 

Typical Number of Fuel 62 63 79 79 72 72 92 

Rods per Assembly 

Pitch (mm, in.) 16.26 16.26 14.52 14.52 14.45 14.45 

0.640 0.640 0.572 0.572 0.569 0.569 

Cladding OD (mm, in.) 12.27 12.52 10.76 10.76 10.95 10.95 

0.483 0.493 0.424 0.424 0.431 0.431 

Cladding ID (mm, in.) 10.64 10.80 9.25 9.25 9.68 9.68 

0.419 0.425 0.364 0.364 0.381 0.381 

Cladding Thickness (mm, in.) 0.813 0.863 0.762 0.762 0.635 0.635 

0.032 0.034 0.030 0.030 0.025 0.025 

Gap Thickness (mm, in.) 0.115 0.115 0.095 0.095 0.105 

0.0045 0.0045 0.0037 0.0037 0.0041 

Fuel Diameter (mm, in.) 10.41 10.57 9.05 9.50 9.47 

0.410 0.416 0.356 0.374 0.373 

Fuel Pellet Length (mm, in.) 10.41 10.67 10.41 

0.410 0.420 0.410 

Fuel Rod Length (m, in.) 4.20 4.09 4.04 4.16 

165.4 161.1 159.1 163.8 

Active Fuel Length (m, in.) 3.68 3.71 3.68 3.81 3.81 3.81 

145 146 145 150 150 150 

Plenum Length (m, in.) 0.241 0.356 0.243 0.243 

9.48 14.00 9.58 9.58 

Average Enrichment 2.06 2.64 2.92 

atom% 

Fuel Density (% TD) 95.0 95.0 94.5 94.5 96.3 94.5 

System Pressure (Mpa, psia) 7.14 7.14 7.07 

1035 1035 1026 

Helium fill gas pressure 207 0 414 414 

(kPa, psig) 30 0 60 60 

a. All values are from Ref. 7 except as noted

A-1
Table A2. Non-proprietary PWR Fuel Design Parameters 

Fuel Vendor ABB SNP SNP W B&W B&W SNP W Array 

Version 

14x14 14x14 14x14 14x14 15x15 15x15 15x15 15x15 CE ABB CE Top Rod WE Mark B Mark BW W WE Typical Number of Fuel 164 176 179 176 208 204 204 204 Rods per Assembly I 

Pitch (mm, in.) 14.73 14.73 14.12 14.73 14.4 14.3 14.3 14.3 0.580 0.580 0.556 0.580 0.568 0.563 0.563 0.563 Cladding OD (mm, in.) 11.17 11.17 10.59 11.17 10.92 10.72 10.76 10.72 0.440 0.440 0.417 0.440 0.430 0.422 0.424 0.422 Cladding ID (mm, in.) 9.75 9.61 9.11 9.85 9.58 9.35 9.25 9.48 0.384 0.378 0.359 0.388 0.377 0.368 0.364 0.373 Cladding Thickness 0.711 0.780 0.738 0.660 0.673 0.686 0.762 0.622 (mm, in.) 0.028 0.031 0.029 0.026 0.027 0.027 0.030 0.024 

Gap Thickness 0.095 0.110 0.085 0.107 0.089 0.095 0.095 (mm, in.) 0.0038 0.0043 0.0033 0.0042 0.0035 0.0038 0.0038 

Fuel Diameter 9.56 9.39 9.68 9.36 9.17 9.05 9.29 (mm, in.) 0.377 0.370 0.381 0.369 0.361 0.356 0.366 Fuel Pellet Length 11.43 10.8 15.24 11.05 10.8 6.93 15.24 (mm, in.) 0.450 0.425 0.600 0.435 0.425 0.273 0.600 

Fuel Rod Length 3.71 3.72 3.86 3.72 3.90 3.20 3.86 3.80 (m, in.) 145.9 146.4 152.0 146.4 153.7 125.9 152.0 149.7 

Active Fuel Length 3.48 3.40 3.66 3.48 3.60 3.66 3.66 3.66 (m, in.) 137 134 144 137 142 144 a 144 144 

Plenum Length 0.218 0.185 0.298 0.160 0.173 0.208 (m, in.) 8.60 7.28 11.70 6.30 6.80 8.20 Average Enrichment 4.1 3.5 3.13 3.46 3.58 2.65 2.92 

atom% 

Fuel Density (% TD) 95.0 94.0 94.0 95.0 95.0 95.0 94.0 95.0 

%TD 

System Pressure 15.5 15.2 13.9 15.5 15.5 (Mpa, psi) 2250 2200 2015 2250 2250 

Helium fill gas pressure 2.07-3.10 2.10 2.10 1.90-2.76 2.86 2.00 He (MPa, psig) 300-450 305 305 275-400 415 1 290 a. All values are from Ref 7 ew'ent • •=.

(cont'd)

A-2

a. All values are from Ref 7 exce t as notec,
Table A2 (cont'd). Non-proprietary PWR Fuel Design Parameters 

Fuel Vendor ABB B&W B&W SNP W 

Array 16x16 17x17 17x17 17x17 17x17 

Version CE Mark C Mark BW W Vantage 5 

Typical Number of Fuel 224 264 264 264 264 

Rods per Assembly 

Pitch (mm, in.) 12.9 12.8 12.6 12.6 12.6 

0.506 0.502 0.496 0.496 0.496 

Cladding OD (mm, in.) 9.70 9.63 9.50 9.14 9.14 

0.382 0.379 0.374 0.360 0.360 

Cladding ID (mm, in.) 8.43 8.41 8.28 7.87 8.00 

0.332 0.331 0.326 0.310 0.315 

Cladding Thickness 0.635 0.610 0.610 0.635 0.572 

(mm, in.) 0.025 0.024 0.024 0.025 0.0225 

Gap Thickness 0.089 0.099 0.083 0.089 0.065 

(mm, in.) 0.0035 0.0039 0.0033 0.0035 0.0026 

Fuel Diameter 8.26 8.21 8.12 7.69 7.85 

(mm, in.) 0.325 0.323 0.320 0.303 0.309 

Fuel Pellet Length 11.43 9.53 10.16 8.84 12.95 

(mm, in. ) 0.450 0.375 0.400 0.348 0.510 

Fuel Rod Length 4.09 3.88 3.85 3.86 3.87 

(m, in.) 161.0 152.7 151.5 152.0 152.3 

Active Fuel Length 3.81 3.63 3.66 3.66 3.66 

(m, in.) 150 143 144 144 144 

Plenum Length 0.254 0.242 0.163 0.184 0.188 

(m, in.) 10.00 9.50 6.40 7.26 7.41 

Average Enrichment 2.45 3.29 3.56 3.84 3.59 

atom% 

Fuel Density (% TD) 95.0 95.0 96.0 94.0 95.0 

%TD 

System Pressure 15.5 15.5 15.5 15.5 

(Mpa, psi) 2250 2250 2250 2250 

Helium fill gas pressure 2.07-3.10 3.00 2.00 He 

(MPa, psig) 300-450 435 290 1 

a. All values are from Ref. 7 except as noted

A-3
NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER 

(2489) (Assigned by NRC, Add Vol., Supp., Rev., 

NRCM 1102B and Addendum Numbers, if any.) F32C1 3202. BIBLIOGRAPHIC DATA SHEET 

3201, 3202 

(See instructions on the reverse) NUREG - 1754 

2. TITLE AND SUBTITLE 

A NEW COMPARATIVE ANALYSIS OF LWR FUEL DESIGNS 3. DATE REPORT PUBLISHED 

MONTH YEAR 

December 2001 

4. FIN OR GRANT NUMBER 

5. AUTHOR(S) 

6. TYPE OF REPORT 

G. M. O'Donnell, H. H. Scott, and R. 0. Meyer 7. PERIOD COVERED (inclusive Dates) 

8. PERFORMING ORGANIZATION - NAME AND ADDRESS (IfNRC, provide Division, Office or Region, U.S. Nuclear Regulatory Commission, and mailing address; if contractor, 

provide name and mailing address.) 

Division of Systems Analysis and Regulatory Effectiveness 

Office of Nuclear Regulatory Research 

U. S. Nuclear Regulatory Commission 

Washington, DC 20555-0001 - Office......... • or R iU NNuclear Regulatory Commission,

9. SPONSORING ORGANIZATION - NAME AND ADDRESS (tf NRC, type 'Same as above"; ir contractor P -. . ... 

and mailing address.)

same as above

10. SUPPLEMENTARY NOTES

11. ABSTRACT (200 words or less) 

In 1980, NRC published a comparative analysis of LWR fuel designs, and that report served as a handy reference for typical 

design and operating parameters for all types of fuel then in operation in U.S. power reactors. During the past twenty years, 

significant changes have been made in fuel designs, bumups, and analytical computer codes. The present report is an update 

of the earlier report. Typical fuel design parameters are tabulated for almost all fuel types in current operation, from BWR 8x8 

bundles to PWR 17x17 assemblies. Cross-section diagrams are given for BWR fuel bundles and PWR fuel assemblies. 

Calculated values are plotted for thirteen operating parameters including fuel centerline temperature, cladding O.D. 

temperature, gap conductance, rod internal gas pressure, and cladding hoop stress. The calculated values are plotted as a 

function of fuel burnup to 65 GWd/t for a variety of power histories, covering a range from low to high linear heat ratings, which 

are constant early in life but decline later in a realistic manner.

12. KEY WORDS/DESCRIPTORS (List words or phrases that will assist researchers in locating the report.) 13 AVAILABILITY STATEMENT 

unlimited 

Computer Code Fuel Rod Design Data 14. SECURITY CLASSIFICATION 

Rod Gas Pressure Fuel Rod Performance (ThisPage) 

unclassified 

Cladding Corrosion Cladding Deformation (This Repoit) 

unclassified 

High Burnup Pellet Centerline Temperature 15. NUMBER OF PAGES 

16. PRICE

NRC FORM 335 (2-89) This form was electronically produce. Dy t.eru,,,• ......
Federal Recycling Program
UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

WASHINGTON, DC 20555-0001 

OFFICIAL BUSINESS 

PENALTY FOR PRIVATE USE, $300