Kimikazu Sasa

Learn More
A tremendous amount of radioactivity was discharged because of the damage to cooling systems of nuclear reactors in the Fukushima No. 1 nuclear power plant in March 2011. Fukushima and its adjacent prefectures were contaminated with fission products from the accident. Here, we show a geographical distribution of radioactive iodine, tellurium, and cesium in(More)
Dependence of nitrogen content on (a) partial pressure of nitrogen PN2 (substrate temperature TS = 800 ºC, deposition rate r ~ 0.04 h/nm), (b) r (PN2 = 10 −5 Torr, TS = 800 ºC), and (c) TS (PN2 = 10 −5 Torr, r ~ 0.04 h/nm). In this report, we expressed the chemical composition of the films as SrTaO3−xNx despite the possible deviation of the total anion(More)
To clarify the effect of vegetation and surface soil removal on dissolved inorganic nitrogen (N) dynamics in a snow-dominated forest soil in northern Japan, the seasonal fluctuation of N concentrations in soil solution and the annual flux of N in soil were investigated at a treated site (in which surface soil, including understory vegetation and organic and(More)
We propose a methodology for estimating the residence time of groundwater based on bomb-produced (36)Cl. Water samples were collected from 28 springs and 2 flowing wells located around Mt. Fuji, Central Japan. (36)Cl/Cl ratios in the water samples, determined by accelerator mass spectrometry (AMS), were between 43 × 10(-15) and 412 × 10(-15). A reference(More)
A first international (36)Cl interlaboratory comparison has been initiated. Evaluation of the final results of the eight participating accelerator mass spectrometry (AMS) laboratories on three synthetic AgCl samples with (36)Cl/Cl ratios at the 10(-11), 10(-12), and 10(-13) level shows no difference in the sense of simple statistical significance. However,(More)
In the process of developing a new dosimetry system for atomic bomb survivors in Hiroshima and Nagasaki (DS02), an intercomparison study between (152)Eu and (36)Cl measurements was proposed, to reconcile the discrepancy previously observed in the Hiroshima data between measurements and calculations of thermal neutron activation products. Nine granite(More)
Essential parameters for the applications of (36)Cl as a tracer in groundwater studies include the initial (36)Cl/Cl ratio, at the time of recharge, and/or the natural background deposition flux of (36)Cl in the recharge area. To facilitate the hydrological use of (36)Cl in central Japan, this study aimed to obtain a precise estimate of the long-term(More)
Nitrogen (N) emissions in Asian countries are predicted to increase over the next several decades. An understanding of the mechanisms that control temporal and spatial fluctuation of N export to forest streams is important not only to quantify critical loads of N, N saturation status, and soil acidification N dynamics and budgets in Japanese forested(More)
To evaluate the deposition density and extent of subsurface infiltration of (129)I and (137)Cs in the restricted area that was highly contaminated by the accident of Fukushima Dai-ichi Nuclear Power Plant, cumulative inventories of (129)I and (137)Cs, concentrations of (129)I and (137)Cs, and (129)I/(137)Cs ratio in 30-cm-long soil columns were compared(More)
In an effort to develop DS02, a new radiation dosimetry system for the atomic bomb survivors of Hiroshima and Nagasaki, measurements of neutron-induced activities have provided valuable information to reconstruct the radiation situation at the time of the bombings. In Hiroshima, the depth profile of (152)Eu activity measured in a granite pillar of the(More)