Critical Heat Flux Model Improvement in CTF for Natural Circulation Type Reactors
Open Access
- Author:
- Jernigan, Caleb S
- Graduate Program:
- Nuclear Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- None
- Committee Members:
- Maria Nikolova Avramova, Thesis Advisor/Co-Advisor
- Keywords:
- SMR-160
CTF
CHF
Bowring
Groeneveld
EPRI-1
W3
Biasi
DNB - Abstract:
- The objective of this study was to enhance the capabilities of the subchannel thermal-hydraulics analysis code CTF for modeling critical heat flux (CHF) conditions within natural circulation type of nuclear reactors such as the Holtec small modular reactor SMR-160. The SMR-160 is a pressurized water reactor (PWR) characterized by core coolant flow driven by natural circulation at relatively low mass flow rates and high inlet subcooling as in compared to a typical PWR. Identifying a CHF model appropriate for these conditions is required for an accurate thermal-hydraulics performance analysis. Several CHF models available in the open literature, including those already implemented in CTF, were studied for their applicability to SMR-160. This includes the CHF models by Westinghouse (W-3), Electric Power Research Institute (EPRI-1), Biasi, Bowring, and Groeneveld. Since the models were developed within a certain validity range of operating conditions (mass flow rate, equilibrium quality, pressure, hydraulic diameter, and others), these ranges were used as a measure of acceptability when compared to the standard or expected SMR-160 operating conditions. It was found that the existing CHF models in CTF, excluding the models by Bowring and Groeneveld, were not fully applicable to the unique SMR-160 rated conditions. Therefore, the models by Bowring and Groeneveld were selected for SMR-160 safety analysis. The Bowring model consists of a set of empirical equations. The Groeneveld model is in the form of a 15×21×23 multi-dimensional table of CHF values discretized in pressure, mass flux and equilibrium quality, along with several “K” factors adjusting for additional physical affects. These two models were implemented in CTF for CHF and DNB calculations of SMR-160.