NUCLEAR SAFETY & NUCLEAR THERMAL-HYDRAULICS
In a nuclear reactor, harsh environments present unique and exciting challenges to thermal-hydraulic scientists and engineers for the development, testing, and characterization of current and future reactor systems. Therefore, understanding the physics of thermal-hydraulics in nuclear reactors is key in dictating the safety and efficiency of the nuclear reactor systems. We are exploring high impact emerging thermal-hydraulic issues for improving nuclear power plant energy systems even in accidents.
Nuclear thermal-hydraulics for safer nuclear fuel & cladding development
In reaction to the Fukushima Daiichi accident, efforts are underway by governments and industries to develop fuel cladding that is more oxidation resistant and hence more accident tolerant than the presently used zirconium alloys. The new advanced fuel & cladding is called Accident Tolerant Fuel (ATF). Extensive research is already underway for evaluating these ATF concepts in regards to high temperature oxidation and mechanical behavior, and in-reactor radiation performance. However, as a part of these ATF development efforts, it is important to understand the role of surface characteristics of these ATF cladding materials on heat-transfer behavior. In this regard, the CHF phenomenon is an important metric as it represents the thermal limit of the high heat transfer rates during boiling and is an important figure of merit defining Light Water Reactor (LWR) safety margins. We experimentally investigated boiling characteristics with the unique surface characteristics and thermal properties of ATF cladding materials.
Research reactor design assessment for safety
Nuclear reactors are typically used to generate electricity since it has high energy power density compared with other energy resources. However, some nuclear reactors are designed and used only for research, development, education, and training. In addition, the research reactor could produce neutrons for use in industry, medicine, agriculture, and forensics, among others. Due to the different purposes of the reactors, detail designs in research reactors are different compared with commercial reactors (e.g., APR 600, OPR 1000 or APR 1400), and it requires safety assessment for the new designs used in a new research reactor. We are proudly supporting the assessment process of new research reactor designs proposed by KAERI (Korea Atomic Energy Research Institute).
Cooling channel development for divertors used in nuclear fusion reactors
Nuclear fusion energy is one of promising future energy sources, and the divertor is a heat sink component of the fusion reactors. (The purpose of the divertor is not only for removing heat from the reactor but also for removing the impurities by plasma fusion reaction.) The divertor is heated by plasma only on the top side, resulting in one-side heating but should transfer about 10 MW/m2 in steady-state which is much larger than the current nuclear power plant capacity (about 1 MW/m2). Such high heat flux conditions in nuclear fusion reactors are unique and difficult challenges in terms of heat transfer. We are trying to propose and verify a new design of the cooling channel handling the issue of the divertor design in nuclear fusion reactors.