Radioactive iodine is one of the major constituents among fission products released into the environment from damaged containment at nuclear power plant (NPP) during severe core melt accidents such as Chernobyl and Fukushima as well asnuclear fuel reprocessing. Released radioactive iodine from nuclear reactor and nuclear severe accidents is one of the most hazardous radioactive contaminants and can create significant effect to human health. Several radioactive iodines such as I-131,I-135, I-125, a…

Cs+ captured fly ash filter waste from pyro-processing was immobilized by alumino-borosilicate glass waste form. Produced glass specimens were irradiated by electrons in order to simulate the beta irradiation during the storage and disposal. Density, glass transition temperature, Vickers hardness and linear thermal expansion coefficient of pristine and irradiated glasses were measured. All of measured glass properties were similar to that of commercial HLW glass waste forms.&n…

 A new alkali-alumino tellurite glass composition was developed to immobilize highly-volatile technetium (Tc) wastes generated from the pyrochemical processing technology. Tellurite glass can incorporate up to 7 mass% of rhenium (Re, used as a surrogate for Tc) with an average retention of 86%. Normalized elemental releases evaluated by seven-day product consistency test (PCT) satisfied the immobilized low activity waste requirements of United States when concentration of Ca(ReO4)2 in the glass was < 12 m…

Silver tellurite glasses with melting temperatures < 700 °C were prepared to immobilize the 129I that normally volatilizes during high-temperature melting. Glasses have densities of 6.31 ± 0.1 g/cm3 and transition temperatures of 165 ± 3 °C that provide thermal stability at the disposal site. Iodine waste loading in glasses was as high as 12.64 wt.% of all metallic elements and 11.21 wt.% including oxygen. Normalized elemental releases obtained from the product consistency test were well below US regulation of 2 g/…

Glass-ceramic wasteforms containing calcium neodymium(cerium) oxide silicate [Ca2Nd8 - xCex(SiO4)6O2] were synthesized to immobilize lanthanide oxide wastes generated from pyro-processing. 1. These Caesilicate crystals (~100 mm in size) were formed from alkali borosilicate glasses by heat-treating at 750 C for 3 h. Ce and Nd ions were partitioned inside the Caesilicate crystalline phases, constituting ~44 wt.% of the crystals. 2. Maximum leaching of these ions in the glasses was >26.8 wt.%. The normalize…

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 …