Comparison of Water, Helium, and Carbon Dioxide as Coolants for Next Generation Power Plants using TRACE
Open Access
- Author:
- Garrett, Grant Robert
- Graduate Program:
- Nuclear Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- April 02, 2018
- Committee Members:
- Justin Kyle Watson, Thesis Advisor/Co-Advisor
- Keywords:
- Generation IV Reactors
Water
Helium
Carbon Dioxide
Thermal-Hydraulic Simulation
TRACE
SNAP
Fusion Reactors - Abstract:
- The purpose of this study is to compare the use of water, helium, and carbon dioxide as coolants for Generation IV and fusion power plants. The Symbolic Nuclear Analysis Package (SNAP) was used to create input files for the TRAC/RELAP Advanced Computational Engine (TRACE) thermal hydraulics and neutronics coupled code representing this phenomenon. In addition, TRACE was used to perform simulations comparing how Helium, Carbon Dioxide, and water perform as coolants for power plant systems. To start, a TRACE model was built for each coolant of this study that represented a 600 $MW_{th}$ fusion Field Reversed Configuration (FRC) power plant. The vessel and power source were the same for each model of this study. The TRACE models include all components of the primary side of a Rankin cycle power plant, including pumps, heat exchangers, a reactor vessel, pipes, coolant channels, etc. The reactor vessel in the TRACE models represented a hollow cylinder at vacuum with a fusion FRC power source inside this hollow cylinder. The materials that comprised the cylinder wall were chosen based on thermal conductivity, attenuation coefficients, and other factors. Part of the cylinder wall was coolant channels with the coolant flowing through it. Besides flow through the steam generators, most of the secondary side components were represented by a control system that calculated the turbine output work. Once the model for each coolant was built, simulations were performed to ensure the models reached steady state. After the models prove to reach steady state, parameters were changed to optimize the performance of the systems for each coolant based on the various system requirements. The final water cooled model operated at similar conditions to those of a PWR. The final helium and carbon dioxide cooled models operated at conditions based on AGRs, GFRs, and other similar gas cooled systems. Simulations were performed, and the results were used to analyze how each coolant performs for the power system analyzed in this study. Before performing analysis based on the TRACE predicted results, verification was performed for helium and carbon dioxide in TRACE because TRACE is only verified and validated with water as the fluid in simulations. To ensure the results from the helium cooled and carbon dioxide cooled TRACE models were reliable, the method of manufactured solutions was used to perform verification for various test cases. The TRACE results were compared to hand calculated results for identical test cases. The verification process determined the TRACE predicted results from the helium and carbon dioxide models were reliable for the range of conditions of each respective model. Further verification and validation can be performed for helium and carbon dioxide as fluids in TRACE models and simulations. After performing the tasks mentioned in the previous paragraphs, analysis was performed based on the TRACE predicted results for each coolant. Based on the system requirements and the results from the TRACE simulations, it was determined that water was the best coolant for the system analyzed in this study. For the operating conditions used in this research, water was able to keep the temperature of certain materials below their maximum temperatures much easier than the helium and carbon dioxide cooled systems. Specifically, beryllium was used as a material in the system and was determined to have a maximum temperature of 800\textdegree C for its applications in this study. Additionally, this temperature limit restricts the efficiency and capabilities of the helium and carbon dioxide cooled systems. There is also uncertainty associated with the turbine efficiencies used in this study. This introduces uncertainty into the overall efficiency of the system for each coolant. So, the overall efficiency is not as important of a parameter in determining the best coolant for the system in this study as other parameters. Theoretically, the helium and carbon dioxide cooled systems should have a higher efficiency than the water cooled model. Modifications that could be made to the system of this study and their resulting potential impacts are considered and analyzed.