Nuclear Thermal Hydraulics
Nuclear Thermal Hydraulics
Pebble-Bed Advanced High Temperature Reactor
In 2002 UC Berkeley, ORNL, and SNL proposed that liquid fluoride salts could be used instead of helium as heat transfer fluids for high-temperature reactors. These are commonly referred to as Advanced High Temperature Reactors (AHTRs). Subsequent research at UC Berkeley and elsewhere has demonstrated that salt-cooled reactors can have substantial advantages for the production of low-cost electricity, process heat, and desalinated water, due to their capability to operate at high power density (20 to 30 MW/m^3), low pressure (atmospheric), and deliver heat at high average temperature (650°C) using currently available ASME code qualified materials. Subsequent work at U.C. Berkeley has demonstrated the practicality of this technology, including the capability to circulate pebble fuels, to obtain negative coolant void and temperature reactivity feedback, to convert thermal power to electricity using multi-reheat helium Brayton cycles or supercritical CO2 cycles, to develop and validate experimental thermal hydraulics models for transients such as Loss of Heat Sink, and to develop integrated plant designs including structural and seismic engineering. Current work at UC Berkeley involves separate effect and integral effect test experiments using simulant fluids, model development, simulation, and system design.
Research Sponsors: DOE, ORNL
Advanced Power Conversion and Process Heat Applications
Current light water reactor technology has low power conversion efficiency in the range of 32 to 35%, and requires large and high-quality heat sinks, typically involving direct cooling from rivers, lakes, or the ocean, or large cooling towers. A major goal of advanced reactor research is to achieve higher average coolant temperatures, enabling higher power conversion efficiency, reduced and simplified cooling requirements, and the capacity to co-generate additional products including process heat and desalinated water. UCB performs research in a range of relevant areas, including applications of liquid-salts for high-temperature heat transport, advanced metallic and ceramic heat exchanger design and optimization, multiple-reheat closed gas Brayton cycle power conversion, open air gas Brayton power conversion, tritium control, and advanced multi-effect distillation for sea-water desalination.
Research Sponsors: DOE, ORNL
Technology Neutral Licensing for Advanced Nuclear Energy Systems
 |
Traditional approaches to licensing of nuclear reactors have been deterministic and prescriptive, and thus have limited the ability of reactor designers and vendors to introduce new fuels, coolants, materials, and safety and security system designs. Beginning in the late 1980's, researchers in thermal hydraulics began developing non-deterministic, best-estimate safety evaluation methods which provided the foundation for the licensing of new passive safety systems in the AP-600/1000 and SBWR/ESBWR reactor designs. More broadly, substantive efforts are now being devoted to develop technology neutral licensing frameworks for new reactor technologies, such as Small Modular Reactors. Technology neutral licensing is an area where the U.S. has clear technical leadership, with the U.S. Nuclear Regulatory Commission being the only national regulatory authority having a demonstrated capability to license new reactor designs using passive safety systems. UCB works extensively across several areas of technology neutral licensing and performance based design, including methods for Phenomena Identification and Ranking, Code Scaling and Applicability Analysis, and design and scaling of separate effect test and integral effect test experiments..
Research Sponsors: DOE, LBNL
Integration of Passive Safety Systems with Modular Construction and Seismic Base Isolation Systems
The Nuclear Engineering department collaborates with the Department of Civil and Environmental Engineering studying methods for modular construction and seismic base isolation for nuclear reactors and other nuclear facilities. Advanced modular construction technologies, particularly the use of steel/concrete composite structures, makes it possible to move almost all high-tolerance, high-quality fabrication activities for new nuclear plants into a controlled factory setting, reducing and changing the role of site-work to be increasingly focused on simpler assembly activities. The application of seismic base isolation technology provides further opportunities to reduce and simplify equipment seismic qualification requirements and expand and simplify reactor siting options. Because the passive safety systems in the most modern reactor designs require close integration with the reactor building structures, early collaboration between reactor designers and structural engineers offers significant promise to improve reactor safety and security and to reduce construction costs and schedules significantly.
Research Sponsors: DOE, LBNL
Integration of Safety and Reliability with Physical Security and IAEA Safeguards
Modern nuclear reactor and fuel cycle facilities should be designed with a holistic approach to achieve performance requirements for reliability, safety, security, and IAEA safeguards. Achieving these requirements by synergistic methods, where the approach improves performance in all of these areas, is preferred to methods that involve conflicts between these requirements and the necessity to balance these conflicts. In all of these areas--reliability, safety, security, and safeguards--the fundamental requirements involve maintaining knowledge and control of the locations of radioactive materials under a wide variety of different events that can challenge a facility. A major focus in design is on passive safety and remote handling systems, which can achieve performance requirements while avoiding many of the potential conflicts between safety and security. Research in these areas promises to provide better approaches to meeting reliabilty, safety, security and safeguards performance requirement more robustly and at lower cost..
Research Sponsors: DOE, KAERI
