The biological effects of radiation are of two types: stochastic (such as radiation‐induced cancer) and deterministic (such as erythema).The effective dose is used to assess the risk of stochastic effects, and the dose equivalent is used to assess the risk of deterministic effects. However, the effective dose and dose equivalent, body‐related protection quantities, are not measurable. Therefore, operational quantities (1‐cm dose equivalent and 70‐μm dose equivalent) are used to assess the effective dose and dose equivalent. Generally, the 1‐cm dose equivalent, determined using a monitoring badge, is used to assess effective dose, whereas the 70‐cm dose equivalent, determined using a monitoring badge, is used to assess dose equivalent. Furthermore, when using two monitoring badges, the 1‐cm dose equivalent of each badge is converted into the effective dose using calculation algorithms.
On March 11 in 2011, a very big earthquake occurred in Tohoku district in Japan. Huge tsunami was generated by this earthquake and the coastal area of Tohoku district had catastrophic damage. Many houses were destroyed by tsunami and huge amount of rubble was generated. At the same time, a large amount of tsunami sludge deposited on land. We carried out the actual construction to create the artificial ground by recycling tsunami sludge. The physical properties of tsunami sludge were different if the places were different. However, it was confirmed through the actual construction that creation of artificial ground was possible even if the properties of tsunami sludge were different.
A strong earthquake hit eastern Japan on March 11th, 2011 and it lasted for 6 minutes. It triggered huge tsunami and the tsunami damaged not only houses and residents but also farmlands. There are several types of interactions between the tsunami and the farmlands. If there was a muddy (sometimes contains sulfidic materials) and/or sandy deposit under the shallow seawater or in the nearshore zone, it was transported inland. Pyrite was found in the sulfur-rich muddy deposits. There are narrowly eroded places along a road and a ridge where tsunami fell down from these micro-high sites. Moreover, the plow layer soil was lost at least partly. Thus, the deposits on the farmlands are the mixtures of the eroded plow layer soil and transported materials from the nearshore zone. The chemical interactions include the exchange reaction between Na+ in seawater and exchangeable cations in the plow layer soil, and precipitation of gypsum (CaSO4.2H2O) as well as halite (NaCl) when the soils dry. Debris of various materials and halite, at least, must be removed to restore the damaged farmlands.
The program of research and development on the reconstruction support from the Great East Japan Earthquake on the base of the collaboration of college of technology was conducted using micro bubble technology for the water purification and the recovery of oyster culture in Ofunato Bay. The compact, lightweight and energy-saving devices having instrumentation system of 104 micro bubble generators were developed to carry out the purification and the culture. The micro bubbles in Takonoura water area of Ofunato Bay were supplied continuously during 8 months. Oyster growth-promoting was achieved by the supply of micro bubbles in Ofunato Bay and a new cultivation method of the oyster using micro bubble technology was found by the growth.
On the occasion of one year after the huge earthquake disaster in the eastern part of Japan, the symposium on recovery from the earthquake disaster toward environmental resuscitation was held in Sendai city on 15th May, 2012, which was organized by the Japanese Society for Multiphase Flow (JSMF). In the symposium, the five interesting and profitable invited talks were presented, focusing on the environmental recovery from both the far-reaching radioactive contaminations due to the severe accident of the Fukushima Daiichi nuclear power plants and the tsunami disasters in the seaside. This summary describes the planning and the status of the symposium, the opening address from the president of the JSMF, and the outlines of the five presentations.
In the cleaning processes of manufacturing semiconductor devices, two-fluid spray cleaning technique is widely used: however, the detailed cleaning mechanism has not been clarified yet. In this study, we focus our attention to the elementary process of this cleaning technique, i.e. a single droplet impact on a solid surface. We experimentally observe impact of single droplet on a rigid solid surface with the use of high-speed photography, and we discuss the deformation of the droplet. Especially we focus on the effects of surfaces tension, surface roughness and surrounding pressure. Water droplets always create lamella during spreading after the impact on a smooth surface in the atmospheric pressure condition. Either decrease of the surface tension or increase of the surface roughness causes droplet splash. However, decrease of the surrounding gas pressure makes droplets always create lamella even in the cases with low surface tension and rough surfaces.
We have been developing a novel surface cleaning technique using steam and water mixed spray. Our technique shows great efficiency in removing thin surface film such as photo-resist film. However, the film-removal mechanism has not been clarified yet. One possible film-removal mechanism is the local heat expansion due to the difference of coefficients of linear expansion between film and substrate. In this study, we studied the removal characteristics of deposited aluminum film on a glass surface by spraying steam-water or air-water mixed spray. The surface temperature changes caused by the spray were carefully measured. We found that the steam and water mixed spray that increases the surface temperature can remove the film while the air and water mixed spray cannot. These results indicate that the difference of coefficients of linear expansion between film and substrate may not be the dominant factor in the film removal by the steam and water mixed spray.
Critical heat flux is an important design factor of boiling two-phase flow equipments, such as boiler, steam generator, so on. In actual boiling system, the water tubes were suffered from a non-uniform heat flux and a tube inclination. In this series investigation, in order to understand the CHF phenomena in inclined upward flow systematically, CHF experiment was conducted by using tube of 900, 1800 mm in heating length with several tube inclinations and 450 mm in heating length with vertical upward flow. On the basis of evaluation of CHF in vertical upward flow by using the film flow model, the entrainment was drastically increased with a decrease of heating length, because the entrainment due to boiling can not be neglected under high heat flux condition. The objective of this investigation is to systematically understand the influence of the tube inclination on CHF characteristics under such high heat flux condition. In this study, the CHF experiment was conducted by using a circumferentially non-uniform heated tube with the forced convective boiling system. The test section had 20 mm in inner diameter, 24 mm in outer diameter and 450 mm in heating length. In the non-uniform heated tube, the center of inner diameter was shifted by 1.5 mm from the center of outer diameter. The circumferentially non-uniform heat flux distribution was generated by the difference of the circumferential electrical resistance. The test section tube was set at arbitrary inclination angles. The obtained CHF was strongly influenced by the circumferential location of local maximum heat flux point and tube inclination. These CHF characteristics could be categorized by using the CHF ratio against the value of the vertical upward flow and the modified Froude number which took account of the influence of disturbance wave.