DEVELOPMENT AND INTEGRATION OF FUEL ROD GAS GAP CONDUCTANCE MODEL IN CTF AS A FUNCTION OF REACTOR POWER AND BURNUP
Open Access
- Author:
- Raja, Faisal Z.
- Graduate Program:
- Nuclear Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- September 17, 2016
- Committee Members:
- Dr. Maria Avramova, Dissertation Advisor/Co-Advisor
Dr. Maria Avramova, Committee Chair/Co-Chair
Dr. Kostadin Ivanov, Committee Member
Dr. Jack S. Brenizer, Committee Member
Dr. John M. Regan, Outside Member - Keywords:
- COBRA-TF
CTF
FRAPCON
BISON
GAP CONDUCTANCE
REACTOR POWER
FUEL BURNUP
FUEL EXPOSURE
NUCLEAR
FUEL ROD
SUBCHANNEL CODE
FUEL CENTERLINE TEMPERATURE
FUEL SURFACE TEMPERATURE
UO2
ZIRC4
ZIRC CLADDING
LIGHT WATER REACTOR - Abstract:
- Having the ability to predict fuel temperatures for efficient multi-physics depletion and transient calculations with reasonable accuracy without the added burden of prohibitively expensive computation costs has been a major driving force in the nuclear industry. One of the parameters that has an immense impact on fuel surface and fuel centerline temperatures is the nuclear fuel gas gap conductance. This study addresses the issue of fuel rod gas gap conductance prediction by utilizing the subchannel thermal-hydraulics code CTF, which is a modified version of the legacy code COBRA-TF (Coolant Boiling in Rod Array – Two Fluid), to predict fuel rod temperatures with the help of a new gas gap conductance model that leverages the fuel performance code FRAPCON. Gas gap conductance data was pre-computed as a function of linear heat rate and fuel exposure and was integrated into CTF as part of the new model. Using FRAPCON as a reference solution, the new FRAPCON-informed gap conductance model of CTF was found to be within 2 Kelvin of FRAPCON with respect to fuel surface temperature. In addition to the inclusion of gas gap conductance model as a function of power and exposure, a comparative analysis was performed using CTF, and higher-fidelity fuel performance codes FRAPCON and BISON. The purpose of these analyses was to ascertain the predictive accuracy of the stand-alone fuel performance model in CTF, and then to use this model to integrate a FRAPCON-informed gas gap conductance model in CTF. For the comparative analysis, gap conductance and internal pin power distributions were provided by BISON and FRAPCON for CTF simulations. Excellent agreement was found between CTF and FRAPCON, and between CTF and BISON with respect to clad inside, fuel pellet surface, and fuel centerline temperatures when the gap conductance values were set by either FRAPCON or BISON. This study certainly does not undermine high-fidelity standalone fuel performance codes and their place in the industry, rather it provides an insight into a practical and lucrative alternative in the form of a subchannel code.