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Sueoka, Shigeru; Ikuho, Zuitetsu*; Hasebe, Noriko*; Tagami, Takahiro*
no journal, ,
no abstracts in English
Murakami, Hiroaki; Iwatsuki, Teruki
no journal, ,
no abstracts in English
Otosaka, Shigeyoshi; Fukuda, Miho*; Aono, Tatsuo*
no journal, ,
Behavior of dissolved radiocesium near the seafloor is discussed from the distributions of 
Cs in seawater, seabed sediment and pore water collected from the area around Fukushima. The Cs concentrations in the pore water, collected from 2015 to 2017, ranged between 33 and 1186 mBq/L, and were 10
40 times higher than those in seawater on the sediment surface. The Cs concentration in the overlying water did not show clear differences regardless of the pore size of the filter used for filtration. From these results, it was confirmed that radiocesium in the seabed sediment was dissolved in pore water and diffused to the benthic layer. The apparent distribution coefficient between pore water and sediment was [0.94.2]
10
L/kg, with no difference depending on the year of sampling. These results indicated that an equilibrium of Cs between pore water and sediment has established during the observation period.
Watanabe, Tsuyoshi; Asamori, Koichi
no journal, ,
no abstracts in English
Ueki, Tadamasa; Niwa, Masakazu; Yonaga, Yusuke; Iwano, Hideki*; Danhara, Toru*
no journal, ,
no abstracts in English
Watanabe, Tsuyoshi; Asamori, Koichi; Okuyama, Satoshi*; Saiga, Atsushi; Umeda, Koji*
no journal, ,
no abstracts in English
Watanabe, Tsuyoshi; Saiga, Atsushi; Asamori, Koichi; Shimada, Akiomi; Umeda, Koji*
no journal, ,
no abstracts in English
Ishii, Eiichi
no journal, ,
Assessing the hydraulic connectivity of fractures by single-borehole investigations is crucial to radioactive waste disposal, but is still a challenge as such connectivity is difficult to measure directly. This study presents geological, hydrological, hydrochemical, and rock mechanical data for three faulted/fractured mudstones (the Koetoi, Wakkanai, and Palfris formations) and proposes a new methodology for assessing the hydraulic connectivity of fractures.
Sato, Tatsuhiko; Kataoka, Ryuho*; Shiota, Daiko*; Kubo, Yuki*; Ishii, Mamoru*; Yasuda, Hiroshi*; Miyake, Shoko*; Tsujino, Takashi*
no journal, ,
A ground level enhancement (GLE) event occurred on 10-11 September 2017, associated with X8.2 solar flare exploded at western limb. The magnitude of the GLE was not so large even at the peak, but the duration of the event was longer than average. We briefly report the results of our manually conducted nowcast using WASAVIES (Warning System of AViation Exposure to Solar energetic particles). The maximum radiation dose rate at 12 km flight altitude was estimated to be approximately 2 
Sv/h, which is only one-third of the corresponding background dose rate due to the galactic cosmic-ray exposure. This result verified the safety of aircrews and passengers in aviation during this event. The automatic calculation system of WASAVIES was developed, and it will be released via website of Regional Warning Center Japan, International Space Environment Services (RWC Japan, ISES) at NICT in near future.
Watanabe, Yusuke; Hayashida, Kazuki; Murakami, Hiroaki; Iwatsuki, Teruki
no journal, ,
In assessing the safety of geological disposal of high-level radioactive waste, groundwater chemistry is an important factor influencing the performance of engineered materials and the behavior of radionuclides. It is essential to understand the hydrochemical changing process and stable condition after the closure of the disposal facilities. In this study, a simulated experimental drift was constructed in granite at a depth of 500 m at the Mizunami Underground Research Laboratory, and the hydrochemical condition and related processes after drift closure were observed.
Komatsu, Tetsuya; Izumida, Atsuto*; Takahashi, Takayuki*; Funatsu, Taro*; Muraki, Masahiro*; Hozo, Renya*; Nomura, Katsuhiro; Niwa, Masakazu; Sugai, Toshihiko*
no journal, ,
no abstracts in English
Kijima, Yuichi; Yamamoto, Yoichi
no journal, ,
JAEA as Japanese NDC-2 is in charge of monitoring radionuclide related to CTBT and performs analysis of radionuclide data and Atmospheric Transport Modelling (ATM) simulation to investigate the diffusion of radioactive plume. About two months later after the third nuclear test in DPRK on 12 February 2013 (DPRK-3), xenon-133 and xenon-131m were detected simultaneously far beyond normal background level of the activity concentration at the CTBT Takasaki station in Japan. From the aspect of isotope ratio and the result of ATM simulation, it is highly possible that these radioxenon isotopes are originated from DPRK-3. And there were detections of balium-140 and lanthanum-140 at the CTBT Okinawa station in Japan in 2010, and rutenium-106 in several CTBT stations in Eurasia in 2017. We report on these detections of artificial radionuclides in CTBT radionuclide stations.
Kurikami, Hiroshi; Sakuma, Kazuyuki
no journal, ,
It is thought that radiocesium exported from forests is the main source of the radiocesium taken up by freshwater fish, so it is important to clarify the export mechanism to predict future trends. In this study we developed a compartment model to assess catchment-scale migration of radiocesium and evaluated three potential transport pathways from forests to freshwater fish: direct litter fall into rivers, lateral inflow from litter layers in forests, and lateral inflow from underlying forest soils. The results suggest that a combination of direct litter fall and lateral inflow from the litter layer are the main export mechanisms influencing the radiocesium concentration of freshwater fish.
Yamamoto, Yoichi; Kijima, Yuichi; Tomita, Yutaka
no journal, ,
This presentation summarizes JAEA's recent activities related to CTBT verification regime. To establish the global verification regime of CTBT for the nuclear tests, JAEA has been operating provisionally three facilities (two monitoring stations and one radionuclide laboratory) of the CTBT international monitoring system and a national data center for radionuclide monitoring. For the 6th nuclear test conducted by North Korea in September 2017, JAEA reported the analysis and evaluation results of data observed at the CTBT radionuclide monitoring stations to the national government etc. in a timely manner and thereby contributed to the evaluation by the national government based on the CTBT operation system in Japan. For the purpose of strengthening CTBTO's detection capability for nuclear tests, JAEA started new noble gas joint measurement project with CTBTO in Horonobe (Hokkaido) and Mutsu (Aomori) based on the Japanese government contribution in 2017.
Niizato, Tadafumi; Sasaki, Yoshito; Watanabe, Takayoshi; Mitachi, Katsuaki*; Ito, Satomi; Kuramoto, Takayuki*; Arai, Hirotsugu*; Nomura, Naoki*; Hayashi, Seiji*; Tamaoki, Masanori*
no journal, ,
Cs released from the TEPCO's Fukushima Dai-ichi Nuclear Power Plant accident has a long half-life of about 30 years, it is necessary to monitor the distribution and its radioecological impact over the long term. Mountainous forests, which accounts for about 70% of Fukushima prefecture, tend to be a sink of radiocesium contamination rather than a source for the contamination of other ecosystems. An understanding of the environmental dynamics of radiocesium in the forest floor of various conditions is important issue, while progressing to the resident return. In this paper, we report on the results of the field investigation into the Cs distribution and the Cs outflow in the mountainous forest of Fukushima, where the wildfire broke out in the spring of 2017.
King, G.*; Sueoka, Shigeru; Tsukamoto, Sumiko*; Herman, F.*; Ahadi, F.*; Gautheron, C.*; Delpech, G.*; Tagami, Takahiro*
no journal, ,
no abstracts in English
King, G.*; Sueoka, Shigeru; Tsukamoto, Sumiko*; Herman, F.*; Ahadi, F.*; Gautheron, C.*; Delpech, G.*; Tagami, Takahiro*
no journal, ,
no abstracts in English
Shishikura, Ai*; Sueoka, Shigeru; Tagami, Takahiro*
no journal, ,
no abstracts in English
Sakuma, Kazuyuki; Malins, A.; Kurikami, Hiroshi; Kitamura, Akihiro
no journal, ,
Various simulation studies have been undertaken into dissolved and particulate Cs concentrations in rivers affected by Chernobyl and Fukushima accident fallout. Here we applied the General-purpose Terrestrial fluid-Flow Simulator (GETFLOWS) watershed code to calculate water, sediment, and particulate and dissolved Cs discharge from the upstream of Ota River catchment in Fukushima Prefecture. It was possible for the simulations to reproduce the mean dissolved Cs concentrations in river water between 2014 and 2015 under base flow conditions. However neither the seasonal variability of the Cs concentrations in base flow periods, nor the peaks in concentration that occurred during storms, could be reproduced in the simulations. We are now extending GETFLOWS with a forest compartment model such that forest canopies, internal transport inside trees, fresh litter fall, and litter decomposition can be simulated, in order to assess the effect of these processes on Cs concentrations in river water.
Tagami, Takahiro*; Sueoka, Shigeru
no journal, ,
no abstracts in English