The PEMFC (polymer electrolyte membrane fuel cell) is a kinds of electro – chemical system to exchange chemical potential energy of gases, especially hydrogen and oxygen, to electrical energy. The system always makes water as a reactant of gases or condensation of slow humidity of gases. Hydrogen gas is diffused from channel to gas diffusion layer. And when it touches the anode catalyst layer, then hydrogen is ionized and generate electron. Membrane has high proton conductivity but low electrical conductivity. So …

The big issue of S-CO2 Brayton cycle is to develop compact heat exchanger which is comparable to the size of turbines and compressors. One of the candidates of this compact heat exchanger is printed circuit heat exchanger (PCHE). PCHE is manufactured by chemical etching and diffusion bonding technologies (Fig. 14). Using these two technologies, PCHE has many micro-scale channels and durability to high pressure and temperature. Further, it has larger heat transfer area per volume than other conventional heat exchan…

The sodium–water reaction (SWR) is a serious impediment to development of sodium fast cooled nuclear reactor (SFR), especially at sodium water heat exchanger  

The final goal of MCCI prevent interaction of corium and concrete. In addition to this, we have to eliminate decay heat and secure corium coolability. But it hardly prevents MCCI phenomena. Nuclear engineer research a way which obtain coolability and delay molten corium –concrete interaction like core catcher system. MCCI accompanies many gases such as H2, CO2, CO, H2O and concrete ablation. Therefore, we focus on the how to act non condensable gases and what parameters govern concrete ablation such as temperature, de…

  In case of severe accident when core melt is ejected from vessel, external core catcher has been considered in APR1400 reactor. Two-phasenatural circulation basedcore catcher cooling system removes decay heat of corium to increases the reliability and safety. KAERI (Korea Atomic Energy Research Institute) have developed core catcher concept which operates as a passive system. As coolant flows through single channel below the core catcher plate, bubbles are generated due to decay heat and a two-phase flow is est…

  In the late phase of severe accident in nuclear power plants, it is important to assure the coolability of the relocated corium in the reactor cavity. Under this circumstance, concrete ablation and over-pressurization caused by molten core concrete interaction (MCCI) may threaten the integrity of containment, the final barrier of the defense-in-depth, to prevent the release of radioactive material to environment. To ensure the long-term cooling of corium in the reactor cavity, it is important to ensure the …

Cooling of ex-vessel corium mixture is one of the most important issues of the severe accident for preventing the accident progress and mitigating the accident result. To avoid MCCI and secure the safety from the threat of radioactive material release to environment, the coolability of ex-vessel corium should be sufficiently secured. In the flooded cavity with coolant water, there must be FCI, and following fragmentation of the discharged melt jet. For massive discharge of melt during very short time, there must be co…

  Steam explosion is one of the risk significant phenomena at the severe accident. It often occurs if hot liquid material comes into contact with cold coolant and the coolant boils at a local area of hot liquid-coolant interaction producing rapid vapor generation. The steam explosion is developed following four steps: premixing, triggering, propagation, and expansion. 

In severe accident, the ex-vessel corium coolability is one of risk-significant issues and there are still significant uncertainties in the coolability in terms of the debris bed characteristics even in the case the cavity flooding system is utilized. The coolability of debris particle bed which is important because of the possibility of molten core concrete interaction is related with debris size, distribution and so on. These components depend on the earlier phase such as melt-jet injection, break up, fragmentat…

In-Vessel Retention by External Reactor Vessel Cooling (IVR-ERVC) is one of the severe accident management strategies to terminate or mitigate the severe accident (SA) which is also called ‘core-melt accident’. The reactor vessel which is containing molten core material in the lower head is cooled by flooding coolant. The molten core mixture is expected to be divided into some layers due to the density difference. Fig.2 shows the conventional two layered configuration of IVR. It has light metal layer of Fe-Zr and …

Research reactors are nuclear reactors which were developed for neutron based research industry rather than for power generation. Water in the reactor pool acts as the moderator, reflector, and shielding barrier to radioactivity from the nuclear reactor fuel rods. Moreover, the coolant in the reactor pool provides the ultimate heat sink during accidents in which the pump of primary cooling system stops working. The quantity of coolant is strongly related to the length of time for which safety can be maintained between…

Condensation phenomenon occurs when vapor is subcooled below the saturation temperature at given pressure. And condensation is a phase change phenomenon which is very efficient heat transfer using latent heat. Many industries use condensation heat exchanger, namely condenser. Thus, it is important to study the condensation heat transfer characteristics in various conditions and find the way to enhance the condensation heat transfer performance 

We used the basic two experimental methods to understand the Film Boiling Heat Transfer; quenching and leidenfrost experiment. The major points able to achieve are below, 1) Efficient core-cooling strategy under the severe accident of nuclear power plant 2) Phenomenological investigation during phase-change on the modulated heat transfer surface under high temperature condition 3) Development of technical methodology to identify the phase-change motion at th…

The flow boiling, which has heat transfer with flow, is the one of the phase change phenomena but not well understood due to the complexity. In many industries including power plants, flow boiling is the core technology in heat transfer because it is an efficient method in comparison to other techniques. Specially, flow boiling is more complex than pool boiling, so flow regime is one of the means to divide physical phenomena for understanding 

As one of a key phenomenon in thermal hydraulics system, nucleate boiling has been widely studied by numerous researchers to improve efficiency and safety of the system (i.e, nuclear power plant, refrigerating system etc.). In general, the evaluation of the boiling performance mainly focus on two physical parameters: boiling heat transfer (BHT) and critical heat flux (CHF). Since both BHT and CHF contribute the thermal system efficiency and safety, respectively many new approaches to enhance the boiling performance co…