Kimikazu Sasa

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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)
The Fukushima Daiichi Nuclear Power Plant (F1NPP) accident in 2011 released radionuclides into the atmosphere in both aerosol and gaseous form. Subsequent studies of contamination in the environment have focused on the bulk radioactivity in samples. Comparatively little is known about the relative contribution and patterns of soluble versus particulate(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)
1 Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 Japan 2 Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 Japan 3 CREST, Japan Science and Technology Agency, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 Japan 4 Tandem Accelerator Complex, University of Tsukuba, 1-1-1(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 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)
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)
This study investigates the potential of Cl in tracing young groundwater with residence times of up to ~50 years. Groundwater samples were obtained from 16 irrigation wells in paddy fields located within an upland–lowland system in the Yoro River basin, Central Japan. The Cl/Cl ratios were in the range of 17 to 362  10. Among the samples with higher Cl(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)