- 著者
- Yukihiko Satou Keisuke Sueki Kimikazu Sasa Hideki Yoshikawa Shigeo Nakama Haruka Minowa Yoshinari Abe Izumi Nakai Takahiro Ono Kouji Adachi Yasuhito Igarashi
- 出版者
- GEOCHEMICAL SOCIETY OF JAPAN
- 雑誌
- GEOCHEMICAL JOURNAL (ISSN:00167002)
- 巻号頁・発行日
- vol.52, no.2, pp.137-143, 2018-03-30 (Released:2018-04-19)
- 参考文献数
- 14
- 被引用文献数
- 36 77
Two types of radioactive particles were isolated from environmental samples collected at various distances from the Fukushima Dai-ichi Nuclear Power Station. “Type A” particles are 2–10 μm in diameter and display characteristic Cs X-ray emissions when analyzed using energy-dispersive X-ray spectrometry (EDS). “Type B” particles are considerably larger, up to 400 μm in diameter, with Cs concentrations too low to be detectable with EDS. These larger particles were isolated from the region north of the nuclear reactor site, which was contaminated on March 12, 2011. The specific activity of Type B particles is much lower than Type A, and the mean 134Cs/137Cs ratios are ~0.93 and 1.04, respectively. The Type B ratio indicates that power station Unit 1 is the source, implying that these larger radioactive particles were discharged on March 12. This study found that different type of radioactive particles were released not only on March 15 but also on March 12.
- 著者
- Sebastian Oscar Danielache Chisato Yoshikawa Mizuo Kajino Satoshi Itou Wataru Kakeya Naohiro Yoshida Yasuhito Igarashi
- 出版者
- GEOCHEMICAL SOCIETY OF JAPAN
- 雑誌
- GEOCHEMICAL JOURNAL (ISSN:00167002)
- 巻号頁・発行日
- vol.53, no.2, pp.103-118, 2019 (Released:2019-04-05)
- 参考文献数
- 24
- 被引用文献数
- 1
We present a numerical study conducted using a regional Lagrangian model to account for the transport, deposition and radioactive decay of 35S in sulfur dioxide and sulfate aerosols emitted into the atmosphere during the Fukushima Dai-ichi Nuclear Power Plant incident. The model is a Eulerian-Lagrangian hybrid system that accounts for chemical conversion of SO2 into SO42− in a Eulerian manner. The simulations were compared to field measurements of atmospheric 35S in sulfate collected at Kawamata, Tsukuba, Kashiwa, Fuchu and Yokohama, Japan. The 35S emission scenario that best replicated the field measurements followed the same temporal variation pattern as the 134/137Cs emissions. These results suggest that 35S and 134/137Cs follow a similar release pattern. Among the considered emission scenarios, a maximum flux of emitted chemical compounds was assumed to be either 100% 35SO42− or 100% 35SO2, with values of 4.0 × 1019 molecules/hour and 4.0 × 1020 molecules/hour, respectively on March 14th. These emission scenarios reflect the findings reported in the literature, where traces of 35SO2 were measured along with 35SO42−, so the actual emission is expected to be a combination of both chemical forms. The Kawamata measurements (Figs. 5 and 6) presented a large concentration in the July–August period, several months after emissions decreased by more than an order of magnitude. To explain this anomaly, re-suspension ratios were calculated for the Kawamata site, which ranged between 0.1 and 1.5% and partially, but not fully, explain the large measured concentrations. Furthermore, they show large discrepancies with 134/137Cs re-suspension values for measurements at the town of Namie. This situation indicates a lack of understanding of the transformations of 35S that occurs after deposition and the mechanisms involved in the 35S re-suspension process.