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Analysis of radioactive cesium-enriched particles and measurement of their distribution in marine sediment near Fukushima Daiichi nuclear power plant

Analysis of radioactive cesium-enriched particles and measurement of their distribution in marine sediment near Fukushima Daiichi nuclear power plant
Analysis of radioactive cesium-enriched particles and measurement of their distribution in marine sediment near Fukushima Daiichi nuclear power plant
Cesium-enriched particles released from the Fukushima Daiich Nuclear Power Plant (NPP1) exist in the Fukushima coastal waters and offshore, and they possibly affect the wide-area distribution of the radioactive cesium measured by the towed spectrometer. Therefore, the distribution of them in marine sediment was measured near NPP1 in November, 2016. We scanned the seafloor using a remotely operated vehicle (ROV) equipped with a NaI(Tl) scintillation detector. The sediment samples were obtained on the survey line by the ROV’s suction-type sampler. Five cesium particles, with diameters of approximately 400 μm, were isolated from the samples. The radioactivity of 137Cs was less than 360 Bq, and no nuclides other than 134Cs, 137Cs, and natural radioactive ones were found from gamma-ray spectroscopy. In the particles, titanium and calcium were commonly detected by energy-dispersive X-ray spectrometry. We also estimated the particles’ presence from the change in the total counting rate of the scintillation detector. The average particle density is found to be 3.45×10−2 m −1 at most. The average increase in the counting rate directly above the cesium-enriched particles in the sediment was less than double. Therefore, the effect of such particles on the distribution of radioactive cesium is limited.
Fukushima, ROV, Sediment, Tohoku, cesium-enriched particle, radioactive cesium, underwater measurement
0022-3131
482-492
Ohnishi, Seiki
035c497a-ec02-4ce9-9879-a39a916b5d9a
Thornton, Blair
8293beb5-c083-47e3-b5f0-d9c3cee14be9
Koike, Toshikazu
3dccb070-231b-416d-8f8e-ff42e85a1c06
Odano, Naoteru
acead221-760b-421e-8c06-9907c2542f9e
Asami, Mitsufumi
6cc28349-80a3-4206-a0fd-09d7273eb94f
Kamada, So
2c260678-0588-4fba-a4b1-b7c1ea7a5f69
Nagano, Kazunori
da455901-ec39-4c26-bb85-b376c86d67de
Ura, Tamaki
b8fea5ba-e731-40fd-8544-1db1ca9f356b
Ohnishi, Seiki
035c497a-ec02-4ce9-9879-a39a916b5d9a
Thornton, Blair
8293beb5-c083-47e3-b5f0-d9c3cee14be9
Koike, Toshikazu
3dccb070-231b-416d-8f8e-ff42e85a1c06
Odano, Naoteru
acead221-760b-421e-8c06-9907c2542f9e
Asami, Mitsufumi
6cc28349-80a3-4206-a0fd-09d7273eb94f
Kamada, So
2c260678-0588-4fba-a4b1-b7c1ea7a5f69
Nagano, Kazunori
da455901-ec39-4c26-bb85-b376c86d67de
Ura, Tamaki
b8fea5ba-e731-40fd-8544-1db1ca9f356b

Ohnishi, Seiki, Thornton, Blair, Koike, Toshikazu, Odano, Naoteru, Asami, Mitsufumi, Kamada, So, Nagano, Kazunori and Ura, Tamaki (2021) Analysis of radioactive cesium-enriched particles and measurement of their distribution in marine sediment near Fukushima Daiichi nuclear power plant. Journal of Nuclear Science and Technology, 58 (4), 482-492. (doi:10.1080/00223131.2021.1879688).

Record type: Article

Abstract

Cesium-enriched particles released from the Fukushima Daiich Nuclear Power Plant (NPP1) exist in the Fukushima coastal waters and offshore, and they possibly affect the wide-area distribution of the radioactive cesium measured by the towed spectrometer. Therefore, the distribution of them in marine sediment was measured near NPP1 in November, 2016. We scanned the seafloor using a remotely operated vehicle (ROV) equipped with a NaI(Tl) scintillation detector. The sediment samples were obtained on the survey line by the ROV’s suction-type sampler. Five cesium particles, with diameters of approximately 400 μm, were isolated from the samples. The radioactivity of 137Cs was less than 360 Bq, and no nuclides other than 134Cs, 137Cs, and natural radioactive ones were found from gamma-ray spectroscopy. In the particles, titanium and calcium were commonly detected by energy-dispersive X-ray spectrometry. We also estimated the particles’ presence from the change in the total counting rate of the scintillation detector. The average particle density is found to be 3.45×10−2 m −1 at most. The average increase in the counting rate directly above the cesium-enriched particles in the sediment was less than double. Therefore, the effect of such particles on the distribution of radioactive cesium is limited.

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More information

Accepted/In Press date: 12 January 2021
e-pub ahead of print date: 8 February 2021
Keywords: Fukushima, ROV, Sediment, Tohoku, cesium-enriched particle, radioactive cesium, underwater measurement

Identifiers

Local EPrints ID: 447082
URI: http://eprints.soton.ac.uk/id/eprint/447082
ISSN: 0022-3131
PURE UUID: a4ccc7e9-c836-453f-954b-3f0d161b73ba

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Date deposited: 02 Mar 2021 17:33
Last modified: 25 Nov 2021 18:43

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Contributors

Author: Seiki Ohnishi
Author: Blair Thornton
Author: Toshikazu Koike
Author: Naoteru Odano
Author: Mitsufumi Asami
Author: So Kamada
Author: Kazunori Nagano
Author: Tamaki Ura

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