1. KAIST Hee Cheon NO Nuclear System/Hydrogen Lab.
Chapter 3: Fuel Thermal Analysis
Hee Cheon NO
Nuclear System/Hydrogen Lab.
KAIST

2. Contents 3.1 Basic heat transport modes
3.1.1 conduction heat transport
3.1.2 convective heat transport
3.1.3 radiation heat transport
3.2 Fuel irradiation effects
3.2.1 Fission gas release
3.2.2 Thermal expansion, densification, swelling
3.2.3 Clad creepdown and lift-off
3.2.4 Fuel-cladding interaction
3.2.5 Fuel failure mechanisms
3.3 Fuel thermal analysis
3.3.1 Fuel pellet thermal analysis
3.3.2 Fuel cladding thermal analysis
3.3.3 Fuel gas gap thermal analysis
3.3.4 Heat transfer in the fluid channel

3. 3.1 Basic heat transport models
Conduction heat transport

4. 3.1 Basic heat transport models
Convection heat transport
heat transfer coefficient

5. 3.1 Basic heat transport models
Radiation heat transport
Black medium: emissivility=1; perfect emiiter and absorber
Grey medium(practical medium): emissivility<1

6. 3.2 Fuel irradiation effects

7. 3.2 Fuel irradiation effects
Fission gas release: recoil & knockout

8. 3.2 Fuel irradiation effects
open tunnel network
Fission gas release: diffusion mechanism

9. 3.2 Fuel irradiation effects
Fission gas release: grain size effect

10. 3.2 Fuel irradiation effects
Thermal expansion

11. 3.2 Fuel irradiation effects
Densification and swelling

12. 3.2 Fuel irradiation effects
Clad creepdown and lift-off
creep: long-term transient deformation given load

13. 3.2 Fuel irradiation effects
Fuel-cladding interaction

14. 3.2 Fuel irradiation effects
Fuel failure mechanism

15. 3.2 Fuel irradiation effects
Fuel failure mechanism

16. 3.3 Fuel thermal analysis
Example of fuel temperature radial distribution in fuel pellet

17. 3.3 Fuel thermal analysis Fuel thermal analysis
Fouling is the accumulation of unwanted material on solid surfaces to the detriment of function. The fouling material can consist of either living organisms (biofouling) or a non-living substance (inorganic or organic). Other terms used in the literature to describe fouling include: deposit formation, encrustation, crudding, deposition, scaling, scale formation, slagging, and sludge formation.

18. 3.3 Fuel thermal analysis Fuel pellet thermal analysis:
Fuel cladding thermal analysis:

19. 3.3 Fuel thermal analysis
Fuel gas gap thermal analysis(open gap):

20. 3.3 Fuel thermal analysis Fuel gas gap thermal analysis(closed gap):
Meyer's hardness: H=force/contact area=mean contact pressure normal to surface of the indent;
contact area~1/load; high Meyer's hardness means less plastic deformation which increases contact area;p/H~contact area

21. 3.3 Fuel thermal analysis
coolant T with cosine power profile:

22. 3.3 Fuel thermal analysis cladding T for subcooled non-boiling
cladding T for subcooled boiling: Jens-Lottes correlation

23. CHF concept
3.3 Fuel thermal analysis

24. CHF correlation(W-3)
3.3 Fuel thermal analysis

25. HW#3: Chapter 3: Probelms 4, 5