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A 40-year-long record of the sulfur dioxide (SO 2) emission rate of Asama volcano, Japan, is presented including high-temporal-resolution data since the 2004 eruption. The 2004 and 2008–2009 eruptive activities were associated with high SO 2 emission, and SO 2 emission rates markedly fluctuated. In contrast, stable and weak SO 2 emissions have been observed for the rest of the investigated interval. The fluctuation of the SO 2 emission rates is correlated with the number of shallow low-frequency B-type earthquakes, implying that increased flows of gas and/or magma induced the B-type earthquakes along the shallow conduit. The total volumes of outgassed magma during the 2004 and 2008–2009 eruptive activities are estimated to be 1.9 × 10 8 and 1.5 × 10 8 m 3, respectively. These volumes are about 100–200 times larger than those of the erupted magma, indicating that the large volumes of the magma were outgassed without being erupted (i.e., excess degassing/outgassing). Degassing and outgassing driven by magma convection rather than by permeable gas flow in the conduit is concluded as the probable degassing/outgassing process of Asama volcano based on model examinations, and is thought to occur regardless of the outgassing intensity. Production rates of outgassed magma related to the 2004 and 2008–2009 eruptive periods are estimated to have been 7.4 × 10 3 and 6.7 × 10 3 kg/s, respectively. These values are one order of magnitude higher than the average production rate of 0.92 × 10 3 kg/s for the inactive periods. Increased supply of fresh magma is thought to activate magma convection in the conduit and to thereby increase magma degassing/outgassing. [ABSTRACT FROM AUTHOR]

Abstract: The current material design of the International fusion materials irradiation facility (IFMIF) back-plate in Japan consists of an austenitic stainless steel type-316L and a RAF/M steel type-F82H. The 316L and F82H are welded together. The 316L region of the back-plate is also welded to the target assembly made of 316L. The back-plate operates under a severe neutron irradiation condition (50dpa/year). Therefore, it is important to perform metallurgical and mechanical tests for these welds in engineering design of the IFMIF. The F82H/316L weld joint with a filler metal type-Y309 was fabricated using TIG-welding method, followed by PWHT at 1013K for 1h. The 316L/316L weld joint was fabricated using YAG-laser welding method. The F82H/316L TIG-weld was found to be satisfactory. However, although the 316L/316L YAG-weld showed no harmful defect, the hardness was somewhat lower in the weld metal. Rupture occurred in the weld metal, and strength and elongation decreased somewhat. Furthermore, small dimples with several large voids were also visible in the fracture surface. [Copyright &y& Elsevier]

An extremely large amount of volcanic gas has been released since mid-August 2000 from the volcanic island of Miyakejima, Japan, after formation of a summit caldera of 1.6 km diameter. The volcanic gas emission was continuous with very little extrusive magma activity. Variation of the SO2 emission rate was monitored by repeated measurements with an airborne correlation spectrometer. In December 2000, the SO2 emission rate averaged for the month peaked at 54 kt/d, which is twice the global SO2 emission rate from nonerupting volcanoes evaluated before this activity. The SO2 emission rate gradually decreased, almost linearly when plotted on a log scale, to 7 kt/d by the end of 2002, and then remained constant until at least December 2003. The total SO2 emission amounts to 18 Mt, comparable to the emission of a large explosive eruption such as Pinatubo in 1991. A theoretical evaluation, based on the model of magma convection in a conduit, suggests that extremely large volcanic gas emissions can be caused by formation of a magma pathway with a slightly larger diameter than exists in common systems, because the magma-transport rate is proportional to the fourth power of the conduit radius. Because volcanic gas emissions were initiated by formation of a summit collapse caldera of 1.6 km diameter, the creation of a large magma-conduit system through fractures formed during caldera collapse is likely the underlying cause of the extremely large volcanic gas emissions from the volcano. [ABSTRACT FROM AUTHOR]