Since the end of the Cold-War Regime in the beginning of nineties, the torrent of globalization forced each nation to make their system compatible with the global standard.Engineering education is not outside of this stream.Japan needs extra effort to cope with this demand, since our systems are out of global standard in many aspects.Two major problems we face, are the establishment of professional engineer qualification and the introduction of accreditation system of engineering education.Current movement for the establishment of Japan Accreditation Board for Engineering Education (JABEE) is explained.
Current status of research on geological disposal of radioactive wastes is described briefly, mainly focused on fluid flow and mass transport phenomena such as nuclide migration in geological media, colloid transportation, hydro-thermal-mechanical coupled process, moisture migration through clay, bentonite extrusion and erosion, long-term rock creep deformation.
Radioactive aerosols produced by cutting components and structures may cause internal exposures of workers and secondary contamination in dismantling nuclear facilities.It must be important for safety to understand the diffusion behaviors of aerosols in dismantling activities under various working conditions. Therefore diffusion behaviors of aerosols have been studied by experiments such as flow visualization and by numerical analyses based on the fluid dynamics.The results were compared with those obtained in the analyses.As a result, it was confirmed that the diffusion behaviors of aerosols in in-air plasma arc cutting can be simulated by numerical analyses.
Although nuclear power is one of the indispensable energy sources to support modern life styles in developed countries, it becomes harder and harder to increase its capacity.Newspaper reported that there are numbers of evidences showing the suppression effect on cancer by the low level of radiation.It is expected for public people that the fear for radiation induced harm on health will mitigate through the explanation based on scientific evidences.Safe management of radioactive waste is one of the most serious issues to be solved.The neutron at fast reactors can eat more effectively the long lived several nuclear waste materials from light water reactor system.The key issue is to develop the fast reactor fuel cycle system technologies that are more economical, more proliferation resistant and higher breeding ratio.The Metallic Fuel Cycle is one of the options for the future fast breeder reactor and its related fuel cycle that enable to give the answer for the radioactive waste issues.The attractiveness of the metallic fuel cycle concept is briefly described.
Hydrates have peculiar crystal structure that one guest molecule is surrounded with a cage composed by water molecules.These water molecules are connected by hydrogen bonding each other, but there is no chemical bonding between the guest molecule and the water molecules.In this short monograph I will mention the possibility of hydrate's application to solve environmental problems.The cage-like structure of hydrates can be utilized as an environmental pollutant gas separation method since in mixture hydrates the mole fraction of components in a hydrate phase is different from that in a gas phase.The outline and principle of this technique is considered to be similar to the separation technology using phase equilibrium.Thus firstly the separation technology using phase equilibrium is briefed, then properties of hydrates concerning with the separation technology are summarized concisely.After that the separation technology with hydrates is introduced.
It is expected that pure and high performance materials could be manufactured in space under the micro-gravity environment.However, if bubbles are initially trapped in the molten material, they cannot escape from the material under the micro-gravity condition and could adversely affect the product quality.In the present study, an ultrasonic acoustic standing wave field is adopted to control the bubble motion under the micro-gravity environment.At first, a single ultrasonic transmitter was used to establish the acoustic standing wave field in a fluid with afree surface.It was experimentally confirmed under normal gravity that the bubble can be held stationary in the ultrasonic wave field.The experimental results were also confirmed by numerically solving the Rayleigh-Plesset equation and bubble motion equation in the translational direction.Next, the bubble control experiment was conducted by using dual ultrasonic vibrators.The ultrasonic acoustic standing wave field was moved by shifting the phase difference between the dual ultrasonic transmitters.It was experimentally confirmed that the bubble position can be controlled by moving the ultrasonic acoustic standing wave field.Finally, the bubble control technique by ultrasonic waves developed in ground experiments was verified for the reduced-gravity condition by conducting experiments aboard the KC-135 aircraft at NASA Johnson Space Center in the United States.It was experimentally confirmed that the present technique is applicable even under the reduced-gravity condition.It was also found that a larger bubble than that under normal gravity and a group of bubbles can be controlled under reduced-gravity by the present ultrasonic wave technique.
Underground water/gas transporting pipelines or cable-defective pipelines are important facilities of modern cities.Installation of such underground pipeline systems may be carried out by using underground digging machines with some trenchless techniques that can meet the requirements of minimum impact on the environment.In this paper, an underground digging method is introduced and discussed for transportation characteristics of dug soil.A distinct feature of the air transportation is that a special device is used for controlling the dug soil when it is sucked into a transportation pipeline by a vacuum pump.This transportation method is tested with sand, and the air-sand two-phase flow is measured by using visualization and pressure measurement.Visual observation with a video camera shows that air-sand plug flow is a flow pattern in the present transportation conditions.The pressure drop is discussed based on the visualization measurement.
Gas-liquid-solid three-phase bubbly flow in a vertical pipe is observed.Air, tap water and aluminum-ceramic balls of mean diameters 4.16 and 24.8mm were flowed in two vertical pipes with similar size of 30.3 and 30.8mm inside diameters and about 7.5m in height.The motions of small bubbles, small particles and large particles of two-phase flow and three-phase flow were recorded by a 8mm CCD video camera and a high speed video camera.Their motions were explained and qualitatively compared with each others.It become clear that the rising velocity of cluster composed of small bubbles differs from that of cluster of small particles in gas-liquid-solid three-phase bubbly flow with small particles, and the rising velocity of large particle in gas-liquid-solid three-phase bubbly flow with large particles is larger than that of in liquid-solid two-phase flow with large particles.The former phenomenon is explained by the difference of their buoyancy in liquid phase.The latter phenomenon shows that there is strong interaction between large particle and small bubbles through the liquid when they flow through the thin clearance between large particle and pipe wall.
Gas-liquid-solid three-phase slug flow in a vertical pipe is observed. The motions of small bubbles, small particles, large bubbles and large particles were explained qualitatively by comparing their spatial distributions and velocities with each of other flows.It become clear in the case of three-phase slug flow that the rising velocity of cluster composed of small bubbles or small particles in liquid slug is larger than it in three-phase bubbly flow.When large particle collides with large bubble, it enters into it and falls there, then large bubble is destroyed by large particle.When large particle leaves large bubble and enters into liquid slug, first it is accelerated at a big acceleration then rises with approximately constant velocity. But this rising velocity in three-phase slug flow is smaller than it in liquid-solid two-phase flow or gas-liquid-solid three-phase bubbly flow.Also small particle falls in the liquid film around large bubble with a declining acceleration to be bigger than large particle.In gas-liquid-solid three-phase slug flow with small particles, the velocity of large bubble is faster than it in gas-liquid two-phase slug flow, but when becoming gas-liquid-solid three-phase slug flow with large particles, the large bubbles show a situation contrary to the above.