Analysis of two forms of radioactive particles emitted during the early stages of the Fukushima Dai-ichi Nuclear Power Station accident

Satou, Yukihiko; Sueki, Keisuke; Sasa, Kimikazu; Yoshikawa, Hiroyuki; Nakama, Shigeo; Minowa, Haruka; Abe, Yoshinari; Nakai, Izumi; Ono, Takahiro; Adachi, Kouji; Igarashi, Yasuhito

doi:10.2343/geochemj.2.0514

Cited by 86 publications

(110 citation statements)

References 12 publications

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“…Throughout the paper, we only focus on 137 Cs because the atmospheric behavior and radioactivity of 134 Cs should be almost the same as those of 137 Cs for the current analysis. Certainly, the slight difference in the activities of 134 Cs and 137 Cs was essentially important for the analysis of their origins, as conducted by Satou et al (2018). Thus, the simulation results of all radio-Cs can be obtained by doubling the results of 137 Cs.…”

Section: Comparison Of Precipitation Fieldsmentioning

confidence: 99%

Deposition and Dispersion of Radio‐Cesium Released Due to the Fukushima Nuclear Accident: Sensitivity to Meteorological Models and Physical Modules

et al. 2019

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To assess the uncertainty of meteorological simulations in the transport and deposition of radio‐Cs release associated with the Fukushima Daiichi Nuclear Power Station accident in Japan, a multiple meteorological model and module ensemble analysis with a single chemical transport model (CTM) was conducted. Although several multimodel ensemble studies have previously been performed, the current type (i.e., one CTM with several meteorological fields) was applied for the first time and represents a useful way to evaluate the uncertainty of each component of CTM. The current analysis concluded that the underestimation of the deposition efficiency of CTM was the reason for the underestimation of simulated radio‐Cs deposition, whereas the simulated dispersion and precipitation and estimated source term were all reasonable: all of the simulations underestimated the deposition amount, whereas some underestimated but others overestimated the simulated precipitation and radio‐Cs concentrations. The CTM simulation performed using the meteorological ensemble mean field was successful in reducing variance, and they gave reasonable results. The simulated deposition using the meteorological ensemble was better than others because the ensemble mean enlarged the light precipitation areas and because the land contamination was mainly caused by light precipitation. The current ensemble study indicated that in‐cloud scavenging was the most dominant mechanism of radio‐Cs deposition, followed by dry deposition and fog deposition over the entire land area. In some deposition regions, fog deposition was dominant, exceeding 80%, depending on the simulations. The simulated concentrations and depositions varied by more than twofold, depending on the selection of the meteorological field.

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Section: Comparison Of Precipitation Fieldsmentioning

confidence: 99%

Deposition and Dispersion of Radio‐Cesium Released Due to the Fukushima Nuclear Accident: Sensitivity to Meteorological Models and Physical Modules

et al. 2019

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“…These particles were estimated to be released from unit 1 based on the comparison with the 134 Cs/ 137 Cs activity ratio of the nuclear fuel at the time of the accident (the ratios of units 1, 2 and 3 were approximately 0.94, 1.08, and 1.05, respectively) calculated with the ORIGEN2 code by Nishihara et al 23 . Satou et al 24 classified these two types of CsMPs into Type-A and Type-B. This classification is mostly due to difference in the emission sources based on the 134 Cs/ 137 Cs activity ratio (Type-A: unit 2 or 3; Type-B: unit 1).…”

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Isotopic ratios of uranium and caesium in spherical radioactive caesium-bearing microparticles derived from the Fukushima Dai-ichi Nuclear Power Plant

Kurihara

Takahata

Yokoyama

et al. 2020

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Spherical radioactive caesium (cs)-bearing microparticles (csMps) were emitted during the fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March, 2011. The emission source (timing) and formation process of these particles remain unclear. In this study, the isotopic ratios of uranium (235 U and 238 U) and caesium (133 Cs, 134 Cs, 135 Cs, and 137 Cs) isotopes in the five spherical CsMPs (ca. 2 μm in size) sampled at 50 km west of the FDNPP were determined using secondary ion mass spectrometry and laser ablation-ICPMS, respectively. Results showed that the 235 U/ 238 U ratios of csMps were homogeneous (1.93 ± 0.03, N = 4) and close to those estimated for the fuel cores in units 2 and 3, and that the Cs isotopic ratios of CsMP were identical to those of units 2 and 3. These results indicated that U and Cs in the spherical CsMPs originated exclusively from the fuel melt in the reactors. Based on a thorough review of literatures related to the detailed atmospheric releases of radionuclides, the flow of plumes from the fDnpp reactor units during the accident and the U and cs isotopic ratio results in this study, we hereby suggest that the spherical CsMPs originate only from the fuel in unit 2 on the night of 14 March to the morning of 15 March. The variation range of the analysed 235 U/ 238 U isotopic ratios for the four spherical particles was extremely narrow. Thus, U may have been homogenised in the source through the formation of fuel melt, which ultimately evaporating and taken into CsMPs in the reactor and was released from the unit 2. On 11 March 2011, the Great East Japan Earthquake triggered the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Radioactive materials were released to the atmosphere and have caused various environmental problems 1-4. Among the six nuclear reactors in the FDNPP, the reactors of units 1-3 were in operation at the time of the earthquake 5. In the accident, hydrogen explosions occurred in the nuclear reactor buildings of units 1, 3 and 4 (at 15:36 JST on 12 March, 11:01 JST on 14 March and 6:14 JST on 15 March, respectively), but the explosion in unit 4 occurred in the reverse flow of hydrogen generated in unit 3 6. Unit 4 had been shut down from 2010, and all of the fuel were kept in the spent fuel pool (SFP), suggesting that no radionuclide was emitted from unit 4, whereas units 1 and 3 can be the sources of the radionuclides. Meanwhile, the release of radionuclides from reactor pressure vessel (RPV) or blowout panel in unit 2 was also an important source of the radionuclides 7 .

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“…Some recent research proposed that CsMPs can be distinguished from radiocesium-sorbing minerals by the intensity of radioactivity per individual particle. 13,14 The radioactivity of CsMPs is approximately proportional to their volume, 15 and as an example, the minimum CsMP reported to date had a diameter of 1.3¯m and 137 Cs radioactivity of 0.43 Bq. 14 In contrast, WB and other mineral grains of several dozen microns possess radioactivity on the order of 10 ¹2 Bq, at most.…”

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confidence: 99%

“…1¯m, based on their specific radioactivity (radioactivity per volume). 15 For these reasons, it is expected that CsMPs with higher radioactivity have been preferentially reported to date. In this study, we attempted to find CsMPs with smaller size and lower radioactivity than those previously reported, as well as radiocesium-sorbing mineral grains with higher radioactivity than has ever been searched for.…”

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Finding Radiocesium-bearing Microparticles More Minute than Previously Reported, Emitted by the Fukushima Nuclear Accident

2019

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Radiocesium-bearing microparticles (CsMPs) with a diameter and 137 Cs radioactivity less than 0.5¯m and 0.05 Bq, respectively, released by the Fukushima nuclear accident were identified on the ground. These values are considerably lower than those expected for CsMPs in previous studies. Radiocesium-sorbing mineral grains with radioactivity >0.1 Bq were also found in the soil near the nuclear plant. Therefore, it is not reliable to only use the intensity of radioactivity as the criterion for distinguishing CsMPs from radiocesium-sorbing minerals.

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Analysis of two forms of radioactive particles emitted during the early stages of the Fukushima Dai-ichi Nuclear Power Station accident

Cited by 86 publications

References 12 publications

Deposition and Dispersion of Radio‐Cesium Released Due to the Fukushima Nuclear Accident: Sensitivity to Meteorological Models and Physical Modules

Deposition and Dispersion of Radio‐Cesium Released Due to the Fukushima Nuclear Accident: Sensitivity to Meteorological Models and Physical Modules

Isotopic ratios of uranium and caesium in spherical radioactive caesium-bearing microparticles derived from the Fukushima Dai-ichi Nuclear Power Plant

Finding Radiocesium-bearing Microparticles More Minute than Previously Reported, Emitted by the Fukushima Nuclear Accident

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