june 8 demo thermal analysis hanson

1. Used Fuel Disposition Campaign
Thermal Analysis of High Burnup Spent Fuel
Data Project Research Project Cask
Brady Hanson, Lab Lead Experiments
Harold Adkins, Jim Fort, Judith Cuta, Sarah Suffield
Pacific Northwest National Laboratory
UFD Working Group Meeting
June 8, 2016
Las Vegas, NV
PNNL-SA-XXXXX

2. Used
Fuel
Disposition
North Anna Site Specific License
TN-32
 North Anna ISFS Final
Safety Analysis Report
– 32 PWR fuel assemblies
– 32.7 kW maximum total decay
heat load (1.02 kW per
assembly)
– Ambient temperature
• -30°F to 115°F
• Max daily average 100°F
– Peak Cladding Temperature
(PCT) storage = 296°C
(595°F)
– Vacuum drying limited to <36
hours to provide assurance
PCT < 400°C 2

3. Used
Fuel
Disposition
COBRA-SFS
 Validated against numerous
– Single assembly (electrically
heated) tests
– Multi-assembly tests with spent
fuel
 Accepted by NRC
 Detailed fuel and basket
region models
 Radiation, convection, and
conduction heat transfer
 Dimensions, materials, and
properties from UFSAR
(2012) provided under non-
disclosure agreement with
AREVA TN
3
Rod-and-Subchannel Array Diagram for
COBRA-SFS Model of 17x17 Fuel Assembly
within Basket Cells of TN-32B (Note: diagram is
not to scale)

4. Used
Fuel
Disposition
STAR-CCM+
 Computational Fluid
Dynamics code
 Model basket and cask body
in detail
 Approximate backfill gas and
fuel assemblies as a porous
media
– Homogenized over the active
fuel length
 Effective thermal
conductivity model to
calculate cladding
temperatures
– No recirculation so porous media
loss coefficients not needed
4

5. Used
Fuel
Disposition
Research Project Cask
Initial Loading Scenarios (31.5 kW)
 Many conservatisms remain
 Assumptions:
– Generic axial decay heat profile
– WE 17x17 LoPar and V5H
assembly information
– Boundary conditions
 Decision made to replace 8
assemblies in middle ring
with short-cooled assemblies
to increase PCT
5
 PCT
– Storage
• 261°C COBRA-SFS
• 263°C STAR-CCM+
• 296°C (32.7 kW) UFSAR
– Drying
• 299°C steady state COBRA-SFS
• <400°C (32.7 kW) UFSAR

6. Used
Fuel
Disposition
Cladding Storage Temperatures
COBRA-SFS (36.8 kW)
6
Peak Cladding Temperature (°C)
Minimum Cladding Temperature (°C)

7. Used
Fuel
Disposition
PCT Storage Temperatures
STAR-CCM+ (36.8 kW)
7

8. Used
Fuel
Disposition
PCT Under Transient Drying
COBRA-SFS (36.8 kW)
 337°C PCT (drying steady state) compares to ~350°C
calculated in LAR 8

9. Used
Fuel
Disposition
Best Estimate
Cladding Storage Temperatures
COBRA-SFS (30.6 kW)
9
Peak Cladding Temperature (°C)
Minimum Cladding Temperature (°C)
Modifications:
ORIGEN vs conservative/regulator practice decay heats.
~17% total reduction in decay heat at loading.
Actual decay heat profiles
Proper assembly design parameters

10. Used
Fuel
Disposition
Temperature Variability Within an
Assembly
10

11. Used
Fuel
Disposition
Temperature Variability in Instrumented
Assemblies
11

12. Used
Fuel
Disposition
Cladding Temperature Distribution
COBRA-SFS (30.6 kW)
12

13. Used
Fuel
Disposition
Best Estimate
PCT Storage Temperatures
STAR-CCM+ (30.6 kW)
13Differences between COBRA-SFS and STAR-CCM+
model estimates of assembly PCTs (°C)
Assembly PCTs (°C)

14. Used
Fuel
Disposition
System Temperatures
COBRA-SFS (30.6 kW)
14

15. Used
Fuel
Disposition
PCT Under Transient Drying
COBRA-SFS (30.6 kW)
15

16. Used
Fuel
Disposition
Cladding Temperatures After 10 Years
COBRA-SFS
16
Peak Clad Temperature (°C)
Minimum Clad Temperature (°C)

17. Used
Fuel
Disposition
Temperature Distributions in Hottest
Assembly at Loading and 10 Years
17

18. Used
Fuel
Disposition
Why Does Temperature Matter?
Hydride dissolution (heating) and
precipitation (cooling) curves
18

19. Used
Fuel
Disposition
FRAPCON Hoop Stress Estimates
19
Rod Design BOL Fill Pressure (MPa)
EOL Hoop Stress (MPa)
@570°C PCT
No oxidation
@570°C PCT
40 µm oxidation
@350°C PCT
40 µm oxidation
B&W
15×15
3.31 89.4 92.8 68.7
Westinghouse
15×15
3.31 98.6 102.8 76.1
Westinghouse
15×15
2.48 79.5 82.9 61.4
CE
14×14
2.63 77.2 80.0 59.3
Westinghouse
14×14
2.63 70.5 73.3 54.3
Westinghouse
17×17 IFBA
(natural boron)
NA NA 112 83
Westinghouse
17×17 IFBA
(enriched boron)
NA NA <126 <93
BOL = beginning of life, EOL = end of life, IFBA = integral fuel burnable absorber, PCT = peak cladding temperature