Four monolithic refractory ceramics (Al2O3, SiC, TiC and TiN) were exposed to severe thermal shock caused by thermite reaction. Such experiments were intended to simulate the exposure of a core catcher to hot debris of melted core in nuclear reactor. Moreover, the chemical interactions between tested materials and products of thermite reaction were investigated by holding samples in laboratory furnace for 5 hours at 1000oC in air. None of the materials entirely withstand such sudden temperature rise, o...
英字タイトル:
Molten Core Concrete Interaction and Development of Core Catcher (2) Thermal shock effects for advanced high temperature ceramics

During the Fukushima Daiichi Nuclear Power Plant accident, fuels in the each core in units 1, 3 and 2 melted, and the melted core might dropped down into the lower plenum of the RPV. The core debris heated the bottom structure of reactor vessels and dropped down onto the pedestal through the melted pass of the vessel bottom structure. High temperature core debris might attack concrete or PCV bottom. In order to protect core concrete reaction, several types of core catchers were developed, but they are...
英字タイトル:
Study on Compact-Type Core Catcher for Current Nuclear Power Plants

This paper describes how to write a manuscript of the 18th PES Proceedings. In the Fukushima Daiichi Nuclear Power Plant accident, a great deal of radioactive material was released to surrounding environment. After the accident, the Filtered Containment Venting System (FCVS) that can remove radioactive material from steam in containment vessel has attracted a great deal of attentions. However, there is few knowledge of filtered vent in Japan because almost filtered vent were developed in Europe after ...
英字タイトル:
Research related to Filtered Venting System

A concept of a plutonium burner HTGR (High Temperature Gas-cooled Reactor) with a high nuclear proliferation resistance has been proposed by Japan Atomic Energy Agency. In addition to the high nuclear proliferation resistance, in order to attain the high burn-up, we propose to introduce a PuO2-YSZ (Yttria Stabilized Zirconia) fuel kernel with ZrC coating to the plutonium burner HTGR. In this study, we conduct design of the coated fuel particle and of the reactor core to confirm the feasibility of the plut...
英字タイトル:
Design Study on Fuel and Reactor Core for Plutonium Burner High Temperature Gas-cooled Reactor

Secondary system piping was ruptured at Mihama Nuclear Power Station Unit 3 of Kansai Electric Power Company in August 2004, and 11 workers were injured and killed. The operators of PWRs in Japan established and implemented the guidelines for wearing management procedure about secondary system piping. In this study, the management system of Japan and foreign countries were compared, and the validity of the domesti c wearing management technique was examined. Consequently, it was acknowledged a great diffe...
英字タイトル:
Japan-U.S. Comparison of Management System of Secondary System Piping Wearing

There are various leak phenomena in nuclear power plants, such as thermal or vibration fatigue crack, grand of valve, valve sheet, mechanical seal and SG tubes, and so on. In the current power plant, engineers should find such probl ems by annual inspection. But, in case of severe accident, operators should conduct a prompt action without mistake. It is very difficult to do such action with limited information and AM tools. Therefore, authors have conducted to develop online leak rate evaluation method for...
英字タイトル:
Development of Online Leak Rate Evaluation Method for Various Leak Phenomena in NPPs

Various leak events have happened in nuclear power plants so far. And plants have bad conditions because of these leakages. Several leak events must be investigated, and we have to prepare these leakages. Like this, systematizing evaluation s of several leak events brings upgrades in regulations or new system of inspections, plans for aging deterioration. By using this method, we know deeper about Fukushima-Daiichi NPP. For example, here, from changes of CV pressure, we can conclude that SB-LOCA was NO...
英字タイトル:
Studies about Development of Leak Event Evaluation Method in Nuclear Power Plant

By using the FCVS technology, we had started to develop a high decontamination air cleaning system to remove multi-nuclides for radiation protection to conduct decommissioning the Fukushima NPP (Fig. 17). Development of high efficiency multi-nuclide aerosol filters for radiation protection during a process of cutting core debris at Hokkaido University. A plasma cutter, laser cutter, wire cutter, drilling machine, etc., will be used and will generate aerosols. Therefore, the air cleaning system should be...
英字タイトル:
Development of a high efficiency multi-nuclide aerosol filters for radiation protection during a process of cutting core debris (1) Plan of this project

By using the FCVS technology, we had started to develop a high decontamination air cleaning system to remove multi-nuclides for radiation protection to conduct decommissioning the Fukushima NPP. High efficiency multi-nuclide aerosol filters for radiation protection during a process of cutting core debris has been developing at Hokkaido University. A plasma cutter, laser cutter, wire cutter, drilling machine, etc., will be used and will generate aerosols. Therefore, the air cleaning system should be neede...
英字タイトル:
Development of a high efficiency multi-nuclide aerosol filters for radiation protection during a process of cutting core debris (2) Measurement of DF for Metal Fiber Filter

Japan, as a frequent earthquake country, has a responsibility to resolve efficient measures to enhance nuclear safety, to continue utilizing the nuclear power, based on the risks and importance levels in the scientific and rational manner. In his paper describes how to evaluate the risk of faults movement by engineering approach. An open fruitful discussion by experts in the various areas of earthquake, geology, geotechnical, civil, and a seismic design as well as other stakeholders such as academia prof...
英字タイトル:
Risk Evaluation Method for Faults by Engineering Approach (1) Nuclear safety for accident scenario and measures for fault movement